Belted mechanical part comprising an interface insert

Abstract

The invention relates to a mechanical part (100) comprising a core (110) having a fibrous reinforcement densified by a matrix, comprising at least one opening adjacent to the core (110) through which a shaft is intended to pass in order to establish a connection with another part, and comprising a belt (120) having a fibrous reinforcement densified by the matrix surrounding the core (110) and the at least one opening. According to the invention, the part (100) is characterized in that at least one insert (140) extending from the opening is positioned between the core (110) and the belt (120).

Description

Description Title of the invention; Belted mechanical part comprising an interface insert Technical Field

[0001] The present invention relates to a part made of composite material intended to be articulated with one or more other parts at its ends, in particular a connecting rod or a landing gear lever. Prior art

[0002] Figure 1 shows a landing gear comprising two struts 1 and 1', respectively called main strut and lateral strut. These struts are articulated to the landing gear leg 4 and to the landing gear frame 5. Each strut 1 and 1' is formed of two connecting rods, as illustrated in Figure 2. Thus, the strut 1 comprises an upper connecting rod 3 and a lower connecting rod 2. The connecting rods of a strut are articulated to each other and to other parts of the landing gear at their ends, by means of articulation pins. Such connecting rods are subjected in operation to significant mechanical forces, mainly in compression and in tension, oriented along the longitudinal axis of the part.

[0003] These connecting rods were usually made of steel, aluminum, or titanium alloys. In order to lighten these rods, they can now be made of composite material. Indeed, the production of connecting rods in composite material allows for lighter connecting rods than those made of metal while maintaining good mechanical properties. Composite material connecting rods are therefore easier to operate during landing gear operation and help reduce the weight of the aircraft, thus reducing fuel consumption.

[0004] Documents FR 2 887 601 A1 and FR 3 017 819 describe such connecting rods made of composite material, comprising a core surrounded by a belt, the fiber reinforcements of the core and the belt being produced by three-dimensional weaving then co- injected. Figure 3 illustrates an example of a connecting rod made of composite material according to the prior art comprising a core A, a ring B located in the extension of the core A and allowing articulation with another part and a belt C surrounding the core A and the ring B.

[0005] It was found that, in operation, cracks F could appear on the connecting rod at the interface between the web A and the belt C, said cracks generally extending from the ring B, as illustrated in Figure 3. Statement of the invention

[0006] These cracks were found to be caused by a high concentration of stresses at the interface point between the core, the belt, and the hole receiving the ring. Indeed, it was found that the fiber reinforcements of the core and the belt did not deform in the same way, thus generating significant shear stresses at the interface between the core and the belt. The fiber orientations in the core and the belt near the interface between the core and the belt cause very different coefficients of expansion on either side of the interface, which can lead to the appearance of cracks. In addition, it was found that these cracks could be favored by residual manufacturing stresses. These residual stresses appear during the cooling of the part during its manufacturing process, and depend on the difference in coefficient of expansion between the core and the belt.

[0007] The invention therefore aims to prevent the formation of cracks at the interface between the core and the belt, or at least to increase the tensile or compressive load supported by the part in order to delay the appearance of cracks.

[0008] To this end, the invention proposes a mechanical part comprising a core comprising a fibrous reinforcement densified by a matrix, comprising at least one orifice adjacent to the core and intended to be crossed by an axis to make a connection with another part, and comprising a belt comprising a fibrous reinforcement densified by the matrix surrounding the core and said at least one orifice, the part being characterized in that at least one insert extending from the orifice is interposed between the core and the belt.

[0009] Thus, the presence of such an insert makes it possible to separate the core from the belt in the area most at risk of cracking. In operation, the core and the belt each have their own mechanical function and each undergo different mechanical stresses to ensure the proper functioning of the part. By placing an insert between the core and the belt, we act on the transmission of forces between the core and the belt and we can increase the distance over which said forces are transmitted. The risk of cracking is thus reduced.

[0010] According to one embodiment of the invention, the insert is a layer of matrix material.

[0011] Thus, the insert is particularly flexible and ductile, and greatly limits stress concentrations at the interface between the core and the belt. In addition, the insert can then be made from the same material as the core and belt matrix, which makes the mechanical part easy to manufacture.

[0012] According to one embodiment, the insert comprises a superposition of fibrous layers produced by two-dimensional weaving and densified by a matrix, the fibrous layers being superimposed on each other from the core to the belt.

[0013] Thus, the insert is relatively flexible and limits stress concentrations. The use of several layers allows for a certain deformability and a reduction in shear stresses.

[0014] According to a particular embodiment of the invention, the fibrous layers have fiber orientations of ±45°, 0° / 90° or ±45790°.

[0015] Indeed, such orientations ensure optimal improvement of the mechanical performance of the interface between the core and the belt.

[0016] According to a particular embodiment of the invention, the matrix is ​​an epoxy resin.

[0017] According to a particular embodiment of the invention, the thickness of the insert is between 4% and 40% of a reference distance extending between the axis of the orifice and the closest point of the external surface of the belt.

[0018] The thicker the insert, the more it will help to reduce stresses at the interface between the core and the belt. However, an insert that is too thick will be detrimental to the mechanical performance of the part, particularly when the part is subjected to compressive loading. Such a range of values ​​for the thickness of the insert thus provides very satisfactory protection against cracks at the interface between the core and the belt without significantly reducing the general mechanical performance of the part or without making the part too heavy.

[0019] According to a particular embodiment of the invention, the insert extends from the ring over a distance of between 80% and 220% of a reference distance extending between the axis of the orifice and the closest point of the external surface of the belt.

[0020] In fact, it was found that the risk of cracks appearing was limited to an area close to the ring, i.e. close to the orifice. It is therefore not necessary to unnecessarily extend the insert in length, at the risk of reducing the overall mechanical performance of the part or making the part too heavy.

[0021] According to a particular embodiment of the invention, the thickness of the insert decreases from a portion of the insert adjacent to the orifice to a portion of said insert remote from the orifice.

[0022] This reduction in thickness can be regular and / or continuous.

[0023] Such a reduction in thickness allows for more uniform exposure of the insert to shear stresses, and thus better resistance of the insert in shear.

[0024] According to a particular embodiment of the invention, the part further comprises at least one ring arranged in the orifice and adjacent to the core.

[0025] The invention also relates to a method for manufacturing a fibrous assembly intended to form the fibrous reinforcement of a mechanical part made of composite material, comprising:

[0026] - the production by three-dimensional weaving of a fibrous core preform and a fibrous belt preform,

[0027] - arranging the belt fiber preform around the core fiber preform such that the belt fiber preform defines a cylindrical space adjacent to the core fiber preform.

[0028] According to a particular aspect of the invention, the fibrous core preform comprises a first longitudinal edge and a second longitudinal edge opposite the first longitudinal edge, the first longitudinal edge and the second longitudinal edge being connected by a first curved edge partially delimiting the cylindrical space.

[0029] According to a first embodiment, the arrangement of the fiber belt preform around the fiber core preform is carried out so as to leave at least one gap between the fiber core preform and the fiber belt preform extending from the cylindrical space.

[0030] According to a second embodiment of the invention, the fibrous belt preform is in contact with the fibrous core preform over the entire length of the first and second longitudinal edges. Thus, the fibrous assembly obtained is free of interstices.

[0031] According to a first variant of the first embodiment of the invention, the gap is filled by a superposition of fibrous layers produced by two-dimensional weaving, the fibrous layers being superimposed on one another from the core fibrous preform to the belt fibrous preform.

[0032] The invention also relates to a method of manufacturing a mechanical part comprising:

[0033] - the manufacture of a fibrous assembly according to the process described above,

[0034] - densification of the fibrous assembly by a matrix while retaining the cylindrical space free of matrix, so as to obtain a part made of composite material comprising a core, a cylindrical orifice adjacent to the core, a belt surrounding the core and the cylindrical orifice, the final mechanical part comprising at least one insert extending from the orifice between the core and the belt.

[0035] According to the first variant of the first embodiment of the invention, the superposition of fibrous layers produced by two-dimensional weaving is densified by the matrix at the same time as the core and belt fiber preforms. The insert of the final part can then be formed by the superposition of fiber layers densified by the matrix.

[0036] According to a second variant of the first embodiment of the invention, the gap of the fibrous assembly is filled with an elastomeric material before densification. The insert of the final part can then be formed by the elastomeric material.

[0037] According to a third variant of the first embodiment of the invention, the gap of the fibrous assembly is filled only by the matrix material during densification. The insert of the final part can then be formed only by the matrix material. The insert of the final part can then be devoid of fibrous reinforcement.

[0038] Thus, according to one aspect of the first embodiment of the invention, the method of manufacturing a part comprises the introduction of the matrix material into the gap during densification, which corresponds for example to the first variant and the third variant of the first embodiment of the invention.

[0039] According to a particular aspect of the method for manufacturing a part made of composite material, the method may further comprise:

[0040] - removing at least one portion of the fibrous assembly densified by the matrix, said at least one removed portion extending from the cylindrical orifice and separating the belt from the core,

[0041] - the introduction of a filling material into the at least one removed portion so as to obtain the at least one insert.

[0042] The filling material can be a resin, an elastomeric material or an adhesive joint.

[0043] This aspect is particularly suitable for the second embodiment of the invention, since it allows the insert to be formed by removing a portion of the core and a portion of the belt. This aspect is of little interest in the context of the first variant and the second variant of the first embodiment of the invention. This aspect may be of interest in the context of the third variant of the first embodiment, because it makes it possible to form the insert by machining a portion devoid of fibers. Brief description of the drawings

[0044] [Fig. 1] Figure 1 is a schematic view of a landing gear.

[0045] [Fig. 2] Figure 2 is a schematic view of a strut of the landing gear of Figure 1.

[0046] [Fig. 3] Figure 3 is a partial schematic view of a connecting rod according to the prior art having cracks.

[0047] [Fig. 4] Figure 4 is a schematic sectional view of a connecting rod with an insert.

[0048] [Fig. 5] Figure 5 is a detailed view of the connecting rod of Figure 4.

[0049] [Fig. 6] Figure 6 is a schematic detail view of another connecting rod with an insert.

[0050] [Fig. 7] Figure 7 is a perspective view of a fiber preform of the connecting rod core of Figures 4 and 5.

[0051] [Fig. 8] Figure 8 is a sectional view of the fibrous core preform of Figure 7 on which are arranged layers of two-dimensional fabric intended to form the fibrous reinforcement of the insert.

[0052] [Fig, 9] Figure 9 is a sectional view of the fiber reinforcement of the connecting rod of Figures 4 and 5. Description of the embodiments

[0053] Figures 4 and 5 illustrate a first example of a mechanical part 100 according to the invention. Figure 6 illustrates a second example of a mechanical part 300 according to the invention.

[0054] The part 100, 300 comprises a core 110, 310, a belt 120, 320, a first orifice 101, 301 and possibly a second orifice 102. Rings 130 and 130bis can be mounted respectively in the first orifice 101, 131 and the second orifice 102. It is of course not beyond the scope of the invention if the part does not include a ring. In accordance with the invention, the part 100, 300 further comprises a first insert 140, 340 and possibly a second insert 150, 350. The parts 100, 300 as illustrated only have single yokes. It is of course not beyond the scope of the invention if the mechanical part has double yokes, as is for example the case of the parts illustrated in document FR 2 887 601 A1.

[0055] The first orifice 101, 301 is delimited by an internal surface. The second orifice 102 is delimited by an internal surface. The first orifice 101, 301 is open. The second orifice 102 is open.

[0056] The core 110, 310 comprises a first longitudinal edge 110a, 310a and a second longitudinal edge 110b, 310b opposite the first longitudinal edge 110a, 310a. The core 110, 310 further comprises at least one first curved edge 110c, 310c which connects the first longitudinal edge 110a, 310a to the second longitudinal edge 110b, 310b. The first curved edge 110c, 310c partially delimits the first orifice 101, 301. Thus, a portion of the internal surface of the first orifice 101, 301 is defined by the first curved edge 110c, 310c of the core 110, 310. As illustrated in FIG. 4, the core 110, 310 may comprise a second curved edge opposite the first curved edge 110c, 310c, which connects the first longitudinal edge 110a, 310a to the second longitudinal edge 110b, 310b. The second curved edge partially delimits the second orifice 102. Thus, a portion of the internal surface of the second orifice 102 is defined by the second curved edge of the core 110, 310.

[0057] The ring 130 comprises an inner surface 130a and an outer surface 130b. The ring 130 is adjacent to the core 110. The outer surface 130b of the ring 130 may correspond to the inner surface of the first orifice 101. The outer surface 130b is in contact with the first curved edge 110c of the core 110. The first curved edge 110c of the core 110 matches the outer surface 130b of the ring 130. The ring 130 is intended to be crossed by an axis to make a connection with another part. The ring 130 extends around an axis A.

[0058] The additional ring 130bis comprises an inner surface and an outer surface. The additional ring 130bis is adjacent to the core 110 and opposite the ring 130. The external surface of the additional ring 130bis may correspond to the internal surface of the second orifice 102. The external surface of the additional ring 130bis is in contact with the second curved edge of the core 110. The second curved edge of the core 110 matches the external surface of the additional ring 130bis. The additional ring 130bis is intended to be crossed by an axis to make a connection with another part. The additional ring 130bis extends around an axis A'. The axis A' of the additional ring 130bis is preferably parallel to the axis A of the ring 130.

[0059] The first insert 140, 340 comprises a first longitudinal edge 140a, 340a and a second longitudinal edge 140b, 340b opposite the first longitudinal edge 140a, 340a. The first longitudinal edge 140a, 340a of the first insert 140, 340 is in contact with the first longitudinal edge 110a, 310a of the core 110, 310. The first insert 140, 340 further comprises a transverse edge which connects the first longitudinal edge 140a, 340a to the second longitudinal edge 140b, 340b of said first insert 140, 340. The transverse edge of the first insert 140, 340 partly delimits the first orifice 101, 301. Thus, a portion of the internal surface of the first orifice 101, 301 is defined by the transverse edge of the first insert 140, 340. The transverse edge of the first insert 140, 340 may be in contact with the ring 130. The transverse edge of the first insert 140, 340 may be in contact with the external surface 130b of the ring 130.The transverse edge of the first insert 140, 340 can fit the external surface 130b of the ring 130.

[0060] The second insert 150, 350 comprises a first longitudinal edge 150a, 350a and a second longitudinal edge 150b, 350b opposite the first longitudinal edge 150a, 350a. The first longitudinal edge 150a, 350a of the second insert 150, 350 is in contact with the second longitudinal edge 110b, 310b of the core 110, 310. The second insert 150, 350 further comprises a transverse edge which connects the first longitudinal edge 150a, 350a to the second longitudinal edge 150b, 350b of said second insert 150, 350. The transverse edge of the second insert 150, 350 partly delimits the first orifice 101, 301. Thus, a portion of the internal surface of the first orifice 101, 301 is defined by the transverse edge of the second insert 150, 350. The transverse edge of the second insert 150, 350 may be in contact with the ring 130. The transverse edge of the second insert 150, 350 may be in contact with the external surface 130b of the ring 130. The transverse edge of the second insert 150, 350 may fit the external surface 130b of the ring 130.

[0061] In the example illustrated in Figures 4 and 5 and in the example illustrated in Figure 6, the parts 100 and 300 comprise two inserts 140, 340 and 150, 350. It is of course not outside the scope of the invention if the part comprises only one insert, or if it comprises more than two inserts. For example, a part according to the invention may comprise a pair of inserts for each orifice receiving a ring.

[0062] The belt 120, 320 surrounds the core 110, 310 and the orifice(s) 101, 301, 102. Thus, the belt 120, 320 surrounds the ring(s) 130, 130bis. The belt 120, 320 partially delimits the orifice(s) 101, 102, 301. The belt 120, 320 comprises a closed inner edge 120a. The belt 120, 320 comprises an outer surface opposite the closed inner edge 120a. The closed inner edge 120a of the belt 120, 320 is in contact with the first insert 140, 340. The closed inner edge 120a of the belt 120, 320 is in contact with all the inserts 140, 150, 340, 350. The closed inner edge 120a of the belt 120, 320 is in contact with the second longitudinal edge 140b, 340b of the first insert 140, 340. The closed inner edge 120a of the belt 120, 320 is in contact with the second longitudinal edge 150b, 350b of the second insert 150, 350. The closed inner edge 120a of the belt 120, 320 is in contact with the outer surface 130b of the ring 130.The closed inner edge 120a of the belt 120, 320 is in contact with the outer surface of the additional ring 130bis. The closed inner edge 120a partly delimits the first orifice 101, 301 and the second orifice 102. Thus, a portion of the inner surface of the first orifice 101, 301 is defined by the closed inner edge 120a of the belt 120, 320. A portion of the inner surface of the second orifice 102 is defined by the closed inner edge 120a of the belt 120, 320.

[0063] The thickness of the insert 140, 340 and / or 150, 350 may be between 2 mm and 9 mm, and in particular between 3 mm and 7 mm. The thickness of the insert 140, 340 and / or 150, 350 is measured between the two longitudinal edges of the insert 140, 150, 340, 350. In particular, the thickness of the first insert 140, 340 may be between between 4% and 40% of a reference distance extending between the axis A of the first orifice 101, 301 and the closest point of the external surface of the belt 120, 320. This reference distance corresponds to the radius of the yoke comprising the first orifice 101. Thus, this reference distance corresponds to the radius of the yoke comprising the ring 130. The thickness of the second insert 150, 350 may be between 4% and 40% of the reference distance.

[0064] The thickness of the first insert 140 may be constant, as illustrated in Figures 4 and 5. The thickness of the first insert 140 is constant along the interface between the core 110 and the belt 120. Thus, the spacing between the first longitudinal edge 140a and the second longitudinal edge 140b of the first insert 140 is constant. Similarly, the thickness of the second insert 150 may be constant, as illustrated in Figures 4 and 5. The thickness of the first insert 140 is constant along the interface between the core 110 and the belt 120. Thus, the spacing between the first longitudinal edge 150a and the second longitudinal edge 150b of the second insert 150 is constant.

[0065] The thickness of the first insert 340 may also be variable, as illustrated in FIG. 6. The thickness of the first insert 340 is variable along the interface between the core 310 and the belt 320. Thus, the spacing between the first longitudinal edge 340a and the second longitudinal edge 340b of the first insert 340 is variable. In particular, the thickness of the first insert 340 may decrease from the first orifice 101. Thus, the thickness of the first insert 340 decreases from a portion of said first insert 340 adjacent to the orifice 101 to a portion of said first insert 340 remote from the first orifice 101. Thus, the spacing between the first longitudinal edge 340a and the second longitudinal edge 340b of the first insert 340 decreases from a portion of said first insert 340 adjacent to the orifice 101 to a portion of said first insert 340 remote from the first orifice 101. The decrease in thickness may be regular and / or continuous.

[0066] The thickness of the second insert 350 may also be variable, as illustrated in FIG. 6. The thickness of the second insert 350 is variable along the interface between the core 310 and the belt 320. Thus, the spacing between the first longitudinal edge 350a and the second longitudinal edge 350b of the second insert 350 is variable. In particular, the thickness of the second insert 350 may decrease from the first orifice 101. Thus, the thickness of the second insert 350 decreases from a portion of said second insert 350 adjacent to the orifice 101 to a portion of said second insert 350 remote from the first orifice 101. Thus, the spacing between the first longitudinal edge 350a and the second longitudinal edge 350b of the second insert 350 decreases from a portion of said second insert 350 adjacent to the orifice 101 to a portion of said second insert 350 remote from the first orifice 101. The decrease in thickness may be regular and / or continuous.

[0067] The first insert 140 and / or the second insert 150 may extend from the first orifice 101 to the second orifice 102, as illustrated in FIGS. 4 and 5. The closed inner edge 120a of the belt 120 is then maintained at a non-zero distance from the first and / or second longitudinal edge 110a and / or 110b of the core 110 over the entire length of said first and / or second longitudinal edge 110a and / or 110b. It is not departing from the scope of the invention if the first insert 140 and / or the second insert 150 extends from the first orifice 101 to the second orifice 102 and has a variable thickness (variant not illustrated). In this configuration, the thickness of the first insert 140 and / or the second insert 150 may decrease from the first and second orifices 101, 102 towards a central portion of said insert(s) remote from said first and second orifices 101, 102.Thus, the spacing between the first longitudinal edge and the second longitudinal edge of the insert(s) decreases from the portions of said insert(s) adjacent to the orifices 101, 102 to a central portion remote from said first and second orifices 101, 102. The insert(s) then have an hourglass shape. The first longitudinal edge and the second longitudinal edge then form an hourglass shape. The reduction in thickness may be regular and / or continuous.

[0068] The first insert 340 may open into a single orifice 301, as illustrated in FIG. 6. Preferably, the first insert 140, 340 extends from the first orifice 101, 301 over a first extension distance of between 80% and 220% of the reference distance. The second insert 150, 350 may extend from the first orifice 101, 301 to the second orifice 102. The second insert 150, 350 may open into a single orifice 101, 301. Preferably, the second insert 150, 350 extends from the first orifice 101, 301 over a second extension distance of between 80% and 220% of the reference distance.

[0069] Thus, the inserts 140, 150, 340, 350 which extend from the first orifice 101, 301 do not necessarily extend over the entire length of the interface between the core 110, 310 and the belt 120, 320. The closed internal edge 320a of the belt 320 is then in contact with the first and / or second longitudinal edge 310a and / or 310b of the core 310. In this configuration, the thickness of the insert(s) may decrease from a portion of said insert(s) adjacent to the first orifice to an end of said insert(s) remote from the first orifice. The reduction in thickness may be regular and / or continuous.

[0070] It is of course not outside the scope of the invention if the insert(s) open into a single orifice 301 and have a constant thickness (variant not illustrated).

[0071] The ring 130 and the additional ring 130bis can be made of metal. The ring 130 and the additional ring 130bis can also be made of composite material.

[0072] The core 110 and the belt 120 are made of composite material. Preferably, the core 110 and the belt 120 are made of organic matrix composite (OMC) material. The core 110 comprises a fibrous reinforcement densified by a matrix. The fibrous reinforcement of the core 110 is made by three-dimensional weaving. The fibrous reinforcement of the core 110 may be formed by carbon fibers. The belt 120 comprises a fibrous reinforcement densified by a matrix. The fibrous reinforcement of the belt 120 is made by three-dimensional weaving. The fibrous reinforcement of the belt 120 may be formed by carbon fibers. Preferably, the yarns used for the fibrous reinforcement of the belt 120 are of the same nature and material as the yarns used for the fibrous reinforcement of the core 110. By "three-dimensional weaving" is meant here a weaving method by which at least some of the warp yarns bind weft yarns over several weft layers.A reversal of roles between warp and weft is possible.

[0073] The fibrous reinforcements of the core 110 and the belt 120 are densified by the same matrix. Preferably, the fibrous reinforcements of the core 110 and the belt 120 are co-densified by a thermoplastic or thermosetting resin. The fibrous reinforcements of the core 110 and the belt 120 may be co-densified by an epoxy resin.

[0074] Inserts 140 and 150 are without three-dimensional weaving.

[0075] The material forming the inserts 140 and 150 may comprise the same matrix as that of the core 110 and the belt 120. The inserts 140 and 150 may be made solely of the matrix material of the core 110 and the belt 120. The inserts 140 and 150 may be made solely of resin, for example solid epoxy resin. The inserts 140 and 150 may be made of elastomer. The use of the elastomer allows the production of a very flexible insert, which makes it possible to further improve the resistance of the part in the face of peaks in the introduction of forces.

[0076] According to a preferred embodiment of the invention, the inserts 140 and 150 are formed by a superposition of fibrous layers produced by two-dimensional weaving and densified by a matrix. Thus, the inserts 140 and 150 are formed by a superposition of two-dimensional fibrous plies. The fibrous layers of the inserts 140 and 150 are preferably densified by the same matrix as that of the core 110 and the belt 120. The fibrous layers of the inserts 140 and 150 may be densified by an epoxy resin.

[0077] The inserts 140 and 150 can also be formed by a single fibrous layer made by two-dimensional weaving and densified by a matrix.

[0078] The fibers of the fibrous layers of the inserts 140 and 150 may be made of glass.

[0079] The first insert 140 may be formed by 1 to 10 fibrous layers made by two-dimensional weaving. Preferably, the first insert 140 is formed by 2 to 10 fibrous layers made by two-dimensional weaving. Similarly, the second insert 150 may be formed by 1 to 10 fibrous layers made by weaving two-dimensional. Preferably, the second insert 150 is formed by 2 to 10 fibrous layers produced by two-dimensional weaving.

[0080] The fibrous layers of the first insert 140 and / or the second insert 150 may have the following fiber orientations: ±45°, 0° / 90° and ±45° / 90°.

[0081] The first insert 140 may be made differently from the second insert 150. However, it is preferable that the first insert 140 and the second insert 150 are made in a similar manner to facilitate the manufacture of the part 100.

[0082] According to the method of the invention, a fibrous assembly is first produced comprising a core fibrous preform and a belt fibrous preform, the belt fibrous preform is arranged around the core fibrous preform so that the belt fibrous preform delimits at least one cylindrical space adjacent to the core fibrous preform. Said cylindrical space is intended to form the first orifice 101, 301. Another cylindrical space adjacent to the core fibrous preform may be intended to form the second orifice 102.

[0083] Figure 7 illustrates a core fiber preform 210 intended to form the core fiber reinforcement 110. As indicated previously, the core fiber preform 210 is made by three-dimensional weaving. The core fiber preform 210 can be made of carbon fibers.

[0084] The core fiber preform 210 comprises a first longitudinal edge 210a and a second longitudinal edge 210b opposite the first longitudinal edge 210b. The first longitudinal edge 210a and the second longitudinal edge 210b of the core fiber preform 210 are respectively intended to form the longitudinal edge 210a and the second longitudinal edge 210b of the core 110. The core fiber preform 210 further comprises at least one first curved edge 210c which connects the first longitudinal edge 210a to the second longitudinal edge 210b. The first curved edge 210c of the core fiber preform 210 is intended to form the first curved edge 110c of the core 110. In the example illustrated in FIG. 7, the core fiber preform 210 comprises a second curved edge opposite the first curved edge 210c, which connects the first longitudinal edge 210a to the second longitudinal edge 210b,

[0085] The fiber belt preform 220 is intended to form the fiber reinforcement of the belt 120. As indicated previously, the fiber belt preform 220 is made by three-dimensional weaving. The fiber belt preform 220 can be made of carbon fibers.

[0086] The fibrous assembly 200 is thus intended to form the fibrous reinforcement of the part 100 to be produced.

[0087] According to a first embodiment, the fiber belt preform is arranged so as to leave at least one gap between the fiber core preform and the fiber belt preform extending from the cylindrical space. Two gaps may extend between the fiber core preform and the fiber belt preform from the same cylindrical space, on either side of the fiber core preform.

[0088] According to a first variant, the fibrous assembly further comprises a superposition of fibrous layers.

[0089] Figures 7 to 9 illustrate an example of a method for manufacturing a part according to the invention, for the first variant of the first embodiment in which the inserts 140 and 150 are produced by superimposing fibrous layers. Figures 7 to 9 thus describe the production of a fibrous assembly 200 intended to be densified by the matrix. The fibrous assembly 200 is thus intended to form the fibrous reinforcement of the part 100 to be produced.

[0090] Figure 8 illustrates a first fibrous insert preform 240 of the first insert 140 and a second fibrous insert preform 250 of the second insert 150. The first fibrous insert preform 240 is intended to form the fibrous reinforcement of the first insert 140. The second fibrous insert preform 250 is intended to form the fibrous reinforcement of the second insert 150.

[0091] The first fibrous insert preform 240 is formed by a plurality of fibrous layers 241, 242, 243, 244 as described previously. A first fibrous layer 241 is arranged in contact with the core fibrous preform 210, as illustrated in Figure 8. The first fibrous layer 241 rests against the core fibrous preform 210. The first fibrous layer 241 is in contact with the first longitudinal edge 210a of the core fibrous preform 210. The following fibrous layers 242, 243 and 244 are superimposed in order on the first fibrous layer 241 until the last fibrous layer 244 is deposited.

[0092] The second insert fiber preform 250 is formed by a plurality of fiber layers 251, 252, 253, 254 as previously described. A first fiber layer 251 is disposed in contact with the core fiber preform 210, as illustrated in FIG. 8. The first fiber layer 251 rests against the core fiber preform 210. The first fiber layer 251 is in contact with the second longitudinal edge 210b of the core fiber preform 210. The following fiber layers 252, 253 and 254 are superimposed in order on the first fiber layer 251 until the last fiber layer 254 is deposited.

[0093] A belt fiber preform 220 is then arranged around the core fiber preform 210 and the insert fiber preforms 240 and 250 to obtain the fiber assembly 200, as illustrated in FIG. 9.

[0094] The belt fiber preform 220 comprises a closed inner edge 220a. The belt fiber preform 220 is disposed around the core fiber preform 210 and the insert fiber preforms 240 and 250. The closed inner edge 220a of the belt fiber preform 220 is disposed in contact with the insert fiber preforms 240 and 250. The closed inner edge 220a of the belt fiber preform 220 is disposed in contact with the last fiber layer 244 of the first insert fiber preform 240. The closed inner edge 220a of the belt fiber preform 220 is disposed in contact with the last fiber layer 254 of the second insert fiber preform 250.

[0095] According to a second variant of the first embodiment, the gap of the fibrous assembly is filled with an elastomeric material before the densification of said fibrous assembly. It is thus possible to arrange elastomeric inserts between the belt fiber preform and the core fiber preform before densification, then to proceed with the densification of the assembly. The elastomeric inserts thus form the inserts 140 and 150.

[0096] According to a third variant of the first embodiment, the gap of the fibrous assembly is filled only by the matrix material during densification. The insert of the final part can then be formed only by the matrix material. The gap filled only by the matrix material can also be removed in part or completely after densification. A filling material can then be introduced into the removed portion so as to obtain the insert. The filling material can be a resin, an elastomeric material or an adhesive joint.

[0097] According to a second embodiment, the fiber belt preform is in contact with the fiber core preform along the entire length of the first and second longitudinal edges. Thus, the fiber assembly obtained is free of interstices. The fiber assembly comprises only the fiber core preform and the fiber belt preform. The insert(s) are then formed after densification of the fiber assembly, by removing at least a portion of the fiber assembly densified by the matrix. A filling material is then introduced into the removed portion. The filling material may be a resin, an elastomeric material or an adhesive joint.

[0098] In all embodiments, in order to facilitate the positioning of the fiber belt preform 220 around the fiber core preform 210 and the possible fiber insert preforms 240 and 250, elements 51 and 52 may be used, as illustrated in FIG. 9. A first cylindrical element 51 may be disposed against the first curved edge 210c of the fiber core preform 210. The first cylindrical element 51 is thus disposed between the fiber core preform 210 and the fiber belt preform 220 so as to maintain the fiber belt preform 220 in the proper position. A second cylindrical member 52 may be disposed against the second curved edge of the core fiber preform 210. The second cylindrical member 52 is thus disposed between the core fiber preform 210 and the belt fiber preform 220 so as to maintain the belt fiber preform 220 in the proper position.

[0099] The first cylindrical element 51 makes it possible to define a cylindrical space adjacent to the fiber core preform 510, said cylindrical space being intended for form the first orifice. The second cylindrical element 52 makes it possible to define a cylindrical space adjacent to the fiber core preform 510, said cylindrical space being intended to form the second orifice.

[0100] The assembly of the fibrous assembly 200 can be carried out in any order.

[0101] The fibrous assembly 200 thus obtained is then densified by a matrix. For this purpose, the fibrous assembly 200 can be placed in a mold. Densification by the matrix can be carried out by the introduction of 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.

[0102] A composite material part is thus obtained, the fiber reinforcements of which are formed by the core fiber preform 210, the belt fiber preform 220 and by the possible insert fiber preforms 240 and 250 having been co-densified. The rings 130 and 130bis can then be added so as to obtain the mechanical part 100. It is of course not outside the scope of the invention if the rings 130 and 130bis are added to the fiber assembly 200 before densification by the matrix.

[0103] In the third variant of the first embodiment, in which the insert is formed solely by the matrix material without fibrous reinforcement, the belt fiber preform 220 may be kept at a distance from the core fiber preform 210 during densification, so that the gap formed between the core fiber preform 210 and the belt fiber preform 220 is filled with resin. The resin present in this gap will then make it possible to form the inserts 140 and 150.

[0104] It is also possible to arrange resin inserts between the fiber belt preform 220 and the fiber core preform 210 before densification, and then to proceed with the densification of the assembly. The resin inserts thus form the inserts 140 and 150. In this embodiment, the inserts 140 and 150 may be made in a resin different from the matrix used to densify the fiber belt 220 and core 210 preforms.

[0105] The part according to the invention 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 even a brake bar.

[0106] The part according to the invention thus has better mechanical properties than similar parts of the prior art.

[0107] When a part according to the prior art is loaded in tension, the end of the belt surrounding the orifice is first loaded, then the forces pass into the rest of the belt and into the core. This transfer of forces occurs progressively via the interface between the core and the belt with a stress peak, until the loading is homogeneous. A similar phenomenon occurs during compression loading. The part according to the invention makes it possible to better absorb and reduce this stress peak thanks to the presence of a flexible insert.

[0108] The expression "between ... and ..." must be understood as including the limits.

Claims

Claims

1. Mechanical part (100) comprising a core (110) comprising a fibrous reinforcement densified by a matrix, comprising at least one orifice adjacent to the core (110) and intended to be crossed by an axis to make a connection with another part, the core (110) comprising at least one curved edge (110c) partially delimiting the orifice, the mechanical part further comprising a belt (120) comprising a fibrous reinforcement densified by the matrix surrounding the core (110) and said at least one orifice, the part (100) being characterized in that at least one insert (140, 150) extending from the orifice is interposed between the core (110) and the belt (120).

2. The part (100) of claim 1, wherein the insert (140, 150) is a layer of matrix material.

3. Part (100) according to claim 1, in which the insert (140, 150) is made of elastomer.

4. Part (100) according to claim 1, in which the insert (140, 150) comprises a superposition of fibrous layers (241, 242, 243, 244, 251, 252, 253, 254) produced by two-dimensional weaving and densified by a matrix, the fibrous layers being superimposed on each other from the core (110) to the belt (120).

5. A part (100) according to any one of claims 1 to 4, wherein the matrix is an epoxy resin.

6. Part (100) according to any one of claims 1 to 5, in which the thickness of the insert (140, 150) is between 4% and 40% of a reference distance extending between the axis (A, A') of the orifice and the closest point of the external surface of the belt (120).

7. Part (100) according to any one of claims 1 to 6, in which the insert (140, 150) extends from the orifice over a distance of between 80% and 220% of a reference distance extending between the axis (A, A') of the orifice and the closest point of the external surface of the belt (120).

8. A part (100) according to any one of claims 1 to 7, wherein the thickness of the insert decreases from a portion of the insert adjacent the orifice to a portion of said insert remote from the orifice.

9. A part (100) according to any one of claims 1 to 8, the part further comprising at least one ring (130) disposed in the orifice and adjacent to the core (110).

10. Method for manufacturing a fibrous assembly (200) intended to form the fibrous reinforcement of a mechanical part (100) made of composite material, comprising: - the production by three-dimensional weaving of a fibrous core preform (210) and a fibrous belt preform (220), - arranging the belt fiber preform (220) around the core fiber preform (210) such that the belt fiber preform (220) defines a cylindrical space adjacent to the core fiber preform (210).

11. A method of manufacturing a fibrous assembly according to claim 10, wherein the arrangement of the belt fibrous preform (220) around the core fibrous preform (210) is carried out so as to leave at least one gap between the core fibrous preform (210) and the belt fibrous preform (220) extending from the cylindrical space.

12. A method of manufacturing a fibrous assembly (200) according to claim 11, wherein the gap is filled by a superposition of fibrous layers (241, 242, 243, 244, 251, 252, 253, 254) produced by two-dimensional weaving, the fibrous layers (241, 242, 243, 244, 251, 252, 253, 254) being superimposed on each other from the core fibrous preform (210) to the belt fibrous preform (220).

13. Method of manufacturing a mechanical part (100) comprising: - the manufacture of a fibrous assembly (200) according to any one of claims 10 to 12, - densifying the fibrous assembly (200) by a matrix while keeping the cylindrical space free of matrix, so as to obtain a part made of composite material comprising a core (110), a cylindrical orifice adjacent to the core (110), a belt (120) surrounding the core (110) and the cylindrical orifice, the final mechanical part (100) comprising at least one insert (140, 150) extending from the orifice between the core (110) and the belt (120).

14. A method of manufacturing a mechanical part (100) according to claim 13 attached to claim 11 or 12, comprising introducing the matrix material into the gap during densification.

15. A method of manufacturing a mechanical part (300) according to claim 13, the method further comprising: - removing at least one portion of the fibrous assembly densified by the matrix, said at least one removed portion extending from the cylindrical orifice (301) and separating the belt (320) from the core (310), - introducing a filling material into the at least one removed portion so as to obtain the at least one insert (340, 350).

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