FIBROUS STRUCTURE HAVING VARiAliLE NUMBERING YARNS
Background of Lhe inventi on
The present invention relates to making parts out of
composite material, and more particularly to making
reinforcing fiber. structures for such pants.
A particular field of appl i cation ol" the invention
l.ies in making parts of structural composite manorial,
i.e. parts having a fiber reinforcing structure that is
donsified by a matrix. Composite materials make it
poss i blc to fabricate parts that present overaJ1 weight
that is less than that of. the same parts when made ol
me Lai.
Tn the context of making fiber structures by
multilayer weaving so as to produce the fiber
rei EI for cement for a composite material part, such as a
blade for an aeroengine,. it is necessary during weaving
of the structure to withdraw yarns both in, Lho warp
direction and "i.ti the weft direction in order to match
reductions in the thickness ol" Lho part, e.g. in the
fas toning or i it the tra f .ling; edge ol" the blade, so as to
obtai n a fiber preform that presents the quasi-fi rial
shape and dimensions of the blade (i.e. thai presents its
"net shape").
In Lho portio_ns_of the I. Lbor structure that have a
large number of layers of yarns, withdrawing yarns has
' li t L.l.e influence on varyi r\q the densi ty of the f i.bors,
which-density remains relatively constant. Nevertheless,
once the number of layers decreases significantJ y, e.g.
when there remain only four or fewer 3 ayers of weft yarris
or of warp yarns, then the variation in fiber density
becomes too great when another layer of yarns is
withdrawn.
Object and summary of the invention
It is therefore desirable to be able to have fiber
structures available with the quasi-final shape and
?.
dimensions of the composite material paft that is to be
made, in particular in porti.ons thereof that arc? of
decreasing thickness, while havi nq fiber density varying
minimally i.n such porti otis,
To this end; the invention provides a fiberstrucl-
tfrc for reinforcing a composi te material part, s'a i d
structure being woven as a s i.iigle piece by multilayer
weav i ng between a i i.rst plurality ol" layers of yarns
extending in a first direction and a second plurality of
layers of yarns extending in a second direction,
the structure be ing characterj aed in that at least
one of the first and second pluralities of layers of
ya rns includes at I cast one layer of yarns of variable
weight, each variable-weight yarn beinq made up of a
separable assembly of individual yarns each having a
determined weight; and
in that the fiber structure includes at least one
portion of reduced thickness i.n which the variable-weight
yarns present weight that is less than the weight
presented by said variable-weight yarns prior to said
portion of reduced thickness.
Ry using yarns o( variable wei ght, it is possibt e Lo
adjust the weight of the yarns as a function-of the
decrease in the'number of layers or yarns in portions of
the structurethat are o( small thickness, thereby
controlling variation in fiber density so thaL such
var i a tion is minimi v,ed. The unit - yarns making up the- •-
yarns of variable weight may be extracted progressively
i rom the fiber structure, thus mak I.ng it possible to
avoid any 'sudden variation in the fiber density, in
particular .in portions of srna E1 thickness that include a
smai I. number of layers of yarns.
In a particular aspect of the invention, the weight
ol: each individ.u^ i yarn of a varid able-weight yarn ia a
divisor of the weight of: said variable-weight yarn.
in another aspect of the invention, the variableweight
yarns are selected from at least one of the
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following types of yarn: twisted yarns, plied yarns, and
covered yarns.
In yet another aspect of: Lhe invention, each
variable-weight yarn has an initial wei-ghL of 48K, and it
is_made up of one of the following separable assembt ics
of individual yarns:
- two individual yarns, each weighing ?4K;
* three individual yarns comprising one weighing ?QK
and two others, each weighing 12K; and
• tour yarns, each weighing 12K.
According to a particular oharact oris tic of the
invention, in the porLion of reduced thickness, the fiber
structure has three layers of the first plurality of
layers of yam* and two layers of Lhe second plurality of
1aycrs of yarns.
Accord"? ng to another parti cuJ ar characteristic of
tho invention, the portion of reduced thickness includes
a I. least one zone starting from which a layer of Lhe
first or second plurality of layers of yarns is
interrupted, said interrupted layer of yarns being
replaced thereafter in' the portion of reduced thickness
by individual yarns of a layer of variable-weight yarns
adjacent to said interrupted layer.
. The invention also provides a composite material
part comprising a t iber structure of the i iw_c_ntio_n
densificd by a matrix. In particular, the part, may
constitute-an aeroengine blade. '
The invention also provides a turboprop fitted with
a plurali Ly of blades of the i nvention,
The invention also provides an aircraft fitted with
at least one turboprop of the invention.
Brief description oi" the drawings
Other characteristics and advantages of the.
invention appear LYoni the following description of
particular embodiments of Lhe invention given as nonlimiting
examples and with reference to the accompanying
i
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drawings, in which:
• Figure 1 is a diagrammatic view showing multilayer
weav Lng of a fiber structure for fabricatinq an
aerbengine blade in an embodimenL of the invention;
* Figures 2A to ?H show eight successive weave
planes in weft section of a portion of the Figure \ fiber
structure that is to form the trailing edge of the blade
that i s to be made in an embodiment of the i nvention;
• Figures 3 A' to 311 show e j ghL successive weave
planes in weft sect Loii of a portion of the Figure 1 fiber
structure that is to form Lhe trailing edge of the blade
that is to be made in another embodiment of the
invention;
* Fi gures 4A to 4ti show eight successive weave
planes in weft section of a portion ol the figure 1 fiber
struelure that is to form the trailing edge "of the blade
that is to be ftiado in another embodiment of the
invention;
• Figures 5 A to 5H show slight successive weave
planes in weft, section of a portion of the Figure 1 fiber
structure that is to form the trailing edge of the blade
that is to be made in another embodiment of the
invention;
• Figure 6 is a diagrammatic perspective view of a
blade fiber preform obtained I rom the Figure "1 fiber
structure;, and
---- Figure 7 is a' d.i agr.ammatic perspective-v Iew of a
composite material blade obtained by densifying the
Figure 6 preform with a matrix.
Detailed description of embodiments • __ •
The invention applies in general to making fiber
structure suitable for constituting fiber reinforcement,
referred to as preterms, for use in fabricating composite
material parts, in particular aeroengine blades, the
parts being obtained by densifying fiber structures with
a matrix. Typically, the matrix is made of a res.En, for
i
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composite materials that are used up to temperatures that
are relatively low, typically up to 3Q0DC, or by a
refractory material such as carbon or ceramic for
Lhermostrtictural composite.maLorialsFigure 1 is a highly diagrammatic view of a Fiber
structure 2 00 for forming the fiber re Lrl for cement of ait
aeroengine blade.
The liber structure 200 is obtainod by multilayer
weaving performed iit known manner using a jaequard" type
loom having a bundle of vrarp yarns or strands 20-1
organized as a plurality of layers, the warp yarns being
interlinked by we I L yarns 202 Likewise arranged as a
plurality of layers.
The fiber structure 200 is woven i n the form of a
strip extending generally, in a direction X corresponding
to the longitudinal direction of the blade that is Lo be
made. The fiber structure presents thickness that vari es
in a manner that is determined as a function of the
longitudina I thickness of. the airfoil profile o'f the
blade that is to be made. In i ts portion that is to form
a root preform, the fiber structure 200 presents extra
thickness 2-0J determined as a function of the thickness
of the foot of the blade that is to be made and that may
be implemented, for example, fry using yarns of greaLur
weight or by nsing an insert. The fiber structure 200 is
extended by a portion of decreasing thickness 204 that is
to form the Lang of the b tade followed by a portion 205
that is to form the airfoil ol the blade. In a direction
perpendicular to the direction XF (.he portion 205
presents a profile of thi cknosd that" varies between 1Ls
edge 205a that is Lo form the heading edge ol tho blade
and its edge 205b that is to form the trailing edge of
the blade that is Lo be'made.
Examples of making a fiber prerform for forming the
liber reinforcoftiont of an aeroengine blade are described
in particular in detail in the fol towing documenLs:
US 7 101 154, OS 7 241 112, arid WO 2010/061140, the
i
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contents of which is incorporated herein by reference.
In the examp]es described below, the outer faces, ot
"skins", of the fiber structure are made nsi t\q a satin
typo weave, while the internal portion of the structure
is made us ing an inter]ock type weave, as described in
document WO 2006/136755, the content of which is
.incorporated herein by reference. The term "interlock"
is used herein to mean a weave in which each layer of
warp'yarns interlocks a plurality ol layers of weft yarns
with all of the yarns i.n a given warp column having the
some movement in the weave piano.
The fiber structure of the invention may in
particular, but not exclus i vcly, be woven nsi ng fibers
made of carbon or of ceramic such as silicon carbi de,
The IJber density in the fiber structure is determined
locally as a function of the density of yarns present at
the location of Lhc structure under consideration.
The fiber structure 200 is woven as a single piece
and after the non-woven yarns have been cut it i s to
present the quasi-final shape and dimensions of the blade
{i.e. the "net shape") * For this purpose, "i n the
portions of Lhc fiber structure in which thickness is
reduced, such as the portion situated between the edqes
205a and 205b"of the structure, the thickness of the
preform is reduced by progressively withdrawing layers of
warp yarns and of weft yarns during weaving.
In 'accordance with the- invention, the fiber
structure is woven w.i th yarns including at least some
that are so-called yarns of, "variable weight", i.e. yarns
that are made up of a separable assembly of individual
yarns, each having a determined weight, with the sum of:
the weights of all of the individual yarns rtiakinq up a
variable-weight yarn giving its' initial weight.
The, weight of a yarn corresponds to its size (and
depending on the type of material constituting the yarn
i
its density will vary so the volume it occupies for a
given weight will be different), and it may be detinod in
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various ways. Tti particular, it may bo defined as the
weight per unit length of the yarn, which is generally
expressed .i n Lex, corresponding to the weight in grama of
1000 meters of. yarn, or "in decitex (dtexj corresponding
5 to the weight (in grants) of "10,000 meters of yarn. The •
weight of the yarn may also be defined as the number of
filaments that make it up. Under such circumstances, the
weight of the yarn is expressed i.n "K" which corresponds
Lo the number of thousands of filaments per yarn, For
10 example a IK yarn has 1000 filaments. Other units of
measurement may. also be used to give the weight of a
yarn, such as, for exampfe, its metric number (Nrn)
expressing the number of meters represented by one qram
of a yarn.'
15 Tn the present inventi.on, the individual, yarns
making up a yarn of variable weight may be assembled
together in various ways. In particular, the variableweight
yarn may be an assembled yarn that results from
uniting a plural 1ty of individual yarns without
20 s kqni.ficant twisting*
Variabfe-weight yarns are advantageously reduced in
- weight when redue i.rsg the thickness ol" the fiber structure
by withdrawing a layer of" yarns in order to -mi.iiimize 'the
1 variation in the fiber density E n these portion's cf
2b reduced thickness. Tl is preferable to reduoo__the weight
of variable-weight yarns when the fiber structure is down
to four"layers (weft or warp) or even fewer. This
reduction may be applied equally well to w&rp yarns, to
weft yarns, or both to warp and to weft yarns. The
30 location in the fiber texture from which the weight of a
variable-weight yarn is reduced is independent I"rom the
location at whi ch a layer of yarn (warp or weft) is
withdrawn in order to narrow down the structure.
As explained below, variable-weight yarns may be
3b used for implementing a progressive exit from the fiber
- structure for the yarns in a 1 ayor of yarns. Vari abieweight
yarns may also be used to repl ace yarns of an
:• L-:^.^^.^^f;^fi^;-:;'.-''-
adjacent Layer that has been extracted complete!y from
the fiber structure, with some of the .i ridividual yarns of
the variable-weight yarn being conserved in the layer to
which they belonged initially in order to continue '
5 weaving that layer while the other individual, yarns are
deflected to continue weaving the extracted adjacent
t ayor of the structure.
Example embodiments of a fi ber structure l.or
constituting reinfo-rcement in a compos i ee material blade
10 .in accordance with the invention are described below. In
all of these examples, the weaving i 3 performed on a
jacquard type J 00m,
Example J
15 figures 2A Lo 2H. show eight successive weave planes
of a portion of a fiber structure SI obtained by
multilayer weaving, the weft yarns bei ng shown in
section. The portion of the fiber structure SI shown
corresponds to the portion of the fiber reinforcernent
20 that is situated at the tra I ling edge ol. the coinposi L.e
material blade, such as the portion 205b of the fiber
structure 200 in Figure 1. The -eight, weave planes shown
i.n Figures 2A Lo 211 correspond to eight successive stages
of variation, in the weave of variable-weighs yarn 70 is extracted from the structure
S3, with weaving continuing wi Lh the other individual
yarn 72 weiqhing 24K. In figure AF, the individual yarn
31 oJ: the variabl o-weight yarn 80 is extracted from the
structure S3,' with weaving continuing with the other
10 individual -yarn 82 weighing 24K. In Figure 4G, the
individual yarn 91 of the variable-weight yarn 90 is
extracted Iron* the structure S3, with weaving continuing
with the other individual yarn 92 weighing 24K.
1b Example A
Figures 5A to 511 show e ight success i ve weave plane a
in a porti.oii.of the f Lbcr structure S4 obtained by
multilayer weaving, the weft yarns being shown in.
section. The portion of .the Tiber structure S4 shown
20 corresponds to the portion of the Liber reinforcement
that is situated at the trailing edge of the composite
material blade, like the portion 205b of the fiber
structure 200 of Figure 1^ The eiqht weave planes shown
in Figures 5A to 511 coxrespond ta eight successive stages
25_ of variation in the weave of the structure SA. These
eight planes do not fully define the weave of the
structure S4. Tfi Figures 5A -and 513, the I i.ber structure
comprises three layers of weft yarns t10D, t110, and tlZ0.
Tn Figure 5C, a half-layer of the layer t110 is withdrawn
30 "so as to leave only the half-Jayor t'lia in the structure
S3. In F.iqurcs 5D to btt, the' hall":-l ayer t[
llt> is
withdrawn so as to leave only the two layers t1 M and t1iJ(t
in the structure 54«
In the p Lanes shown i n Figures 5A l.o 5F, the .layors
35 or haW-iayers of weft yarns are woven with three warp
yarns 100, 110, 120, the warp yarns ]Q0 and 120 be.i rig
4!stLl--.
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woven with a satin type weave and the warp yarn 110 beinq
woven with an interlock typo weave.
The warp yarn 100 is variable-weight yarn made up of
a separable assembly ot four individual yarns 101 to 104
5 each weighing 12K. The warp yarns 110 and 120 are
variable-weight yarns each made up of a separable
assembJy of two individual yarns 111 £ 112 oi" 121 & 122
respectively, each individual yarn weighing 24K.
In Figure 5D, the i ndividual yarn 101 oJ." the
10 variable-weight yarn 100 i# extracted from the structure
£4,-with weaving continuing with the throe remaining
individual yarns 102, 103, and 104, each weighing 12K."
In Figure bE, the individual yarn 111 of the
variable-weight yarn 110 is extracted I torn the structure
15 S4, wf Lh weaving continui tig with the other indi vidual
yarn 112 weighing 24K.
In L'igure 5F, the i ndividual yarn 1 21 oT .the
variabt e-weight yarn 12 0 is extracted from the structure
S4y with weavinq continuing with the other individual
20 yarn 122 weighing 24K,
in Fiqure 5G, the individual, yarn 112 is extracted
from the structure $4 such that there no longer remains
any individual yarn derived from the variable-weight yarn
110.' Heaving of the individual yarn 112 in the core is-
?h continued by the indi vidual yarns 103 arid 104, each
weighi ng 12K, while weavi nqi in the skin, is cont i nucd by
the individual yarn 102 weighing -1 2.K,
Onco the weaving o! the fiber structure has been
completed, the non-woven yarns-arc cut, and in parti eular
30 those that have been extracted from Lho texture in the
wi l.hdrawal" parts in surface continuity and i n surface
discontinuity. This produces the Tiber preform 300 shown
in Figure d, which preform is woven as a single piece.
Thereafter" the fiber prefoqii 300 is densities- in
3b order to form a b.l ade 10 o£ composite material as shown
in Figure 7. The fiber preform that is to constitute the
fiber reinforcement of the part that ,i s to be fabricated
-•••••xiw&mi&i^
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is densified by filling in the pores of the preform,
throughout all or pari of its volume, with the material
that cons Li tutos the matrix. This densification may be
performed in known manner using a .liquid technique or a -
5 gaseous technique (chemical vapor infiltration (CVl)), or
indeed by using both of these techniques one after the
other,
The li qui.d technique consists in imp re gnat", i ng the
preform with a liquid composition containing a precursor
10 • for |:he material of the matrix. The precursor is
generally in the form of a polymer, such as a high
performance epoxy resin, possibly diluted in a solvent.
The preform is .placed in a moJ.d suitable for being closed
in leaktight .manner with a recess that has the shape of
15 the final molded blade. Thereafter, the mold is closed
and the liqu i d precursor of the matrix {e.g. a resin) is
Injected into the entire recess so as to impregnate all
of the fiber structure of the preform.
The precursor is transformed into the matrix, i.e.
20 it is polymerized, by applying heat treatment, generally
by heati ng the mold after e Iiminating any sol vent and
curing the polymer, with the preform continuing to be
held in the mold that haa a shape corresponding to the
shape of -the part that is to be made.*
25 When forming a matrix of carbon or of ceramic, the
heat treatment consists in pyrolyzing the precursor in
order; to transform the matrix-i nto a carbon or ceramic
matrix depending on the precursor used and on pyrolysis
conditions. By way of exatVipLe, liquid precursors for
30 - ceramic, in particular for Sic, may be resins of the
pol yearbosilane ("PCS) type, or of the
polytitanocarbosilane (PTCS) type, or of the pel ys i lazane
(PSft} type, whereas 1iquid precursors of carbon may be
resins having a relative1y high coke content, such as
35 phenolic resins. A plurality of consecutive cycles, each
running from impregnation to heat treatment, may be
performed in order to achieve a desired degree of
•;ji--. 13:-^ _
14
densi.l icatioii.
According to an aspect of the invention, in
particular when forming an organic matrix, the fiber
preform may be densified by the well-known resin
b transform molding {RTM) method- in the RTH method! the
fiber preform is placed in a mold presenting the outside
shape of the part that .is to be made. A thermosetting
res in is injected i.nto the inside volume of the mold that
contains Lho fiber preform. A pressure gradient is
10 generally established in sal.d inside space between the
location where the resin is injected and orifices for
exhausting Lho resin in order to control, and optimize the
way the preform E.s impregnated by the resin,
Tn known manner, the fiber preform may also be
15 densified using a gaseous technique of chemical vapor
E n {."iltration (CVT) of the matrix. The fiber preform
corresponding to the fiber reinforcement of the blade
that is to be made is placed in an oven into which a
reaction gas is admitted. The "pressure and the
20 temperature that exist i nside the oven and the
composition of the gas are seleeted in such a manner as
to enable the gas Lo diffuse within the pores of. the
preform so as to form the matrix therein by depositing a
solid material En the core of the material1 hin contact .
25 with the fibers, which solid material ia_the result of_£_
component of the gas decomposing or of .a reaction between
a plurality of components, in contrast to the-pressure
and temperature conditions that are specific to chemicaL
vapor deposition tCVD) methods that lead to deposition
30 taking place solely "on the surface oE'the materia J .
An Si.C matrix may. be formed using
meLhyitrichlorosil.ane [UTS] that gives Sic by
decompose Li on of the MTS, whereas a carbon matrix may be
obtained using hydrocarbon gases such, as methane and/or
35 propane that produce carbon by cracking.
It is also possible to perform densifination by
combi.n ing the liquid technique and Lhe gaseous technique
15
so as to facilitate implementation, limit cost, and limit
the number of fabri cation cycles while still obtaining
characteristi es that are satisfactory lor the intended
utilination. . '
After densification, a composite material blade 400
is obtained, "as shown in Figure 1, that includes a root
403 in i Ls bottom portion that is constituted by the
extra thickness 203 of the fiber structure 200, which is
extended by a tanq 404 formed by tho portion of
decreasing thickness ?04 of the structure 2 00, and by an
a.lrfoil 405 formed by the portion 205 of tho. fiber
structure 200, and extending perpendicularly relative to
tho longitudinal direction of the blade between a leading
edge 4'05a and a trailing edge 405b,
16
CLAIMS
1, A fjber structure for reinforcing a composite material
part, said structure be.i ng woven as a single piece by
multilayer weaving between a first p.l u ra 1 1 l.y of layers of
5 yarns extending i n a fi.rst direction and1 a second
plurality of layers of yarns ox Lending in a second
direction,
the structure be.i nq characterized in that at least
one of the first and second pluralities ol layers of
10 yarns includes at least one layer of yarns of variable
. weight, each variable-weighL yarn being made up of a
separable assembly of individual yarns each having.a
determined weight; and
in that the fiber structure Includes at least one
15 portion of reduced thickness in which the variable-weight
yarns present weight that is less than the weight
presented by said variable-weight yarns prior Lo said
portion of reduced thickness.
20 2, A structure according to claim 1, characteri*ed in
that the weight of each individual yarn of a variableweight
yarn is a divisor ol. the weight of said variableweight
yarn,
2b 3,_A structure according to claim 1 or c l.aiin 2,
characterised in that the variable-weight yarns ar^.
assembled yarns. '- -
A. A structure accordi ng to any one of claims 1 to 3,
30 .characterized in that, each vari abi c-weight yarn has an
.. initial weight of 48K, and in that it 'is made up ol one
of the following separabte assemblies of individual
yarns:
• two individual yar.ns, each weighing 24K;
35 • three individual yarns eompri s Lug one weighing 24K
and two others, each weighing 12K; and
• four yarns, each weighing 12K.
n
5. A s t r u c t u r e decorriiny to any one of claims 1 to 4,
c h a r a c t e r ! -zed i n t h a t , in the portion. of reduced
L-hi ckiiflss, the f i b e r s t r u c t u r e has three "1 ayers of the.
5 first p l u r a l i t y ol layers of yarns and two layers of the
Second pi ura l..i l:y of l a y e r s of yarns .
6. A s t r u c t u r e according to any one of claims -1 to 5,
cha r a c t e r l z e d in t h a t the p o r t i o n of reduced thickness *
.10 i no 1 ndes at l e a s t one zone s t a r t i n g from which a .1 ayer of
the f i r s t or second p l u r a l i t y of. l a y e r s of yarns is
iriLer.rupl.ed, said i n t e r r u p t e d layer of yarns being
replaced t h e r e a f t e r in the portion ol reduced thickness
by i n d i v i d u a l yarn;. ol" a layer of variable-weight, yarns
15 aid ) a c e n t to said i n t e r r u p t e d l a y e r.
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7. A compos i te material part comprising fiber
reinioroenient densified by a resin matriK in which the
fiber reinforcement i s formed by a I iber structure
?.{) accord i nq to any one of claims. 1 to 6 and densified by a
matrix.
H , A pa rl. aooordt ng to claim 1, characteri zed in that i I:
constitutes -an aeroengine blade.
25
9. A part according to claim R, character! xed i \\ that the
reduced thickness portion of ,the fiber structure
-corresponds to the port i on o\ the J j.ber reinforcement
that, forms the trailing edge of the blade,
'30 •
10. A turboprop including a plurality of blades according
to claim 9.
11. An aircra t:t \\\ tted with at least one. turboprop