Fibrous Reinforcement for the Manufacture of Composite Parts Intended to be Articulated with Other Parts

Abstract

The present invention relates to a fibrous preform of a core portion of a fibrous reinforcing material of a composite material part, which has an elongated shape along the longitudinal direction X and is formed by first yarns C1 to C16 extending along the longitudinal direction and second yarns t1 to t8 crossing the first yarns. In the fibrous preform, the preform includes two longitudinal ends intended for articulation joining with other parts and an intermediate region located between the longitudinal ends. Each longitudinal end has a thickness greater than the thickness of the intermediate region. The intermediate region includes first non-woven yarns C5 to C12. Each longitudinal end includes a reinforcing segment 102c including a three-dimensional weave of a first non-woven yarn and a second yarn of the reinforcing segment.

Description

Technical Field

[0001] The present invention relates to a fibrous preform intended to form part of the fibrous reinforcement of a component made of a composite material, the component being intended to be articulated with another component at its end, and to a related manufacturing method.

Background Art

[0002] The use of composite materials instead of metallic materials can be proposed in view of the weight reduction that is always a concern, especially in the case of aircraft components. From this perspective, Patent Document 1 (U.S. Patent Application Publication No. 7704429) proposes the manufacture of a landing gear strut made of a composite material having a region called a fork, this fork being intended for articulation with and force introduction to other components and being formed by a laminated structure involving the insertion of a layer between primary layers extending the body of the reinforcement. Nevertheless, this solution can have drawbacks. In fact, a fork having a laminated configuration can lead to an increase in the size of the force introduction region compared to metallic components in order to avoid the risk of delamination. In this case, the weight reduction of the whole system becomes less interesting and the integration of the component becomes more restrictive due to the increase in bulk density. Another problem is that the proposed manufacturing technology involves a significant amount of manual intervention that can lead to incompatibilities and increased costs. Finally, the mechanical performance of the composite materials proposed herein can be improved, especially with respect to the compressive strength over the intermediate region of the length of the component, called the common region. One option to address this is to add material to the common region, which is disadvantageous from the mass perspective and thus does not provide complete satisfaction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention proposes to address all or part of the aforementioned drawbacks.

Means for Solving the Problems

[0005] The present invention relates to a fibrous preform of the core part of a fibrous reinforcement for a composite material part, the fibrous preform having an elongated shape along the longitudinal direction and being formed by a first thread extending along the longitudinal direction and a second thread crossing the first thread. The preform comprises two longitudinal ends intended for articulation with other parts and an intermediate region located between these two longitudinal ends. Each longitudinal end has a thickness greater than the thickness of the intermediate region. The intermediate region comprises a reinforcing segment comprising a first non-woven thread. Each longitudinal end comprises a three-dimensional weave of the first and second threads of this reinforcing segment.

[0006] The present invention proposes an optimized design of a core preform of a core belt assembly type of fibrous reinforcement based on three-dimensional weaving technology and on articulation regions of excessive thickness compared to the intermediate region, i.e., the common region, in order to obtain improved resistance to force introduction into the region. This reinforcing segment makes it possible to significantly improve the compression performance of the intermediate region compared to the structure obtained entirely by three-dimensional weaving. Also, according to the present invention, the weaving by the second thread in the intermediate region is restricted or even avoided, thereby reducing material consumption and post-weaving processing such as cutting. The first thread of the reinforcing segment is woven in a three-dimensional weave at the longitudinal ends so as to obtain the desired resistance to forces in the articulation region.

[0007] In an exemplary embodiment, the fibrous preform comprises a fabric skin located on both sides of the reinforcing segment, and the first thread of this reinforcing segment is held by a thread coming from the fabric skin.

[0008] Due to such characteristics, advantageously, the impact resistance of the fibrous reinforcement can be improved.

[0009] In particular, the fabric skin may comprise folded, unconnected transverse fibrous segments that form positioning surfaces for the fiber belt texture at the upper and lower sides of the preform.

[0010] Such characteristics help to improve the quality of the interface between the core and the belt and further improve the mechanical performance of the part.

[0011] In an exemplary embodiment, the preform further comprises a transition region having an additional layer of the first yarn between each longitudinal end and the intermediate region, compared to that present in the intermediate region woven with the second yarn at the two longitudinal ends.

[0012] Due to such characteristics, advantageously, it is possible to achieve a greater increase in the thickness of the longitudinal ends, and thus it is possible to further improve the mechanical properties of the part.

[0013] In an exemplary embodiment, the preform is made of carbon yarn.

[0014] The present invention also relates to a method for manufacturing a fibrous reinforcement of a composite part, Positioning a woven fiber belt texture on a preform of a core part as described above, the belt texture defining a loop around the preform of the core part so as to define a free space intended for articulation with other parts at the longitudinal ends.

[0015] In one exemplary embodiment, the belt texture is made of carbon yarn.

[0016] The present invention also relates to a method for manufacturing a composite part intended to be articulated with other parts, Forming a fibrous reinforcement as described above, A method comprising forming a matrix at the porosity of the fibrous reinforcement thus obtained.

[0017] In an exemplary embodiment, the matrix is an organic matrix.

[0018] In an exemplary embodiment, the component is a landing gear strut, a part of a landing gear strut, or a brake bar.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Figure 4

Modes for Carrying Out the Invention

[0020] Figure 1 shows a woven fiber texture 100 that is intended to form a fibrous preform 200 (see FIGS. 3B, 3C, and 4) of a core of fibrous reinforcement for a composite material part after shaping. The possible shapes of the texture are described below in connection with FIGS. 3A-3C. The texture 100 and the preform 200 have an extended shape extending along the longitudinal direction X and can be obtained by weaving into a single part. The texture 100 and the preform 200 continuously comprise a first longitudinal end 103a, an intermediate region ZM, and a second longitudinal end 103b along the longitudinal direction X. In the illustrated example, there is a first transition region ZTa between the first end 103a and the intermediate region ZM, and a second transition region ZTb between the intermediate region ZM and the second end 103b. The presence of the transition regions ZTa and ZTb is considered in the illustrated embodiment but is optional within the framework of the present invention. According to one example, each possible transition region ZTa, ZTb can have lengths La, Lb that constitute 1% to 20% of the length LO of the texture 100 or the preform 200, and each end 103a; 103b can have lengths L2, L3 that constitute 1% to 20% of the length LO. The lengths are measured along the longitudinal direction X. The intermediate region ZM is located at the intermediate length of the texture 100 or the preform 200 and can be centered with respect to a plane P50 perpendicular to the longitudinal direction X. In the example shown in FIG. 1, the thickness e2 of the first end 103a is greater than the thickness e1 of the intermediate region ZM. The thickness e3 of the second end 103b is smaller than the thickness e2 but greater than the thickness e1. The thickness is measured along the thickness direction (E direction) and corresponds to the minimum dimension. In one example, the ratio e2 / e1 can be greater than 1 and less than or equal to 4, for example, 1.5 to 2.5, and the ratio e3 / e1 can be greater than 1 and less than or equal to 4, for example, 1.5 to 2.5.

[0021] The fabric architecture is different in the end portions 103a; 103b, the transition regions ZTa, ZTb, and the intermediate region ZM, as detailed below. The end portions 103a; 103b are obtained by three-dimensionally weaving a first thread extending along the longitudinal direction X together with a second thread crossing the first thread, for example, in a "lockstitch" weaving pattern. In the illustrated example, a part of the first thread present in the end portions 103a; 103b forms a reinforcing segment 102c in the intermediate region ZM, and this segment 102c is not woven with the second thread. The first thread can extend substantially linearly within the reinforcing segment 102c. The reinforcing segment 102c can comprise a unidirectional layer of the first thread. Generally, the first non-woven thread can be the majority (more than 50%) of the number within the intermediate region ZM, for example, can represent at least 80% of the total number of all threads present within the intermediate region ZM. The second thread is applied to the longitudinal end portions 103a; 103b so as to weave the first thread of the reinforcing segment 102c. These additional second threads probably correspond to an additional layer of threads as compared to the layer of the second thread present in the intermediate region ZM. FIG. 2 shows a cross-sectional view of a possible fabric configuration in the intermediate region ZM with respect to the longitudinal direction X. The texture 100 comprises a central segment 110 having two positioning edges 120 each provided with unconnected transverse segments 160a, 160b separated by unconnected regions 140 on both sides 111 thereof allowing the spacing of these segments 160a, 160b with respect to each other. The positioning edges 120 and the central segment 110 are offset along the width direction L, and the unconnected segments 160a, 160b are offset along the thickness direction E. The central segment 110 comprises a reinforcing segment 102c comprising the first non-woven threads C5 to C12. Fabric skins 102a, 102b obtained by three-dimensionally weaving, for example, by "lockstitch" weaving, are present within and extend beyond the central segment 110 to form the unconnected segments 160a, 160b. The skins 102a, 102b are formed by weaving between the second threads t1 to t8 extending along the direction L and the first threads C1 to C4 and C13 to C16 extending along the longitudinal direction X.Generally, it will be recognized that the number of layers of yarns shown and the weaving pattern are provided by way of example only and can be varied without departing from the scope of the present invention. The skins 102a, 102b are disposed in the intermediate region ZM, and their extent defines a single piece of fabric that extends across the width and thickness of the texture 100 or preform 200 at the ends 103a; 103b. The yarns C5 - C12 of the reinforcing segment 102c are disposed between the skins 102a, 102b and are held together by the yarns coming therefrom. In fact, note that the yarn t4 extends into the first skin 102a outside the central segment 110, exits this first skin 102a, and is deflected to join the set 102c of yarns C5 - C12 within the central segment 110. Similarly, the yarn t5 extends into the second skin 102b outside the central segment 110, exits this second skin 102b, and is deflected to join the set 102c of yarns C5 - C12 within the central segment 110 on the side opposite to the yarn t4. Thus, the encapsulation of the reinforcing segment 102c formed by the yarns C5 - C12 is obtained between the skins 102a, 102b, and these yarns C5 - C12 are held in place by the deflected yarns t4 - t5. In the example shown, in the central segment 110, along the thickness direction E, the first skin 102a, the segment 102c of non-woven yarns, and the second skin 102b are continuously present. Note that the segment 102c of non-woven yarns is present only in the central segment 110 and not in the positioning edge 120. This allows for a saving of yarns in this region and avoids the manual cutting step when these yarns are woven. As described above, the yarns C5 - C12 are not woven across the entire length of the first texture 100 or preform 200, but only across its intermediate region ZM and possibly across the transition regions ZTa, ZTb, and are woven at the longitudinal ends 103a; 103b. When the yarns C5 - C12 are non-woven, their length can be 50% or more, for example 75%, of the length LO of the texture 100 or preform 200.

[0022] Figures 3A - 3C schematically show the shaping of the texture 100 of FIGS. 1 and 2 and the positioning of the second belt texture 40 to obtain the preform 200. It should be understood that this configuration is symmetric with respect to the directions L and E. In the example considered, on the shape (not shown), the unconnected segments 160a, 160b are deployed to form an angle of substantially 90° with respect to the direction L and are positioned at the height of the segment 102c. This height is obtained along the direction L. The preform 200 has a substantially planar positioning surface 130 and, at the same level, has the unconnected segments 160a, 160b and the segment 102c that is located between these unconnected segments and thus defines the contact surface of the belt texture 40. The preform 200 can have an I - shaped (referred to as a double - angle shape) cross - section with respect to the longitudinal direction X. In the example of FIG. 1, there are transition regions ZTa, ZTb between the intermediate region ZM and the ends 103a; 103b. The reinforcing segment 102c is also present in the transition regions ZTa, ZTb, but the skins 104a1, 104a2, 104b1 and 104b2 are thicker than the skins 102a, 102b of the intermediate region ZM. In fact, there is an addition of a further layer of the first yarn in this region compared to what is present in the intermediate region ZM. The layer of the first yarn added to this region is gradually woven with the second yarn as shown to form the skins 104a1, 104a2, 104b1, and 104b2, extends into the ends 103a; 103b, and can obtain the desired thickness for the ends when a significant excess thickness is required.

[0023] Figure 4 shows an example of a core belt assembly according to the present invention for forming the fibrous reinforcement 300 of the resulting part. The woven belt texture 40 is positioned around the preform 200 obtained after shaping the texture 100 by folding the unconnected segments 160a, 160b. The texture 40 can have the shape of a strip wound around the preform 1. When positioned, the texture 40 abuts against the positioning surface 130. The texture 40 can be in the form of a single strip of cloth, but it is not outside the scope of the present invention if it is in the form of several strips arranged end-to-end or side-by-side. The texture 40 can also be obtained, for example, by three-dimensional weaving using an "interlock" weaving pattern. The texture 40 defines a closed loop around the preform 200 and defines a free space 42 intended for articulation with other parts. Inserts (not shown) can be temporarily used at the longitudinal ends 103a; 103b, and a second texture 40 can be wound around them to ensure the desired shape for the end regions. The ends 103a; 103b can have a curved shape, for example, a substantially circular shape as shown. The transverse dimension DT of the positioning surface 130 increases from the first end 103a to the intermediate region ZM, for example, and is located between the planes P40 and P60 at least at positions of 40% and 60% of the length LO and is in a cross-section perpendicular to the longitudinal direction X. It is maximum near the plane P50 of the intermediate length of the preform 200 and then decreases towards the second end 103b. The positioning surface 130 defines transverse fins for positioning the belt texture 40. The volume ratio between the warp and weft of each of the preform 200 and the belt texture 40 can be made the same, for example, with a maximum difference of 10%. These volume ratios correspond to the ratio of [volume occupied by the warp] / [volume occupied by the weft] for each fabric considered.

[0024] Next, the densification of the entire preform 200 and the texture 40 is carried out, for example, by introducing a resin such as an epoxy resin and then, in the case of a thermosetting resin, crosslinking it or, in the case of a thermoplastic resin, cooling it. The form of the matrix can be carried out by a resin transfer molding technique corresponding to techniques known per se. The composite material part thus obtained is intended to be articulated with other parts at its longitudinal ends and to receive tensile and compressive forces. The fibrous reinforcement of the part can be formed of carbon filaments, and the part can have an organic matrix as described above. The part may or may not be for aviation applications. The part can be, for example, a connecting rod, a landing gear strut or its components, or a brake bar. The obtained part can be attached to other parts by positioning a hinge pin for connecting to other parts and a contact insert with this pin via a free space 42.

Claims

1. In a method for manufacturing a fibrous reinforcement (300) of a composite part, the method comprises positioning a woven fiber belt texture (40) on a fibrous preform (200) of a core portion of the fibrous reinforcement (300) for the composite part, the fibrous preform has an extended shape along a longitudinal direction (X), and is formed by a first thread (C1 to C16) extending along the longitudinal direction and a second thread (t1 to t8) crossing the first thread. The fibrous preform comprises two longitudinal ends (103a; 103b) intended for articulation with other parts and an intermediate region (ZM) located between the two longitudinal ends. Each longitudinal end has a thickness (e2; e3) greater than the thickness (e1) of the intermediate region. The intermediate region comprises a reinforcing segment (102c) comprising a first non-woven thread (C5 to C12). Each longitudinal end comprises a three-dimensional weave of the first non-woven thread (C5 to C12) of the reinforcing segment and the second thread. The woven fiber belt texture defines a loop around the fibrous preform of the core portion so as to define a free space (42) intended for articulation with other parts at the two longitudinal ends.

2. The method according to claim 1, wherein the fibrous preform comprises fabric skins (102a; 102b) located on both sides of the reinforcing segment (102c), and the first threads (C5 to C12) of the reinforcing segment are held by threads (t4; t5) coming from the fabric skins.

3. The method according to claim 2, wherein the fabric skins (102a; 102b) comprise folded, unconnected transverse fibrous segments (160a; 160b), and form positioning surfaces (130) for the fiber belt texture (40) on the upper and lower sides (111) of the fibrous preform.

4. The method according to any one of claims 1 to 3, wherein the fibrous preform further comprises transition regions (ZTa; ZTb) comprising additional layers of the first thread between each longitudinal end (103a; 103b) and the intermediate region (ZM), as compared to those present in the intermediate region woven with the second thread at the two longitudinal ends.

5. The method according to any one of claims 1 to 4, wherein the fibrous preform is made of carbon threads.

6. The method according to any one of claims 1 to 5, wherein the woven fiber belt texture (40) is made of carbon yarns. **Claim 7** In a method of manufacturing a composite part intended to be articulated with other parts, the method comprises: forming a fibrous reinforcement (300) according to any one of claims 1 to 6; and forming a matrix at the porosity of the fibrous reinforcement thus obtained. **Claim 8** The method according to claim 7, wherein the matrix is an organic matrix. **Claim 9** The method according to claim 7 or 8, wherein the part is a landing gear strut, a part of a landing gear strut, or a brake bar.

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