Method for manufacturing a part made of composite material

Abstract

Method for manufacturing a part, particularly a connecting rod, made of composite material comprising a thermoplastic or thermosetting matrix reinforced with fibres, the method comprises winding or de

Description

Title: Method for manufacturing a part made of composite material Technical field of the invention The present invention relates, in general, to parts made of composite material, such as a connecting rod. More specifically, the invention relates to a method for manufacturing a part made of composite material, in particular, comprising a thermoplastic or thermosetting matrix reinforced with fibres. Prior art A conventional means of manufacturing a connecting rod made of composite material is based on the manufacture of a preform with the aid of one or more tools, such as a metal mandrel and / or a mould. Document FR 3 053 622 describes, for example, a method for manufacturing a connecting rod. The preform is produced by filament winding of pre-impregnated fibres around the mandrel, before being cut so as to be removed from the mandrel. Next, the preform is placed in a female mould in order to be shaped, then tensioned using a bladder placed inside the preform. The connecting rod is then obtained at the end of a step of polymerization. The use of tools such as the mandrel or the mould requires one or more steps of removal of same. In particular, given the shape of the connecting rod, the mandrel ends up trapped inside the preform. The number and the nature of the steps arising from the use of a tool makes such a manufacturing method particularly difficult and expensive. Summary of the invention The invention therefore aims to overcome these drawbacks and to propose a simple and inexpensive means for manufacturing a part made of composite material, such as a connecting rod. It thus proposes a method for manufacturing a part made of composite material comprising a thermoplastic or thermosetting matrix reinforced with fibres. The method further comprises the following successive steps: a) winding or depositing pre-impregnated fibres, so as to form a preform around a mandrel comprising a thermoplastic or thermosetting material, said fibres being pre-impregnated with a thermoplastic or thermosetting matrix, b) winding a heat-shrinkable film around the preform, c) polymerizing the intermediate product obtained at the end of step b) at a polymerization temperature that depends on the composite material used, and d) removing the heat-shrinkable film from the intermediate product so as to obtain said part made of composite material in one piece, which includes the mandrel. The part made of composite material is thus obtained by a manufacturing method that is simple, comprising a limited number of steps, and inexpensive, not involving the use of tools that need to be removed. To be specific, the part made of composite material obtained is formed directly of the mandrel and the preform. Advantageously, the pre-impregnated fibres may be impregnated with a thermoplastic or thermosetting matrix, such as an epoxy resin, comprising carbon and / or glass fibres. Advantageously, the material of the mandrel may be a composite material comprising a thermoplastic or thermosetting matrix reinforced with fibres. According to one feature, a pressure may be applied inside the mandrel during one or more of the steps a), b) and c). In one embodiment, the mandrel may include at least two independent parts that are assembled together before step a). For example, the mandrel may comprise first and second forked parts assembled respectively to the first and second ends of a main tubular part. The manufacturing method may further comprise the addition of at least one reinforcement, such as a patch, before step a), on the mandrel, preferably in a housing of the mandrel. Preferably, a notch, such as a wing, is formed on the mandrel so as to make it easier to put the reinforcement, such as a patch, in place. Advantageously, the material of the mandrel may comprise particles, such as fibres, having electrical conductivity properties and / or anti-corrosion properties. Advantageously, the manufacturing method may comprise, prior to step a), the at least partial manufacture of the mandrel using one or more of the following techniques: extrusion, extrusion blow moulding, injection moulding, injection blow moulding, blow moulding, rotational moulding, thermoforming, 3D printing, pultrusion or filament winding. The invention also relates to a connecting rod made of composite material, characterized in that it is produced by implementing the manufacturing method described above. Brief description of the figures Further aims, advantages and features will become clear from the description set out below, which is provided purely by way of illustration and with reference to the attached drawings, in which: [Fig 1] is a flow chart showing the steps of a method for manufacturing a part made of composite material according to an exemplary embodiment of the invention, [Fig 2] shows a connecting rod according to another embodiment of the invention, [Fig 3a] [Fig 3b] and [Fig 3c] are schematic views in longitudinal section of a connecting rod in various steps of its manufacture according to an exemplary embodiment of the manufacturing method of the invention, [Fig 4] is a schematic view in longitudinal section of a mandrel according to another embodiment of the invention, and [Fig 5] shows patches being put in place during a method for manufacturing a connecting rod according to another exemplary embodiment of the invention. Detailed description of the invention With reference to Figure 1, the invention relates to a method for manufacturing a part made of composite material. In the example shown in Figure 2, the part made of composite material produced according to an exemplary embodiment of the manufacturing method according to the invention is a connecting rod 1. Alternatively, the method may be applied to the manufacture of other types of parts. The connecting rod 1 shown comprises a main tubular portion 2 having first and second opposite ends 2a and 2b from which extend, respectively, first and second forked portions 3 and 4. The first and second forked portions 3 and 4 are advantageously yokes, each being intended to be attached to a tenon. Alternatively, the connecting rod 1 may have a single forked portion. With reference to Figure 3a, the manufacturing method according to the invention advantageously comprises providing a mandrel M comprising a thermoplastic or thermosetting material. The thermoplastic or thermosetting material of the mandrel M is, for example, a resin. The material of the mandrel M may be a composite material comprising a thermoplastic or thermosetting matrix reinforced with fibres, for example glass and / or carbon fibres. The mandrel M advantageously has, at least partially, a shape generally similar to the shape of the connecting rod 1 to be produced. In the example illustrated, the mandrel M comprises a tubular portion 5 having first and second opposite ends 5a and 5b from which extend, respectively, first and second forked portions 6 and 7. Naturally, the shape of the mandrel M may be adapted to the desired shape of the connecting rod 1. The mandrel M may, for example, have a single forked portion. In a step a), and as shown in Figure 3b, pre-impregnated fibres are then wound or deposited so as to form a preform P around the mandrel M. Preferably, the preform P covers the whole of the outer surface of the mandrel M. The pre-impregnated fibres are fibres pre-impregnated using a thermoplastic or thermosetting matrix, for example an epoxy resin. The preform P may be formed by deposition of pre-impregnated fibres in the form of a pre-impregnated sheet, known as a "prepreg", or in the form of a cut pre-impregnated sheet, known as a "slit tape". According to another alternative, the preform P may be formed by winding of a pre-impregnated fibre, known as a "towpreg". With reference to Figure 3c, the manufacturing method then comprises, in a step b), winding a heat-shrinkable film F around the preform, in contact with the preform P. Preferably, the heat-shrinkable film F covers the whole of the outer surface of the preform P. Heat-shrinkable film means a film that can shrink under the effect of heat. In a subsequent step c), the thermoplastic or thermosetting matrix of the pre-impregnated fibres is polymerized. To this end, the assembly or intermediate product obtained at the end of step b), and made up of the mandrel M, the preform P and the heat-shrinkable film F, is placed in an oven, under pressure and temperature conditions adapted to the nature of the thermoplastic or thermosetting matrix of the pre-impregnated fibres to be polymerized. The heat-shrinkable film F, which shrinks under the effect of the heat applied during polymerization, creates a pressure on the preform P and compacts it against the mandrel M. The material of the heat-shrinkable film F is advantageously adapted as a function of the nature of the thermoplastic or thermosetting matrix of the pre-impregnated fibres, and in particular adapted in such a way as to withstand the temperature of polymerization of the thermoplastic or thermosetting matrix of the pre-impregnated fibres. The heat-shrinkable film F is a plastic film, for example made of polyester. After polymerization, the heat-shrinkable film F is removed in a step d), and the connecting rod 1 made of composite material is obtained. The part made of composite material is thus obtained by a manufacturing method that is simple, quick and does not involve any tools that have to be removed. The mandrel M made of thermoplastic or thermosetting material, whether or not reinforced with fibres, forms an integral part of the connecting rod 1 obtained, which makes it possible to produce the preform P without it being necessary to remove the mandrel M. The connecting rod 1 made of composite material is made up of the mandrel M and the preform P which, after the step c) of polymerization, form a one-piece part. Advantageously, the manufacturing method according to the invention may comprise a step of applying a pressure inside the mandrel M. The pressure may be applied during one or more of the steps a), b) and c). Such a pressure, for example between 3 and 6 bar, makes it possible to reinforce the compacting of the preform P. Such a pressure also makes it possible to optimize the tensioning of the preform P, preventing said preform P from being crushed or deformed under the effect of the tension due to the filament winding. In one embodiment, the material of the mandrel M may comprise particles, such as fibres, having electrical conductivity properties and / or anticorrosion properties. For example, the mandrel M may be made of composite material comprising a thermoplastic or thermosetting matrix incorporating carbon or metal fibres, for example copper fibres, for electrical conductivity or glass fibres for an anti-corrosion, in particular anti-galvanic corrosion, effect. According to one feature, the manufacturing method according to the invention may comprise, prior to step a), the at least partial manufacture of the mandrel M. The mandrel M may be manufactured using one or more of the following techniques: extrusion, extrusion blow moulding, injection moulding, injection blow moulding, blow moulding, rotational moulding, thermoforming, 3D printing, pultrusion or filament winding. "At least partial" means the manufacture of a portion or of a part of the mandrel M or of the entire mandrel M by one of these techniques: extrusion, extrusion blow moulding, injection moulding, injection blow moulding, blow moulding, rotational moulding, thermoforming, 3D printing, pultrusion or filament winding. Preferably, the mandrel M provided for step a) has a shape close to or similar to the shape of the connecting rod 1 to be produced so as to avoid the need to machine the part obtained in order to obtain the final shape of the connecting rod 1. In the embodiment shown in Figure 3a, the mandrel M is in one piece. As an alternative, the mandrel M may be made up of two, or more, independent parts assembled together. In the example shown in Figure 4, the mandrel M comprises a tubular part 8 having first and second opposite ends 8a and 8b. The mandrel M also comprises first and second forked parts 9 and 10 that are assembled, respectively, to the first and second ends 8a and 8b of the tubular part 8. As an alternative, the mandrel M may be made up of a single forked part assembled to the tubular portion 8. The assembly of several parts so as to form the mandrel M makes it possible to use several manufacturing techniques depending on the shape and the nature of the material of each part of the mandrel M. Assembly makes it possible to adapt the nature of the material of each part according to its location on the mandrel M and the mechanical properties it must have. This makes it possible to reduce the cost of manufacturing the mandrel M, and its overall weight. Furthermore, assembly also allows direct manufacture of complex parts, such as the forked parts 9 and 10, without it being necessary to machine them. Moreover, a specific tubular part 8 may be assembled to various forked parts, and vice versa. In the example shown in Figure 4, given their complex shape, the two forked parts 9 and 10 may, for example, be produced by injection moulding, whereas the tubular part 8 may, for example, be produced by extrusion, pultrusion or filament winding. Preferably, the mandrel M, in one piece, such as that shown in Figure 3a, is produced by blow moulding, which is a simple and inexpensive technique and allows the mandrel M to be easily manufactured on an industrial scale. The manufacturing method according to the invention may comprise, in one embodiment, the addition of at least one reinforcement, such as a patch, on the mandrel M. Advantageously, one or more reinforcements may be added on various areas of the mandrel M, before the winding or the deposition of the preimpregnated fibres on the mandrel M, or on the preform P. The position of the reinforcements on the mandrel M may be determined by the desired advantage. In particular, these local reinforcements may be deposited directly on the mandrel M and / or on the preform P as the preform P is wound on the mandrel M. A function of mechanical reinforcement may be achieved by alternating winding of the preform P and deposition of the reinforcement. The reinforcements allow local reinforcement, in particular mechanical, of certain areas of the mandrel M which may need to have superior mechanical properties, such as higher compressive strength. According to another example, a function of control over galvanic corrosion may be obtained by directly depositing reinforcements with anti-galvanic corrosion properties on the mandrel M. Preferably, the reinforcements are made of a material that is identical to that constituting the preform P. A reinforcement may be made up of a stack of such material so as to form a patch. The preform P may be positioned in such a way as to overlap at least one end of the reinforcement. Advantageously, the mandrel M may include one or more housing(s) intended to receive the reinforcements, such that the shape of the mandrel M used in step a) is advantageously appropriate for forming complex areas and such that it can be functionalized without it being necessary to carry out shaping and machining of the part obtained at the end of step d). In the example shown in Figure 5, first and second patches 11 and 12 are positioned on the forked portions 3 and 4, respectively, of a mandrel M made in one piece. Preferably, and as shown in Figure 5, first and second wings 13 and 14 are formed on the forked portions 7 and 8, respectively, of the mandrel M, forming two housings for putting the patches 11 and 12 in place. Placing local reinforcements on the mandrel M before steps b) and c) makes it possible to produce complex portions of the mandrel M and to do away with steps of machining of the part after polymerization.

Claims

1. Method for manufacturing a part made of composite material comprising a thermoplastic or thermosetting matrix reinforced with fibres, characterized in that it comprises the following successive steps:a) winding or depositing pre-impregnated fibres, so as to form a preform (P) around a mandrel (M) comprising a thermoplastic or thermosetting material, said fibres being pre-impregnated with a thermoplastic or thermosetting matrix,b) winding a heat-shrinkable film (F) around the preform (P),c) polymerizing the intermediate product obtained at the end of step b) at a polymerization temperature that depends on the composite material used, andd) removing the heat-shrinkable film (F) from the intermediate product so as to obtain said part made of composite material in one piece, which includes the mandrel (M).

2. Manufacturing method according to Claim 1, wherein the preimpregnated fibres are impregnated with a thermoplastic or thermosetting matrix, such as an epoxy resin, comprising carbon and / or glass fibres.

3. Manufacturing method according to Claim 1 or 2, wherein the material of the mandrel (M) is a composite material comprising a thermoplastic or thermosetting matrix reinforced with fibres.

4. Manufacturing method according to any one of the preceding claims, wherein a pressure is applied inside the mandrel (M) during one or more of the steps a), b) and c).

5. Manufacturing method according to any one of the preceding claims, wherein the mandrel (M) includes at least two independent parts (8, 9, 10) that are assembled together before step a).

6. Manufacturing method according to Claim 5, wherein the mandrel comprises first and second forked parts (9, 10) assembled respectively to the first and second ends (8a, 8b) of a main tubular part (8).

7. Manufacturing method according to any one of the preceding claims, comprising the addition of at least one reinforcement (11, 12), such as apatch, before step a), on the mandrel (M), preferably in a housing of the mandrel (M).

8. Manufacturing method according to any one of the preceding claims, wherein the material of the mandrel (M) comprises particles, such as fibres, 5 having electrical conductivity properties and / or anti-corrosion properties.

9. Manufacturing method according to any one of the preceding claims, comprising, prior to step a), the at least partial manufacture of the mandrel (M) using one or more of the following techniques: extrusion, extrusion blow moulding, injection moulding, injection blow moulding, blow moulding,10 rotational moulding, thermoforming, 3D printing, pultrusion or filament winding.

10. Connecting rod made of composite material, characterized in that it is produced by implementing the manufacturing method according to any one of the preceding claims.

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