Method for manufacturing a fibrous preform for a composite part intended to be articulated with other parts

Abstract

The present invention relates to a method for manufacturing a fibrous preform of a core for a composite part intended to be articulated with other parts, comprising forming a one-piece strip by three-dimensional weaving, shaping said strip to give it a generally H-shaped cross-section, and positioning a reinforcing counter-form with rounded corners in order to reduce local stress concentrations when the part is under load.

Description

Description Title of the invention: Method for manufacturing a fibrous preform for a composite part intended to be articulated with other parts Technical Field

[0001] This presentation concerns the manufacture of a composite part intended to be articulated with other parts at its ends, in particular the manufacture of a fibrous preform of a core of such a part. Previous technique

[0002] The use of composite materials as a replacement for metallic materials can be proposed with a view to reducing weight, which is a constant concern in the particular case of aircraft parts.

[0003] In this view, US patent 7704429 proposed manufacturing landing gear struts from composite material that include regions, called cleats, intended for articulation and load transfer with other parts. These cleats are formed by a laminated structure with intercalated plies between primary plies extending the body of the reinforcement. However, this solution may have drawbacks. Indeed, the cleats, which have a laminated configuration, can lead to an increase in the size of the load transfer areas compared to the metal parts in order to avoid the risk of delamination. The overall system weight reduction then becomes less significant, and the integration of the part becomes more challenging due to the increased size. 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 mid-section 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 mass and therefore does not provide complete satisfaction. WO2010146288 discloses a turbine distributor element made of CMC, FR2983428 discloses a manufacturing process for a turbomachine blade including integrated platforms, FR3116753 discloses a manufacturing process for a composite blade with integrated platforms and mounting brackets, and W02014076408 discloses a preform for a one-piece blade for a turbomachine.We also know of US2011293828 which describes a process for manufacturing a part of complex shape made of composite material, and WO 2025 / 052061 which describes a process for manufacturing a fibrous preform of a part of composite material intended to be articulated to other parts.

[0004] The invention proposes to address all or part of the aforementioned drawbacks. Description of the invention

[0005] The present invention relates, according to a first aspect, to a method for manufacturing a fibrous preform of a core for a composite part intended to be articulated with other parts, the method comprising: - the formation by three-dimensional weaving of a single-piece fibrous strip having a slender shape along a longitudinal axis and comprising a debonding zone extending along the longitudinal axis and spaced from each of the lateral edges of the strip, the debonding zone defining a first region superimposed on a second region and which can be separated from the latter, the first region comprising first woven lateral portions connected by a first intermediate portion, and the second region comprising second lateral portions, connected by a second intermediate portion, woven with the first lateral portions, the first region optionally having a thickness greater than or equal to that of the second region, - cutting the first intermediate portion so as to separate the first lateral portions, - the shaping of the strip, after cutting the first intermediate portion, including the unfolding of the first lateral portions transversely to the unbundling zone, and the folding of the second lateral portions along the edges of the unbundling zone so as to give the strip thus shaped an H-shaped cross-section, each of the first unfolded lateral portions defining a part of a respective sash preform on each longitudinal end of the strip, the strip thus shaped defining an intersection zone between the second intermediate portion and each first unfolded lateral portion, and - the positioning of a counterform of reinforcement, textile or metallic, on the unbundling zone of the strip thus formed, said counterform comprising an intermediate part positioned on the unbundling zone and a corner on each side of the intermediate part, each corner covering a respective intersection zone and having a rounded shape in cross-section.

[0006] The invention thus proposes the manufacture of a core preform adapted to obtaining a composite part having two flanges at each longitudinal end. The invention allows, if desired, the formation of an evolving spacing between the lateral arms of the H, which are formed by the first deployed portions, by modifying the local width of the bond zone to obtain, in particular, a different spacing between the flanges at the ends.

[0007] The invention offers the advantage of producing a single-piece fabric strip (monobloc) to avoid handling that can cause defects during manufacturing, and also to reduce the interfaces between multiple preforms, which are a source of mechanical weakness. The use of a weaving technique also ensures the presence of threads extending from one longitudinal end to the other along the arms of the H-shaped structure to withstand the desired compressive forces. The second region forms a horizontal junction between these arms, which guarantees the overall strength of the part, particularly against buckling, and resists the separation of the flanges when the part is subjected to tensile or compressive loads.Furthermore, the addition of the reinforcing counterform with rounded corners reduces local stress concentrations in intersection areas during part loading, leading to increased part life due to better stress distribution around the unbonding zone. The final web shape is generated after strip forming and counterform positioning.

[0008] In one embodiment, each corner of the counterform is extended by a connecting edge which rests on a first deployed lateral portion and extends over at least half the height of this first portion measured from the uncoupling zone.

[0009] Such a feature advantageously allows for further limiting of the separation of the first lateral portions deployed under load due to increased support of the lateral portions by the connecting edges in the part.

[0010] In particular, each connecting edge can bear on at least 75%, or even substantially all, of the height of the corresponding first deployed lateral portion.

[0011] In one example implementation, a filler material is introduced between each corner and the corresponding intersection area.

[0012] In one example of implementation, the counter-form reinforcement is textile and obtained by three-dimensional weaving.

[0013] The invention also relates to a method for manufacturing a fibrous preform of a composite part intended to be articulated with other parts, comprising: - the manufacture of the fibrous core preform by implementing a process as described above, and - the positioning of a woven fibrous belt texture on the first deployed lateral portions of the core preform so as to define a loop around it, the belt texture thus positioned defining on each longitudinal end, with the first deployed lateral portions, distinct cap preforms.

[0014] This forms a core-belt type preform, the belt of which ensures the absorption of tensile forces.

[0015] In one embodiment example, the fibrous core preform and the belt texture are made of carbon fibers.

[0016] The invention is not, however, limited to the production of a "core-belt" type preform. Thus, the invention also relates, in a second aspect, to a method for manufacturing a fibrous preform of a composite part intended to be articulated with other parts, comprising: - the formation by three-dimensional weaving of a single-piece fibrous strip having a slender shape along a longitudinal axis and comprising a debinding zone extending along the longitudinal axis and spaced from each of the lateral edges of the strip, the debinding zone defining a first region superimposed on a second region and which can be separated from the latter, the first region comprising first woven lateral portions connected by a first intermediate portion, and the second region comprising second lateral portions, connected by a second intermediate portion, woven with the first lateral portions, the first region optionally having a thickness greater than or equal to that of the second region, - cutting the first intermediate portion so as to separate the first lateral portions, and - the shaping of the strip, after cutting the first intermediate portion, including the deployment of the first lateral portions transversely to the unbundling zone, and the folding of the second lateral portions along the edges of the unbundling zone so as to give the strip thus shaped an H-shaped cross-section, the strip thus shaped defining an intersection zone between the second intermediate portion and each first deployed lateral portion, and - the positioning of a reinforcing counterform, textile or metallic, on the unbundling zone of the strip thus shaped, said counterform comprising an intermediate part positioned on the unbundling zone and a corner on each side of the intermediate part, each corner covering a respective intersection zone and having a rounded shape in cross-section, Each of the first deployed lateral portions being machined and drilled so as to define a respective cleat preform on each longitudinal end of the strip, the machining and drilling being carried out on the formed strip, before or after the positioning of the counterform.

[0017] This case concerns the production of machined screeds during the shaping of the strip.

[0018] The invention also relates to a method for manufacturing a part made of composite material intended to be articulated with other parts, comprising at least: - the manufacture of the fibrous preform of the part by implementing a process such as that described above, and - the formation of a matrix in a porosity of the fibrous preform thus obtained.

[0019] In one example of implementation, the matrix is ​​organic.

[0020] In one embodiment example, the part is a landing gear strut, part of a landing gear strut, or a brake bar. Brief description of the drawings [Fig. 1] Figure 1 represents, schematically and partially in top view, an example of a fibrous tape usable within the framework of the invention. [Fig. 2] Figure 2 represents, schematically and partially, a cross-section of the strip of figure 1 taken along II-II. [Fig. 3] Figure 3 represents, schematically and partially, the shaping of the strip in Figure 1. [Fig. 4] Figure 4 represents, schematically and partially, the shaping of the band of figure 1 at the level of another cross-section taken along IV-IV. [Fig. 5] Figure 5 represents, schematically and partially, the shaping of the band of figure 1 at the level of another cross-section taken along VV. [Fig. 6] Figure 6 represents, schematically and partially, a cross-section of the strip in Figure 1, shaped and annotated with different geometric parameters. [Fig. 7] Figure 7 schematically and partially represents the positioning of a reinforcing counterform on the formed strip. [Fig. 8] Figure 8 schematically and partially represents a detail of a variant in which a filling material is introduced between the corners of the counterform and the intersection areas. [Fig. 9] Figure 9 represents, schematically and partially, a side view of an example of a preform of a part according to the invention. [Fig. 10] Figure 10 represents, schematically and partially, a top view of the preform of Figure 9. [Fig. 11] Figure 11 represents, schematically and partially in top view, another example of fibrous tape usable within the framework of the invention. [Fig. 12] Figure 12 represents, schematically and partially, a side view of another example of a part preform within the scope of the invention. [Fig. 13] Figure 13 represents, schematically and partially, a side view of another example of a part preform within the scope of the invention. Description of the implementation methods

[0021] 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.

[0022] Figures 1 and 2 illustrate, 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. Unless otherwise specified, a cross-section is taken transversely, for example, perpendicularly, to the X-axis. The strip 10 is laterally delimited by lateral edges BL. The edges BL delimit the strip 10 along the lateral direction L. Each edge BL extends along the X-axis. The width of the strip 10 corresponds to the distance between the edges BL. Unless otherwise specified, the widths are measured in cross-section with respect to the X-axis along the L-direction. The strip 10 can, as illustrated, have a substantially constant width along its entire length. The thickness direction is defined by the axis E (see Figure 2).The thickness of the band 10 corresponds to its smallest dimension.

[0023] Band 10 is obtained by three-dimensional weaving in a single piece (monobloc) with a debonding zone, as will be detailed later. 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 band 10.

[0024] Figure 2 represents a cross-section of the band 10 taken transversely, for example perpendicularly, 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.

[0025] The band 10 has a debonding zone 20 that extends along the X-axis, here along the entire length of the band 10 from one end EB to the other. The zone 20 extends over only a portion of the width of the band 10. The zone 20 is spaced from each of the edges BL. The zone 20 can extend in a plane containing the X-axis and the direction L. The zone 20 is located inside the band 10 and only extends outside the band at the ends EB. The zone 20 is laterally bounded by two edges 20a. The profile of the edges 20a determines the geometry of the web preform after shaping, as will be detailed below. In the illustrated example, the edges 20a form a non-zero 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 edges BL. Each edge 20a is located on the side of a respective edge BL.

[0026] Zone 20 defines a first woven region 11, which is superimposed on a second woven region 12. Within zone 20, layers of yarn from the first 11 and second 12 regions have been intentionally omitted to allow for the shaping process described later. The first region 11 can be separated from the second region 12 due to the presence of zone 20. 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 edge BL to the other. The first region 11 may have a first thickness α that is greater than a second thickness ε2 of the second region 12. The thicknesses are measured along the E direction.

[0027] More specifically, the first region 11 comprises lateral first lia portions, each located on the side of a respective BL edge. Each first lia portion is laterally delimited by a BL edge. The first lia portions are obtained by three-dimensional weaving. The first lia portions are textile-linked by an intermediate portion 11b, which is intended to be cut later in the process as detailed below. When moving through the first region 11 from one BL edge to another, one passes successively through a first lia portion, through portion 11b, and then through another first lia portion. Portion 11b may be unwoven to facilitate its subsequent cutting and may consist only of second yarns that link the first lia portions. Alternatively, portion 11b is woven and may, for example, include first yarns distinct from the first yarns used in the rest of the band 10.Thus, band 10 can generally be formed of carbon fibers but with a portion 11b formed of first polymeric fibers, for example polyester which are less expensive than carbon fibers.

[0028] 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. 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 lia and are superimposed 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 may be greater than the thickness of the second portions 12a.

[0029] Once strip 10 is obtained, the manufacturing of the core preform continues as illustrated in figure 3.

[0030] The first portion 11b is initially cut using known methods. The first portion 11b is cut along its entire length or along the entire length of the strip 10. This creates a zone 11c of material deficiency between the first portions lia (see drawing 3A). Zone 11c is located between two inner edges BL1 of the first portions lia. The first portions lia are separated following this cut and can be deployed independently of each other.

[0031] The process continues with the shaping of the strip, after this cutting, as illustrated in drawings 3B and 3C.

[0032] The shaping is carried out in a shaping tooling (not shown) to the shape of the core of the part to be obtained.

[0033] The shaping process involves the outward deployment of the first lia portions, indicated by arrows D in Figure 3B, during which the edges BL1 are moved apart. The 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 band 10. Plane P may be a plane of symmetry of band 10. The first lia portions are deployed so as to be positioned transversely, or even substantially perpendicularly, to zone 20. The deployment of the first lia portions leads to an increase in the width of zone 11c.

[0034] The shaping process also includes folding the second sections 12a inwards along the edges 20a. This fold is indicated by the arrows PL in drawing 3B. The second sections 12a are folded towards each other and in the direction of plane P. The second sections 12a are folded so that they are positioned transversely, or even substantially perpendicularly, to area 20. The second sections 12a are folded, and the first sections 1a are straightened along the edges 20a. The unfolding of the sections 1a and the folding of the sections 12a are carried out simultaneously because these sections are woven together.

[0035] After shaping, a shaped strip 40 is obtained with an H-shaped cross-section, as illustrated in drawing 3C. The first unfolded 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. The shaped strip 40 defines an intersection zone ZI between the second portion 12b and each first unfolded portion 1a. Each ZI zone is located at a distinct edge 20a. Due to the variation in width of zone 20 along the X-axis, the first unfolded portions 30 form the angle α described above, which allows for a flared geometry for the part and, in particular, distinct spacing between the cleats at each end EB.Such a configuration with distinct spacing can offer various advantages depending on the application, including: the ability to limit the amount of material removed from the first intermediate section by reducing the width of the bond zone, or the possibility of housing equipment between the cleats by spacing them apart. The orientation of the first wires along the X-axis in the first 30 deployed sections ensures that they withstand the compressive forces during operation. The second section 12b forms the junction zone between the first 30 deployed sections, which maintains the geometry between them and contributes to the buckling resistance of the part.

[0036] One consequence of the described solution is that the second portion 12b, within the formed strip, is at a different height h on one side of the part than the other (see Figures 4 and 5). Figure 6 illustrates the relevant geometric parameters for determining the height h of the second portion 12b. The value of h is defined such that the length L1 remains constant over the entire part, regardless of variations in RI, el, or DI:

[0037] [Math. 1] >

[0038] with in the formula above: el = thickness of portion 12b which may be variable (see figure 12), RI = internal radius of the formed strip, generally taken to be approximately equal to el to ensure good radius forming, and L1 = length of the curve illustrated in bold at the altitude of the unbinding in the preform.

[0039] The variation in altitude h reflects the approach or separation of the first 30 deployed sections. Bringing these branches closer together may be advantageous to limit the amount of material removed in section 11b. Alternatively, it may be advantageous to remove them if you wish to have space in the lower part of the preform (to house equipment, for example).

[0040] The process continues with the positioning of the reinforcing counterform 100 onto the formed strip. As mentioned above, the counterform 100 can be made of textile, for example, obtained by three-dimensional weaving using a known method. Alternatively, the counterform 100 can be metallic, for example, made of titanium or titanium alloy, or even stainless steel. These materials have the advantage of resisting galvanic corrosion in contact with carbon fibers. Generally, the counterform 100 can be monobloc (a single piece).

[0041] The counterform 100 includes an intermediate portion 101 which is positioned on the zone 20, or on the second portion 12b. The portion 101 can be superimposed on the zone 20, or on the second portion 12b. In the example considered here, the relative difference between the thickness el11 of the portion 101 and the thickness el2b of the second portion 12b does not exceed 10%. In particular, the thickness el2b can be substantially equal to the thickness el11. Such symmetry between the counterform and the web of the strip can be of particular interest when these elements are of the same nature, for example, both formed by 3D weaving, but is not mandatory within the scope of the invention. By way of illustration, the thickness el11 can be greater than or equal to 3 mm, for example, between 3 mm and 15 mm.

[0042] The counterform 100 further defines a corner 102 on each side of the part 101. The part 101 is located between the corners 102. Each corner 102 covers a respective intersection zone ZI. Each corner 102 is located on the side of a respective first deployed portion lia.

[0043] Each corner 102 has a rounded cross-section, and in particular, is more rounded than the corresponding intersection zone ZI, which can substantially form a right angle (90°). Each corner 102 can have a radius of curvature R102 greater than or equal to 5 mm, for example, 10 mm. This radius of curvature R102 can be between 5 mm and 20 mm, for example, between 10 mm and 20 mm. In the illustrated example, the corners 102 have a substantially symmetrical shape with respect to plane P.

[0044] The counterform 100 comprises a first face Fl located on the side of the intersection zones ZI and a second face F2 opposite the first face Fl and curved at least locally to form the corners 102. The radius of curvature R102 described above corresponds to the local radius of curvature of the second face F2 at the intersection zones ZI. The second face F2 has a curvilinear shape, for example, substantially an arc of a circle or an arc of an ellipse, at each of the corners 102. In the illustrated example, the second face F2 has a concave shape (curvature inwards) at each of the corners 102.

[0045] The counterform 100 further includes connecting edges 103 that rest on the first deployed portions lia. Each corner 102 is located between the portion 101 and a distinct edge 103. Each edge 103 extends a respective corner 102 along a first deployed portion lia. Each edge 103 extends over at least half the height Hlia of the corresponding first portion lia. Unless otherwise specified, the height Hlia is measured from zone 20 and transversely, or even perpendicularly, to it. In the illustrated example, each edge 103 extends over substantially the entire height Hlia. The counterform 100 can, as illustrated, have a substantially U-shaped cross-section. The thickness el03 of each edge 103 can, as illustrated, decrease continuously when moving away from part 101, which improves the continuity of the connection with the first corresponding portion lia.In general, the counterform 100 can extend over at least 50% of the length of zone 20 or the second portion 12b, for example over at least 75% of this length, or even over virtually the entire length.

[0046] The inventors performed a numerical simulation of the forces acting on the cross-section of zone 20 in the area near the slab on the side of the large air gap, considering a configuration as shown in Figure 7. By reinforcing zone 20 with the counterform 100, the stiffness of the web is increased, and therefore the forces acting on the uncoupling zone are increased. However, while the cross-section of the uncoupling zone was doubled in this case, the forces acting on the web at the ultimate loading are multiplied by less than two, demonstrating the control of stresses when the counterform is present. Furthermore, this configuration no longer contains any right angles, which reduces local stress concentrations in the intersection zones (ZI) during the loading of the part.

[0047] In the example shown in Figure 7, there is an empty space between each corner 102 and the corresponding intersection zone ZI. This space is intended to be filled by the organic matrix during the manufacturing of the part. However, it remains within the scope of the invention if a filling material 104 is introduced into this space as illustrated in Figure 8. The filling material 104 may include braids, by way of non-limiting example.

[0048] Figure 9 shows the preform of the part obtained in lateral view from the core preform described above. To obtain the shape illustrated in Figure 9, 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 invention remains within the scope of the invention if the forming process does not include this machining.

[0049] At a given end EB, the first deployed portions 30 each define a part 50 of a respective screed preform, that is to say that a first deployed portion 30 defines a part of a preform of a first screed and a second deployed portion 30, different from the first deployed portion, defines a part of a preform of a second screed, different from the first screed.

[0050] The woven belt texture 60 is then positioned on the deployed lateral portions 30 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, defines, with the deployed lateral portions 30, separate preforms 70 of the cleats at each end EB. Each preform 70 defines free spaces 55 for articulation with other parts. The texture 60 provides tensile strength. After positioning the texture 60, the preform 80 of the desired part is obtained. The texture 60 can also be obtained by three-dimensional weaving, for example, with an interlock weave. In the illustrated example, the preform 80 has a different El, E2 spacing from the preforms 70 of the screeds at the ends EB (see figure 10).This spacing also corresponds to the spacing between the 30 deployed lateral portions.

[0051] A counter-mold is then positioned around the preform 80 to define a cavity for introducing the matrix material. The core preform and the belt texture are then densified, for example, by introducing a resin, such as an epoxy resin, followed by cross-linking if it is a thermosetting resin, or cooling if it is a thermoplastic resin. The matrix can be formed using resin transfer molding, a well-established technique. This produces a composite material part designed to be articulated with other parts at its longitudinal ends. The organic matrix allows, in particular, the counter-mold to be bonded to the formed strip, and specifically, the counter-mold to be densified if it is made of textile material.The organic matrix allows the counterform 100 to be bonded to the second portion 12b and to the lateral portions lia. The fibrous reinforcement of the part can be made of carbon fibers and the part can have an organic matrix.

[0052] 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.

[0053] We have just described an example in which the edges 20a each have a straight line shape, but we do not depart from the scope of the invention when it is otherwise, as will now be described in connection with figure 11.

[0054] Figure 11 illustrates a variant of the band 110, which has a debonding zone 120 delimited by edges 120a having a broken line shape, thus with a variation in the angle formed between the edges 120a along the X-axis. The band 110 also has a structure similar to that just described, with a first region comprising lateral first portions 111a connected by an intermediate first portion 111b, and a second region comprising lateral first portions 112a connected by a second intermediate portion. The rest of the process is carried out similarly to that described above and allows the formation of lateral branches of the H having locally a relatively high angle al, which can, for example, reach up to 60°.

[0055] In the examples just described, the thickness of the second intermediate portion is unchanged along the X axis. The example in Figure 12 illustrates a variant in which the second region has areas of local overthickness.

[0056] Figure 12 shows a variant of the part preform 280, which includes a core preform 240 and a web texture 260 wrapped around it to define end cap preforms 270. In the illustrated example, the second intermediate portion 212b has reinforcement zones 2121b near the longitudinal ends EB. The zones 2121b are formed by a localized thickening as shown. The zones 2121b are woven in one piece with the rest of the web. The zones 2121b advantageously improve the mechanical strength of the second region, particularly at its free edges.

[0057] The examples just described relate to a preform concept for a "core-belt" type part. However, the invention is not limited to this solution, as illustrated in relation to Figure 13.

[0058] Figure 13 illustrates a variant in which a strip is formed, cut, and shaped similarly to that described above. During shaping, the first lateral portions 300 are unfolded and then directly machined and drilled at each longitudinal end of the strip, as shown by the dashed lines 320 in the upper drawing of Figure 13. The machining and drilling result in a preform 800 of the part, which has separate clevis preforms 700 at each longitudinal end, as illustrated in the lower drawing of Figure 13. Each preform 700 defines free spaces 550 for articulation with other parts. The spaces 550 were formed by drilling the first portions 300 at each longitudinal end, and the shape of the clevis preforms 700 was determined by the machining.The characteristics described above for the band and the counterform remain applicable to this embodiment.

[0059] The expression "between ... and ..." should be understood as including the boundaries.

Claims

Demands

1. A method for manufacturing a fibrous preform (40; 240) of a core for a composite part intended to be articulated with other parts, the method comprising: - the formation by three-dimensional weaving of a one-piece fibrous strip (10; 110) having a slender shape along a longitudinal axis (X) and comprising a debonding zone (20) extending along the longitudinal axis and spaced from each of the lateral edges (BL) of the strip, the debonding zone defining a first region (11) superimposed on a second region (12) and which can be separated from the latter, the first region comprising first lateral portions (11a; 111a) woven together by a first intermediate portion (11b; 111b), and the second region comprising second lateral portions (12a; 112a), connected by a second intermediate portion (12b), woven together with the first lateral portions, - cutting the first intermediate portion so as to separate the first lateral portions, - the shaping of the strip, after cutting the first intermediate portion, comprising the unfolding (D) of the first lateral portions transversely to the unbundling zone, and the folding (PL) of the second lateral portions along edges (20a) of the unbundling zone so as to give the strip thus shaped an H-shaped cross-section, each of the first unfolded lateral portions defining a part (50) of a respective cleat preform on each longitudinal end of the strip, the strip thus shaped defining an intersection zone (ZI) between the second intermediate portion and each first unfolded lateral portion, and - the positioning of a counterform (100) of reinforcement, textile or metallic, on the unbundling zone of the strip thus formed, said counterform comprising an intermediate part (101) positioned on the unbundling zone and a corner (102) on each side of the intermediate part, each corner covering a respective intersection zone and having a rounded shape in cross-section.

2. Method according to claim 1, in which each corner (102) of the counterform (100) is extended by a connecting edge (103) bearing on a first deployed lateral portion (lia) and extending over at least half of the height (H lia) of this first portion measured from the unbundling zone (20).

3. Method according to claim 1 or 2, wherein a filling material (104) is introduced between each corner (102) and the corresponding intersection zone (ZI).

4. A method according to any one of claims 1 to 3, wherein the counterform (100) of reinforcement is textile and obtained by three-dimensional weaving.

5. A method for manufacturing a fibrous preform (80; 280) of a composite part intended to be articulated with other parts, comprising: - the manufacture of the fibrous core preform (40; 240) by implementing a process according to any one of claims 1 to 4, and - the positioning of a woven fibrous belt texture (60; 260) on the first deployed lateral portions (30) of the core preform so as to define a loop around it, the belt texture thus positioned defining on each longitudinal end (EB), with the first deployed lateral portions, distinct cap preforms (70; 270).

6. Method according to claim 5, wherein the fibrous core preform (40; 240) and the belt texture (60; 260) are made of carbon yarns.

7. A method for manufacturing a fibrous preform (800) of a composite part intended to be articulated with other parts, comprising: - the formation by three-dimensional weaving of a one-piece fibrous strip (10) having a slender shape along a longitudinal axis (X) and comprising a debonding zone (20) extending along the longitudinal axis and spaced from each of the lateral edges (BL) of the strip, the debonding zone defining a first region (11) superimposed on a second region (12) and which can be separated from the latter, the first region comprising first lateral portions (11a; 111a) woven together by a first intermediate portion (11b; 111b), and the second region comprising second lateral portions (12a; 112a), connected by a second intermediate portion (12b), woven together with the first lateral portions, - cutting the first intermediate portion so as to separate the first lateral portions, and - the shaping of the strip, after cutting the first intermediate portion, comprising the unfolding (D) of the first lateral portions transversely to the unbundling zone, and the folding (PL) of the second lateral portions along edges (20a) of the unbundling zone so as to give the strip thus shaped an H-shaped cross-section, the strip thus shaped defining an intersection zone (ZI) between the second intermediate portion and each first unfolded lateral portion, and - the positioning of a counterform (100) of reinforcement, textile or metallic, on the unbundling area of ​​the strip thus formed, said counterform comprising an intermediate part (101) positioned on the unbundling area and a corner (102) on each side of the intermediate part, each corner covering a respective intersection area and having a rounded shape in cross-section, each of the first deployed lateral portions being machined and drilled so as to define a respective cleat preform (700) on each longitudinal end of the strip, the machining and drilling being carried out on the formed strip, before or after the positioning of the counterform.

8. A method for manufacturing a part made of composite material intended to be articulated with other parts, comprising at least: - the manufacture of the fibrous preform (80; 280; 800) of the part by implementing a process according to any one of claims 5 to 7, and - the formation of a matrix in a porosity of the fibrous preform thus obtained.

9. Method according to claim 8, wherein the matrix is ​​organic.

10. Method according to claim 8 or 9, wherein the part is a landing gear strut, part of a landing gear strut or a brake bar.

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