Fibrous reinforcement for the manufacture of a composite part intended to be articulated with other parts

Abstract

Fibrous reinforcement for manufacturing a composite part intended to be articulated with other parts The present invention relates to a fibrous preform of a core portion of a fibrous reinforcement for a part made of composite material, the preform having a slender shape along a longitudinal direction (X) and being formed by first threads (C1-C16) extending along the longitudinal direction with second threads (t1-t8) transverse to the first threads, the preform comprising two longitudinal ends intended for articulation with other parts and a middle zone located between the longitudinal ends, each longitudinal end having a thickness greater than a thickness of the middle zone, the middle zone comprising a stiffening portion (102c) comprising first non-woven threads (C5-C12) and each longitudinal end comprising a three-dimensional weaving of the first threads of this stiffening portion with second threads.Figure for abstract: Fig. 2.

Description

Title of the invention: Fibrous reinforcement for the manufacture of a composite part intended to be articulated with other parts Technical field

[0001] The subject of the invention is a fibrous preform intended to form a part of a fibrous reinforcement of a part made of composite material, which part is intended to be articulated with other parts at its ends, and an associated manufacturing method. Prior art

[0002] The use of composite materials as a replacement for metallic materials can be proposed with a view to lightening, which is a constant concern in the particular case of aircraft parts. In this view, document US 7,704,429 has proposed the manufacture of landing gear struts made of composite material which comprise regions, called yokes, which are intended for articulation and the introduction of force with other parts and are formed by a laminated structure with intercalation of plies between primary plies extending the body of the reinforcement. This solution can nevertheless have drawbacks. Indeed, yokes which have a laminated configuration can lead to an increase in the size of the force introduction zones compared to the metal parts in order to avoid the risk of delamination.The mass gain of the overall system then becomes less interesting and the integration of the part more restrictive due to increased bulk. Another problem is that the proposed manufacturing technique involves significant manual intervention which can lead to non-conformities and an increase in cost. Finally, the mechanical performance of the composite material proposed in this document can be improved, particularly in terms of compressive strength over a middle zone of the length of the part called the current zone. One option to address this is to add material in the current zone which then penalizes the mass and therefore does not provide complete satisfaction.

[0003] The invention proposes to address all or part of the aforementioned drawbacks. Statement of the invention

[0004] The invention relates to a fibrous preform of a core portion of a fibrous reinforcement for a composite material part, the preform having a slender shape along a longitudinal direction and being formed by first threads extending along the longitudinal direction with second threads transverse to the first threads, the preform comprising two longitudinal ends intended for articulation with other parts and a median zone located between the longitudinal ends, each longitudinal end having a thickness greater than a thickness of the middle zone, the middle zone comprising a stiffening portion comprising first nonwoven yarns and each longitudinal end comprising a three-dimensional weave of the first yarns of this stiffening portion with second yarns.

[0005] The invention proposes an optimized design of a core preform of a fiber reinforcement of the core-belt assembly type which is based on the three-dimensional weaving technique and on articulation zones with excess thickness compared to the middle zone, or current zone, in order to obtain improved resistance to stress introduction zones. The stiffening portion makes it possible to significantly improve the compression performance of the middle zone compared to a structure entirely obtained by three-dimensional weaving. The invention also limits, or even avoids, weaving with second threads in the middle zone, which reduces material consumption as well as subsequent treatments after the textile operation such as cutting. The first threads of the stiffening portion are woven by three-dimensional weaving on the longitudinal ends so as to obtain the desired resistance to stresses in the articulation zones.

[0006] In an exemplary embodiment, the fiber preform comprises woven skins located on either side of the stiffening portion with the first threads of this stiffening portion being held by threads originating from said woven skins.

[0007] Such a characteristic advantageously makes it possible to improve the impact resistance of the fiber reinforcement.

[0008] In particular, the woven skins may comprise folded-over, untied lateral fibrous portions forming, on upper and lower sides of the preform, a positioning surface for a belt fibrous texture.

[0009] Such a characteristic helps to improve the quality of the interface between the core and the belt and to further improve the mechanical performance of the part.

[0010] In an exemplary embodiment, the preform further comprises, between each longitudinal end and the middle zone, a transition zone comprising additional layers of first yarns compared to those present in the middle zone which are woven with second yarns in the longitudinal ends.

[0011] Such a characteristic advantageously makes it possible to achieve a greater increase in thickness in the longitudinal ends and therefore to further improve the mechanical properties of the part.

[0012] In an exemplary embodiment, the preform is made of carbon wires.

[0013] The invention also relates to a method for manufacturing a fibrous reinforcement of a part made of composite material, comprising: - positioning a woven fibrous belt texture on a preform of a core portion as described above, the belt texture defining a loop around the preform of the core part so as to define, at the longitudinal ends, free spaces intended for articulation with other parts.

[0014] In an exemplary embodiment, the belt texture is made of carbon threads.

[0015] The invention also relates to a method of manufacturing a composite part intended to be articulated with other parts, comprising: - the formation of a fibrous reinforcement as described above, and - the formation of a matrix in a porosity of the fibrous reinforcement thus obtained.

[0016] In an exemplary embodiment, the matrix is ​​an organic matrix.

[0017] In an exemplary embodiment, the part is a landing gear strut, part of a landing gear strut or brake bar. Brief description of the drawings

[0018] [Fig-1] [Fig.l] schematically represents an example of fibrous texture intended to form a preform according to the invention.

[0019] [Fig.2] [Fig.2] schematically represents a cross-section of the texture of [Fig.l].

[0020] [Fig.3A] [Fig.3A] represents, schematically and partially, a first stage of a possible shaping for the texture of figures 1 and 2.

[0021] [Fig.3B] [Fig.3B] represents, schematically and partially, a second stage of a possible shaping for the texture of figures 1 and 2.

[0022] [Fig.3C] [Fig.3C] represents, schematically and partially, a third stage of a possible shaping for the texture of figures 1 and 2 as well as the positioning of the belt.

[0023] [Fig.4] [Fig.4] is a perspective view of an example of a core-belt assembly type fiber reinforcement according to the invention. Description of the embodiments

[0024] [Fig. 1] represents a woven fibrous texture 100 which is intended to form, after shaping, a fibrous preform 200 (see FIGS. 3B, 3C and 4) of a core of a fibrous reinforcement for a composite material part. A possible shaping for the texture will be described below in connection with FIGS. 3A to 3C. The texture 100 and the preform 200 have a slender shape extending along a longitudinal direction X and can be obtained by weaving in a single piece. The texture 100 and the preform 200 successively comprise along the direction X a first longitudinal end 103a, a middle zone ZM and a second longitudinal end 103b. In the illustrated example, there is also the presence of a first transition zone ZTa between the first end 103a and the middle zone ZM and of a second transition zone ZTb between the middle zone ZM and the second end 103b.The presence of the transition zones ZTa and ZTb is considered in the illustrated example but . remains optional within the scope of the invention. According to one example, each transition zone ZTa, ZTb possibly present may have a length La, Lb comprised between 1% and 20% of the length LO of the texture 100 or the preform 200, and each end 103a, 103b may have a length L2, L3 comprised between 1% and 20% of the length LO. The lengths are measured along the X direction. The median zone ZM may be centered relative to a plane P50 located at mid-length of the texture 100 or the preform 200 and perpendicular to the X direction. In the example illustrated in [Fig.l], the thickness e2 of the first end 103a is greater than the thickness el of the median zone ZM. The thickness e3 of the second end 103b is less than the thickness e2 but greater than the thickness el. Thicknesses are measured along the thickness direction (E direction) and correspond to the smallest dimension.According to one example, the ratio e2 / el may be greater than 1 and less than or equal to 4, for example between 1.5 and 2.5, and the ratio e3 / el may be greater than 1 and less than or equal to 4, for example between 1.5 and 2.5.

[0025] The textile architecture differs between the ends 103a, 103b, the transition zones ZTa, ZTb and the middle zone ZM as will be detailed below. The ends 103a, 103b are obtained by three-dimensional weaving of first yarns which extend along the direction X with second yarns transverse to the first yarns, for example with an “interlock” weave. In the example illustrated, a portion of the first yarns present in the ends 103a, 103b form, in the middle zone ZM, a stiffening portion 102c and are not woven with second yarns in this portion 102c. The first yarns may extend, in the stiffening portion 102c, in a substantially rectilinear manner. The stiffening portion 102c may comprise unidirectional layers of first yarns.Generally speaking, the first nonwoven yarns may be in the majority in number (more than 50%) in the middle zone ZM, for example representing at least 80% in number of all the yarns present in the middle zone ZM. Second yarns are added in the longitudinal ends 103a, 103b so as to weave the first yarns of the stiffening portion 102c. These second added yarns correspond to layers of yarns additional to the layers of second yarns possibly present in the middle zone ZM. [Fig.2] illustrates a view, in cross section, relative to the direction X, of a possible textile configuration at the level of the middle zone ZM.The texture 100 comprises a central portion 110 having, on its opposite sides 111, two positioning edges 120 which each comprise unbound lateral portions 160a, 160b separated by a unbounding zone 140 allowing a spacing of these portions 160a, 160b relative to each other. The positioning edges 120 and the central portion 110 are offset along the width direction L, and the unbound portions 160a, 160b. are offset along the thickness direction E. The central portion 110 comprises the stiffening portion 102c comprising the first non-woven C5-C12 yarns. Woven skins 102a, 102b, for example obtained by three-dimensional weaving, for example by “interlock” weaving, are present in the central portion 110 and extend beyond it so as to form the untied portions 160a, 160b. The skins 102a, 102b are formed by a weave between first yarns C1-C4 and C13-C16 extending along the longitudinal direction X with second yarns t1-t8 extending along the direction L. Generally, it will be recognized that the number of yarn layers as well as the weave pattern illustrated are provided only as an example and may be modified without departing from the scope of the invention.The skins 102a, 102b are located in the middle zone ZM and their extension defines in the ends 103a, 103b a single piece of fabric extending over the entire width and thickness of the texture 100 or of the preform 200. The threads C5-C12 of the stiffening portion 102c are located between the skins 102a, 102b and held together by threads originating from them. Indeed, it can be seen that the wire t4 extends in the first skin 102a outside the central portion 110 and is deflected in order to exit this first skin 102a to bind the set 102c of wires C5-C12 in the central portion 110. Similarly, the wire t5 extends in the second skin 102b outside the central portion 110 and is deflected in order to exit this second skin 102b to bind the set 102c of wires C5-C12 in the central portion 110 on the side opposite the wire t4.This results in encapsulation of the stiffening portion 102c formed by the threads C5-C12 between the skins 102a, 102b, these threads C5-C12 being held in place by the deflected threads t4-t5. In the example illustrated, there are in the central portion 110 successively along the thickness direction E: the first skin 102a, the portion 102c of non-woven threads and the second skin 102b. It will be noted that the portion 102c of non-woven threads is only present in the central portion 110 and not in the positioning edges 120. This allows a saving of thread in this area and avoids a manual cutting step if these threads were woven. As indicated above, the C5-C12 yarns are not woven over only part of the length of the first texture 100 or of the preform 200, over its middle zone ZM and possibly over the transition zones ZTa, ZTb, and are woven into the longitudinal ends 103a, 103b.The length where the C5-C12 yarns are non-woven may be greater than or equal to 50%, for example 75%, of the length LO of the texture 100 or of the preform 200.

[0026] Figures 3A to 3C illustrate, in a simplified manner, the shaping of the texture. 100 of figures 1 and 2 in order to obtain the preform 200 as well as the positioning of the second belt texture 40, it being understood that the configuration is symmetrical with respect to the directions L and E. In the example considered, there is deployment of the untied portions 160a, 160b on a form (not illustrated) so as to form an angle substantially 90° with the direction L and to position the loose portions 160a, 160b at the height of the portion 102c. This height is taken along the direction L. A preform 200 is thus obtained having a positioning surface 130 of substantially planar shape with, at the same level, the loose portions 160a, 160b as well as the portion 102c which is located between these loose portions and thus defines a bearing surface for the belt texture 40. The preform 200 may have an I-shape (called a double angle iron shape) in cross-section relative to the longitudinal direction X. In the example of [Fig.l], there is a transition zone ZTa, ZTb between the median zone ZM and the ends 103a, 103b. The stiffening portion 102c is also present in the transition zones ZTa, ZTb but the skins 104al, 104a2, 104bl and 104b2 are thickened compared to the skins 102a, 102b of the middle zone ZM.Indeed, there is an addition in this zone of layers of first threads additional to those present in the middle zone ZM. The layers of first threads added in this zone can, as illustrated, be woven progressively with second threads so as to form the skins 104al, 104a2, 104bl and 104b2 and extend into the ends 103a, 103b in order to obtain the desired thickness for these when a significant excess thickness is sought.

[0027] [Fig.4] represents an example of a core-belt assembly according to the invention. forming the fibrous reinforcement 300 of the part to be obtained. The woven belt texture 40 was positioned around the preform 200 obtained after shaping the texture 100 by folding down the loosened portions 160a, 160b. The texture 40 may have the shape of a strip which is wrapped around the preform 1. During its positioning, the texture 40 comes to bear on the positioning surface 130. The texture 40 may be in the form of a single strip of fabric but it is not outside the scope of the invention if it is in the form of several strips placed end to end or side by side. The texture 40 may also be obtained by three-dimensional weaving, for example with an “interlock” weave. The texture 40 defines a closed loop around the preform 200 and defines free spaces 42 intended for articulation with the other parts.Inserts (not shown) can be temporarily used at the longitudinal ends 103a, 103b and the second texture 40 can be wrapped around them so as to ensure the desired shape for the end regions. The ends 103a, 103b can, as illustrated, have a curved shape, for example substantially circular. The transverse dimension DT of the positioning surface 130 increases from the first end 103a to the median zone ZM, maximum in the vicinity of the mid-length plane P50 of the preform 200, for example at least on the section located between the planes P40 and P60 located at 40% and 60% of the length LO and perpendicular to the direction X, then decreasing towards the second end 103b. The positioning surface 130 defines fins. lateral for positioning the belt texture 40. The volume ratios between the warp and weft threads of each of the preform 200 and the belt texture 40 may be similar, for example with a difference of at most 10%. These volume ratios correspond to the ratio: [volume occupied by the warp threads] / [volume occupied by the weft threads] for each textile considered.

[0028] A densification of the entire preform 200 and texture 40 is then carried out, for example by introducing a resin, such as an epoxy resin, followed by crosslinking thereof if it is a thermosetting resin or by cooling if it is a thermoplastic resin. The formation of the matrix can be carried out by resin transfer molding technique which corresponds to a technique known per se. A part is thus obtained made of composite material intended to be articulated with other parts at its longitudinal ends and to undergo tensile and compressive forces. The fibrous reinforcement of the part can be formed of carbon threads and the part can have an organic matrix as just described. The part may or may not be intended for an aeronautical application.The part may for example be a connecting rod, a landing gear strut or a constituent element thereof, or even a brake bar. The part obtained may be mounted to other parts by positioning through the free spaces 42 a hinge pin for connection to other parts as well as a contact insert with this. axis.

Claims

Claims

1. A method of manufacturing a fibrous reinforcement (300) of a composite material part, comprising: - positioning a woven belt fibrous texture (40) on a fibrous preform (200) of a core portion of a fibrous reinforcement (300) for a composite material part, the preform having a slender shape along a longitudinal direction (X) and being formed by first threads (Cl-Cl6) extending along the longitudinal direction with second threads (tl-t8) transverse to the first threads, the preform comprising two longitudinal ends (103a; 103b) intended for articulation with other parts and a middle zone (ZM) located between the longitudinal ends, each longitudinal end having a thickness (e2;e3) greater than a thickness (el) of the middle zone, the middle zone comprising a stiffening portion (102c) comprising first non-woven yarns (C5-C12) and each longitudinal end comprising a three-dimensional weaving of the first yarns of this stiffening portion with second yarns, the belt texture defining a loop around the preform of the core part so as to define, at the longitudinal ends, free spaces (42) intended for articulation with other parts.;

2. Method according to claim 1, in which the fibrous preform comprises woven skins (102a; 102b) located on either side of the stiffening portion (102c) with the first threads (C5-C12) of this stiffening portion being held by threads (t4; t5) coming from said woven skins.

3. A method according to claim 2, wherein the woven skins (102a; 102b) comprise folded-over, untied lateral fibrous portions (160a; 160b) forming, on upper and lower sides (111) of the preform, a positioning surface (130) for a belt fibrous texture (40).

4. A method according to any one of claims 1 to 3, wherein the preform further comprises, between each longitudinal end (103a; 103b) and the middle zone (ZM), a transition zone (ZTa; ZTb) comprising additional layers of first yarns compared to those present in the middle zone which are woven with second yarns in the longitudinal ends.

5. A method according to any one of claims 1 to 4, wherein the preform is made of carbon fibers.

6. A method according to any one of claims 1 to 5, wherein the belt texture (40) is made of carbon yarns.

7. Method for manufacturing a composite part intended to be articulated with other parts, comprising: - the formation of a fibrous reinforcement (300) according to any one of claims 1 to 6, and - the formation of a matrix in a porosity of the fibrous reinforcement thus obtained.

8. The method of claim 7, wherein the matrix is ​​an organic matrix.

9. A method according to claim 7 or 8, wherein the part is a landing gear strut, a portion of a landing gear strut or a brake bar.