Fibrous reinforcement for producing composite component hinged to other components

Abstract

The invention relates to a fibrous preform (1) for a core part of a fibrous reinforcement of a composite component, having an elongated shape in a longitudinal direction (X) and formed by three-dimensional weaving of a first yarn extending in the longitudinal direction with a second yarn transverse to the first yarn, the preform comprises: two longitudinal ends (3a, 3b) for articulating with other components, each longitudinal end having a thickness greater than the thickness of the median region, and a median region (ZM) located between the longitudinal ends, the median region having 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 that is smaller than the first volume ratio and closer to 1 than the first volume ratio.

Description

Technical Field

[0001] The invention relates to a fiber preform for forming part of a fiber reinforcement of a component made of composite material, the component being intended to be articulated at its ends to other components, and to a related manufacturing method. Background Art

[0002] The use of composite materials instead of metal materials can be proposed in order to reduce weight, which is a constant concern in the specific case of aircraft components. To this end, document US 7 704 429 proposes the manufacture of a landing gear strut made of composite materials, which includes areas called forks, which are used for articulation and stress introduction with other components and are formed by a laminated structure in which plies are interspersed between the main plies of the main body extending the reinforcement. However, despite this, this solution may have disadvantages. In fact, forks with a laminated configuration may lead to an increase in the size of the stress introduction area compared to metal parts to avoid the risk of delamination. Due to the increase in space requirements, the mass saving of the entire system becomes less attractive and the integration of the components becomes more stringent. Another problem is that the proposed manufacturing technology implements a lot of manual work, which may lead to non-conformity and increased costs. Finally, the mechanical properties of the composite material proposed in this article can be improved, especially in terms of compressive strength on the median area of ​​the length of the component, called the common area. One option to deal with this problem is to add material in the common area, which reduces the quality and therefore cannot be fully satisfied.

[0003] The present invention aims to address all or part of the above disadvantages. Summary of the invention

[0004] The present invention relates to a fiber preform for a core part of a fiber reinforcement of a composite material component, the preform having an elongated shape along a longitudinal direction and formed by three-dimensionally weaving a first yarn extending along the longitudinal direction and a second yarn transverse to the first yarn, the preform comprising: two longitudinal ends for hinged connection with other components and a middle area between the longitudinal ends, each longitudinal end having a thickness greater than that of the middle area, the middle area having a first volume ratio of the first yarn to the second yarn greater than 1, each longitudinal end having a second volume ratio of the first yarn to the second yarn, the second volume ratio being smaller than the first volume ratio and closer to 1 than the first volume ratio.

[0005] The volume ratio of the first yarn to the second yarn corresponds to the ratio [volume occupied by the first yarn] / [volume occupied by the second yarn]. For simplicity, the ratio may be referred to as "F1 / F2 ratio" hereinafter. In the specific case where the first yarn corresponds to the warp yarn, this ratio corresponds to the warp / weft ratio. In a variant, the first yarn may correspond to the weft yarn and the second yarn to the warp yarn.

[0006] The invention proposes an optimized design of a core preform of a fiber reinforcement of the core band assembly type, which is based on three-dimensional weaving technology and articulation areas with excess thickness relative to the median area or common area in order to obtain better resistance. In addition, it is proposed to rebalance the F1 / F2 ratio in these articulation areas in order to control the fiber content while allowing the design of a first yarn with a constant or substantially constant number of layers over the entire length of the preform. Therefore, by eliminating manual steps as much as possible, the manufacturing is repeatable and the quality is improved by avoiding or greatly limiting the local addition of the first yarn at the end with excessive thickness and its subsequent cutting (which may lead to non-conformity in production due to slight remaining overlength).

[0007] In one embodiment, each longitudinal end portion has a spacing between consecutive rows of second yarns that is smaller than a spacing between consecutive rows of second yarns in said median region.

[0008] This characteristic constitutes a first solution allowing the F1 / F2 ratio to be modified in order to rebalance it at the longitudinal ends.

[0009] In a variant or combination, the weight of the second yarn at each longitudinal end is greater than the weight of the second yarn in the median zone.

[0010] This characteristic constitutes a second solution allowing modification of the F1 / F2 ratio in order to rebalance it at the longitudinal ends.

[0011] Of course, the F1 / F2 ratio can be modified by modifying both the inter-row spacing and the weight of the second yarn.

[0012] In an exemplary embodiment, the preform defines, on the upper side and on the lower side, positioning edges having a transverse dimension, measured transversely to the longitudinal direction, which gradually changes and reaches a maximum value in the median region.

[0013] This increased lateral dimension increases the inertia of the component, which is beneficial for buckling, bending and certain vibration modes. In addition, the strength of the interface increases as the surface increases.

[0014] In an exemplary embodiment, the preform is made from carbon yarn.

[0015] The invention also relates to a method for producing a fiber reinforcement for a composite material component, the method comprising: - As described above, positioning a woven fabric tape on the preform of the core, said tape defining a ring around said preform of the core so as to define, at said longitudinal ends, a free space for articulation with other parts.

[0016] In one embodiment, the tape texture is made of carbon yarn.

[0017] The invention also relates to a method for producing a composite component for articulation with other components, the method comprising: - forming a fiber reinforcement as described above; and - Formation of a matrix in the pores of the fiber reinforcement thus obtained.

[0018] In one embodiment, the matrix is ​​an organic matrix.

[0019] In an exemplary embodiment, the component is a landing gear strut, a portion of a landing gear strut, or a brake rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 An example of a fiber core preform according to the invention is shown.

[0021] Figure 2A Shows Figure 1 A cross-section of a preform over a first region of its length.

[0022] Figure 2B Shows Figure 1 A cross-section of the preform over a second region of its length.

[0023] Figure 2C Shows Figure 1 A cross section of a preform over a third region of its length.

[0024] Figure 3 A detail of an example of a longitudinal end of a core preform according to the invention is shown.

[0025] Figure 4 A detail of an example of a longitudinal end of a core preform according to the invention is shown.

[0026] Figure 5 shows that positioning the texture on Figure 1 The fiber reinforcement of the composite component is then obtained on the preform. DETAILED DESCRIPTION

[0027] Figure 1A fiber preform 1 for the core of a fiber reinforcement of a component made of composite material is shown. The preform 1 has an elongated shape extending in a longitudinal direction X. It can be obtained by three-dimensional weaving of a single piece using, for example, an "interlocking" pattern weaving. The term "three-dimensional weaving" or "3D weaving" is understood to refer to a weaving method by which at least some first yarns pointing in the direction X bind the second yarns transverse to the first yarns to several layers of second yarns. This weaving can be performed on a jacquard loom in a manner known per se. The preform 1 includes, in sequence, along the direction X: a first longitudinal end 3a, a median region ZM and a second longitudinal end 3b. Each of the first end 3a, the median region ZM and the second end 3b can be obtained by three-dimensional weaving and can be located in a fabric extension of each other. The median region ZM can be designed to withstand tensile and compressive forces. The longitudinal ends 3a, 3b have a curved shape, such as a substantially circular shape, and are used to define a free space dedicated to articulation with other components in the component to be obtained. According to one example, the length L1 of the median zone ZM may be between 50% and 98% of the length LO of the preform 1, and the length L2, L3 of each end 3a, 3b may be between 1% and 25% of the length LO. These lengths are measured along the direction X. The median zone ZM may be centered relative to a plane P50 located halfway along the length of the preform 1 and perpendicular to the direction X. Here, the longitudinal ends 3a, 3b have different dimensions, and in particular different widths LA2, LA3, which are measured along the width direction L. The preform 1 defines, on its upper and lower sides, a positioning edge 12 extending along the longitudinal direction X and defining a surface 30 for positioning the texture. The transverse dimension DT of the positioning edge 12 in the median zone ZM is larger than its transverse dimension in the ends 3a, 3b. As illustrated, when moving from the first end 3a, the dimension DT can increase in the median region ZM and be maximum near the mid-length plane P50 of the preform 1, for example, at least in the section between the planes P40 and P60 located at 40% and 60% of the length LO and perpendicular to the direction X, and then decrease in the median region ZM in the direction of the second end 3b. In cross section, the preform 1 includes a central portion 10 having two positioning edges 12 on its upper and lower sides. In the illustrated example, the edges 12 and the central portion 10 are offset along the width (direction L). The preform 1 can be obtained by weaving the fiber strips three-dimensionally into one piece, providing a non-interconnected area so that the positioning edge 12 is formed after the non-interconnected portions 16a and 16b are folded down. The intermediate portion 18 that enables the positioning surface 30 of a substantially flat shape to be obtained can be present between the portions 16a and 16b and can be obtained by cutting from the portions 16a and 16b by the non-interconnected intermediate texture. In the example shown and as FIG. 2A to FIG. 2CAs illustrated in , the thickness e2 of the first end 3a is greater than the thickness e1 of the middle zone ZM. The thickness e3 of the second end 3b is smaller than the thickness e2 but greater than the thickness e1. These thicknesses are measured along the thickness direction (direction E) and correspond to the minimum dimension. According to an example, the ratio e2 / e1 can be greater than 1 and less than or equal to 4, for example, between 1.5 and 2.5, and the ratio e3 / e1 can be greater than 1 and less than or equal to 4, for example, between 1.5 and 2.5. As illustrated in the figure, the preform 1 can have an I shape (called a double angle shape) relative to the longitudinal direction X in cross section. In the illustrated example, the positioning edges 12 each form an angle substantially equal to 90° with the direction L. The positioning edge 12 forms a transverse wing for positioning a texture. The preform 1 defines a positioning surface 30 for depositing a texture thereon at the positioning edge 12.

[0028] As described above, the F1 / F2 ratio in the end portions 3a and 3b is smaller than the F1 / F2 ratio in the middle zone ZM and is closer to 1 than the latter. Therefore, the absolute value of the difference [(the second volume ratio of the first yarn to the second yarn)-1] is smaller than the difference [(the first volume ratio of the first yarn to the second yarn)-1]. According to one example, the F1 / F2 ratio in the middle zone ZM may be between 1.2 and 9, and the F1 / F2 ratio in the end portions 3a and 3b may be between 0.6 and 4. It should be noted that the end portions 3a and 3b may have the same or different F1 / F2 ratios. Figure 3 and Figure 4 Different methods of changing the F1 / F2 ratio are shown. Figure 3 In the example of the embodiment of the invention, the spacing ESN between the consecutive columns CLN and CLN+1 of the second yarn 22 is modified so as to be reduced to a value ES2 in the end regions 3a, 3b lower than the value ES1 in the middle region ZM. As illustrated in the figure, this change can be gradually achieved by passing one or more intermediate values ​​ES3 that are less than ES1 and greater than ES2. According to one example, the ES1 / ES2 ratio can be between 1 and 5. Figure 4 The weight of the second yarn is shown increasing in the end zones 3a, 3b relative to the middle zone ZM between the first weight t1 and the second weight t2 (the weight of the yarn 221 is t1 and the weight of the yarn 222 is t2). This progression can be gradual by passing through the second yarn 223 having one or more intermediate weights t3 greater than t1 and less than t2.

[0029] An example of a preform 1 according to the invention has just been described. This preform 1 is used only to form a component of the fiber reinforcement 50 of the composite component to be obtained. The subsequent production of this component is described below and comprises: positioning the woven tape texture 40 around the preform 1, such as Figure 5. The texture 40 may be in the form of a strip wound around the preform 1. During its positioning, the texture 40 comes to bear on the positioning surface 30. The texture 40 may be in the form of a single strip of fabric, but it would not be beyond the scope of the invention if it were in the form of several strips connected end to end or placed side by side. The texture 40 may also be obtained by three-dimensional weaving, for example with interlocking weaving. The texture 40 defines a loop around the preform 1 and defines a free space 42 for articulation with other parts. The texture 40 may follow the shape of the positioning edges 12, thus completely covering them. Inserts (not shown) may be temporarily used at the longitudinal ends 3, and a second texture 40 may be wrapped around them, thus ensuring the desired shape for the end region. The entire preform 1 and the texture 40 are then densified, for example by introducing a resin (for example, an epoxy resin), then crosslinking the resin (if it is a thermosetting resin) or cooling (if it is a thermoplastic resin). The matrix may be formed by a resin transfer molding technique, which corresponds to a technique known per se. Thus, a composite component can be obtained, which is used for articulation with other components at its longitudinal ends. The fiber reinforcement 50 of the component can be formed by carbon yarns, and the component can have an organic matrix as described above. The component may be used for aviation applications, or not for aviation applications. For example, the component can be a connecting rod, a landing gear strut or a part thereof, or a brake lever. By positioning the hinge pin for connection to the other component and the insert for contacting the pin through the free space 42, the obtained component can be mounted on the other component.

Claims

1. A fiber preform (1) for a core part of a fiber reinforcement (50) for a composite material component, the preform having an elongated shape along a longitudinal direction (X) and formed by three-dimensionally weaving a first yarn extending along the longitudinal direction and a second yarn transverse to the first yarn; The preform comprises: Two longitudinal ends (3a, 3b), the two longitudinal ends are used for hinge connection with other components; and a middle zone (ZM), wherein the middle zone is located between the longitudinal ends, each longitudinal end having a thickness (e2, e3) greater than a thickness (e1) of the middle zone, the middle zone having a first volume ratio of the first yarn to the second yarn greater than 1, and each longitudinal end having a second volume ratio of the first yarn to the second yarn, the second volume ratio being smaller than the first volume ratio and closer to 1 than the first volume ratio.

2. The fiber preform (1) according to claim 1, wherein: Each longitudinal end portion (3a, 3b) has a spacing (ES2) between consecutive rows of second yarns that is smaller than the spacing (ES1) between consecutive rows of second yarns in said median zone (ZM).

3. The fiber preform (1) according to claim 1 or 2, wherein: The weight (t2, t3) of the second yarn at each longitudinal end (3a, 3b) is greater than the weight (t1) of the second yarn in the middle zone (ZM).

4. The fiber preform (1) according to any one of claims 1 to 3, wherein: The preform defines, on the upper side and on the lower side, positioning edges (12) having a transverse dimension (DT) measured transversely to the longitudinal direction (X), which varies gradually and reaches a maximum in the median zone (ZM).

5. The fiber preform (1) according to any one of claims 1 to 4, wherein: The preform is made of carbon yarn.

6. A method for manufacturing a fiber reinforcement (50) for a composite material component, comprising: A woven fiber tape texture (40) is positioned on a preform (1) of a core part according to any one of claims 1 to 5, the tape texture defining a ring around the preform of the core part so as to define a free space (42) at the longitudinal ends (3a, 3b) for articulation with other parts.

7. The method according to claim 6, wherein: The texture (40) is made of carbon yarn.

8. A method of manufacturing a composite component for articulation with other components, comprising: forming a fiber reinforcement (50) according to claim 6 or 7, and A matrix is ​​formed in the pores of the fiber reinforcement thus obtained.

9. The method according to claim 8, wherein: The matrix is ​​an organic matrix.

10. The method according to claim 8 or 9, wherein: The component is a landing gear strut, a portion of a landing gear strut or a brake rod.

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