Method for manufacturing a part made of thermoplastic material incorporating metallic fillers

Abstract

A method for manufacturing a part made of thermoplastic material incorporating metallic fillers. A method for manufacturing a part suitable for welding to another part comprises forming, on a part body (105), one or more portions (106) of thermoplastic material (140) filled with metallic particles (120) corresponding to one or more assembly surfaces (101) of the part. Figure for the abstract: Fig. 1.

Description

Title of the invention: Method for manufacturing a part made of thermoplastic material incorporating metallic fillers. Technical field

[0001] The present invention relates to the field of thermoplastic material parts and, more particularly to the welding assembly of such parts. Previous technique

[0002] Thermoplastic materials and in particular composite materials comprising reinforcing fibers, for example carbon fibers and / or glass fibers, dispersed in a thermoplastic polymer matrix have many possible uses, and in particular, in the field of aeronautics. For the construction of certain structures, it may be necessary to assemble several parts made of thermoplastic material such as, for example, for a thrust reverser flap, a stiffened panel, stiffeners, fairing elements, etc. These composite parts can be assembled by welding, particularly using a technology such as: Induction welding, resistive welding, welding by heat and pressure Ultrasonic welding, laser welding.

[0003] Document EP 2 907 651 describes an induction welding process in which an assembly consisting of two parts to be welded made of thermoplastic matrix composite material and a field absorber or susceptor positioned at the interface between the parts is subjected to a magnetic field. The magnetic field causes the susceptor to heat up to a temperature that allows the thermoplastic resin to soften or melt. The use of a susceptor between the parts to be welded has the disadvantage of technically complicating the welding operation due to the need for precise positioning and holding the susceptor in place between the parts during welding. Furthermore, the use of a susceptor increases manufacturing time and cost. In addition, the presence of a susceptor at the interface between the two parts can compromise the mechanical strength of the resulting structure in service. Description of the invention

[0004] The main purpose of the present invention is therefore to provide a solution for the welding of a part made of thermoplastic material which does not have the aforementioned disadvantages.

[0005] According to the invention, this goal is achieved through a manufacturing process for a part suitable for welding to another part, characterized in that it comprises the formation on a part body of one or more portions of thermoplastic material loaded with metallic particles corresponding to one or more assembly surfaces of the part.

[0006] By forming one or more portions of thermoplastic material filled with metallic particles in one or more parts of the component, the problems associated with the use of a susceptor described above are eliminated. Integrating metallic particles into the thermoplastic material of the component facilitates positioning between the parts to be assembled with good repeatability during serial production. The process of the invention avoids the use of a susceptor, which constitutes an additional step that can be technically or economically disadvantageous (manual positioning can be complex, and the component is costly and difficult to install). Furthermore, the presence of the susceptor can impair the component's performance in service.

[0007] Furthermore, by using one or more portions of thermoplastic material filled with overmolded or embedded metallic particles, thermal diffusivity can be controlled within a part whose body is made of a heat-sensitive material such as a thermoplastic. Indeed, it is thus possible to locally heat the thermoplastic material of the part above its melting point at the joint surface(s) while maintaining a sufficiently low temperature in the rest of the part's material to ensure its geometric stability and a controlled level of crystallinity.

[0008] According to one embodiment of the method according to the invention, this method comprises introducing a thermoplastic material loaded with metal particles into one or more portions of a mold so as to form one or more sections corresponding to one or more assembly surfaces of the part, and introducing a thermoplastic material not loaded with metal particles into the remainder of the mold so as to form the body of the part. The thermoplastic material not loaded with metal particles may comprise a simple thermoplastic resin or a thermoplastic resin loaded with short fibers.According to a particular aspect of this embodiment, the mold has a plurality of cavities forming a network of ribs, the thermoplastic material loaded with metallic particles being introduced into the bottom of the cavities so as to be present at one crest of the ribs of the thermoplastic part, the unloaded thermoplastic material then being introduced into the rest of the cavities.

[0009] According to another embodiment of the method according to the invention, it comprises producing a composite skin forming a part body and forming, on at least one face of the composite skin, one or more portions of thermoplastic material filled with metallic particles corresponding to one or more assembly surfaces of the part. The portion(s) of thermoplastic material filled with metallic particles are produced by injection molding of a thermoplastic material filled with metallic particles onto the part body. The portion(s) of thermoplastic material filled with metallic particles may also be produced by thermocompression of a thermoplastic material filled with metallic particles onto the part body.

[0010] According to a particular feature of the process of the invention, the metallic particles are made of a material capable of heating up under the effect of a magnetic field. They can be made in particular with one of the following materials: copper, iron, titanium and nickel.

[0011] According to another particular feature of the process of the invention, the metallic particles have a size between 1 pm and 100 pm.

[0012] According to another particular feature of the process of the invention, the thermoplastic material loaded with metallic particles comprises between 1% and 80% by mass of metallic particles.

[0013] The invention also relates to a method for manufacturing a structure comprising at least first and second parts, the method comprising manufacturing a first part in thermoplastic material according to the method for manufacturing a part of the invention, joining the assembly surface(s) of the first part with a second part and placing the joined first and second parts in a magnetic field so as to weld said first part to the second part. Brief description of the drawings

[0014] [Fig.1] Fig.1 is a schematic perspective view of a part made of thermoplastic material according to an embodiment of the invention,

[0015] [Fig.2A] Fig.2A is a schematic perspective view showing the injection of a thermoplastic material loaded with metallic particles into a mold,

[0016] [Fig.2B] The [Fig.2B] is a schematic perspective view showing the injection of a thermoplastic material not loaded with metallic particles into the mold of the [Fig.2A],

[0017] [Fig.3] Fig.3 is a schematic perspective view of a part according to another embodiment of the invention,

[0018] [Fig.4] Fig.4 is a schematic cross-sectional view showing a tool injection molding used to produce the part in [Fig.3],

[0019] [Fig.5] Fig.5 is a schematic cross-sectional view showing the abutment of the part of Fig.1 with a composite skin,

[0020] [Fig.6] The [Fig.6] is a schematic cross-sectional view showing the realization of a structure by welding the two parts of the [Fig.5]. Description of the implementation methods

[0021] Figure 1 represents a part made of thermoplastic material 100 according to an embodiment of the invention. The part 100 comprises a part body 105 made of a first thermoplastic material not filled with metallic or similar particles 130, the part body 105 forming here a network of ribs 110 intersecting perpendicularly.

[0022] According to the invention, the part 100 further comprises a portion 106 made with a thermoplastic material 140 loaded with metallic particles 120. In the example described here, the portion 106 is present at the level of a crest 111 of the ribs 110 which defines the assembly surface 101 of the part 100, that is to say the part of the part 100 intended to be welded with another part.

[0023] As illustrated in [Fig. 2A], the manufacture of the part 100 first involves the introduction, here by injection, of a thermoplastic material 140 loaded with metal particles 120 into one or more portions of a mold 50 corresponding to one or more assembly surfaces 101 of the part 100. In the example described here, the mold 50 has a plurality of cavities 56 forming a network of ribs. The thermoplastic material 140 loaded with metal particles 120 is introduced into the bottom of the cavities 56 so as to be present at a crest 111 of the ribs 110 of the part after demolding.

[0024] As shown in [Fig.2B], a thermoplastic material not loaded with metallic or similar particles 130 is then introduced, here by injection, into the rest of the cavities 56 so as to form the body of part 105 after demolding.

[0025] The injection of the two materials is shown schematically in Figures 2A and 2B. In practice, a thermoplastic material loaded with metallic particles is injected into the mold via one or more first injection ports, while the thermoplastic material not loaded with metallic or similar particles is injected into the mold via one or more second injection ports located on the mold at different positions from the first injection port(s). Furthermore, it is possible to carry out the first injection of the thermoplastic material loaded with metallic particles into a mold whose mold cavity has a height corresponding to that of portion 106 of part 100. The mold is then opened and extended in height to allow the second injection of the thermoplastic material not loaded with metallic particles. metallic or similar particles 130 so as to form the body of part 105. According to one embodiment, the formed portion 106 is transferred to another mold suitable for injection molding of the part body. The injection of the thermoplastic material not filled with metal particles or similar materials, intended to form the part body 105, can be carried out before the injection of the thermoplastic material filled with metal particles, intended to form portion 106 of the part 100.

[0026] After successive injections of the two thermoplastic materials 140 and 130 and cooling of the mold, the part 100, comprising the body of the part 105 and the portion 106 which together form the network of ribs 110 ([Fig. 1]), is demolded. When the part 100 is subjected to a magnetic field, the metal particles 120 heat up, causing the thermoplastic material 140 to melt locally. The part 100 is thus ready to be joined to another part by inductive welding.

[0027] The thermoplastic material used to form the part can be of different types. By way of non-limiting examples, the part according to the invention can be made with one of the following thermoplastic materials: PAEK (PolyArylEtherKetone), PEEK (PolyEtherEtherKetone), PEKK (PolyEtherKetoneKetone), PEI (polyetherimide), TPU or PU (Thermoplastic Polyurethane), PESU or PPS (polyphenylene sulfide).

[0028] The thermoplastic material can be in the form of a resin alone or a resin loaded in particular with short fibers which can be carbon, glass, aramid fibers, etc.

[0029] The part can also be made by compression molding of a composite material reinforced with discontinuous long fibers of the type BMC (Bulk Molding Compound), SMC (Sheet Molding Compound) or DLF (Discontinuous Long Fibers).

[0030] The size of the fibers is typically between 0.1 mm and 1 mm for short fibers and between 1 mm and 50 mm for long fibers.

[0031] The metallic particles used as fillers in the thermoplastic material are made of a material capable of heating up under the effect of a magnetic field. By way of non-limiting examples, the metallic particles may be made of one of the following materials: copper, iron, titanium and nickel.

[0032] The metallic particles preferably have a size between 1 pm and 100 pm. The thermoplastic material loaded with metallic particles comprises between 1% and 80% by mass of metallic particles.

[0033] Figure 3 shows a part 200 according to another embodiment of the invention. The part 200 comprises a part body 205 made of a skin of composite material including a continuous fiber reinforcement densified by a thermoplastic matrix. The part body 205 can, in particular, be made by stamping, thermocompression, automated placement of AFP fibers, etc.

[0034] According to the invention, part 200 further comprises, on a face 205a of the body of part 205, a portion 206 made of a thermoplastic material 240 loaded with metallic particles 220 similar to the metallic particles 120 already described. In the example described here, portion 206 has a shape corresponding to a rib network like the rib network 110 of part 100, portion 206 defining an assembly surface on part 200. Part 200 is suitable for welding to a part in the shape of a rib network similar to part 100, which, in this case, does not need to be provided with a portion of thermoplastic material loaded with metallic particles.

[0035] The portion 220 can be produced by overmolding onto the part body 205, which has been previously produced by stamping. More specifically, as illustrated in [Fig. 4], a tooling 70 is used, comprising a first half-shell 71 with a recess 72 in which the part body 205 is placed, and a second half-shell 73 with molding cavities 74 into which a thermoplastic material 240 loaded with metal particles 220 is injected. After cooling and demolding, the part 200 of [Fig. 3] is obtained.

[0036] According to one embodiment, portion 220 can be produced by thermocompression using a tool comprising a first half-shell with initial mold cavities beneath which the part body is placed, and a second half-shell with additional mold cavities designed to cooperate with the initial mold cavities. Thermoplastic material filled with metallic particles is placed in each of the initial cavities. The tool is then closed by applying pressure to the second half-shell while heating the mold to carry out the thermocompression. After cooling and demolding, part 200 of [Fig. 3] is obtained.

[0037] A method for manufacturing a structure according to an embodiment of the invention between the thermoplastic part 100 described above and a skin 300 is now described. The method begins, as illustrated in [Fig. 5], by bringing the assembly surface 101 of the part 100, comprising the metal particles 120, into contact with a surface 301 of the skin 300 in a predetermined position. In the example described here, the skin 300 is made of a composite material comprising a continuous fiber reinforcement densified by a thermoplastic matrix. The skin 300 can, in particular, be produced by stamping, thermocompression, automated fiber placement, etc.

[0038] Once parts 100 and 300 are positioned relative to each other, maintaining the assembly surface 101 of part 100 in contact with the assembly surface 301 of part 300, the welding operation is carried out as illustrated in [Fig. 6]. The assembly thus formed is subjected to a magnetic field C60 created by a inductor 60.

[0039] Under the influence of the magnetic field, the metallic particles 120 present at the assembly surface 101 heat up, causing the thermoplastic material of the part 100 to melt locally as close as possible to the assembly interface between the two parts, thus welding them together. Preferably, a pressure P is applied to the two parts during welding.

[0040] A structure 500 is then obtained, comprising a skin 300 attached to a network of ribs corresponding to the part 100. The junction portions between the ribs 110 of the part 100 and the skin 300 have ridges 112 resulting from the softening or melting of the thermoplastic material at the assembly interface. The ridges 112 reinforce the welded connection between the part 100 and the skin 300. The structure 500 can, in particular, constitute all or part of a thrust reverser flap, a stiffened panel, a fuselage or fairing component, a sandwich-type structure, particularly for acoustic treatments, etc.

[0041] The plastic part according to the invention may comprise several heating elements. Several identical or different heating elements may be placed in the same location on the part in order to increase the local heating temperature if necessary. Several identical or different heating elements may also be placed in different locations on the part in order to form several joining surfaces within the part and allow, for example, welding the part to several other parts.

[0042] By overmolding or embedding one or more heating elements in one or more parts of the part, the thermal diffusivity within the part is controlled. It is thus possible to locally heat the thermoplastic material of the part above its melting point at the assembly surface(s) while maintaining a sufficiently low temperature in the rest of the part's material to ensure its geometric stability and a controlled level of crystallinity.

[0043] According to one embodiment, the portion or portions of thermoplastic material loaded with metallic particles, such as portions 106 or 206 described above, can be replaced by a metallic deposit produced for example by CVD chemical vapor deposition, by 3D printing, cold spray metallization, or any other method of deposition or accretion by projection.

Claims

Demands

1. A method for manufacturing a part (200) suitable for welding to another part, comprising the production of a composite skin forming a part body (205), characterized in that it comprises the formation on at least one face (205a) of the composite skin of one or more portions (206) of thermoplastic material (240) loaded with metallic particles (220) corresponding to one or more assembly surfaces (101) of the part, the portion(s) (206) of thermoplastic material (240) loaded with metallic particles (220) being produced by thermocompression on the part body (205).

2. A method according to claim 1, wherein the metallic particles (220) are made of a material capable of heating up under the effect of a magnetic field (C60).

3. A method according to any one of claims 1 to 2, wherein the metallic particles (220) have a size between 1 pm and 100 pm.

4. A method according to any one of claims 1 to 3, wherein the thermoplastic material (240) loaded with metallic particles (220) comprises between 1% and 80% by mass of metallic particles.

5. Method of manufacturing a structure (500) comprising at least first and second parts (100, 300), the method comprising manufacturing a first part (100) according to the method as defined in claims 1 to 4, abutting the assembly surface(s) (101) of the first part with a second part (300) and placing the abutted first and second parts in a magnetic field so as to weld said first part to the second part.

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