Title of the invention
A composite material reinforcing part of n-shaped
section, in particular a platform for a turbine engine
fan, and its method of fabrication
5
Background of the invention
The present invention relates to the general field
of reinforcing parts of n-shaped section that are made of
composite material comprising fiber reinforcement
10 densified with a matrix.
A field of application is that of platforms for
turbine engine fans
The fan platforms of a turbine engine, in particular
of a turbojet, are arranged between the blades of the fan
15 so as to extend its inlet cone. They serve in particular
to define the inside of the annular inlet passage for
admitting air into the fan, said passage being defined on
the outside by a casing.
A fan platform may be attached to the structure of
20 the engine by means of steps that are formed at the front
and at the rear of the platform. The steps are then
received under rims of the structure of the engine so as
to retain the platform against the effect of the
centrifugal force due to the speed of rotation of the
25 fan. The centrifugal force due to the rotation of the
fan also has the effect of causing the platform to bulge
outwards in its middle. Thus, in order to ensure that
the platforms behave properly and in order to avoid them
moving excessively, it is necessary to stiffen these
30 parts by giving them legs or tabs that extend under their
bases.
Furthermore, having recourse to thermostructural
composite materials, and in particular organic matrix
composite (CMC) materials has become common practice when
35 making fan blades. Compared with metal alloys, such
materials present better high temperature performance and
they weigh less.
Object and summary of the invention
It is therefore desirable also to have fan
platforms, and more generally turbine engine reinforcing
5 parts, that are made of composite material, particularly
but not exclusively out of thermostructural composite
material such as OMC material.
To this end, the invention provides a method of
fabricating a reinforcing part of x-shaped section out of
10 composite material, the part comprising a first portion
forming a base that presents a step at at least one of
its longitudinal ends, and a second portion forming a
stiffener having two legs that extend from a face of the
base over at least a fraction of the length thereof, the
15 method comprising:
making a first set of a plurality of layers of
yarns that are interlinked by three-dimensional weaving
to form a first fiber blank portion that is to form a
base preform;
20 making a second set of a plurality of layers of
yarns that are interlinked by three-dimensional weaving
to form a second fiber blank portion that is to form a
stiffener preform, yarns of the second set of layers of
yarns being interlinked by weaving with the yarns of the
25 first set of layers of yarns in a central interlinked
strip extending longitudinally between the two
longitudinal ends of the first fiber blank portion and
flaring towards the side edges thereof in a zone
corresponding to the step of the base;
30 shaping the two fiber blank portions to obtain a
single-piece fiber preform having a portion forming a
base preform and a portion forming a stiffener preform;
and
depositing a resin in the fiber preform so as to
35 obtain a composite material reinforcing part comprising
fiber reinforcement constituted by the preform that is
densified by the matrix.
The method of the invention provides for
interlinking the two sets of layers of yarns along a
central interlinked strip that flares in a zone of the
first blank portion that corresponds to the step of the
5 base. The particular shape of the interlinking that
results therefrom between the two sets of layers of yarns
thus makes it possible, during shaping, to form the leg
blanks of the stiffener of the reinforcing part in spite
of the presence of the step. In particular, in the
10 region of the step, the leg blanks may be formed without
creating folds in their length that might otherwise give
rise to buckling phenomena.
Compared with three-dimensional weaving of a fiber
blank for the reinforcing part as a single piece, the
15 method of the invention presents the advantage of being
much simpler to implement. In particular, the shaping of
the portions making up the fiber blank does not require
the preform to be cut, nor does it require numerous and
difficult operations of positioning folds relative to one
20 another.
Furthermore, the method of the invention makes it
possible to obtain a fiber preform that is particularly
robust since the two fiber blank portions that make it up
are interlinked by weaving. When applied to fabricating
25 a turbine engine fan platform, the method of the
invention thus contributes to imparting the mechanical
properties for such a platform, in particular at the
connection between the base-forming portion and the
stiffener-forming portion.
30 According to an advantageous feature of the method,
the interlinking of the yarns of the second set of layers
of yarns and the yarns of the first set of layers of
yarns by weaving is obtained by crossing said yarns
respectively along the interlinked strip. Such
35 interlinking may thus be obtained without adding
additional yarns, thereby avoiding stiffening the
preform.
When the base ofthe reinforcing part presents a
step at both of its longitudinal ends, the interlinked
strip between the yarns of the first and second sets of
layers of yarns flares advantageously toward the side
5 edges of the first fiber blank portion in each of the
zones corresponding to the steps of the base. Under such
circumstances, and preferably, upstream from the zone
corresponding to the upstream step of the base and
downstream from the zone corresponding to the downstream
10 step of the base, the interlinked strip between the yarns
of the first and second sets of layers of yarns extends
transversely over the entire width of said first fiber
blank portion. The terms "upstream" and "downstream" are
used herein relative to the direction of weaving.
15 Preferably, shaping comprises forming at least one
step by folding the two fiber blank portions along a
common, substantially-transverse fold line. Likewise,
the shaping of the second fiber blank portion comprises
folding the non-interlinked portions of the second fiber
20 blank portion in a direction that is substantially
perpendicular to the first fiber blank portion so as to
form two leg preforms.
The invention also provides a reinforcing part of nshaped
section made of composite material, comprising a
25 base-forming first portion that presents a step at at
least one of its longitudinal ends, and a stiffenerforming
second portion having two legs that extend from a
face of the base over at least a fraction of the length
thereof, the first and second portions being interlinked
30 along a central interlinked strip that extends
longitudinally between the two longitudinal ends of the
first portion and that flares towards the side edges
thereof in a zone corresponding to the step of the base.
The reinforcing part may be made of organic matrix
35 composite material.
According to a feature of the reinforcing part, the
first and second portions are interlinked by respective
crossings of the yarns that constitute them in the
interlinked strip.
According to another feature of the reinforcing
part, downstream from the zone of the first portion
5 corresponding to the step of the base, the interlinked
strip between the first and second portions extends
transversely over the entire width of said first portion.
The first portion of the reinforcing part may
include a step at each of its longitudinal ends.
10 The reinforcing part may constitute a fan platform
of a turbine engine.
The invention also provides a turbine engine fitted
with at least one fan platform as defined above.
15 Brief description of the drawings
Other characteristics and advantages of the present
invention appear from the following description made with
reference to the accompanying drawings that show an
implementation having no limiting character. In the
20 figures:
Figure 1 is a diagrammatic view of a turbine
engine fan platform obtained by the method of the
invention;
Figure 2 shows very diagrammatically how the two
25 sets of layers of yarns are arranged in a threedimensional
woven fiber blank for making a fiber preform
for a platform of the kind shown in Figure 1;
Figures 3 and 4 show successive steps in making a
fiber preform for a platform of the kind shown in
30 Figure 1 from the fiber blank of Figure 2; and
Figures 5, 6, and 7 are weft planes of the
Figure 2 fiber blank, respectively on planes V-V, VI-VI,
and VII-VII.
35 Detailed description of the invention
The invention is applicable to any n-section
reinforcing part that comprises a case having a step at
at least one of its longitudinal ends and a stiffener
having two legs that extend from one face of the base.
A preferred application of the invention is to be
found in particular in fabricating platforms for a
5 turbine engine fan, such as the platform shown in
Figure 1.
The platform 10 in Figure 1 comprises a first
portion forming a base 12 and a second portion forming a
stiffener 14. The base 12 is substantially elongate in
10 shape with a top face 12a and a bottom face 12b. At each
of its longitudinal ends, the base has a respective step
16, i.e. its ends are folded inwards along lines that
extend substantially transversely. These steps 16 enable
the platform to be fastened to the structure of the
15 turbine engine.
The stiffener 14 of the platform comprises two legs
18 (or tabs) that extend from the inside face 12b of the
base over its entire length. The legs serve to stiffen
the platform so as to avoid it moving under centrifugal
20 force as a result of the speed of rotation of the fan.
The platform 10 as made in this way presents a
section that is n-shaped, as shown by dashed lines in
Figure 1.
Figure 2 is a highly diagrammatic view of a fiber
25 blank 100 from which a fiber preform for a platform can
be shaped, prior to injecting resin or densifying with a
matrix, and possibly also machining, in order to obtain a
fan platform made of composite material and as shown in
Figure 1.
30 The blank 100 comprises a first blank portion 102
and a second blank portion 104 obtained by threedimensional
weaving or multilayer weaving, and only the
envelopes of these two portions are shown in Figure 2.
After shaping, the first portion 102 is to constitute a
35 portion of the fiber of the platform that corresponds to
a base preform. The second portion 104 is intended,
after shaping, to constitute another portion of the fiber
preform for a platform that corresponds to a stiffener
preform.
The two blank portions 102 and 104 are in the form
of strips extending generally in a direction X that
5 corresponds to the longitudinal direction of the platform
that is to be made. The two fiber blank portions may
have the same width and the same length, which width and
length are selected as a function of the dimensions of
the platform that is to be -made.
10 The two blank portions 102 and 104 are woven
simultaneously by three-dimensional weaving without
interlinking except along a central strip referred to as
the interlinked strip 106 that extends longitudinally
between their two longitudinal ends. An example of how
15 the connection is made between the portions of the blank
along the central strip is described below with reference
to Figures 6 to 8.
At each of its longitudinal ends, the central
interlinked strip 106 between the two blank portions 102,
20 104 flares towards the respective opposite sides 102a and
104a of the two blank portions in first and second zones
108 and 110 that correspond to the locations of the steps
of the base of the platform.
Thus, in the weaving advance direction F of the two
25 blank portions 102 and 104 as shown in the figure, the
interlinked strip 106 extends at an upstream end over the
entire width of the blank portion. Starting from a first
transverse fold line 108a corresponding to the beginning
of the first zone 108 (also referred to as the upstream
30 zone), the width of the interlinked strip narrows to a
second transverse fold line 108b corresponding to the end
to the first zone 108. At the opposite end, the
interlinked strip between the blank portions expands once
more (in the transverse direction) from a first
35 transverse fold line llOa corresponding to the beginning
of the second zone 110 (also referred to as the
downstream zone) to a second transverse fold line 110b
corresponding to the end of the second zone 110 from
which the interlinked strip extends over the entire width
of the blank portions.
As shown in Figure 3, the two fiber blank portions
5 102 and 104 are then folded towards the inside at the
above-defined fold lines 108b and llOa (which lines are
common to both blank portions). Thereafter, the blank
portions are folded towards the outside at the other fold
lines 108a and 110b so as to give the two ends of the
10 fiber blank rims suitable for attaching the platform to
the structure of the engine. The steps are thus defined
by fractions of the blank portions that are defined
between the fold lines 108a and 108b for the upstream
step and between the fold lines llOa and 1lOb for the
15 downstream step.
Because of the lack of interlinking between the
portions of the fiber blank outside the central
interlinked strip 106, the non-interlinked portions 112
of the second blank portion 104 can then be folded (or
20 deployed) inwards so as to form leg preforms (Figure 4).
The particular shape of the non-interlinked zones
between the blank portions in the vicinity of the steps
enables leg preforms 112 to be obtained that do not have
any folds along their entire length.
25 A fiber preform for the platform that is to be
fabricated is then obtained by molding, with the first
fiber blank portion being deformed so as to take on
shapes that match the profiles of the blades between
which the platform is to be mounted. The final shape may
30 be given by deforming the preform prior to molding or by
machining the part after molding. This produces a
preform with a base preform portion having its steps and
a stiffener preform portion having its two legs (or
tabs).
35 The fibers of the fiber preform are made of a
material that is selected as a function of the intended
application, e.g. they are made of glass, of carbon, or
of ceramic.
The matrix is deposited in the fiber preform in
order to obtain a composite material platform while the
5 preform is held in the mold, at least until the preform
has been stiffened (or consolidated). The matrix is of a
nature that is selected as a function of the intended
application, for example an organic matrix obtained in
particular from a resin that is a precursor of a polymer
10 matrix such as an epoxy, bismaleimide, or polyimide
resin, or a carbon matrix, or a ceramic matrix. With an
organic matrix, the fiber preform is impregnated with a
composition containing the resin that is a precursor of
the matrix, either before being shaped in tooling or
15 after being shaped, in which case impregnation may be
performed for example by infusion or by a process of the
resin transfer molding (RTM) type. With a carbon matrix
or a ceramic matrix, densification may be performed by
chemical vapor infiltration (CVI) or by impregnation with
20 a liquid composition that contains a resin that is a
precursor for carbon or for ceramic, and then performing
pyrolysis or ceramization heat treatment on the
precursor, which methods are themselves well known.
The platform is machined to its final dimensions
25 after the fiber preform has been injected/densified.
With reference to Figures 5 to 7, there follows a
description of an example of three-dimensional weaving of
the fiber blank 100, and more particularly of the
interlinking between the blank portions 102 and 104 along
30 the central strip 106.
Figures 5, 6, and 7 are highly diagrammatic views of
weft planes of the Figure 2 fiber blank 100, respectively
on planes V-V, VI-VI, and VII-VII. The term "weft" plane
of the fiber blank is used to mean a plane perpendicular
35 to the warp yarns and containing a column of weft yarns.
The weft plane V-V corresponds to a plane halfway
between the two longitudinal ends of the fiber blank.
The weft plane VI-VI lies in the zone 110 corresponding
to the location of the downstream step of the base of the
platform, while the weft plane VII-VII is downstream from
the zone 110 (in the weaving advance direction F ) .
5 Between its outer and inner faces 114a and 114b, the
fiber blank 100 comprises nine layers of warp yarns c, to
c9 and nine layers of weft yarns t, to t,, with two
crossings between yarns of the group of weft yarns t, to
t, and the yarns of the group of weft yarns t, to t, in
10 crossing zones 116a and 116b.
Non-interlinked zones 118a and 118b, represented by
lines in Figures 5 to 7, are arranged between adjacent
layers of warp yarns, specifically between the layers c,
and c,, these non-interlinked zones extending in the side
15 portions of the fiber blank 100 between its opposite side
edges 100a, lOOb and the crossing zones 116a and 116b.
These non-interlinked zones are zones that are not
crossed by weft yarns for the purpose of interlinking
warp yarns situated on either side of the non-interlinked
20 zones.
The crossing zones 116a and 116b define between them
the central interlinked strip 106 along which the two
blank portions are interlinked. Thus, as shown in
Figure 6, the crossing zones 116a and 116b are spaced
25 further apart from each other in weft plane VI-VI of
Figure 2 than in the weft plane V-V. As a result the
interlinked strip flares downstream between the two
portions of the blank. Similarly, in Figure 7 that
corresponds to the weft plane VII-VII in Figure 2, there
30 is no longer any non-interlinked zone between the two
portions of the blank, such that both portions are
interlinked over their entire width and form a single set
of layers of yarns.
As mentioned above, after the fiber blank 100 has
35 been woven, the portions 120 and 122 of the blank that
are adjacent to the non-linked zones 118a and 118b and to
the inside face ll4b are deployed towards the inside so
as to form the leg preforms 112.
Naturally, the number of layers of warp yarns and of
weft yarns in the various portions of the preform (base
5 and legs) could be different from those in the example
described, providing three-dimensional weaving is
performed in each of these blades.
In addition, the number of yarns in the groups of
yarns that cross twice could also be different from the
10 numbers in the example described, providing there is at
least one yarn in each group. In particular,,there is no
need for all of the weft yarns involved in weaving the
legs of the preform also to be involved in the two
crossings with the weft yarns that are involved in
15 weaving the base.
Alternatively, the interlinking between the blank
portions 102 and 104 of the fiber blank along the
interlinked strip 106 may be made by adding additional
yarns (e.g. by stitching or sewing).
20 Finally, in the above description, it is naturally
possible to interchange the terms "warp" and "weft".
More generally, it should also be observed that the
non-interlinked zones created by the above weaving could
be obtained in other manners that are themselves known,
25 in particular by de-interlinking in the weave without
crossing yarns from the two sets of layers of yarns.
For example, the fiber structure may have a portion
corresponding to the above-described central interlinked
strip that is formed by three-dimensioned weaving with an
30 interlock weave interlinking the layers of yarns over the
entire thickness of the fiber structure, and two portions
corresponding to the legs of the platform in which each
two adjacent layers of yarns (e.g. the layers c, and c, of
Figure 5) are no longer interlinked for linking together
35 a plurality of layers in the thickness of the structure,
but are woven with a surface satin weave so as to create
two non-interlinked preform portions.

CLAIMS
1. A method of fabricating a reinforcing part (10),of nshaped
section out of composite material, the part
comprising a first portion forming a base (12) that
5 presents a step (16) at least one of its longitudinal
ends, and a second portion forming a stiffener (14)
having two legs (18) that extend from a face (12b) of the
base over at least a fraction of the length thereof, the
method comprising:
10 making a first set of a plurality of layers of yarns
that are interlinked by three-dimensional weaving to form
a first fiber blank portion (102) that is to form a base
preform;
making a second set of a plurality of layers of
15 yarns that are interlinked by three-dimensional weaving
to form a second fiber blank portion (104) that is to
form a stiffener preform, yarns of the second set of
layers of yarns being interlinked by weaving with the
yarns of the first set of layers of yarns in a central
20 interlinked strip (106) extending longitudinally between
the two longitudinal ends of the first fiber blank
portion and flaring towards the side edges (102a) thereof
in a zone (108, 110) corresponding to the step of the
base;
25 shaping the two fiber blank portions to obtain a
single-piece fiber preform (100) having a portion forming
a base preform and a portion forming a stiffener preform;
and
depositing a resin in the fiber preform to form a
30 matrix so as to obtain a composite material reinforcing
part comprising fiber reinforcement constituted by the
preform that is densified by the matrix.
2. A method according to claim 1, characterized in that
35 the interlinking of the yarns of the second set of layers
of yarns and the yarns of the first set of layers of
yarns by weaving is obtained by crossing said yarns
respectively along the interlinked strip.
3. A method according to claim 1 or claim 2,
5 characterized in that when the base of the reinforcing
part presents a step at both of its longitudinal ends,
the interlinked strip between the yarns of the first and
second sets of layers of yarns flares toward the side
edges of the first fiber blank portion in each of the
10 zones corresponding to the steps of the base.
4. A method according to claim 3, wherein, upstream from
the zone corresponding to the upstream step of the base
and downstream form the zone corresponding to the
15 downstream step of the base, the interlinked strip
between the yarns of the first and second sets of layers
of yarns extends transversely over the entire width of
said first fiber blank portion.
20 5. A method according to any one of claims 1 to 4,
characterized in that shaping comprises forming at least
one step by folding the two fiber blank portions along a
common, substantially-transverse fold line (108b, 110a).
25 6. A method according to any one of claims 1 to 5,
characterized in that the shaping of the second fiber
blank portion comprises folding the non-interlinked
portions (112) of the second fiber blank portion in a
direction that is substantially perpendicular to the
30 first fiber blank portion so as to form two leg preforms.
7. A reinforcing part (10) of n-shaped section made of
composite material, comprising a base-forming first
portion (12) that presents a step (16) at at least one
35 of its longitudinal ends, and a stiffener-forming second
portion (14) having two legs (18) that extend from a face
(12b) of the base over at least a fraction of the length
thereof, characterized in that the first and second
portions are interlinked along a central interlinked
strip (106) that extends longitudinally between the two
longitudinal ends of the first portion and that flares
5 towards the side edges (102a) thereof in a zone (108,
110) corresponding to the step of the base.
8. A reinforcing part according to claim 1, characterized
in that it is made of organic matrix composite material.
10
9. A reinforcing part according to claim 7 or claim 8,
characterized in that the first and second portions are
interlinked by respective crossings of the yarns that
constitute them in the interlinked strip.
15
10. A reinforcing part according to any one of claims 7
to 9, characterized in that downstream from-the zone of
the first portion corresponding to the step of the base,
the interlinked strip between the first and second
20 portions extends transversely over the entire width of
said first portion.
11. A reinforcing part according to any one of claims 7
to 10, characterized in that the first portion includes a
25 step at each of its longitudinal ends.
12. A reinforcing part according to any one of claims 7
to 10, characterized in that it constitutes a fan
platform of a turbine engine.
30
13. A turbine engine fitted with at least one fan
platform according to claim 12 or fabricated by the
method according to any one of claims 1 to 6.
Dated this 08.07.2014
[RANJNA MEHTA-DU'IT]
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANT[S]
IN THE UNITED STATES PATENT AND TRADEMARK OFFICE
PATENT APPLICATION
5 Entitled: A composite material reinforcing part of nshaped
section, in particular a platform for
a turbine engine fan, and its method of
fabrication
10 Inventors :
Assignee :
ABSTRACT OF THE DISCLOSURE
The invention relates to a method of fabricating a
reinforcing part of n-shaped section out of composite
material, the method comprising making a first set of
20 layers of interlinked yarns by three-dimensional weaving
to form a first fiber blank portion that is to form a
base preform, making a second set of layers of
interlinked yarns by three-dimensional weaving to form a
second fiber blank portion that is to form a stiffener
25 preform, yarns of the second set being interlinked with
yarns of the first set by weaving over a central
interlinked strip that flares towards the side edges of
the first fiber blank portion in a zone corresponding to
the step of the base; shaping the two fiber blank
30 portions to obtain a single-piece fiber preform having a
portion forming a base preform and a portion forming a
stiffener preform; and depositing a resin in the fiber
preform to form a matrix. The invention also provides a
reinforcing part of n-shaped section obtained by the
35 method.