A belted connecting piece made of composite material, including a non-symmetrical ring

Abstract

A belted connecting piece made of composite material comprising a non-symmetrical ring. The invention relates to a connecting piece (100) comprising a core (110) made of composite material including a fibrous reinforcement densified by a matrix, a ring (150) having a first portion (153) cooperating with an end (111) of the core (110), and a belt (120) made of composite material including a fibrous reinforcement densified by a matrix. The composite belt (120) surrounds the core and a second portion (154) of the ring (150). The second portion (154) of the ring (150) has a thickness (E154) less than the thickness (E153) of the first portion (153) of the ring. Figure for the abstract: Fig. 4

Description

Title of the invention: Belted connecting piece made of composite material comprising a non-symmetrical ring. 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. Previous technique

[0002] Fig. 1 shows a landing gear comprising two struts 1 and 1', respectively referred to as the main strut and the lateral strut. These struts are articulated to the landing gear leg 4 and the landing gear frame 5. Each strut 1 and 1' is formed of two connecting rods, as illustrated in Fig. 2. Thus, 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 pivot pins. Such connecting rods are subjected in operation to significant mechanical stresses, primarily in compression and tension, oriented along the longitudinal axis of the part.

[0003] These connecting rods were usually made of steel, aluminum, or titanium alloys. To reduce their weight, they can now be made of composite material. Indeed, manufacturing connecting rods from composite material allows for lighter rods than those made of metal while maintaining good mechanical properties. Composite connecting rods are thus easier to operate during landing gear operation and reduce the aircraft's mass, thereby lowering fuel consumption.

[0004] US2007007386 and US2015239553 describe a connecting rod made of composite material, comprising a core surrounded by a belt, the fibrous reinforcements of the core and the belt being produced by three-dimensional (3D) weaving and then co-injected. The connecting rod has an opening at each of its ends intended to contact a shaft to transfer the tensile and compressive forces of the connecting rod and forming a yoke allowing the connecting rod to be articulated with other parts.

[0005] To improve the mechanical strength around each yoke, a ring made of metallic material, for example titanium, is inserted and bonded into the yoke's opening. Such a ring also has the advantage of allowing repair by machining in a homogeneous material, which is less sensitive than composite materials. The inserted ring is generally axisymmetric.

[0006] In the case of a reinforced composite slab as described in documents US2007007386 and US2015239553, the composite material around the axis is not homogeneous in the plane perpendicular to the axis / orifice. Indeed, the orifice is formed on half of its contour by a first fibrous preform of the slab produced by 3D weaving, the out-of-plane direction of which is normal to the edge of the orifice, and on the other half of its contour by a second fibrous preform of the core produced by 3D weaving, the warp or weft yarn direction of which is perpendicular to the axis and oriented in alignment with the two orifices of the slab.

[0007] The interface between these two preforms near the orifice is subjected to high stress during tensile and compressive loading of the caps formed by co-injected portions of these two fibrous preforms. An axisymmetric ring does not allow for optimization of the loading level at the interface of the co-injected fibrous preforms near the orifice of the cap.

[0008] US patent 2017-152886 discloses a composite material connecting part comprising a yoke machined from a composite material and incorporating a ring with a non-axisymmetric shape but with double symmetry about two perpendicular planes. This shape improves the mechanical strength of the yoke. Indeed, the mechanical load on a shaft / yoke connection is not homogeneous in terms of load and intensity at the edge of the hole in the yoke. However, this solution is only suitable for a yoke whose composite material consists of a homogeneous fibrous reinforcement in the plane of a layered plies or a weave. In fact, in the case of a composite material connecting part comprising a core surrounded by a band, the use of a non-axisymmetric ring such as that described in US patent 2017-152886 would modify the tensile mechanical load on the band as well as the mode and zone of failure.Furthermore, the use of such a ring can lead to small bend radii for the wires wound around it, thus increasing the risk of uncontrolled wire waviness.

[0009] There is, therefore, a need for a solution to improve the mechanical resistance at the level of the orifice(s) intended to transfer the tensile and compressive forces of a connecting part made of composite material formed from a fibrous core surrounded by a fibrous belt. Description of the invention

[0010] To this end, the invention proposes a connecting piece comprising a core made of composite material including a fibrous reinforcement densified by a matrix, at least a first ring having a first portion cooperating with a first end of the core and a belt made of composite material including a reinforcement fibrous densified by a matrix, the composite material belt surrounding the core and a second portion of said at least a first ring, each ring defining an orifice intended to be traversed by an axis to make a connection with another part, the part being characterized in that the second portion of said at least a first ring has a thickness less than the thickness of the first portion of said ring.

[0011] The difference in thickness between the portions of the ring located on the web and belt sides respectively improves the mechanical strength of the interface between the web and the belt at the orifice that houses the ring. Furthermore, the portion of the ring located on the web side has a greater thickness, which increases resistance to deformation during compressive loading of the part. If the ring is bonded, its retention in the recess between the web and the belt is improved by the presence of a larger bonding surface.

[0012] According to a feature of the connecting piece of the invention, the second portion of said at least a first ring has a constant thickness. This makes it possible to avoid altering the tensile mechanical load of the belt and to maintain the usual mode and zone of failure with a completely symmetrical ring. In addition, the second portion of the outer surface of the ring has an arc-shaped form allowing for a gradual curvature of the belt. This avoids small radii of curvature that could lead to the appearance of uncontrolled undulations in the fibers of the preformed fibrous belt.

[0013] According to another feature of the connecting piece of the invention, the first portion of said at least a first ring has a variable thickness.

[0014] According to another feature of the connecting piece of the invention, the thickness of the first portion of said at least a first ring varies from 2 mm to 6 mm or from 2 mm to 45 mm.

[0015] According to another feature of the connecting piece of the invention, said at least one first ring comprises a flat present at least between one end of the first portion and one end of the second portion of said at least one first ring.

[0016] According to another feature of the connecting piece of the invention, said connecting piece further comprises a second ring having a first portion cooperating with a second end of the core and the belt, the belt surrounding the core and a second portion of the second ring, said second ring defining an orifice intended to be traversed by a shaft to establish a connection with another piece, the second portion of the second ring having a thickness less than the thickness of the first portion of said second ring, the orifice defined by the second ring being of the same dimension or of a different dimension than the dimension of the orifice defined by the first ring.

[0017] The invention also relates to a method for manufacturing a connecting part made of composite material, comprising: - the production, by three-dimensional weaving, of a fibrous core preform and a fibrous belt preform, - the arrangement of the fibrous belt preform around the fibrous core preform so as to form at least one housing between a first end of the fibrous core preform and the fibrous belt preform, - the co-densification of the fibrous core preform and the fibrous belt preform by a matrix so as to obtain a connecting piece in composite material comprising a core, a belt and at least one first housing present between a first end of the core and the belt, - the bonding of at least one first ring in said at least one first housing of the connecting piece made of composite material, said at least one ring comprising a first portion cooperating with a first end of the core and a second portion cooperating with a first closed inner edge of the belt, or - the production, by three-dimensional weaving, of a fibrous core preform and a fibrous belt preform, - the arrangement of the fibrous belt preform around the fibrous core preform and at least a first ring comprising a first portion cooperating with a first end of the core preform and a second portion cooperating with a first edge of the belt preform, - the co-densification of the fibrous preform of the core and the fibrous preform of the belt by a matrix so as to obtain a connecting piece in composite material comprising a core, a belt and at least one first ring present between a first end of the core and a first edge of the belt, characterized in that the second portion of said at least one first ring has a thickness less than the thickness of the first portion of said at least one first ring.

[0018] According to a feature of the method of the invention, the second portion of said at least a first ring has a constant thickness.

[0019] According to another feature of the method of the invention, the first portion of said at least a first ring has a variable thickness.

[0020] According to another feature of the method of the invention, the thickness of the first portion of said at least a first ring varies from 2 mm to 6 mm or from 2 mm to 45 mm.

[0021] According to another feature of the method of the invention, said at least one first ring comprises a flat present at least between one end of the first portion and one end of the second portion of said at least one ring.

[0022] According to another feature of the method of the invention, it further comprises: - the bonding of a second ring in a second housing of the composite material connecting piece, the second ring comprising a first portion cooperating with a second end of the core and a second portion cooperating with a second closed inner edge of the belt, or - the co-densification of the fibrous preform of the core and the fibrous preform of the belt by a matrix so as to obtain a connecting piece in composite material comprising a core, a belt and a first ring present between a first end of the core and a first edge of the belt and a second ring present between a second end of the core and a second edge of the belt. Brief description of the drawings

[0023] [Fig-1] The [Fig.1] is a schematic view of a landing gear.

[0024] [Fig.2] Fig.2 is a schematic view of a landing gear strut of the [Fig.l].

[0025] [Fig.3] Fig.3 is a schematic cross-sectional view of a connecting rod according to a mode of realization of the invention.

[0026] [Fig.4] Fig.4 is a detailed view of the connecting rod of Fig.3 fitted with a ring having a first type of form.

[0027] [Fig. 5] [Fig. 5] is a detailed view of the connecting rod of [Fig. 3] showing a ring having a second type of shape.

[0028] [Fig. 6] Fig. 6 is a detailed view of the connecting rod of Fig. 3 fitted with a ring having a third type of form.

[0029] [Fig.7] Fig.7 is a perspective view of a fibrous preform of the core of the connecting rod of figures 3 and 4.

[0030] [Fig.8] Fig.8 is a cross-sectional view of the fibrous reinforcement of the connecting rod in Figures 3 and 4. Description of the implementation methods

[0031] Figures 3 and 4 illustrate an example of a connecting piece 100 made of composite material according to the invention. The piece 100 comprises a core 110 and a band 120 together defining a first housing 130 and a second housing 140 in which rings 150 and 160 are mounted, respectively. In the example illustrated in [Fig. 3], the piece 100 comprises two housings in each of which a ring is mounted. The invention remains within the scope of the invention if the connecting piece does not include only one housing with a ring. Similarly, part 100 as illustrated has only single clevises. The invention remains within the scope of invention if the mechanical part has double clevises, as is the case, for example, with the parts illustrated in document US2007007386.

[0032] The first dwelling 130 is delimited by an internal surface 131 while the second dwelling 140 is delimited by an internal surface 141.

[0033] The web 110 includes a first curved end 111 which delimits a portion of the first housing 130. Thus, a portion of the internal surface 131 of the first housing 130 is defined by the first curved end 111 of the web 110. In the example illustrated in [Fig. 3], the web 110 includes a second curved end 112 opposite the first curved end 111. The second curved end 112 delimits a portion of the second housing 140. Thus, a portion of the internal surface 141 of the second housing 140 is defined by the second curved end 112 of the web 110.

[0034] The belt 120 surrounds the core 110 and the first and second housings 130 and 140. More specifically, the belt 120 includes a first closed inner edge 121 which delimits the remainder of the first housing 130 from the first curved end 111 of the core 110 and a second closed inner edge 122 which delimits the remainder of the second housing 140 from the second curved end 112 of the core 110.

[0035] The ring 150 comprises an inner surface 151 and an outer surface 152 ([Fig. 4]). The ring 150 comprises a first portion 153 cooperating with the first curved end 111 of the core 110 and a second portion 154 surrounded by and cooperating with the first closed inner edge 121 of the belt 120. In other words, the first curved end 111 of the core 110 is in contact with a first portion 152a of the outer surface 152 of the ring 150 located at the level of the first portion 153 of the ring 150, while the first closed inner edge 121 of the belt 120 is in contact with a second portion 152b of the outer surface 152 of the ring 150 located at the level of the second portion 154 of said ring.

[0036] In accordance with the invention and as illustrated in [Fig. 4], the second portion 154 of the ring 150 has a thickness Ei54 that is less than the thickness Ei53 of the first portion 153 of the ring. The thickness Ei53 of the first portion 153 of the ring 150 gradually increases from each of its two junctions 153a and 153b with the second portion 154 up to a median plane Pi53 located equidistant from the two junctions 153a and 153b along a circumferential direction Di50 of the ring 150, where the thickness of the first portion reaches a maximum value Ei53max. The first portion 153 of the ring therefore exhibits symmetry along the median plane Pi53, while the ring 150 has an overall non-axisymmetric shape.

[0037] The asymmetry of the ring 150 due to the difference in thickness between the first and second portions 153 and 154 improves the mechanical strength of the interface between the web 110 and the belt 120 at the first housing 130 of the ring 150. Above a certain loading level, the force flow between the web 110 and the belt 120 can cause decohesion in a sensitive area located just after the contact zone between the belt 120 and the ring 150 and corresponding to the beginning of the contact between the internal surface 131 of the first housing 130 and the ring 150. By increasing the contact area between the web 110 and the extra thickness of the first portion 153 of the ring 150, it is possible to reduce the force flow in this sensitive area.

[0038] The resistance to deformation of the connecting piece 100 during compressive loads on it is significantly improved by the extra thickness of the first portion 153 of the ring 150 located on the side of the web 100. If the ring is glued, its hold in the first housing 130 is improved by the presence of a larger bonding surface on the side of the first portion 153.

[0039] Preferably, and as in the example described here, the thickness Ei54 of the second portion 154 is constant along its entire length. In this case, the second portion 154 of the ring exhibits symmetry about a median plane Pi54, while the ring 150 has an overall non-axisymmetric shape. This avoids altering the tensile mechanical load on the belt and preserves the usual failure mode and zone of a fully symmetrical ring.

[0040] Still in the case where the thickness Ei54 of the second portion 154 is constant over the whole of said second portion, the second portion 152b of the external surface 152 of the ring 150 has an arc-shaped form allowing a progressive curvature of the belt 120 at the level of the first closed inner edge 121. This avoids small radii of curvature likely to cause the appearance of uncontrolled undulations of the fibers of the fibrous preform of the belt.

[0041] The same characteristics as those described above for ring 150 These provisions also apply to the ring 160, which, according to the invention, comprises first and second portions 163 and 164. The second portion 164 of the ring 160 has a thickness less than the thickness of the first portion 163 of said ring. The rings 150 and 160 define openings intended to be traversed by axes A and A', respectively, to establish a connection with another part.

[0042] In the embodiment described in Figures 3 and 4, the thickness of the first portion of the rings 150 and 160 can vary from 2 mm for its minimum thickness up to 6 mm for its maximum thickness without this being limiting, the thickness of the first portion can vary over a larger range.

[0043] Figure 5 illustrates another embodiment of the connecting piece 100 that differs from that described in Figure 4 in that a ring 250 is used, the first portion 253 of which varies over a thickness E253 greater than that of the first portion 153 of the ring 150, and in that the shape of the first curved end 111 of the web 110 in contact with a first portion 252a of the external surface 252 of the ring 250 at the level of the first portion 253 of the ring 250 has a more curved shape in order to adapt to the more pronounced shape of the first portion 253. The contact surface between the web 110 and the excess thickness of the first portion 253 of the ring 250 is even greater here, which consequently makes it possible to further reduce the stress flow in the sensitive area located just after the area contact between the belt and the ring at the point where the contact between the inner surface of the first housing and the ring begins is this sensitive area.According to one embodiment, the contact area between the core and the extra thickness of the first portion of the ring can also be increased by creating shape effects on the external surface of the first portion of the ring and complementary shape effects on the surface of the part of the core in contact with the first portion of the ring. These shape effects can, in particular, correspond to undulations, sinusoids, or crenellations.

[0044] As with the ring 150 described previously, the ring 250 comprises an inner surface 251 and a second portion 254 surrounded and cooperating with the first closed inner edge 121 of the belt 120. The second portion 254 of the ring 150 has a thickness E254 that is less than the thickness E253 of the first portion 253 of the ring. The thickness E253 of the first portion 253 of the ring 250 gradually increases from each of its two junctions 253a and 253b with the second portion 254 up to a median plane P233 located equidistant from the two junctions 253a and 253b along a circumferential direction D250 of the ring 250 where the thickness of the first portion reaches a maximum value E253max. The first portion 153 of the ring therefore has a symmetry along the median plane P233 while the ring 250 has an overall non-axisymmetric shape.The thickness of the first portion 253 of the ring 250 can vary from 2 mm for its minimum thickness to 45 mm for its maximum thickness E253max without this being limiting, the thickness of the first portion can vary over a greater or lesser range.

[0045] Preferably, and as in the example described here, the thickness E254 of the second portion 254 is constant over the entire length of said second portion. The second In this case, portion 254 of the ring exhibits symmetry along a median plane P254, while the ring 250 has an overall non-axisymmetric shape. Also in this case, the second portion 252b of the external surface 252 of the ring 250 has an arc-shaped form, allowing for a gradual curvature of the belt 120 at the first closed inner edge 121.

[0046] The other parts of the core 100, the belt 120 and the ring 250 being identical to those already described above in relation to [Fig.4], they are not described again here for the sake of simplification.

[0047] Figure 6 illustrates another embodiment of the connecting piece 100 that differs from that described in Figure 4 in that it uses a ring 350 comprising at least one flat between one end of the first portion and one end of the second portion of the ring. More precisely, and as illustrated in Figure 6, the ring 350 has a first flat 355 located between the upper end of the first portion 353 and the upper end of the second portion 354 of the ring 350, and a second flat 356 located between the lower end of the first portion 353 and the lower end of the second portion 354 of the ring 350. The flat allows adjustment of the position of the interface zone between the web and the belt. Indeed, it may be advantageous to locate the critical interface zone at a different point than where there is the greatest deformation of the belt, which results in a significant opening stress.This is a means of optimizing the decoupling of the effects of constraints that cause decohesion.

[0048] As with the ring 150 described previously, the ring 350 includes an internal surface 351. The second portion 354 of the ring 350 has a thickness E354 that is less than the thickness E353 of the first portion 353 of the ring. The thickness E353 of the first portion 353 of the ring 350 gradually increases from each of its two junctions 353a and 353b with the second portion 354 until it reaches a median plane P353 located equidistant from the two junctions 253a and 253b along a circumferential direction D350 of the ring 350, where the thickness of the first portion reaches a maximum value E353max. The first portion 353 of the ring therefore exhibits symmetry about the median plane P353, while the ring 350 has an overall non-axisymmetric shape.The thickness of the first portion 353 of the ring 350 can vary from 2 mm for its minimum thickness to 6 mm for its maximum thickness E253max without this being limiting, the thickness of the first portion being able to vary over a wider range.

[0049] Preferably, and as in the example described here, the thickness E354 of the second portion 354 is constant over the entire length of said second portion. The second portion 354 of the ring then exhibits symmetry along a plane in this case. median P354 while the ring 350 has an overall non-axisymmetric shape. Also in this case, the first portion 352a of the external surface 352 of the ring 350 has an arc-shaped form allowing a progressive curvature of the belt 120 at the level of the first closed inner edge 121.

[0050] The other parts of the core 100, the belt 120 and the ring 350 being identical to those already described above in relation to [Fig.4], they are not described again here for the sake of simplification.

[0051] The rings 150, 160, 250 and 350 can be made of metal, and in particular of titanium. An additional ring (not shown in Figures 4 to 6), for example made of copper or bronze alloy, can be interposed between the internal surface 151, 251, 351 of the rings 150, 250 and 350 respectively and a shaft used to create a connection with another part.

[0052] 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). The core 110 comprises a fibrous reinforcement densified by a matrix. The fibrous reinforcement of the core 110 is produced by three-dimensional weaving. The fibrous reinforcement of the core 110 may be formed from carbon fibers. The belt 120 comprises a fibrous reinforcement densified by a matrix. The fibrous reinforcement of the belt 120 is produced by three-dimensional weaving. The fibrous reinforcement of the belt 120 may be formed from 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 in 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.

[0053] 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.

[0054] Figures 7 and 8 illustrate an example of a manufacturing process for a connecting part according to the invention. Figures 7 and 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 connecting part 100 to be produced.

[0055] Figure 7 illustrates a fibrous core preform 210 intended to form the fibrous reinforcement of the core 110. As previously stated, the fibrous core preform 210 is produced by three-dimensional weaving. The fibrous core preform 210 can be made of carbon fibers.

[0056] The fibrous core preform 210 comprises at least a first curved end preform portion 211 intended to form the first curved end 111 of the core 110. In the example illustrated in [Fig.7], the fibrous core preform 210 includes a second curved end preform part 212 intended to form the second curved end 112 of the core 110.

[0057] A fibrous belt preform 220 is then placed around a fibrous core preform 210, as illustrated in [Fig. 8]. The fibrous belt preform 220 is intended to form the fibrous reinforcement of the belt 120. As previously mentioned, the fibrous belt preform 220 is produced by three-dimensional weaving. The fibrous belt preform 220 can be made of carbon fibers.

[0058] The fibrous belt preform 220 comprises a first part of a closed inner edge preform 221 intended to form the first closed inner edge 121 of the belt 120 and a second part of a closed inner edge preform 222 intended to form the second closed edge 122 of the belt 120.

[0059] To facilitate the positioning of the belt fiber preform 220 around the core fiber preform, conforming elements 51 and 52 can be used, as illustrated in [Fig. 8]. A first conforming element 51, having the shape of the first recess 130 of the connecting piece 100, can be positioned against the first curved end preform portion 211 of the core fiber preform 210. The first conforming element 51 is thus positioned between the core fiber preform 210 and the belt fiber preform 220 so as to hold the belt fiber preform 220 in the correct position. A second conforming element 52, having the shape of the second recess 140 of the connecting piece 100, can be positioned against the second curved end preform portion 212 of the core fiber preform 210.The second conformation element 52 is thus arranged between the core fibrous preform 210 and the belt fibrous preform 220 so as to maintain the belt fibrous preform 220 in the proper position.

[0060] The resulting fibrous assembly 200 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 achieved by introducing a resin, such as an epoxy resin, followed by crosslinking if it is a thermosetting resin or by cooling if it is a thermoplastic resin. The matrix can be formed by resin transfer molding, a technique known per se.

[0061] This results in a composite material part, the fibrous reinforcements of which, formed by the core fiber preform 210 and the belt fiber preform 220, have been co-densified. The rings 150 and 160 can then be added to obtain the connecting piece 100. In this case, the ring 150 is bonded to the inner surface 131 of the first housing 130. Similarly, the ring 160 is bonded to the inner surface 141 of the second housing 140. According to the invention, the first portion of each ring has a greater thickness than the second portion, which increases the bonding surface between the ring and the housing and thus improves its hold in the housing delimited between the core and the belt.

[0062] We do not, of course, depart from the scope of the invention if the rings 150 and 160 are attached to the fibrous assembly 200 before densification by the matrix or during the formation of the fibrous assembly 200 in place of the conformation elements 51 and 52, the rings 150 and 160 then being secured respectively in the housings 130 and 140 during densification by the matrix.

[0063] 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 component thereof, or even a brake rod.

[0064] The part according to the invention thus exhibits better mechanical properties, particularly when loaded in compression and tension.

Claims

Demands

1. Connecting piece (100) comprising a core (110) of composite material comprising a fibrous reinforcement densified by a matrix, at least a first ring (150) comprising a first portion (153) cooperating with a first end (111) of the core (110) and a belt (120) of composite material comprising a fibrous reinforcement densified by a matrix, the composite material belt surrounding the core and a second portion (154) of said at least a first ring (150), said at least a ring defining an orifice intended to be traversed by a shaft to make a connection with another piece, the piece (100) being characterized in that the second portion (154) of said at least a first ring (150) has a thickness (Ei54) less than the thickness (Ei53) of the first portion (153) of said at least a first ring.

2. Part according to claim 1, wherein the second portion (154) of said at least a first ring (150) has a constant thickness.

3. Part according to claim 1 or 2, wherein the first portion (153) of said at least a first ring has a variable thickness.

4. Part according to claim 3, wherein the thickness of the first portion (153) of said at least a first ring varies from 2 mm to 6 mm or from 2 mm to 45 mm.

5. Part according to any one of claims 1 to 4, wherein said at least one first ring (350) comprises a flat (355) present at least between one end of the first portion (353) and one end of the second portion (354) of said at least one first ring.

6. A connecting piece according to any one of claims 1 to 5, said piece further comprising a second ring (160) having a first portion cooperating with a second end (112) of the core (110) and the belt (120), the belt surrounding the core and a second portion of the second ring (160), said second ring defining an orifice for a shaft to be passed through for connection with another piece, the second portion of the second ring (160) having a thickness less than the thickness of the first portion of said second ring, the orifice defined by the second ring being of the same dimension or of a different dimension than the dimension of the orifice defined by the first ring.

7. A method for manufacturing a connecting piece made of composite material, comprising: - three-dimensional weaving of a core fiber preform (210) and a belt fiber preform (220), - arranging the belt fiber preform (220) around the core fiber preform (210) so as to form at least one first recess (230) between a first end of the core fiber preform (210) and the belt fiber preform (220), - co-densification of the core fiber preform (210) and the belt fiber preform (220) by a matrix so as to obtain a connecting piece (100) made of composite material comprising a core (110), a belt (120) and at least one first recess (130) located between a first end (111) of the core (110) and the belt (120), - bonding of at least one first ring (150) in said at least one first housing (130) of the composite material connecting piece (100),said at least a first ring comprising a first portion (153) cooperating with a first end (111) of the core (110) and a second portion (154) cooperating with a first closed inner edge (121) of the belt (120), or - the three-dimensional weaving of a fibrous core preform (210) and a fibrous belt preform (220), - the arrangement of the fibrous belt preform (220) around the fibrous core preform (210) and at least a first ring (150) comprising a first portion (153) cooperating with a first end (211) of the core preform (210) and a second portion (154) cooperating with a first edge (221) of the belt preform (220), - the co-densification of the fibrous core preform (210) and the fibrous belt preform (220) by a matrix so as to obtain a connecting piece (100) made of composite material comprising a core (110),a belt (120) and at least one first ring (150) present between a first end (111) of the core (110) and a first edge (121) of the belt (120), characterized in that the second portion (154) of said at least one first ring (150) has a thickness (Ei54) less than the thickness (Ei53) of the first portion (153) of said at least one ring.

8. Method according to claim 7, wherein the second portion (154) of said at least a first ring (150) has a constant thickness.

9. Method according to claim 7 or 8, wherein the first portion (153) of said at least a first ring (150) has a variable thickness.

10. Method according to claim 9, wherein the thickness of the first portion (153) of said at least one first ring (150) varies from 2 mm to 6 mm or from 2 mm to 45 mm.

11. A method according to any one of claims 7 to 10, wherein said at least one first ring (350) comprises a flat (355) present at least between one end of the first portion (353) and one end of the second portion (354) of said at least one first ring.

12. A method according to any one of claims 7 to 11, further comprising: - bonding a second ring (160) into a second recess (140) of the composite connecting piece (100), the second ring having a first portion (163) cooperating with a second end (112) of the core (110) and a second portion (164) cooperating with a second closed inner edge (122) of the belt (120), or - co-densifying the fibrous core preform (210) and the fibrous belt preform (220) by a matrix so as to obtain a composite connecting piece (100) comprising a core (110), a belt (120), and a first ring (150) present between a first end (111) of the core (110) and a first edge (121) of the belt (120), and a second ring (160) is present between a second end (112) of the core (110) and a second edge (121) of the belt (120).

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