Note: Descriptions are shown in the official language in which they were submitted.
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Turbomachine blade having complementary asymmetrical geometry
Background of the invention
The invention relates to turbomachine blades made of
composite material including a fiber reinforcement densified
by a matrix.
The intended field is that of gas turbine blades for
aeroengines or industrial turbines.
The fabrication of turbomachine blades of composite
material has already been proposed. Reference can be made in
particular to international patent application
PCT/FR2009/052309 filed jointly by SNECMA and SNECMA
Propulsion Solide. This application describes the fabrication
of a turbomachine blade made of composite material including a
fiber reinforcement densified by a matrix. More precisely,
this method exhibits the feature that the fiber blank
fabricated by three-dimensional weaving is shaped to obtain a
one-piece fiber preform having a first portion constituting an
airfoil and blade root preform and at least one second portion
constituting an inner platform and blade outer platform
preform. Thus, after densification of the preform, it is
possible to obtain a blade made of composite material having a
fiber reinforcement consisting of the preform and densified by
the matrix, and forming a single piece with integrated inner
platform and/or outer platform.
The blade obtained by such a method has the
disadvantage that its outer platform cannot integrate both a
function of sealing (through the presence of wipers) to the
housing which surrounds the blades and an aerodynamic function
(by the presence of covering spoilers defining the outside of
the flowpath of the gas stream in the turbine).
French patent application No. 09 58931 filed jointly
by SNECMA and SNECMA Propulsion Solide, describes the
fabrication of a blade made of composite material forming a
single piece with integrated inner platform and outer
platform, the outer platform providing both the sealing
function and the aerodynamic function.
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However, the fabrication of such an outer platform
with the method described in French patent application No. 09
58931 involves in particular shaping and molding operations
with two-layer fiber structures, operations which are
completely feasible but which can be more complex to carry out
than with single-layer structures. In addition, the blade thus
fabricated does not incorporate an anti-tilting wall.
Further, in the event of damage to the outer platform
of the blade fabricated according to the method described in
French patent application No. 09 58931, the aerodynamic
function and the sealing function are both impacted because
the outer platform is formed in a single piece providing both
functions.
Object and summary of the invention
It is therefore desirable to be able to have blades
available made of composite material, particularly but not
necessarily of thermostructural composite material such as
CMC, for turbines or compressors of turbomachinery, blades
that are relatively simple to fabricate and which integrate
the required functions, namely the sealing, flowpath
definition (aerodynamic function), and anti-tilting functions.
To this end, according to the present invention, a
method is proposed for fabricating a turbomachine blade made
of composite material including a fiber reinforcement
densified by a matrix, the method including:
- fabrication by three-dimensional weaving of a one-
piece fiber blank,
- shaping of the fiber blank to obtain a one-piece
fiber preform having a first portion constituting an airfoil
and blade root preform, the blade airfoil exhibiting two faces
each connecting a leading edge and a trailing edge, and at
least one second portion present only on one of the faces of
the blade airfoil, said second portion constituting a preform
of a portion of at least one of the following elements: blade
inner platform, blade anti-tilting wall, blade outer platform
spoilers and blade outer platform wipers,
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densification of the preform by a matrix to obtain a
blade made composite material having a fiber reinforcement
consisting of the preform and densified by the matrix, and
forming a single piece with at least a portion of one of the
following elements: blade inner platform, blade anti-tilting
wall, blade outer platform spoilers and blade outer platform
wipers.
Compared with the method described in patent
application No. 09 58931, the invention provides for providing
each of these functions of flowpath definition, sealing, and
anti-tilting by distinct portions of the blade which are
fabricated from single-layer structures. The blade thus
fabricated exhibits a complementary asymmetrical geometry,
providing on one side of its airfoil (pressure face or suction
face) the sealing function with a portion of blade outer
platfrom wipers, the flowpath definition function with
portions of an inner platform and of a blade outer platform
spoiler and the anti-tilting function with a portion of an
anti-tilting wall. This asymmetrical geometry allows several
identical airfoils to be interleaved in order to provide the
required functions on each side of their airfoil.
According to an advantageous feature of the method, in
the longitudinal direction of the fiber blank corresponding to
the longitudinal direction of the blade to be fabricated, the
fiber blank includes a first set of several layers of yarns
which are interlinked to form a first portion of the blank
corresponding to the airfoil and blade root preform, and a
second set of several layers of yarns which are interlinked at
least locally to constitute on one of the faces of the blade
airfoil at least the second portion of the blank corresponding
to a preform of a portion of at least one of the following
elements: blade inner platform, anti-tilting wall, blade outer
platform spoilers and blade outer platform wipers, the yarns
of the first set of yarn layers not being linked to the yarns
of the second set of yarn layers, and the first set of yarn
layers having yarns of the second set of yarn layers crossing
through it at the or each second portion of the blank.
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The provision of unlinked areas allows shaping of the
fiber preform without cutting linking yarns, such a cut
possibly reducing the mechanical strength of the fiber
reinforcement, hence of the fabricated blade.
According to one embodiment of the invention, in the
longitudinal direction corresponding to the longitudinal
direction of the fiber blank to be fabricated, the fiber blank
includes:
- a first set of several layers of yarns which are
interlinked to form a first portion of the blank corresponding
to the preform of the airfoil and the blade root;
- a second set of several layers of yarns which are
interlinked at least locally to form on one of the faces of
the airfoil at least one second portion of the blank
corresponding to the preform of a portion of blade inner
platform and/or of blade outer platform spoilers and at least
one third portion of the blank corresponding to the preform of
a portion of blade anti-tilting wall and/or of blade outer
platform wipers;
the yarns of the first set of yarn layers not being
linked to the yarns of the second set of yarn layers, and
the first set of yarn layers having yarns from the
second set of yarn layers crossing through it at the or at
each second portion of the fiber blank and at the or at each
third portion of the fiber blank.
In this case, the fiber blank is woven with a second
continuous set of yarn layers and the shaping of the fiber
blank includes the elimination by cutting out of portions of
the second set of yarn layers outside of the or each second
portion of the fiber blank and the or each third portion of
the fiber blank.
According to another embodiment of the invention, in
the longitudinal direction corresponding to the longitudinal
direction of the fiber blank to be fabricated, the fiber blank
includes:
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- a first set of several layers of yarns which are
interlinked to form a first portion of the blank corresponding
to the airfoil and blade root preform;
- a second set of several layers of yarns which are
5 interlinked at least locally to form on one of the
surfaces of the airfoil at least one second portion of
the blank corresponding to the preform of a portion of
at least one of the following elements: blade inner
platform, blade anti-tilting wall, blade outer platform
spoilers and blade outer platform wipers and a third
portion of the blank corresponding to the preform of
all or a portion of one of said elements other than
that formed by the second portion; and
- a second set of several layers of yarns which are
interlinked at least locally to form on one face of the
airfoil at least one fourth portion of the blank corresponding
to the preform of all or a portion of one of said element
other than that formed by the second and third portions and a
fifth portion of the blank, an element corresponding to the
preform of all or part of said elements other than that formed
by the second, third and fourth portions;
the yarns of the first set of yarn layers not being
linked to the yarns of the second and third sets of yarn
layers, and
the first set of the yarn layers having yarns from the
second and third sets of yarn layers crossing through it at
second, third, fourth and fifth portions of the fiber blank.
In this case, the fiber blank is woven with a second
and a third continuous sets of yarn layers and the shaping of
the fiber blank includes the elimination by cutting out of
portions of the second and third sets of yarn layers outside
of the second, third, fourth and fifth portions of the fiber
blank.
According to yet another feature of the method, in the
first portion of the fiber blank and in a direction
corresponding to that extending along the profile of an
airfoil of variable thickness in the blade to be fabricated,
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the number of yarn layers in the first set of yarn layers is
constant. The yarns of the first set of yarns can then have
variable weight and/or count.
Advantageously, a strip is fabricated by three-
dimensional weaving that includes a succession of fiber
blanks. These can then be cut out of the strip. The blanks can
be woven with the longitudinal direction of the blade to be
fabricated in the weft direction or in the warp direction.
According to the present invention, a turbomachine
blade of composite material is also proposed including a fiber
reinforcement obtained by three-dimensional weaving of yarns
and densified by a matrix, the blade including a first portion
constituting an airfoil and a blade root, the blade airfoil
exhibiting two faces each connecting a leading edge to a
trailing edge, the first portion forming a single piece with
at least one second portion present only on one of the faces
of the blade airfoil, the second portion constituting a
portion of at least one of the following elements: blade inner
platform, blade anti-tilting wall, blade outer platform
spoilers and blade outer platform wipers, the portions of the
fiber reinforcement corresponding to the first and the second
portions of the blade being at least partially mutually
nested, with yarns of the first portion of the fiber
reinforcement penetrating into the second portion of the fiber
reinforcement.
According to one embodiment of the invention, the
second portion constitutes a portion of one of the following
elements: blade inner platform, blade anti-tilting wall, blade
outer platform spoilers and blade outer platform wipers, the
first portion also forming a single piece with at least one
third portion constituting a portion of at least one of said
elements other than that constituted by the second portion,
the third portion being present only on one face of the
airfoil, the portions of the fiber reinforcement corresponding
to the first, second and third portions of the blade being at
least partly mutually imbricated, with yarns of the first
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portion of the fiber reinforcement penetrating into the second
and third portions of the fiber reinforcement.
In this case, the first portion can also form a single
piece with at least one fourth portion constituting a portion
of at least one of said elements other than that constituted
by said second and third portions, the fourth portion being
present only on one face of the airfoil, the portions of the
fiber reinforcement corresponding to the first, second, third
and fourth portions of the blade being at least in part
mutually imbricated, with yarns of the first portion of the
fiber reinforcement penetrating into the second, third and
fourth parts of the fiber reinforcement.
The first part can also form a single piece with at
least one fifth portion constituting a portion of at least one
of said elements other than that constituted by said second,
third, and fourth portions, said fifth portion being present
only on one face of the airfoil, the portions of the fiber
reinforcement corresponding to the first, second, third,
fourth and fifth portions of the blade being at least in part
mutually imbricated, with yarns of the first portion of the
fiber reinforcement penetrating into the second, third, fourth
and fifth portions of the fiber reinforcement.
According to another embodiment, the second portion
constitutes a portion of one of the following elements: blade
inner platform, blade anti-tilting wall, blade outer platform
spoilers and blade outer platform wipers, the first portion
also forming a single piece with at least one third portion
constituting all or a portion of at least one of said elements
other than that constituted by said second portion, the
portions of the fiber reinforcement corresponding to the
first, second, and third portions of the blade being at least
partly mutually imbricated, with yarns of the first portion of
the fiber reinforcement penetrating into the second and third
portions of the fiber reinforcement.
The blade can be made of a ceramic matrix composite
material.
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According to one feature of the blade, the yarns
constituting the portion of the fiber reinforcement
corresponding to the second, third, fourth and/or fifth
portions of the blade cross through the portion of the fiber
reinforcement corresponding to the first portion of the blade.
The blade airfoil can have a variable thickness
profile along which the portion of the fiber reinforcement
corresponding to the first portion of the blade has, in the
longitudinal direction of the blade, a constant number of yarn
layers having a variable weight and/or count, or a variable
number of yarn layers.
The invention also has as its object a turbomachine
rotor or disk and a turbomachine equipped with a blade as
defined earlier.
Brief description of drawings
The invention will be better understood from the
description given hereafter, by way of indication but without
limitation, with reference to the appended drawings in which:
- Figure 1 is a perspective view of a turbomachine
blade in conformity with one embodiment of the invention;
- Figures 2A through 2C are enlarged views of portions
of the blade of Figure 1;
- Figure 3 illustrates very schematically the
arrangement of three sets of yarn layers in a three-
dimensionally woven fiber blank designed for the fabrication
of a fiber preform for a blade such as that illustrated by
Figure 1;
- Figures 4, 5 and 6 illustrate successive fabrication
steps of a fiber preform for a blade such as that illustrated
by Figure 1, starting with the fiber blank of Figure 3;
- Figure 7 is a section view showing the flattened
profile of a blade airfoil such as that of Figure 1;
- Figure 8 is a section view of a set of warp yarn
layers making it possible to obtain a profile such as that of
Figure 7;
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Figures 9A and 9B are section views showing a method
of weaving the fiber blank of Figure 3;
- Figures 10A and 10B are partial section views in a
plane parallel to the warp and weft directions in a portion of
the fiber blank of Figure 3 corresponding to the junction
location between, on the one hand, the airfoil and a portion
of blade anti-tilting wall and, on the other hand, between the
airfoil and a portion of blade inner platform;
- Figure 10C is a partial weft section view in a
portion of the fiber blank of Figure 2 corresponding to the
junction location between the airfoil and portions of blade
anti-tilting wall and of portions of blade inner platform;
- Figures 11A and 11B are partial section views in a
plane parallel to the warp and weft directions in a portion of
the fiber blank of Figure 3 corresponding to the junction
location between, on the one hand, the airfoil and a portion
of blade outer platform spoiler and, on the other hand,
between the airfoil and a portion of blade outer platform
wipers;
- Figure 11C is a partial weft section view in a
portion of the fiber blank of Figure 2 corresponding to the
junction location between the airfoil and portions of blade
anti-tilting wall and a portion of blade inner platform;
- Figure 12A is a weft section view showing an example
of arrangement of weft yarns in a portion of the fiber blank
corresponding to a portion of the airfoil root;
- Figures 12B to 12D are weft section views showing
warp planes for an example of three-dimensional (multilayer)
weaving in the fiber blank portion of Figure 12A;
- Figure 13 is a partial schematic section view
showing another embodiment of a portion of the blank
corresponding to an airfoil root;
- Figures 14 and 15 illustrate very schematically two
embodiments of a woven fiber strip obtained by three-
dimensional weaving including a plurality of fiber blanks like
that of Figure 3;
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Figure 16 indicates successive steps in an
embodiment of a fabrication method for a turbomachine blade in
conformity with the invention;
- Figure 17 indicates successive steps of another
5 embodiment of a fabrication method for a turbomachine blade in
conformity with the invention;
- Figure 18 shows the mounting onto a turbomachine
rotor of a plurality of blades similar to that of Figure 1;
and
10 - Figure 19 is a perspective view of a turbomachine
blade in conformity with another embodiment of the invention.
Detailed description of embodiments
The invention is applicable to different types of
turbomachine blades having integrated inner platforms and/or
outer platforms, particularly compressor and turbine blades of
different gas turbine spools, for example a low pressure
turbine (BP) rotor blade like that illustrated by Figure 1.
The blade 10 of Figure 1 includes, in well-known
fashion, an airfoil 20, a root 30 constituted by a portion
having greater thickness, having for example a bulb-shaped
section, continuing in a tang 32. The airfoil 20 extends in
the longitudinal direction between its root 30 and its tip 21
and shows in cross-section a dished profile with variable
thickness defining two faces 22 and 23, corresponding
respectively to the suction face and to the pressure face of
the airfoil 20 and each connecting the leading edge 20a and
the trailing edge 20b of the last mentioned.
The blade 10 is mounted on a turbine rotor (not
illustrated) by insertion of the root 30 into a recess of
matching shape provided at the periphery of the rotor.
In conformity with one embodiment of the invention,
the airfoil 20 also includes four distinct elements
respectively constituting a blade inner platform 40 portion, a
blade anti-tilting wall 50 portion, a blade outer platform
spoilers 60 portion and a blade outer platform wipers 70
portion.
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More precisely, at its radially inward end and on its
face 22, the airfoil 20 connects to the blade inner platform
40 portion the outer (or upper) surface 42 whereof defines,
radially inward, the flowpath of a gas stream f. In its
upstream and downstream end portions (in the flow direction f
of the gas stream), the platform 40 portion ends in covering
spoilers 44 and 46. In the example illustrated, the surface 42
of the platform portion is tilted, generally forming a nonzero
angle relative to the normal to the longitudinal direction of
the blade. Depending on the desired profile of the inner
surface of the gas stream flowpath, the angle could be zero,
or the surface 42 could have a generally non-rectilinear
profile, dished for example.
Still at its radially inward end but on its face 21,
the blade 20 connects to the anti-tilting wall 50 portion
which comprises flanks 51 and 52 at its upstream and
downstream ends capable of preventing tilting of the blade
when the latter is mounted on a turbine rotor.
The airfoil 20 also connects at its radially outward
end and on its face 22 to the blade outer platform spoiler 60
portion which defines on its inner (lower) surface 61,
radially outward, the flowpath of the gas stream f (Figures 1
and 2C). In its upstream and downstream end portions, the
blade outer platform spoiler 60 portion ends in covering
spoilers 62 and 63. In the example illustrated, the surface 61
of the blade outer platform spoiler 60 portion exhibits a
tilted rectilinear profile generally forming a nonzero angle
relative to the normal to the longitudinal direction of the
blade or the surface 61 (Figure 2B). As a variant, depending
on the desired profile of the outer surface of the gas stream
flowpath, the surface 61 could have a generally non-
rectilinear profile, dished for example, and/or extend
substantially perpendicularly to the longitudinal direction of
the blade.
Still at its radially outward end but on its face 21,
the airfoil connects to the blade outer platform wipers 70
portion. On its outer (upper) surface 72, the blade outer
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platform wipers 70 portion defines a depression or bathtub 73
(Figures 1 and 2A). Along the upstream and downstream edges of
the bathtub 73, the portion 70 carries wipers 74 and 75 having
a tooth-shaped profile the tips whereof can penetrate into a
layer of abradable material of a turbine ring (not shown) to
reduce the clearance between the blade tip and the turbine
ring.
As illustrated in Figure 1, the blade inner platform
40 portion, the blade anti-tilting wall 50 portion, the blade
outer platform spoilers 60 portion and the blade outer
platform wipers 70 portion are respectively present only on
one of the faces of the airfoil. In other words, the face of
the airfoil opposite that comprising one or more of these
elements lacks the or these same elements. Thus, the functions
of defining (radially outside) the flowpath and of anti-
tilting customarily performed by one and the same element
present at the radially inward end of the airfoil are
performed, in the blade of the invention, by distinct elements
to wit, in the example described here, by the blade inner
platform 40 portion and the blade anti-tilting wall 50
portion. Likewise, the flowpath definition and tilting seal
customarily performed by one and the same element present at
the radially outward end of the airfoil are performed, in the
blade of the invention, by distinct elements to wit, in the
example described here, by the blade outer platform spoilers
60 portion and the blade outer platform wipers 70 portion.
Figure 3 shows very schematically a fiber blank 100
starting with which a fiber blade preform can be shaped in
order to obtain, after densification by a matrix and possible
machining, a blade made of composite material with integrated
inner platform, anti-tilting wall, blade outer platform
spoilers and wipers portions like that illustrated in
Figure 1.
The blank 100 includes two portions 102 and 104
obtained by three-dimensional weaving or multilayer weaving,
only the envelopes of these three portions being shown in
Figure 3. The portion 102 is designed, after shaping, to
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constitute a portion of a fiber blade preform corresponding to
an airfoil and blade root preform. The portion 104 is
designed, after shaping, to constitute the portions of the
fiber blade preform corresponding to preforms of the blade
anti-tilting portion, the blade outer platform wiper portion,
the blade inner platform portion and the blade outer platform
spoilers portion.
The two portions 102 and 104 are in the form of strips
extending generally in a direction X corresponding to a
longitudinal direction of the blade to be fabricated. The
fiber strip 102 exhibits, in its portion designed to
constitute an airfoil preform, a variable thickness determined
according to the thickness of the profile of the airfoil of
the blade to be fabricated. In its portion designed to
constitute a root preform, the fiber strip 102 exhibits an
extra thickness 103 determined according to the thickness of
the root of the blade to be fabricated.
The fiber strip 102 has a width 1 selected according
to the length of the developed (flattened) profile of the
airfoil and the root of the blade to be fabricated while the
fiber strips 104 and 106 each have a width L greater than 1
selected according to developed lengths of the blade anti-
tilting wall, inner platform, blade outer platform spoilers
and wipers portions to be fabricated.
The fiber strip 104 has a substantially constant
thickness determined according to the thicknesses of the anti-
tilting wall, inner platform and outer platform spoiler and
wiper portions of the blade to be fabricated. The strip 104
includes a first portion 104a, which extends along and in the
vicinity of a first surface 102a of the strip 102 designed to
constitute the pressure face of the airfoil, a second portion
104b, which extends along and in the vicinity of the second
surface 102b of the strip 102 designed to constitute the
suction face of the airfoil, and a third portion 104c which
extends along and in the vicinity of the first surface 102a of
the strip 102.
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The portions 104a and 104b of the strip 104 are linked
by a connecting portion 140c which extends transversely
relative to the strip 102 at a location corresponding to that
of the anti-tilting wall portion and the inner platform
portion of the blade to be fabricated.
The portions 104b and 104c of the strip 104 are linked
by a connecting portion 150c which extends transversely
relative to the strip 102 at a location corresponding to that
of the outer platform wiper portion and of the outer platform
spoiler portion of the blade to be fabricated.
Depending on the desired geometry at the outer
platform wiper portion of the blade, at the blade outer
platform spoiler portion, at the anti-tilting wall portion and
at the blade inner platform portion, the connecting portions
140c and 150c can cross through the strip 102, entering and/or
emerging, substantially perpendicularly to the longitudinal
direction X of the blank or following a curved profile as
described hereafter in relation to Figures 10A, 10B, 11A and
11B. As described in more detail later, the strips 102 and 104
are simultaneously woven by three-dimensional weaving, with no
linkage between the strip 102 and the portions 104a, 104b and
104c of the strip 104 by continuously weaving a plurality of
successive blanks 100 in the X direction.
Figures 4 through 6 show very schematically how a
fiber preform having a shape close to that of the blade to be
fabricated can be obtained starting with the fiber blank 100.
The strip 102 is cut at one end in the extra thickness
103 and at another end slightly beyond the connecting portion
150c to obtain a strip 120 with a length corresponding to the
longitudinal dimension of the blade to be fabricated with a
swollen portion 130 constituted by a portion of the extra
thickness 103 and situated at a location corresponding to the
position of the root of the blade to be fabricated.
In addition, cutouts are made at the ends of the
portions 104a and 104c of the strip 104 and in the portion
104b thereof so as to free independent segments 140a and 140b
extending to either side of the connecting portion 140c as
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well as independent segments 150a and 150b on either side of
the connecting portion 150c, as shown in Figure 4.
The lengths of the portions 140a, 140b, 150a and 150b
are determined according to the lengths of the inner platform,
5 anti-tilting wall, outer platform spoilers and outer platform
wipers portions in the blade to be fabricated.
Due to the absence of linkage between the strip 102
and the portions 104a, 104b and 104c of the strip 104, the
portions 140a, 140b, 150a and 150b can be folded back
10 perpendicularly to the strip 102 without cutting yarns so as
to form plates as shown in Figure 5.
A fiber preform 200 of the blade to be fabricated is
then obtained by molding with deformation of the strip 102 to
reproduce the dished profile of the blade airfoil. The
15 portions 140a and 140b are also deformed to reproduce shapes
similar respectively to that of the inner platform portion of
the blade (with its covering spoilers in particular) and to
that of the anti-tilting wall portion of the blade. Likewise,
the portions 150a and 150b are deformed to reproduce shapes
similar respectively to that of blade outer platform spoilers
portion and to the outer platform wipers portion of the blade
(see Figure 5). A preform 200 is thus obtained having an
airfoil preform portion 220 including a surface 220a designed
to constitute the pressure face of the airfoil and a surface
220b designed to constitute the suction face of the airfoil,
root preform portion 230 (with tang preform), an inner
platform portion preform portion 240, an anti-tilting wall
portion preform portion 250, a blade outer platform covering
spoilers portion preform portion 260 and an outer platform
wipers portion preform portion 270 (Figure 6).
As described later, the steps in fabricating a blade
preform starting with a fiber blank are advantageously carried
out after treatment of the fibers of the blank and its
impregnation with a consolidation composition.
A three-dimensional weaving method for the fiber blank
100 will now be described in greater detail.
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It is assumed that the weaving is carried out with
warp yarns extending in the longitudinal direction X of the
blank, it being specified that weaving with the weft yarns in
this direction is also possible.
The variation in thickness of the strip 102 over its
length is obtained by using warp yarns having variable weight.
As a variant or a supplement it is possible to vary the count
of the yarns (number of yarns per unit of length in the weft
direction), a smaller count allowing greater thinning during
shaping of the preform by molding.
Thus, to obtain a blade airfoil profile as shown in
flat projection in Figure 7, 3 layers of warp yarns can be
used with variable weight and count as illustrated in
Figure 8.
In one example of implementation, the yarns used can
be silicon carbide (SiC) yarns supplied under the name
"Nicalon" by the Japanese company Nippon Carbon and having a
weight (number of filaments) of 0.5K (500 filaments).
The warp is made with 0.5K SiC yarns and 1K SiC yarns
obtained by the combination of two 0.5K yarns, the two yarns
being combined by covering. Covering is carried out
advantageously with filament of a temporary nature capable of
being eliminated after weaving, for example a polyvinyl
alcohol (PVA) filament that can be eliminated by dissolving in
water.
Table I below gives, for each column of warp yarns,
the count (number of yarns/cm over the length of the profile),
the number of 0.5K yarns, the number of 1K yarns and the
profile thickness in mm, the latter varying between
approximately 1 mm and 2.5 mm:
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Table I
Column 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Count 6 6 6 6 6 6 6 8 8 8 8 8 8 8 8 8 8 8 6
No of 0.5K 3 3 3 3 3 3 3 2 1 0 0 0 0 0 0 0 2 1 3
yarns
No of 0 0 0 0 0 0 0 1 2 3 3 3 3 3 3 3 1 2 0
2x0 .5K
yarns
Thickness 1 1 1 1 1 1 1.2 1.5 2 2.2 2.4 2.5 2.4 2.4 2.2 2.1 1.8 1.5 1.2
Naturally, depending on the weights of the available
yarns, different combinations of numbers of yarn layers and of
variations of count and of weight can be adopted for the
profile to be obtained.
Figures 9A, 9B show, in warp section, two successive
plans of a weave which can be used for weaving the fiber blank
100 of Figure 3 outside the extra thickness 103.
The strip 102 of the fiber blank 100 includes a set of
warp yarn layers, the number of layers being here for example
equal to 3 (layers C11, C12, C13) . The warp yarns are linked by
weft yarns t1 by three-dimensional weaving.
The strip 104 also includes a set of warp yarns for
example identically equal to 3 (layers C21, C22, C23) linked by
weft yarns t2 by three-dimensional weaving, like the strip
102.
It is noted that the weft yarns t1 do not extend into
the layers of warp yarns of the strip 104, that the weft yarns
t2 do not extend into the layers of warp yarns of the strip
102 in order to leave them unlinked.
In the example illustrated, the weaving is multilayer
weaving performed with a satin or multi-satin type weave.
Other types of three-dimensional weaving can be used, for
example multilayer weaving using a multiple plain weave or
weaving with an "interlock" type weave. What is meant here by
"interlock" weaving is a weave wherein each layer of weft
yarns links several layers of warp yarns with all the yarns of
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a given warp column having the same path in the plane of the
weave.
Different methods of three-dimensional weaving are
described in particular in document WO 2006/136755.
Figures 10A and IOB are section views parallel to the
warp and weft directions at the crossing of the strip 102
respectively by the connecting portions 140c and 150c of the
strip 104 of the fiber blanks of Figure 3. Figure 10A shows
the entry of the warp yarns into the strip 104 on the side of
the surface 102a (pressure face) of the strip 102 at the
connecting portion 140c. At this location, each layer of warp
yarns of the strip 104 (here layers C21, C22, C23) penetrates
between the weft yarns t1 of the strip 102 following a dished
profile such as that shown in Figure 10A.
Figure IOB shows the emergence of the warp yarns in
the strip 104 on the side of the surface 102b (suction face)
of the strip 102 at the connection portion 140c. At this
location, each layer of warp yarns of the strip 104 (here
layers C21, C22, C23) emerge between the weft yarns t1 of the
strip 102 following a dished profile such as that shown in
Figure 10B.
Naturally, depending on the desired shape of the anti-
tilting wall portion and of the inner blade platform portion,
the layers of warp yarns of the strip 104 can enter and emerge
from the strip 102 with different profiles such as rectilinear
profiles for example.
The crossing of the strip 104 from one side to the
other of the strip 102 is achieved, during weaving, by having
each warp yarn of the strip 104 individually cross through all
the warp and weft yarns of the strip 102.
Figure 10C is a weft section view at the crossing of
the strip 102 by the connecting portion 140c of the strip 104.
It is observed that the layers of warp yarns of the strip 104
(here layers C21, C22, C23) , and of course the weft yarns t1 of
the strip 104, will not re-emerge from the strip 102 at the
same place as that of their entry into the strip 102. Indeed,
between their entry (on the side of the face 102a) into the
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strip 102 and their emergence (on the side of the face 102b),
the warp yarns of the strip 104 are held within the strip 102
over a distance d1 which makes it possible to form the offset
between the portions 104a and 104b at the connecting portion
140c (Figure 3) . This offset makes it possible to form, as
illustrated in Figure 1, a blade inner platform portion 40
which is above the anti-tilting wall portion 50 in the
direction of the airfoil 20.
Figures 11A and 11B are section views parallel to the
warp and weft directions at the crossing of the strip 102 by
the connecting portion 150c of the strip 104 of the fiber
blank of Figure 3. Figure 11A shows the entry of the warp
yarns into the strip 104 on the side of the face 102b (suction
face) of the strip 102 at the connecting portion 150c. At this
location, each layer of warp yarns of the strip 104 (here
layers C21, C22, C23) penetrates between the weft yarns t1 of
the strip 102 following a dished profile such as that shown in
Figure 11A.
Figure 11B shows the emergence of the warp yarns in
the strip 104 on the side of the face 102a (pressure face) of
the strip 102 at the connecting portion 150c. At this
location, each layer of warp yarns of the strip 104 (here
layers C21, C22, C23) emerge between the weft yarns t1 of the
strip 102 following a dished profile such as that shown in
Figure 11B.
Of course, depending on the desired shape of the blade
outer platform spoiler portion and of the blade outer platform
wipers portion, the layers of warp yarns of the strip 104 can
enter and emerge from the strip 102 with profiles having
different shapes such as rectilinear profiles for example.
Figure 11C is a weft section view at the crossing of
the strip 102 by the connecting portion 150c of the strip 104.
It is observed that the warp yarn layers (here layers C21, C22,
C23) of the strip 104, and of course the weft yarns t1 of the
strip 104, will not emerge from the strip 102 at the same
location as that of their entry into the strip 102. Indeed,
between their entry (on the side of the face 102b) into the
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strip 102 and their emergence (on the side of the face 102a),
the warp yarns of the strip 104 are held within the strip 102
over a distance d2 which allows the creation of the offset
between the portions 104b and 104c at the connecting portion
5 150c (Figure 3) . This offset makes it possible to form, as
illustrated in Figure 1, a blade outer platform wipers portion
70 which is above the blade outer platform spoiler portion 60
in the direction of the airfoil 20.
The extra thickness 103 can be obtained by using warp
10 yarns having greater weight and additional layers of weft
yarns.
In Figure 12A, the number of layers of weft yarns
changes in this example from 4 to 7 between a portion 1021 of
the strip 102, corresponding to the tang of the blade, and the
15 portion 1023 of the strip 102 having the extra thickness 103.
In addition, weft yarns t1, t'1, t"1 having different
weights are used, the yarns tl being for example "Nicalon" SiC
yarns of 0.5K weight (500 filaments), the yarns t'1 being
obtained by the combination of two 0.5K yarns and the yarns
20 t"1 by the combination of three 0.5K yarns.
The weaving in the blank portion 1023 necessitates
layers of warp yarns in greater number than in the portion
1021. This is advantageously achieved during transition
between the portion 1021 and the portion 1023 by reducing the
number of warp planes by constituting each warp plane in the
portion 1023 by combining warp yarns from two warp planes of
the portion 1021. Figures 12B and 12C show two neighboring
warp planes in the portion 1021 and Figure 12D shows a warp
plane obtained in the portion 1023 by combination of the warp
planes of Figures 12B and 12C. In Figures 12B, 12C and 12D,
the different weights of the warp yarns (as shown in Figure 8)
or of the weft yarns are not shown for the sake of simplicity.
Between Figures 12B, 12C, on the one hand, and Figure 12D, on
the other hand, the dashes show how the warp yarns of the
different layers in Figures 12B, 12C form the layers of warp
yarns of Figure 12D.
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Of course, different combinations of numbers of weft
layers and of weft yarn weights can be adopted to form the
extra thickness 103.
According to another embodiment shown schematically in
Figure 13, the extra thickness 103 can be obtained by
introducing an insert during weaving of the strip 102.
In Figure 13, the set T1 of weft yarn layers of the
portion 1021 of the strip 102 corresponding to the tang of the
blade is divided by omitting linking during weaving into two
subsets T11, T12 between which an insert 1031 is inserted. In
the example illustrated, the portion 1021 has a greater
thickness than of the portion 1022 of the strip 102
corresponding to the blade airfoil. The transition between the
1022 and the portion 1021 can be made in the same manner as
described above for the transition between the portions 1021
and 1023 of Figure 12A. The crossing of the strip 102 by the
strip 104 and at the connecting portion 140c of Figure 3 can
optionally be performed through the thickened portion 1021.
At the end of the insert 103, opposite the portion
1021, the subsets T11, T12 of weft yarn layers are once again
reunited by weaving to form a portion 1021 having the same
thickness as the portion 1021r then, by thickness reduction, a
portion 102'2 having the same thickness as the portion 1022,
the portion 102'2 forming the portion corresponding to a blade
airfoil for the following woven blank.
The insert 1031 is preferably made of monolithic
ceramic, preferably the same ceramic material as that of the
matrix of the composite material of the blade to be
fabricated. Thus, the insert 1031 can be a block of SiC
obtained by sintering SiC powder.
As shown very schematically by Figure 14, a plurality
of fiber blanks 100 can be obtained by weaving a strip 300
wherein are formed one or more rows of successive fiber
blanks. Extra-length areas 310, 320 are provided in the warp
direction (warp yarns only) and in the weft direction (weft
yarns only) to avoid edge effects connected with weaving, to
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leave more freedom to deform during shaping of the preform and
to provide transition areas between blanks 100.
Figure 15 shows a variant of implementation according
to which a strip 400 is made with a row of blanks 100 woven in
the weft direction perpendicularly to the longitudinal
direction of the strip. Extra-length areas 410, 420 are also
provided in the warp direction and, in the weft direction.
Several rows of blanks 100 can be woven, the width of the
strip 400 being adjusted to this end.
Successive steps of a manufacturing method for a blade
made of composite material according to one embodiment of the
invention are indicated in Figure 16.
At step 501, a fiber strip is woven by three-
dimensional weaving having a plurality of fiber blanks, for
example several rows of fiber blanks oriented in the warp
direction, as shown in Figure 15. For turbomachine blades
designed for use at high temperature and particularly in a
corrosive environment (particularly humidity), yarns made of
ceramic fibers are used for weaving, particularly silicon
carbide (SiC) fibers.
At step 502, the fiber strip is treated to eliminate
oiling present on the fibers and the presence of oxide on the
surface of the fibers. The elimination of the oxide is
obtained by acid treatment, particularly by immersion in a
hydrofluoric acid bath. If the oiling cannot be eliminated by
the acid treatment, a prior treatment for eliminating oiling
is carried out, for example by decomposition of the oiling by
a brief heat treatment.
At step 503, a thin layer of interphase coating is
formed on the fibers of the fiber strip by chemical vapor
infiltration or CVI. The material of the interphase coating is
for example pyrolytic carbon or pyrocarbon (PyC), boron
nitride (BN) or boron-doped carbon (BC, with for example 5
atom percent (oat) to 20%at B, the remainder being C) . The
thin layer of interphase coating has preferably a small
thickness, for example equal to 100 nanometers at most, or
even equal to 50 nanometers at most, so as to maintain good
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deformability of the fiber blanks. Preferably, the thickness
is at least equal to 10 nanometers.
At step 504, the fiber strip with the fibers coated
with a thin interphase coating layer is impregnated with a
consolidation composition, typically a resin possibly diluted
in a solvent. A carbon precursor resin can be used, for
example a phenolic or furanic resin, or a ceramic precursor
resin, for example a polysilazane or polysiloxane resin
precursor of SiC.
After drying by elimination of any solvent in the
resin (step 505), a pre-curing of the resin can be carried out
(step 506). The pre-curing, or partial crosslinking, allows an
increase in the stiffness, hence the strength, while still
preserving the deformability needed for the fabrication of
blade preforms.
At step 507, the individual fiber blanks are cut out,
as illustrated by Figures 4 and S.
At step 508, a fiber blank thus cut out is shaped (as
illustrated by Figures 5 and 6) and placed in a mold, made of
graphite for example, for forming of the airfoil and root
preform portion and of the inner platform portion, anti-
tilting wall portion, blade outer platform spoilers portion
and outer platform wipers portion preform portions.
Thereafter, the crosslinking of the resin is completed
(step 509) and the crosslinked resin is pyrolized (step 510).
The crosslinking and the pyrolysis can be concatenated by
progressively raising the temperature in the mold.
After pyrolysis, a fiber preform consolidated by the
pyrolysis residue is obtained. The quantity of consolidation
resin is selected so that the pyrolysis residue links the
fibers of the preform sufficiently that it can be handled
while retaining its shape without the assistance of tooling,
it being specified that the quantity of consolidation resin is
preferably chosen to be as low as possible.
Steps consisting of eliminating oiling, of acid
treatment and of formation of interphase coating for a
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substrate made of SiC fibers are known. Reference can be made
to document US 5,071,679.
A second interphase layer is formed by CVI (step 511)
in order to generally obtain a fiber-matrix interphase having
sufficient thickness to provide its function of brittleness
relief of the composite material. The second interphase layer
can be a material selected from among PyC, BN, BC, not
necessarily the same as that of the first interphase layer.
The thickness of the second interphase layer is preferably at
least equal to 100 nanometers.
The fabrication of two-layer interphase, as indicated
earlier, is preferred. It is described in French patent
application No. 08 54937 by SNECMA Propulsion Solide.
Densification by a matrix of the consolidated preform
is then carried out. For a turbomachine blade designed for use
at high temperature, and particularly in a corrosive
environment, the matrix is of ceramic, for example of SiC.
Densification can be carried out by CVI, in which case
formation of the second interphase layer and densification by
the matrix can be concatenated in the same furnace.
Densification can be carried out in two successive
steps (steps 512 and 514) separated by a step 513 consisting
of machining the blade to the desired dimensions.
It will be noted that a pre-machining operation can be
carried out between steps 509 and 510, that is to say after
crosslinking and before pyrolysis of the resin.
Successive steps of a manufacturing method of a blade
made of composite material according to another embodiment of
the invention are given in Figure 17.
Step 601 consisting of three-dimensional weaving of a
fiber strip having a plurality of fiber blanks and step 602
consisting of treatment for eliminating oiling and oxide are
similar to steps 501 and 502 of the embodiment of Figure 16.
At step 603, individual fiber blanks are cut out of
the fiber strip, then each individual fiber blank is shaped in
a mold or former (step 604) to obtain a fiber blade preform by
forming of the airfoil and root preform portion and of the
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inner platform portion, anti-tilting wall portion, blade outer
platform spoilers portion and outer platform wipers portion
preform portions.
At step 605, an interphase brittleness relief coating
5 is formed by CVI on the fibers of the preform held in the
former. The material of the interphase coating is for example
PyC, BN or BC, as previously mentioned. The thickness of the
interphase coating is roughly one to a few hundred nanometers.
The preform still being held in the former,
10 consolidation of the preform by partial densification is
carried out (step 606), the consolidation being carried out by
formation of a ceramic deposit on the fibers by CVI.
The formation of the interphase coating by CVI and
consolidation by ceramic deposit by CVI can be concatenated in
15 the same CVI furnace.
The former is preferably made of graphite and exhibits
holes facilitating the passage of reactive gas phases giving
the interphase deposit by CVI.
When consolidation is sufficient that the preform can
20 be handled which still retaining its shape without the
assistance of holding tooling, the consolidated preform is
removed from the former and densification by a ceramic matrix
by CVI is carried out. The densification can be performed in
two successive steps (steps 607 and 609) separated by a step
25 608 consisting of machining the blade to the desired
dimensions.
In the foregoing, the fabrication of a variable
thickness airfoil profile by using yarns having variable
weight and/or count has been considered. It is possible, as a
variant, to fabricate the fiber blank portion corresponding to
the airfoil preform with a certain number of layers of yarns
with the same weight and with a fixed count, the variation in
profile thickness being obtained during machining after the
first densification step or during pre-machining of the
consolidated blade preform.
Further, according to the conditions of use planned for
the blade, the fibers of the fiber reinforcement of the blade
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can be made of a material other than ceramic, for example of
carbon, and the matrix can be of a material other than
ceramic, for example of carbon or of a resin, the invention
being of course also applicable to the manufacture of blades
made of organic matrix composite material.
Figure 18 shows the mounting on a turbomachine rotor
or disk 500 of a plurality of blades 510, 520, 530 and 540
exhibiting a structure similar to the blade 10 of Figure 1.
The blades 510, 520, 530 and 540 are mounted on the rotor 500
by inserting the roots 517, 527, 537 and 547 of each blade
respectively into the recesses 501, 502, 503 and 504 having
matching shapes provided in the periphery of the rotor. As
described before for the blade 10, the airfoil 516,
respectively 526, 536 and 546, of the blade 510, respectively
520, 530 and 540, includes on its surface 512 (suction face),
respectively 522, 532 and 542, an inner platform portion
(including covering spoilers at its ends) 518, respectively
528, 538 and 548 and a blade outer platform spoiler portion
514, respectively 524, 534 and 544. In addition, on its face
511 (pressure face), respectively 521, 531 and 541, the
airfoil 516, respectively 526, 536 and 546, includes an anti-
tilting wall portion 513, respectively 523, 533 and 543 and a
blade outer platform wipers portion 515, respectively 525, 535
and 545.
As shown in Figure 18, the blades nest with one
another, one already-mounted blade, for example the blade 530,
receiving above its anti-tilting wall portion, 533 here, the
inner platform portion of the adjacent blade, here the
platform portion 548 of the blade 540. Likewise, the blade 530
receives above its blade outer platform wipers portion 535 the
blade outer platform spoilers portion 544 of the blade 540.
Once mounted together, each blade, here for example
the blade 520, comprises on each side of its airfoil, here the
airfoil 526, the functions customarily present at its radially
inward end, to wit the anti-tilting function provided here by
the combination of the anti-tilting wall portions 513 and 523
and the function of defining a flowpath provided here by the
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combination of the inner platform portions 528 and 538 as well
as at its radially outward end, to wit the function of
defining a flowpath provided by the combination of the outer
platform spoiler portions 524 and 534 and the sealing function
provided by the combination of the outer platform wipers
portions 515 and 525.
The blade 10 described earlier in relation with
Figure 1 includes on the suction face of its airfoil 20 the
blade platform portion 40 and the blade outer platform wipers
portion 70, while it includes on the pressure of its airfoil
the anti-tilting wall portion 50 and the blade outer
platform spoilers portion 60. According to variants of
implementation, the blade inner platform and blade outer
platform wipers portions can be arranged on the pressure face
15 of the blade airfoil while the anti-tilting wall and blade
outer platform spoilers portions can be arranged on the
suction face of the blade airfoil. According to other variants
of implementation, the distribution of the blade inner
platform, blade outer platform wipers, anti-tilting wall and
20 blade outer platform spoilers portions over the faces of the
blade airfoil can be such that the airfoil comprises on one of
the faces of its airfoil only one of the portions of the blade
inner platform, blade outer platform wipers, anti-tilting wall
and blade outer platform spoilers portions, the three other
portions being arranged on the other face of the airfoil or
such that these four portions are all present on the same face
of the airfoil. However, for a better distribution of the
masses over the blade, the blade preferably comprises two
portions on one face and the two other portions on the
opposite face of the airfoil.
According to still other variations of implementation
of the blade according to the invention, a portion of the
elements of blade inner platform, of blade outer platform
wipers, of anti-tilting wall and of blade outer platform
spoilers can be present on both faces of the airfoil while
certain other of these elements are present only on one face
of the airfoil as described earlier. Figure 19 illustrates
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such an example of a variant of implementation with a blade
600 which comprises an inner platform 640 and complete blade
outer platform spoilers 660 in that they are present on both
faces 622 and 623 of the airfoil 620 while only the anti-
tilting wall 650 and blade outer platform wipers 670 portions
are present only respectively on the face 623 of the airfoil
620. In this case, the fiber strip designed to constitute the
airfoil, such as the strip 102 described earlier, and crossed
at the connecting portions, such as the portions 140c and 150c
described previously, by two fiber strips such as the strip
104, in order to make it possible to have independent portions
of fiber strip allowing the fabrication of an inner platform
and blade outer platform spoilers together with anti-tilting
wall and blade outer platform spoilers portions.
