Fibre reinforcement for producing a composite part to be articulated with other parts

Abstract

The present invention relates to a fiber preform for the core of a fiber reinforcement of a composite part, the preform having an elongated shape along a longitudinal direction (X) and being formed by first yarns (C1-C16) extending along the longitudinal direction and second yarns (t1-t8) transverse to the first yarns. The preform includes two longitudinal ends for articulation with other parts and an intermediate region located between the longitudinal ends. The thickness of each longitudinal end is greater than the thickness of the intermediate region. The intermediate region includes a reinforcement section (102c), which includes first non-woven yarns (C5-C12), and each longitudinal end includes a three-dimensional braiding of the first yarns and the second yarns of the reinforcement section.

Description

Technical field

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

[0002] In order to reduce weight, it is possible to propose using composite materials instead of metallic materials, which has been a concern in the specific case of aircraft components. From this point of view, document US 7 704 429 proposes manufacturing a landing gear strut from a composite material, which strut includes regions called forks that are intended to be articulated with other components and to introduce stresses, and which is formed of a laminated structure in which interlayers are inserted between the main layers, extending the body of the reinforcement. However, this solution may have drawbacks. In fact, in order to avoid the risk of delamination, the forks having a laminated configuration may lead to an increase in the size of the stress-introduction regions compared to metallic components. Due to the increase in volume, the weight savings of the entire system become less attractive and the integration of the components is more restricted. Another problem is that the manufacturing techniques proposed involve a large amount of manual intervention, which may lead to non-compliance / inconsistency and an increase in costs. Finally, the mechanical properties of the composite materials proposed in this document can be improved, particularly with regard to the compressive strength in the intermediate region of the length of the component called the common region. One option for solving this problem is to add material in the common region, but this sacrifices quality and is therefore not entirely satisfactory.

[0003] The present invention aims to solve all or part of the abovementioned drawbacks. Summary of the invention

[0004] The present invention relates to a fiber preform for the core of a fiber reinforcement of a composite component, the preform having an elongated shape along a longitudinal direction and being formed of a first yarn extending along the longitudinal direction and a second yarn transverse to the first yarn, the preform including two longitudinal ends for articulating with other components together and an intermediate region located between the longitudinal ends, the thickness of each longitudinal end being greater than the thickness of the intermediate region, the intermediate region including a reinforcement section formed of a first non-woven yarn, and each longitudinal end including a three-dimensional braiding of the first and second yarns of the reinforcement section.

[0005] The present invention proposes an optimized design of a core preform of a core - belt component type fiber reinforcement, which is based on three - dimensional braiding technology and articulated regions with increased thickness compared to intermediate or common regions, in order to obtain improved tolerance for stress introduction regions. Compared with a structure obtained entirely by three - dimensional braiding, the strengthening section can significantly improve the compressive properties of the intermediate region. The present invention also limits or even avoids braiding with the second yarn in the intermediate region, which reduces material consumption and post - braiding processing (such as cutting). The first yarn of the strengthening section is braided at the longitudinal ends by three - dimensional braiding in order to obtain the required stress resistance / tolerance in the articulated regions.

[0006] In an exemplary embodiment, the fiber preform includes a braided outer skin on both sides of the strengthening section, wherein the first yarn of the strengthening section is held / fixed by the yarns from the braided outer skin.

[0007] This feature is beneficial for improving the impact resistance of the fiber reinforcement.

[0008] In particular, the braided outer skin may include folded, non - interconnected transverse fiber sections that form positioning surfaces for the fiber - belt structure on the upper and lower sides of the preform.

[0009] This feature helps to improve the quality of the interface between the core and the belt, further enhancing the mechanical properties of the component.

[0010] In an exemplary embodiment, the preform also includes transition regions between each longitudinal end and the intermediate region, which include additional first - yarn layers compared to the intermediate region and are braided with the second yarn in the longitudinal ends.

[0011] This feature is beneficial for achieving a further increase in the thickness of the longitudinal ends, thereby further improving the mechanical properties of the component.

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

[0013] The present invention also relates to a method for manufacturing a fiber reinforcement of a composite component, comprising:

[0014] - Positioning a braided fiber - belt structure on the preform of the core as described above, the belt structure defining a loop around the preform of the core so as to define a free space for articulation with other components at the longitudinal ends.

[0015] In an exemplary embodiment, the belt structure is made of carbon yarn.

[0016] The present invention also relates to a method for manufacturing a composite component intended to be articulated with other components, the method comprising:

[0017] - Form the fiber reinforcement as described above, and

[0018] - Form a matrix in the pores of the fiber reinforcement thus obtained.

[0019] In an exemplary 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 lever. Description of the Drawings

[0021] Figure 1 Figure 1 Schematically shows an example of the fiber structure intended to form a preform according to the invention.

[0022] Figure 2 Figure 2 Schematically shows Figure 1 a cross-section of the structure of

[0023] Figure 3A Figure 3A Schematically and partially shows the first possible forming step for the structure of Figure 1 and 2 the structure of

[0024] Figure 3B Figure 3B Schematically and partially shows the second possible forming step for the structure of Figure 1 and 2 the structure of

[0025] Figure 3C Figure 3C Schematically and partially shows the third possible forming step for the structure of Figure 1 and 2 the structure of

[0026] Figure 4 Figure 4 is a perspective view of an example of a fiber reinforcement of the core-belt assembly type according to the invention. Detailed Description

[0027] Figure 1 Shows a woven fiber structure 100, which is intended to form a fiber preform 200 (see Figure 3B , 3C and 4) after forming, and the fiber preform 200 is the core of the fiber reinforcement for a composite component. The following will be combined with Figures 3A to 3C ​​​​​​​​​​​​Describe the possible shaping of the structure. The structure 100 and the preform 200 have an elongated shape extending along the longitudinal direction X and can be obtained by braiding into a single piece. The structure 100 and the preform 200 successively include a first longitudinal end 103a, an intermediate region ZM, and a second longitudinal end 103b along the direction X. In the illustrated example, there is also 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 example, but within the framework of the present invention, the transition region ZTa is still optional. According to one example, the lengths La, Lb of each possible transition region ZTa, ZTb can be between 1% and 20% of the length LO of the structure 100 or the preform 200, and the lengths L2, L3 of each end 103a, 103b can be between 1% and 20% of the length LO. The length is measured along the direction X. The intermediate region ZM can be centered with respect to the plane P50 - the plane P50 is located at the middle length of the structure 100 or the preform 200 and is perpendicular to the direction X. In Figure 1 the illustrated example, 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 less than the thickness e2 but greater than the thickness e1. The thickness is measured along the thickness direction (direction E) 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 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.

[0028] The textile structures between the ends 103a, 103b, the transition regions ZTa, ZTb, and the intermediate region ZM are different, as will be detailed below. The ends 103a, 103b are obtained by three - dimensional braiding of a first yarn extending along the direction X and a second yarn transverse to the first yarn, for example using an "interlocking" braiding pattern. In the illustrated example, a part of the first yarn present in the ends 103a, 103b forms a reinforcing section 102c in the intermediate region ZM, and in this section 102c, it is not braided with the second yarn. The first yarn can extend in a substantially straight line in the reinforcing section 102c. The reinforcing section 102c can include a unidirectional layer of the first yarn. Generally, the number of the first non - braided yarns in the intermediate region ZM can be in the majority (more than 50%), for example at least 80% of all the yarns present in the intermediate region ZM. Second yarns are added in the longitudinal ends 103a, 103b in order to braid / interweave the first yarns of the reinforcing section 102c. Compared with the possible second - yarn layer in the intermediate region ZM, these added second yarns correspond to additional yarn layers. Figure 2Shows a possible textile configuration at the intermediate zone ZM (cross-sectional view relative to the direction X). Structure 100 includes a central section 110 having two positioning edges 120 on its opposite sides 111, each positioning edge including side sections 160a, 160b that are not interconnected, and the side sections 160a, 160b are separated by a non-interconnected region 140, thereby allowing these sections 160a, 160b to be spaced apart relative to each other. The positioning edges 120 and the central section 110 are offset in the width direction L, and the non-interconnected sections 160a, 160b are offset in the thickness direction E. The central section 110 includes a reinforcing section 102c, and the reinforcing section 102c includes first non-woven yarns C5-C12. Braided sheaths 102a, 102b obtained, for example, by three-dimensional braiding (such as by "interlocking" braiding) are present in the central section 110 and extend beyond its scope, thereby forming non-interconnected sections 160a, 160b. The sheaths 102a, 102b are formed by braiding between first yarns C1-C4 and C13-C16 extending in the longitudinal direction X and second yarns t1-t8 extending in the direction L. Generally speaking, it should be recognized that the illustrated number of yarn layers and the braiding pattern are provided only by way of example and can be modified without departing from the scope of the present invention. The sheaths 102a, 102b are located in the intermediate zone ZM, and they extend to the ends 103a, 103b, defining a single piece of fabric that extends over the entire width and thickness of the structure 100 or the preform 200. The yarns C5-C12 of the reinforcing section 102c are located between the sheaths 102a, 102b and are fixed together by the yarns from the sheaths 102a, 102b. In fact, it is worth noting that the yarn t4 extends beyond the central section 110 in the first sheath 102a and is deflected so as to come out / exposed from the first sheath 102a, thereby binding / fixing the group 102c of the yarns C5-C12 in the central section 110. Similarly, on the side opposite to the yarn t4, the yarn t5 extends beyond the central section 110 in the second sheath 102b and is deflected so as to come out / exposed from the second sheath 102b, thereby binding / fixing the group 102c of the yarns C5-C12 in the central section 110. Thus, encapsulation of the reinforcing section 102c (formed by the yarns C5-C12) between the sheaths 102a, 102b is achieved, and these yarns C5-C12 are fixed in place by the deflected yarns t4-t5. In the illustrated example, in the central section 110, in the thickness direction E in sequence are: the first sheath 102a, the section 102c formed by non-woven yarns, and the second sheath 102b. It should be noted that the section 102c formed by non-woven yarns only exists in the central section 110 and does not exist in the positioning edges 120. This allows saving of yarns in this area and avoids a manual cutting step (if these yarns were braided).As described above, the yarns C5-C12 are not only woven over a partial length of the first structure 100 or the preform 200 - woven over its intermediate region ZM and possibly over the transition regions ZTa, ZTb - but are also woven into the longitudinal ends 103a, 103b. The length of the non-woven yarns C5-C12 can be greater than or equal to 50%, for example 75%, of the length LO of the structure 100 or the preform 200.

[0029] Figures 3A to 3C is shown in a simplified manner Figure 1 and 2 the shaping of the structure 100 in order to obtain the positioning of the preform 200 and of the second belt structure 40. It should be understood that this configuration is symmetric with respect to the directions L and E. In the example considered, the non-connected sections 160a, 160b are unfolded in outline (not shown) so as to form an angle of approximately 90° with the direction L and the non-connected sections 160a, 160b are positioned at the height of the section 102c. The height is measured along the direction L. Thereby, the preform 200 is obtained which has a positioning surface 130 of substantially flat shape, with non-connected sections 160a, 160b at the same height and a section 102c located between these non-connected sections, thus defining a bearing surface for the belt structure 40. The cross-section of the preform 200 can have an I shape (referred to as double-angle) with respect to the longitudinal direction X. In Figure 1 the example, there are transition regions ZTa, ZTb between the intermediate region ZM and the ends 103a, 103b. The reinforcing section 102c is also present in the transition regions ZTa, ZTb, but the sheaths 104a1, 104a2, 104b1 and 104b2 are thickened with respect to the sheaths 102a, 102b of the intermediate region ZM. In fact, an additional first layer of yarns is added in this region with respect to the yarns present in the intermediate region ZM. As shown, the additional first layer of yarns in this region can be gradually woven with the second yarns to form the sheaths 104a1, 104a2, 104b1 and 104b2 and extend into the ends 103a, 103b in order to obtain the required thickness of the latter when a significant increase in thickness is needed.

[0030] Figure 4Shows an example of a core belt assembly according to the present invention, which forms a fiber reinforcement 300 of a part to be obtained. The braided belt structure 40 has been positioned around the preform 200, which is obtained after shaping the structure 100 by folding down the non-interconnected sections 160a, 160b. The structure 40 can have a strip shape wound around the preform 1. When positioned, the structure 40 is supported / abutted against the positioning surface 130. The structure 40 can be in the form of a single fabric strip, but it is also within the scope of the present invention if it is in the form of multiple strips connected end to end or placed side by side. The structure 40 can also be obtained by three-dimensional braiding, for example using an "interlocking" braiding pattern. The structure 40 defines a closed loop around the preform 200 and defines a free space 42 for articulation with other parts. Inserts (not shown) can be temporarily used at the longitudinal ends 103a, 103b, and a second structure 40 can be wound around them to ensure that the end regions have the desired shape. As shown, the ends 103a, 103b can have a curved shape, for example, substantially circular. The transverse dimension DT of the positioning surface 130 increases from the first end 103a towards the middle region ZM, being maximum near the middle length plane P50 of the preform 200, for example, at least maximum in the section located between the planes P40 and P60 - the planes P40 and P60 are located at 40% and 60% of the length LO and are perpendicular to the direction X, and then decreases towards the second end 103b. The positioning surface 130 defines side fins for positioning the belt structure 40. The volume ratio between the warp and weft yarns of each preform 200 and the belt structure 40 can be similar, for example, differing by at most 10%. For each textile considered, these volume ratios correspond to the following ratio: [volume occupied by warp yarns] / [volume occupied by weft yarns].

[0031] Then the entire preform 200 and the structure 40 are densified, for example, by introducing a resin (such as an epoxy resin), and then crosslinked if the resin is a thermosetting resin or cooled if the resin is a thermoplastic resin. The formation of the matrix can be carried out by resin transfer molding technology, which is a technique known per se. In this way, a composite part is obtained, which is intended to be articulated with other parts at its longitudinal ends and withstand tensile and compressive stresses. The fiber reinforcement of this part can be formed by carbon yarns, and this part can have the organic matrix described above. This part can be used or not used in aviation applications. This part can be, for example, a connecting rod, a landing gear strut or its component elements, or a brake lever. The obtained part can be mounted to other parts by positioning a hinge pin for connecting to other parts and a contact insert with the pin in the free space 42.

Claims

1. A method for manufacturing a fiber reinforcement (300) for a composite component, comprising: - positioning a woven fiber tape structure (40) on a fiber preform (200) of a core of a fiber reinforcement (300) for a composite component, the preform having an elongated shape along a longitudinal direction (X) and being formed by first yarns (C1-C16) extending along the longitudinal direction and second yarns (t1-t8) transverse to the first yarns, the preform including two longitudinal ends (103a; 103b) for articulation with other components, and an intermediate region (ZM) located between the longitudinal ends, the thickness (e2; e3) of each longitudinal end being greater than the thickness (e1) of the intermediate region, the intermediate region including a reinforcement section (102c), the reinforcement section including first non-woven yarns (C5-C12), and each longitudinal end including a three-dimensional weaving of the first and second yarns of the reinforcement section, the tape structure defining a loop around the preform of the core so as to define a free space (42) for articulation with other components at the longitudinal ends.

2. The method according to claim 1, wherein The fiber preform includes woven outer skins (102a; 102b) located on both sides of the reinforcement section (102c), wherein the first yarns (C5-C12) of the reinforcement section are held by yarns (t4; t5) from the woven outer skins.

3. The method according to claim 2, wherein The woven outer skins (102a; 102b) include folded, non-connected transverse fiber sections (160a; 160b) that form positioning surfaces (130) for the fiber tape structure (40) on the upper and lower sides (111) of the preform.

4. The method according to any one of claims 1 to 3, wherein, The preform further includes transition regions (ZTa; ZTb) located between each longitudinal end (103a; 103b) and the intermediate region (ZM), the transition regions including additional first yarn layers that are woven with the second yarns in the longitudinal ends, compared to the yarns present in the intermediate region.

5. The method according to claim 4, wherein, The preform is made of carbon yarn.

6. The method according to claim 4, wherein, The tape structure (40) is made of carbon yarn.

7. A method for manufacturing a composite component intended for articulation with other components, comprising: - forming a fiber reinforcement (300) according to the method of any one of claims 1 to 6, and - forming a matrix in the pores of the fiber reinforcement thus obtained.

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 composite component is a landing gear strut, a part of a landing gear strut, or a brake lever.

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