Title of the invention
A fiber preform for a turbine engine blade made of
composite material and having an integrated platform, and
a method of making it
5
Background of the invention
The present invention relates to making a blade
fiber preform having at least one platform, in particular
for fabricating a turbine engine blade out of composite
10 material.
Proposals have already been made to make blades out
of composite material for turbine engines. By way of
example, reference may be made to document EP 1 526 285,
which describes fabricating a fan blade by making a fiber
15 preform by three-dimensional weaving and densifying the
preform with an organic matrix.
Furthermore, a turbine engine fan includes platforms
that are arranged between the blades in order to define
the inside of the annular air inlet passage into the fan,
20 this passage being defined on the outside by a casing.
These platforms may be added separately or they may be
incorporated directly with the bases of the fan blades,
between their airfoils and the tangs that extend their
roots. The invention relates more particularly to blades
25 forming part of the second category, i.e. blades having
one or more platforms integrated therewith.
Object and summary of the invention
It is therefore desirable to have turbine engine
30 6lades with one or more integrated platforms and made out
of composite material, in particular, but not
exclusively, out of- organic matrix composite (OMC)
material.
To this end, the invention proposes a method of
35 making a fiber preform for fabricating a turbine engine
blade out of composite material, the blade having an
airfoil extending in a longitudinal direction and
presenting two opposite side faces and at least one
platform extending from a side face, the method
comprising:
making a single-piece fiber blank by three-
5 dimensional weaving with a plurality of longitudinal
yarns extending in a direction corresponding to the
longitudinal direction of the blade that is to be
fabricated and interlinked by yarns of a plurality of
transverse layers of yarns;
10 shaping the fiber blank to obtain a single-piece
fiber preform having a first portion forming an airfoil
preform and at least one second portion forming a
platform preform; and
during the weaving of the fiber blank, extracting
15 yarns of a first group of longitudinal yarns from the
fiber blank beside at least one of the side faces of the
fiber blank in order to form a portion of the blank
corresponding to a blade platform preform, and inserting
yarns of a second group of longitudinal yarns into the
20 fiber blank with mutual crossing between the yarns of the
first group and the yarns of the second group.
During weaving, by crossing yarns extracted from the
fiber blank with yarns inserted into the fiber blank, it
is possible to obtain a single-piece fiber preform by
25 three-dimensional weaving with both a portion that forms
the airfoil preform and another portion that forms the
platform preform, while maintaining fiber density within
the fiber blank that is constant in spite of extracting
the yarns of the first group.
30 This also ensures fiber continuity between the
portion of the preform that forms the airfoil and the
portion of the preform that forms the platform, thereby
making it possible to impart the mechanical properties
that are required for a blade having an integrated
35 platform.
According to a feature of the method, the crossing
between the yarns of the first group and the yarns of the
second group takes place close to a connection between
the portion of the blank corresponding to the blade
platform preform and the portion of the blank
corresponding to the airfoil preform.
5 Preferably, the yarns of the second group of yarns
that are inserted into the fiber blank come from layers
of longitudinal yarn previously extracted from the fiber
blank in order to obtain a reduction in the thickness of
the blank over its width. Layers of yarns may be
10 extracted from the blank in order to take account of the
reduction in the thickness of the profile of the airfoil
(going from the root towards the tip of the blade).
Using them to make the platform is therefore particularly
advantageous since this avoids wasting them.
15 Under such circumstances, the shaping of the fiber
blank advantageously includes cutting away the portion of
the yarns of the second group of yarns that are situated
between the zones where they are extracted from and
inserted into the fiber blank. Furthermore, at least
20 some of the yarns of the second group of yarns may be
extracted from the fiber blank downstream from the zone
where they are inserted into said fiber blank in order to
reduce the thickness of the blank over its width
downstream from the portion of the blank that corresponds
25 to the blade platform preform.
When the profile of the airfoil of the blade does
not present any thickness reduction between the root and
the tip of the blade, or when such reduction in thickness
does not enable a large enough quantity of yarns to be
30 made available for forming the blade platform, at least
some of the yarns of the second group of yarns that may
be inserted into the fiber blank may come from additional
layers of longitudinal yarns.
According to another feature of the method, the
35 yarns are extracted from and inserted into the fiber
blank on each of the side faces of the fiber blank in
order to form portions of the blank that correspond to
two blade platform preforms. Under such circumstances,
the blade that is fabricated therefrom presents two
platforms, one on either side (pressure side and suction
side).
5 According to yet another feature of the method, the
shaping of the fiber blank includes cutting the portion
of the blank that corresponds to the blade platform
preform to have the desired dimensions, and deploying
said portion of the blank in a direction that is
10 substantially orthogonal to its side face.
The longitudinal yarns extending in a direction
corresponding to the longitudinal direction of the blade
that is to be fabricated may be warp yarns.
Alternatively, the longitudinal yarns extending in a
15 direction corresponding to the longitudinal direction of
the blade that is to be fabricated may be weft yarns.
The invention also provides a fiber preform for a
turbine engine blade having an airfoil extending in a
longitudinal direction and presenting two opposite side
20 faces together with at least one platform extending from
a side face, the preform comprising a fiber blank woven
as a single piece by three-dimensional weaving with a
plurality of layers of longitudinal yarns extending in a
direction corresponding to the longitudinal direction of
25 the blade that is to be fabricated and interlinked by
yarns of a plurality of layers of transverse yarns,
wherein, in accordance with the invention, yarns of a
first group of longitudinal yarns are extracted from the
fiber blank beside at least one of the side faces of the
30 fiber blank in order to form a portion of the blank
corresponding to a blade platform preform, and yarns of a
second group of longitudinal yarns are inserted into the
fiber blank, with mutual crossing between the yarns of
the first group and of the second group.
3 5 The invention also provides a turbine engine fan
blade made of composite material and comprising a fiber
preform as defined above that has been densified with a
matrix. The invention also provides a turbine engine fan
that includes at least one such blade.
Brief description of the drawings
5 Other characteristics and advantages of the present
invention appear from the following description given
with reference to the accompanying drawings that show an
implementation having no limiting character. In the
figures :
10 Figure 1 is a perspective view of a turbine engine
fan blade having two platforms integrated therewith;
Figure 2 is a very diagrammatic view of the
arrangement of the layers of yarns in a 3D woven fiber
blank for making a fan blade such as that shown in
15 Figure 1;
Figure 3 is a diagrammatic view of a warp plane
showing one way of weaving the Figure 2 fiber blank; and
Figure 4 is a diagrammatic view of a warp plane
showing another way of weaving the fiber blank in a
20 variant implementation of the invention.
Detailed description of the invention
The invention is applicable to fabricating any
turbine engine blade having integrated platform(s) out of
25 composite material, and it appiies particulariy but not
exclusively to fan blades such as the blade shown in
Figure 1.
In well-known manner, the blade 10 of Figure 1
comprises an airfoil 20, a root 30 formed by a portion of
30 greater thickness, e.g. having a section that is bulbshaped,
extended by a tang 32, and two platforms 40
situated between the tang 32 and the airfoil 20.
The airfoil 20 extends in a longitudinal direction
between the platforms 40 and the tip 22 of the blade, and
35 it presents a curved profile in cross-section of
thickness that varies between its two opposite side faces
(i.e. its leading edge 24 and its trailing edge 26).
At its inner radial end, the blade 20 is connected
to the platforms 40 via outside faces thereof that serve
to define the inside of the annular inlet passage for
admitting air into the fan, this passage being defined on
5 the outside by a casing (not shown).
In the example of Figure 1, the blade 10 thus has
two platforms 40 that extend from the side faces (its
pressure side face 20a and its suction side face 20b) of
the blade 20. Naturally, the invention also applies to
10 blades that have only one platform (e.g. extending from
the suction side face of the blade, with the pressure
side face then not having a platform).
Figure 2 shows the arrangement of the layers of
yarns in a 3D woven fiber blank 100 for use in making a
15 fan blade such as that shown in Figure 1.
The fiber blank 100 comprises a central portion 110
that forms a preform for the airfoil and for the root,
and two side portions 120 that, after shaping, are to
form platform preforms. These portions 110 and 120 of
20 the blank extend generally in the direction X
corresponding to the longitudinal direction of the blade
that is to be made. In this figure, only the envelopes
of these two portions are shown. The central portion 110
has two opposite side faces 110a and llOb from which the
25 two side portions 120 extend. When making a fan blade
having a single platform, then only one of these side
portions is present.
In its portion 112 that is to form a root preform,
the central portion 110 presents extra thickness (between
30 the side faces llOa and 110b) that is determined as a
function of the thickness of the root of the blade that
is to be made. In its portion 114 that is to form an
airfoil preform, the central portion 110 presents varying
thickness that is determined as a function of the
35 thickness of the profile of the airfoil of the blade that
is to be made.
Put briefly, a fiber preform having a shape close to
the shape of the fan blade that is to be made can be
obtained from such a fiber blank 100 as follows. After
quality control, the fiber blank 100 is cut out flat so
5 that all of the extra lengths are eliminated from the
weaving and so that the part presents dimensions that
match the injection mold. The cutting-out step applies
in particular to the portion 112 of the blank that is to
form a root preform, to the leading edge, the trailing
10 edge, and the tip of the central portion 110 forming a
blade preform, and to the ends of the side portions 120
that are to form the platform preforms.
Once cutting has been completed, the blank is shaped
by laying it out flat and lifting one of the side
15 portions so that it extends at 90" relative to the
corresponding side face of the central portion. This
position is blocked and the preform is turned over. The
central portion of the blank is then deformed to
reproduce the curved profile of the blade. Thereafter,
20 the side portion is deployed at 90' relative to the
corresponding side face of the central portion. This
produces a single-piece fiber preform with one portion
forming a preform for an airfoil and a root and two
portions forming preforms for platforms. The resulting
25 fiber preform is then dried and put into place in the
injection mold.
The matrix is deposited in the fiber preform by
keeping the preform in the mold at least until the
preform has stiffened (or consolidated). The matrix is
30 of a nature that is selected as a function of the
intended application, e.g. an organic matrix obtained in
particular from a resin that is a precursor of a polymer
matrix, such as an epoxy, bismaleimide, or polyimide
resin, or a carbon matrix, or a ceramic matrix. For an
35 organic matrix, the fiber preform is impregnated with a
composition containing the matrix precursor resin, prior
to being shaped in tooling, or after being shaped,
impregnation then being performed for example by infusion
or by a resin transfer molding (RTM) type process. With
a carbon matrix or a ceramic matrix, densification may be
performed by chemical vapor infiltration (CVI) or by
5 impregnation with a liquid composition containing a resin
that is a precursor for carbon or for ceramic, and then
applying pyrolysis or ceramization heat treatment to the
precursor, these methods themselves being well known.
Ways in which the fiber blank 100 can be woven
10 three-dimensionally are described in detail below.
It is assumed that the weaving is performed with
warp yarns that extend in the longitudinal direction X of
the blank, it being understood that it is also possible
for weaving to be performed with weft yarns extending in
15 this direction.
Figure 3 is a warp plane of a three-dimensional
fiber blank 100 for use in making a fiber preform such as
that shown in Figure 2. The term "warp" plane is used
herein to designate a plane in the fiber blank that
20 extends perpendicularly to the weft yarns and that
contains a column of warp yarns (in Figure 2, continuous
lines represent warp yarns).
By way of example, in a portion 112 that is to form
a root preform, the fiber blank may comprise, between its
25 opposite side faces llOa and 110b, 24 layers of warp
yarns c, to c,, and as many layers of weft yarns t, to t,,.
In this portion 112, the weave is of the interlock type
with a satin type weave for the warp yarns c, and c,, in
the portions adjacent to the opposite side faces llOa and
30 110b. 3D weaving of a fiber structure with an interlock
type weave in its core and a 2D or 3D satin type weave in
its skin is itself known. Reference may be made to
document WO 2006/136755.
In the portion 114 that is to form an airfoil
35 preform, the thickness of the fiber blank between its
side faces llOa and llOb varies. Thus, in order to take
account of this thinning of the profile of the blade that
is to be fabricated, layers of warp yarns and a
corresponding number of weft yarns are withdrawn
progressively from the fiber blank. In the example of
Figure 3, it is the warp yarns c,, c,, and c, that are
5 successively withdrawn from beside the side face 110a,
and warp yarns c,,, c,,, and c,, that are successively
withdrawn from beside the opposite side face 110b. This
manipulation that consists in withdrawing yarns that are
being woven in the weaving of the fiber blank is itself
10 known. Reference may be made to document EP 1 528 285.
In a zone 116 of the portion 114 of the fiber blank
there are woven the side portions 120 that are to form
platform preforms. For this purpose, layers of warp
yarns are withdrawn from the fiber blank beside each of
15 its side faces and they are woven with certain layers of
weft yarns. In the example of Figure 3, it is thus
adjacent warp yarns c, to c, that are withdrawn from
beside the side face 110a and woven with weft yarns t, to
t, to form one of the side portions 120. Similarly, the
20 adjacent warp yarns c,, to c,, are withdrawn beside the
other side face llOb and they are woven with weft yarns
t,, to t,, to form the other one of the side portions 120.
Zones of non-interlinking are arranged between the layers
of the warp yarns forming the portions 120 and the layers
25 of warp yarns of the portion 114 that is to form an
airfoil preform.
Furthermore, in order to maintain a constant fiber
density in the fiber blank in spite of these warp yarns
being withdrawn to form the side portions 120, at least
30 some of the warp yarns that are withdrawn'from the fiber
blank for tapering the thickness of the profile of the
blades are inserted into the portion 114 of the fiber
blank in the zone 116 (here the warp yarns c, and c,
beside the side face 110a and c,,, c,,, and c,, beside the
35 side face 110b). Thus, these warp yarns cross the warp
yarns c, to c, (beside the side face 110a) and c,, to c,,
(beside the side face 110b), preferably at the
connections between the portion 114 corresponding to the
airfoil preform and the side portions 120 correspond to
the platform preforms.
As a result, the warp yarns c, and c, beside the side
5 face llOa and c,,, c,,, and c,, beside the side face llOb
are floated (i.e. they remain at the surface of the fiber
blank without being interlinked with the weft yarns)
between the zone where they exit the portion 114 of the
fiber blank and the zone 116 where they are reinserted.
10 If so required by the tapering thickness of the airfoil
profile, at least some of these warp yarns may be
extracted once more further downstream in the portion 114
of the fiber blank. For example, in Figure 3, this
applies to the warp yarns c,, c,,, c,,, and c,,. In the
15 subsequent step of shaping the fiber blank, the portions
of these warp yarns c,, c,,, c,,, and c,, that are situated
between their exits from and their insertions into the
fiber blank are cut away.
Figure 3 shows an implementation of crossing between
20 the warp yarns reinserted into the portion 114 of the
fiber blank in the zone 116 and the warp yarns extracted
therefrom in order to weave the side portions 120 that
are to form the platform preforms. Naturally, other
known types of crossing could be used, in particular so
25 as to avoid crossing that is too sudden.
Figure 4 shows a weft plane of a fiber blank 100'
for making a fiber blank for a turbine engine fan blade
while weaving in a different way.
In this implementation, the profile of the airfoil
30 of the blade that is to be made does not taper in its
thickness, at least in the bottom portion of the blade
going away from the platforms (i.e. thickness remains
constant) .
In its portion 112' that is to form a root preform,
35 and between its opposite side faces 110a' and llObl, the
fiber blank 100' comprises 24 layers of warp yarns c, to
c,, and as many layers of weft yarns t, to t,,. In this
portion 112', the weave is of the interlock type with a
satin type weave for the warp yarns c, and c,, in the
portions adjacent to the opposite side faces.
In the portion 114' that is to form an airfoil
5 preform, the thickness of the fiber blank between its
side faces 110'a and 110'b remains constant, such that no
layer of yarns is extracted.
As in the above-described implementation, in a zone
116' of the portion 114' of the fiber blank, there are
10 woven the side portions 120' that are to form the
platform preform. For this purpose, in the example of
Figure 4, adjacent warp yarns c, to c, are withdrawn from
beside the side face 110'a and woven with weft yarns t, to
t, in order to form one of the side portions 120'.
15 Likewise, adjacent warp yarns c,, to c,, are withdrawn
beside the other side face 110'b and they are woven with
weft yarns t,, to t,, in order to form the other one of the
side portions 120'.
In order to maintain a constant fiber density in the
20 fiber blank in spite of withdrawing these warp yarns that
are to form the side portions 120', additional warp yarns
c', to c', and c',, to c',, are introduced into the portion
114' of the fiber blank in the zone 116'. Thus, these
warp yarns cross the warp yarns c, to c, (beside the side
25 face 110') and c,, to c,, (beside the side face llO1b),
preferably where the portion 114' corresponding to the
airfoil preform is connected to the side portions 120'
corresponding to the platform preforms.
It is possible to envisage other variant ways of
30 weaving the fiber preform of the invention.
In particular, when the blade that is to be
fabricated has only one platform, extracting layers of
yarns for weaving its preform takes place beside only one
of the side faces of the fiber preform. This solution
35 makes it possible to achieve greater flexibility if there
are only a few layers of yarns available for weaving the
platform preform.
It is also possible to make a fiber preform that
presents preforms for half-platforms extending from its
side faces. The half-platforms of the blade fabricated
from such a preform then do not fully cover the space
5 between two adjacent blades and it is necessary to make
the missing half-platforms independently. Nevertheless,
they are relatively easy to make since their weaving does
not require the curvature of the airfoil to be taken into
account.
10 In an alternative to the weaving of Figure 3, the
thickness of the airfoil of the blade to be fabricated
may be varied by using weft yarns of variable weight.
This alternative makes it possible to avoid extracting
layers of yarns from the fiber blank and then reinserting
15 them a little downstream.
In another alternative way of weaving the fiber
blank, it is possible to double up the warp yarns
constituting platform preforms and to weave them side by
side so as to make them easier to extract from the fiber
20 blank at the specific location where the platforms are to
be positioned.
CLAIMS
1. A method of making a fiber preform for fabricating a
turbine engine blade out of composite material, the blade
(10) having an airfoil (20) extending in a longitudinal
5 direction and presenting two opposite side faces (24, 26)
and at least one platform (40) extending from a side
face, the method comprising:
making a single-piece fiber blank (100 ; 100') by
three-dimensional weaving with a plurality of
10 longitudinal yarns (CI to Cz4) extending in a direction
corresponding to the longitudinal direction of the blade
that is to be fabricated and interlinked by yarns of a
plurality of transverse layers of yarns (tl to t24);
shaping the fiber blank to obtain a single-piece
15 fiber preform having a first portion forming an airfoil
preform and at least one second portion forming a
platform preform;
characterized in that, during the weaving of the
fiber blank, yarns ( c t~o c7, clg to CZO) of a first group
20 of longitudinal yarns are extracted from the fiber blank
beside at least one of the side faces (110a, 110b) of the
fiber blank in order to form a portion (120) of the blank
corresponding to a blade platform preform, and yarns (c3,
cq, CZI, czz and c23 ; C'I to ~'3) of a second group of
25 longitudinal yarns are inserted into the fiber blank with
mutual crossing between the yarns of the first group and
the yarns of the second group.
2. A method according to claim 1, wherein the crossing
30 between the yarns of the first group and the yarns of the
second group takes place close to a connection between
the portion of the blank corresponding to the blade
platform preform and the portion of the blank
corresponding to the airfoil preform.
35
3. A method according to claim 1 or claim 2, wherein the
yarns of the second group of yarns that are inserted into
the fiber blank come from layers of longitudinal yarn
previously extracted from the fiber blank in order to
obtain a reduction in the thickness of the blank over its
width.
4. A method according to claim 3, wherein the shaping of
the fiber blank includes cutting away the portions of the
yarns of the second group of yarns that are situated
between the zones where they are extracted from and
inserted into the fiber blank.
5. A method according to claim 3 or claim 4, wherein at
least some of the yarns of the second group of yarns are
extracted from the fiber blank downstream from the zone
where they are inserted into said fiber blank in order to
reduce the thickness of the blank over its width
downstream from the portion of the blank that corresponds
to the blade platform preform.
6. A method according to claim 1 or claim 2, wherein at
least some of the yarns of the second group of yarns that
are inserted into the fiber blank come from additional
layers of longitudinal yarns.
7. A method according to any one of claims 1 to 6,
wherein the yarns are extracted from and inserted into
the fiber blank on each of the side faces of the fiber
blank in order to form portions of the blank that
correspond to two blade platform preforms.
8. A method according to any one of claims 1 to 7,
wherein the shaping of the fiber blank includes cutting
the portion of the blank that corresponds to the blade
platform preform to have the desired dimensions, and
deploying said portion of the blank in a direction that
is substantially orthogonal to its side face.
9. A method according to any one of claims 1 to 8,
wherein the longitudinal yarns extending in a direction
corresponding to the longitudinal direction of the blade
that is to be fabricated are warp yarns.
5
10. A method according to any one of claims 1 to 8,
wherein the longitudinal yarns extending in a direction
corresponding to the longitudinal direction of the blade
that is to be fabricated are weft yarns.
10
11. A fiber preform for a turbine engine blade (10)
having an airfoil (20) extending in a longitudinal
direction and presenting two opposite side faces (24, 26)
together with at least one platform (40) extending from a
15 side face, the preform comprising a fiber blank (100,
100') woven as a single piece by three-dimensional
weaving with a plurality of layers of longitudinal yarns
(cl to C24) extending in a direction corresponding to the
longitudinal direction of the blade that is to be
20 fabricated and interlinked by yarns of a plurality of
layers of transverse yarns (tl to tz4), characterized in
that yarns (c5 to c7, C18 to czO) of a first group of
longitudinal yarns are extracted from the fiber blank
beside at least one of the side faces (110a, 110b) of the
9 L
LJ fiber blank in order to form a portion (120) of the blank
corresponding to a blade platform preform, and yarns (c3,
cq, ~21, c22 and ~ 2 ;3 c'l to ~'3)o f a second group of
longitudinal yarns are inserted into the fiber blank,
with mutual crossing between the yarns of the first group
30 and the yarns of the second group
12. A preform according to claim 11, wherein the crossing
between the yarns of the first group and the yarns of the
second group takes place close to a connection between
35 the portion of the blank that corresponds to a blade
platform preform and the portion of the blank that
corresponds to the airfoil preform.
13. A preform according t o clpim 11 or claim 12, wherein
yarns are extracted from and i n s e r t e d i n t o t h e f i b e r
blank on each of t h e side faces of t h e f i b e r blank i n
5 order t o form portions of the blank t h a t correspond t o
two blade platform preforms.
1 4 . A turbine engine fan blade made of composite material
and including a f i b e r preform according t o any one of
10 claims 11 t o 1 3 d e n s i f i e d by a matrix.
15. A turbine engine fan including a t l e a s t one blade
according t o claim 1 4 .
Dated this 08.07,2014
[RANJNA MEHTA-DUTT]
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANT[S]
-