METHOD FOR PRODUCE A COMPOSITE MATERIAL PART INTENDED TO JOIN WITH OTHER PARTS

Description

Technical Field

[0001] The invention relates to a method for manufacturing a preform of a composite part intended to be articulated with other parts at its ends, and a method for manufacturing such a part. Previous technique

[0002] The use of composite materials as a replacement for metallic materials can be proposed for weight reduction purposes, a constant concern, particularly in the case of aircraft components. In this regard, US patent 7,704,429 proposed the manufacture of landing gear struts from composite materials. These struts include regions, called cleats, designed for articulation and load transfer with other components. These cleats are formed by a laminated structure with intercalated plies between primary plies extending from the body of the reinforcement. However, this solution may present drawbacks. Indeed, cleats with a laminated configuration may lead to an increase in the size of the load transfer areas compared to metallic components, in order to prevent the risk of delamination.The overall system mass reduction then becomes less advantageous, and the integration of the part becomes more challenging due to its increased size. Another issue is that the proposed manufacturing technique involves significant manual intervention, which can lead to non-conformities and increased costs. Finally, the mechanical performance of the composite material proposed in this document can be improved, particularly in terms of compressive strength in a mid-length area of ​​the part, known as the "current zone." One option to address this is to add material to the current zone, which increases the mass and therefore does not provide a fully satisfactory solution. US2007 / 007386A1 relates to a manufacturing process for a fibrous preform of a composite part.

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

[0004] The invention relates to a method for manufacturing a fibrous preform of a composite part intended to be articulated with other parts, comprising at least: the formation by weaving of a first slender-shaped fibrous core texture extending in a longitudinal direction and comprising, in cross-section, a central portion having, on its opposite sides, two positioning edges each comprising two unbound lateral fibrous portions, the shaping of the first fibrous texture comprising at least the unfolding of the unbound lateral portions to form a positioning surface defined by the lateral portions thus unfolded and by an intercalated fibrous portion, situated between these unfolded portions, formed by an extension of the central portion or by this central portion, and the positioning of a second woven fibrous belt texture on the unfolded lateral portions and the intercalated fibrous portion, the second texture defining a loop around the first shaped texture so as to define,At the longitudinal ends, between the first and second textures, are free spaces intended for articulation with other pieces.

[0005] The invention proposes a solution based on an assembly between a core and a belt, each resulting from a weaving operation, with a positioning surface for the belt formed by the interlayer portion and the unfolded, loosely woven portions located on either side of it. Such a solution provides a high-quality interface for the assembly, ensuring good adhesion of the composite part, and notably improves mechanical performance compared to US 7,704,429, particularly in terms of compressive strength, without increasing the mass of the structure. In particular, the positioning surface can advantageously be substantially flat due to the presence of the interlayer portion, thus eliminating the need for a third-party filler material between the unfolded portions.The streamlined sections, after shaping, increase rigidity along all stress axes of the part (optimizing inertia). The belted technology according to the invention also offers lower manufacturing costs than the discussed prior art solution.

[0006] In one example, each positioning edge further includes an intercalary fibrous texture extending from the central portion and situated between the unbound lateral fibrous portions, and the shaping process further includes cutting this intercalary fibrous texture to form the intercalary fibrous portion. In this example, the intercalary portion is formed by a residual textile extension of the central portion within the positioning edges resulting from cutting the intercalary fibrous texture.

[0007] According to one variant, the central portion comprises woven skins and a set of non-woven yarns situated between the woven skins and held together by yarns from them, the woven skins extending beyond the central portion into the positioning edges to form the unbound lateral fibrous portions, and in which these unbound portions are deployed so as to fold them down to the height of the set of non-woven yarns during shaping.

[0008] In this variant, the intermediate portion is formed by the central portion itself, located at the same level as the deployed unbound portions, thus eliminating the need for the cutting operation described above. Furthermore, the set of non-woven yarns forms a stiffening portion that further improves compressive strength compared to a structure entirely obtained through three-dimensional weaving.

[0009] In one exemplary embodiment, the loose lateral fibrous portions are formed by weaving first and second yarns and have a first volume ratio of first yarns relative to second yarns, and the second texture is formed by weaving first and second yarns and has a second volume ratio of first yarns relative to second yarns, the relative difference between the first and second volume ratios not exceeding 25%, for example not exceeding 10%.

[0010] Such a characteristic helps to further improve the mechanical strength of the composite material part to be obtained.

[0011] In one example of the design, the first and second textures are made of carbon fibers.

[0012] The invention also relates to a method for manufacturing a part made of composite material intended to be articulated with other parts, comprising at least: the formation of a fibrous preform of the part to be obtained by implementing a process as described above, and the formation of a matrix in a porosity of the fibrous preform thus obtained.

[0013] In one example of implementation, the matrix is ​​organic.

[0014] In one embodiment example, the part is a landing gear strut, part of a landing gear strut, or a brake bar. Brief description of the drawings

[0015] [ Fig. 1 ] There figure 1 represents, schematically, an example of a first fibrous core texture usable within the framework of the invention. Fig. 2 ] There figure 2 represents, schematically, a cross-section of the first texture according to the figure 1 . [ Fig. 3A ] There figure 3A represents a first step in an example of formatting the first texture according to the invention. Fig. 3B ] There figure 3B represents a second step in the example of formatting the first texture according to the invention. Fig. 3C ] There figure 3C represents a third step in the example of formatting the first texture according to the invention. Fig. 3D ] There figure 3D represents a fourth step in the example of formatting the first texture according to the invention. Fig. 4 ] There figure 4 This schematically represents an example of a preform for a composite material part obtained after positioning the second belt texture on the first shaped texture. Fig. 5 ] There figure 5 represents, schematically, a cross-section of a variant of the first texture usable within the scope of the invention. Fig. 6A ] There figure 6A represents a first step towards a possible shaping of the texture of the figure 5 . [ Fig. 6B ] There figure 6B represents a second step in this formatting process. Fig. 6C ] There figure 6C represents a third step in this shaping process with the positioning of the belt on this shaped texture. Description of the implementation methods

[0016] There figure 1 This illustrates an example of a first fibrous texture 1 usable within the scope of the invention. The first texture 1 has a slender shape extending along a longitudinal direction X. It can be obtained by three-dimensional weaving in a single piece, incorporating unbonding zones, as will be described later. "Three-dimensional weaving" or "3D weaving" refers to a weaving method in which at least some of the first yarns oriented along the X direction interlock second yarns transverse to the first yarns over several layers of second yarns. Such a weave can be produced on a Jacquard-type loom, in a manner known per se. The first texture 1 is intended to form the core of the fibrous reinforcement of the piece to be obtained. An interlock weave can, for example, be used to form the first texture 1.The first texture 1 has longitudinal ends 3 which have a curved shape, for example substantially circular, and which are intended to define, in the part to be obtained, free spaces dedicated to articulation with other parts. In the illustrated example, the longitudinal ends 3 are substantially the same size, but those skilled in the art will recognize that other variations are possible and in particular that the invention can be applied to a part having longitudinal ends of different dimensions.

[0017] The first texture 1 can be in the form of a strip and the figure 2 represents a cross-section of the first texture taken transversely to the longitudinal direction X. The first texture 1 comprises a central portion 10 which has, on its opposite sides 11, two edges 12 intended for positioning a second texture, called positioning edges 12. The central portion 10 and the edges 12 each extend along the longitudinal direction X. The central portion 10 is located between the edges 12. In the illustrated example, the edges 12 and the central portion 10 are offset along the width of the first texture (direction L). Each positioning edge 12 successively presents, in the illustrated example along the thickness of the first texture 1 (direction E), which corresponds to its smallest dimension, a first lateral unbound fibrous portion 16a, an intercalated fibrous texture 18, and a second lateral unbound fibrous portion 16b.A first unbinding zone 14a is present between the first portion 16a and the texture 18, and a second unbinding zone 14b is present between the texture 18 and the second portion 16b. In the unbinding zones 14a and 14b, layers of yarn from texture 18 and portion 16a and 16b have been intentionally omitted from weaving together so that the latter can be deployed as will be described later. The unbinding zones 14a, 14b are initiated from the sides 11. Each of the portions 16a, 16b extends the central portion 10 beyond the sides 11. In the illustrated example, the portions 16a, 16b as well as the intercalated texture 18 are obtained by three-dimensional weaving like the central portion 10 but we do not depart from the scope of the invention when it is otherwise, in particular the intercalated texture can be formed of layers of non-woven yarns (layers of unidirectional yarns).It should be noted that the unbonding zones 14a, 14b can extend over all or part of the length of the first texture 1, in particular over a length LD of at least 50% thereof. The unbonding zones 14a, 14b can, in particular, be present in the median zone ZM of the length of the first texture 1. The example considered concerns the case where the height of the unbonding zones 14a, 14b measured along the direction L does not change along the longitudinal direction X, but this does not depart from the scope of the invention when it does, particularly in the specific case where the longitudinal ends 3 have different dimensions.In particular, the height of the 14a and 14b connections can vary to reach a maximum in the mid-zone ZM, further improving the quality of the interface with the belt and thus the mechanical properties of the current zone, notably the inertia of the web, thereby increasing buckling resistance under compressive or vibrational loading. We have just described a possible structure of the first texture 1; the following section will detail it in relation to the... figures 3A à 3D , a possible format for this in order to prepare the positioning of the second belt texture.

[0018] The first texture 1 is positioned in a first tooling 20 which comprises two parts 22 intended to rest on the first texture 1, as illustrated in the figure 3A More precisely, the central portion 10 is held between the parts 22, which can optionally apply compaction pressure to it if it is desired to adjust the fiber content. The two parts 22 can be offset along direction E as illustrated. The parts 22 have a face 22a, which can be substantially flat, bearing against the central portion 10, and a curved face 22b extending from face 22a in the opposite direction to the first texture 1. Face 22b defines, in particular, near the positioning edges 12, a zone 24 onto which the loose portions 16a, 16b are intended to be draped during the cutting of the interlayer texture 18. Thus, as illustrated in the figure 3B The loose portions 16a, 16b are separated from each other so as to position them on the area 24 of a respective part 22 and thus detach them from the interlayer texture 18. The loose portions 16a, 16b folded onto the area 24 are held to this area 24 by means known per se, for example by pinching. The interlayer texture 18 is then cut along a cutting line LD as shown in the figure 3C This cutting can be performed by waterjet cutting, but those skilled in the art will recognize that other techniques are possible. As illustrated, the cutting of the interlayer texture 18 can be carried out flush with the unbound portions 16a, 16b held on the parts 22. Furthermore, the curved shape of face 22b ensures that the unbound portions 16a, 16b extend away from the cutting line LD, thus avoiding any risk of damage during this operation. The cutting residue of texture 18 forms the interlayer portion 18a, which is located between the unbound portions 16a, 16b and will serve as a support for the belt texture. The portion 18a is located in the textile extension of the central portion 10. The textile portion 18a can have a sufficiently small length to exhibit sufficient rigidity to allow it to maintain a straight shape along the direction L in the absence of any holding tooling.

[0019] Once this cut is made, the first texture is extracted from tooling 20 and positioned between two shapes 23 of a second, separate tooling 21, which is a shaping tool for the core of the part to be obtained. The shapes 23 can be offset along direction E as illustrated. The figure 3D This illustrates the shaping process where the unfolded portions 16a and 16b are deployed on the forms 23 to create lateral fins, and in which the first texture 13 thus shaped has an I-shaped cross-section (called a double angle shape). In the illustrated example, each deployed unfolded portion 16a, 16b forms an elbow with the central portion 10, at an angle of approximately 90° to the direction L. The first shaped texture 13 defines, on either side of the central portion 10, at the positioning edges 12, a positioning surface 30 onto which the second belt texture is intended to be deposited. The positioning surface 30 is defined by the deployed unfolded portions 16a, 16b, as well as by the intermediate portion 18a extending from the central portion 10, which compensates for any lack of material that would result from the deployment of the unfolded portions 16a, 16b.This provides a good interface with the belt and in particular a positioning surface 30 of substantially flat shape, as illustrated in the figure. figure 3D The example just described uses two different tools, one for cutting and the other for shaping the first texture, but the invention remains within its scope if the same tool is used for both operations. The process continues by positioning a second woven fibrous belt texture 40 around the first texture 13, which has been shaped by tool 21, as illustrated in the figure. figure 4 The second texture 40 can be in the form of a strip that is wrapped around the first shaped texture 13. During its positioning, the second texture 40 rests on the unfolded portions 16a, 16b, and also on the intermediate portion 18a, thus providing a good interface between the two textures. The second texture 40 can 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 second texture 40 can also be obtained by three-dimensional weaving, for example, with an interlock weave. The second texture 40 defines a closed loop around the first shaped texture 13 and defines free spaces 42 for articulation with the other parts.Inserts (not shown) can be used temporarily at the longitudinal ends 3, and the second texture 40 can be wrapped around them to ensure the desired shape for the end regions. As mentioned above, the volume ratios between the warp and weft yarns of each of the first 11 and second 40 textures can be similar. These volume ratios correspond to the ratio: [volume occupied by warp yarns] / [volume occupied by weft yarns] for each texture considered.

[0020] A counter-mold is then positioned around the assembly of the two textures 13 and 40 to define, using tooling 21, a cavity for introducing the matrix material. The assembly is then densified, for example, by introducing a resin, such as an epoxy resin, followed by cross-linking if it is a thermosetting resin, or cooling if it is a thermoplastic resin. The matrix can be formed using resin transfer molding, a well-established technique. This produces a composite part designed to be articulated with other parts at its longitudinal ends. The fibrous reinforcement of the part can be made of carbon fibers, and the part can have an organic matrix, as described above. The part may or may not be intended for aeronautical applications.The part could, for example, be a connecting rod, a landing gear strut or a component thereof, or even a brake rod. The part may be designed to primarily withstand tensile and compressive forces during operation. The resulting part can be mounted to other parts by positioning, through the free spaces 42, a pivot pin for connection to other parts, as well as a contact insert for this pin.

[0021] The example just described concerns the case of an intercalary portion 18a formed by a textile extension of the central portion 10. However, the invention also addresses the case where the central portion itself is located between the unfolded, loose portions so as to provide a support surface for the second belt texture. Such an example will now be discussed in connection with the figures 5 And 6A at 6C.

[0022] There figure 5 is a cross-sectional view of a first texture variant 100 which includes, along all or part of its length, a central portion 110 having, on its opposite sides 111, two positioning edges 120 which each include unbounded lateral portions 160a, 160b separated by an unbounding zone 140 allowing these portions 160a, 160b to be separated from each other. As in the previous example, the positioning edges 120 and the central portion 110 are offset along the width direction L and the unbounded portions 160a, 160b are offset along the thickness direction E. The first texture 100 comprises woven skins 102a, 102b, for example obtained by three-dimensional weaving, which form part of the central portion 110 and extend in the continuation of this portion so as to form the unbound portions 160a, 160b.The skins 102a and 102b are formed by weaving together 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 understood that the number of yarn layers and the weave pattern illustrated are provided only as examples and may be modified without departing from the scope of the invention. The central portion 110 also includes a set 102c of non-woven yarns C5-C12 located between the skins 102a and 102b and held together by yarns extending from them. Indeed, we observe 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 link the assembly 102c of wires C5-C12 in the central portion 110.Similarly, yarn t5 extends into the second skin 102b outside the central portion 110 and is deflected to exit this second skin 102b and bind the set 102c of C5-C12 yarns in the central portion 110 on the side opposite yarn t4. This results in the encapsulation of the set 102c of nonwoven C5-C12 yarns between skins 102a and 102b, these C5-C12 yarns being held in place by the deflected yarns t4-t5. In the illustrated example, the central portion 110 contains, successively along the thickness direction E: the first skin 102a, the set 102c of nonwoven yarns, and the second skin 102b. It should be noted that the 102c set of non-woven yarns is present only in the central portion 110 and not in the positioning edges 120.It can also be noted that C5-C12 yarns may be non-woven over only part of the length of the first texture 100, for example in its mid-zone ZM, but may be woven over the longitudinal ends of the first texture 100. The length where the C5-C12 yarns are non-woven may be greater than or equal to 50% of the length of the first texture 100. figures 6A à 6C illustrate, in a simplified way, the formatting of the first texture of the figure 5as well as the positioning of the second belt texture 40, it being understood that the configuration is symmetrical with respect to the L and E directions. In the example considered, the loose portions 160a, 160b are deployed on a shape (not illustrated) so as to form an angle of approximately 90° with the L direction and to position the loose portions 160a, 160b at the height of the set 102c of non-woven yarns. This height is taken along the L direction. A positioning surface 130 of substantially flat shape is thus obtained, with the loose portions 160a, 160b and the set of yarns 102c of the central portion 110, which is located between these loose portions, at the same level and thus defines a support surface for the belt texture 40.

Claims

1. A method for manufacturing a fiber preform for a composite part intended to be articulated to other parts, comprising at least: - forming by weaving a first fiber core texture (1; 100) of elongate shape extending in a longitudinal direction (X) and comprising, in cross section, a central portion (10; 110) having, on its opposite sides (11; 111), two positioning edges (12; 120) each comprising two non-interlinked lateral fibrous portions (16a; 16b; 160a; 160b), - shaping the first fiber texture which involves at least opening out the non-interlinked lateral portions to form a positioning surface (30; 130) defined by the lateral portions thus opened out and by an interleaved fibrous portion, situated between these opened-out portions, formed by a prolongation (18a) of the central portion or by this central portion (110), and - positioning a second woven belt fiber texture (40) over the opened-out lateral portions and the interleaved fibrous portion, the second texture forming a loop around the shaped first texture so as to define, at the longitudinal ends between the first and second textures, empty spaces (42) intended for articulation to other parts.

2. The method according to claim 1, wherein each positioning edge (12) further comprises an interleaved fiber texture (18) extending the central portion (10) and located between the non-interlinked lateral fibrous portions (16a; 16b), and wherein the shaping further comprises cutting this interleaved fiber texture so as to form the interleaved fibrous portion (18a).

3. The method according to claim 1, wherein the central portion (110) comprises woven skins (102a; 102b) and a set of non-woven yarns (102c) located between the woven skins and held together by yarns (t4; t5) coming therefrom, the woven skins extending beyond the central portion into the positioning edges (120) to form the non-interlinked lateral fibrous portions (160a; 160b), and wherein these non-interlinked portions are opened-out so as to fold them down to the height of the set of non-woven yarns during shaping.

4. The method according to any one of claims 1 to 3, wherein the non-interlinked lateral fibrous portions (16a; 16b; 160a; 160b) are formed by weaving first and second yarns and have a first volume ratio of first yarns relative to the second yarns, and wherein the second texture (40) is formed by weaving first and second yarns and has a second volume ratio of first yarns relative to the second yarns, the relative difference between the first and second volume ratios not exceeding 25%.

5. The method according to any one of claims 1 to 4, wherein the first (1; 100) and second (40) textures are made of carbon yarns.

6. A method for manufacturing a composite material part intended to be articulated to other parts, comprising at least: - forming a fiber preform for the part to be obtained by implementing a method according to any one of claims 1 to 5, and - forming a matrix in a porosity of the fiber preform thus obtained.

7. The method according to claim 6, wherein the matrix is organic.

8. The method according to claim 6 or 7, wherein the part is a landing gear strut, a segment of a landing gear strut or a brake bar.