FR2981004A1 - Composite material part, useful for automotive field, comprises structural layer made of composite material comprising fibers maintained by matrix made of thermo-hardening polymeric resin, metal layer, and bonding layer including matrix - Google Patents

Abstract

The composite material part comprises a structural layer (11) made of composite material comprising fibers maintained by a matrix (15) made of thermo-hardening polymeric resin, a metal layer (19), and a bonding layer (17) that is placed between the metal layer and the structural layer and includes a matrix (18) made of thermoplastic polymeric resin. The thermoplastic resin of the bonding layer has a melting point of 150-250[deg] C. The thermo-hardening resin of the structural layer is enriched in particles of compatible thermoplastic resin with the resin of the matrix of the bonding layer. The composite material part comprises a structural layer (11) made of composite material comprising fibers maintained by a matrix (15) made of thermo-hardening polymeric resin, a metal layer (19), and a bonding layer (17) that is placed between the metal layer and the structural layer and includes a matrix (18) made of thermoplastic polymeric resin. The thermoplastic resin of the bonding layer has a melting point of 150-250[deg] C. The thermo-hardening resin of the structural layer is enriched in particles of compatible thermoplastic resin with the resin of the matrix of the bonding layer. The structural layer comprises two parts separated by an interface extending to the bonding layer in a non-parallel manner. Each one of the two parts includes a different thermo-hardening polymeric matrix. The two parts are covered with the bonding layer and include a thermoplastic polymeric matrix. An independent claim is included for a process for fabricating a composite material part.

Description

The invention relates to metallized composite material parts on the surface. The invention relates more particularly to the lightning protection of aeronautical composite parts comprising a thermosetting polymer matrix. The use of composite materials is widespread in many technical fields, such as automotive or aerospace. This type of material is particularly sought for the mass gain that it provides, with equivalent mechanical properties, compared to conventional materials such as metals. Composite materials are particularly used for the manufacture of aircraft structural parts. These materials comprise inorganic or organic fibers which are held by an organic resin matrix. The resin of the matrix may have thermoplastic or thermosetting properties. A thermoplastic material softens or melts when heated above a certain temperature, and becomes hard again below this temperature. This phenomenon is reversible and generally does not alter the mechanical properties of the material. On the contrary, the transformation of a thermosetting material involves an irreversible polymerization and leads to a solid, generally rigid finished product. Thermoplastic resins suitable for use in aircraft structural parts are generally more expensive or more difficult to process than suitable thermosetting resins. The present invention relates particularly to the case of composite materials with a thermosetting matrix. The composite materials are generally electrically insulating or bad conductors, which poses problems in the event of lightning strikes, for example on an aircraft structure. Also, the thermosetting composite structure parts for aircraft structure are generally metallized on the surface, in order to improve their surface conductivity.

A known solution is to integrate the composite part, a wire mesh or metal deployed on the surface. The mesh, impregnated with thermosetting resin, is draped over a structural layer, also called laminate, before polymerization of the matrix.

The laminate is made by stacking layers of plies comprising resin-impregnated fibers. It is desirable to stack these folds by an automated method, in order to reduce the cost of manufacturing parts. Automation is also advantageous for the manufacture of specific parts, for example large and / or non-developable, that is to say curved in two directions. The method of surface metallization with mesh, described above, applies to non-developable parts such as the front tips of aircraft. Compared to fences, continuous or semi-continuous metal films offer the advantage of better conductivity at equivalent mass. However, the application of such films on the surface of a thermosetting part is difficult to achieve before polymerization, especially on non-developable parts because of their double curvature, such as the front tips of aircraft. However, the front tips are parts subjected to more harmful lightning impacts than the current parts of the fuselage, and therefore require stronger protection against lightning. In addition, draping the mesh to provide this protection usually generates a significant increase in mass. The known methods of metallization of thermosetting parts after metallization, such as electroplating, spraying or gluing, are also difficult to implement on an industrial scale, especially for large parts. The present invention allows the industrial manufacture of metallized thermosetting parts, with a good adhesion of the metal to the part, the metallization can take place after polymerization of the thermosetting matrix. More specifically, an object of the invention is a composite material part comprising: a structural layer of composite material comprising fibers held by a thermosetting polymer resin matrix; a substantially continuous metal layer; said part being characterized in that it comprises a bonding layer between the metal layer and the structural layer, said bonding layer comprising a thermoplastic polymer resin matrix. The thermoplastic resin bonding layer makes it possible to effectively weld the structural layer and the metal layer, subsequent to the polymerization of the thermosetting resin. The metal layer is essentially continuous, that is to say that it does not comprise periodic grid openings. Due to this continuity, it is possible to manufacture a piece of mass less than that obtained by means of a grid, for an equivalent conductivity. According to one embodiment of the invention, a thermosetting resin of the structural layer is chosen from a polyepoxide resin, a bismaleimide resin or a phenolic resin. These resins are used in a known manner for the manufacture of composite aircraft structural parts. According to one embodiment of the invention, the thermoplastic resin of the bonding layer is chosen with a relatively low melting temperature, especially between 150 ° C and 250 ° C. The metallization can thus take place at a temperature that does not damage the resin of the structural layer. A preferred resin is, for example, PVDF (polyvinylidene fluoride). According to one embodiment of the invention, a thermosetting resin of the structural layer is enriched with particles of a thermoplastic resin. This thermoplastic resin may be different from that of the tie layer but have better compatibility with said resin of the tie layer than the thermosetting resin. Adhesion between the structural layer and the tie layer can be improved. According to one embodiment of the invention, the structural layer comprises two parts separated by an interface extending non-parallel to the bonding layer, each of said two parts comprising a thermosetting polymer matrix, said two parts being covered with a same tie layer, comprising a thermoplastic polymer matrix.

This embodiment is particularly advantageous when the two thermosetting matrices are different. It makes it possible to metallize a heterogeneous composite part continuously, which is difficult with the methods known from the state of the art.

The composite parts according to the invention can be manufactured by methods analogous to known methods. However, the invention also relates to a particularly advantageous method for this type of room. Indeed, another object of the invention is a method of manufacturing a composite material part as described above, said method comprising successively the following steps: a step of depositing one or more impregnated structural folds a thermosetting resin to form the structural layer; a step of depositing a thermoplastic resin layer on the structural layer, said thermoplastic resin having a melting temperature close to a polymerization temperature of said thermosetting resin; a step of polymerizing the structural layer at said polymerization temperature; a possible cooling step of the piece thus formed; a step of depositing a substantially continuous metal layer on the thermoplastic resin layer. Subsequent polymerization of the deposition of the thermoplastic layer allows partial interpenetration of the molten thermoplastic resin and the thermosetting resin. The adhesion between the structural layer and the tie layer is thus reinforced.

This interpenetration is favored in the case where the thermosetting resin is enriched in thermoplastic resin particles. The bonding layer binds more particularly to these particles during the polymerization. Several processes are possible to metallize the part. According to one embodiment of the invention, the step of depositing a metal layer comprises a hot spraying of metal powder on the thermoplastic resin layer. By "hot" means that the temperature is equal to or greater than the glass transition temperature of the thermoplastic layer, in order to soften at least locally.

According to another embodiment of the invention, the step of depositing a metal layer comprises hot-bonding the thermoplastic resin layer with another layer of thermoplastic resin coated with a metal sheet. Preferably, the two thermoplastic resin layers comprise the same thermoplastic resin. Another object of the invention is a part as described above and capable of being formed by a method as described above. Such a part comprises in particular an interpenetration zone of the bonding layer with the structural layer.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These are given as an indication and in no way limitative of the invention. The figures show: FIG. 1: a schematic sectional view of a composite material part, according to one embodiment of the invention; Figure 2 is a schematic view of a composite part before metallization, according to another embodiment of the invention; Figure 3: a schematic view of a metallization process of the part of Figure 2; Figure 4 is a schematic sectional view of a composite material part, according to another embodiment of the invention. Figure 1 shows a schematic sectional view of a part 10 of composite material, according to one embodiment of the invention. The part 10 comprises a structural layer 11 made of composite material. The structural layer 11 is formed of one or more stacked structural folds (12, 13). The pleats (12, 13) typically include fibers 14 held by a matrix of thermosetting polymer resin. The fibers 14 of the structural folds are, for example, carbon or glass fibers. The nature and / or the spatial orientation of the fibers 14 may vary according to the fold (12, 13), in a known manner. On the other hand, the thermosetting matrix is preferably identical for all the plies (12, 13), in order to ensure good cohesion to the part 10. The thermosetting matrix 15 is preferably formed of a polyepoxide resin, commonly called epoxy resin. In the context of the invention, it is also possible to use a bismaleimide resin or a phenolic resin, or any other type of thermosetting resin used in known manner for the manufacture of composite parts in the field of aeronautics.

A fold 12, close to a surface 16 of the part 10, is in contact with a connecting layer 17. Said layer comprises a matrix 18 of thermoplastic polymer resin. The matrix 18 of thermoplastic polymer resin is preferably chosen with a relatively low melting temperature, for reasons developed below. A preferred resin is, for example, PVDF (polyvinylidene fluoride) or another thermoplastic fluoropolymer. However, depending on the process chosen for the manufacture of the part 10, other types of resins, at higher melting temperatures, can be used.

The connecting layer 17 is itself in contact with a metal layer 19, able to conduct electric currents. The layer 19 is intended to be arranged on the side of the part 10 most exposed to lightning. The layer 19 may form the surface 16 of the part 10, but may also be covered with a layer of paint or finish.

Preferentially, the layer 19 is essentially continuous, that is to say that it does not comprise periodic grid openings. The layer 19 may nevertheless comprise point openings imposed by the shape and / or the mechanical functions of the part 10. The choice of the metal of the layer 19, as well as the thickness 20 of said layer, are notably related to constraints. mass and electrical conductivity. A preferred metal for layer 19 is, for example, copper or aluminum. A thickness of the layer 19 is preferably between 10 μm and 50 μm. A thickness 21 of the connecting layer 17 preferably varies between 1 μm and 300 μm, more preferably between 25 μm and 100 μm. The connecting layer 17 may comprise mineral fibers (not shown), in particular glass fibers. These fibers can avoid galvanic corrosion of the layer 19, related to the presence of carbon fibers in the structural layer 11.

The bonding layer 17 may also comprise mineral fillers such as metal oxides, in order to improve the adhesion between the layers 17 and 19. The component 10 may be manufactured by various methods analogous to known methods. For example, the bonding layer 17 may be deposited on an already polymerized structural layer 11. Depending on the respective nature of the thermosetting and thermoplastic resins, a microroughness of the structural layer can generate sufficient adhesion between the two layers 11 and 17.

Nevertheless, it is common that the thermosetting resin and the thermoplastic resin are incompatible, as is the case for most epoxy resins and PVDF resins. In order to ensure sufficient adhesion between the structural layer and the bonding layer, it is advantageous to use a manufacturing method as described below: FIG. 2 represents a schematic sectional view of a part 30 composite material, allowing the manufacture of a part according to one embodiment of the invention. The part 30 comprises a structural layer 31 of composite material, similar to the layer 11 described above. The layer 31 comprises in particular a matrix 35 of thermosetting polymer resin. The part 30 further comprises a layer 37 which comprises a matrix 38 of thermoplastic polymer resin. The layer 37 forms a surface 36 of the part 30.

In a known first step of a manufacturing method of the part 30, a structural layer 31 is produced by depositing one or more structural folds 32 impregnated with a thermosetting resin. The folds 32 are for example stacked on a mold (not shown) to give a desired shape to the workpiece 30.

In a second step, a layer 37 of thermoplastic resin 38 is deposited on the unpolymerized structural layer 38. The deposition can be carried out by known methods, such as the lay-up on the layer 31 of a resin film 38. or else the projection on the layer 31 of resin particles 38. The resin 38 is chosen with a melting temperature close to a polymerization temperature of the thermosetting resin. "Close temperature" means a difference of the order of 30 ° C more or less. In a third step, the structural layer is cured by polymerization of the resin 35. This step takes place, for example, in an autoclave 5 or in an oven, in a known manner. This third step gives rise to the formation of an intermediate layer 39, between the layers 31 and 37. The layer 39 results from the partial interpenetration of the thermosetting resin 35 and the thermoplastic resin 38, related to the total or partial melting of the resin 38 during the polymerization of the resin 35. This partial interpenetration ensures a good adhesion between the layers 31 and 37, independently of the physicochemical compatibility between the resins 35 and 38. Preferably, the thermosetting resin is a resin epoxy 15 and its polymerization is carried out at a temperature of around 180 ° C. A suitable thermoplastic resin 38 is, for example, a PVDF resin whose melting point is around 180 ° to 200 ° C. According to one embodiment of the invention, the thermosetting resin of the structural layer 31 is enriched in particles (not shown) of thermoplastic resin. This thermoplastic resin may be identical or different from the resin 38, while having a better physico-chemical compatibility with the resin 38 than the resin 35. During the polymerization, the fully or partially melted layer 37 binds more particularly to these particles of thermoplastic resin, which promotes partial interpenetration between the layers 31 and 37. After cooling, the part 30 can be manipulated and / or stored before undergoing a metallization step. This method therefore advantageously makes it possible to split the manufacture of metallized composite parts into several distinct phases, which brings more flexibility in the management of the tools necessary for the manufacture of said parts. Moreover, the structural layer being covered with thermoplastic resin, the development of the metallization step does not require to take into account the physicochemical characteristics of the thermosetting resin of said structural layer. Said method is therefore applicable to several different thermosetting resins without particular development. Several methods can be envisaged for the metallization of the part 30, in order to lead to a part similar to the part 10 of FIG.

According to a first method, a metal powder is sprayed on the layer 37 of thermoplastic resin. "Hot spray" means that the metal particles are brought to a temperature around the glass transition temperature of the layer 37. The resin 38 is thus softened locally, which promotes the adhesion of the metal layer thus formed. Such a process is known as "cold spray". According to one variant, the projection of metal powder can be carried out by keeping the workpiece 30 at a temperature equal to or greater than the glass transition temperature of the layer 37.

Another method of metallization of the part 30 is shown diagrammatically in FIG. 3. Such a method involves the assembly of said part 30 with a hybrid fold 40. Said fold 40 comprises a metal layer 49, preferably substantially continuous and having a good electrical conductivity. The layer 49 is for example a sheet or a strip of copper or aluminum. The fold 40 further comprises a layer 47 comprising a thermoplastic resin matrix 48, compatible with the resin 38 of the part 30. Preferably, it is a resin of the same nature as the resin 38. As described herein above for FIG. 1, the layer 47 may comprise mineral fillers such as metal oxides. The layer 47 may further comprise mineral fibers 44, especially glass fibers. These fibers increase the mechanical strength of the fold 40 and facilitate its handling. A hybrid fold similar to fold 40 is described in particular in document FR2934198, in the name of the Applicant. The metallization of the workpiece 30 comprises contacting the thermoplastic layers (37, 47) of said workpiece 30 and the fold 40. This contacting can be done at a local temperature in the region of the glass transition temperature of the resin 38. , in order to perform a pre-welding for positioning the fold 40 satisfactorily on the part 30. The assembly thus formed is then consolidated at a temperature close to the melting temperature of the resin 38. This consolidation step preferably place in a vacuum oven, in known manner.

This metallization process is analogous to a process described in the above-mentioned document FR2934198. Another mode of metallization may be consolidation welding in situ, that is to say bringing into contact at a local temperature close to the melting temperature of the thermoplastic resin. This gives a definite weld directly. For the non-developable parts 30 of the aircraft nose type, it is particularly advantageous to deposit different folds 40 in the form of strips, positioned edge to edge, so as to adapt each fold to the different curvatures of the part.

Figure 4 shows a schematic sectional view of a part 50 of composite material, according to another embodiment of the invention. The part 50 comprises a structural layer 51 of composite material. The structural layer 51 has at least two portions (52, 53), each of said portions being formed of stacked structural folds. Each portion (52, 53) comprises a matrix (54, 55) of thermosetting polymer resin. The matrices 54 and 55 may be of the same nature or of different natures. The two parts (52, 53) are separated by an interface 56. The interface 56 is arranged non-parallel to the stack of folds of at least one of the two parts (52, 53). Preferably, the interface 56 is substantially perpendicular to the stack of folds of the two parts (52, 53). The two parts (52, 53) can be assembled at the interface 56 by known means. A fold 57, on the surface of the portion 52, preferably forms a continuous surface with a fold 58 of the surface 53, i.e. the folds (57, 58) are substantially flush with each other. other. The folds (57, 58) are covered with a same bonding layer 59, comprising a thermoplastic polymer matrix. The bonding layer 59 is preferably continuous at the interface 56. The bonding layer 59 is itself in contact with a metal layer 60, similar to the layer 19 of the part 10 shown in FIG. Figure 1. The layer 60 is intended to be arranged on the side of the part 50 most exposed to lightning. The thermoplastic resin bonding layer 59 advantageously homogeneously metallises a composite part comprising a plurality of parts (52, 53) whose thermosetting matrices comprise different types of resin. The metallization of the layer 59 can be carried out by one of the methods described above, such as the cold spray 10 or the assembly with a hybrid metal / thermoplastic resin fold. The assembly formed by the parts (52, 53) and the layer 59 can advantageously be formed integrally, by a process similar to that described above for the part 30: the parts (52, 53) can be assembled before baking, covered with a thermoplastic film and then polymerized, which allows an interpenetration of the layer 59 with each of the folds (57, 58). However, it is also possible to assemble the parts (52, 53) after baking and then cover them with a thermoplastic film.

Claims (10)

REVENDICATIONS1. Part (10, 50) made of composite material comprising: - CLAIMS1. Part (10, 50) of composite material comprising: - a layer (11, 31, 51) of composite material comprising fibers held by a matrix (15, 35) of thermosetting polymer resin; a substantially continuous metallic layer (19, 49), said part being characterized in that it comprises a layer (17, 37, 59) for bonding between the metal layer and the structural layer, said tie layer comprising a matrix (18, 38) thermoplastic polymer resin. 2. Part according to claim 1, such that a thermosetting resin of the structural layer is selected from a polyepoxide resin, a bismaleimide resin and a phenolic resin. 3. Part according to claim 1 or claim 2, such as a thermoplastic resin of the bonding layer has a melting temperature between 150 ° C and 250 ° C. 20 4. Part according to one of the preceding claims, such that a thermosetting resin of the structural layer is enriched in particles of a thermoplastic resin compatible with the resin of the matrix of the bonding layer. 25 5. Part (50) according to one of the preceding claims, such that the structural layer comprises two parts (52, 53) separated by an interface (56) extending non-parallel to the bonding layer, each of said two parts comprising a different thermosetting polymer matrix (54, 55), said two parts being covered with a same bonding layer (59), comprising a thermoplastic polymer matrix. 6. A method of manufacturing a composite material part according to one of the preceding claims, said method comprising successively the following steps: a step of deposition of one or more structural folds (32) impregnated with a thermosetting resin for forming the structural layer (31), a step of depositing a layer (37) of thermoplastic resin on the structural layer, said thermoplastic resin having a melting temperature close to a polymerization temperature of said thermosetting resin, a step of polymerization of the structural layer at said polymerization temperature, a possible step of cooling the piece (30) thus formed, a step of depositing a substantially continuous metal layer (49) on the thermoplastic resin layer. 7. The method of claim 6, wherein the step of depositing a metal layer comprises hot-bonding the layer (37) of thermoplastic resin with another layer (47) of thermoplastic resin coated sheet (49). ) of metal. 8. The method of claim 7, wherein the two thermoplastic resin layers comprise the same thermoplastic resin. 9. The method of claim 6, wherein the step of depositing a metal layer comprises a hot spraying of metal powder on the layer (37) of thermoplastic resin. 10. Part according to one of claims 1 to 5, may be derived from a method according to one of claims 6 to 9.