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

Abstract

The present invention relates to a method for manufacturing a fibrous preform (40, 240) of a core for a composite part intended to be articulated to other parts, comprising the formation of a strip (10, 110) in a single piece by three-dimensional weaving and the shaping thereof to give it a generally H-shaped cross-section.

Description

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

[0001] This disclosure relates to the manufacture of a composite part intended to be articulated with other parts at its ends, in particular the manufacture of a fiber preform of a core of such a part. Prior art

[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, document US 7,704,429 has proposed the manufacture of landing gear struts made of composite material which include regions, called yokes, which are intended for articulation and force introductions with other parts and are formed by a laminated structure with intercalation of plies between primary plies extending the body of the reinforcement. This solution can nevertheless have drawbacks. Indeed, yokes which have a laminated configuration can lead to an increase in the size of the force introduction zones compared to metal parts in order to avoid the risk of delamination. The weight saving of the overall system then becomes less interesting and the integration of the part more restrictive due to increased bulk. Another problem is that the proposed manufacturing technique implements significant manual intervention which can lead to non-conformities and an increase in cost.Finally, the mechanical performance of the composite material proposed in this document can be improved, particularly in terms of compressive strength over a middle zone of the length of the part, known as the common zone. One option to address this is to add material in the common zone, which then penalizes the mass and therefore does not provide complete satisfaction. WO2010146288 is known, which discloses a distributor element. CMC turbine, FR2983428 which discloses a method for manufacturing a turbomachine blade including integrated platforms, FR3116753 which discloses a method for manufacturing a composite material blade with integrated platforms and fixing lugs and W02014076408 which discloses a single-piece blade preform for a turbomachine.

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

[0005] The present invention relates, according to a first aspect, to a method of manufacturing a fibrous preform of a core for a composite part intended to be articulated with other parts, the method comprising: - forming by three-dimensional weaving a single-piece fibrous strip having a slender shape along a longitudinal axis and comprising a decoupling zone extending along the longitudinal axis and spaced from each of the lateral edges of the strip, the decoupling zone defining a first region superimposed on a second region and which can be spaced apart from the latter, the first region having a thickness greater than that of the second region and comprising first woven lateral portions connected by an intermediate portion, and the second region comprising second woven lateral portions with the first lateral portions, - cutting the intermediate portion so as to separate the first lateral portions, and - shaping the strip, after cutting the intermediate portion, comprising deploying the first lateral portions transversely to the uncoupling zone, and folding the second lateral portions along edges of the uncoupling zone so as to give the strip thus shaped an H-shaped cross-section, each of the deployed first lateral portions defining a part of a respective screed preform on each longitudinal end of the strip.

[0006] The invention thus proposes the manufacture of a core preform suitable for obtaining a composite part having two yokes at each longitudinal end. The invention allows, if desired, the formation of a spacing scalable between the lateral branches of the H, which are formed by the first deployed portions, by modifying the local width of the delinking zone to obtain in particular a different spacing between the yokes at the ends. The delinking zone is designed in such a way that the final shape of the core is generated at the time of shaping the strip.

[0007] The invention has the advantage of producing a core preform in a single piece of fabric (monobloc) to avoid handling which is a source of defects during manufacturing, and also to reduce the interfaces between multiple preforms which are sources of mechanical weaknesses. The use of a weaving technique also makes it possible to guarantee the presence of threads extending from one longitudinal end to another on the branches of the H to ensure the desired compression stress absorption. The second region forms a horizontal junction between these branches which guarantees, in turn, the overall strength of the part, particularly in buckling.

[0008] In an exemplary embodiment, the decoupling zone has a first width at a first longitudinal end and a second width, different from the first width, at a second longitudinal end opposite the first end, the first deployed lateral portions being spaced apart by a different distance at the longitudinal ends.

[0009] Such a feature makes it possible to obtain different spacings between the yokes on each of the longitudinal ends. This can present different advantages depending on the application, in particular: the possibility of limiting the quantity of material removed for the first intermediate portion by reducing the width of the debonding zone, or the possibility of housing equipment between the yokes by spreading them apart.

[0010] In an exemplary embodiment, the second region further comprises a second intermediate portion connecting the second lateral portions and which comprises at least one reinforcement zone defined by a local excess thickness.

[0011] Such a characteristic advantageously makes it possible to improve the mechanical strength of the second region.

[0012] In particular, the second intermediate portion may comprise, on the side of each longitudinal end, a reinforcement zone defined by a local excess thickness.

[0013] Such a feature advantageously makes it possible to reinforce the free edges of the second region.

[0014] The invention also relates to a method for manufacturing a fiber 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 - positioning 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, separate screed preforms.

[0015] This forms a core-belt type preform whose belt ensures the absorption of tensile forces.

[0016] In an exemplary embodiment, the core fiber preform and the belt texture are made of carbon yarns.

[0017] The invention is however not limited to the production of a “core-belt” type preform. Thus the invention relates as a variant, according to a second aspect, to a method of manufacturing a fiber preform of a composite part intended to be articulated with other parts, comprising: - forming by three-dimensional weaving a single-piece fibrous strip having a slender shape along a longitudinal axis and comprising a decoupling zone extending along the longitudinal axis and spaced from each of the lateral edges of the strip, the decoupling zone defining a first region superimposed on a second region and which can be spaced apart from the latter, the first region having a thickness greater than that of the second region and comprising first woven lateral portions connected by an intermediate portion, and the second region comprising second woven lateral portions with the first lateral portions, - cutting the intermediate portion so as to separate the first lateral portions, and - shaping the strip, after cutting the intermediate portion, comprising deploying the first lateral portions transversely to the uncoupling zone, and folding the second lateral portions along the edges of the uncoupling zone so as to give the strip thus shaped an H-shaped cross-section, each of the deployed first lateral portions being machined and drilled so as to define a respective screed preform on each longitudinal end of the strip.

[0018] This case concerns the production of machined screeds during the shaping of the strip.

[0019] 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 fiber preform of the part by implementing a process as described above, and - the formation of a matrix in a porosity of the fibrous preform thus obtained.

[0020] In one exemplary embodiment, the matrix is ​​organic.

[0021] In an exemplary embodiment, the part is a landing gear strut, a portion of a landing gear strut, or a brake bar. Brief description of the drawings [Fig. 1] Figure 1 shows, schematically and partially in top view, an example of a fibrous strip usable in the context 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 shows, schematically and partially, the shaping of the strip in Figure 1. [Fig. 4] Figure 4 shows, schematically and partially, the shaping of the strip of Figure 1 at the level of another cross-section taken according to IV-IV. [Fig. 5] Figure 5 represents, schematically and partially, the shaping of the strip of figure 1 at the level of another cross section taken along VV. [Fig. 6] Figure 6 shows, schematically and partially, a cross-section of the core preform obtained from the strip of Figure 1 annotated with different geometric parameters. [Fig. 7] Figure 7 shows, schematically and partially, a side view of an example of a part preform according to the invention. [Fig. 8] Figure 8 shows, schematically and partially, a top view of the preform of Figure 7. [Fig. 9] Figure 9 shows, schematically and partially in top view, another example of a fibrous strip usable in the context of the invention. [Fig. 10] Figure 10 shows, schematically and partially, a side view of another example of a part preform in the context of the invention. [Fig. 11] Figure 11 shows, schematically and partially, a side view of another example of a part preform in the context of the invention. Description of the embodiments

[0022] The invention is now described by means of figures, present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0023] Figures 1 and 2 illustrate, respectively in top view and in cross section, an example of a fibrous strip 10 usable in the context 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 delimited laterally by lateral edges BL. The edges BL delimit the strip 10 along the lateral direction L. The edges BL each extend along the axis X. The width of the strip 10 corresponds to the distance between the edges BL. Unless otherwise stated, the widths are measured in cross section, or even perpendicular, to the axis X along the direction L. The strip 10 may, as illustrated, have a substantially constant width over its entire length. The thickness direction is, for its part, materialized by the axis E (see figure 2). The thickness of the strip 10 corresponds to its smallest dimension.

[0024] The strip 10 is obtained by three-dimensional weaving in a single piece (monobloc) by providing a delinking zone, as will be detailed below. The strip 10 comprises first threads, directed along the X axis, which are woven with second threads directed along the L direction. The first threads may be warp threads and the second threads weft threads, or vice versa. By "three-dimensional weaving" or "3D weaving" is meant a weaving method by which at least some of the first threads bind second threads on several layers of second threads. Such weaving may be carried out in a Jacquard type loom, in a manner known per se. For example, and without limitation, an "interlock" weaving weave may be used for the strip 10.

[0025] Figure 2 represents a cross-section of the strip 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 strip 10 by varying the width of the debonding zone.

[0026] The strip 10 has a delinking zone 20 which extends along the X axis, here over the entire length of the strip 10 from one end EB to another. The zone 20 extends over only a portion of the width of the strip 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 strip 10 and only opens outside the strip at the ends EB. The zone 20 is delimited laterally by two edges 20a. The profile of the edges 20a determines the geometry of the core preform once shaped, as will be detailed below. In the example illustrated, 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 α is unchanged along the X axis. However, it does 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.

[0027] Area 20 defines a first woven region 11 which is superimposed on a second woven region 12. In area 20, weaving has been deliberately omitted between them layers of wires of the first 11 and the second 12 regions so as to be able to carry out the shaping as will be described below. The first region 11 can be spaced from the second region 12 due to the presence of the zone 20. The zone 20 is located between the first 11 and second 12 regions. The first 11 and second 12 regions are offset along the direction E. Each of the first 11 and second 12 regions extends over the entire width of the strip 10 from one edge BL to another. The first region li has a first thickness en which is greater than a second thickness e^ of the second region 12. The thicknesses are measured along the direction E.

[0028] More specifically, the first region 11 comprises first lateral portions 11a which are each located on the side of a respective edge BL. Each first portion 11a is delimited laterally by an edge BL. The first portions 11a are obtained by three-dimensional weaving. The first portions 11a are textileally linked by an intermediate portion 11b which is intended to be cut in the remainder of the method as detailed below. When moving in the first region 11 from one edge BL to another, one passes successively through a first portion 11a, through the portion 11b, then again through a first portion 11a. The portion 11b may not be woven to facilitate its subsequent cutting, and may only comprise second threads which connect the first portions 11a. Alternatively, the portion 11b is woven and comprises, for example, first threads distinct from the first threads used in the rest of the strip 10.Thus, the strip 10 can generally be formed of carbon threads but with a portion 11b formed of first polymeric threads, for example polyester which are less expensive than carbon threads.

[0029] The second region 12 comprises second lateral portions 12a which are each located on the side of a respective edge BL. Each second portion 12a is delimited laterally by an edge BL. The second portions 12a are obtained by three-dimensional weaving. The second region 12 further comprises a second intermediate portion 12b which textileally connects the second portions 12a. The second portion 12b may be obtained by three-dimensional weaving. Alternatively, the second portion 12b may be formed solely by unidirectional layers of second yarns connecting the two portions 12a which are woven. second portion 12b extends over the entire width of the 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 superimposed with a first part thereof. A second part of the first portions 11a, different from the first part, is superimposed on the second portion 12b. The thickness of the first part of the first portions 11a is greater than the thickness of the second portions 12a.

[0030] Once the strip 10 is obtained, the manufacture of the core preform continues as illustrated in Figure 3.

[0031] The first portion 11b is first cut using means known per se. The first portion 11b is cut along its entire length or along the entire length of the strip 10. This forms a zone 11c of lack of material between the first portions 11a (see drawing 3A). The zone 11c is located between two inner edges BL1 of the first portions 11a. The first portions 11a are separated following this cutting and can be deployed independently of one another.

[0032] The process continues with the shaping of the strip, after this cutting, as illustrated in drawings 3B and 3C.

[0033] The shaping is carried out in a shaping tool (not shown) to the shape of the core of the part to be obtained.

[0034] The shaping comprises the deployment of the first portions 11a outwards, materialized by the arrows D in drawing 3B, during which the edges BL1 are moved away from each other. The edges BL1 are also moved away from the second portion 12b during deployment. During deployment, the first portions 11a are moved away from a median plane P of the strip 10. The plane P may be a plane of symmetry of the strip 10. The first portions 11a are deployed so as to be positioned transversely, or even substantially perpendicularly, to the zone 20. The deployment of the first portions 11a leads to an increase in the width of the zone 11c.

[0035] The shaping also includes the inward folding of the second portions 12a on the edges 20a. This folding is shown by the arrows PL in drawing 3B. The second portions 12a are folded towards each other, and in the direction of the plane P. The second portions 12a are folded so as to be positioned transversely, or even substantially perpendicularly, to the zone 20. The second portions 12a are folded and the first portions 11a straightened along the edges 20a. The deployment of the portions 11a and the folding of the portions 12a are carried out jointly because these portions are woven together.

[0036] After shaping, a core preform 40 is obtained which has an H-shaped cross-section as illustrated in drawing 3C. The first deployed portions 30 form the lateral branches of the H and here define, on their upper and lower part, a positioning surface 32 for the belt texture. Due to the variation in width of the zone 20 along the X axis, the first deployed portions 30 form between them the angle a described above, which makes it possible to have a flared geometry for the part and in particular distinct spacings between the yokes at each of the ends EB. The orientation of the first wires along the X axis in the first deployed portions 30 makes it possible to ensure that they withstand the compressive forces in 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.

[0037] A consequence of the described solution is that the second portion 12b is, in the core preform, at a different altitude h from one side of the part to the other (see Figures 4 and 5). Figure 6 illustrates the relevant geometric parameters for determining the altitude h of the second portion 12b. The value of h is defined such that the length L1 is constant over the entire part, regardless of variations in RI, el or DI:

[0038] [Math. 1] h ~ 1 / 2[L1 — £M 4 l(3 — i ) 4 £1(4 - 7t)]

[0039] with in the formula above: el = thickness of portion 12b which can possibly be variable (see figure 10), RI = internal radius of the preform, generally taken as substantially equal to el to ensure good forming of the radius, and L1 = length of the curve shown in bold at the height of the debond in the preform.

[0040] The variation in altitude h reflects the bringing together or the separation of the first deployed portions 30. It may be interesting to bring these branches together to limit the quantity of material removed in the portion 11b. Alternatively, it may be interesting to separate them if one wishes to have space in the lower part of the preform (to accommodate equipment for example).

[0041] Figure 7 shows the core preform 40 obtained following the shaping which has just been described in side view. To obtain the shape illustrated in Figure 7, the first deployed portions 30 were machined at the ends EB so as 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 set back relative to the ends EB. However, it is not outside the scope of the invention if the shaping does not include this machining.

[0042] At a given end EB, the first deployed portions 30 each define a part 50 of a respective yoke preform, that is to say that a first deployed portion 30 defines a part of a preform of a first yoke and a second deployed portion 30, different from the first deployed portion, defines a part of a preform of a second yoke, different from the first yoke.

[0043] 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 strip shape which is wrapped around the preform 40. The texture 60 is positioned on the surface 32 resting on the branches 30. The texture 60 thus positioned defines with the deployed lateral portions 30, on each end EB, preforms 70 of distinct yokes. Each preform 70 defines free spaces 55 intended for articulation with other parts. The texture 60 ensures tensile strength. After positioning the texture 60, the preform 80 of the part to be obtained 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 spacing E1, E2 different from the preforms 70 of the yokes at the ends EB (see figure 8).This spacing also corresponds to the spacing between the deployed side portions 30.

[0044] A counter-mold is then positioned around the preform 80 so as 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 crosslinking thereof if it is a thermosetting resin or by cooling if it is a thermoplastic resin. The formation of the matrix can be carried out by resin transfer molding technique which corresponds to a technique known per se. This produces a part made of composite material intended to be articulated with other parts at its longitudinal ends. The fibrous reinforcement of the part can be formed of carbon threads and the part can have an organic matrix.

[0045] The part may or may not be intended for an aeronautical application. The part may, for example, be a connecting rod, a landing gear strut or a constituent element thereof, or a brake bar. The part may be intended to undergo mainly tensile and compressive forces in operation. The part obtained may be mounted to other parts by positioning through the free spaces 55 a hinge pin for connection to other parts as well as an insert for contact with this pin.

[0046] 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 9.

[0047] Figure 9 illustrates a variant of strip 110 which has a delinking zone 120 delimited by edges 120a having a broken line shape, therefore with variation of the angle formed between the edges 120a along the axis X. The strip 110 also has a structure similar to that which has just been described with a first region comprising first lateral portions 111a connected by a first intermediate portion 111b and a second region comprising first lateral portions 112a connected by a second intermediate portion. The rest of the method is carried out in a similar manner to that described above and makes it possible to form lateral branches of the H having locally a relatively high angle al which can for example be up to 60°.

[0048] In the examples just described, the thickness of the second intermediate portion is unchanged along the X axis. The example in Figure 10 illustrates a variant in which the second region has areas of local excess thickness.

[0049] Figure 10 shows a variant of part preform 280 which comprises a core preform 240 and a belt texture 260 wrapped around so as to define yoke preforms 270 at the ends. In the example illustrated, the second intermediate portion 212b has reinforcement zones 2121b in the vicinity of the longitudinal ends EB. The zones 2121b are formed by a local excess thickness as illustrated. The zones 2121b are woven in a single piece with the rest of the strip.

[0050] The examples which have just been described concern a concept of a part preform of the “core-belt” type. The invention is however not limited to this solution as illustrated in connection with figure 11.

[0051] Figure 11 illustrates a variant in which a strip is formed, cut and shaped in a manner similar to that described above. During the shaping, first deployed lateral portions 300 are obtained which are then directly machined and drilled on each longitudinal end of the strip as shown by the dotted lines 320 in the top drawing of Figure 11. The machining and drilling make it possible to obtain a part preform 800 having on each longitudinal end separate yoke preforms 700 as illustrated in the bottom drawing of Figure 11. Each preform 700 defines free spaces 550 intended for articulation with other parts. The spaces 550 were formed by drilling the first portions 300 on each longitudinal end, and the shape of the yoke preforms 700 was imparted by the machining carried out. The characteristics described above for the strip remain applicable to this embodiment.

Claims

Claims

1. 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: - forming by three-dimensional weaving a single-piece fibrous strip (10; 110) having a slender shape along a longitudinal axis (X) and comprising a decoupling zone (20) extending along the longitudinal axis and spaced from each of the lateral edges (BL) of the strip, the decoupling zone defining a first region (11) superimposed on a second region (12) and which can be spaced apart from the latter, the first region having a thickness greater than that of the second region and comprising first woven lateral portions (11a; 111a) connected by an intermediate portion (11b; 111b), and the second region comprising second woven lateral portions (12a; 112a) with the first lateral portions, - cutting the intermediate portion so as to separate the first lateral portions, and - shaping the strip, after cutting the intermediate portion, comprising the deployment (D) of the first lateral portions transversely to the uncoupling zone, and the folding (PL) of the second lateral portions along edges (20a) of the uncoupling zone so as to give the strip thus shaped an H-shaped cross-section, each of the deployed first lateral portions defining a part (50) of a respective screed preform on each longitudinal end of the strip.

2. Method according to claim 1, in which the uncoupling zone (20; 120) has a first width at a first longitudinal end (EB) and a second width, different from the first width, at a second longitudinal end (EB) opposite the first end, the first deployed lateral portions (30) being spaced apart by a different distance (El; E2) at the longitudinal ends.

3. Method according to claim 1 or 2, in which the second region further comprises a second intermediate portion (212b) connecting the second lateral portions and which comprises at least one reinforcement zone (2121b) defined by a local excess thickness.

4. Method according to claim 3, in which the second intermediate portion (212b) comprises, on the side of each longitudinal end (EB), a reinforcement zone (2121b) defined by a local excess thickness.

5. Method for manufacturing a fiber 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 method according to any one of claims 1 to 4, and - positioning 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 the latter, the belt texture thus positioned defining on each longitudinal end (EB), with the first deployed lateral portions, separate yoke preforms (70; 270).

6. The method of claim 5, wherein the core fiber preform (40; 240) and the belt texture (60; 260) are made of carbon yarns.

7. Method for manufacturing a fiber preform (800) of a composite part intended to be articulated with other parts, comprising: - forming by three-dimensional weaving a single-piece fibrous strip (10) having a slender shape along a longitudinal axis (X) and comprising a delinking zone (20) extending along the longitudinal axis and spaced from each of the lateral edges (BL) of the strip, the delinking zone defining a first region (11) superimposed on a second region (12) and which can be spaced apart from the latter, the first region having a thickness greater than that of the second region and comprising first woven lateral portions (11a; 111a) connected by an intermediate portion (lib; 111b), and the second region comprising second lateral portions (12a; 112a) woven with the first lateral portions, - cutting the intermediate portion so as to separate the first lateral portions, and - shaping the strip, after cutting the intermediate portion, comprising the deployment (D) of the first lateral portions transversely to the uncoupling zone, and the folding (PL) of the second lateral portions along edges (20a) of the uncoupling zone so as to give the strip thus shaped an H-shaped cross-section, each of the deployed first lateral portions being machined and pierced so as to define a respective yoke preform (700) on each longitudinal end of the strip.

8. 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 method 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. The method of claim 8, wherein the matrix is ​​organic.

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

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