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

Abstract

The present invention relates to a fibrous preform 1 of a core part of a fibrous reinforcement for a composite material part, wherein the preform is formed by three-dimensional weaving of a first thread extending along the longitudinal direction and a second thread crossing the first thread. In the fibrous preform, the preform comprises two longitudinal ends 3a; 3b for articulation with other parts and an intermediate region ZM located between the two longitudinal ends. Each longitudinal end has a thickness greater than the thickness of the intermediate region, the intermediate region has a first volume ratio of the first thread to the second thread greater than 1, and each longitudinal end has a second volume ratio of the first thread to the second thread smaller than the first volume ratio and closer to 1 than this first volume ratio.

Description

Technical Field

[0001] The present invention relates to a fibrous preform intended to form part of a 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 with a view to weight reduction, which is always a concern in the particular case of aircraft components. For this purpose, Patent Document 1 (U.S. Patent No. 7,704,429) proposes the manufacture of a landing gear strut made of a composite material having a region called a fork, the fork being intended for articulation and force introduction with another component 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 overall mass saving of the system becomes less interesting and the integration of the component becomes more restrictive due to the increase in space requirements. Another problem is that the proposed manufacturing technique involves a significant amount of manual work which can lead to incompatibilities and increased costs. Finally, the mechanical performance of the composite materials proposed herein can be improved, particularly with regard to the compressive strength over an intermediate region of the length of the component, called the common region. One option to respond to this is to add material to the common region, which is disadvantageous from a mass point of view 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 some of the aforementioned drawbacks.

Means for Solving the Problems

[0005] The present invention relates to a fibrous preform of a core portion of a fibrous reinforcing material for a composite material part, the fibrous preform having an elongated shape along a longitudinal direction and being formed by a three-dimensional weave of a first yarn extending along the longitudinal direction and a second yarn crossing the first yarn. The preform comprises two longitudinal ends for articulation with other parts and an intermediate region located between the two longitudinal ends. Each longitudinal end has a thickness greater than the thickness of the intermediate region. The intermediate region has a first volume ratio of the first yarn to the second yarn greater than 1, and each longitudinal end has a second volume ratio of the first yarn to the second yarn smaller than the first volume ratio and closer to 1 than the first volume ratio.

[0006] The volume ratio of the first yarn to the second yarn corresponds to the ratio of [volume occupied by the first yarn] / [volume occupied by the second yarn]. For the sake of brevity, this ratio may hereinafter be designated by the term "F1 / F2 ratio". In a specific case where the first yarn corresponds to the warp yarn, this ratio corresponds to the warp / weft ratio. In a variant embodiment, the first yarn can correspond to the weft yarn and the second yarn can correspond to the warp yarn.

[0007] The present invention proposes an optimized design of a core preform of a fibrous reinforcement of the core belt assembly type based on three-dimensional weaving technology and a joint region having an excessive thickness with respect to an intermediate region or a common region in order to obtain an improved resistance to force. Furthermore, it is proposed to enable a design having a constant or substantially constant number of layers of the first yarn over the entire length of the preform while rebalancing the F1 / F2 ratio in these joint regions so as to control the fiber content. Thus, the manufacturing is repeatable by eliminating as much as possible the manual steps, and provides a reinforcement of improved quality by avoiding or greatly limiting the local addition of the first yarn to the ends having an excessive thickness and the subsequent cutting, which can result in manufacturing incompatibilities due to the remaining small lengths.

[0008] In one embodiment, each longitudinal end has a spacing between successive rows of the second yarn that is smaller than the spacing between successive rows of the second yarn within the intermediate region.

[0009] Such a characteristic constitutes a first solution that enables the F1 / F2 ratio to be changed and rebalanced at the longitudinal ends.

[0010] In an alternative embodiment, or in combination, each longitudinal end has a weight of the second yarn that is greater than the weight of the second yarn in the intermediate region.

[0011] Such a characteristic constitutes a second solution that enables the F1 / F2 ratio to be changed and rebalanced at the longitudinal ends.

[0012] Of course, it is possible to change the F1 / F2 ratio by changing both the spacing and the weight of the rows of the second yarn.

[0013] In an exemplary embodiment, the preform defines upper and lower positioning edges having a lateral dimension measured transversely to the longitudinal direction, and these edges occur and pass through a maximum value within the intermediate region.

[0014] This increased lateral dimension increases the inertia of the component, which is beneficial for buckling, bending, and certain vibration modes. Additionally, the strength of the interface increases with the increase in the surface.

[0015] In an exemplary embodiment, the preform is made from carbon filaments.

[0016] The present invention also relates to a method for manufacturing a fibrous reinforcement for a composite component, the method comprising: positioning a woven fiber belt texture on a preform of the core portion as described above, the belt texture defining a loop around the preform of the core portion so as to define a free space intended for articulation with other components at the longitudinal ends.

[0017] In one embodiment, the belt texture is made from carbon filaments.

[0018] The present invention also relates to a method for manufacturing a composite component intended to articulate with other components, the method comprising: forming a fibrous reinforcement as described above; and forming a matrix in the porosity of the fibrous reinforcement thus obtained.

[0019] In one embodiment, the matrix is an organic matrix.

[0020] 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

[0021]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0022] Figure 1 shows a fibrous preform 1 of the core of a fibrous reinforcement for a part made of a composite material. The preform 1 has an extended shape extending along the longitudinal direction X. The preform 1 can be obtained, for example, by a single-piece three-dimensional weaving using an "interlock" pattern weave. The term "three-dimensional weaving" or "3D weaving" is understood to mean a weaving method in which at least some of the first threads oriented in the longitudinal direction X join the second threads in a transverse direction with respect to the first threads on some layers of the second threads. Such weaving can be carried out on a Jacquard loom by a method known per se. The preform 1 continuously comprises a first longitudinal end 3a, an intermediate region ZM, and a second longitudinal end 3b along the longitudinal direction X. Each of the first end 3a, the intermediate region ZM, and the second end 3b can be obtained by three-dimensional weaving and can be located within the stretching range of the fabric relative to each other. The intermediate region ZM can be designed to receive tensile and compressive forces. The longitudinal ends 3a, 3b have a curved shape, for example, substantially circular, and are intended to define a free space for articulation with other parts in the resulting part. According to one example, the intermediate region ZM can have a length L1 that is 50% to 98% of the length LO of the preform 1, and each end 3a, 3b can have lengths L2, L3 that are 1% to 25% of the length LO. The length is measured along the longitudinal direction X. The intermediate region ZM is located halfway along the length of the preform 1 and can be centered with respect to a plane P50 perpendicular to the longitudinal direction X. Here, the longitudinal ends 3a, 3b have different dimensions, particularly different widths LA2, LA3, measured along the width direction L, and the preform 1 defines positioning edges 12 extending along the longitudinal direction X on its upper and lower sides and defines a surface 30 for positioning the belt texture. The transverse dimension DT of the positioning edge 12 in the intermediate region ZM is larger than the transverse dimension DT at the ends 3a, 3b.This dimension DT, as shown in the figure, increases over the intermediate region ZM when moving from the first end 3a, and is, for example, located between the surfaces P40 and P60 at positions 40% and 60% of the length LO, and is maximum in the vicinity of the intermediate length surface P50 of the preform 1, and at least increases over a cross-section perpendicular to the longitudinal direction X, and then may decrease over the intermediate region ZM in the direction of the second end 3b. In cross-section, the preform 1 comprises a central portion 10 having two positioning edges 12 on its upper and lower sides. In the example shown in the figure, the edges 12 and the central portion 10 are offset along the width (direction L). The preform 1 can be obtained by integrally three-dimensionally weaving fiber strips and providing an unconnected region so as to form the positioning edges 12 after folding the unconnected portions 16a and 16b. A central portion 18 that enables obtaining a positioning surface 30 of a substantially flat shape may exist between the portions 16a and 16b and can be obtained by cutting an unconnected intermediate texture from the portions 16a and 16b. In the example shown and shown in FIGS. 2A to 2C, the thickness e2 of the first end 3a is greater than the thickness e1 of the intermediate region ZM. The thickness e3 of the second end 3b 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. According to one example, the e2 / e1 ratio can be greater than 1 and less than or equal to 4, for example, 1.5 to 2.5, and the e3 / e1 ratio can be greater than 1 and less than or equal to 4, for example, 1.5 to 2.5. As shown in the figure, the preform 1 can have an I-shaped cross-section (referred to as a double angle shape) in the cross-section with respect to the longitudinal direction X. In the example shown in the figure, the positioning edges 12 each form an angle substantially equal to 90° with the direction L. The positioning edges 12 form lateral fins for positioning the belt texture. The preform 1 defines a positioning surface 30 at the positioning edges 12 where the belt texture is intended to be deposited.

[0023] As described above, the F1 / F2 ratio at the ends 3a and 3b is smaller than the F1 / F2 ratio in the intermediate region ZM and closer to 1 than the F1 / F2 ratio in the intermediate region ZM. Therefore, the absolute value of the difference of [(the second volume ratio of the first yarn to the second yarn) - 1] is smaller than [(the first volume ratio of the first yarn to the second yarn) - 1]. According to an example, the F1 / F2 ratio in the intermediate region ZM is from 1.2 to 9, and the F1 / F2 ratio at the ends 3a and 3b is from 0.6 to 4. It should be noted that the ends 3a and 3b may have the same or different F1 / F2 ratios. FIGS. 3 and 4 show various ways of varying the F1 / F2 ratio. In the example of FIG. 3, the spacing ESN between consecutive rows CLN and CLN+1 of the second yarn 22 is modified to decrease to a value ES2 in the lower end regions 3a, 3b than the value ES1 in the intermediate region ZM. As shown, this change can be made gradually by passing through one or more intermediate values ES3 that are greater than ES2 and less than ES1. According to an example, the ES1 / ES2 ratio can be from 1 to 5. FIG. 4 shows the case where the weight of the second yarn is increased in the end regions 3a, 3b with respect to the intermediate region ZM between the first weight t1 and the second weight t2 (yarn 221 having weight t1 and yarn 222 having weight t2). This progression can be made gradual by passing through a second yarn 223 having one or more intermediate weights t3 greater than t1 while being less than t2.

[0024] The above described an example of the preform 1 according to the present invention. This preform 1 is only intended to form a part of the fibrous reinforcement 50 of the composite material part to be obtained. Hereinafter, as shown in FIG. 5, the subsequent manufacture of the part having positioning around the preform 1 of the woven belt texture 40 will be described. The texture 40 can be in the form of a strip wound around the preform 1. The texture 40 will come into contact with the positioning surface 30 during its positioning. The texture 40 can be in the form of a single strip of cloth, but it does not exceed the scope of the present invention if it is in the form of several strips arranged from end to end or from side to side. The texture 40 can also be obtained, for example, by three-dimensional weaving by interlock weaving. The texture 40 defines a closed loop around the preform 1 and defines a free space 42 intended for articulation with other parts. The texture 40 can follow the shape of the positioning edge 12 so as to completely cover them. Inserts (not shown) can be temporarily used at the longitudinal end 3, and a second texture 40 can be wound around them to ensure the desired shape for the end region. Then, the entire preform 1 and texture 40 are introduced with a resin such as, for example, an epoxy resin, and then, if it is a thermosetting resin, the resin is crosslinked, or if it is a thermoplastic resin, it is cooled. The matrix can be formed by resin transfer molding technology corresponding to techniques known per se. The composite material part thus obtained is intended to be articulated with other parts at its longitudinal ends. The fibrous reinforcement 50 of the part can be formed of carbon yarns, and the part can have an organic matrix as described above. The part may or may not be for aerospace 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 an insert for contacting this pin through the free space 42.

Claims

1. A fibrous preform (1) for the core portion of a fibrous reinforcing material (50) for a part of a composite material, wherein the fibrous preform has an extended shape along the longitudinal direction (X) and is formed by a three-dimensional weave of a first thread extending along the longitudinal direction and a second thread crossing the first thread, The fibrous preform comprises two longitudinal ends (3a; 3b) intended to articulate with other parts, and an intermediate region (ZM) located between the two longitudinal ends (3a; 3b), wherein each longitudinal end has a thickness (e2; e3) greater than the thickness (e1) of the intermediate region, the intermediate region has a first volume ratio of first yarn to second yarn greater than 1, and each longitudinal end has a second volume ratio of first yarn to second yarn that is less than the first volume ratio and closer to 1 than the first volume ratio. The fibrous preform (1) defines a positioning edge (12) on the upper and lower sides having a transverse dimension (DT) measured laterally with respect to the longitudinal direction (X), and the positioning edge develops in the intermediate region (ZM) and passes through the maximum value.

2. The fibrous preform (1) according to claim 1, wherein each longitudinal end (3a; 3b) has a spacing (ES2) between consecutive rows of the second yarn that is smaller than the spacing (ES1) between consecutive rows of the second yarn in the intermediate region (ZM).

3. The fibrous preform (1) according to claim 1, wherein each longitudinal end (3a; 3b) has a second yarn weight (t2; t3) greater than the second yarn weight (t1) in the intermediate region (ZM).

4. The fibrous preform (1) according to claim 1, wherein the fibrous preform is made from carbon yarn.

5. In a method for manufacturing a fibrous reinforcing material (50) for a composite material part, The aforementioned method, A method comprising positioning a woven fiber belt texture (40) on a core portion preform (1) as described in claim 1, wherein the woven fiber belt texture defines a loop around the core portion preform such that it defines a free space (42) for articulating with other parts at the longitudinal ends (3a; 3b).

6. The method according to claim 5, wherein the woven fiber belt texture (40) is made from carbon yarn.

7. In a method for manufacturing a composite part intended to be articulated with other parts, The aforementioned method, To form the fibrous reinforcing material (50) described in claim 5, A method comprising forming a matrix in the porosity of the fibrous reinforcing material obtained in this manner.

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

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

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