Belted mechanical part including an interface insert

Abstract

Belted mechanical part comprising an interface insert The invention relates to a 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, and 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) extending from the orifice is interposed between the core (110) and the belt (120). Figure for abstract: Fig. 5

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] [Fig.l] shows a landing gear comprising two struts 1 and 1', respectively called main strut and lateral strut. These struts are articulated to the leg 4 of the landing gear and to the frame 5 of the landing gear. Each strut 1 and 1' is formed of two connecting rods, as illustrated in [Fig.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 from steel, aluminum or titanium alloys. In order to lighten these connecting rods, they can now be made from composite material. Indeed, the production of connecting rods from composite material makes it possible to produce connecting rods that are lighter than those made from metal while retaining good mechanical properties. Connecting rods made from composite material are thus easier to operate during operation of the landing gear and make it possible to reduce the mass 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 and then co-injected. [Fig. 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 has been found that, during operation, cracks F could appear on the connecting rod at the interface between the core A and the belt C, said cracks generally extending from the ring B, as illustrated in [Fig.3]. Statement of the invention

[0006] It was found that these cracks were caused by a high concentration of stresses at the interface point between the core, the belt and the orifice 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 expansion coefficients on either side of the interface, which can cause cracks to appear. Furthermore, it was found that these cracks could be favored by residual processing stresses. These residual stresses appear during cooling of the part during its manufacturing process, and depend on the difference in expansion coefficient between the core and the belt.

[0007] The invention therefore aims to avoid 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, the transmission of forces between the core and the belt is acted upon and the distance over which said forces are transmitted can be increased. The risk of cracking is thus reduced.

[0010] According to a first 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 matrix of the core and the belt, which makes the mechanical part easy to manufacture.

[0012] According to a second 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 one another 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°, 0790° or ±45790°.

[0015] Indeed, such orientations ensure an optimal improvement in 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 point closest to the external surface of the belt.

[0018] The thicker the insert, the more it will be able to reduce the stresses at the interface between the core and the belt. However, an insert that is too thick is 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 point closest to the external surface of the belt.

[0020] Indeed, it has been 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 part further comprises at least one ring arranged in the orifice and adjacent to the core.

[0022] 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:

[0023] - the production by three-dimensional weaving of a fibrous core preform and a fiber belt preform,

[0024] - the arrangement of the belt fiber preform around the fiber preform core such that the fiber belt preform defines a cylindrical space adjacent to the fiber core preform and such as to leave at least one gap between the fiber core preform and the fiber belt preform extending from the cylindrical space.

[0025] According to a particular 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.

[0026] Method of manufacturing a mechanical part comprising:

[0027] - the manufacture of a fibrous assembly according to the method described above,

[0028] - the densification of the fibrous assembly by a matrix while preserving the cy space matrix-free lindric, so as to obtain a mechanical part made of composite material comprising a core, a cylindrical orifice adjacent to the core, a belt surrounding the core and the cylindrical orifice and at least one insert extending from the orifice between the core and the belt. Brief description of the drawings

[0029] [Fig.l] [Fig.l] is a schematic view of a landing gear.

[0030] [Fig.2] [Fig.2] is a schematic view of a landing gear strut of [Fig.l].

[0031] [Fig.3] [Fig.3] is a partial schematic view of a connecting rod according to the prior art having cracks.

[0032] [Fig.4] [Fig.4] is a schematic sectional view of a connecting rod with an insert.

[0033] [Fig.5] [Fig.5] is a detailed view of the connecting rod of [Fig.4].

[0034] [Fig.6] [Fig.6] is a perspective view of a fiber preform of the core of the connecting rod of figures 4 and 5.

[0035] [Fig.7] [Fig.7] is a sectional view of the fibrous core preform on which are arranged layers of two-dimensional fabric intended to form the fibrous reinforcement of the insert.

[0036] [Fig.8] [Fig.8] is a sectional view of the fiber reinforcement of the connecting rod of Figures 4 and 5. Description of the embodiments

[0037] Figures 4 and 5 illustrate an example of a mechanical part 100 according to the invention. The part 100 comprises a core 110, a belt 120 and a first orifice and a second orifice in which rings 130 and 130bis are respectively mounted. It is of course not departing from the scope of the invention if the part does not comprise a ring. In accordance with the invention, the part 100 further comprises a first insert 140 and a second insert 150. The part 100 as illustrated has only single yokes. It is of course not departing from 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 AL

[0038] The first orifice is delimited by an internal surface. The second orifice is delimited by an internal surface. The first orifice is open. The second orifice is open.

[0039] The core 110 comprises a first longitudinal edge 110a and a second longitudinal edge 110b opposite the first longitudinal edge 110a. The core 110 further comprises at least one first curved edge 110c which connects the first longitudinal edge 110a to the second longitudinal edge 110b. The first curved edge 110c partially delimits the first orifice. Thus, a portion of the internal surface of the first orifice is defined by the first curved edge 110c of the core 110. In the example illustrated in [Fig.4], the core 110 comprises a second curved edge opposite the first curved edge 110c, which connects the first longitudinal edge 110a to the second longitudinal edge 110b. The second curved edge partially delimits the second orifice. Thus, a portion of the internal surface of the second orifice is defined by the second curved edge of the core 110.

[0040] 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. 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.

[0041] 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 outer surface of the additional ring 130bis may correspond to the inner surface of the second orifice. The outer 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 outer 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.

[0042] The first insert 140 comprises a first longitudinal edge 140a and a second longitudinal edge 140b opposite the first longitudinal edge 140a. The first longitudinal edge 140a of the first insert 140 is in contact with the first longitudinal edge 110a of the core 110. The first insert 140 further comprises a transverse edge which connects the first longitudinal edge 140a to the second longitudinal edge 140b of said first insert 140. The transverse edge of the first insert 140 partially delimits the first orifice. Thus, a portion of the internal surface of the first orifice is defined by the transverse edge of the first insert 140. The transverse edge of the first insert 140 is in contact with the ring 130. The transverse edge of the first insert 140 is in contact with the external surface 130b of the ring 130. The transverse edge of the first insert 140 matches the external surface 130b of the ring 130.

[0043] The second insert 150 comprises a first longitudinal edge 150a and a second longitudinal edge 150b opposite the first longitudinal edge 150a. The first longitudinal edge 150a of the second insert 150 is in contact with the second longitudinal edge 110b of the core 110. The second insert 150 further comprises a transverse edge which connects the first longitudinal edge 150a to the second longitudinal edge 150b of said second insert 150. The transverse edge of the second insert 150 partially delimits the first orifice. Thus, a portion of the internal surface of the first orifice is defined by the transverse edge of the second insert 150. The transverse edge of the second insert 150 is in contact with the ring 130. The transverse edge of the second insert 150 is in contact with the external surface 130b of the ring 130. The transverse edge of the second insert 150 matches the external surface 130b of the ring 130.

[0044] In the example illustrated in Figures 4 and 5, the part 100 comprises two inserts 140 and 150. 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.

[0045] The belt 120 surrounds the core 110 and the orifice(s). Thus, the belt 120 surrounds the ring(s) 130, 130bis. The belt 120 partially delimits the orifice(s). The belt 120 comprises a closed internal edge 120a. The belt 120 comprises an external surface opposite the closed internal edge 120a. The closed inner edge 120a of the belt 120 is in contact with the first insert 140. The closed inner edge 120a of the belt 120 is in contact with all the inserts 140, 150. The closed inner edge 120a of the belt 120 is in contact with the second longitudinal edge 140b of the first insert 140. The closed inner edge 120a of the belt 120 is in contact with the second longitudinal edge 150b of the second insert 150. The closed inner edge 120a of the belt 120 is in contact with the external surface 130b of the ring 130. The closed inner edge 120a of the belt 120 is in contact with the external surface of the additional ring 130bis.The closed inner edge 120a partially delimits the first orifice and the second orifice. Thus, a portion of the inner surface of the first orifice is defined by the closed inner edge 120a of the belt 120. A portion of the inner surface of the second orifice is defined by the closed inner edge 120a of the belt 120.

[0046] The thickness of the insert 140 and / or 150 may be between 2 mm and 9 mm, and in particular between 3 mm and 7 mm. The thickness of the insert 140 and / or 150 is measured between the two longitudinal edges of the insert 140 / 150. In particular, the thickness of the first insert 140 may be between 4% and 40% of a reference distance extending between the axis A of the ring 130 and the closest point of the external surface of the belt 120. This reference distance corresponds to the radius of the yoke comprising the ring 130. The thickness of the second insert 150 may be between 4% and 40% of the reference distance. Preferably, the first insert 140 extends from the ring 130 over a first extension distance of between 80% and 220% of the reference distance. Thus, the inserts which extend from the ring 130 do not necessarily extend over the entire length of the interface between the core 110 and the belt 120.

[0047] The ring 130 and the additional ring 130bis may be made of metal. The ring 130 and the additional ring 130bis may also be made of composite material.

[0048] The core 110 and the belt 120 are made of a composite material. Preferably, the core 110 and the belt 120 are made of an 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 threads used for the fibrous reinforcement of the belt 120 are of the same nature and made of the same material as the threads 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 threads bind weft threads over several weft layers.A reversal of roles between warp and weft is possible.

[0049] 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.

[0050] Inserts 140 and 150 do not have three-dimensional weaving.

[0051] 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 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.

[0052] 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.

[0053] The inserts 140 and 150 can also be formed by a single fibrous layer produced by two-dimensional weaving and densified by a matrix.

[0054] The fibers of the fibrous layers of the inserts 140 and 150 may be made of glass.

[0055] 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 two-dimensional weaving. Preferably, the second insert 150 is formed by 2 to 10 fibrous layers made by two-dimensional weaving.

[0056] 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°.

[0057] 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.

[0058] Figures 6 to 8 illustrate an example of a method for manufacturing a part according to the invention, for the embodiment in which the inserts 140 and 150 are produced by superimposing fibrous layers. Figures 6 to 8 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.

[0059] [Fig.6] illustrates a fibrous core preform 210 intended to form the fibrous reinforcement of the core 110. As indicated previously, the fibrous core preform 210 is made by three-dimensional weaving. The fibrous core preform 210 can be made of carbon fibers.

[0060] 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.6], the core fiber preform 210 comprises a second curved edge opposite the first curved edge 210c, which connects the first longitudinal edge 210a to second longitudinal edge 210b.

[0061] [Fig.7] 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.

[0062] The first insert fiber preform 240 is formed by a plurality of fiber layers 241, 242, 243, 244 as previously described. A first fiber layer 241 is disposed in contact with the core fiber preform 210, as illustrated in [Fig.7]. The first fiber layer 241 rests against the core fiber preform 210. The first fiber layer 241 is in contact with the first longitudinal edge 210a of the core fiber preform 210. The following fiber layers 242, 243 and 244 are superimposed in order on the first fiber layer 241 until the last fiber layer 244 is deposited.

[0063] The second insert fiber preform 250 is formed by a plurality of fiber layers 251, 252, 253, 254 as described previously. A first fiber layer 251 is arranged in contact with the core fiber preform 210, as illustrated in [Fig.7]. 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.

[0064] 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.8].

[0065] The fibrous belt preform 220 is intended to form the fibrous reinforcement of the belt 120. As indicated previously, the fibrous belt preform 220 is produced by three-dimensional weaving. The fibrous belt preform 220 can be produced from carbon fibers.

[0066] 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.

[0067] In order to facilitate the positioning of the belt fiber preform 220 around the core fiber preform 210 and the insert fiber preforms 240 and 250, elements 51 and 52 may be used, as illustrated in [Fig. 8]. A first cylindrical element 51 may be disposed against the first curved edge 210c of the core fiber preform 210. The first cylindrical element 51 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. 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.

[0068] 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 to 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.

[0069] The assembly of the fibrous assembly 200 can be carried out in any order.

[0070] The fibrous assembly 200 thus obtained is then densified by a matrix. For this purpose, the fibrous assembly 200 can be arranged 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.

[0071] A composite material part is thus obtained, the fiber reinforcements of which formed by the core fiber preform 210, the belt fiber preform 220 and the insert fiber preforms 240 and 250 have 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.

[0072] In the case where the insert is formed solely by the matrix material without fibrous reinforcement, the belt fiber preform 220 can 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 the resin. The resin present in this space will then make it possible to form the inserts 140 and 150.

[0073] It is also conceivable to have resin inserts between the fiber belt preform 220 and the fiber core preform 210 before densification, then to densify the assembly. The resin inserts thus form the inserts 140 and 150. In this embodiment, the inserts 140 and 150 may be made of a resin different from the matrix used to densify the fiber belt 220 and core 210 preforms.

[0074] It is also conceivable to arrange elastomer inserts between the fiber belt preform 220 and the fiber core preform 210 before densification, then to proceed with densification of the assembly. The elastomer inserts thus form the inserts 140 and 150.

[0075] 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.

[0076] The part according to the invention thus has better mechanical properties than similar parts of the prior art.

[0077] 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 is done 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.

[0078] 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, and 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. The part (100) of claim 4, wherein the fibrous layers (241, 242, 243, 244, 251, 252, 253, 254) have fiber orientations of ±45°, 0790° or ±45790°.

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

7. Part (100) according to any one of claims 1 to 6, 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).

8. Part (100) according to any one of claims 1 to 7, 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).

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, including: - the production by three-dimensional weaving of a fibrous core preform (210) and a fibrous belt preform (220), - arranging the fibrous belt preform (220) around the fibrous core preform (210) such that the fibrous belt preform (220) defines a cylindrical space adjacent to the fibrous core preform (210) and such as to leave at least one gap between the fibrous core preform (210) and the fibrous belt preform (220) extending from the cylindrical space.

11. A method of manufacturing a fibrous assembly (200) according to claim 10, 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).

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

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