Fibrous web with a debonding zone

Abstract

The invention relates to a fibrous web (10) formed by three-dimensional weaving of first and second yarns, the fibrous web (10) being elongate along a longitudinal axis and comprising a debonding zone (20) present between a first region (11) and a second region (12), the first region comprising woven first lateral portions (11a) connected by a first intermediate portion, the second region comprising second lateral portions (12a) connected by a second intermediate portion (12b) and woven with the first lateral portions, the first yarns extending transversely to the longitudinal axis and comprising a first set (412) extending in the second region and a second set (413) extending in the first region and overlying the debonding zone, the second set (413) crossing the first set (412) in a crossing zone (30) adjacent to the edges (20a) of the debonding zone, so as to extend into the second lateral portions.

Description

[0001] Description

[0002] Title of the invention: Fiber strip with unbinding zone

[0003] Technical Field

[0004] The present invention relates to the general field of manufacturing composite parts intended to be articulated with other parts at their ends, and more particularly to a fibrous strip intended to form the fibrous preform of a core of such a part.

[0005] Previous technique

[0006] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by different countries. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations.

[0007] Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

[0008] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The applicant takes into account the factors impacting all phases of design and development in order to obtain less energy-intensive and more environmentally friendly aeronautical components and products, whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving aircraft energy efficiency.

[0009] Consequently, the applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0010] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter onboard equipment, the development of the use of electric technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0011] The use of composite materials as a replacement for metallic materials can therefore be proposed with a view to reducing weight, which is a constant concern in the particular case of aircraft parts.

[0012] To this end, US patent 7704429 proposed manufacturing landing gear struts from composite materials. These struts include regions, called cleats, designed for articulation and load transfer with other components. They are formed by a laminated structure with intercalated plies between primary plies extending from the body of the reinforcement. However, this solution may have drawbacks. Indeed, cleats with a laminated configuration can lead to an increase in the size of the load transfer areas compared to metal components, in order to prevent delamination. The overall system weight reduction then becomes less significant, and the integration of the component becomes more challenging due to the increased size.

[0013] Another problem 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 midline area of ​​the part's length, known as the "current zone." One option to address this is to add material to the current zone, which increases the weight and is therefore not entirely satisfactory. Thus, document FR 3 152424 proposes a landing gear strut with an H-shaped web produced in a single piece by three-dimensionally weaving a fibrous strip composed of strands, then shaping this fibrous strip around a debonding zone that forms the central part of the component.However, the high tensile or compressive force generates parasitic forces in the central part of the piece which have the effect of separating the two massive areas held by the central part.

[0014] Document FR 3 141 094 proposes a blade made of composite material whose foot is made from a three-dimensional woven fibrous blank which includes weft crossings.

[0015] It is therefore desirable to improve the holding of the unbundling zone by modifying the trajectory of the strands so that their orientation tends towards that of the force after the shaping of the fibrous strip.

[0016] Description of the invention

[0017] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft. The invention relates to a one-piece fibrous strip formed by three-dimensional weaving through the bonding of first yarns with second yarns. The fibrous strip has a slender shape along a longitudinal axis and comprises a debonding zone extending along the longitudinal axis between lateral edges of the fibrous strip, defining a first region superimposed on a second region that can be separated from the first region. The debonding zone is present between the first and second regions. The first region comprises first woven lateral portions connected by a first intermediate portion.and the second region comprising second lateral portions connected by a second intermediate portion and woven with the first lateral portions, the first yarns extending transversely to the longitudinal axis and comprising a first set of layers of first yarns extending into the second region and a second set of layers of first yarns extending into the first region covering the unlinking zone, characterized in that the second set crosses, in a crossing zone adjacent to each edge of the unlinking zone, the first set so as to extend into the second lateral portions.

[0018] This allows for the production of a single-piece, monolithic fiber strip with improved bond strength. Indeed, the strands of the second assembly will orient themselves more naturally towards the second zone and its lateral portions when a folding force is applied to the edges of the bond zone to form, for example, an H-shaped fiber core preform. According to a particular feature of the invention, consecutive layers of the second assembly intersect, at each intersection point, consecutive layers of the first assembly.

[0019] By crossing several consecutive layers of the second set with the first set, the strength of the unbinding zone can be further improved, as a greater number of strands will naturally orient themselves towards the applied shaping force of the fibrous strip.

[0020] According to another particular feature of the invention, on each second lateral portion, a first group of consecutive layers from the first set is offset along the thickness direction of a second group of consecutive layers from the second set.

[0021] According to one embodiment of the invention, the second group can be intercalated, on each second lateral portion, between the first group and a third group of layers of first yarns extending into the second region.

[0022] According to another embodiment of the invention, the fibrous strip comprises on each second lateral portion, an alternation of layers of the first set and layers of the second set.

[0023] Another object of the invention is a fibrous preform comprising a fibrous strip according to the invention, shaped, having an H-shaped cross-section, the second lateral portions being folded along the unbinding zone and the first lateral portions deployed transversely to this zone so as to form the branches of the H, the second intermediate portion connecting the branches of the H.

[0024] This allows the formation of a fibrous H-shaped core preform whose strand layers are more easily oriented towards the H-shape. This helps to limit the spacing between the branches of the H.

[0025] According to one embodiment of the invention, the fibrous preform comprises at least one first U-shaped textile counterform placed opposite the unbinding zone and the first lateral portions and formed by three-dimensional weaving by linking third yarns with fourth yarns, the third yarns extending transversely to the longitudinal axis, said at least one first counterform comprising the same number of layers of third yarns as the first set has layers of first yarns plus or minus one layer.

[0026] According to another embodiment of the invention, the fibrous preform comprises a first U-shaped textile counterform placed opposite the unbinding zone and the first lateral portions, and a second U-shaped textile counterform placed opposite the unbinding zone and the second lateral portions, each of the first and second counterforms being formed by three-dimensional weaving by bonding third yarns with fourth yarns, the third yarns extending transversely to the longitudinal axis, the second counterform having the same number of layers of third yarns as the first counterform, and the set of the first and second counterforms having the same number of layers of third yarns as the first set has layers of first yarns plus or minus one layer.

[0027] The presence of counterforms helps to reduce stress concentration in areas located on the edges of the unbonding zone, and to balance the thicknesses between the parts located above and below the unbonding zone.

[0028] In this case, the fiber preform may include a compensation preform comprising a set of yarn layers present on each lateral edge of the fiber strip. The compensation preform makes it possible to maintain the same number of yarn layers or strands between the lateral portions of the first and second zones of the fiber strip.

[0029] Yet another object of the invention is an assembly comprising a fibrous preform according to the invention, a woven fibrous belt texture positioned on the first lateral portions of said fibrous preform so as to define a loop around it, the belt texture thus positioned defining on each longitudinal end of the unbinding zone, with the first lateral portions, distinct cap preforms.

[0030] The whole thus forms a core-belt type preform, the belt of which ensures the absorption of tensile forces.

[0031] Yet another object of the invention is a part made of composite material comprising an assembly according to the invention and an organic matrix formed in a porosity of the assembly.

[0032] According to a particular feature of the invention, the part forms a landing gear strut, part of a landing gear strut or a brake bar.

[0033] Brief description of the drawings

[0034] Other features and advantages of the present invention will become apparent from the description given below, with reference to the attached drawings which illustrate examples of embodiment without any limiting character.

[0035] [Fig. 1] Figure 1 represents, schematically and partially in top view, an example of a fibrous band.

[0036] [Fig. 2] Figure 2 represents, schematically and partially, a cross-section of the fibrous band of Figure 1 taken along plane II-II.

[0037] [Fig. 3] Figure 3 schematically and partially represents a cross-section of a fibrous strip according to one embodiment of the invention. [Fig. 4] Figure 4 schematically and partially represents a cross-section of a fibrous strip according to another embodiment of the invention.

[0038] [Fig. 5] Figure 5 schematically and partially represents a cross-section of a fibrous strip according to another embodiment of the invention.

[0039] [Fig. 6] Figure 6 represents, schematically and partially, the shaping of the fibrous strip of the invention.

[0040] [Fig. 7] Figure 7 represents, schematically and partially, the shaping of the fibrous strip of the invention at the level of another cross-section taken according to IV-IV.

[0041] [Fig. 8] Figure 8 represents, schematically and partially, the shaping of the fibrous strip of the invention at the level of another cross-section taken along VV.

[0042] [Fig. 9] Figure 9 schematically and partially represents a cross-section of a fibrous preform comprising a counterform and a fibrous strip according to an embodiment of the invention.

[0043] [Fig. 10] Figure 10 schematically and partially represents a cross-section of a fibrous preform comprising two counterforms and a fibrous strip according to another embodiment of the invention.

[0044] [Fig. 11] Figure 11 represents, schematically and partially, a side view of an example of a preform of a part made with a fibrous strip of the invention.

[0045] Description of the implementation methods

[0046] The invention is now described by means of figures, which are provided for descriptive purposes to illustrate certain embodiments of the invention, and which should not be interpreted as limiting the latter.

[0047] Figures 1 and 2 show, respectively in top view and cross-section, an example of a fibrous strip 10 usable within the scope of the invention. The strip 10 has a slender shape and extends along a longitudinal axis X between two longitudinal ends EB. The strip 10 is laterally delimited by lateral edges BL. The lateral edges BL delimit the strip 10 along the lateral direction L. Each lateral edge BL extends along the X-axis. The width of the strip 10 corresponds to the distance between the lateral edges BL. Unless otherwise specified, the widths are measured in cross-section, or even perpendicular, to the X-axis along the L-direction.

[0048] The strip 10, as shown, can have a virtually constant width along its entire length. The thickness direction is represented by the axis E visible in Figure 2. The thickness of the strip 10 corresponds to its smallest dimension.

[0049] The band 10 is obtained by three-dimensional weaving in a single piece (monobloc) with a debonding zone 20. The band 10 comprises first yarns, oriented along the X-axis, which are woven with second yarns oriented along the L-axis. The first yarns can be warp yarns and the second yarns weft yarns, or vice versa. "Three-dimensional weaving" or "3D weaving" refers to a weaving method in which at least some of the first yarns interlace second yarns over several layers of second yarns. Such a weave can be produced on a Jacquard loom in a manner known per se. For example, but not limited to, an interlock weave can be used for the band 10.

[0050] Figure 2 represents the band 10 taken in cross-section, for example perpendicular to the X axis. It is understood that a similar structure is found over the entire length of the band 10 by varying the width of the unbundling zone 20.

[0051] The debonding zone 20 extends along the X-axis, here along the entire length of the strip 10 from one end EB to the other. The debonding zone 20 extends over only a portion of the width of the strip 10. The debonding zone 20 is separated from each of the lateral edges BL. It can extend in a plane containing the X-axis and the direction L. It is located inside the strip 10 and only extends outside the strip 10 at the ends EB. The debonding zone 20 is laterally bounded by two edges 20a. The profile of the edges 20a determines the geometry of the core preform after shaping, as will be detailed below. In the illustrated example, the edges 20a form an angle α, for example, less than or equal to 10°. In the illustrated example, each of the edges 20a has a straight line shape, so the angle a is unchanged along the X axis. However, we do not depart from the scope of the invention when it is otherwise as mentioned below.The edges 20a are each spaced from the lateral edges BL. Each edge 20a is located on the side of a respective lateral edge BL.

[0052] The unlinking zone 20 defines a first woven region 11 which is superimposed on a second woven region 12. In the unlinking zone 20, layers of yarns from the first 11 and second 12 regions have been intentionally omitted from being woven together, so as to be able to shape the fibrous strip 10, as will be described below.

[0053] The first region 11 can be separated from the second region 12 due to the presence of the debonding zone 20. The debonding zone 20 is located between the first 11 and second 12 regions. The first 11 and second 12 regions are offset along the E direction. Each of the first 11 and second 12 regions extends across the entire width of the band 10 from one lateral edge BL to the other.

[0054] The first region li has a first thickness in which is greater than a second thickness ei2 of the second region 12. The thicknesses are measured along the direction E.

[0055] In this example, the first thickness en is greater than the second thickness en, however, we can also have en = ei2 ; or even en different from ei2 where the second thickness ei2 is greater than the first thickness en.

[0056] More specifically, the first region 11 comprises lateral first portions lia, each located on the side of a respective lateral edge. Each first portion lia is laterally delimited by a lateral edge BL. The first portions lia are obtained by three-dimensional weaving. The first portions lia are textile-linked by an intermediate portion 11b, which is intended to be cut during the shaping of the strip 10, as explained below. When moving through the first region 11 from one lateral edge BL to another, one passes successively through a first portion lia, through portion 11b, and then again through a first portion lia. Portion 11b may not be woven to facilitate its subsequent cutting (shown in Figure 3A), and may consist only of second yarns that link the first portions lia.Alternatively, portion 11b is woven and includes, for example, first yarns distinct from the first yarns used in the rest of band 10. Thus, band 10 can generally be made of carbon yarns but with a portion 11b made of polymeric first yarns, for example polyester, which are less expensive than carbon yarns.

[0057] The second region 12 comprises lateral second portions 12a, each located on the side of a respective edge BL. Each second portion 12a is laterally delimited by an edge BL. The second portions 12a are obtained by three-dimensional weaving. The second region 12 further comprises an intermediate second portion 12b that textileally connects the second portions 12a. The second portion 12b can be obtained by three-dimensional weaving. Alternatively, the second portion 12b can be formed solely by unidirectional layers of second yarns connecting the two woven portions 12a. The second portion 12b extends across the entire width of zone 20. Each second portion 12a extends between an edge 20a and an edge BL. The second portions 12a are woven with the first portions 11a and are overlapped with a first part thereof.A second part of the first portions lia, different from the first part, is superimposed on the second portion 12b. The thickness of the first part of the first portions lia is greater than the thickness of the second portions 12a.

[0058] Figures 3, 4, and 5 show examples of the distribution of first yarn layers in the first 11 and second 12 regions of strip 10. Due to the symmetry of strip 10 and the two regions 11 and 12, only a portion of strip 10 in cross-section is shown in Figures 3, 4, and 5. Figures 3A, 4A, and 5A specifically depict strip 10 before forming, and Figures 3B, 4B, and 5B depict strip 10 after forming, according to the forming process described below with reference to Figures 6, 7, and 8.

[0059] According to the invention, and as shown in Figures 3, 4 and 5, the first yarns comprise a first set 412, 424, 434 of first yarn layers extending into the second region 12, and a second set 413, 423, 433 of first yarn layers extending into the first region 11 covering the unbinding zone 20. In Figure 3, the first set 412 is more particularly formed of two sets of layers 414, 415.

[0060] The second set 413, 423, 433 crosses the first set 412, 424, 434 in a crossing zone 30 adjacent to each edge 20a of the unbinding zone 20, such that the first wire layers of the second set 413, 423, 433 extend into the second lateral portions 12a of the second region 12. The layers of the second set 413, 423, 433 penetrate or cross, for example, at least 2 layers of the first set 412, 424, 434. The first wires of the second set 413, 423, 433 can be positioned at different heights in the second lateral portions 12a, in other words, can penetrate more or less deeply into the thickness of the second lateral portions 12a. Similarly, the first wires of the first set 412, 424, 434 can be positioned at different heights in the first lateral portions lia.

[0061] The crossover between the first 412, 424, 434 and the second 413, 423, 433 sets can be done in different ways.

[0062] For example, in figures 3, 4 and 5, consecutive layers of the second set 413, 423, 433 cross, on the crossing zones 30, consecutive layers 414 of the first set 412, 424, 434.

[0063] We can have a distribution of the layers of the first 412, 424, 434 and second 413, 423, 433 sets by blocks (figures 3 and 5) or in alternation (figure 4).

[0064] Indeed, in Figures 3 and 5 and on each second lateral portion 12a of the band 10, a first group or block 414 of consecutive layers of the first set 412, 434 is offset along the thickness direction of a second group or block of consecutive layers of the second set 413, 433. More particularly, in Figure 3, the second group of the second set 413 is intercalated between the first group 414 and a third group 415 of layers of first yarns of the first set 412 extending into the second region 12. The second group 413 can extend in this way into the second region 12 so as to penetrate at least two layers of the thickness ei2 of the second region 12.

[0065] Regarding the alternation shown in Figure 4, on each second lateral portion 12a of the band 10, there is an alternation 450 of layers of the first set 424 and layers of the second set 423.

[0066] It is also possible to consider a combination of the embodiments of Figures 3 and 4, having for example N layers in the first set, where M layers are alternated with the second set and the remaining NM layers (equivalent to the layers of the third group 415 of the first set of Figure 3) remain in the first set, with N greater than or equal to 3 and M strictly less than N.

[0067] Regardless of the type of crossover between the layers of the first 412, 424, 434 and second 413, 423, 433 sets, the first set 412, 424, 434 can include between 2 and 32 layers, for example between 2 and 10 layers, for example 8 layers.

[0068] Regardless of the type of crossover between the layers of the first 412, 424, 434 and second 413, 423, 433 sets, the second 413, 423, 433 set can comprise between 2 and 32 layers, for example, between 2 and 6 layers, or 4 layers. Limiting the number of layers to 4 allows for better management of yarn length variations that can occur during strip forming (particularly during folding), and thus reduces local strand buckling.

[0069] The shaping of strip 10, so as to have an H-shaped cross-section, is now described; this shaping allows us to obtain the examples illustrated in Figures 3B, 4B, and 5B. This shaping is described more specifically with reference to Figure 6, Figure 6A representing the cutting of the first intermediate region 11c, and then Figures 6B and 6C representing the shaping of strip 10 after this cutting.

[0070] The shaping is carried out in a shaping tooling (not shown) to the shape of the core of the part to be obtained.

[0071] The shaping process involves the outward deployment of the first lia portions, indicated by arrows D in Figure 6B, during which the lateral edges BL1 are moved apart. The lateral edges BL1 are also moved away from the second portion 12b during deployment. During deployment, the first lia portions are moved away from a median plane P of the band 10. This plane P may be a plane of symmetry of the band 10. The first lia portions are deployed so as to be positioned transversely, or even substantially perpendicularly, to the unbundling zone 20. The deployment of the first lia portions leads to an increase in the width of the zone 11c.

[0072] The shaping process also includes folding the second portions 12a inwards along the edges 20a. This fold is indicated by the arrows PL in Figure 6B. The second portions 12a are folded towards each other and in the direction of plane P. The second portions 12a are folded so that they are positioned transversely, or even substantially perpendicularly, to the unbinding zone 20. The second portions 12a are folded, and the first portions 1a are straightened along the edges 20a. The unfolding of the portions 1a and the folding of the portions 12a are carried out simultaneously because these portions are woven together.

[0073] After forming, a core preform 40 is obtained with an H-shaped cross-section, as illustrated in Figure 6C. The first deployed portions 30 form the lateral arms of the H and define, on their upper and lower parts, a positioning surface 32 for the belt texture. Due to the variation in width of the debonding zone 20 along the X-axis, the first deployed portions 30 form the angle α described above, which allows for a flared geometry for the part and, in particular, distinct spacings between the clevises at each end EB. The orientation of the first wires along the X-axis in the first deployed portions 30 ensures that these portions can withstand the compressive forces during operation.The second portion 12b forms the junction zone between the first deployed portions 30, which ensures the geometry between them and contributes to the buckling resistance of the part.

[0074] One consequence of the shaping described above is that the second intermediate portion 12b, in the core preform, is at a different height h on either side of the part (as shown in Figures 7 and 8). The variation in height h reflects the proximity or separation of the first deployed portions 30. Bringing these branches closer together can be advantageous to limit the amount of material removed from the first intermediate portion 11b. Alternatively, separating them can be advantageous if space is desired in the lower part of the preform, for example, to accommodate equipment.

[0075] Figures 9 and 10 represent a fibrous preform 100 obtained from the fibrous strip according to the invention, comprising at least one counterform. Indeed, after obtaining the core preform, one or more counterforms 60, 71, 72 can be positioned opposite the unbonding zone 20 and the first and / or second lateral portions to obtain better mechanical strength and a balanced number of layers in the upper and lower parts of the arms of the H formed by the fibrous preform 100.

[0076] Counterforms 60, 71, 72 are textile counterforms, for example 3D woven counterforms. They are each formed by three-dimensional weaving by linking third threads with fourth threads, the third threads extending transversely to the longitudinal axis X.

[0077] As shown in Figures 3, 4 and 5, only part of the preform 100 is shown in Figures 9 and 10, due to its symmetry.

[0078] In Figures 9 and 10, the preform 100 comprises a first set 444, 454 of consecutive layers of first wires extending into the second region 12 and a second set 443, 453 of consecutive layers of first wires extending into the first region 11 and crossing the first set 444, 454 in the crossing zone 30 so as to extend into the second lateral portion 12a. In particular, the layers of the first set 444, 454 are offset along the thickness of the layers of the second set 443, 453.

[0079] In Figure 9, a U-shaped counterform 60 is positioned opposite the unbinding zone 20 and the first lateral portions lia. The counterform 60 comprises the same number of third-wire layers as the first set 444 has layers of first-wire layers, plus or minus one layer. This maintains a constant thickness in the arms of the H formed by the preform 100.

[0080] In Figure 10, two U-shaped counterforms 71 and 72 are shown. Specifically, counterform 71 is positioned opposite the debonding zone 20 and the first lateral portions 1a; and counterform 72 is positioned opposite the debonding zone 20 and the second lateral portions 12a. Both counterforms 71 and 72 have the same number of layers, and more specifically, their number of third-wire layers is equal to half the number of first-wire layers of the first set 454 plus or minus one. In other words, the sum of the number of third-wire layers of the first 71 and second 72 counterforms is equal to the number of first-wire layers plus or minus one of the first set 454.

[0081] Furthermore, in the case of Figure 10, the presence of the counterform 72 adds additional layers of wires in the second lateral portions 12a. In order to maintain the same number of wire layers between the two regions 11 and 12, a compensating preform 73 can thus be added to the first lateral portions 1a of the first region 11.

[0082] The advantage of having two counterforms 71, 72 instead of one allows us to obtain a symmetry between the upper and lower parts of the H formed by the preform.

[0083] The counterform(s) described may also be present with a preform obtained from a fibrous strip whose first and second sets are arranged according to the examples in figures 3 and 4.

[0084] To fill the space 610, 710, 720 between the counterforms 60, 71, 72 and the first and second lateral portions 12a, a filling material can be placed in these spaces 610, 710, 720. The filling material can be fibrous, for example, braided fibers. This prevents the spaces or zones 610, 710, 720 from being filled with resin during the formation of a matrix in the porosity of the fibrous preform 100, the matrix being formed by resin infiltration, as described below.

[0085] Figure 11 shows the preform 40 of the core in lateral view obtained following the forming process described above. To obtain the shape illustrated in Figure 11, the first unfolded portions 30 were machined at their ends EB to give them the desired shape, here a curved shape, for example, substantially circular. The ends of the second portion 12b were also cut to be recessed relative to the ends EB. However, the process does not depart from the scope of the invention if the forming process does not include this machining.

[0086] At a given end EB, the first deployed portions 30 each define a part 50 of a respective cap preform; that is, a first deployed portion 30 defines a part of a preform of a first cap, and a second deployed portion 30, different from the first deployed portion, defines a part of a preform of a second cap, different from the first cap. The woven belt texture 60 is then positioned on the deployed lateral portions 30 so as to define a loop around the preform 40. The texture 60 has a band shape that is wrapped around the preform 40. The texture 60 is positioned on the surface 32, resting on the arms 30. The texture 60, thus positioned, together with the deployed lateral portions 30, defines, at each end EB, distinct cap preforms 70. Each preform 70 defines 55 free spaces intended for articulation with other parts.Texture 60 ensures tensile strength. After positioning texture 60, the preform 80 of the desired part is obtained. Texture 60 can also be obtained by three-dimensional weaving, for example with an interlock weave.

[0087] The 60 belt texture and the 40 core preform can be made from carbon fibers.

[0088] The preform 80 may have a different spacing from the end cap preforms 70 EB. This spacing also corresponds to the spacing between the deployed lateral portions 30. A counter-mold is then positioned around the preform 80 to define a cavity for introducing the matrix material, and the assembly is 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 results in a composite part intended 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 may have an organic matrix.

[0089] The part may or may not be intended for an aeronautical application. For example, it could be a connecting rod, a landing gear strut or component thereof, or 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 a pivot pin through the gaps 55 for connection to other parts, along with a contact insert for this pin.

[0090] We have just described an example in which the edges 20a each have a straight line shape, but this does not depart from the scope of the invention if the situation is otherwise. The examples just described concern a preform concept for a part of the "core-belt" type. However, the invention is not limited to this solution.

[0091] The expression "between ... and ..." should be understood as including the boundaries.

Claims

Demands

1. A fibrous preform comprising a one-piece fibrous strip (10) formed by three-dimensional weaving by bonding first yarns with second yarns, the fibrous strip having a slender shape along a longitudinal axis (X) and comprising a debonding zone (20) extending along the longitudinal axis between lateral edges (BL) of the fibrous strip and defining a first region (11) superimposed on a second region (12) that can be separated from the first region, the debonding zone being present between the first and second regions, the first region comprising first lateral portions (11a) woven together by a first intermediate portion (11b), and the second region comprising second lateral portions (12a) connected by a second intermediate portion (12b) and woven together with the first lateral portions,the first fibers extending transversely to the longitudinal axis (X) and comprising a first set (412, 424, 434, 444, 454) of first fiber layers extending into the second region and a second set (413, 423, 433, 443, 453) of first fiber layers extending into the first region, covering the unbonding zone, the second set (413, 423, 433, 443, 453) crossing, in a crossing zone (30) adjacent to each edge (20a) of the unbonding zone, the first set (412, 424, 434, 444, 454) so ​​as to extend into the second lateral portions, the fibrous preform being shaped, and having an H-shaped cross-section, the second lateral portions being folded along the detachment zone and the first lateral portions deployed transversely to this zone so as to form the branches of the H, the second intermediate portion connecting the branches of the H.

2. A fibrous preform according to claim 1, wherein consecutive layers of the second set (413, 423, 433, 443, 453) intersect, on each crossing zone (30), consecutive layers (414) of the first set (412, 424, 434, 444, 454).

3. A fibrous preform according to any one of claims 1 or 2, wherein, on each second lateral portion (12a), a first group (414) of consecutive layers of the first set (412, 434, 444, 454) is offset along the thickness direction by a second group of consecutive layers of the second set (413, 433, 443, 453).

4. Fibrous preform according to claim 3, wherein the second group (413) is intercalated, on each second lateral portion (12a), between the first group (414) and a third group (415) of first yarn layers extending into the second region (12).

5. Fibrous preform according to any one of claims 1 or 2, comprising on each second lateral portion (12a), an alternation (450) of layers of the first set (424) and layers of the second set (423).

6. Fibrous preform according to any one of claims 1 to 5 comprising at least a first U-shaped textile counterform (60), positioned opposite the unbinding zone and the first lateral portions and formed by three-dimensional weaving by bonding third yarns with fourth yarns, the third yarns extending transversely to the longitudinal axis (X), and said at least a first counterform comprising the same number of layers of third yarns as the first set has layers of first yarns, plus or minus one layer.

7. A fibrous preform according to any one of claims 1 to 5, comprising a first U-shaped textile counterform (71) positioned opposite the unbinding zone and the first lateral portions (1a), and a second U-shaped textile counterform (72) positioned opposite the unbinding zone (20) and the second lateral portions (12a), each of the first and second counterforms being formed by three-dimensional weaving by bonding third yarns with fourth yarns, the third yarns extending transversely to the longitudinal axis (X), the second counterform having the same number of third yarn layers as the first counterform, the set of the first and second counterforms having the same number of third yarn layers as the first set has of first yarn layers plus or minus one layer.

8. Fibrous preform according to claim 7, comprising a compensation preform (73) comprising a set of yarn layers present on each lateral edge of the fibrous band.

9. Assembly (80) comprising a fibrous preform (40) according to any one of claims 1 to 8 and a woven fibrous belt texture (60) positioned on the first lateral portions (30) of said fibrous preform so as to define a loop around it, the belt texture so positioned defining on each longitudinal end (EB) of the unbinding zone, with the first lateral portions, distinct cap preforms (70).

10. Composite material part comprising an assembly according to claim 9 and an organic matrix formed in a porosity of the assembly.

11. A part made of composite material according to claim 10, forming a landing gear strut, part of a landing gear strut or a brake bar.

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