Note: Descriptions are shown in the official language in which they were submitted.
COMPOSITE STRINGER AND METHODS FOR
FORMING A COMPOSITE STRINGER
FIELD
[0001] The present disclosure generally relates to composite structures
and, more
specifically, to composite stringers and methods for forming composite
stringers.
BACKGROUND
[0002] Various structural components are used to form a typical
aircraft. For
.. example, a stringer is an elongate member that can be coupled to one or
more skin
panels to help carry and/or transfer a load from the skin panel to another
structure of
the aircraft (e.g., a frame, a rib, and/or a spar of the aircraft). In this
way, the stringer
can help to prevent buckling under compression or shear loads on the skin
panels,
and/or mitigate bending of the skin panels. For these and other reasons, the
aircraft
.. typically includes one or more stringers in a fuselage, wing assemblies,
and/or an
empennage of the aircraft.
[0003] Increasingly, aircraft are incorporating composite materials to
help make
the aircraft, among other things, lighter and more fuel-efficient. In
particular, for
example, the stringers and the skin panels may be made of composite materials.
A
.. stringer made from a composite material may be referred to as a "composite
stringer."
[0004] As an example, one type of composite material commonly used in
the
aerospace industry is carbon fiber reinforced plastic ("CFRP"). CFRP generally
includes one or more composite layers or plies laminated together to form a
sheet,
laminate or layup. Each of the composite layers or plies can include a
reinforcement
.. material and a matrix material. The matrix material surrounds, binds and
supports the
reinforcement material. The reinforcement material provides structural
strength to the
matrix material and the CFRP. The matrix material is generally a non-
conductive
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polymer such as an epoxy resin. The reinforcement material generally consists
of
strands of carbon fiber, which are electrically conductive.
[0005] As used herein, the term "composite structure" means a structure
that is
manufactured, fabricated or assembled, in whole or in part, from one or more
components made from CFRP (i.e., CFRP components) including, without
limitation,
aerospace structures, such as aircraft ribs, spars, panels, fuselages, wings,
wing
boxes, fuel tanks and tail assemblies. In order to manufacture, assemble, form
or
fabricate a composite structure, CFRP sheets, laminates or layups may be cut
or
trimmed to a desired shape or size after the composite layers or plies are
laid up,
laminated and cured to form CFRP components.
SUMMARY
[0006] In an example, a composite stringer is described. The composite
stringer
includes a skin flange having a first gage, a top flange having a second gage,
and a
web having a third gage and extending between the skin flange and the top
flange.
The skin flange is configured to be coupled to a support structure. The
support
structure includes at least one of a skin of a vehicle or a base charge. The
second
gage of the top flange is greater than the first gage of the skin flange and
the third
gage of the web. The skin flange, the top flange, and the web include a
plurality of
.. plies of composite material.
[0007] In another example, a method of forming a composite stringer is
described.
The method includes positioning a plurality of plies of composite material on
a layup
to form a skin flange, a top flange, and a web extending between the skin
flange and
the top flange. After positioning the plurality of plies of composite material
on the
layup, the method includes curing the plurality of plies of composite material
to form a
composite stringer including the skin flange having a first gage, the top
flange having
a second gage, and the web having a third gage. The second gage of the top
flange
is greater than the first gage of the skin flange and the third gage of the
web.
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[0008] In another example, a method of forming a composite stringer is
described.
The method includes forming a skin flange having a first gage. The skin flange
is
configured to be coupled to a support structure. The support structure
includes at
least one of a skin of a vehicle or a base charge. The method also includes
forming
a top flange having a second gage, and forming a web having a third gage and
extending between the skin flange and the top flange. The second gage of the
top
flange is greater than the first gage of the skin flange and the third gage of
the web.
The skin flange, the top flange, and the web include a plurality of plies of
composite
material.
[0009] In another example, a method of forming a composite stringer
assembly is
described. The method includes forming a composite stringer including a skin
flange
having a first gage, a top flange having a second gage, and a web having a
third gage
and extending between the skin flange and the top flange. The second gage of
the
top flange is greater than the first gage of the skin flange and the third
gage of the
web. The skin flange, the top flange, and the web include a plurality of plies
of
composite material. The method also includes coupling the skin flange of the
composite stringer to a support structure. The support structure includes at
least one
of a skin of a vehicle or a base charge.
[0010] In an example, a composite stringer assembly is described. The
composite
stringer assembly includes a composite stringer and a radius filler. The
composite
stringer includes (i) a skin flange configured to be coupled to a support
structure, (ii) a
web, (iii) a lower corner portion extending from the skin flange to the web,
(iv) an inner
surface extending along the skin flange, the lower corner portion, and the
web, and
(v) an outer surface extending along the skin flange, the lower corner
portion, and the
web. At the lower corner portion, the outer surface is defined by a first
radius of
curvature, and the first radius of curvature is substantially constant between
the skin
flange and the web. The skin flange, the lower corner portion, and the web
include a
plurality of plies of composite material. The support structure includes at
least one of
a skin of a vehicle or a base charge. The radius filler includes a first
surface coupled
to the inner surface at the lower corner portion, a second surface configured
to couple
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to the support structure, and a third surface extending between the first
surface and
the second surface. The first surface of the radius filler is defined by a
second radius
of curvature, and the second radius of curvature is substantially constant
between the
second surface and the third surface.
[0011] In another example, a composite stringer assembly is described. The
composite stringer assembly includes a plurality of composite stringers and a
radius
filler. The plurality of composite stringers are axially aligned with each
other along a
longitudinal axis of the plurality of composite stringers. Each composite
stringer
includes: (i) a skin flange configured to be coupled to a support structure,
(ii) a web,
(iii) a top flange, (iv) a lower corner portion extending from the skin flange
to the web,
(v) an upper corner portion extending from the web to the top flange, (vi) an
inner
surface extending along the skin flange, the lower corner portion, the web,
the upper
corner portion, and the top flange, and (vii) an outer surface extending along
the skin
flange, the lower corner portion, the web, the upper corner portion, and the
top flange.
The outer surface is defined by a first radius of curvature.
[0012] The radius filler includes (a) a first surface coupled to the
inner surface at
the lower corner portion of each composite stringer, (b) a second surface
configured
to couple to the support structure, and (c) a third surface extending between
the first
surface and the second surface. The first surface of the radius filler is
defined by a
second radius of curvature. Along the longitudinal axis: (1) the composite
stringer
assembly has a total length that is equal to a sum of a respective length of
each
composite stringer, (2) the first radius of curvature is substantially
constant over the
total length of the composite stringer assembly, and (3) the second radius of
curvature
is substantially constant over the total length of the composite stringer
assembly.
[0013] The support structure includes at least one of a skin of a vehicle
or a base
charge. The top flange of a first composite stringer of the plurality of
composite
stringers has a gage that is different than a gage of the top flange of a
second
composite stringer of the plurality of composite stringers.
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[0014] In another example, a method of forming a composite stringer
assembly is
described. The method includes forming a plurality of composite stringers.
Forming
the plurality of composite stringers includes, for each composite stringer,
forming, from
a plurality of plies of composite material: (i) a skin flange, (ii) a web,
(iii) a top flange,
(iii) a lower corner portion extending from the skin flange to the web, (iv)
an upper
corner portion extending from the web to the top flange, (v) an inner surface
extending
along the skin flange, the lower corner portion, the web, the upper corner
portion, and
the top flange, and (vi) an outer surface extending along the skin flange, the
lower
corner portion, the web, the upper corner portion, and the top flange. Forming
the
plurality of composite stringers also includes, for each composite stringer,
forming, at
the lower corner portion, the outer surface with a first radius of curvature.
[0015] The method also includes positioning, on a support structure,
the plurality
of composite stringers in axial alignment with each other along a longitudinal
axis. The
support structure includes at least one of a skin of a vehicle or a base
charge. The
method further includes coupling, to the inner surface of each composite
stringer, a
radius filler at the lower corner portion of the composite stringer. A first
surface of the
radius filler is defined by a second radius of curvature.
[0016] Forming the plurality of composite stringers can include forming
the top
flange of a first composite stringer of the plurality of composite stringers
with a gage
that is different than a gage of the top flange of a second composite stringer
of the
plurality of composite stringers. Along the longitudinal axis: (a) the
composite stringer
assembly has a total length that is equal to a sum of a respective length of
each
composite stringer, (b) the first radius of curvature is substantially
constant over the
total length of the composite stringer assembly, and (c) the second radius of
curvature
is substantially constant over the total length of the composite stringer
assembly.
[0017] The features, functions, and advantages that have been discussed
can be
achieved independently in various examples or may be combined in yet other
examples further details of which can be seen with reference to the following
description and drawings.
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Date Recue/Date Received 2020-05-06
BRIEF DESCRIPTION OF THE FIGURES
[0018] The novel features believed characteristic of the illustrative
examples are
set forth in the appended claims. The illustrative examples, however, as well
as a
preferred mode of use, further objectives and descriptions thereof, will best
be
understood by reference to the following detailed description of an
illustrative example
of the present disclosure when read in conjunction with the accompanying
drawings,
wherein:
[0019] Figure 1 depicts a side view of an aircraft, according to an
example.
[0020] Figure 2 depicts a simplified block diagram of the aircraft,
according to an
example.
[0021] Figure 3A depicts a side view of a composite structure assembly,
according
to an example.
[0022] Figure 3B depicts a perspective view of the composite structure
assembly
shown in Figure 3A, according to an example.
[0023] Figure 4 depicts a composite structure, according to an example.
[0024] Figure 5 depicts a composite structure, according to another
example.
[0025] Figure 6 depicts a composite structure, according to another
example.
[0026] Figure 7 depicts a side view of a composite structure assembly,
according
to an example.
[0027] Figure 8A depicts a side view of a composite structure assembly,
according
to an example.
[0028] Figure 8B depicts a perspective view of the composite structure
assembly
shown in Figure 8A, according to an example.
[0029] Figure 9A depicts a side view of a composite structure assembly,
according
to an example.
[0030] Figure 9B depicts a perspective view of the composite structure
assembly
shown in Figure 9A, according to an example.
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Date Recue/Date Received 2020-05-06
[0031] Figure 10 depicts a side view of a composite structure assembly,
according
to an example.
[0032] Figure 11 depicts a side view of a composite structure assembly,
according
to an example.
[0033] Figure 12 depicts a side view of a composite structure assembly,
according
to an example.
[0034] Figure 13 depicts a side view of a composite structure assembly,
according
to an example.
[0035] Figure 14 depicts a side view of a composite structure assembly,
according
to an example.
[0036] Figure 15 depicts a side view of a composite structure assembly,
according
to an example.
[0037] Figure 16 illustrates a flow chart of an example process for
forming a
composite stringer, according to an example.
[0038] Figure 17 illustrates a flow chart of an example process for forming
a
composite stringer that can be used with the process shown in Figure 16.
[0039] Figure 18 illustrates a flow chart of an example process for
forming a
composite stringer that can be used with the process shown in Figure 17.
[0040] Figure 19 illustrates a flow chart of an example process for
forming a
composite stringer that can be used with the process shown in Figure 16.
[0041] Figure 20 illustrates a flow chart of an example process for
forming a
composite stringer, according to an example.
[0042] Figure 21 illustrates a flow chart of an example process for
forming a
composite stringer assembly, according to an example.
[0043] Figure 22 illustrates a flow chart of an example process for forming
a
composite stringer assembly that can be used with the process shown in Figure
21.
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Date Recue/Date Received 2020-05-06
[0044] Figure 23 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
21.
[0045] Figure 24 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
21.
[0046] Figure 25 illustrates a flow chart of an example process for forming
a
composite stringer assembly, according to an example.
[0047] Figure 26 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
25.
[0048] Figure 27 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
25.
[0049] Figure 28 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
25.
[0050] Figure 29 illustrates a flow chart of an example process for
forming a
composite stringer assembly, according to an example.
[0051] Figure 30 illustrates a flow chart of an example process for forming
a
composite stringer assembly that can be used with the process shown in Figure
29.
[0052] Figure 31 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
30.
[0053] Figure 32 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
30.
[0054] Figure 33 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
32.
[0055] Figure 34 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
32.
[0056] Figure 35 illustrates a flow chart of an example process for forming
a
composite stringer assembly that can be used with the process shown in Figure
29.
8
Date Recue/Date Received 2020-05-06
[0057] Figure 36 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
29.
[0058] Figure 37 illustrates a flow chart of an example process for
forming a
composite stringer assembly that can be used with the process shown in Figure
29.
[0059] Figure 38 illustrates a flow chart of an example process for forming
a
composite stringer assembly that can be used with the process shown in Figure
37.
[0060] Figure 39 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage, according to an example.
[0061] Figure 40 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 39.
[0062] Figure 41 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 39.
[0063] Figure 42 illustrates a flow chart of an example process for forming
a
composite structure having a variable gage that can be used with the process
shown
in Figure 39.
[0064] Figure 43 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 42.
[0065] Figure 44 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 43.
[0066] Figure 45 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 43.
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Date Recue/Date Received 2020-05-06
[0067] Figure 46 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 45.
[0068] Figure 47 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 39.
[0069] Figure 48 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 39.
[0070] Figure 49 illustrates a flow chart of an example process for forming
a
composite structure having a variable gage, according to an example.
[0071] Figure 50 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 49.
[0072] Figure 51 illustrates a flow chart of an example process for forming
a
composite structure having a variable gage that can be used with the process
shown
in Figure 50.
[0073] Figure 52 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 50.
[0074] Figure 53 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 50.
[0075] Figure 54 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 50.
Date Recue/Date Received 2020-05-06
[0076] Figure 55 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 50.
[0077] Figure 56 illustrates a flow chart of an example process for
forming a
composite structure having a variable gage that can be used with the process
shown
in Figure 50.
DETAILED DESCRIPTION
[0078] Disclosed examples will now be described more fully hereinafter
with
reference to the accompanying drawings, in which some, but not all of the
disclosed
examples are shown. Indeed, several different examples may be described and
should not be construed as limited to the examples set forth herein. Rather,
these
examples are described so that this disclosure will be thorough and complete
and will
fully convey the scope of the disclosure to those skilled in the art.
[0079] By the term "approximately" or "substantially" with reference to
amounts or
measurement values described herein, it is meant that the recited
characteristic,
parameter, or value need not be achieved exactly, but that deviations or
variations,
including for example, tolerances, measurement error, measurement accuracy
limitations and other factors known to those of skill in the art, may occur in
amounts
that do not preclude the effect the characteristic was intended to provide.
[0080] By the term "substantially constant" with reference to a amounts
or
measurement values described herein, it is meant that the recited
characteristic,
parameter, or value remains substantially unchanged, but that deviations or
variations,
including for example, tolerances, measurement error, measurement accuracy
limitations and other factors known to those of skill in the art, may occur in
amounts
that do not preclude the effect the characteristic was intended to provide.
[0081] As used herein, the terms "greater than" and "less than" are
intended to
have their common meaning. Thus, a first value is greater than a second value
if the
11
Date Recue/Date Received 2020-05-06
first value is greater than the second value by any amount. Similarly, a first
value is
less than a second value if the first value is less than the second value by
any amount.
[0082] As noted above, aircraft generally include one or more composite
stringers
coupled to one or more skin panels to help carry and/or transfer a load from
the skin
panels to another structure of the aircraft (e.g., a frame, a rib, and/or a
spar of the
aircraft). The composite stringers may be formed in a plurality of different
shapes such
as, for example, hat-shaped stringers, C-shaped stringers, J-shaped stringers,
Y-
shaped stringers, and/or Z-shaped stringers. Additionally, for example, many
types of
composite stringers include at least a skin flange that is configured to
couple to a
support structure (e.g., a skin panel), a top flange, and a web extending
between the
skin flange and the top flange.
[0083] In general, a load bearing performance of a composite stringer
may be
related to a gage of one or more portions of the composite stringer (i.e., a
gage of the
skin flange, the top flange, and/or the web). The gage of a given portion of
the
composite stringer is a measurement of a thickness between (i) an inner
surface of
the given portion, which faces toward the support structure when the skin
flange is
coupled to the composite stringer, and (ii) an outer surface of the given
portion, which
faces away from the support structure when the skin flange is coupled to the
composite stringer.
[0084] Conventionally, the skin flange, the web, and the top flange are all
formed
with a common or substantially equal gage. However, in some implementations
where
the top flange tends to bear a greater amount of a load relative to the skin
flange and
the web. As such, for a conventional composite stringer, the gage of the skin
flange,
the top flange, and the web may be based on a load bearing requirement of the
top
flange. As a result, the web and/or the skin flange of the conventional
composite
stringer generally have a greater gage than is needed to meet the load bearing
requirements of the web and/or the skin flange. This excess gage of the web
and/or
the skin flange can impose a weight penalty and/or increased manufacturing
costs.
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[0085] Additionally, for example, because the skin flange
conventionally has the
same gage as the top flange, the skin flange may have a stiffness that is
relatively
greater than a stiffness of the support structure (e.g., the skin panel) to
which the skin
flange is coupled. As used herein, the term "stiffness" means an extent to
which an
object (e.g., the skin flange and/or the support structure) resists
deformation in
response to an applied force. In some instances, a relatively large mismatch
between
the stiffness of the skin flange and the support structure may lead to
delamination of
the composite stringer from the support structure under certain mechanical
loads.
[0086] Also, for example, as different portions of the aircraft may be
expected to
experience different loads, the gage of the composite stingers may vary from
stringer
to stringer. For instance, the aircraft can include some composite stringers
having
relatively larger gages at locations on the aircraft that are expected to
experience a
relatively greater amount of loading and other composite stringers having
relatively
smaller gages at locations on the aircraft that are expected to experience a
relatively
lesser amount of loading. Because different composite stringers at different
locations
in an aircraft may have different gages, designing and manufacturing the
composite
stringers can be relatively complex and costly due to, for example, increased
weight
considerations and/or different tooling requirements to address the individual
stringer
designs.
[0087] One approach to strengthening and improving a durability of
conventional
composite stringers is to couple a radius filler to the composite stringer at
a "radius
filler region" or "noodle region" between the composite stringer and the
support
structure. In general, the radius filler region is formed between the support
structure
and a corner portion of the composite stringer, which is generally a curved or
bent
portion of the composite stringer between the skin flange and the web. The
radius
filler can be a composite material (e.g., CFRP) positioned in the radius
filler region.
Although the radius filler can help strengthen and improve the durability of
the
composite stringer, the radius filler incurs a weight penalty (which, in the
context of a
vehicle, can undesirably impact fuel efficiency and/or payload carrying
capabilities).
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[0088] Example composite stringers, composite stringer assemblies, and
methods
described herein can address at least some limitations of existing composite
stringers.
For instance, within examples, a composite stringer can include a skin flange
having
a first gage, a top flange having a second gage, and a web having a third gage
and
extending between the skin flange and the top flange. The second gage of the
top
flange is greater than the first gage of the skin flange and the third gage of
the web.
As such, the top flange can have a relatively greater gage to meet load
bearing
requirements, whereas the skin flange and the web can have a relatively lesser
gage
to reduce a weight of the composite stringer, reduce a cost of manufacture of
the
composite stringer, and/or mitigate delamination at an interface between the
skin
flange and the support structure.
[0089] The first gage of the skin flange can be configured such that a
stiffness of
the skin flange is approximately equal to a stiffness of the support
structure. This can
help to allow the skin flange to flex with the support structure under
mechanical loads
and, thus, further mitigate delamination at the interface between the skin
flange and
the support structure. Within examples, this improved flexibility of the skin
flange can
be achieved while having a relatively larger gage at the top flange to meet
load bearing
performance requirements of the composite stringer.
[0090] Additionally, within examples, when the first gage of the skin
flange and the
.. third gage of the web are reduced (e.g., relative to a conventional
composite stringer
having the same second gage at the top flange), a size and/or a shape of the
radius
filler can be reduced. This can help to further reduce a weight and/or a cost
to
manufacture the composite stringer.
[0091] The composite stringer and/or a radius filler can additionally
or alternatively
include one or more surfaces defined by constant radii of curvature. For
example, at
an interface between the composite stringer and the radius filler, the
composite
stringer and the radius filler can each be defined by a radius of curvature
that is
constant over a surface area of the interface. This can help to reduce a size
of the
radius filler, improve strength of the composite stringer assembly, simplify
tooling
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Date Recue/Date Received 2020-05-06
requirements for forming the composite stringer assembly, and/or reduce
variability
among a plurality of composite stringers.
[0092] Forming composite stringers with a plurality of different gages
and/or with
constant radii of curvature can help to reduce (or may minimize) a variability
among a
plurality of composite stringers at certain portions of the composite
stringers. For
instance, in an example, a plurality of composite stringers can have different
second
gages at the top flanges, but the composite stringers can have (i) the same
first gages
at the skin flanges, (ii) the same third gages at the webs, and/or (iii) the
same radii of
curvature at the interfaces with a radius filler. This can help reduce
manufacturing
costs and/or simplify tooling requirements for forming a composite stringer
assembly
including the composite stringers at least because the radius filler can
extend along
the composite stringers with a constant shape and/or a constant size that is
compatible
with all of the composite stringers.
[0093] In additional or alternative examples to those previously
described, a
composite stringer assembly can include a composite stringer, a support
structure,
and an overwrap coupled to the inner surface of the composite stringer and the
support structure. In this arrangement, the overwrap layer can help to support
the
web, the skin flange, and/or the radius filler and, thus, help to mitigate (or
may prevent)
delamination between the composite stringer, the radius filler, and/or the
support
structure. Providing the overwrap in this arrangement can additionally or
alternatively
help to reduce the first gage of the skin flange, reduce the third gage of the
web, and/or
reduce a size of the radius filler (e.g., relative to composite stringer
assemblies that
omit the overwrap layer).
[0094] Referring now to Figure 1, a side view of an aircraft 100 is
depicted,
according to an example. As shown in Figure 1, the aircraft 100 can include a
plurality
of assemblies such as, for example, a fuselage 110, a plurality of wing
assemblies
112, and an empennage 114. One or more propulsion units 116 can be coupled to
the wing assemblies 112, the fuselage 110, and/or other portions of the
aircraft 100.
Although the aircraft 100 shown in Figure 1 is generally representative of a
commercial
Date Recue/Date Received 2020-05-06
passenger aircraft, the teachings of the present disclosure can be applied to
other
passenger aircraft, cargo aircraft, military aircraft, rotorcraft, and other
types of
vehicles such as, for examples, aerospace vehicles (e.g., satellites, space
launch
vehicles, and/or rockets), watercraft, trains, automobiles, trucks, buses, or
other
suitable structures having one or more composite stringers.
[0095] Within examples, the fuselage 110, the wing assemblies 112,
and/or the
empennage 114 can include one or more composite structures. In general, a
composite structure is a structure that is formed from a plurality of
composite materials
that are bound together with sufficient strength that the composite materials
act as a
single unit from a structural point of view. A composite material (also called
a
composition material or shortened to composite, which is the common name) is a
material made from two or more constituent materials with significantly
different
physical or chemical properties that, when combined, produce a material with
characteristics different from the individual components.
[0096] Figure 2 is a simplified block diagram of the aircraft 100,
including the
fuselage 110, the wing assemblies 112, and the empennage 114, according to an
example. As shown in Figures 1-2, the fuselage 110, the wing assemblies 112,
and
the empennage 114 can each include one or more skin panels 218 and one or more
composite stringers 220. As noted above, the composite stringers 220 are
configured
to provide a predetermined flexural and torsional stiffness to the fuselage
110, the
wing assemblies 112, and the empennage 114. For example, the composite
stringers
220 can be configured to transfer bending loads in the skin panels 218, and
stiffen the
skin panels 218 so that the skin panels 218 do not buckle under loading.
[0097] Although Figure 2 depicts the composite stringers 220 for the
fuselage 110,
the wing assemblies 112, and the empennage 114, the aircraft 100 can include
the
composite stringers 220 in one or more other assemblies of the aircraft 100 to
stiffen
and/or transfer loads on those other assemblies. Within examples, the
composite
stringers 220 in the fuselage 110, the wing assemblies 112, and the empennage
114
may be subject to uniaxial tension and compression and out-of-plane buckling.
The
16
Date Recue/Date Received 2020-05-06
composite stringers 220 in the fuselage 110, the wing assemblies 112, and the
empennage 114 may also be subject to secondary loads including shear and
bearing
loads. A component under compression tends to twist, cripple and buckle. The
composite stringers 220 provide strength, resist compression and tension, and
provide
stability against twisting, crippling, and buckling forces. For example, the
composite
stringers 220 can provide support structures within the fuselage 110, the wing
assemblies 112, or the empennage 114 that may brace against various exerted
forces.
[0098] Referring now to Figures 3A-3B, a composite stringer assembly
301
including a composite stringer 320 coupled to a support structure 322 is
illustrated
according to an example. In particular, Figure 3A depicts a side view of the
composite
stringer 320 and the support structure 322, and Figure 3B depicts a
perspective view
of the composite stringer 320 and the support structure 322.
[0099] As shown in Figures 3A-3B, the composite stringer 320 includes a
skin
flange 324 configured to be coupled to the support structure 322, a top flange
326,
and a web 328 extending between the skin flange 324 and the top flange 326. In
Figures 3A-3B, the composite stringer 320 is in the form of a hat-shaped
stringer. As
such, the web 328 can extend from a first side 326A of the top flange 326, and
the
composite stringer 320 can further include a second skin flange 330 configured
to be
coupled to the support structure 322 and a second web 332 extending between
the
second skin flange 330 and a second side 326B of the top flange 326.
[0100] Although the composite stringer 320 shown in Figures 3A-3B is a
hat-
shaped stringer, as described below with respect to Figures 12-15, the
principles
described with respect to Figures 3A-3B can extend to apply to other types of
composite stringers (e.g., J-shaped stringers, C-shaped stringers, l-shaped
stringers,
and/or Z-shaped stringers). In particular, the concepts and principles
described herein
can be applied to any type of composite stringer that includes at least one
skin flange,
at least one web, and a top flange.
[0101] As noted above, the skin flange 324 and the second skin flange
330 are
configured to be coupled to the support structure 322. For example, the skin
flange
17
Date Recue/Date Received 2020-05-06
324 and the second skin flange 330 can extend in a plane that is substantially
parallel
to a surface of the support structure 322 to which the skin flange 324 and the
second
skin flange 330 are coupled. This can help to promote a relatively strong bond
between the composite stringer 320 and the support structure 322 at an
interface
between (i) the skin flange 324 and the second skin flange 330 and (ii) the
support
structure 322 due, at least in part, to a relatively large surface area of the
interface.
[0102] In Figures 3A-3B, the support structure 322 is a skin 323 of a
vehicle (e.g.,
the skin panel 210 of the fuselage 110, the wing assemblies 112, and/or the
empennage 114). However, as described below, the support structure 322 can
additionally or alternatively include a base charge coupled to the skin 323 of
the
vehicle. The base charge can include a plurality of plies of composite
material and
can be used, for example, to help support and cushion the composite stringer
320 on
the skin 323. Thus, more generally, the support structure 322 can include at
least one
of the skin 323 of the vehicle or the base charge.
[0103] The skin flange 324, the top flange 326, and the web 328, the second
skin
flange 330, and the second web 332 include a plurality of plies of composite
material.
As one example, the composite material can be carbon fiber reinforced plastic
("CFRP"). Each ply can include a reinforcement material and a matrix material.
The
matrix material can bind and supports the reinforcement material. As examples,
the
matrix material can include a non-conductive polymer such as an epoxy resin,
and the
reinforcement material can include one or more strands carbon fiber.
[0104] Additionally, as shown in Figures 3A-3B, the composite stringer
320 can
include an inner surface 334 extending along the skin flange 324, the web 328,
the
top flange 326, the second web 332, and the second skin flange 330. The inner
surface 334 faces the support structure 322 when the skin flange 324 and the
second
skin flange 330 are coupled to the support structure 322. The composite
stringer 320
also includes an outer surface 336 extending along the skin flange 324, the
web 328,
and the top flange 326, the second web 332, and the second skin flange 330.
The
18
Date Recue/Date Received 2020-05-06
outer surface 336 faces away from the support structure 322 when the skin
flange 324
and the second skin flange 330 are coupled to the support structure 322.
[0105] In this arrangement, the skin flange 324 has a first gage 338,
the top flange
326 has a second gage 340, and the web 328 has a third gage 342. The first
gage
338, the second gage 340, and the third gage 342 are respective thicknesses
between
the inner surface 334 and the outer surface 336 at the skin flange 324, the
top flange
326, and the web 328, respectively. As shown in Figures 3A-3B, the second gage
340 of the top flange 326 is greater than the first gage 338 of the skin
flange 324 and
the third gage 342 of the web 328. As used herein, the term "greater than" is
intended
to have its common meaning (i.e., that the second gage 340 is greater than the
first
gage 338 by any amount and the second gage 340 is greater than the third gage
342
by any amount).
[0106] In general, the top flange 326 bears a greater amount of a load
on the skin
323 relative to the skin flange 324 and the web 328. By providing the top
flange 326
with the second gage 340, which is greater than the first gage 338 of the skin
flange
324 and the third gage 342 of the web 328, the strength-to-weight ratio of the
composite stringer 320 can be improved relative to a composite stringer in
which the
skin flange 324, the web 328, and the top flange 326 all have the same gage.
Additionally, as described in further detail below, reducing the first gage
338 of the
skin flange 324 and the third gage 342 of the web 328 can provide a number of
additional benefits.
[0107] In Figures 3A-3B, the third gage 342 of the web 328 is
approximately equal
to the first gage 338 of the skin flange 324. As described in further detail
below with
respect to Figures 8A-8B, this can help to reduce (or may minimize or may
eliminate)
an amount of a radius filler that is coupled to the composite stringer 320.
However, in
other examples, the third gage 342 of the web 328 can be different than the
first gage
338 of the skin flange 324.
[0108] Also, within examples, the second skin flange 330 can have a
fourth gage
344 and the second web 332 can have a fifth gage 346. The fourth gage 344 and
the
19
Date Recue/Date Received 2020-05-06
fifth gage 346 can be respective thicknesses between the inner surface 334 and
the
outer surface 336 at the second skin flange 330 and the second web 332,
respectively.
In this example, the second gage 340 of the top flange 326 can be greater than
the
fourth gage 344 of the second skin flange 330 and the fifth gage 346 of the
second
web 332. As noted above, this can beneficially help to improve the strength-to-
weight
ratio of the composite stringer 320 relative to a composite stringer in which
the second
skin flange 330, the second web 332, and the top flange 326 all have the same
gage
[0109] Additionally, in Figures 3A-3B, the fourth gage 344 of the
second skin
flange 330 can be approximately equal to the fifth gage 346 of the second web
332.
As described in further detail below with respect to Figures 8A-8B, this can
help to
reduce (or may minimize or may eliminate) an amount of a radius filler that is
coupled
to the composite stringer 320. However, in other examples, the third gage 342
of the
web 328 can be different than the first gage 338 of the skin flange 324.
[0110] In one example, the second gage 340 can be approximately 1.5
millimeters
(mm) to approximately 16.0 mm. In this example, the first gage 338 and the
third gage
342 can be less than the second gage 340 and within a range of approximately
0.6
mm to approximately 12.0 mm. In another example, the second gage 340 can be
approximately 2.0 mm to approximately 14.0 mm. In this example, the first gage
338
and the third gage 342 can be less than the second gage 340 and within a range
of
approximately 0.8 mm to approximately 10.0 mm. In a further example, the
second
gage 340 can be approximately 2.4 mm to approximately 12.0 mm. In this
example,
the first gage 338 and the third gage 342 can be less than the second gage 340
and
within a range of approximately 1.0 mm to approximately 8.0 mm. Other examples
are also possible.
[0111] In one example, the second gage 340 can be approximately 10 percent
to
approximately 500 percent greater than the first gage 338 and the third gage
342. In
another example, the second gage 340 can be approximately 14 percent to
approximately 300 percent greater than the first gage 338 and the third gage
342. In
yet another example, the second gage 340 can be approximately 30 percent to
Date Recue/Date Received 2020-05-06
approximately 200 percent greater than the first gage 338 and the third gage
342. The
foregoing are illustrative examples of the second gage 340 being greater than
the first
gage 338 and/or the third gage 342. Other examples are also possible.
[0112] Within examples, the first gage 338 of the skin flange 324
and/or the fourth
gage 344 of the second skin flange 330 can be based, at least in part, on a
stiffness
of the skin 323 of the vehicle. For instance, a stiffness of the skin flange
324 and a
stiffness of the second skin flange 330 can be related to the first gage 338
of the skin
flange 324 and the fourth gage 344 of the second skin flange 330, respectively
(e.g.,
a relative large gage may contribute to a relatively high level of stiffness,
whereas a
relatively small gage may contribute to a relatively low level of stiffness).
[0113] In general, a relatively large mismatch between (i) the
stiffness of the skin
flange 324 and/or the second skin flange 330 and (ii) the skin 323 of the
vehicle may
lead to delamination of the composite stringer 320 from the skin 323 under
certain
mechanical loads. Within examples, the composite stringer assembly 301 of
Figure 3
can reduce (or may prevent) such delamination due to stiffness mismatches. For
instance, in some examples, the first gage 338 of the skin flange 324 and the
fourth
gage 344 of the second skin flange 330 can be configured such that a stiffness
of the
skin flange 324 and/or a stiffness of the second skin flange 330 is
approximately equal
to the stiffness of the skin 323 of the vehicle. This can help to enhance (or
may
maximize) energy absorption due to an impact and/or a load at an interface
between
(i) the skin 323 of the vehicle and (ii) the skin flange 324 or the second
skin flange
330, and mitigate (or may prevent) delamination between the composite stringer
320
and the skin 323.
[0114] As described above, the top flange 324 has the second gage 340,
which is
greater than the first gage 338 of the skin flange 324 and the fourth gage 344
of the
second skin flange 330. As such, the top flange 326 can have a stiffness that
is greater
than the stiffness of the skin flange 324 and/or the second skin flange 330.
Thus, the
composite stringer 320 can advantageously have a greater amount of stiffness
at the
top flange 326 where such stiffness is beneficial to carry and transfer loads,
and a
21
Date Recue/Date Received 2020-05-06
lesser amount of stiffness at the skin flange 324 and/or the second skin
flange 330
where it is beneficial to allow the composite stringer 320 to flex with the
skin 323 of
the vehicle so as to mitigate delamination.
[0115] As shown in Figure 3B, the composite stringer 320 has a
longitudinal axis
348 and, along a longitudinal axis 348, the composite stringer 320 has a
length 349
between a first end 350A of the composite stringer 320 and a second end 350B
of the
composite stringer 320. In Figure 3B, along the longitudinal axis 348: the
first gage
338 of the skin flange 324, the third gage 342 of the web 328, and/or the
second gage
340 of the top flange 326 are each substantially constant over the length 349
of the
composite stringer 320. Within examples, this can help to simplify stringer
fabrication,
reduce stringer tooling cost, and/or reduce fabrication time. This can
additionally or
alternatively help to improve the quality of the composite stringer 320 due
to, for
example, reduced (or minimized) variation of the first gage of skin flange 324
and the
third gage 342 of the web 328 over the length 349. Similarly, along the
longitudinal
axis 348: the fourth gage 344 of the second skin flange 330 and the fifth gage
346 of
the second web 332 are each substantially constant over the length 349 of the
composite stringer 320.
[0116] As noted above, the skin flange 324, the top flange 326, and the
web 328,
the second skin flange 330, and the second web 332 include the plurality of
plies of
composite material. In an example, the plurality of plies of composite
material include
a plurality of fibers, and the plurality of fibers include approximately 30
percent or more
of the skin flange 324, the top flange 326, and the web 328, the second skin
flange
330, and the second web 332 along the longitudinal axis. This can, for
example,
improve a stiffness of the top flange 326 while reducing weight, fabrication
costs,
and/or material costs.
[0117] In one example, the plurality of plies that form the composite
stringer 320
can be laid up at traditional ply angles relative to the longitudinal axis
348. As such,
the plurality of plies of the composite material can each have a ply angle,
relative to
the longitudinal axis 348 of the composite stringer 320, which is equal to any
one of
22
Date Recue/Date Received 2020-05-06
the group of ply angles consisting of 0 degrees, +45 degrees, -45 degrees, and
90
degrees. In another example, the plurality of plies can be laid up at
nontraditional ply
angles relative to the longitudinal axis 348. For instance, at least one ply
of the
plurality of plies of composite material can have a ply angle, relative to the
longitudinal
axis 348 of the composite stringer 320, which is not equal to any one of a
group of ply
angles consisting of: 0 degrees, +45 degrees, -45 degrees, and 90 degrees.
This can,
for example, help provide the composite stringer 320 with sufficient
flexibility to fit into
a contoured panel surface and/or improve fabrication quality.
[0118] Within examples, the composite stringer 320 can further include
one or
more corner portions, which each provides a transition section between two
other
portions of the composite stringer 320 (i.e., between two of the skin flange
324, the
web 328, the top flange 326, the second web 332, and the second skin flange
330).
For instance, in Figures 3A-3B, the corner portion(s) of the composite
stringer 320 can
include (i) a lower corner portion 352 extending from the skin flange 324 to
the web
328, (ii) an upper corner portion 354 extending from the web 328 to the top
flange 326,
(iii) a second lower corner portion 356 extending from the second skin flange
330 to
the second web 332, and/or (iv) a second upper corner portion 358 extending
from
the second web 332 to the top flange 326. In implementations in which the
composite
stringer 320 includes two or more corner portions, the term "lower" means
closer to
the support structure 322 than the top flange 326 when the composite stringer
320 is
coupled to the support structure 322, and the term "upper" means closer to the
top
flange 326 than the support structure 322 when the composite stringer 320 is
coupled
to the support structure 322. However, in implementations in which the
composite
stringer 320 includes a single corner portion, the terms "lower" and "upper"
may be
used interchangeably unless context dictates otherwise.
[0119] In general, the lower corner portion 352 can provide a
transition section
between the skin flange 324 and the web 328, whereas the upper corner portion
354
can provide a transition section between the web 328 and the top flange 326.
Similarly, the second lower corner portion 356 can provide a transition
section
between the second skin flange 330 and the second web 332, whereas the second
23
Date Recue/Date Received 2020-05-06
upper corner portion 358 can provide a transition section between the second
web
332 and the top flange 326.
[0120] For example, in Figures 3A-3B, the skin flange 324, the web 328,
the top
flange 326, the second web 332, and the second skin flange 330 can be planar
structures that each extend in a respective plane in space. The respective
planes in
which the skin flange 324, the web 328, the top flange 326, the second web
332, and
the second skin flange 330 extend can be different from each other. As such,
the
lower corner portion 352, the upper corner portion 354, the second lower
corner
portion 356, and/or the second upper corner portion 358 can include a curved
shape
and/or a bent shape that facilitates transitioning from one plane to another.
[0121] For instance, Figures 3A-3B indicates a coordinate system 360,
and Figure
3A depicts the composite stringer assembly 301 in an X-Y plane of the
coordinate
system 360. As shown in Figures 3A-3B, the skin flange 324, the top flange
326, and
the second skin flange 330 each extend in a respective plane parallel to an X-
Z plane
of the coordinate system 360, whereas the web 328 and the second web 332 can
each extend in a respective plane that is transverse to the X-Z plane of the
coordinate
system 360. In this arrangement, the lower corner portion 352 can define an
angle
362 between the skin flange 324 and the web 328, the upper corner portion 354
can
define an angle 364 between the web 328 and the top flange 326, the second
lower
corner portion 356 can define an angle 366 between the second skin flange 330
and
the second web 332, and the second upper corner portion 358 can define an
angle
368 between the second skin flange 330 and the second web 332.
[0122] In one example, the angle 362 between the skin flange 324 and
the web
328 can be between approximately 95 degrees and approximately 150 degrees, and
the angle 366 between the second skin flange 330 and the second web 332 can be
between approximately 95 degrees and approximately 150 degrees. In another
example, the angle 362 and/or the angle 366 can be between approximately 100
degrees and approximately 135 degrees. This can help to enhance a stiffness,
reduce
a weight, reduce a cost of fabrication, and/or reduce a cost of material for
the
24
Date Recue/Date Received 2020-05-06
composite stringer 320. Additionally, in an example, the angle 364 between the
web
328 and the top flange 326 can be between approximately 95 degrees and
approximately 150 degrees, and the angle 368 between the second web 332 and
the
top flange 326 can be between approximately 95 degrees and approximately 150
degrees. In another example, the angle 364 and/or the angle 368 can be between
approximately 100 degrees and approximately 135 degrees. This can also help to
enhance a stiffness, reduce a weight, reduce a cost of fabrication, and/or
reduce a
cost of material for the composite stringer 320.
[0123] In the example shown in Figures 3A-3B, the skin flange 324, the
web 328,
the top flange 326, the second web 332, and the second skin flange 330 are
planar
structures. However, in other examples, the skin flange 324, the web 328, the
top
flange 326, the second web 332, and/or the second skin flange 330 can be
nonplanar
structures. For instance, the skin flange 324 and/or the second skin flange
330 can
be a nonplanar structure so as to conform to a nonplanar shape of the support
structure 322.
[0124] Additionally or alternatively, the lower corner portion 352, the
upper corner
portion 354, the second lower corner portion 356, and/or the second upper
corner
portion 358 can be configured to transition from one gage to another gage. For
instance, in Figures 3A-3B, the upper corner portion 354 provides for
transitioning
from the second gage 340 of the top flange 326 to the third gage 342 of the
web 328,
where the second gage 340 is greater than the third gage 342. As such, the
upper
corner portion 354 can have a variable gage that decreases in a direction from
the top
flange 326 toward the web 328. Similarly, in Figures 3A-3B, the second upper
corner
portion 358 provides for transitioning from the second gage 340 of the top
flange 326
to the fifth gage 346 of the second web 332. As such, the second upper corner
portion
358 can have a variable gage that decreases from the top flange 326 toward the
second web 332.
[0125] In Figures 3A-3B, the first gage 338 of the skin flange 324 is
approximately
equal to the third gage 342 of the web 328, and the fourth gage 344 of the
second
Date Recue/Date Received 2020-05-06
skin flange 330 is approximately equal to the fifth gage 346 of the second web
332.
As such, in Figures 3A-3B, the lower corner portion 352 can have a gage that
is
approximately equal to the first gage 338 and the third gage 342, and the
second lower
corner portion 356 can have a gage that is approximately equal to the fourth
gage 344
and the fifth gage 346. However, in other examples in which the skin flange
324, the
web 328, the second skin flange 330, and/or the second web 332 have different
gages
relative to each other, the lower corner portion 352 and/or the second lower
corner
portion 356 can have a variable gage that increases or decreases between the
skin
flange 324, the web 328, the second skin flange 330, and/or the second web
332.
[0126] Within examples, to transition from one gage to another gage, the
lower
corner portion 352, the upper corner portion 354, the second lower corner
portion 356,
and/or the second upper corner portion 358 can include a plurality of
continuous plies
and one or more drop-off plies. In general, each continuous ply extends from a
first
end to a second end of the lower corner portion 352, the upper corner portion
354, the
second lower corner portion 356, and/or the second upper corner portion 358.
By
contrast, each drop-off ply extends from the first end to a respective
position of a tip
of the drop-off ply between the first end and the second end. In this
arrangement,
there are fewer plies at the second end relative to the first end. Thus, by
positioning
the tips of the drop-off plies between the first end and the second end, the
gage
.. decreases from the first end to the second end so as to transition from one
gage to
another gage.
[0127] For example, in Figures 3A-3B, the plurality of plies of
composite material
can include a plurality of continuous plies and a plurality of drop-off plies.
As noted
above, in Figures 3A-3B, the upper corner portion 354 can facilitate
transitioning from
the second gage 340 of the top flange 326 to the third gage 342 of the web
328. In
this example, the skin flange 324, the web 328, the upper corner portion 354,
and the
top flange 326 can include each continuous ply. Additionally, in this example,
the top
flange 326 and the upper corner portion 354 can include each drop-off ply,
whereas
the skin flange 324 and the web 328 can omit the drop-off plies. In
particular, for
instance, each drop-off ply can have a free end (i.e., a tip) at the upper
corner portion
26
Date Recue/Date Received 2020-05-06
354 such that the drop-off ply does not extend to the web 328 and the skin
flange 324.
As described in further detail below, the free end of each drop-off ply can
have a blunt-
end shape and/or a tapered shape.
[0128] As examples, Figures 4-6 each depict a respective composite
structure
having a variable gage for transitioning from one gage to another gage. The
composite structures shown in Figures 4-6 can be a corner portion of the
composite
stringer 320 such as, for example, the lower corner portion 352, the upper
corner
portion 354, the second lower corner portion 356, and/or the second upper
corner
portion 358 shown in Figures 3A-3B.
[0129] Figure 4 depicts a composite structure 470 according to an example.
As
shown in Figure 4, the composite structure 470 includes a first end 470A
having a first
gage 472A and a second end 470B having a second gage 472B, which is less than
the first gage 472A of the first end 470A. The composite structure 470 also
includes
an inner surface 434 extending from the first end 470A to the second end 470B,
and
an outer surface 436 extending from the first end 470A to the second end 470B.
[0130] In one implementation, the first end 470A and the second end
470B can be
respective interfaces between the composite structure 470 and other portions
of a
composite stringer (e.g., the composite stringer 320). For instance, in an
example in
which the composite structure 470 is the upper corner portion 354 in Figure 3,
the first
end 470A can be a first interface between the upper corner portion 354 and the
top
flange 326, and the second end 470B can be a second interface between the
upper
corner portion 354 and the web 328 in Figure 3. Also, in this example, the
first gage
472A of the first end 470A of the composite structure 470 can be approximately
equal
to the second gage 340 of the top flange 326, and the second gage 472B of the
second
end 470B of the composite structure 470 can be approximately equal to the
third gage
342 of the web 328.
[0131] In other examples (e.g., in which the composite structure 470 is
the lower
corner portion 352, the second lower corner portion 356, or the second upper
corner
portion 358), the first gage 472A of the first end 470A and the second gage
472B of
27
Date Recue/Date Received 2020-05-06
the second end 470B can correspond to respective ones of the first gage 338,
the
second gage 340, the third gage 342, the fourth gage 344, and/or the fifth
gage 346
to facilitate transitioning between corresponding ones of the skin flange 324,
the web
328, the top flange 326, the second web 332, and the/or the second skin flange
330.
[0132] As also shown in Figure 4, the composite structure 470 includes a
plurality
of plies 4741.1 to 474=n of composite material (hereinafter collectively
referred to as
"plies 474") arranged in a stack between the inner surface 434 and the outer
surface
436, where n is an integer value that is greater than or equal to two. In
Figure 4, the
composite structure 470 includes a total of 18 plies 474 (i.e., n=18).
However, in other
examples, the composite structure 470 can include a lesser quantity or a
greater
quantity of plies 474.
[0133] In this arrangement, the first gage 472A of the first end 470A
and the
second gage 472B of the second end 470B are respective thicknesses between the
inner surface 434 and the outer surface 436 at the first end 470A and the
second end
470B, respectively. Further, the first gage 472A is related to a quantity of
the plies
474 at the first end 470A and the second gage 472B is related to a quantity of
the
plies 474 at the second end 470B. For instance, in Figure 4, the quantity of
the plies
474 at the first end 470A is greater than the quantity of the plies 474 at the
second
end 470B such that the first gage 472A is greater than the second gage 472B.
[0134] Specifically, to vary the quantity of the plies 474 between the
first end 470A
and the second end 470B, the plies 474 of composite material include a
plurality of
continuous plies 474A and a plurality of drop-off plies 474B. In Figure 4,
each
continuous ply 474A extends from the first end 470A to the second end 470B.
Whereas, each drop-off ply 474B includes a tip 476, and each drop-off ply 474B
extends from the first end 470A to a respective position of the tip 476 of the
drop-off
ply 474B between the first end 470A and the second end 470B.
[0135] Accordingly, while the continuous plies 474A are present at the
first end
470A and the second end 470B, the drop-off plies 474B are present at the first
end
470A and absent at the second end 470B. In this way, the drop-off plies 474B
can
28
Date Recue/Date Received 2020-05-06
contribute to the first gage 472A at the first end 470A, whereas the drop-off
plies 474B
do not contribute to the second gage 472B at the second end 470B due to the
drop-
off plies 474B terminating prior to the second end 470B (i.e., the tips 476
being located
at the respective positions between the first end 470A and the second end
470B).
[0136] For clarity of illustration, in Figure 4, a representative subset of
the
continuous plies 474A are labeled with reference number 474A and a
representative
subset of the drop-off plies 474B are labeled with reference number 474B.
However,
each of the plies 474 that extends entirely from the first end 470A to the
second end
470B is one of the continuous plies 474A, and each of the plies 474 that
terminates
between the first end 470A and the second end 470B is one of the drop-off
plies 474B.
Specifically, in Figure 4, the plies 474=1_3,9-18 are the continuous plies
474A, and the
plies 474=4_8 are the drop-off plies 474B.
[0137] As shown in Figure 4, the tip 476 of each drop-off ply 474B has
a blunt-end
shape, and the drop-off plies 474B are arranged immediately next to each other
in the
stack (e.g., in a cluster). In general, this approach to transitioning from
one gage to
another gage can be effective. However, it has been found that the performance
of
the composite structure 470 (and/or a composite stringer 320 incorporating the
composite structure 470) can be improved using one or more of the techniques
described in detail below with respect to Figures 5-6.
[0138] For example, using drop-off plies 474B with blunt-end shaped tips
476
and/or arranging the drop-off plies 474B in a cluster can result in a
relatively large
resin pocket in a region 478 at or near the tips 476 of the drop-off plies
474B. In some
instances, the relatively large resin pocket in the region 478 could lead to
delamination
in the region 478 under certain thermal and/or mechanical loads. Additionally,
for
example, arranging the tips 476 of the drop-off plies 474B in a cluster may
increase a
risk of ply kinks and/or wrinkles, which may reduce laminate strength.
Further, in some
instances, arranging the tips 476 of the drop-off plies at an off-center
location (e.g.,
closer to the outer surface 436 than the inner surface 434) can also increase
a risk of
29
Date Recue/Date Received 2020-05-06
ply kinks and/or wrinkles, which can have a reduced static strength and/or a
reduced
fatigue strength due to potential distortion under thermal and/or mechanical
loads.
[0139]
Within examples, composite structures having variable gages are
described, which can improve upon the composite structure 470 in one or more
respects. For instance, in some examples, the tips 476 of the drop-off plies
474B can
have a tapered shape and/or the plies 474 can be arranged according to one or
more
patterns that enhance the load carrying capabilities of the composite
structure 470.
[0140]
Referring now to Figure 5, a composite structure 570 having a variable
gage is depicted according to another example. As shown in Figure 5, the
composite
structure 570 includes a first end 570A having a first gage 572A and a second
end
570B having a second gage 572B, which is less than the first gage 572A of the
first
end 570A. Additionally, as shown in Figure 5, the composite structure 570
includes
an inner surface 534 extending from the first end 570A to the second end 570B,
and
an outer surface 536 extending from the first end 570A to the second end 570B.
[0141] As also shown in Figure 5, the composite structure 570 includes a
plurality
of plies 574.1 to 574=n of composite material (hereinafter collectively
referred to as
"plies 574") arranged in a stack between the inner surface 534 and the outer
surface
536, where n is an integer value that is greater than or equal to two. In
Figure 5, the
composite structure 570 includes a total of 28 plies 574 (i.e., n=28).
However, in other
examples, the composite structure 570 can include a lesser quantity or a
greater
quantity of plies 574.
[0142]
In this arrangement, the first gage 572A of the first end 570A and the
second gage 572B of the second end 570B are respective thicknesses between the
inner surface 534 and the outer surface 536 at the first end 570A and the
second end
570B, respectively. Further, as described above, the first gage 572A is
related to a
quantity of the plies 574 at the first end 570A and the second gage 572B is
related to
a quantity of the plies 574 at the second end 570B. For instance, in Figure 5,
the
quantity of the plies 574 at the first end 570A is greater than the quantity
of the plies
Date Recue/Date Received 2020-05-06
574 at the second end 570B such that the first gage 572A is greater than the
second
gage 572B.
[0143] As described above, the variable gage of the composite structure
570
results from the plies 574 of composite material including a plurality of
continuous plies
574A and a plurality of drop-off plies 574B arranged in the stack between the
inner
surface 534 and the outer surface 536. In Figure 5, each continuous ply 574A
extends
from the first end 570A to the second end 570B. Whereas, each drop-off ply
574B
extends from the first end 570A to a respective position of a tip 576 of the
drop-off ply
574B between the first end 570A and the second end 570B. Thus, the first gage
572A
is based on a quantity of the continuous plies 574A and a quantity of the drop-
off plies
574B, and the second gage 572B is based on the quantity of the continuous
plies
574A (and not the quantity of the drop-off plies 574B).
[0144] For clarity of illustration, in Figure 5, a representative
subset of the
continuous plies 574A are labeled with reference number 574A and a
representative
subset of the drop-off plies 574B are labeled with reference number 574B.
However,
each of the plies 574 that extends entirely from the first end 570A to the
second end
570B is one of the continuous plies 574A, and each of the plies 574 that
terminates
between the first end 570A and the second end 570B is one of the drop-off
plies 574B.
Specifically, in Figure 5, the plies 574=1-6, 8, 10, 12, 14,15, 17, 19, 21,
23, 25-28 are the continuous
plies 574A, and the plies 574=7,9,11,13,16, 18, 20, 22,24 are the drop-off
plies 574B.
[0145] As shown in Figure 5, the tip 576 of each drop-off ply 574B has
a tapered
shape. More particularly, for example, the tip 576 of each drop-off ply 574B
can
gradually reduce in thickness in a direction along the tip 576 from the first
end 570A
toward the second end 570B. Because the tip 576 has the tapered shape, the tip
576
can more closely abut against adjacent ones of the plies 574 (e.g., as
compared to
the blunt-end shaped tips 476 in Figure 4, which terminate relatively
abruptly). As
such, the tips 576 having the tapered shape can reduce (or may minimize) resin
pockets at the tips 576 of the drop-off plies 574B, which can help to improve
(or may
maximize) interlaminar strength of the composite structure 570. Accordingly,
the
31
Date Recue/Date Received 2020-05-06
tapered shape of the tips 576 of the drop-off plies 574B can help to improve a
load
bearing performance of the composite structure 570 having the variable gage
for
transitioning from a section having the first gage 572A to a section having
the second
gage 572B.
[0146] Within examples, the tapered shape of the tips 576 of the drop-off
plies
574B can be formed by cutting each drop-off ply 574B at an angle less than
approximately 85 degrees relative to a longitudinal axis of the drop-off ply
574B. By
contrast, the blunt-end shape of the tips 476 of the drop-off plies 474B shown
in Figure
4 can be formed, for example, by cutting each drop-off ply 474B at an angle of
approximately 90 degrees relative to a longitudinal axis of the drop-off ply
474B.
[0147] As noted above, the load bearing performance of the composite
structure
570 can be enhanced, additionally or alternatively, based on a pattern in
which the
plies 5741 are arranged in the composite structure 570. For example, in Figure
5, the
drop-off plies 574B are separated from each other by at least one of the
continuous
plies 574A. More particularly, in Figure 5, each drop-off ply 574B is
sandwiched
between and abuts against a respective two continuous plies 574A of the
plurality of
continuous plies 574A. By separating the drop-off plies 574B from each other
and/or
sandwiching the drop-off plies 574B between the continuous plies 574A, the
drop-off
plies 574B can be more uniformly distributed between the inner surface 534 and
the
.. outer surface 536 (as compared to the clustered arrangement of the drop-off
plies
474B shown in Figure 4). This can help to reduce (or may prevent) ply kinks
and/or
wrinkles, reduce (or may prevent) resin pockets, and/or increase (or may
maximize)
interlaminar strength of the composite structure 570.
[0148] As noted above, in Figure 5, the plies 5741=1-6,8, 10, 12,14,
15, 17, 19, 21, 23, 25-28 are
the continuous plies 574A, and the plies 574=7, 9, 11, 13, 16, 18, 20, 22, 24
are the drop-off
plies 574B. Accordingly, in Figure 5, each of the plies 574=7, 9, 11, 13, 16,
18, 20, 22, 24 is
separated from each other by at least one of the plies 5741=1-6, 8, 10, 12,
14, 15, 17, 19, 21, 23,
25-28, and each of the plies 574=7,9, 11, 13, 16, 18, 20, 22, 24 is sandwiched
between and abuts
against a respective two of the plies 5741=1-6,8, 10, 12, 14, 15, 17, 19, 21,
23, 25-28. For instance,
32
Date Recue/Date Received 2020-05-06
in Figure 5, the ply 5741=7 is separated from the ply 574=9 by the ply 5741=8,
and the ply
5741=7 is sandwiched between the ply 5741=6 and the ply 5741=8. Additionally,
for
instance, the ply 574=9 is separated from the ply 5741=ii by the ply 5741.10,
separated
from the ply 574=9 by the ply 5741=8, and sandwiched between the ply 5741=8
and the
ply 5741.10. Further, for instance, the ply 5741=16 is separated from the ply
5741=13 by
the plies 574=14,18, separated from the ply 5741=18 by the ply 574=17, and
sandwiched
between the ply 574=15 and the ply 574=17. Similar relationships exist for a
remainder
of the drop-off plies 574B in Figure 5 (i.e., the plies 5741=11, 13, 18, 20,
22, 24). As noted
above, arranging the plies 574 in a pattern having a characteristic of the
drop-off plies
574B interleaved with the continuous plies 574A (e.g., as shown in Figure 5)
can help
to reduce (or may prevent) ply kinks and/or wrinkles, reduce (or may prevent)
resin
pockets, and/or increase (or may maximize) interlaminar strength of the
composite
structure 570.
[0149] Within examples, the pattern of the tips 576 of the drop-off
plies 574B can
additionally or alternatively include one or more of the following
characteristics: (i) an
arrangement of the tips 576 in a first half of the composite structure 570 in
a pattern
that mirrors a pattern of the tips 576 in a second half of the composite
structure 570,
(ii) a staggered arrangement of the tips 576 relative to each other, and/or
(iii) spacing
the tips 576 relative to each other by at least one threshold distance (e.g.,
at least one
distance related to respective positions and/or respective thicknesses of one
or more
of the plies 574). Each of these characteristics alone or in combination can
contribute
to arranging the drop-off plies 574B in a pattern that can reduce (or may
prevent) ply
kinks and/or wrinkles, reduce (or may prevent) resin pockets, and/or increase
(or may
maximize) interlaminar strength.
[0150] Figure 5 shows the tips 576 arranged in mirror patterns relative to
a central
portion 580 of the composite structure 570 according to one example. The
central
portion 580 can include one or more of the plies 574 that provide a frame of
reference
for characterizing patterns of the tips 576 of the drop-off plies 574B on
opposing sides
of the central portion 580. In general, the central portion 580 (i) is between
the inner
33
Date Recue/Date Received 2020-05-06
surface 534 and the outer surface 536 and (ii) extends from the first end 570A
to the
second end 570B.
[0151] In Figure 5, the central portion 580 can include the plies
5741=15,16. Thus, in
Figure 5, the central portion 580 can include a single drop-off ply 574B
(i.e., the ply
5741=16) and a single continuous ply 574A (i.e., the ply 574=15). However, in
another
example, the central portion 580 can include two drop-off plies 574B and at
least one
continuous ply 574A. In yet another example, the central portion 580 can
consist of
only a single drop-off ply 574B. In another example, the central portion 580
can
consist of one or more continuous plies 574A and omit the drop-off plies 574B.
More
generally, the central portion 580 can include one or more of the continuous
plies 574A
and/or one or more of the drop-off plies 574B.
[0152] As noted above, the tips 576 of the drop-off plies 574B can be
arranged in
substantially mirror or mirror patterns relative to the central portion 580.
For instance,
a first subset of the drop-off plies 574B can be between the outer surface 536
and the
central portion 580, and a second subset of the drop-off plies 574B can be
between
the central portion 580 and the inner surface 534. In this arrangement, the
tips 576 of
the first subset of the drop-off plies 574B are arranged in a pattern that
substantially
mirrors a pattern of the tips 576 of the second subset of the drop-off plies
574B. In
other words, with reference to the central portion 580, the respective
positions of the
.. tips 576 of the first subset of the drop-off plies 574B are (i) reversely
and (ii) similarly
(or identically) arranged in comparison to the respective positions of the
tips 576 of
the second subset of the drop-off plies 574B.
[0153] For example, in Figure 5, the central portion 580 can include
the plies
5741=15,16, the first subset of the drop-off plies 574B can include the plies
5741=7,9, 11, 13,
and the second subset of the drop-off plies 574B can include the plies
5741=18,20,22,24.
As shown in Figure 5, the pattern of the tips 576 of the first subset of the
drop-off plies
574B substantially mirrors the pattern of the tips 576 of the second subset of
the drop-
off plies 574B. For instance, with reference to the central portion 580, the
respective
34
Date Recue/Date Received 2020-05-06
positions of the tips 576 of the first subset are reversely and similarly
arranged in
comparison to the respective positions of the tips 576 of the second subset.
[0154] Additionally, as shown in Figure 5, the pattern of the tips 576
of the drop-
off plies 574B can be a monotonically-outward pattern. For instance, in Figure
5, the
first subset of the drop-off plies 574B can be in an order from a drop-off ply
574B
closest to the central portion 580 (e.g., the ply 5741=13) to a drop-off ply
574B closest
to the outer surface 536 (i.e., the ply 5741=7). The pattern of the tips 576
of the first
subset of the drop-off plies 574B can include, with each successive drop-off
ply 574B
in the order, a relative distance between the tip 576 of the drop-off ply 574B
and the
second end 570B decreases. As such, in Figure 5, (i) the tip 576 of the ply
5741=13 is
at a first distance from the second end 570B, (ii) the tip 576 of the ply
574=i1 is at a
second distance from the second end 570B, which is less than the first
distance, (iii)
the tip 576 of the ply 5741=9 is at a third distance from the second end 570B,
which is
less than the second distance, and (iv) the tip 576 of the ply 5741=7 is at a
fourth
distance from the second end 570B, which is less than the third distance.
[0155] Similarly, the second subset of the drop-off plies 574B can be
in an order
from a drop-off ply 574B closest to the central portion 580 (e.g., the ply
5741=18) to a
drop-off ply 574B closest to the inner surface 534 (e.g., the ply 5741=24).
The pattern
of the tips 576 of the second subset of the drop-off plies 574B includes, with
each
successive drop-off ply 574B in the order, a relative distance between the tip
576 of
the drop-off ply 574B and the second end 570B decreases. As such, in Figure 5,
(v)
the tip 576 of the ply 5741=18 is at a fifth distance from the second end
570B, (vi) the
tip 576 of the ply 574.20 is at a sixth distance from the second end 570B,
which is less
than the fifth distance, (vii) the tip 576 of the ply 5741=22 is at a seventh
distance from
the second end 570B, which is less than the sixth distance, and (viii) the tip
576 of the
ply 5741=24 is at an eighth distance from the second end 570B, which is less
than the
seventh distance.
[0156] Accordingly, in the monotonically-outward pattern of the tips
576 shown in
Figure 5, the tips 576 of the drop-off plies 574B generally appear to be
spread outward
Date Recue/Date Received 2020-05-06
from the central portion 580 in a direction from the first end 570A to the
second end
570B. The monotonically-outward pattern of the tips 576 can help to more
gradually
and/or smoothly transition from the first gage 572A at the first end 570A to
the second
gage 572B at the second end 570B. Additionally, for example, the monotonically-
outward pattern of the tips 576 can help to achieve a relatively greater
degree of
symmetry relative to, for instance, the arrangement of the tips 476 in Figure
4 (which
are clustered near the outer surface 436).
[0157] According to an additional or alternative aspect of the
monotonically-
outward pattern shown in Figure 5, the drop-off plies 574B can be arranged in
a
plurality of pairs of drop-off plies 574B that define an order in which the
drop-off plies
574B drop off in a direction from the first end 570A toward the second end
570B (i.e.,
an order of the respective positions of the tips 576 in the direction from the
first end
570A toward the second end 570B). In particular, each pair of drop-off plies
574B can
include a respective one drop-off ply 574B of the first subset and a
respective one
drop-off ply 574B of the second subset.
[0158] For example, in Figure 5, a first pair includes the plies
5741=13,18, a second
pair includes the plies 5741=11,20, a third pair includes the plies 5741=9,22,
and a fourth
pair includes the plies 5741=7,24. As shown in Figure 5, in the direction from
the first
end 570A to the second end 570B, the drop-off plies 574B drop off in an order
from
the first pair to the fourth pair. In other words, the tips 576 of the first
pair of the drop-
off plies 574B are closest to the first end 570A, the tips 576 of the second
pair of the
drop-off plies 574B are second closest to the first end 570A, the tips 576 of
the third
pair of the drop-off plies 574B are third closest to the first end 570A, and
the tips 576
of the fourth pair of the drop-off plies 574B are farthest from the first end
570A.
[0159] Additionally, for example, for each pair of drop-off plies 574B, the
respective one drop-off ply 574B of the first subset and the respective one
drop-off ply
574B of the second subset can be substantially equidistant from the central
portion
580 in a dimension between the outer surface 536 and the inner surface 534.
For
instance, as shown in Figure 5, the first pair of the drop-off plies 574B are
each spaced
36
Date Recue/Date Received 2020-05-06
from the central portion 580 by a distance equal to a ply thickness 582 of a
single ply
574, the second pair of the drop-off plies 574B are each spaced from the
central
portion 580 by a distance equal to three times the ply thickness 582, the
third pair of
the drop-off plies 574B are each spaced from the central portion 580 by a
distance
equal to five times the ply thickness 582, and the fourth pair of the drop-off
plies 574B
are each spaced from the central portion 580 by a distance equal to seven
times the
ply thickness 582.
[0160] Arranging the drop-off plies 574B in pairs that (i) drop off,
pair-by-pair, in an
order from the first end 570A to the second end 570B, and/or (ii) are
equidistant
relative to the central portion 580 can additionally help to more gradually
and/or
smoothly transition from the first gage 572A at the first end 570A to the
second gage
572B at the second end 570B, and/or achieve a relatively greater degree of
symmetry
relative to, for instance, the arrangement of the tips 476 in Figure 4 (which
are
clustered near the outer surface 436).
[0161] Within examples, each drop-off ply 574B can have a ply angle,
relative to
a longitudinal axis of the composite structure 570 (e.g., the longitudinal
axis 348),
which is between approximately -30 degrees and +30 degrees. This can help to
achieve a desired stiffness with a relatively few (or minimal) quantity of
plies 574 and,
thus, reduce (or may minimize) a weight and/or cost of fabricating the
composite
structure 570. In an example, for each pair, the ply angle is approximately
the same
for the drop-off plies 574B of the pair. This can help to improve (or may
maximize) a
symmetry of the composite structure 570.
[0162] According to an additional or alternative aspect of the
monotonically-
outward pattern shown in Figure 5, the monotonically-outward pattern can
include,
along a direction from the first end 570A to the second end 570B, the tips 576
of the
first subset of the drop-off plies 574B alternating with the tips 576 of the
second subset
of the drop-off plies 574B. For example, in Figure 5, the tips 576 of the drop-
off plies
574B are in the following order from the first end 570A to the second end
570B: (i) the
tip 576 of the ply 5741=18 from the second subset, (ii) the tip 576 of the ply
5741=13 from
37
Date Recue/Date Received 2020-05-06
the first subset, (iii) the tip 576 of the ply 5741.20 from the second subset,
(iv) the tip
576 of the ply 5741.11 from the first subset, (v) the tip 576 of the ply
5741=22 from the
second subset, (vi) the tip 576 of the ply 5741=9 from the first subset, (vii)
the tip 576 of
the ply 5741=24 from the second subset, and (viii) the tip 576 of the ply
5741=7 from the
first subset. Alternating the respective positions of the tips 576 of the drop-
off plies
574B can additionally or alternatively help to help to more gradually and/or
smoothly
transition from the first gage 572A at the first end 570A to the second gage
572B at
the second end 570B.
[0163] As noted above, arranging the drop-off plies 574B such that the
tips 576 of
the drop-off plies 574B are staggered relative to each other can additionally
or
alternatively help to reduce (or may prevent) ply kinks and/or wrinkles,
reduce (or may
prevent) resin pockets, and/or increase (or may maximize) interlaminar
strength. As
an example, in Figure 5, the respective positions of the tips 576 of the drop-
off plies
574B can be staggered from the first end 570A to the second end 570B. By
"staggered", it is meant that the tips 576 of the drop-off plies 574B are each
at a
respective distance from the second end 570B, and the respective distances
between
the tips 576 and the second end 570B are all different from each other (i.e.,
the tips of
no two drop-off plies are equidistant from the second end 570B). Staggering
the tips
576 of the drop-off plies 574B can help to mitigate some or all of the
challenges
associated with a clustered arrangement of drop-off plies described above.
[0164] Also, as noted above, spacing the tips 576 relative to each
other by at least
one threshold distance can additionally or alternatively help to reduce (or
may prevent)
ply kinks and/or wrinkles, reduce (or may prevent) resin pockets, and/or
increase (or
may maximize) interlaminar strength. In an example, for each drop-off ply
574B, a
distance 584 between the tip 576 of the drop-off ply 574B and the tip 576 of
an
adjacent one of the drop-off plies 574B can be at least ten times greater than
the ply
thickness 582 of the drop-off ply 574B. In this example, for each drop-off ply
574B,
the adjacent one of the drop-off plies 574B is adjacent to the drop-off ply
574B in a
dimension extending between the outer surface 536 and the inner surface 534.
That
is, two of the drop-off plies 574B are adjacent to each other only if there is
not another
38
Date Recue/Date Received 2020-05-06
one of the drop-off plies 574B between the two of the drop-off plies 574B in
the
dimension extending between the outer surface 536 and the inner surface 534.
Thus,
for example, the ply 5741=19 is adjacent to the ply 5741=16 and the ply
5741.29, and non-
adjacent to the other drop-off plies 574B (i.e., plies 574=7, 9, 11, 13, 22,
24).
[0165] A representative one of the distances 584 is depicted in Figure 5
between
the tips 576 of the ply 5741=19 and the ply 574=16, which are adjacent to each
other. As
shown in Figure 5, the distance 584 between the tip 576 of the ply 5741=19 and
the tip
of the ply 5741=16 is at least ten times greater than the ply thickness 582 of
the ply
574=19. Similarly, in Figure 5, the tips 576 of the other adjacent ones of the
drop-off
plies 574B are separated by respective distances 584 that are at least ten
times
greater than the ply thickness 582. As described above, arranging the drop-off
plies
574B such that the tips 576 of adjacent ones of the drop-off plies 574B are
separated
by the distance 584 of at least ten times the ply thickness 582 can help to
reduce (or
may prevent) ply kinks and/or wrinkles, reduce (or may prevent) resin pockets,
and/or
.. increase (or may maximize) interlaminar strength.
[0166] Additionally or alternatively, for example, a distance 586
between non-
adjacent ones of the drop-off plies 574B can be at least three times greater
than the
ply thickness 582 of each drop-off ply 574B. A representative one of the
distances
586 is depicted in Figure 5 between the tips 576 of the ply 5741=19 and the
ply 5741=13,
which are non-adjacent to each other (e.g., because the ply 5741=16 is between
the ply
5741=19 and the ply 5741=13). As shown in Figure 5, the distance 586 between
the tip
576 of the ply 5741=19 and the tip of the ply 5741=13 is at least three times
greater than
the ply thickness 582 of the ply 574=19. Similarly, the tips 576 of the other
non-adjacent
ones of the drop-off plies 574B are separated by respective distances 586 that
are at
least three times greater than the ply thickness 582. As described above,
arranging
the drop-off plies 574B such that the tips 576 of non-adjacent ones of the
drop-off plies
574B are separated by the distance 584 of at least three times the ply
thickness 582
can help to reduce (or may prevent) ply kinks and/or wrinkles, reduce (or may
prevent)
resin pockets, and/or increase (or may maximize) interlaminar strength.
39
Date Recue/Date Received 2020-05-06
[0167] In Figure 5, the ply thickness 582 is the same for all of the
plies 574.
However, in another example, one or more of the plies 574 can have a different
ply
thickness than another one of the plies 574. In some implementations,
providing the
plies 574 with different ply thicknesses can help to provide relatively
greater flexibility
for achieving fabrication quality objectives.
[0168] Additionally, in Figure 5, the tips 576 of the drop-off plies
574B all have the
tapered shape. However, in another example, one or more of the tips 576 of the
drop-
off plies 574B can have the blunt-end shape shown in Figure 4. Although the
tapered
shape can be beneficial for at least the reasons described above, a composite
structure including the drop-off plies 574B having the tips 476 with the blunt-
end shape
in a pattern having one or more of the characteristics described above with
respect to
Figure Scan provide improvements over the composite structure 470 shown in
Figure
4. Similarly, a composite structure including the drop-off plies 474B arranged
in the
pattern shown in Figure 4, but with the tips 576 having the tapered shape can
provide
improvements over the composite structure 470 shown in Figure 4. Accordingly,
within examples, the drop-off plies 474B, 574B can the tips 576 with the
tapered shape
and/or the tips 476 with the blunt-end shape, and the drop-off plies 474B,
574B can
be arranged in a clustered pattern (as shown in Figure 4) and/or a pattern
having one
or more of the characteristics described above with respect to Figure 5.
[0169] As described, arranging the tips 576 of the drop-off plies 574B in a
pattern
having one or more of the characteristics described above can help to achieve
a
relatively greater degree of symmetry for the composite structure 570 (e.g.,
about the
central portion 580) relative to, for instance, the arrangement of the tips
476 in Figure
4. As used herein, the term "symmetry" is intended to be a relative term and
does not
mean exactly symmetric. For example, as shown in Figure 5, the composite
structure
570 includes 14 plies 574 between the central portion 580 and the outer
surface 536,
and 12 plies 574 between the central portion 580 and the inner surface 534.
However,
in the context of this disclosure, the composite structure 570 shown in Figure
5 has a
greater degree of symmetry relative to the composite structure 470 shown in
Figure
__ 4.
Date Recue/Date Received 2020-05-06
[0170]
Within examples, providing the composite structure 570 with a relatively
greater degree of symmetry about the central portion 580 can help to increase
(or may
maximize) interlaminar strength. Additionally or alternatively, providing the
composite
structure 570 with a relatively greater degree of symmetry about the central
portion
.. 580 can help to reduce (or may minimize) re-curing, tooling, material
handling costs,
and/or weight.
[0171]
As described above, Figure 5 shows the composite structure 570 with the
drop-off plies 574B arranged in an example pattern having one or more
characteristics
that can help to improve performance, reduce re-curing, reduce tooling, reduce
material handling costs, and/or reduce a weight of the composite structure
570. Other
example patterns having the one or more characteristics are also possible. For
instance, Figure 6 shows a composite structure 670 having a variable gage
according
to another example. As shown in Figure 6, the composite structure 670 includes
a
first end 670A having a first gage 672A and a second end 670B having a second
gage
672B, which is less than the first gage 672A of the first end 670A.
Additionally, as
shown in Figure 6, the composite structure 670 includes an inner surface 634
extending from the first end 670A to the second end 670B, and an outer surface
636
extending from the first end 670A to the second end 670B.
[0172]
As also shown in Figure 6, the composite structure 670 includes a plurality
.. of plies 674=1 to 674=n of composite material (hereinafter collectively
referred to as
"plies 674") arranged in a stack between the inner surface 634 and the outer
surface
636, where n is an integer value that is greater than or equal to two. In
Figure 6, the
composite structure 670 includes a total of 28 plies 674 (i.e., n=28).
However, in other
examples, the composite structure 670 can include a lesser quantity or a
greater
quantity of plies 674.
[0173]
In this arrangement, the first gage 672A of the first end 670A and the
second gage 672B of the second end 670B are respective thicknesses between the
inner surface 634 and the outer surface 636 at the first end 670A and the
second end
670B, respectively. Further, the first gage 672A is related to a quantity of
the plies
41
Date Recue/Date Received 2020-05-06
674 at the first end 670A and the second gage 672B is related to a quantity of
the
plies 674 at the second end 670B. For instance, in Figure 6, the quantity of
the plies
674 at the first end 670A is greater than the quantity of the plies 674 at the
second
end 670B such that the first gage 672A is greater than the second gage 672B.
[0174] As described above, the variable gage of the composite structure 670
results from the plies 674 of composite material including a plurality of
continuous plies
674A and a plurality of drop-off plies 674B arranged in the stack between the
inner
surface 634 and the outer surface 636. In Figure 6, each continuous ply 674A
extends
from the first end 670A to the second end 670B. Whereas, each drop-off ply
674B
includes a tip 676, and each drop-off ply 674B extends from the first end 670A
to a
respective position of the tip 676 of the drop-off ply 674B between the first
end 670A
and the second end 670B.
[0175] For clarity of illustration, in Figure 6, a representative
subset of the
continuous plies 674A are labeled with reference number 674A and a
representative
subset of the drop-off plies 674B are labeled with reference number 674B.
However,
each of the plies 674 that extends entirely from the first end 670A to the
second end
670B is one of the continuous plies 674A, and each of the plies 674 that
terminates
between the first end 670A and the second end 670B is one of the drop-off
plies 674B.
Specifically, in Figure 6, the plies 674=1-4,6,8õ10,12,14,15,17,19,21,23,25-28
are the continuous
plies 674A, and the plies 6741=5,7,9,11,13,16,18,20,2224 are the drop-off
plies 674B.
[0176] As shown in Figure 6, the tip 676 of each drop-off ply 674B has
the tapered
shape described above with respect to the tips 576 shown in Figure 5. As such,
the
tips 676 having the tapered shape can reduce (or may minimize) resin pockets
at the
tips 676 of the drop-off plies 674B, which can help to improve (or may
maximize)
interlaminar strength of the composite structure 670. However, in other
examples,
one or more of the drop-off plies 674B can have the blunt-end shape shown in
Figure
4.
[0177] As noted above, the load bearing performance of the composite
structure
670 can be enhanced, additionally or alternatively, based on the pattern in
which the
42
Date Recue/Date Received 2020-05-06
plies 6741 are arranged in the composite structure 670. For example, in Figure
6, the
drop-off plies 574B can be separated from each other by at least one of the
continuous
plies 674A. For instance, each drop-off ply 674B can be sandwiched between and
abut against a respective two continuous plies 674A of the plurality of
continuous plies
674A. By separating the drop-off plies 674B from each other and/or sandwiching
the
drop-off plies 674B between the continuous plies 674A, the drop-off plies 674B
can
be more uniformly distributed between the inner surface 634 and the outer
surface
636 (as compared to the clustered arrangement of the drop-off plies 474B shown
in
Figure 4). This can help to reduce (or may prevent) ply kinks and/or wrinkles,
reduce
(or may prevent) resin pockets, and/or increase (or may maximize) interlaminar
strength of the composite structure 670.
[0178] Within examples, the pattern of the tips 676 of the drop-off
plies 574B can
additionally or alternatively include one or more of the following
characteristics: (i) an
arrangement of the tips 676 in a first half of the composite structure 670 in
a pattern
that mirrors a pattern of the tips 676 in a second half of the composite
structure 670,
(ii) a staggered arrangement of the tips 676 relative to each other, and/or
(iii) spacing
the tips 676 relative to each other by at least one threshold distance. As
described
above, each of these characteristics alone or in combination can contribute to
arranging the drop-off plies 674B in a pattern that can reduce (or may
prevent) ply
kinks and/or wrinkles, reduce (or may prevent) resin pockets, and/or increase
(or may
maximize) interlaminar strength.
[0179] Figure 6 shows the tips 676 arranged in mirror patterns relative
to a central
portion 680 of the composite structure 670 according to another example. The
central
portion 680 can include one or more of the plies 674 that provide a frame of
reference
.. for characterizing patterns of the tips 676 of the drop-off plies 674B on
opposing sides
of the central portion 680. As noted above, in general, the central portion
680 (i) is
between the inner surface 634 and the outer surface 636 and (ii) extends from
the first
end 670A to the second end 670B.
43
Date Recue/Date Received 2020-05-06
[0180] In Figure 6, the central portion 680 can include the plies
6741=14,15. Thus, in
Figure 6, the central portion 680 can include two continuous plies 674A.
However, in
another example, the central portion 680 can include two drop-off plies 674B
and at
least one continuous ply 674A. In yet another example, the central portion 680
can
consist of only a single drop-off ply 674B. In another example, the central
portion 680
can consist of at least one continuous ply 674A and omit the drop-off plies
674B. More
generally, the central portion 680 can include one or more of the continuous
plies 674A
and/or one or more of the drop-off plies 674B.
[0181] Also, as shown in Figure 6, the tips 676 of the drop-off plies
674B can be
arranged in mirror patterns relative to the central portion 680. For instance,
a first
subset of the drop-off plies 674B can be between the outer surface 636 and the
central
portion 680, and a second subset of the drop-off plies 674B can be between the
central
portion 680 and the inner surface 634. In this arrangement, the tips 676 of
the first
subset of the drop-off plies 674B are arranged in a pattern that substantially
mirrors a
pattern of the tips 676 of the second subset of the drop-off plies 674B. In
other words,
with reference to the central portion 680, the respective positions of the
tips 676 of the
first subset of the drop-off plies 674B are (i) reversely and (ii) similarly
(or identically)
arranged in comparison to the respective positions of the tips 676 of the
second subset
of the drop-off plies 674B.
[0182] For example, in Figure 6, the central portion 680 can include the
plies
6741=14,15, the first subset of the drop-off plies 674B can include the plies
6741=5, 7, 9, 11,
13, and the second subset of the drop-off plies 674B can include the plies
674=16,18,20,
22, 24. As shown in Figure 6, the pattern of the tips 676 of the first subset
of the drop-
off plies 674B substantially mirrors the pattern of the tips 676 of the second
subset of
the drop-off plies 674B. For instance, with reference to the central portion
680, the
respective positions of the tips 676 of the first subset are reversely and
similarly
arranged in comparison to the respective positions of the tips 676 of the
second
subset.
44
Date Recue/Date Received 2020-05-06
[0183] As described above, Figure 5 shows the pattern of the tips 576
of the drop-
off plies 574B as a monotonically-outward pattern. Figure 6 shows the tips 676
of the
drop-off plies 674B arranged in a monotonically-inward pattern, according to
an
example. In a first order of the first subset of the drop-off plies 674B from
the outer
surface 636 toward the central portion 680, with each successive drop-off ply
674B in
the first order, a relative distance between the tip 676 of the drop-off ply
674B and the
second end 670B decreases. Also, in a second order of the second subset of the
drop-off plies 674B from the inner surface 634 toward the central portion 680,
with
each successive drop-off ply 674B in the second order, a relative distance
between
the tip 676 of the drop-off ply 674B and the second end 670B decreases.
[0184] As such, in Figure 6, (i) the tip 676 of the ply 5741=5 is at a
first distance from
the second end 670B, (ii) the tip 676 of the ply 6741=7 is at a second
distance from the
second end 670B, which is less than the first distance, (iii) the tip 676 of
the ply 674=9
is at a third distance from the second end 670B, which is less than the second
distance, (iv) the tip 676 of the ply 6741.11 is at a fourth distance from the
second end
670B, which is less than the third distance, and (v) the tip 676 of the ply
6741=13 is at a
fifth distance from the second end 670B, which is less than the fourth
distance. Also,
in Figure 6, (vi) the tip 676 of the ply 6741=24 is at a sixth distance from
the second end
670B, (vii) the tip 676 of the ply 6741=22 is at a seventh distance from the
second end
670B, which is less than the sixth distance, (viii) the tip 676 of the ply
6741.20 is at an
eighth distance from the second end 670B, which is less than the seventh
distance,
(ix) the tip 676 of the ply 6741=18 is at a ninth distance from the second end
670B, which
is less than the eighth distance, and (x) the tip 676 of the ply 6741=16 is at
a tenth
distance from the second end 670B, which is less than the ninth distance.
[0185] Accordingly, in the monotonically-inward pattern of the tips 676
shown in
Figure 6, the tips 676 of the drop-off plies 674B generally appear to be
converge
inward from the outer surface 636 and the inner surface 634 toward the central
portion
680 in a direction from the first end 670A to the second end 670B. The
monotonically-
inward pattern of the tips 676 can help to more gradually and/or smoothly
transition
from the first gage 672A at the first end 670A to the second gage 672B at the
second
Date Recue/Date Received 2020-05-06
end 670B. Additionally, for example, the monotonically-inward pattern of the
tips 676
can help to achieve a relatively greater degree of symmetry relative to, for
instance,
the arrangement of the tips 476 in Figure 4 (which are clustered near the
outer surface
436).
[0186] According to an additional or alternative aspect of the
monotonically-inward
pattern shown in Figure 6, the drop-off plies 674B can be arranged in a
plurality of
pairs of drop-off plies 674B that define an order in which the drop-off plies
674B drop
off in a direction from the first end 670A toward the second end 670B (i.e.,
an order of
the respective positions of the tips 676 in the direction from the first end
670A toward
the second end 670B). In particular, each pair of drop-off plies 674B can
include a
respective one drop-off ply 674B of the first subset and a respective one drop-
off ply
674B of the second subset.
[0187] For example, in Figure 6, a first pair includes the plies
6741=5,24, a second
pair includes the plies 6741=7,22, a third pair includes the plies 6741=9, 20,
a fourth pair
includes the plies 674=11,18, and a fifth pair includes the plies 6741=13,16.
As shown in
Figure 6, in the direction from the first end 670A to the second end 670B, the
drop-off
plies 674B drop off in an order from the first pair to the fifth pair. In
other words, the
tips 676 of the first pair of the drop-off plies 674B are closest to the first
end 670A, the
tips 676 of the second pair of the drop-off plies 674B are second closest to
the first
end 670A, the tips 676 of the third pair of the drop-off plies 674B are third
closest to
the first end 670A, the tips 676 of the fourth pair of the drop-off plies 674B
are second
farthest from the first end 670A, and the tips 676 of the fifth pair of the
drop-off plies
674B are farthest from the first end 670A.
[0188] Additionally, for example, for each pair of drop-off plies 674B,
the
respective one drop-off ply 674B of the first subset and the respective one
drop-off ply
674B of the second subset can be equidistant from the central portion 680 in a
dimension between the outer surface 636 and the inner surface 634. For
instance, as
shown in Figure 6, the first pair of the drop-off plies 674B are each spaced
from the
central portion 680 by a distance equal to eight times a ply thickness 682 of
a single
46
Date Recue/Date Received 2020-05-06
ply 674, the second pair of the drop-off plies 674B are each spaced from the
central
portion 680 by a distance equal to six times the ply thickness 682, the third
pair of the
drop-off plies 674B are each spaced from the central portion 680 by a distance
equal
to four times the ply thickness 682, the fourth pair of the drop-off plies
674B are each
spaced from the central portion 680 by a distance equal to two times the ply
thickness
682, and the fifth pair of the drop-off plies 674B are each immediately
adjacent to and
abut against the central portion 680.
[0189] Arranging the drop-off plies 674B in pairs that (i) drop off,
pair-by-pair, in an
order from the first end 670A to the second end 670B, and/or (ii) are
equidistant
relative to the central portion 680 can additionally help to more gradually
and/or
smoothly transition from the first gage 672A at the first end 670A to the
second gage
672B at the second end 670B, and/or achieve a relatively greater degree of
symmetry
relative to, for instance, the arrangement of the tips 476 in Figure 4 (which
are
clustered near the outer surface 436).
[0190] According to an additional or alternative aspect of the
monotonically-inward
pattern shown in Figure 6, the monotonically-inward pattern can include, along
a
direction from the first end 670A to the second end 670B, the tips 676 of the
first subset
of the drop-off plies 674B alternating with the tips 676 of the second subset
of the
drop-off plies 674B. For example, in Figure 6, the tips 676 of the drop-off
plies 674B
are in the following order from the first end 670A to the second end 670B: (i)
the tip
676 of the ply 674=5 from the first subset, (ii) the tip 676 of the ply 674=24
from the
second subset, (iii) the tip 676 of the ply 674=7 from the first subset, (iv)
the tip 676 of
the ply 674=22 from the second subset, (v) the tip 676 of the ply 674=9 from
the first
subset, (vi) the tip 676 of the ply 674=20 from the second subset, (vii) the
tip 676 of the
ply 674=ii from the first subset, (viii) the tip 676 of the ply 674=15 from
the second
subset, (ix) the tip 676 of the ply 674=13 from the first subset, and (x) the
tip 676 of the
ply 674=16 from the second subset. Alternating the respective positions of the
tips 676
of the drop-off plies 674B can additionally or alternatively help to help to
more
gradually and/or smoothly transition from the first gage 672A at the first end
670A to
the second gage 672B at the second end 670B.
47
Date Recue/Date Received 2020-05-06
[0191] As noted above, arranging the drop-off plies 674B such that the
tips 676 of
the drop-off plies 674B are staggered relative to each other can additionally
or
alternatively help to reduce (or may prevent) ply kinks and/or wrinkles,
reduce (or may
prevent) resin pockets, and/or increase (or may maximize) interlaminar
strength. As
an example, in Figure 6, the respective positions of the tips 676 of the drop-
off plies
674B can be staggered from the first end 670A to the second end 670B. By
"staggered", it is meant that the tips 676 of the drop-off plies 674B are each
at a
respective distance from the second end 670B, and the respective distances
between
the tips 676 and the second end 670B are all different from each other (i.e.,
the tips of
-- no two drop-off plies are equidistant from the second end 670B). Staggering
the tips
676 of the drop-off plies 674B can help to mitigate some or all of the
challenges
associated with a clustered arrangement of drop-off plies described above.
[0192] Also, as noted above, spacing the tips 676 relative to each
other by at least
one threshold distance can additionally or alternatively help to reduce (or
may prevent)
ply kinks and/or wrinkles, reduce (or may prevent) resin pockets, and/or
increase (or
may maximize) interlaminar strength. In an example, for each drop-off ply
674B, a
distance 684 between the tip 676 of the drop-off ply 674B and the tip 676 of
an
adjacent one of the drop-off plies 674B can be at least ten times greater than
the ply
thickness 682 of the drop-off ply 674B. In this example, for each drop-off ply
674B,
the adjacent one of the drop-off plies 674B is adjacent to the drop-off ply
674B in a
dimension extending between the outer surface 636 and the inner surface 634.
For
instance, as described above, two of the drop-off plies 674B are adjacent to
each other
only if there is not another one of the drop-off plies 674B between the two of
the drop-
off plies 674B in the dimension extending between the outer surface 636 and
the inner
surface 634. Thus, for example, the ply 6741=7 is adjacent to the ply 6741=5
and the ply
6741=9, and non-adjacent to the other drop-off plies 674B (i.e., plies
5741=11,13,16, 18, 20,
22, 24).
[0193] A representative one of the distances 684 is depicted in Figure
6 between
the tips 676 of the ply 6741=7 and the ply 6741=5, which are adjacent to each
other. As
shown in Figure 6, the distance 684 between the tip 676 of the ply 6741=7 and
the tip
48
Date Recue/Date Received 2020-05-06
of the ply 674=5 is at least ten times greater than the ply thickness 682 of
the ply 674=7.
Similarly, in Figure 6, the tips 676 of the other adjacent ones of the drop-
off plies 674B
are separated by respective distances 684 that are at least ten times greater
than the
ply thickness 682. As described above, arranging the drop-off plies 674B such
that
the tips 676 of adjacent ones of the drop-off plies 674B are separated by the
distance
684 of at least ten times the ply thickness 682 can help to reduce (or may
prevent) ply
kinks and/or wrinkles, reduce (or may prevent) resin pockets, and/or increase
(or may
maximize) interlaminar strength.
[0194] Additionally or alternatively, for example, a distance 686
between non-
adjacent ones of the drop-off plies 674B can be at least three times greater
than the
ply thickness 682 of each drop-off ply 674B. A representative one of the
distances
686 is depicted in Figure 6 between the tips 676 of the ply 674=7 and the ply
674=22,
which are non-adjacent to each other (e.g., because the plies 674=9, 11, 13,
16, 18,20 are
between the ply 674=7 and the ply 674=22). As shown in Figure 6, the distance
686
between the tip 676 of the ply 674=7 and the tip of the ply 674=22 is at least
three times
greater than the ply thickness 682 of the ply 674=7. Similarly, the tips 676
of the other
non-adjacent ones of the drop-off plies 674B are separated by respective
distances
686 that are at least three times greater than the ply thickness 682. As
described
above, arranging the drop-off plies 674B such that the tips 676 of non-
adjacent ones
of the drop-off plies 674B are separated by the distance 684 of at least three
times the
ply thickness 682 can help to reduce (or may prevent) ply kinks and/or
wrinkles,
reduce (or may prevent) resin pockets, and/or increase (or may maximize)
interlaminar
strength.
[0195] In Figure 6, the ply thickness 682 is the same for all of the
plies 674.
However, in another example, one or more of the plies 674 can have a different
ply
thickness than another one of the plies 674. In some implementations,
providing the
plies 674 with different ply thicknesses can help to provide relatively
greater flexibility
for achieving fabrication quality objectives.
49
Date Recue/Date Received 2020-05-06
[0196] Additionally, in Figure 6, the tips 676 of the drop-off plies
674B all have the
tapered shape. However, in another example, one or more of the tips 676 of the
drop-
off plies 674B can have the blunt-end shape of the tips 476 shown in Figure 4.
Although the tapered shape can be beneficial for at least the reasons
described above,
a composite structure including the drop-off plies 674B having the tips 476
with the
blunt-end shape in a pattern having one or more of the characteristics
described above
with respect to Figure 6 can provide improvements over the composite structure
470
shown in Figure 4.
[0197] As described above, within examples, the lower corner portion
352, the
upper corner portion 354, the second upper corner portion 358, and/or the
second
lower corner portion 356 can include the composite structures 470, 570, 670
described
above with respect to Figures 4-6. In Figures 4-6, the first end 470A, 570A,
670A has
the first gage 472A, 572A, 672A, which is greater than the second gage 472B,
572B,
672B at the second end 470B, 570B, 670B. Accordingly, depending on the
respective
gages of the portions of the composite stringer 320 on opposing sides of the
composite
structure 470, 570, 670, (i) the first end 470A, 570A, 670A can be located at
a first
interface between the composite structure 470, 570, 670 and any one of the
skin
flange 324, the web 328, the top flange 326, the second web 332, or the second
skin
flange 330, and (ii) the second end 470B, 570B, 670B can be located at a
second
interface between the composite structure 470, 570, 670 and another one of the
skin
flange 324, the web 328, the top flange 326, the second web 332, or the second
skin
flange 330.
[0198] As described above, the composite stringer 320 is coupled to the
support
structure 322, which includes the skin flange, in Figures 3A-3B. However, as
described above, the support structure 322 can additionally include a base
charge in
some examples. Figure 7 depicts a composite stringer assembly 701 including
the
composite stringer 320 coupled to a support structure 722, according to
another
example. The composite stringer assembly 701 shown in Figure 7 is identical to
the
composite stringer assembly 701 shown in Figures 3A-3B, except the support
structure 722 includes a base charge 788 and the skin 323 of the vehicle.
Date Recue/Date Received 2020-05-06
[0199] The base charge 788 is configured to couple the skin flange 324
and the
second skin flange 330 to the skin 323 of the vehicle. Within examples, the
base
charge 788 can include one or more plies of composite material that can help
support
and cushion the composite stringer 320 on the skin 323. In Figure 7, the base
charge
788 extends under an entire surface area of inner surface 334 at the skin
flange 324
and an entire surface area of the inner surface 334 at the second skin flange
330.
Also, in Figure 7, the base charge 788 extends continuously across a space
between
the skin flange 324 and the second skin flange 330. However, in other
examples, the
base charge 788 can include a plurality of base charges 788. For instance, the
base
charge 788 can include one base charge 788 at the skin flange 324 and another
base
charge 788 at the second skin flange 330, and the base charges 788 can be
separated
by a gap (e.g., the skin 723 can be exposed at the gap).
[0200] As shown in Figure 7, the base charge 788 can have a sixth gage
790,
which is approximately equal to or less than the first gage 338 of the skin
flange 324
and/or the fourth gage 344 of the second skin flange 330. This can help to
provide
the base charge 788 with a stiffness that is approximately equal to a
stiffness of the
skin flange 324 and/or a stiffness of the second skin flange 330. Providing
the base
charge 788, the skin flange 324, and/or the second skin flange 330 with
approximately
the same stiffness can help to enhance (or may maximize) energy absorption due
to
an impact and/or a load at an interface between (i) the base charge 788 and
(ii) the
skin flange 324 or the second skin flange 330. In this way, a bond at the
interface
between (i) the base charge 788 and (ii) the skin flange 324 and/or the second
skin
flange 330.
[0201] Also, within examples, at least one of the skin flange 324, the
second skin
flange 330, or the base charge 788 can have a stiffness that is approximately
equal to
a stiffness of the skin 323 of the vehicle. As described above, this can help
to enhance
(or may maximize) energy absorption due to an impact and/or a load at an
interfaces
between the skin 323 of the vehicle, the base charge 788, the skin flange 324,
and/or
the second skin flange 330 (and, thus, mitigate (or may prevent) delamination
between
the composite stringer 320, the base charge 788, and the skin 323).
51
Date Recue/Date Received 2020-05-06
[0202] As described above with respect to Figures 3A-3B and 7, the
lower corner
portion 352 and/or the second lower corner portion 356 can be curved to
transition
from the skin flange 324 to the web 328 and/or the second skin flange 330 to
the
second web 332, respectively. As shown in Figures 3A-3B and 7, the curvature
of the
lower corner portion 352 and/or the second lower corner portion 356 can form a
void
region between (i) the support structure 322, 722 and (ii) the inner surface
334 at the
lower corner portion 352 and/or at the second lower corner portion 356. Such
void
region(s) may be referred to as "radius filler regions" or "noodle regions".
For some
conventional composite stringer assemblies, the radius filler regions may be
prone to
cracking. To strengthen and/or improve a durability of the composite stringer
assemblies, a radius filler formed of a composite material (e.g., CFRP) may be
positioned in the radius filler region.
[0203] Within examples, by providing the top flange 326 with the second
gage 340,
which is greater than the first gage 338 of the skin flange 324, the third
gage 342 of
the web 328, the fourth gage 344 of the second skin flange 330, and/or the
fifth gage
346 of the second web 332, the composite stringer assemblies 301, 701 can omit
a
radius filler and/or include a radius filler that is relatively smaller than
the radius fillers
of conventional composite stringer assemblies (i.e., in which the skin flange
324, the
web 328, the top flange 326, the second web 332, and the second skin flange
330 all
have the same gage). This is, at least in part, due to the performance
improvements
achieved by the composite stringer assemblies 301, 701 described above (e.g.,
due
to improved strength-to-weight ratios and/or improved stiffness compatibility
allowing
for greater flexibility at an interface between the composite stringer 320 and
the
support structure 322, 722 as described above).
[0204] Additionally, a size of the radius filler region can be related to a
gage of the
lower corner portion 352 or a gage of the second lower corner portion 356
(which are
related to the first gage 338, the third gage 342, the fourth gage 344, and/or
the fifth
gage 346). Within examples, a size of the radius filler can be reduced (or may
be
minimized) when the first gage 338 of the skin flange 324 is approximately
equal to
52
Date Recue/Date Received 2020-05-06
the third gage of the web 328 and/or the fourth gage 344 of the second skin
flange
330 is approximately equal to the second web 332.
[0205] In some implementations in which the composite stringer assembly
301,
701 includes a radius filler, the composite stringer assembly 301, 701 can
include one
or more of the features described below with respect to Figures 8A-8B to
achieve one
or more improvements relative to conventional composite stringer assemblies.
In
particular, within examples, the composite stringer 320 and/or a radius filler
can
include one or more surfaces defined by constant radii of curvature, which can
help to
reduce a size of the radius filler, improve strength of the composite stringer
assembly
301, 701, simplify tooling requirements, and/or reduce variability among a
plurality of
composite stringers 320.
[0206] Referring now to Figures 8A-8B, a composite stringer assembly
801 is
illustrated according to an example. In particular, Figure 8A depicts a side
view of the
composite stringer assembly 801, and Figure 8B depicts a perspective view of
the
composite stringer assembly 801.
[0207] As shown in Figures 8A-8B, the composite stringer assembly 801
includes
a composite stringer 820 and a radius filler 890. The composite stringer
assembly
801 can also include a support structure 822 coupled to the composite stringer
820
and/or the radius filler 890. In Figures 8A-8B, the support structure 822
includes a
skin 823 of a vehicle and a base charge 888. However, in another example, the
support structure 822 can include the skin 823 of the vehicle and omit the
base charge
888. More generally, as described above, the support structure 822 can include
at
least one of the skin 823 of the vehicle or the base charge 888.
[0208] As shown in Figures 8A-8B, the composite stringer 820 includes a
skin
flange 824 that is configured to be coupled to the support structure 822, a
web 828, a
lower corner portion 852 extending from the skin flange 824 to the web 828.
The
composite stringer 820 also includes (i) an inner surface 834 extending along
the skin
flange 824, the lower corner portion 852, and the web 828, and (ii) an outer
surface
836 extending along the skin flange 824, the lower corner portion 852, and the
web
53
Date Recue/Date Received 2020-05-06
828. The inner surface 834 faces the support structure 822 when the skin
flange 824
is coupled to the support structure 822, and the outer surface 836 faces away
from
the support structure 822 when the skin flange 824 is coupled to the support
structure
822.
[0209] In Figures 8A-8B, the composite stringer 820 is in the form of a hat-
shaped
stringer. As such, the composite stringer 820 can also include a top flange
826, an
upper corner portion 854 extending from the web 828 to the top flange 826. The
web
828 and the upper corner portion 854 can extend from a first side 826A of the
top
flange 826. Additionally, as a hat-shaped stringer, the composite stringer 820
can
further include a second skin flange 830 configured to be coupled to the
support
structure 822 and a second web 832 extending between the second skin flange
830
and a second side 826B of the top flange 826. The composite stringer 820 can
also
include a second lower corner portion 856 extending form the second skin
flange 830
to the second web 832, and a second upper corner portion 858 extending from
the
second web 832 to the top flange 826.
[0210] Although the composite stringer 820 shown in Figures 8A-8B is a
hat-
shaped stringer, as described below with respect to Figures 12-15, the
principles
described with respect to Figures 8A-8B can extend to apply to other types of
composite stringers (e.g., J-shaped stringers, C-shaped stringers, l-shaped
stringers,
and/or Z-shaped stringers). In particular, the concepts and principles
described herein
can be applied to any type of composite stringer that includes at least the
skin flange
824, the web 828, and the lower corner portion 852 extending from the skin
flange 824
to the web 828.
[0211] Within examples, the skin flange 824, the web 828, the top
flange 826, the
second web 832, and/or the second skin flange 830 can have any or all of the
features
described above with respect to the composite stringer 320 shown in Figures 3A-
3B
and 7. Similarly, the lower corner portion 852, the upper corner portion 854,
the
second lower corner portion 856, and/or the second upper corner portion 858
can
have any of the features described above with respect to the composite
stringer 320
54
Date Recue/Date Received 2020-05-06
shown in Figures 3A-3B and 7, and/or the composite structures 470, 570, 670
shown
in Figures 4-6.
[0212] For instance, within examples, the skin flange 824, the web 828,
the top
flange 826, the second web 832, the second skin flange 830, the lower corner
portion
852, the upper corner portion 854, the second lower corner portion 856, and/or
the
second upper corner portion 858 can include a plurality of plies of composite
material.
Additionally, for instance, the skin flange 824 can have a first gage 838, the
top flange
826 can have a second gage 840, the web 828 can have a third gage 842, the
second
skin flange 830 can have a fourth gage 844, and/or the second web 832 can have
a
fifth gage 846. Within examples, these respective gages 838, 840, 842, 844,
846 can
be configured as described above.
[0213] More particularly, in some examples, the second gage 840 of the
top flange
826 can be greater than the first gage 838 of the skin flange 824 and the
third gage
842 of the web 828, and/or the second gage 840 of the top flange 826 can be
greater
than the fourth gage 844 of the second skin flange 830 and the fifth gage 846
of the
second web 832. As described above, this can help to increase a strength-to-
weight
ratio of the composite stringer 820. Additionally or alternatively, it can
help to provide
greater strength (and/or greater stiffness) at the top flange 826 to enhance
load
transfer performance, while providing greater flexibility at an interface
between the
composite stringer 820 and the support structure 822.
[0214] Also, in some examples, the first gage 838 of the skin flange
824 can be
approximately equal to the third gage 842 of the web 828, and/or the fourth
gage 844
of the second skin flange 830 can be approximately equal to the fifth gage 846
of the
second web 832. In an implementation in which the first gage 838 of the skin
flange
824 is approximately equal to the third gage 842 of the web 828, the lower
corner
portion 852 can have a gage that is also approximately equal to the first gage
838 and
the third gage 842. Similarly, in an implementation in which the fourth gage
844 of the
second skin flange 830 is approximately equal to the fifth gage 846 of the
second web
832, the second lower corner portion 856 can have a gage that is also
approximately
Date Recue/Date Received 2020-05-06
equal to the fourth gage 844 and the fifth gage 846. As described above, this
configuration of the skin flange 824, the lower corner portion 852, the web
828, the
second skin flange 830, the second lower corner portion 856, and/or the second
web
832 can help to reduce (or may minimize) a size of the radius filler 890.
[0215] Although Figures 8A-8B depict the composite stringer 820 having the
respective gages 838, 840, 842, 844, 846 described above, the composite
stringer
820 can include different respective gages 838, 840, 842, 844, 846 in other
examples.
For instance, within examples, one or more of the constant radii of curvature
features
described below can be applied to composite stringers 820 in which the second
gage
840 of the top flange 826 is approximately equal to the first gage 838 of the
skin flange
824 and the third gage 842 of the web 828, and/or the second gage 840 of the
top
flange 826 is approximately equal to the third gage 842 of the second skin
flange 930
and the fifth gage 846 of the second web 832. Additionally, for example, in an
implementation in which the first gage 838 differs from the third gage 842
and/or the
fourth gage 844 differs from the fifth gage 846, the lower corner portion 852
and/or the
second lower corner portion 856 can have a variable gage to transition between
the
different gages as described above with respect to Figures 4-6.
[0216] Additionally, as described above, the lower corner portion 852
can provide
a transition section between the skin flange 824 and the web 828, whereas the
upper
corner portion 854 can provide a transition section between the web 828 and
the top
flange 826. Similarly, the second lower corner portion 856 can provide a
transition
section between the second skin flange 830 and the second web 832, whereas the
second upper corner portion 858 can provide a transition section between the
second
web 832 and the top flange 826.
[0217] For example, in Figures 3A-3B, the skin flange 824, the web 828, the
top
flange 826, the second web 832, and the second skin flange 830 can be planar
portions of the composite stringer 820 that each extend in a respective plane
in space.
For instance, Figures 8A-8B indicate a coordinate system 860, and Figure 8A
depicts
the composite stringer assembly 801 in an X-Y plane of the coordinate system
860.
56
Date Recue/Date Received 2020-05-06
As shown in Figures 8A-8B, the skin flange 824 can be a planar portion of the
composite stringer 820 extending in a first plane parallel to an X-Z plane of
the
coordinate system 860, the web 828 can be a planar portion of the composite
stringer
820 extending in a second plane is transverse to the X-Z plane of the
coordinate
system 860, the second web 832 can be a planar portion of the composite
stringer
820 extending in a third plane is transverse to the X-Z plane of the
coordinate system
860, and the top flange 826 can be a planar portion of the composite stringer
820
extending in a fourth plane that is parallel to the X-Z plane of the
coordinate system
860. In this arrangement, the second plane and the third plane are transverse
to the
first plane and the fourth plane.
[0218] Accordingly, the respective planes in which the skin flange 824,
the web
828, the top flange 826, the second web 832, and the second skin flange 830
extend
can be different from each other. As such, the lower corner portion 852, the
upper
corner portion 854, the second lower corner portion 856, and/or the second
upper
corner portion 858 can include a curved shape that facilitates transitioning
from one
plane to another.
[0219] As shown in Figure 8A, at the lower corner portion 852, the
outer surface
836 is defined by a first radius of curvature R1. In Figures 8A-8B, the first
radius of
curvature R1 is substantially constant between the skin flange 824 and the web
828.
Additionally, as shown in Figure 8A, at the second lower corner portion 856,
the outer
surface 836 is defined by the first radius of curvature R1. In Figures 8A-8B,
the first
radius of curvature R1 is substantially constant between the second skin
flange 830
and the second web 832. Forming the lower corner portion 852 and/or the second
lower corner portion 856 with the constant first radius of curvature R1 can
help to
.. reduce a size of the radius filler 890, improve strength of the composite
stringer
assembly 801, simplify tooling requirements, and/or reduce variability among a
plurality of composite stringers 820.
[0220] As shown in Figures 8A-8B, the radius filler 890 can be coupled
to the
composite stringer 820 and the support structure 822 at a radius filler region
between
57
Date Recue/Date Received 2020-05-06
the lower corner portion 852 and the support structure 822 and/or a radius
filler region
between the second lower corner portion 856 and the support structure 822.
Within
examples, the radius filler 890 can be made from a composite material (e.g.,
CFRP)
and/or an adhesive/epoxy material. The radius fillers 890 can help to
strengthen
and/or improve a durability of the composite stringer assembly 801 at the
lower corner
portion 852 and/or the second lower corner portion 856.
[0221] Also, as shown in Figures 8A-8B, the radius filler 890 includes
a first surface
890A coupled to the inner surface 834 at the lower corner portion 852, a
second
surface 890B configured to couple to the support structure 822, and a third
surface
890C extending between the first surface 890A and the second surface 890B. In
an
example, the second surface 890B of the radius filler 890 can be configured to
couple
to the support structure 822 by having a shape that generally conforms to a
shape of
the support structure 822.
[0222] In Figures 8A-8B, the first surface 890A of the radius filler
890 is defined by
a second radius of curvature R2, and the second radius of curvature R2 is
substantially
constant between the second surface 890B and the third surface 890C. This can
also
help to reduce a size of the radius filler 890, improve strength of the
composite stringer
assembly 801, simplify tooling requirements, and/or reduce variability among a
plurality of composite stringers 820.
[0223] In Figures 8A-8B, at the lower corner portion 852, the inner surface
834 is
also defined by the second radius of curvature R2. Forming the first surface
890A of
the radius filler 890 and the inner surface 834 at the lower corner portion
852 to be
defined the second radius of curvature R2 can help to strengthen the coupling
between the radius filler 890 and the inner surface 834 at the lower corner
portion 852
and/or simplify tooling requirements for forming the composite stringer
assembly 801.
[0224] As shown in Figure 8A, the second radius of curvature R2 can be
approximately equal to a sum of the first radius of curvature R1 and the first
gage 838
of the skin flange 824. In one example, the first radius of curvature R1 can
be between
approximately 3.0 mm and approximately 130.0 mm, the first gage 838 can be
58
Date Recue/Date Received 2020-05-06
between approximately 0.6 mm and approximately 12.0 mm, and thus the second
radius of curvature R2 can be between approximately 3.6 mm and approximately
142.0 mm. In another example, the first radius of curvature R1 can be between
approximately 4.0 mm and approximately 100.0 mm, the first gage 838 can be
between approximately 1.0 mm and approximately 8.0 mm, and thus the second
radius of curvature R2 can be between approximately 5.0 mm and approximately
108.0 mm. Within examples, reducing the first radius of curvature R1 can help
to
reduce a cost of tooling and/or a cost of fabrication for the composite
stringer 820.
[0225] Also, as shown in Figure 8A, the third surface 890C of the
radius filler 890
can be defined by a third radius of curvature R3, and the third radius of
curvature R3
can be substantially constant between the first surface 890A and the second
surface
890B. This can additionally or alternatively help to reduce (or may minimize)
a size of
the radius filler 890, improve strength of the composite stringer assembly
801, and/or
simplify tooling requirements for forming the composite stringer assembly 801.
In
some examples, the third radius of curvature R3 of the third surface 890C can
be
approximately equal to second radius of curvature R2. This can further help to
simplify
tooling requirements for forming the composite stringer assembly 801. However,
in
other examples, the third radius of curvature R3 of the third surface 890C can
be
different than the second radius of curvature R2.
[0226] As shown in Figure 8B, the composite stringer 820 has a longitudinal
axis
848, and the composite stringer 820 has a length 849 between a first end 850A
of the
composite stringer 820 and a second end 850B of the composite stringer 820. In
Figure 8B, along the longitudinal axis 848, the first radius of curvature R1
is
substantially constant over the length 849 of the composite stringer 820. This
can
also help to reduce a size of the radius filler 890, improve strength of the
composite
stringer assembly 801, simplify tooling requirements, and/or reduce
variability among
a plurality of composite stringers 820.
[0227] Similarly, along the longitudinal axis 848, the second radius of
curvature R2
of the first surface 890A of the radius filler 890 and/or the second radius of
curvature
59
Date Recue/Date Received 2020-05-06
R2 of the inner surface 834 at the lower corner portion 852 can be
substantially
constant over the length 849 of the composite stringer 820. Also, along the
longitudinal axis 848, the third radius of curvature R3 of the third surface
890C of the
radius filler 890 can be substantially constant over the length 849 of the
composite
.. stringer 820. These features can additionally or alternatively help to
reduce a size of
the radius filler 890, improve strength of the composite stringer assembly
801, simplify
tooling requirements for forming the composite stringer assembly 801, and/or
reduce
variability among a plurality of composite stringers 820.
[0228] As shown in Figures 8A-8B, the composite stringer assembly 801
can also
.. include a second radius filler 892 coupled to the second lower corner
portion 856. The
second radius filler 892 can help to strengthen the composite stringer
assembly 801
at the second lower corner portion 856. The second radius filler 892 can be
substantially similar or identical to the radius filler 890, except the second
radius filler
892 is coupled to the second lower corner portion 856 instead of the lower
corner
portion 852. Accordingly, the second lower corner portion 856 can include a
fourth
surface 892A coupled to the inner surface 834 at the second lower corner
portion 856,
a fifth surface 892B configured to couple to the support structure 822, and a
sixth
surface 892C extending between the fourth surface 892A and the fifth surface
892B.
[0229] The second lower corner portion 856 and the second radius filler
992 can
.. include any or all of the features of the first radius of curvature R1, the
second radius
of curvature R2, and/or the third radius of curvature R3 at portions of the
second lower
corner portion 856 and the second radius filler 992 that correspond to the
portions of
the lower corner portion 852 and the radius filler 990 having the first radius
of curvature
R1, the second radius of curvature R2, and/or the third radius of curvature
R3. In
.. particular, the features and concepts described above with respect to the
first surface
890A can apply to the fourth surface 892A, the features and concepts described
above
with respect to the second surface 890B can apply to the fifth surface 892B,
and/or
the features and concepts described above with respect to the third surface
890C can
apply to the sixth surface 892C. Similarly, the features and concepts
described above
.. with respect to the inner surface 834 at the lower corner portion 852 can
apply to the
Date Recue/Date Received 2020-05-06
inner surface 834 at the second lower corner portion 856, and/or the features
and
concepts described above with respect to the outer surface 836 at the lower
corner
portion 852 can apply to the outer surface 836 at the second lower corner
portion 856.
[0230] As described above, a variability among a plurality of composite
stringers
820 can be reduced by (i) forming the outer surface 836 at the lower corner
portion
852 with the first radius of curvature R1 that is substantially constant
and/or (ii) forming
the inner surface 834 at the lower corner portion 852 with the second radius
of
curvature R2 that is substantially constant. Further, reducing the variability
of these
features among the plurality of composite stringers 820 can help to reduce
manufacturing costs and/or simplify tooling requirements forming a composite
stringer
assembly 801 including a plurality of composite stringers 820.
[0231] For example, a single type of radius filler 890 having one size
and/or one
shape can be used with a plurality of different types of composite stringers
820 when
the outer surfaces 836 and/or the inner surfaces 834 at the lower corner
portions 852
of the composite stringers 820 have a common, constant first radius of
curvature R1
and/or a common, constant second radius of curvature R2, respectively. For
instance,
a plurality of composite stringers 820 having different second gages 840 at
the top
flanges 826 can be coupled with a common type of radius filler 890 when the
outer
surfaces 836 and/or the inner surfaces 834 at the lower corner portions 852 of
the
composite stringers 820 have a common, constant first radius of curvature R1
and/or
a common, constant second radius of curvature R2, respectively
[0232] Figures 9A-9B depict a composite stringer assembly 901, which
includes a
support structure 922, a plurality of composite stringers 920A, 920B, and a
radius filler
990 according to an example. In particular, Figure 9A depicts a side view of
the
.. composite stringer assembly 901, and Figure 9B depicts a perspective view
of the
composite stringer assembly 901.
[0233] Within examples, the support structure 922 can include at least
one of a
skin of a vehicle or a base charge (e.g., the skin 323, 823 and/or the base
charge 788,
888 described above). As shown in Figures 9A-9B, the composite stringers 920A,
61
Date Recue/Date Received 2020-05-06
920B include a first composite stringer 920A and a second composite stringer
920B.
Although two composite stringers 920A, 920B are shown in Figures 9A-9B, the
composite stringer assembly 901 can include more than two composite stringers
920A, 920B in other examples.
[0234] As shown in Figures 9A-9B, the composite stringers 920A, 920B are
axially
aligned with each other along a longitudinal axis 948 of the composite
stringers 920A,
920B. Additionally, as shown in Figure 9B, a first end 950A of the second
composite
stringer 920B can abut against a second end 950B of the first composite
stringer 920A.
[0235] The composite stringers 920A, 920B can be substantially similar
or
.. identical to the composite stringers 320, 820 described above. For example,
as shown
in Figures 9A-9B, each composite stringer 920A, 920B can include a skin flange
924
configured to be coupled to the support structure 922, a web 928, lower corner
portion
952 extending from the skin flange 924 to the web 928, a top flange 926, an
upper
corner portion 954 extending from the web 928 to the top flange 926.
Additionally, for
.. example, each composite stringer 920A, 920B can include (i) an inner
surface 934
extending along the skin flange 924, the lower corner portion 952, the web
928, the
upper corner portion 954, and the top flange 926, and (ii) an outer surface
936
extending along the skin flange 924, the lower corner portion 952, the web
928, the
upper corner portion 954, and the top flange 926.
[0236] In Figures 9A-9B, at the lower corner portion 952 of each composite
stringer
920A, 920B, the outer surface 936 is defined by a first radius of curvature R1
and the
first radius of curvature R1 is substantially constant between the skin flange
924 and
the web 928 of the composite stringer 920A, 920B. Additionally, in Figures 9A-
9B, at
the lower corner portion 952 of each composite stringer 920A, 920B, the inner
surface
934 can be defined by a second radius of curvature R2 and the second radius of
curvature R2 can be substantially constant between the skin flange 924 and the
web
928 of the composite stringer 920A, 920B. As such, in Figures 9A-9B, the lower
corner
portion 952 of the first composite stringer 920A and the lower corner portion
952 of
the second composite stringer 920B are both defined by the same first radius
of
62
Date Recue/Date Received 2020-05-06
curvature R1 and/or the same second radius of curvature R2. Thus, in an
arrangement in which the composite stringers 920A, 920B can be axially aligned
and
positioned end-to-end as shown in Figures 9A-9B, a radius filler region
between the
lower corner portions 952 and the support structure 922 can have a
substantially
similar or identical shape, size, and/or alignment.
[0237] The radius filler 990 can be substantially similar or identical
to the radius
filler 890 described above with respect to Figures 8A-8B. For example, the
radius filler
990 can include a first surface 990A coupled to the inner surface 934 at the
lower
corner portion 952 of each composite stringer 920A, 920B, a second surface
990B
configured to couple to the support structure 922, and a third surface 990C
extending
between the first surface 990A and the second surface 990B. In Figures 9A-9B,
the
first surface 990A of the radius filler 990 also can be defined by the second
radius of
curvature R2, and the second radius of curvature R2 can be substantially
constant
between the second surface 990B and the third surface 990C. Also, in Figures
9A-
9B, the second radius of curvature R2 can be approximately equal to a sum of
the first
radius of curvature R1 and a first gage 938 of the skin flange 924.
[0238] Within examples, along the longitudinal axis 948 shown in Figure
9B: (i) the
composite stringer assembly 901 can have a total length 949 that is equal to a
sum of
a respective length of each composite stringer 920A, 920B, (ii) the first
radius of
curvature R1 can be substantially constant over the total length 949 of the
composite
stringer assembly 901, and (iii) the second radius of curvature R2 can be
substantially
constant over the total length 949 of the composite stringer assembly 901.
[0239] Thus, in this arrangement, a shape and/or a size of the first
surface 990A
of the radius filler 990 can substantially match both (i) a shape and/or a
size of the
lower corner portion 352 of the first composite stringer 920A and (ii) a shape
and/or a
size of the lower corner portion 352 of the second composite stringer 920B. As
described above, this can help to reduce manufacturing costs and/or simplify
tooling
requirements for forming the composite stringer assembly at least because the
radius
63
Date Recue/Date Received 2020-05-06
filler 990 can extend along the plurality of composite stringers 920A, 920B
with a
constant shape that is compatible with those composite stringers 920A, 920B.
[0240] As shown in Figures 9A-9B, the compatibility of the radius
filler 990 with the
composite stringers 920A, 920B can be achieved even when there are variations
in at
least a portion of the composite stringers 920A, 920B. For example, in Figures
9A-
9B, the top flange 926 of the first composite stringer 920A of the plurality
of composite
stringers 920A, 920B has a second gage 940A that is different than a second
gage
940B of the top flange 926 of a second composite stringer 920B of the
plurality of
composite stringers 920A, 920B. Accordingly, within examples, the second gage
940A, 940B of the top flanges 926 can be varied on a per-stringer basis to
more
specifically tailor a load carrying capability of the composite stringer
assembly 901 to
expected load conditions at different locations, while simultaneously
maintaining a
relatively constant configuration of the lower corner portions 952 of the
composite
stringers 920A, 920B to achieve a relatively universal and/or efficient
forming of the
radius filler 990.
[0241] Within examples, each composite stringer 920A, 920B can also
include a
second skin flange 930 configured to be coupled to the support structure 922,
a
second web 932, a second lower corner portion 956 extending from the second
skin
flange 930 to the second web 932, a second upper corner portion 958 extending
from
the second web 932 to the top flange 926. The inner surface 934 can also
extend
along the second skin flange 930, the second lower corner portion 956, the
second
web 932, and the second upper corner portion 958. The outer surface 936 can
also
along the second skin flange 930, the second lower corner portion 956, the
second
web 932, and the second upper corner portion 958. The composite stringer
assembly
901 can also include a second radius filler 992 coupled to the second lower
corner
portion 956 of each composite stringer 920A, 920B. As described above, the
second
radius filler 992 can be substantially similar or identical to the radius
filler 990, except
the second radius filler 992 is coupled to the second lower corner portion 956
instead
of the lower corner portion 952 of each composite stringer 920A, 920B.
64
Date Recue/Date Received 2020-05-06
[0242] Also, within examples, the skin flange 924, the web 928, the top
flange 926,
the second web 932, and/or the second skin flange 930 can have any or all of
the
features described above with respect to the composite stringers 320, 820
shown in
Figures 3A-3B and 7-8B. Similarly, the lower corner portion 952, the upper
corner
portion 954, the second lower corner portion 956, and/or the second upper
corner
portion 958 can have any of the features described above with respect to the
composite stringers 320, 820 shown in Figures 3A-3B and 7-8B, and/or the
composite
structures 470, 570, 670 shown in Figures 4-6.
[0243] For instance, for each composite stringer 920A, 920B, the skin
flange 924,
the web 928, the top flange 926, the second web 932, the second skin flange
930, the
lower corner portion 952, the upper corner portion 954, the second lower
corner
portion 956, and/or the second upper corner portion 958 can include a
plurality of plies
of composite material. Additionally, for each composite stringer 920A, 920B,
the skin
flange 924 can have the first gage 938, the top flange 926 can have the second
gage
940A, 940B, the web 928 can have a third gage 942, the second skin flange 930
can
have a fourth gage 944, and/or the second web 932 can have a fifth gage 946.
[0244] Within examples, these respective gages 938, 940A, 940B, 942,
944, 946
of the composite stringers 920A, 920B can be configured as described above.
For
instance, for each composite stringer 920A, 920B, the second gage 940A, 940B
of the
top flange 926 can be greater than the first gage 938 of the skin flange 924
and the
third gage 942 of the web 928, and/or the second gage 940A, 940B of the top
flange
926 can be greater than the fourth gage 944 of the second skin flange 930 and
the
fifth gage 946 of the second web 932. As described above, this can help to
increase
a strength-to-weight ratio of the composite stringers 920A, 920B. Additionally
or
alternatively, it can help to provide greater strength (and/or greater
stiffness) at the top
flange 926 to enhance load transfer performance, while providing greater
flexibility at
an interface between the composite stringer 920 and the support structure 922.
[0245] Also, for each composite stringer 920A, 920B, the first gage 938
of the skin
flange 924 can be approximately equal to the third gage 942 of the web 928,
and/or
Date Recue/Date Received 2020-05-06
the fourth gage 944 of the second skin flange 930 can be approximately equal
to the
fifth gage 946 of the second web 932. In an implementation in which the first
gage
938 of the skin flange 924 is approximately equal to the third gage 942 of the
web 928,
the lower corner portion 952 can have a gage that is also approximately equal
to the
first gage 938 and the third gage 942. Similarly, in an implementation in
which the
fourth gage 944 of the second skin flange 930 is approximately equal to the
fifth gage
946 of the second web 932, the second lower corner portion 956 can have a gage
that
is also approximately equal to the fourth gage 944 and the fifth gage 946. As
described above, this configuration of the skin flange 924, the lower corner
portion
952, the web 928, the second skin flange 930, the second lower corner portion
956,
and/or the second web 932 can help to reduce (or may minimize) a size of the
radius
filler 990 and/or the second radius filler 992.
[0246] Also, within examples, the web 928 and the skin flange 924 of
the first
composite stringer 920A can have a gage that is approximately equal to a gage
of the
web 928 and the skin flange 924 of the second composite stringer 920B (i.e.,
the third
gage 942 and the first gage 938 of the first composite stringer 920A can be
approximately equal to the third gage 942 and the first gage 938 of the second
composite stringer 920B). Similarly, for example, the second web 932 and the
second
skin flange 930 of the first composite stringer 920A can have a gage that is
approximately equal to a gage of the second web 932 and the second skin flange
930
of the second composite stringer 920B (i.e., the fifth gage 946 and the fourth
gage 944
of the first composite stringer 920A can be approximately equal to the fifth
gage 946
and the fourth gage 944 of the second composite stringer 920B). This can
additionally
or alternatively help to reduce (or may minimize) variability among the
composite
stringers 920A, 920B at the lower corner portion 952 and/or the second lower
corner
portion 956.
[0247] Referring now to Figure 10, a composite stringer assembly 1001
is shown
according to another example. As shown in Figure 10, the composite stringer
assembly 1001 includes a composite stringer 1020, a radius filler 1090, and an
overwrap layer 1094. The composite stringer assembly 1001 can also include a
66
Date Recue/Date Received 2020-05-06
support structure 1022 coupled to the composite stringer 1020, the radius
filler 1090,
and/or the overwrap layer 1094. In Figure 10 the support structure 1022
includes a
skin 1023 of a vehicle and a base charge 1088. However, in another example,
the
support structure 1022 can include the skin 1023 of the vehicle and omit the
base
charge 1088. More generally, as described above, the support structure 1022
can
include at least one of the skin 1023 of the vehicle or the base charge 1088.
[0248] The composite stringer 1020 can be substantially similar or
identical to the
composite stringers 320, 820, 920A, 920B described. For example, as shown in
Figures 10, the composite stringer 1020 includes a skin flange 1024 that is
configured
to be coupled to the support structure 1022, a web 1028, a lower corner
portion 1052
extending from the skin flange 1024 to the web 1028, and an inner surface 1034
extending along the skin flange 1024, the lower corner portion 1052, and the
web
1028.
[0249] In some examples, the composite stringer 1020 can be in the form
of a hat-
shaped stringer. As such, the composite stringer 1020 can also include a top
flange
1026, an upper corner portion 1054 extending from the web 1028 to the top
flange
1026. The web 1028 and the upper corner portion 1054 can extend from a first
side
1026A of the top flange 1026. Additionally, as a hat-shaped stringer, the
composite
stringer 1020 can further include a second skin flange 1030 configured to be
coupled
to the support structure 1022 and a second web 1032 extending between the
second
skin flange 1030 and a second side 1026B of the top flange 1026. The composite
stringer 1020 can also include a second lower corner portion 1056 extending
form the
second skin flange 1030 to the second web 1032, and a second upper corner
portion
1058 extending from the second web 1032 to the top flange 1026.
[0250] In this arrangement, the inner surface 1034 can also extend along
the upper
corner portion 1054, the top flange 1026, the second upper corner portion
1058, the
second web 1032, the second lower corner portion 1056, and/or the second skin
flange 1030. The composite stringer 1020 can also include an outer surface
1036
extending along the skin flange 1024, the lower corner portion 1052, the web
1028,
67
Date Recue/Date Received 2020-05-06
the upper corner portion 1054, the top flange 1026, the second upper corner
portion
1058, the second web 1032, the second lower corner portion 1056, and/or the
second
skin flange 1030. The inner surface 1034 faces the support structure 1022 when
the
skin flange 1024 and/or the second skin flange 1030 are coupled to the support
structure 1022, and the outer surface 1036 faces away from the support
structure 1022
when the skin flange 1024 and/or the second skin flange 1030 are coupled to
the
support structure 1022.
[0251] Although the composite stringer 1020 shown in Figure 10 is a hat-
shaped
stringer, as described below with respect to Figures 12-15, the principles
described
with respect to Figure 10 can extend to apply to other types of composite
stringers
(e.g., J-shaped stringers, C-shaped stringers, l-shaped stringers, and/or Z-
shaped
stringers). In particular, the concepts and principles described herein can be
applied
to any type of composite stringer that includes at least the skin flange 1024,
the web
1028, and the lower corner portion 1052 extending from the skin flange 1024 to
the
web 1028.
[0252] Within examples, the skin flange 1024, the web 1028, the top
flange 1026,
the second web 1032, and/or the second skin flange 1030 can have any or all of
the
features described above with respect to the composite stringers 320, 820,
920A,
920B shown in Figures 3A-3B and 7-9B. Similarly, the lower corner portion
1052, the
upper corner portion 1054, the second lower corner portion 1056, and/or the
second
upper corner portion 1058 can have any of the features described above with
respect
to the composite stringers 320, 820, 920A, 920B shown in Figures 3A-3B and 7-
9B,
and/or the composite structures 470, 570, 670 shown in Figures 4-6.
[0253] For instance, in some examples, the skin flange 1024, the web
1028, the
top flange 1026, the second web 1032, the second skin flange 1030, the lower
corner
portion 1052, the upper corner portion 1054, the second lower corner portion
1056,
and/or the second upper corner portion 1058 can include a plurality of plies
of
composite material. Additionally, for example, the skin flange 1024 can have a
first
gage 1038, the top flange 1026 can have a second gage 1040, the web 1028 can
68
Date Recue/Date Received 2020-05-06
have a third gage 1042, the second skin flange 1030 can have a fourth gage
1044,
and/or the second web 1032 can have a fifth gage 1046.
[0254] Within examples, these respective gages 1038, 1040, 1042, 1044,
1046 of
the composite stringer 1020 can be configured as described above. For
instance, the
second gage 1040 of the top flange 1026 can be greater than the first gage
1038 of
the skin flange 1024 and the third gage 1042 of the web 1028, and/or the
second gage
1040 of the top flange 1026 can be greater than the fourth gage 1044 of the
second
skin flange 1030 and the fifth gage 1046 of the second web 1032. As described
above,
this can help to increase a strength-to-weight ratio of the composite stringer
1020.
Additionally or alternatively, it can help to provide greater strength (and/or
greater
stiffness) at the top flange 1026 to enhance load transfer performance, while
providing
greater flexibility at an interface between the composite stringer 1020 and
the support
structure 1022.
[0255] Also, within examples, the first gage 1038 of the skin flange
1024 can be
approximately equal to the third gage 1042 of the web 1028, and/or the fourth
gage
1044 of the second skin flange 1030 can be approximately equal to the fifth
gage 1046
of the second web 1032. In an implementation in which the first gage 1038 of
the skin
flange 1024 is approximately equal to the third gage 1042 of the web 1028, the
lower
corner portion 1052 can have a gage that is also approximately equal to the
first gage
1038 and the third gage 1042. Similarly, in an implementation in which the
fourth gage
1044 of the second skin flange 1030 is approximately equal to the fifth gage
1046 of
the second web 1032, the second lower corner portion 1056 can have a gage that
is
also approximately equal to the fourth gage 1044 and the fifth gage 1046. As
described above, this configuration of the skin flange 1024, the lower corner
portion
1052, the web 1028, the second skin flange 1030, the second lower corner
portion
1056, and/or the second web 1032 can help to reduce (or may minimize) a size
of the
radius filler 1090 and/or a second radius filler 1092.
[0256] The radius filler 1090 can be substantially similar or identical
to the radius
fillers 890, 990 described above. For example, the radius filler 1090 can
include a first
69
Date Recue/Date Received 2020-05-06
surface 1090A coupled to the inner surface 1034 at the lower corner portion
1052, a
second surface 1090B configured to couple to the support structure 1022, and a
third
surface 1090C extending between the first surface 1090A and the second surface
1090B.
[0257] Within examples, the composite stringer assembly 1001 can also
include a
second radius filler 1092. The second radius filler 1092 can be substantially
similar or
identical to the second radius fillers 892, 992 described above. For example,
the
second radius filler 1092 can include a fourth surface 1092A coupled to the
inner
surface 1034 at the second lower corner portion 1056, a fifth surface 1092B
configured
to couple to the support structure 1022, and a sixth surface 1092C extending
between
the fourth surface 1092A and fifth surface 1092B.
[0258] The overwrap layer 1094 is coupled to the inner surface 1034 at
the web
1028, the third surface 1090C of the radius filler 1090, and the support
structure 1022
(e.g., the base charge 1088 of the support structure 1022 or the skin 1023 of
the
support structure 1022). In this arrangement, the overwrap layer 1094 can help
to
support the web 1028, the skin flange 1024, and/or the radius filler 1090 and,
thus,
help to mitigate (or may prevent) delamination between the composite stringer
1020,
the radius filler 1090, and/or the support structure 1022.
[0259] In one example, the overwrap layer 1094 can include one or more
plies of
composite material (e.g., the plies 474, 574, 674). In another example, the
overwrap
layer 1094 can include a quantity of plies of composite material between one
ply and
six plies. Within examples, the quantity of the plies of composite material
that form
the overwrap layer 1094 can be based on one or more factors selected from a
group
of factors consisting of: (i) expected load conditions that may be experienced
by the
composite stringer assembly 1001, (ii) a location of the composite stringer
assembly
1001 in a vehicle (e.g., an aircraft), (iii) the first gage 1038 of the skin
flange 1024
and/or the third gage 1042 of the web 1028, (iv) a stiffness of the skin
flange 1024
and/or a stiffness of the support structure 1022, (v) one or more radii of
curvature of
Date Recue/Date Received 2020-05-06
the lower corner portion 1052 and/or the radius filler 1090, and (vi) a weight
of the
composite stringer assembly 1001.
[0260] As shown in Figure 10, the overwrap layer 1094 can also be
coupled to the
inner surface 1034 at the second web 1032, the sixth surface 1092C of the
second
radius filler 1092, and the support structure 1022 (e.g., the base charge 1088
of the
support structure 1022 or the skin 1023 of the support structure 1022).
Accordingly,
in Figure 10, the overwrap layer 1094 can extend over the support structure
1022
(e.g., over the base charge 1088) from the radius filler 1090 to the second
radius filler
1092. Thus, in Figure 10, the overwrap layer 1094 can also can help to support
the
second web 1032, the second skin flange 1030, and/or the second radius filler
1092
and, thus, help to further mitigate (or may prevent) delamination between the
composite stringer 1020, the second radius filler 1092, and/or the support
structure
1022.
[0261] More particularly, as shown in Figure 10, the overwrap layer
1094 can
continuously extend from a first end 1094A to a second end 1094B. In Figure
10, the
first end 1094A of the overwrap layer 1094 is at a position that is (i) on the
inner surface
1034 at the web 1028 and (ii) above the radius filler 1090. Additionally, the
second
end 1094B of the overwrap layer 1094 is at a position that is (i) on the inner
surface
1034 at the second web 1032 and (ii) above the second radius filler 1092.
Within
examples, a shear load on the composite stringer assembly 1001 may be
relatively
low at a point on the web 1028 above the radius filler 1090 and/or a point on
the
second web 1032 above the second radius filler 1092. Thus, with the first end
1094A
and the second end 1094B arranged in this way, the overwrap layer 1094 can be
configured to extend over one or more portions of the composite stringer
assembly
1001 that may experience a relatively higher shear load, and not extend over
one or
more portions that may experience a relatively lower shear load. This, in
turn, can
help to balance the benefits of the additional support against delamination
provided
by the overwrap layer 1094 against a weight penalty associated with including
the
overwrap layer 1094.
71
Date Recue/Date Received 2020-05-06
[0262] In one example, the overwrap layer 1094 can be coupled to at
least
approximately 0.1 inches of the inner surface 1034 at the web 1028 and/or at
least
approximately 0.1 inches of the inner surface 1034 at the second web 1032. In
other
words, the first end 1094A of the overwrap layer 1094 can be at a distance of
at least
.. approximately 0.1 inches above the radius filler 1090 and/or the second end
1094B of
the overwrap layer 1094 can be at a distance of at least approximately 0.1
inches
above the second radius filler 1092. In another example, the overwrap layer
1094 can
be coupled to at least approximately 0.25 inches of the inner surface 1034 at
the web
1028 and/or at least approximately 0.25 inches of the inner surface 1034 at
the second
web 1032. This can help to improve the overwrap layer 1094 protecting the
radius filler
1090. In another example, the overwrap layer 1094 can be coupled to
approximately
0.1 inches to approximately 2.5 inches of the inner surface 1034 at the web
1028
and/or approximately 0.1 inches to approximately 2.5 inches of the inner
surface 1034
at the second web 1032.
[0263] In Figure 10, the overwrap layer 1094 can extend entirely over the
support
structure 1022 (e.g., over the base charge 1088) between the radius filler
1090 and
the second radius filler 1092. However, in another example, the overwrap layer
1094
may not extend entirely over the support structure 1022 between the radius
filler 1090
and the second radius filler 1092. An implementation of such example is shown
in
.. Figure 11. In particular, Figure 11 shows a composite stringer assembly
1101
according to another example.
[0264] As shown in Figure 11, the composite stringer assembly 1101
includes the
composite stringer 1020 and the radius filler 1090 described above with
respect to
Figure. The composite stringer assembly 1101 can also include the support
structure
1022 and/or the second radius filler 1092 described above with respect to
Figure 10.
The composite stringer assembly 1101 is thus substantially similar or
identical to the
composite stringer assembly 1001 described above for Figure 10, except the
composite stringer assembly 1101 includes two overwrap layers. Specifically,
the
composite stringer assembly 1101 includes an overwrap layer 1194 and a second
overwrap layer 1196.
72
Date Recue/Date Received 2020-05-06
[0265] The overwrap layer 1194 is coupled to the inner surface 1034 at
the web
1028, the third surface 1090C of the radius filler 1090, and the support
structure 1022
(e.g., the base charge 1088 of the support structure 1022 or the skin 1023 of
the
support structure 1022). In this arrangement, the overwrap layer 1194 can help
to
support the web 1028, the skin flange 1024, and/or the radius filler 1090 and,
thus,
help to mitigate (or may prevent) delamination between the composite stringer
1020,
the radius filler 1090, and/or the support structure 1022.
[0266] The second overwrap layer 1196 is coupled to the inner surface
1034 at
the second web 1032, the sixth surface 1092C of the second radius filler 1092,
and
the support structure 1022 (e.g., the base charge 1088 of the support
structure 1022
or the skin 1023 of the support structure 1022). Thus, in Figure 11, the
second
overwrap layer 1196 can also can help to support the second web 1032, the
second
skin flange 1030, and/or the second radius filler 1092 and, thus, help to
mitigate (or
may prevent) delamination between the composite stringer 1020, the second
radius
filler 1092, and/or the support structure 1022.
[0267] As shown in Figure 11, the overwrap layer 1194 is separated from
the
second overwrap layer 1196 by a gap 1198 exposing a portion of the support
structure
1022 (e.g., the base charge 1088 and/or the skin 1023) between the overwrap
layer
1194 and the second overwrap layer 1196. For example, in Figure 11, (i) the
overwrap
layer 1194 can extend from a first end 1194A at the inner surface 1034 of the
web
1028 to a second end 1194B at the support structure 1022, (ii) the second
overwrap
layer 1196 can extend from a first end 1196A at the inner surface 1034 of the
second
web 1032 to a second end 1196B at the support structure 1022, and (iii) the
gap 1198
can extend from the first end 1194A of the overwrap layer 1194 to the second
end
1196B of the second overwrap layer 1196. Because the composite stringer
assembly
1101 includes the gap 1198 between the overwrap layer 1194 and the second
overwrap layer 1196, the composite stringer assembly 1101 can be lighter in
weight
than the composite stringer assembly 1101 in which the overwrap layer 1094
extends
entirely over the support structure 1022 between the radius filler 1090 and
the second
radius filler 1092.
73
Date Recue/Date Received 2020-05-06
[0268] In one example, the overwrap layer 1194 and the second overwrap
layer
1196 can each include one or more plies of composite material (e.g., the plies
474,
574, 674). In another example, the overwrap layer 1194 and the second overwrap
layer 1196 can each include a quantity of plies of composite material between
one ply
and six plies. Within examples, the quantity of the plies of composite
material that
form the overwrap layer 1194 and/or the second overwrap layer 1196 can be
based
on one or more factors selected from a group of factors consisting of: (i)
expected load
conditions that may be experienced by the composite stringer assembly 1101,
(ii) a
location of the composite stringer assembly 1101 in a vehicle (e.g., an
aircraft), (iii)
the first gage 1038 of the skin flange 1024 and/or the third gage 1042 of the
web 1028,
(iv) a stiffness of the skin flange 1024 and/or a stiffness of the support
structure 1022,
(v) one or more radii of curvature of the lower corner portion 1052 and/or the
radius
filler 1090, and (vi) a weight of the composite stringer assembly 1101.
[0269] In one example, the overwrap layer 1194 can be coupled to at
least
approximately 0.1 inches of the inner surface 1034 at the web 1028 and/or the
second
overwrap layer 1196 can be coupled to at least approximately 0.1 inches of the
inner
surface 1034 at the second web 1032. In other words, the first end 1194A of
the
overwrap layer 1194 can be at a distance of at least approximately 0.1 inches
above
the radius filler 1090 and/or the first end 1196A of the second overwrap layer
1196
can be at a distance of at least approximately 0.1 inches above the second
radius filler
1092. In another example, the overwrap layer 1194 can be coupled to at least
approximately 0.25 inches of the inner surface 1034 at the web 1028 and/or the
second overwrap layer 1196 can be coupled to at least approximately 0.25
inches of
the inner surface 1034 at the second web 1032. In another example, the
overwrap
layer 1194 can be coupled to approximately 0.1 inches to approximately 2.5
inches of
the inner surface 1034 at the web 1028 and/or the second overwrap layer 1196
can
be coupled to approximately 0.1 inches to approximately 2.5 inches of the
inner
surface 1034 at the second web 1032.
[0270] As described above, although the composite stringers 320, 820,
920A,
920B, 1020 shown in Figures 3A-3B and 7A-11 are in the form of a hat-shaped
74
Date Recue/Date Received 2020-05-06
stringer, the principles described in the present disclosure can extend to
apply to other
types of composite stringers (e.g., J-shaped stringers, C-shaped stringers, l-
shaped
stringers, and/or Z-shaped stringers). Figures 12-15 depict composite stringer
assemblies including additional or alternative types of composite stringers,
which can
include one or more of the features described above, according to examples.
[0271] Figure 12 depicts a composite stringer assembly 1201, which
includes a
composite stringer 1220 in the form of an l-shaped stringer, according to an
example.
As shown in Figure 12, the composite stringer 1220 includes a skin flange
1224, a
web 1228, a top flange 1226, and a second skin flange 1230. The web 1228
extends
from a first end 1228A to a second end 1228B. The skin flange 1224 and the
second
skin flange 1230 extend from opposing sides of the first end 1228A of the web
1228.
A first portion 1226A of the top flange 1226 and a second portion 1226B of the
top
flange 1226 extend from opposing sides of the second end 1228B of the web
1228.
The composite stringer assembly 1201 can also include a support structure
1222, as
described above.
[0272] Figure 13 depicts a composite stringer assembly 1301, which
includes a
composite stringer 1320 in the form of a Y-shaped stringer, according to an
example.
As shown in Figure 13, the composite stringer 1320 includes a skin flange
1324, a
web 1328, a top flange 1326, and a second skin flange 1330. The web 1328
extends
from a first end 1328A to a second end 1328B. Between the first end 1328A and
the
second end 1328B, the web 1328 includes a vertex 1328C. A first portion 1328D
of
the web 1328 extends from the vertex 1328C to the skin flange 1324 at the
first end
1328A of the web 1328. A second portion 1328E of the web 1328 extends from the
vertex 1328C to the second skin flange 1330 at the first end 1328A of the web
1328.
A third portion 1328F of the web 1328 extends from the vertex 1328C to the top
flange
1326 at the second end 1328B of the web 1328. Additionally, in Figure 13, a
first
portion 1326A of the top flange 1326 and a second portion 1326B of the top
flange
1326 extend from opposing sides of the second end 1328B of the web 1328. The
composite stringer assembly 1301 can also include a support structure 1322, as
described above.
Date Recue/Date Received 2020-05-06
[0273] Figure 14 depicts a composite stringer assembly 1401, which
includes a
composite stringer 1420 in the form of a J-shaped stringer, according to an
example.
As shown in Figure 14, the composite stringer 1420 includes a skin flange
1424, a
web 1428, a top flange 1426, and a second skin flange 1430. The web 1428
extends
from a first end 1428A to a second end 1428B. The skin flange 1424 and the
second
skin flange 1430 extend from opposing sides of the first end 1428A of the web
1428.
The top flange 1426 extend extends from one side of the second end 1428B of
the
web 1428. The composite stringer assembly 1401 can also include a support
structure
1422, as described above.
[0274] Figure 15 depicts a composite stringer assembly 1501, which includes
a
composite stringer 1520 in the form of a Z-shaped stringer, according to an
example.
As shown in Figure 15, the composite stringer 1520 includes a skin flange
1524, a
web 1528, and a top flange 1526. The web 1528 extends from a first end 1528A
to a
second end 1528B. The skin flange 1524 extends from a first of the web 1528 at
the
first end 1528A. The top flange 1526 extends from a second side of the web
1528,
which is opposite the first side of the web 1528, at the second end 1528B. The
composite stringer assembly 1501 can also include a support structure 1522, as
described above.
[0275] Within examples, the composite stringer assemblies 1201, 1301,
1401,
1501 can include one or more of the features described above with respect to
Figures
3A-11. For example, in Figures 12-15, the top flange 1226, 1326, 1426, 1526
can
have a second gage that is greater than a first gage of the skin flange 1224,
1324,
1424, 1524 and the web 1228, 1328, 1428, 1528. Additionally, for example, the
skin
flange 1224, 1324, 1424, 1524 can have a gage that is approximately equal to a
gage
of the web 1228,1328, 1428, 1528.
[0276] The composite stringers 1220, 1320, 1420, 1520 can additionally
or
alternatively include one or more corner portions between the skin flange
1224, 1324,
1424, 1524, the web 1228, 1328, 1428, 1528, the top flange 1226, 1326, 1426,
1526,
and/or the second skin flange 1230, 1330, 1430. Within examples, at least one
of the
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Date Recue/Date Received 2020-05-06
one or more corner portions can have a variable gage as described above with
respect
to the composite structures 470, 570, 670 and shown in Figures 4-6.
[0277] Also, within examples, the one or more corner portions
additionally or
alternatively can be defined by one or more radii of curvature such as, for
instance,
the first radius of curvature R1 and/or the second radius of curvature R2
described
above with respect to Figures 8A-9B. Further, within examples, the composite
stringer
assemblies 1201, 1301, 1401, 1501 can additionally or alternatively include
the radius
filler 890, 990, 1090, the second radius filler 892, 992, 1092, the overwrap
layer 1094,
1194, and/or the second overwrap layer 1196 as described above with respect to
Figures 8A-11.
[0278] Within examples, the composite stringers 220 of the aircraft 100
shown in
Figure 2 or another type of vehicle described above can include any of the
composite
stringers 320, 820, 920A, 920B, 1020, 1220, 1320, 1420, 1520 described above.
Also,
within examples, the aircraft 100 or another type of vehicle described above
can
include any of the composite stringer assemblies 301, 701, 801, 901, 1001,
1101,
1201, 1301, 1401, 1501 described above.
[0279] Referring now to Figure 16, a flowchart for a process 1600 of
forming a
composite stringer is described according to an example. As shown in Figure
16, at
block 1610, the process 1600 includes positioning a plurality of plies of
composite
material on a layup to form a skin flange, a top flange, and a web extending
between
the skin flange and the top flange. After positioning the plurality of plies
of composite
material on the layup at block 1610, the process 1600 includes curing the
plurality of
plies of composite material to form a composite stringer including the skin
flange
having a first gage, the top flange having a second gage, and the web having a
third
gage at block 1612. The second gage of the top flange is greater than the
first gage
of the skin flange and the third gage of the web.
[0280] Figures 17-19 depict additional aspects of the process 1600
according to
further examples. In the example of Figure 17, the plurality of plies of
composite
material include a plurality of continuous plies and a plurality of drop-off
plies. As
77
Date Recue/Date Received 2020-05-06
shown in Figure 17, positioning the plurality of plies of composite material
on the layup
at block 1610 includes positioning the plurality of continuous plies on the
layup at the
top flange, the web, and the skin flange at block 1614, and positioning the
plurality of
drop-off plies on the layup (i) at the top flange and (ii) not at the web and
the skin
flange at block 1616.
[0281] As shown in Figure 18, positioning the plurality of plies of
composite
material on the layup at block 1610 can include positioning the plurality of
drop-off
plies such that a free end of each drop-off ply is at an upper corner portion
extending
from the top flange to the web at block 1618. As shown in Figure 19,
positioning the
plurality of plies of composite material on the layup at block 1610 can
include
positioning at least one ply of the plurality of plies of composite material
at a ply angle,
relative to a longitudinal axis of the composite stringer, which is not equal
to any one
of a group of angles consisting of: 0 degrees, +45 degrees, -45 degrees, and
90
degrees at block 1620.
[0282] Referring now to Figure 20, a flowchart for a process 2000 of
forming a
composite stringer is described according to an example. As shown in Figure
20, at
block 2010, the process 2000 includes forming a skin flange having a first
gage. The
skin flange is configured to be coupled to a support structure. The support
structure
includes at least one of a skin of a vehicle or a base charge. At block 2012,
the
process 2000 includes forming a top flange having a second gage. At block
2014, the
process 2000 includes forming a web having a third gage and extending between
the
skin flange and the top flange. The second gage of the top flange is greater
than the
first gage of the skin flange and the third gage of the web. The skin flange,
the top
flange, and the web include a plurality of plies of composite material.
[0283] Referring now to Figure 21, a flowchart for a process 2100 of
forming a
composite stringer assembly is described according to an example. As shown in
Figure 21, at block 2110, the process 2100 includes forming a composite
stringer
includes a skin flange having a first gage, a top flange having a second gage,
and a
web having a third gage and extending between the skin flange and the top
flange.
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Date Recue/Date Received 2020-05-06
The second gage of the top flange is greater than the first gage of the skin
flange and
the third gage of the web. The skin flange, the top flange, and the web
include a
plurality of plies of composite material. At block 2112, the process 2100
includes
coupling the skin flange of the composite stringer to a support structure. The
support
structure includes at least one of a skin of a vehicle or a base charge.
[0284] Figures 22-24 depict additional aspects of the process 2100
according to
further examples. As shown in Figure 22, forming the composite stringer at
block 2110
can include forming the web and the skin flange such that the third gage of
the web is
approximately equal to the first gage of the skin flange at block 2114. As
shown in
Figure 23, forming the composite stringer at block 2110 can include forming
the skin
flange such that the skin flange has a stiffness that is approximately equal
to a stiffness
of the support structure at block 2116. As shown in Figure 24, coupling the
skin flange
of the composite stringer to the support structure at block 2112 can include
co-curing
the composite stringer and the support structure at block 2118.
[0285] Referring now to Figure 25, a flowchart for a process 2500 of
forming a
composite stringer assembly is described according to an example. As shown in
Figure 25, at block 2510, the process 2500 includes forming a plurality of
composite
stringers. Forming the plurality of composite stringers at block 2510 can
include, for
each composite stringer, forming, from a plurality of plies of composite
material: (i) a
skin flange, (ii) a web, (iii) a top flange, (iii) a lower corner portion
extending from the
skin flange to the web, (iv) an upper corner portion extending from the web to
the top
flange, (v) an inner surface extending along the skin flange, the lower corner
portion,
the web, the upper corner portion, and the top flange, and (vi) an outer
surface
extending along the skin flange, the lower corner portion, the web, the upper
corner
portion, and the top flange at block 2512. Forming the plurality of composite
stringers
at block 2510 can also include forming, at the lower corner portion, the outer
surface
with a first radius of curvature at block 2514.
[0286] At block 2516, the process 2500 includes positioning, on a
support
structure, the plurality of composite stringers in axial alignment with each
other along
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Date Recue/Date Received 2020-05-06
a longitudinal axis. The support structure can include at least one of a skin
of a vehicle
or a base charge. At block 2518, the process 2500 includes coupling, to the
inner
surface of each composite stringer, a radius filler at the lower corner
portion of the
composite stringer. A first surface of the radius filler is defined by a
second radius of
curvature. Along the longitudinal axis: (i) the composite stringer assembly
has a total
length that is equal to a sum of a respective length of each composite
stringer, (ii) the
first radius of curvature is substantially constant over the total length of
the composite
stringer assembly, and (iii) the second radius of curvature is substantially
constant
over the total length of the composite stringer assembly.
[0287] Figures 26-28 depict additional aspects of the process 2500
according to
further examples. As shown in Figure 26, forming the composite stringer at
block 2512
can include forming the top flange of a first composite stringer of the
plurality of
composite stringers with a gage that is different than a gage of the top
flange of a
second composite stringer of the plurality of composite stringers at block
2520.
[0288] As shown in Figure 27, forming the composite stringer at block 2512
can
include, for each composite stringer, forming the web with a gage that is
approximately
equal to a gage of the skin flange at block 2522. As shown in Figure 28,
forming the
composite stringer at block 2512 can include forming the first composite
stringer and
the second composite stringer such that the web and the skin flange of the
first
composite stringer have a gage that is approximately equal to a gage of the
web and
the skin flange of the second composite stringer at block 2524.
[0289] Referring now to Figure 29, a flowchart for a process 2900 of
forming a
composite stringer assembly is described according to an example. As shown in
Figure 29, at block 2910, the process 2900 includes forming a composite
stringer.
Forming the composite stringer at block 2910 includes: (i) forming a skin
flange
configured to be coupled to a support structure at block 2912, (ii) forming a
web at
block 2914, (iii) forming a lower corner portion extending from the skin
flange to the
web at block 2916, (iv) forming an inner surface extending along the skin
flange, the
lower corner portion, and the web at block 2918.
Date Recue/Date Received 2020-05-06
[0290] At block 2920, the process 2900 includes coupling a radius
filler to the inner
surface of the composite stringer. At block 2922, the process 2900 includes
coupling
an overwrap layer to the inner surface at the web, the radius filler, and the
support
structure. The support structure includes at least one of a skin of a vehicle
or a base
charge.
[0291] Figures 30-38 depict additional aspects of the process 2900
according to
further examples. For process 2900 shown in Figure 30, the composite stringer
further
includes a top flange and an upper portion extending from the web to the top
flange.
As shown in Figure 30, forming the composite stringer at block 2910 can
further
include forming the skin flange with a first gage at block 2924, forming the
top flange
with a second gage at block 2926, and forming the web with a third gage at
block
2928. The second gage of the top flange is greater than the first gage of the
skin
flange and the third gage of the web.
[0292] As shown in Figure 31, forming the composite stringer at block
2910 can
include forming the web and the skin flange such that the third gage of the
web is
approximately equal to the first gage of the skin flange at block 2930.
[0293] For the process 2900 shown in Figure 32, the web extends from a
first side
of the top flange. As shown in Figure 32, forming the composite stringer at
block 2910
can further include (i) forming a second web extending from a second side of
the top
flange at block 2932, (ii) forming a second skin flange configured to be
coupled to the
support structure at block 2934, (iii) forming a second lower corner portion
extending
from the second skin flange to the second web at block 2936, and (iv) forming
the
inner surface extending along the second web, the second lower corner portion,
and
the second lower corner portion at block 2938. Also, as shown in Figure 32,
the
process 2900 can further include coupling a second radius filler to the inner
surface at
the second lower corner portion at block 2940.
[0294] As shown in Figure 33, the process 2900 can further include
coupling the
overwrap layer to the inner surface at the second web, the second radius
filler, and
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Date Recue/Date Received 2020-05-06
the support structure such that the overwrap layer extends over the support
structure
from the radius filler to the second radius filler at block 2942.
[0295] As shown in Figure 34, the process 2900 can further include
coupling a
second overwrap layer to the inner surface at the second web, the inner
surface at the
second lower corner portion, and the support structure such that the overwrap
layer is
separated from the second overwrap layer by a gap exposing a portion of the
support
structure between the overwrap layer and the second overwrap layer at block
2944.
[0296] As shown in Figure 35, coupling the overwrap layer to the inner
surface at
the web, the radius filler, and the support structure at block 2922 includes
coupling the
overwrap layer to a portion of the web that extends at least 0.25 inches above
the
radius filler at block 2946.
[0297] As shown in Figure 36, coupling the overwrap layer to the inner
surface at
the web, the radius filler, and the support structure at block 2922 includes
coupling a
quantity of plies of composite material between one ply and six plies to the
inner
surface at the web, the radius filler, and the support structure at block
2948.
[0298] As shown in Figure 37, the process 2900 can further include
coupling the
composite stringer to the support structure at block 2050. As shown in Figure
38,
coupling the composite stringer to the support structure at block 2050 can
include co-
curing the composite stringer and the support structure at block 2052.
[0299] Referring now to Figure 39, a flowchart for a process 3900 of
forming a
composite structure having a variable gage is described according to an
example. As
shown in Figure 39, at block 3910, the process 3900 includes forming a
plurality of
continuous plies. At block 3912, the process 3900 includes forming a plurality
of drop-
off plies. Forming the plurality of drop-off plies at block 3912 can include
forming, for
each drop-off ply, a tip of the drop-off ply at block 3914.
[0300] At block 3916, the process 3900 includes positioning the
plurality of
continuous plies and the plurality of drop-off plies in a stack having a first
end and a
second end. The first end has a first gage. The second end has a second gage,
which is less than the first gage. As shown in Figure 39, positioning the
plurality of
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Date Recue/Date Received 2020-05-06
continuous plies and the plurality of drop-off plies at block 3916 can include
positioning
the plurality of continuous plies such that each continuous ply extends from
the first
end to the second end at block 3918. Positioning the plurality of continuous
plies and
the plurality of drop-off plies at block 3916 can also include positioning the
plurality of
drop-off plies such that (i) each drop-off ply extends from the first end to a
respective
position of the tip of the drop-off ply between the first end and the second
end, and (ii)
the plurality of drop-off plies are separated from each other by at least one
of the
plurality of continuous plies at block 3920.
[0301] Figures 40-48 depict additional aspects of the process 3900
according to
further examples. As shown in Figure 40, forming the plurality of drop-off
plies at block
3912 can include forming, for each drop-off ply, the tip of the drop-off ply
having a
tapered shape at block 3921.
[0302] As shown in Figure 41, the process 3900 can further include,
after
positioning the plurality of continuous plies and the plurality of drop-off
plies in the
stack at block 3916, curing the plurality of continuous plies and the
plurality of drop-
off plies at block 3922.
[0303] As shown in Figure 42, positioning the plurality of continuous
plies and the
plurality of drop-off plies in the stack at block 3916 can further include
forming an outer
surface extending from the first end to the second end at block 3924, and
forming an
inner surface extending from the first end to the second end at block 3926.
The first
gage and the second gage can be respective thicknesses between the outer
surface
and the inner surface at the first end and the second end, respectively.
[0304] As shown in Figure 43, positioning the plurality of continuous
plies and the
plurality of drop-off plies in the stack at block 3916 can include positioning
a first subset
of the plurality of drop-off plies between the outer surface and a central
portion at block
3928. The central portion (i) is between the outer surface and the inner
surface and
(ii) extends from the first end to the second end. Also, in Figure 43,
positioning the
plurality of continuous plies and the plurality of drop-off plies in the stack
at block 3916
83
Date Recue/Date Received 2020-05-06
can include positioning a second subset of the plurality of drop-off plies
between the
central portion and the inner surface at block 3930.
[0305] As shown in Figure 44, positioning the first subset of the
plurality of drop-
off plies at block 3928 and positioning the second subset of the plurality of
drop-off
plies at block 3930 can include positioning the plurality of drop-off plies
such that the
tips of the first subset of the plurality of drop-off plies are arranged in a
pattern that
substantially mirrors a pattern of the tips of the second subset of the
plurality of drop-
off plies at block 3932.
[0306] As shown in Figure 45, positioning the plurality of drop-off
plies at block
3920 can include positioning the plurality of drop-off plies such that the
respective
positions of the tips of the plurality of drop-off plies are staggered from
the first end to
the second end at block 3934.
[0307] As shown in Figure 46, positioning the first subset of the
plurality of drop-
off plies at block 3928 can include (i) positioning the first subset of the
plurality of drop-
off plies in an order from a drop-off ply closest to the central portion to a
drop-off ply
closest to the outer surface at block 3936, and (ii) positioning the first
subset of the
plurality of drop-off plies such that the pattern of the tips of the first
subset of the
plurality of drop-off plies includes, with each successive drop-off ply in the
order, a
relative distance between the tip of the drop-off ply and the second end
decreases at
block 3938.
[0308] Also, as shown in Figure 46, positioning the second subset of
the plurality
of drop-off plies at block 3930 can include (i) positioning the second subset
of the
plurality of drop-off plies includes positioning the second subset of the
plurality of drop-
off plies in an order from a drop-off ply closest to the central portion to a
drop-off ply
closest to the inner surface at block 3940, and (ii) positioning the second
subset of the
plurality of drop-off plies such that the pattern of the tips of the second
subset of the
plurality of drop-off plies includes, with each successive drop-off ply in the
order, a
relative distance between the tip of the drop-off ply and the second end
decreases at
block 3942.
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Date Recue/Date Received 2020-05-06
[0309] As shown in Figure 47, positioning the plurality of drop-off
plies at block
3920 can include positioning the plurality of drop-off plies such that, for
each drop-off
ply, a distance between the tip of the drop-off ply and the tip of an adjacent
one of the
plurality of drop-off plies is at least ten times greater than a thickness of
the drop-off
ply at block 3944. For each drop-off ply, the adjacent one of the plurality of
drop-off
plies is adjacent to the drop-off ply in a dimension extending between the
outer surface
and the inner surface.
[0310] As shown in Figure 48, positioning the plurality of drop-off
plies at block
3920 can include positioning the plurality of drop-off plies such that a
distance between
.. non-adjacent ones of the plurality of drop-off plies is at least three
times greater than
a thickness of each drop-off ply at block 3946.
[0311] Referring now to Figure 49, a flowchart for a process 4900 of
forming a
composite structure having a variable gage is described according to an
example. As
shown in Figure 49, at block 4910, the process 4900 includes forming a
plurality of
continuous plies. At block 4912, the process 4900 includes forming a plurality
of drop-
off plies. Forming the plurality of drop-off plies at block 4912 can include
forming, for
each drop-off ply, a tip of the drop-off ply at block 4914.
[0312] At block 4916, the process 4900 can include positioning the
plurality of
continuous plies and the plurality of drop-off plies in a stack having (i) a
first end, (ii) a
second end, (iii) an outer surface extending from the first end to the second
end, and
(iv) an inner surface extending from the first end to the second end. The
first end has
a first gage. The second end has a second gage, which is less than the first
gage.
[0313] In Figure 49, positioning the plurality of continuous plies and
the plurality of
drop-off plies at block 4916 can include positioning the plurality of
continuous plies
such that each continuous ply extends from the first end to the second end at
block
4918. Additionally, positioning the plurality of continuous plies and the
plurality of
drop-off plies at block 4916 can also include positioning the plurality of
drop-off plies
such that each drop-off ply extends from the first end to a respective
position of the tip
of the drop-off ply between the first end and the second end at block 4920. A
first
Date Recue/Date Received 2020-05-06
subset of the plurality of drop-off plies are between the outer surface and a
central
portion of the stack and a second subset of the plurality of drop-off plies
are between
the central portion and the inner surface.
[0314]
Figures 50-56 depict additional aspects of the process 4900 according to
further examples. As shown in Figure 50, positioning the plurality of
continuous plies
and the plurality of drop-off plies in the stack at block 4916 can further
include, at block
4922, arranging the plurality of drop-off plies in a monotonically-inward
pattern
including (i) in a first order of the first subset of the plurality of drop-
off plies from the
outer surface toward the central portion, with each successive drop-off ply in
the first
order, a relative distance between the tip of the drop-off ply and the second
end
decreases, and (ii) in a second order of the second subset of the plurality of
drop-off
plies from the inner surface toward the central portion, with each successive
drop-off
ply in the second order, a relative distance between the tip of the drop-off
ply and the
second end decreases.
[0315] As shown in Figure 51, forming the plurality of drop-off plies at
block 4912
can include forming, for each drop-off ply, the tip of the drop-off ply having
a tapered
shape at block 4924.
[0316]
As shown in Figure 52, after positioning the plurality of continuous plies and
the plurality of drop-off plies in the stack at block 4916, the process 4900
can include
curing the plurality of continuous plies and the plurality of drop-off plies
at block 4926.
[0317]
As shown in Figure 53, positioning the plurality of continuous plies and the
plurality of drop-off plies at block 4916 can include positioning the
plurality of
continuous plies and the plurality of drop-off plies such that the plurality
of drop-off
plies are separated from each other by at least one of the plurality of
continuous plies
at block 4928.
[0318]
As shown in Figure 54, positioning the plurality of drop-off plies at block
4920 can include positioning the plurality of drop-off plies such that the
respective
positions of the tips of the plurality of drop-off plies are staggered from
the first end to
the second end at block 4930.
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Date Recue/Date Received 2020-05-06
[0319] As shown in Figure 55, positioning the plurality of drop-off
plies at block
4920 can include positioning the plurality of drop-off plies such that, for
each drop-off
ply, a distance between the tip of the drop-off ply and the tip of an adjacent
one of the
plurality of drop-off plies is at least ten times greater than a thickness of
the drop-off
ply at block 4932. For each drop-off ply, the adjacent one of the plurality of
drop-off
plies is adjacent to the drop-off ply in a dimension extending between the
outer surface
and the inner surface.
[0320] As shown in Figure 56, positioning the plurality of drop-off
plies at block
4920 can include positioning the plurality of drop-off plies such that a
distance between
non-adjacent ones of the plurality of drop-off plies is at least three times
greater than
a thickness of each drop-off ply at block 4934.
[0321] One or more of the blocks shown in Figures 16-56 may represent a
module,
a segment, or a portion of program code, which includes one or more
instructions
executable by a processor for implementing specific logical functions or steps
in the
process. The program code may be stored on any type of computer readable
medium
or data storage, for example, such as a storage device including a disk or
hard drive.
Further, the program code can be encoded on a computer-readable storage media
in
a machine-readable format, or on other non-transitory media or articles of
manufacture. The computer readable medium may include non-transitory computer
readable medium or memory, for example, such as computer-readable media that
stores data for short periods of time like register memory, processor cache
and
Random Access Memory (RAM). The computer readable medium may also include
non-transitory media, such as secondary or persistent long term storage, like
read
only memory (ROM), optical or magnetic disks, compact-disc read only memory
(CD-
ROM), for example. The computer readable media may also be any other volatile
or
non-volatile storage systems. The computer readable medium may be considered a
tangible computer readable storage medium, for example.
[0322] In some instances, components of the devices and/or systems
described
herein may be configured to perform the functions such that the components are
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actually configured and structured (with hardware and/or software) to enable
such
performance. Example configurations then include one or more processors
executing
instructions to cause the system to perform the functions. Similarly,
components of
the devices and/or systems may be configured so as to be arranged or adapted
to,
capable of, or suited for performing the functions, such as when operated in a
specific
manner.
[0323] The description of the different advantageous arrangements has
been
presented for purposes of illustration and description, and is not intended to
be
exhaustive or limited to the examples in the form disclosed. Many
modifications and
variations will be apparent to those of ordinary skill in the art. Further,
different
advantageous examples may describe different advantages as compared to other
advantageous examples. The example or examples selected are chosen and
described in order to explain the principles of the examples, the practical
application,
and to enable others of ordinary skill in the art to understand the disclosure
for various
.. examples with various modifications as are suited to the particular use
contemplated.
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