Assembly comprising at least one composite part and fixing means
The assembly of a composite part with a draping of unidirectional fibers and a specifically designed fixing zone addresses the issue of local overstresses in composite assemblies, enabling efficient transmission of mechanical actions and improving structural integrity.
Patent Information
- Application Number
- FR2023003380
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-04-05
- Publication Date
- 2025-06-20
- Estimated Expiration
- 2043-04-05
AI Technical Summary
Existing mechanical fixing methods for composite parts often lead to local overstresses, creating weak points that can result in cracking and premature failure, especially due to eccentricity of fasteners relative to the neutral fiber of the composite.
The assembly comprises a composite part with a draping of unidirectional fibers in a thermoplastic or thermosetting matrix, featuring a fixing zone with a cavity parallel to the contact surface and a bore perpendicular to it, designed to receive a threaded element for secure clamping.
This solution allows for the transmission of significant mechanical actions in the main direction of the composite walls, reducing the risk of overstresses and enhancing the structural integrity of composite assemblies.
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Abstract
Description
Title of the invention: Assembly comprising at least one composite part and fixing means
[0001] The present invention relates to the field of composite materials and, more particularly, to a composite part manufactured by means of specific draping, the latter being adapted for association with a means of fixing said composite part to any second part.
[0002] The attachment of composite parts to another part, whether the latter is also made of composite or of a non-composite material, constitutes an important parameter in the design and manufacture of said composite parts.
[0003] Indeed, in particular, mechanical fixings, such as clamps or screws, between a composite part and a second part, generate local overstresses, so that these fixings represent the weak point of the composite structures and can lead to cracking of the composite and premature failures.
[0004] In particular, in conventional fasteners, the eccentricity of the fastener relative to the neutral fiber of the part causes bending. However, this stress is a particular difficulty in the field of composites, because it creates a fragile zone in the direction change zone, in particular in T or L fittings, a disadvantage which is further accentuated by the fact that variations in shell direction are difficult to achieve and therefore costly.
[0005] The present invention aims to remedy, at least in part, the drawbacks of the mechanical fixing methods existing in the field of composite parts, by proposing the production of a fixing method allowing transmission of significant mechanical actions in the main direction of the composite walls.
[0006] To this end, the invention relates to an assembly comprising, at least, a first composite part consisting of a draping of sheets of unidirectional fibers in a thermoplastic or thermosetting matrix, said first composite part being intended to be secured, at a fixing zone which it comprises, to a second part, composite or not, a bearing edge of said first composite part coming into contact with a bearing edge of said second part, thus creating a contact surface, said assembly further comprising means for fixing said first composite part to said second part.
[0007] Said assembly is particular in that, at least at the level of said fixing zone, said first composite part is composed of a drape consisting of a superposition of unidirectional sheets with different fiber orientation angles between two adjacent sheets, and in that, in a first example of rea lization, at the level of said fixing zone, at least one cavity is provided in said first composite part, parallel to said contact surface, and at least one bore along an axis perpendicular to said contact surface, said bore starting from the bearing edge of said first composite part and opening into said cavity, said bore being intended to receive a threaded element while said cavity and the second part serve as support for clamping elements.
[0008] Thus, through the invention, the fact of stressing in the axis of the fibering of the composite part makes it possible to resolve the problems encountered in the assemblies existing in the state of the art.
[0009] In a second embodiment of the assembly of the invention, at least one cavity is provided in said first composite part, parallel to said contact surface created between said first composite part and said second composite part, while the drilling is carried out along an axis inclined relative to this contact surface.
[0010] According to particular embodiments of the assembly of the invention, whether it is the first or the second example of embodiment as described above:
[0011] - the cavity of said first composite part consists of a lumen;
[0012] - said first composite part comprises an excess thickness of sheets of uni fibers directional at least in the fixing area;
[0013] - said cavity formed in said first composite part is of cylindrical shape lindrique and the clamping element coming into said cavity consists of a threaded cylinder of dimensions adapted to those of said cavity;
[0014] - the draping of sheets of unidirectional fibers of said first composite part consists of a stack, repeated n times, composed of a first sheet, the fibers of which are oriented at 90° with the main axis of said first part, said first sheet being topped with a sandwich consisting of a central sheet the fibers of which are oriented at 0° with the main axis of the first part between two intermediate sheets the fibers of which are oriented at + or - 45° with the fibers of said first central sheet and with the fibers of the first sheet.
[0015] The invention also relates to a method for manufacturing a first composite part, consisting of a draping of sheets of unidirectional fibers in a thermoplastic or thermosetting matrix, and of securing, by means of the assembly according to the present invention, said first composite part to a second part, composite or not, at a fixing zone that said first composite part comprises, a bearing edge of said first composite part coming into contact with a bearing edge of said second part, thus creating a contact surface.
[0016] More particularly, said method is characterized in that it comprises, at least, the following steps, taken in order:
[0017] - The draping of said first piece is formed by superimposing n sheets of uni fibers directional, the fibers of two adjacent sheets having different orientation angles, and the matrix is polymerized;
[0018] - At least one cavity is provided at the level of a fixing zone which comprises said first composite part, said cavity being parallel to said contact surface;
[0019] - At least one drilling is carried out along an axis perpendicular to said surface of contact, starting from the bearing edge of said first composite part and opening into said cavity;
[0020] - Said bearing edge of said first composite part is brought into contact with said bearing edge of said second part, and a threaded element is inserted into said drilling and clamping elements into said cavity and at the level of said second part to secure said two parts.
[0021] When the method aims to manufacture the assembly according to the second embodiment of the invention, as already described above, the steps are similar, except for the fact that the drilling is carried out along an axis inclined relative to said contact surface between the first composite part and the second part, composite or not.
[0022] Other aims and advantages of the present invention will appear during the description which follows relating to embodiments which are given only as indicative and non-limiting examples.
[0023] Understanding of this description will be facilitated by referring to the attached drawings in which:
[0024] [Fig. 1] represents a schematic and perspective view of a particular embodiment of an assembly according to the invention, comprising, on the left of the figure, a first composite part intended to be secured, through a fixing zone and via fixing means, to a second part, composite or not, visible on the right of the figure.
[0025] [Fig.2] represents a schematic and sectional view of the first composite part illustrating the succession of layers of unidirectional fibers forming a draping in which holes are provided, also represented.
[0026] [Fig.3] represents a schematic view of three non-limiting examples of embodiments of composite parts which can be secured to another part, composite or not, through the assembly according to the invention, namely, from left to right, a fitting, a tube, or a turbo machine blade.
[0027] [Fig.4] represents a schematic and exploded view of an exemplary embodiment of an assembly according to the present invention, in which the first composite part consists of a first type of fitting.
[0028] [Fig.5] represents a schematic and perspective view of another example of embodiment of a part of an assembly according to the present invention, namely the first composite part, in which the latter consists of a second type of fitting.
[0029] [Fig.6] represents two different views, schematic and in perspective, of another example of embodiment of a part of an assembly according to the present invention, namely the first composite part, in which the latter consists of a third type of fitting, called multipoint fitting.
[0030] [Fig.7] represents two similar views, schematically and in perspective, one of the two views being an enlargement of a part of the second view, of another example of embodiment of a part of an assembly according to the present invention, namely the first composite part, in which the latter consists of an I-beam.
[0031] [Fig.8] represents two schematic views, one in section and in perspective and the second in section and in full, of another example of embodiment of a part of an assembly according to the present invention, namely the first composite part, in which the latter consists of a first type of tube having a constant diameter over its entire length.
[0032] [Fig.9] represents two schematic views, one in section and in perspective and the second in section and in its entirety, of another example of embodiment of a part of an assembly according to the present invention, namely the first composite part, in which the latter consists of a second type of tube having a larger diameter at the level of the zone of attachment of said first composite part to a second part, composite or not, which is not illustrated in the figure.
[0033] [Fig. 10] represents a partial schematic view of another example of embodiment of a part of an assembly according to the present invention, namely the first composite part, which has a flat surface perpendicular to the drilling.
[0034] [Fig. 11] represents a partial schematic view of another example of embodiment of a part of an assembly according to the present invention, namely the first composite part, in which the cavity is arranged parallel to a contact surface between said first part and a second part (not shown), while the drilling is carried out along an axis inclined relative to this contact surface.
[0035] With reference to the figures of the attached drawings, the present invention relates, more particularly, to an assembly 1 comprising, on the one hand, a first composite part 2 intended to be secured, at the level of a fixing zone 21 which it comprises, to a second part 3.
[0036] This second part 3 can also be a composite part. However, it can also be a non-composite part.
[0037] Said second part 3, composite or not, can be considered as forming part of the assembly 1 according to the invention, or as not forming part of said assembly 1.
[0038] Said first composite part 2 is, in a conventional manner, made up of a succession of sheets of unidirectional fibers 41, 42, 43, 44, 45 in a thermoplastic or thermosetting matrix.
[0039] Said sheets 41, 42, 43, 44, 45 are superimposed on each other so as to form a drape 4, which is more particularly illustrated, in a very schematic manner, in [Fig.2] of the attached drawings.
[0040] According to a feature of the invention, at least at the level of the fixing zone 21 of said first composite part 2, the draping 4 consists of a superposition of sheets of unidirectional fibers 41, 42, 43, 44, 45 having different angles of orientation of said fibers between two adjacent sheets.
[0041] Thus, for example, two adjacent sheets may advantageously have unidirectional fibers having orientation angles different from + or - 45°, at least at the level of the fixing zone 21 of said first composite part 2 and, preferably, over the whole of said part 2.
[0042] Obviously, when the second part 3 to which the first composite part 2 is to be secured is also a part made of composite material, the latter can be manufactured in the same way as said first composite part 2. It can also be obtained by any other means known to those skilled in the art for manufacturing composite parts.
[0043] To return to the joining between said first composite part 2 and the second part 3, composite or not, this is carried out, on the one hand, through the contacting of a bearing edge 22 that said first composite part 2 comprises, at the level of the fixing zone 21, with a bearing edge 32 that the second composite part 3 comprises, which allows the creation of a contact surface between these two parts 2, 3 and, on the other hand, by means of fixing means 5.
[0044] The contact surface between the two parts can be flat or curved (as shown for example in [Fig.3] of the attached drawings, illustrating a blade fixed on a tube).
[0045] According to another particular feature of the assembly 1 of the invention, at the level of the fixing zone 21 of the first composite part 2, at least one cavity 6 is formed in said first composite part 2, in an orientation parallel to said contact surface between said first part 2 and the second part 3. Said cavity 6 is thus perpendicular to the main axis of said part 2.
[0046] Furthermore, at least one bore 7 is provided, along an axis perpendicular to said contact surface between the two parts 2, 3, said bore 7 starting more particularly from the bearing edge 22 of the fixing zone 21 of the part 2, and opening out in cavity 6.
[0047] The bore 7 is intended to receive a threaded element 51 which the fixing means 5 comprise, while the cavity 6 and the second part 3 serve as support for clamping elements 52, 53 which also make up the fixing means 5.
[0048] The cavity 6 is preferably open so that it can consist of a light, according to the embodiment which is illustrated in the attached figures.
[0049] It should be noted that, preferably, and as shown in particular in Figures 1 and 3 to 9, the assembly 1 of the present invention more preferably comprises a plurality of cavities 6 and an equivalent number of holes 7, the quantity and arrangement of these orifices being adapted according to the shapes and dimensions of said first composite part 2 to be secured to said second part 3.
[0050] Most preferably, and as illustrated in the attached figures, said cavity 6, or said cavities where appropriate, provided in said first composite part 2 have(s) a cylindrical shape.
[0051] Thus, the clamping element 52 intended to be positioned in said cavity 6 may consist of a threaded cylinder 52 of dimensions adapted so as to allow its insertion within said cavity 6, while the fixing means 5 are completed by a screw 51, 53. This particularly preferred embodiment is that which is illustrated in [Fig.l] of the attached drawings.
[0052] However, it is conceivable that said cavity 6, as well as the clamping element 52 intended to be integrated within said cavity 6, have any shape and size.
[0053] With reference to [Fig. 10] of the attached drawings, it is thus conceivable that one of the edges of the cavity 6 has, at least partially, or even totally, a flat surface perpendicular to the bore 7. This advantageously allows the use of conventional screws and washers as tightening elements.
[0054] Such a design of an assembly 1 in accordance with the present invention allows the absorption of considerable tensile force, the resistance limit being the mechanical strength of the screws.
[0055] Of course, the shapes may be advantageously adapted to allow the threaded elements to be fixed by tightening on the side of the first composite part 2 (not illustrated), or on the side of the second part 3, composite or not, as illustrated in the figures.
[0056] Furthermore, intermediate support elements 54, visible in figures 4, 5, 6, of the half-moon washer type, may possibly supplement the fixing means 5, in particular when the cavity 6 is of concave shape, the intermediate support element 54 then allowing clamping on a flat surface.
[0057] Note that the draping 4 of the sheets 41, 42, 43, 44, 45 of said first part composite 2 can be optimized and, in particular, the stacking of sheets 41, 42, 43, 44 which is illustrated in [Fig.2] proves to be particularly effective, notably in terms of resistance.
[0058] In particular, the draping 4 of sheets 41, 42, 43, 44, 45 of unidirectional fibers of said first composite part 3 is made up of a stack of sheets 41, 42, 43, 44, 45, composed as follows:
[0059] - a first sheet 41 is provided whose fibers are oriented at 90° with the axis principal of said first part 2,
[0060] - said first sheet 41 is topped with a sandwich consisting of a sheet central 43 whose fibers are oriented at 0° with the main axis of the first composite part 2 between two intermediate plies 42, 44 whose fibers are oriented at + or - 45° with the fibers of said first central ply 43 and with the fibers of the first ply 41,
[0061] - this stacking is repeated n times, starting again with a sheet 45 whose fibers are oriented at 90° with the main axis of said first part 2, etc.
[0062] In a particularly advantageous manner, said first composite part 2 comprises an excess thickness E of unidirectional fiber layers 41, 42, 43, 44, 45, at least in the fixing zone 21 of this composite part 2 to a second part 3, composite or not.
[0063] With reference to [Fig. 11] of the attached drawings, this represents a part of an assembly according to the invention, namely the first composite part 2, in a second exemplary embodiment of the invention, similar to the first, the cavity 6 being again formed parallel to the contact surface between the two parts 2, 3 to be assembled, while, unlike the first exemplary embodiment described previously, the bore 7 is formed along an axis which is inclined relative to said contact surface created between said two parts 2, 3 to be assembled.
[0064] Thus the drilling 7, in the representation on the left of [Fig.l 1], where the clamping element passes, can be inclined in the mean plane of the surface of the composite part 2, for example to increase the shear transmission capacity of the connection, or to transmit a torsion torque for a shaft.
[0065] As regards the right part of [Fig.l 1], the drilling 7 can also be inclined in the plane perpendicular to the mean plane of the composite surface 2, to facilitate the installation of the clamping elements.
[0066] All of the characteristics that have been described above, in connection with the first embodiment of the assembly, in which the first composite part 2 comprises a bore 7 arranged along an axis perpendicular to said contact surface between said first composite part 2 and a second part 3, are also applicable to this second embodiment in which the bore 7 is inclined by relative to this contact surface.
[0067] The present invention also relates to a method of manufacturing, on the one hand, a first composite part 2, consisting of a drape 4 of sheets of unidirectional fibers 41, 42, 43, 44, 45 in a thermoplastic or thermosetting matrix, and of securing, on the other hand, by means of the assembly 1 described above, said first composite part 2 to a second part 3, composite or not.
[0068] As already mentioned, the joining of the two parts 2, 3 is carried out at the level of a fixing zone 21 which comprises said first composite part 2, a bearing edge 22 of said first composite part 2 coming into contact with a bearing edge 32 of said second part 3, thus creating a contact surface between said first composite part 2, and the second part 3, the latter being able to be composite or not.
[0069] The manufacturing and joining method according to the invention comprises at least the following steps, taken in order:
[0070] - The draping 4 of said first part 2 is formed by superimposing n sheets of fibers unidirectional 41, 42, 43, 44, 45, the fibers of two adjacent sheets having different fiber orientation angles, and a polymerization of the thermoplastic or thermosetting matrix is carried out;
[0071] - note that, preferably, but optionally, during the formation of the draping 4, an excess thickness E of unidirectional fiber layers is produced at least in the fixing zone 21 of the first composite part 2 which will intervene in the subsequent stages of securing the latter to the second part 3;
[0072] - At least one cavity 6 is provided at the level of said fixing zone 21 that comprises said first composite part 2, the latter preferably having an excess thickness of fiber layers, said cavity 6 being produced along an axis parallel to the contact surface between said first composite part 2 and the second part 3, composite or not;
[0073] - At least one drilling 7 is carried out along an axis perpendicular to the surface of contact or, as the case may be, inclined relative to this contact surface, starting from the bearing edge 22 of said first composite part 2 and opening into the cavity 6 which was drilled in the fixing zone 21 in the previous step;
[0074] - Said bearing edge 22 of said first composite part 2 is brought into contact with said bearing edge 32 of said second part 3, and a threaded element 51 is inserted into said bore 7 and clamping elements 52, 53 into said cavity 6 and at the level of said second part 3 to proceed with the securing of said first composite part 2 with said second part 3.
[0075] The elements and preferred characteristics which have been described in connection with the assembly 1 of the invention can of course be applied to the method of the invention, in particular with regard to the sequence of the fiber sheets for the formation of the draping 4, and with regard to the plurality of cavities 6 and holes 7 which can be provided at the level of the fixing zone 21 of the first composite part 2.
[0076] Referring now to [Fig. 3] of the attached drawings, it should be noted that the fixing system according to the invention will be able to follow the geometric evolution of the wall of the composite part 2 to be fixed, so as to optimize the cohesion of the assembly between said composite part 2 and a second part 3, in particular during stresses which may be complex or in complex geometries, such as fittings 2a, tubes 2b, or turbomachine blades 2c.
[0077] Figures 4 and following illustrate various applications of the present invention for a connection of a first composite part 2 to a second part 3, made of composite or not.
[0078] Thus, in figures 4, 5, 6, the first composite part 2 consists of a fitting, in particular a multi-point fitting in [Fig.6].
[0079] In [Fig.7], the first composite part 2 consists of an I-beam.
[0080] In Figures 8 and 9, the first composite part 2 consists of a tube
[0081] The tube of [Fig.8] has a constant diameter over its entire length, and, at the level of its fixing zone 21, an increase in thickness is made to compensate for the shrinkage of material and to have the thickness necessary for the fixing means.
[0082] In [Fig.9], a tube of larger diameter is shown at the level of the fixing zone 21 of said first composite part 2 to a second composite part 3, so as to allow clearance to facilitate the installation of the fixing means and for axial access to these fixing means (not illustrated in the figure).
[0083] In this particular application, shown in [Fig.9], it can be noted that the fixing axis is offset from the main axis of the composite part 2, which makes it possible to adapt the shape of the composite part to the fixing method for reinforcement at the fixing zone.
[0084] More generally, the invention has applications in the production of aeronautical fittings, transmission shafts, masts, beams, etc.
Claims
Claims
1. Assembly (1) comprising, at least, a first composite part (2) consisting of a lay-up (4) of sheets of unidirectional fibers (41, 42, 43, 44, 45) in a thermoplastic or thermosetting matrix, said first composite part (2) being intended to be secured, at a fixing zone (21) which it comprises, to a second part (3), composite or not, a bearing edge (22) of said first composite part (2) coming into contact with a bearing edge (32) of said second part (3) creating a contact surface, said assembly (1) further comprising means (5) for fixing said first composite part (2) to said second part (2) and being characterized in that, at least at said fixing zone (22), said first composite part (2) is composed of a lay-up (4) consisting of a superposition of sheets unidirectional (41, 42, 43, 44,45) with different fiber orientation angles between two adjacent plies, and in that, at the level of said fixing zone (21), at least one cavity (6) is provided in said first composite part (3), parallel to said contact surface and in a direction perpendicular to the direction of the unidirectional plies (41, 42, 43, 44, 45), and at least one bore (7) along an axis perpendicular to said contact surface, said bore (7) starting from the bearing edge (22) of said first composite part (2) and opening into said cavity (6), said bore (7) being intended to receive a threaded element (51) while said cavity (6) and the second part (3) serve as support for clamping elements (52, 53).,
2. Assembly (1) according to claim 1 characterized in that the cavity (6) of said first composite part (2) consists of a light.
3. Assembly (1) according to claim 1 or claim 2 characterized in that said first composite part (2) comprises an excess thickness (E) of unidirectional fiber sheets (41, 42, 43, 44, 45) at least in the fixing zone (21).
4. Assembly (1) according to any one of the preceding claims, characterized in that said cavity (6) formed in said first composite part (2) is of cylindrical shape and the clamping element (52) coming into said cavity (6) consists of a threaded cylinder (52) of dimensions adapted to those of said cavity (6).
5. Assembly (1) according to any one of the preceding claims, characterized in that the draping (4) of sheets of unidirectional fibers of said first composite part (2) consists of a stack, repeated n times, composed of a first sheet (41), the fibers of which are oriented at 90° with the main axis of said first part (2), said first sheet (41) being surmounted by a sandwich consisting of a central sheet (43) the fibers of which are oriented at 0° with the main axis of the first part between two intermediate sheets (42, 44) the fibers of which are oriented at + or - 45° with the fibers of said first central sheet (43) and with the fibers of the first sheet (41).
6. Method for manufacturing a first composite part (2), consisting of a lay-up (4) of sheets of unidirectional fibers (41, 42, 43, 44, 45) in a thermoplastic or thermosetting matrix, and of securing, by means of the assembly (1) according to one of the preceding claims, said first composite part (2) to a second part (3), composite or not, at a fixing zone (21) that said first composite part (2) comprises, a bearing edge (22) of said first composite part (2) coming into contact with a bearing edge (32) of said second part (3) creating a contact surface, said method being characterized in that it comprises, at least, the following steps, taken in order: - The draping (4) of said first part (2) is formed by superimposing n sheets of unidirectional fibers (41, 42, 43, 44, 45), the fibers of two adjacent sheets having different orientation angles, and the matrix is polymerized; - At least one cavity (6) is provided at the level of a fixing zone (21) which comprises said first composite part (2), said cavity (6) being parallel to said contact surface and in a direction perpendicular to the direction of the unidirectional layers (41, 42, 43, 44, 45); - At least one hole (7) is made along an axis perpendicular to said contact surface, starting from the bearing edge (22) of said first composite part and opening into said cavity (6); - Said bearing edge (22) is brought into contact with said first composite part (2) with said bearing edge (32) of said second part (3), and a threaded element (51) is inserted into said bore (7) and clamping elements (52, 53) into said cavity (6) and at the level of said second part (3) to secure said two parts (2, 3).
7. Assembly (1) comprising, at least, a first composite part (2) consisting of a lay-up (4) of sheets of unidirectional fibers (41, 42, 43, 44, 45) in a thermoplastic or thermosetting matrix, said first composite part (2) being intended to be secured, at a fixing zone (21) which it comprises, to a second part (3), composite or not, a bearing edge (22) of said first composite part (2) coming into contact with a bearing edge (32) of said second part (3) creating a contact surface, said assembly (1) further comprising means (5) for fixing said first composite part (2) to said second part (3) and being characterized in that, at least at said fixing zone (22), said first composite part (2) is composed of a lay-up (4) consisting of a superposition of sheets unidirectional (41, 42, 43, 44,45) with different fiber orientation angles between two adjacent plies, and in that, at the level of said fixing zone (21), at least one cavity (6) is provided in said first composite part (3), parallel to said contact surface and in a direction perpendicular to the direction of the unidirectional plies (41, 42, 43, 44, 45), and at least one bore (7) along an axis inclined relative to said contact surface, said bore (7) starting from the bearing edge (22) of said first composite part (2) and opening into said cavity (6), said bore (7) being intended to receive a threaded element (51) while said cavity (6) and the second part (3) serve as support for clamping elements (52, 53).,