Note: Descriptions are shown in the official language in which they were submitted.
97~33
Description
Co!n~osite Laminate Joint Structure
and Method and APparatus for Making Same
Technical Field
This invention relates generally to a composite
laminate joint structure, including a method and
apparatus for making same, and more particularly to
a multiple ply compositeistructure containing a
sandwiched ply of longitu~inally oriented bundles of
~0 continuous filament strands which are tapered at an
angle between 5 and 15 degrees at one or both ends
of the structure to enable the across-strand shear
strength of each longitudinally-oriented filament ply
bundle to be increased so it equals the tensile
strength of the filament bundle. Composit:e laminate
joint structures made in accordance with the speci-
fications taught in this invention wi.ll exhibit. a
joint tensile strength that is soverned primarily by
the tensile strength of the lam~nate longitudinally
directed filaments rather than by the interlaminar
shear strength of the laminate matrix material.
Backqround of the Invention
This invention relates to an criented fiber
composite structure adapted for use in a wide variety
of sealing and load transfer applications and to a
method and apparatus for making same. A material
havinq two or more distinct constituent materials is
a composite material. Composite materials consist of
one or more discontinuous phases embedded in a continuo~s
phase. The discontinuous phase is usually harder and
stronger than the continuous phase and is calied the
REI~lFORCEME~T, whereas the continuous phase is termed
the MATRIX. A composite material is produced when the
volume fraction of the reinforcement exceeds ten percent
and when the property of one constituent is at least
five times greater than that of the other. Composit.e
materials characteristically exhibit significant
property changes as a result of the combination of
reinforcement and rna-rix materials.
-2-
~ ,2~7~3
Fiber Reinforced Plastic (FRP) cornposite
structures belong to one of two categories, depending
upon whether or not the fiber reinforcement consti-
tuents ale tensioned during fabrication of the
composite structure. One category to which FRP
composite structures belong is referred to as the
Loose Fiber Reinforced Plastic (Ll'RP) category. The
LFRP composites include those fabricated from chopped
strand fibers, random oriented fiber mat, surfacing
- 1~ veil, felt-like fabrics, milled fibers or woven cloth.
The other category is referred to as the Tensioned
Filament Reirlforce(3 Plastic (TFRP) category. The
TFRP composites include those fahricated from
continuous unidirectional filament strands which are
1~ collimated, oriented and tensioned during the fabri-
~ cation process. The TFRP composites are made by the
- pultrusion method, by the filament winding method,
or by the combination of these two methods ~nown as
the "I.ONGO-CIRC" method. Pultruded TFRP composites
include those containing continuous unidirectional
collimated filament reinforcements which are tensioned
~"hile the filaments are pulled through extrusion dies
which form the composite into structural shapes,
such as angles or tees, of nearly any length.
Pultruded composite structures primarily comprise
tensioned "L~NGCS", the name given by the American
Society of Mechanical Engineers (ASME) in Section X
of the Boiler and Pressure Vessel Code to longi-
tudinally oriented filament reinforcements. Filament
wound composites, on the other hand, primarilv consist
of tensioned "CIRCS", the ASME name given to circum-
ferentially wound filament reinforcements. This
invention includes the class of TFRP cormposites which
contain both LONGOS and CIRCS and particularly
t.ubular laminate structures fabricated in accordance
wit.h the "parabolic tensioning" methods taught by
U.S. patent 3,784,441. The tubular larninate structures
cescribed by the specifications and illustrations of
the present invention are ideally suited to serve as
pipe, truss and tank structures and can resist
--3--
internal pressure loads and the longidudinal and circum-
ferential stresses which are simultaneously imposed
, .
upon the tubular laminate plies.
Prior art methods for joining tubular filament
: wound laminates subjectedi to longitudinal stresses have
. 5 a joint bond strength that can never exeeed the inter-
laminate shear strength of the plastic matrix material
used to bond the laminate plies and their constituent
filament reinforcernents. The longitudinal loads
transferred through bolted flanges, ~hreaded ends and
other prior art mechanical methods used to join and
disconnect tu~ular laminate struc~ures are limi~ed by
the shear strength of the adhesive material used to
bond the flanges, threads or other joint rnaking
structures to the end portions of the tubular laminate.
The shear strength limitations characteri%ing plastic
- matrix or bonding material, restrict, if not prevent,
the use of prior art tubular laminate structures to
applications where high strength mechanical joints are
required. Prior art methods employed to mechanically
join and seal tubular laminate structures include
threaded ends and flanged ends. Threaded ends used
to mechanically join and seal composite pipe of rein-
forced plastic are generally weaker and less wear
resistant than composite flanged-ended counterparts
of equivalent size and service. For this reason
flanged ends are commonly employed to mechanically
join and seal prior art tubular laminate structures
; which are highly stressed. Such flanges are Erequently
fabricated as separate structures which are bonded -to
specially prepared end portions of the composite tubes.
Other flanges are filament wound or otherwise fo,-med
directly upon ends as an integral part of the composite
tube structure Prior art methods which employ these
types of threaded or flanged ends to mechanically
join and seal tubular laminate structures are limited
by the interlaminate shear strength of the plastic
matrix material used to fabricate threaded or flanged
laminate structures or by the shear strength of the
adhesive material used to bond preabricated threaded
or flanged structures to the ends of tubular laminate
-4~
~2297~3
structures For this reason prior art cornposite
structures which mechanically join and seal tubular
' laminate structures possess a longitudinal tensile
end-load resistance capability which is governed by
flange thic~ness, thread root section area or the
adhesive surface area employed in bonding the joint
structure rather than upon the thic~ness of certain
tubular laminate plies.
Panel laminate structures fabricated in
accordance with specifications outlined in the present
invention are ideally suited to serve as easily assembled
integral elements of monolithic wall or roof structures.
Prior art methods for joining flat or curved composite
laminate panels generally involve bonding, clamping,
riveting or bolting the panels. The prior art panel
joining methods prevent the joint strenqth to equal
a panel's maximum tensile and bending strength. This
is because the strength of bonded or clamped joints is
limited by the interlaminate shear strength of the
adhesive material bonding the laminate plies. The
strength of bonded and clamped joints is especially
diminished when panel joints are flexed or twisted
in a manner which imposes peel stresses upon the
adhesive bonding material. The strength of bolted
or riveted panel joints, although possibly superior
to bonded joints, is limited by the tear out, bearing
or crush strength of the laminate composite material.
These prior art panel joining methods do not enable
panel joints to be made which are flush with the joined
panels.
:
Disclosure of the Invention
A primary object of the present invention
is to overcome the briefly described prior art problems
and restrictions by providing a composite laminate
joint structure which enables mechanically joining
multiple ply composite laminates so that the joint
tensile strength approximately equals the combined
tensile strength of the laminate Structure filament
strands which are oriented parallel to the principal
di~ection of the joint tc-nsile stress.
-5
~L2~97~3~
l~no~her object of his invention is to
disclose how unidirectional continuous filament strands
can be positioned to increase the across - strand shear
-trength of the individual filament strands by a factor
of at ]east four and thereby enable a shear load
applied to the unidirectional filament strands to be
primarily resisted by the tensile strenqth of the
filament strands.
rrhe rnethod and apparatus for making such
a composite laminate joint structure may comprise
- the following steps:
1. Coating a cylindrical mandrel and any
seal forming appurtenants with a suitable resin
release agent.
. .
; 2. Fabricating upon the coated mandrel and
any seal forming appurtenants an impermeable inner
. liner structure from a combination of woven and
non-woven fiber reinforcemellts impregnated with a
t resin.
- 3. Placing upon the liner structure a first
ply of circumferentially oriented continuous filament
strands which are impregnated with a liquid thermo-
setting polymeric resin and forming at each extremity
of the first ply an inwardly tapered conical laminate
support structure having sufficient thickness to
provide a taper angle of at least 8 degrees.
4. Placing upon the first ply filament strands
a second ply of unidirectional longitudinal continuous
filament strands which are impregnated with a liquid
therrnosetting polymeric resin and oriented approxi-
mately parallel to the mandrel turning axis, the ends
of the longitudinal filament strands being secured by
a series of protruding pins or hooks which are uniformly
spaced around each of the pin support rings ~ocated
at the extremities of the mandrel.
--6--
~22978~
5. Placing ul~on the second ply filalllent
s~rands a third ply of circumferentially oriented
continuous filament strands which are irnpregnated with
a li~uid helmosetting plastic resin and which
tension and pre~ss the second ply filament strands
fi{lllly a~lainst the first ply filament strands to
ro!-m at each end, against removahle flange forming
s~lucl.ules, a ~langed configuration suitable for
mec~)anically connec~ing the completed composite
!aminate joint struct.ul-e to other composite laminate
joint str~lctules
6. At least partially curing and hardening
. the resin to maintain all filament strands in tension
and disconnecting the ends of the second ply longi-
tudinai.filament strands from pins or hooks ernployed
to secure the ends of the second ply filament stands.
7. Fully curing and hardening the thermo-
setting l-esin matrix ana removing the composite
laminate joint structure from the mandrel and any
seal formins app~rtendnts,
One aspect of the invention provides an appa-
ratus for forming a composite laminate joint structure
thereon comprising a mandrel comprising separate parts
releasably attached together in axial alignment by fas-
tening means, said mandrel mounted on a longitudinal axisthereof and having an annular cross section throughout
its length, at least one~pair of annular filament strand
grippin~ means spaced apart longitudinaliy on the peri-
pherv o~ one of the parts of said mandrel, each of said
gripping means extending radially outwardly from said axis
and terminating at a convex surface, the radial heights of
--7--
~Z2~7~33
said gri~pilly means being suf~icient to enable long1tua-
inally disvosed filament strands attached to said gripping
means to be formed into a composite laminate having a
tapered end configuration, at least one removable annular
flange forming means adapted to be positioned adjacent
to the in~ard angle-forming edge of a tapered laminate
comprising an end portion of a multiple ply composite
laminate struct~re formed upon said mandrel.
Other aspects of this invention are claimed in my
co-pending Canadian patent application Serial No. 419,171
filed on January 10, 1983, of which the present applica-
tion is a division.
srief Description of the Dra~,ings
Further objects of this invention will become
appaLell~ fl-om the follo~ing description and accompanying
dra~:ings ~!herein:
FIG. 1 displays the principal dimensional
design paL-ameters of an idealized section of an end
of a composite laminate joi.nt structure comprised of
a t~pered laminate ply structure sandwiched bet~een a
tanc-red support structure and a flanged load-inducing
structure in accordance with the teaching or this
ir,vention .
-7a-
12~97~;~
FIG. 2 is a perspective view of FIG. 1
illustrating the principal pressures and stresses
imposed upon the structural constituents of a
unit width of a composite laminate joint structure
subjected to a representative loading condition.
FIG 3 schematically illustrates the
relationship between the principal structural
elements of the representative laminate joint structure
depicted in FIG. 2 and the principal resulting load
vec tors.
FIG 4 is an enlarged Eragmentary perspective
view depicting the arrangement of filarnent reinforce-
ments in the laminate plies which comprise an endportion of a composite laminate joint structure made
in accordance with the teaching of this invention.
; FIG. 5 is a partially sectioned side
20 elevation view of an assembly of tubular composite
laminate joint structures used in conjunction with
appropriate pressure sealing and connecting structures
to illustrate a pipe coupling embodiment of this
- invention.
c 25
FIG. 6 is an exploded perspective view
of a pipe joint embodiment of this invention employing
a segmented coupling structure assembly similar to
that depicted in FIG. 5.
., .
Description of the Preferred Embodiment
FIGS. 1 2 and 3 schematically illustrate
the dimensional parameters and vector analyses
associated with the three principal structural elements
5 comprising an end portiOn of Che composite lamin~te
,, .
c
"
.,
--8--
~2%9~
joint structure which represents the preferred
embodiment of this invention.
The composite laminate joint structure
in its broadest application comprises at least one
end portion consisting of a first ply tapered support
structure 2a, having a taper angle "a"upon which is
formed a tapered-end second ply structure la having
a laminate thickness "T" and a taper angle a'. The
second ply laminate structure comprises continuous
filaments 1 \r~hich are oriented approximately parallel
-
to the direction of the resisting tensile load
vector Tx. A third ply laminate structure 3a is
.
formed upon the tapered end portion of the second
ply laminate and configured to form a flanged structure
which communicates an impressed unit joint load Px
directly to the filament reinforcements 1 comprising
the tapered end portion of the second ply laminate
structure 1a.
Each filament of each strand is preferably
continuous and each strand preferably contains from
204 to 12,240 (one end to 60 end) individual filarnents.
The filaments may be inorganically (glass, metal
carbon, etc.) or organically (aramid, polyamide,
fluorocarbon, etc.) composed. The preferred filament
for the hereinafter described structures constitutes
glass having an O.D. of 0.00095 inch or less. The
preferred glass filament strand for making the
hereinafter described structures has a yield of
225 to 250 yards of strand length per pound and a
minimum-dry breaking strength of from 190 to 250
pounds .
The hereinafter more fully described hardened
"adhesive means", or "composite matrix material"
used for bonding strands of superimposed lami.nate
~ plies together, may be selected from the broad
group of available thermosetting or thermoplastic
resin materials as ~lell as certain inorganic bonding
~2297~3
liquids and hydraulic cements suitably composed
for such bonding purposes. As is well known in the
art, the thermosetting resins may be polyesters,
vinylesters, furans, epoxies, phenolics , polyurethanes,
S silicones or any suitable mixture thereof. The
thermoplastic resins rnay comprise polyethylene,
polypropylene, aramid, or fluorocarbons. The
inorqanic bonding liquids may comprise the consti-
tuents of magnesium oxychloride or sirnilar hydraulic
cements. The polyesters, vinylesters and epoxies are
normally utilized in the hereinafter described
examples since they are relatively available
easily used and s~iitable for many composite structure
applications.
The forming apparatus for the cornposite
laminate joint structure is typified by a removable
forming surface or mandrel which may include a pair
of LONGO strand attachment rings each of which comprise
an annular array of strand hooks positioned at each
end of the mandrel.
The forming apparatus may also include at
least one separable annular forming unit secured to
the mandrel during laminate fabrication. The annular
forming unit may be used to govern the end thickness
and configuration of the tapered first ply support
structure and to guide the fabrication of a first
ply support structure having the desired angle of
taper.
The preferred embodiment of this invention
exhibits how the unidirectional continuous filament
strands which resist an applied joint tensile load
can be positioned in a composite laminate joint
structure in a manner that increases the "across strand"
shear path and concomitajntly increases the "across
strand" shear area and the net "across strand" shear
strength of the continuous filament strands. The
basic "across strand" shear strength of continuous
filament strands can be determined by rneasuring the
force required to punch a hardened steel die through
a laminate sheet comprised of unidirectional continuous
--1 0--
~%;~:97~
filaments bonded togethcr ~Jith a hardened thermosetting
resin and oriented in a plane perpendicular to the
punch shear force direction. The basic "across strand"
shear strength of the continuous filament strands
equals the punch shear force divided by the product of
the die punch circumference and the laminate sheet
thic~ness. It has been determined that a shear force
of approximately 6600 pounds is r~luired to punch out
a composite laminate section having a circumference
of approximately 3 inches from a laminate approxi-
mately 0.10 inch thic~ comprised to a volume fraction
of at least 45 percent of unidirectional continuous
glass filament reinforcements oriented parallel to
the faces of the laminate sheet and perpendicular to
the die punch shear force. From such tests it has
been determined that the "across strand" shear strength
of continuous glass filaments is approximately one
fourth the maximum tensile strength of filament strands
loaded in a direction parallel to their longitudinal
axis. ~Jhen the "across strand" shear path of a laminate
comprised of unidirectional filament strands is increased
so that the shear path length equals or exceeds four
times the laminate thic~ness the maximum shear force
resisted by the filament strands is no longer governed
by the combined "across strand" shear strength of the
individual filament strands but is determined instead
by the combined tensile strength of the individual
filament strands.
FIG. 1 illustrates in cross section the
arrangement and configuration of the three principal
structural elements comprising an end portion of the
preferred embodiment of the present invention.
FIG. 1 also identifies the three dimensions ~1hich
principally govern the strength per unit ~-idth of the
depicted compOsite laminate joint structure. The first
ply laminate support structure 2a is the principal
_ 1 1 _
~ ~97~33
end portion of the composite laminate joint structure
and is configured to have a taper equal to the angle
"a". The second ply laminate structure, 1a, has a
laminate thic~ness "T" and a taper angle equal to
that of the laminate support structure 2a. The third
ply laminate structure 3a is configured to firmly
contact the tapered laminate ply, 1a, and to provide
a flanged joint end structure sufficiently rigid to
enable the tapered laminate s~ructure 1a to resist
a unit tensile joint load along the shear plane
having a shear path length equal to the "S" dimension.
Table I helow illustrates how the taper angle "a"
governs the length of the "across strand" shear path,
"S" for a given thickness, "T" of the second ply
laminate structure, 1a. This relationship is
expressed by the formula S = T / sin "a".
TABLE I
TAPER A~GLE "a" ACROSS STRAND
(Degrees)SHEAR PATH LENG'rl~, "S"
. ~
2 28.6 T
11.5 T
5.8 T
3.9 T
2.3 T
2.0 T
1.4 T
1.2 T
Table I illustrates that ~3hen the end portion
of the second ply laminate structure, 1a, is configured
to have a taper angle between 5 and 15 the "across
strand" shear stress imposed upon the continuous
filament strands comprising the second ply laminate
structure becomes less than the tensile stress imposed
upon the same strands. Tensile loads resisted by
a cornposite laminate joi.nt structure similar to
that illustrated in EIG. 1 are thus governed by
-12-
97~3
the combined tensile strength of the continuous
filament strands comprising the second ply laminate
structure.
FIG. 2 is an ideali2ed perspective view
of a unit width of the end portion of a composite
laminate joint structure. The end portion of the
laminate ply structure lb is assumed to have a taper
angle "a" greater than 5 degrees and less than 10
degrees. The unit tensile joint load, Px, which is
imposed upon a unit width of the third ply flange
structure 3b is resisted by an equal and opposite
tensile load, Tx, imposed upon the unidirectional
continuous filament strands comprising a unit width
of the laminate ply structure 1b. FIG. 2 illustrates
that the unit load, Px acting upon the wedge-shaped
flange structure 3b requires a unit compression force
equal to Py to assure the second ply laminate structure,
lb, continues to resist the unit tensile load, Tx. The
unit compression force, Pv, imposed upon the third ply
flange structure is resisted by an equal and opposite
compression force,~y, acting upon the first ply -
laminate support structure, 2b.
Table II below illustrates how the magnitude
of the compression force, Py, decreases with respect
to a given tensile force Px, as the taper anc;le "a"
increases. This relationship is-expressed by the
formula P y = P x / tan "a".
TABLE II
. . .
TAPER ANGLE "a"CO~lPRESSIOI~ FORCE, "Py"
(Degrees)
_
11.4 Px
5.7 Px
3.7 Px
1.7 Px
1.0 Px
0.6 Px
FIG. 3 is a schematic diagram of vectors
imposed upon the three principal structural elements
comprising the composite laminate joint structure
-13~
~2,~978.3
configured to repl-esent a prefel-red c-mbo(1iment of he
pres~nt invention. rable III below illustrates ho~
an increase in the taper angle a serves to increase
the resultant tensile stress ~. It should be noted
that the tensile strength oE the composite laminate
joint structure of the present invention is governed
by the unit resultant tensile force, ~, imposed upon
the continuous filament strands comprising the tapered
end portion of the laminate structure 1c. As may be
noted, for low taper angles ~B approximately equals
Tx. This relationship is expressed by the formula
T R = T x / cos a .
_ABLE III
TAPER ~NGLE a RES~LTANT TE~SILE
(~egrees) ¦STRESs rR
-
1.00 Tx
1.02 Tx
1.04 Tx
1.15 Tx
1.41 Tx
2.00 Tx
Exam~le_1
~ IG. 4 depicts; the end portion of a multiple
ply composite laminate joint structure comprising a
first ply of tensioned and compacted unidirectional
continuous first filament strands 2 disposed upon
an impeL-meable plastic liner and collimat:ed to have a
direction approximately parallel to the laminate
joint end terminator and the joint flange face
configured by filament strands 3 and arranged to form
at the join~t end a tapc-red second ply support sul-face
having an angle of taper approximately equal to 8.
A second ply of tensioned and compacted unidirectional
continuous second filament str.ands 1 having a uniform
thickness ~as ~isposed transversely of and superimposed
upon the first filament strands to form the tapered-
end second ply support surface. A third ply of tensioned
-14-
~ZZ97~3
and compacted unidirectional continuous third filament
strands 3 disposed transversely of and superimposed
upon the second filament strands was confiyured to
have a joint flange on the tapered end of said second
ply and a joint flange face parallel to the terminator
of the composite laminate joint structure.
The impermeable plastic liner was made of
a thermosetting vinylester resin reinforced with a
non-woven fabric comprised o~ glass fiber. The
continuous filarnent strands comprising the first,
second and third laminate plies consisted of glass
roving strands each of which has a "yield" of 225
yards per pound, a dry strand breaking strength
in excess of 200 pounds, a strand filament count of
2000 having individual filament diameters ranging
from 0.00090 to 0.00095 inch. The resin matrix
material used to impregnate the continuous filament
strands was a liquid thermosetting polyester resin.
The total thickness of the non-tapered portion of the
exampled multiple ply compOsite structure depicted
in FIG. 4 was approximately 0.34 inch in which the
plastic liner was approximately 0.09 inch, the
first ply thickness was 0.06 inch, and the third ply
thickness was 0.12 inch. The flanged face configured
from the third ply filament strands, 3, was approximately
0.25 inches high and positioned approximately 3 inches
from the tapered end termina-tor face of the composite
laminate joint structure The above described joint
structure was able to resist an end load in excess of
7200 pounds per inch of joint structure width.
Example 2
FIG. 5 illustrates a partially sectioned
side elevation view of an assembly of tubular composite
laminate joint structures used to mechanically join
and seal pressure pipe which was tested to demollstrate
that the pipe and coupling meets or exceeds: (a) the
performance requirements for water pipe established
-15-
1~297B;~
by American ~-'ater l~orks Association (A~ A) and the
American ~Jational Standards Institute (ANSI) in the
AWWA Standard ANSI/A~'WA C950-81, (b) the specification
requirements for line pipe, casing and tubing
established by American Petroleum Institute in API
Spec SLR and API Spec 5Ar, and (c) the design and
test criteria for pressure piping established by the
American Society of Mechanical Engineers in ASME Code
B31.3 and B31.q.
The pressure pipe joint detail depicted in
FIG 5 depicts a means of connecting two lengths of
filament wound composite Reinforced Thermosetting
Resin Pipe (RTRP), cach length of which have iden~ical
pipe joint ends 10, sealed by a pair of rubber "O"
rings 9 positioned on a 4 inch long reinforced plastic
tubular seal sleeve structure 8 having a wall thickness
of approximately 0.31 inches and an inner diameter
equal to that of the pipe joint ends 10 Each joint
end of the composite filament wound pipe comprised
an inner impermeable liner 4 approximately 0.1 inch
thick made of a glass fiber reinforced thermosetting
vinylester resin which extended the full length of
the pipe and which served as the sealing surface
against which each rubber "O" ring seal 9 was
compressed.
A first ply of continuous CIRC filament
strands 2 was filament wound upon the liner structure
4 of each pipe to a minimum wall thickness of approxi-
mately 0.06 inches and enlarged at each pipe end to
provide a conical laminate ply support s~rface
having an angle of approximately 8 with respect to
the pipe longitudinal axis.
A second ply comprising continuous LO~GO
filament strands 1 was transversely disposed upon
the first ply CIRC filament strands to provide a
LO~'GO ply laminate having a uniform thickness of
approximately 0.09 inches and flared at the pipe ends
~X297~
at a taper angle approximately equal to that of the
first ply joint structure. The across strand
shear path of the resulting flared LONGO ply laminate
was calculated to equal 0.65 inches or approximately
seven times the LONGO ply laminate thickness thereby
enabling a joint tenslle load at least equal to 5000
pounds per inch of pipe circumference to be resisted
by the continuous longitudinally directed filament
strands cornprising the second ply laminate.
0 A third ply comprising continuous CIRC
filament strands 3 was filament wound upon the
second ply LONGO strands to tension and compress the
LONGO filament strands against the first ply tubular
structure. The filament wound thickness of the third
ply laminate was approximately 0.12 except for the
pipe joint ends where the third ply filament strands
3 were configured to form a 3 inch wide cylindrically
shaped flange having a load bearing annular plane
surface extending approximately 0.25 inches above the
pipe outer wall surface.
After the pipe ends were mated with the
seal sleeve structure 8 the two piece segmented
composite coupling structure 7 was positioned to
engage and secure the abutting flanges of each pipe
end. The segmented coupling structure 7 shown
in FIG. 5 in a partially sectioned side elevation
view comprises a first ply of continuous filzment
CIRC strands 2s filament wound upon a removable
segmented coupling forming structure and configured
at each end to have a tapered laminate support surface
having a taper angle a of approximately 15. A
second ply of continuous filament LONGO strands 1s
was then transversely disposed upon the segrnented
coupler first ply filament strands. A third ply of
continuous filament strands 3s was afterwards filament
wound upon the segmented coupler second ply LONGO
strands to simultaneously tension and compress the
~297~3
LONGO filament strands against the segmented coupler
first ply support structure. A sufficient thickness
of third ply filament strands was filament wound
upon the segmented coupler second ply filament strands
to provide a cylindrically shaped segmented coupllng
structure having a uniform outer surface diameter.
The outer surface of the two piece segrnented coupling
structure 7 was then covered with a resin impregnated
woven fabric comprised of filament reinforcements to
provide an improved structural integrity to the
segmented coupling structure.
After the two piece coupling structure was
positioned to engage the pair of pipe end flanges,
a cylindrical filament wound tubular lock sleeve 6
having an inner diameter slightly larger that the outer
diameter of the segmented coupling structure was
slipped over the coupling halves to secure and lock
the segmented coupling structure in a position
that enabled the coupling structure to resist the
tensile forces applied to the pipe joint structure.
Example III
FIG. 6 is an exploded view of a composite
pipe joint and segmented coupling structure similar
to that illustrated in FIG. 5 except that the exterior
third ply flange structure 3 of each pipe joint end
is configured to have an annular groove to retain an
"O" ring seal 9 and the sealing sleeve structure 8
has an inner bore diameter designed to compress the
pair of rubber "O" rings to provide a satisfactory
pressure seal. Each of the tubular multiple ply
composite laminate structures 10 were constructed in
a manner similar to that illustrated in FIG. 4
inasmuch as the first plyilaminate support structure
w,asnOt recessed to accept a sealing sleeve. The
two piece seqmented coupling 7 illustrated in FIG. 6
is similar to that illustrated in FIG. S except it
has a larger outer diameter to enable it to accomodate
a sealing sleeve, 8, positioned upon the pipe joint
-18-
12:~97~,3
flanges comprised of filament wo~nd third ply
continuous filament CIRC strands 3. The lock sleeve
6 shown in FIG. 6 was also required to have a larger
diameter for a given pipe size than the lock sleeve
shown in FIG. 5 and was provided with a pair of
threaded lock bolts 11 to prevent the lock sleeve
from being moved.
