Link between a thin metal liner and a composite wall by thermoplastic particle-filled coating
The invention concerns a method for producing, by welding, a link between an element made from any material, for example metal, and an element made from a thermoplastic-matrix composite material, the second element being produced by depositing a textile yarn pre-impregnated with a thermoplastic material on the surface of the first element. The method mainly includes an operation consisting of producing an interface coating consisting of an epoxy resin filled with a thermoplastic material powder, coating the surface of the element made from any material with same, and leaving the coating to polymerize. It next includes an operation consisting simultaneously of forming the second element and welding same to the coating deposited on the surface of the first element by locally heating the two elements, when depositing the pre-impregnated textile on the first element.
1. A process for providing the assembly between a first structural element made from a first material and a second structural element made from a thermoplastic matrix composite material, comprising the following steps:
a first step of preparing a coating, said coating consisting of an epoxide resin, wherein a powder of particles of a thermoplastic material is incorporated;
a second step of coating, during which the coating is applied to the surface of the first structural element;
a third step during which the coating is polymerized;
a fourth step, during which the first structural element covered with its coating is welded to the second structural element to which it must be assembled.
2. The process as claimed in claim 1 , wherein the fourth step further comprises an operation during which the second structural element is formed by depositing the thermoplastic material at the surface of the first structural element; the welding of the first structural element to the second structural element being carried out at the moment when the thermoplastic material is deposited at the surface of the first structural element.
3. The process as claimed in claim 2 , wherein, formation of the second structural element being carried out by depositing a textile yarn pre-impregnated with a thermoplastic matrix on the surface of the first structural element, the actual welding is carried out at the same time as the formation of the second structural element by locally heating the two structural elements, in the deposition zone of the textile yarn.
4. The process as claimed in claim 1 , wherein the fourth step is carried out by placing the surface of the second structural element in contact with the surface of the first structural element coated with its coating, by placing the two elements in an oven, and by bringing the oven to a temperature sufficient to cause the melting of the thermoplastic materials constituting the coating of the first structural element and the second structural element.
5. The process as claimed in claim 1 , wherein, the coating consisting of a thermosetting monomer further comprises two components to be mixed, the step of preparing the coating consists in mixing a proportion of a thermoplastic material powder with one of the components, then in introducing the other component into the mixture.
6. The process as claimed in claim 1 , wherein said powder consists of a thermoplastic material, selected for its compatibility with the thermoplastic material constituting the second structural element and with the other constituents of the coating.
7. The process as claimed in claim 6 , wherein the second structural element is made of carbon/polyamide PA12 composite, said thermoplastic material powder consists of polyamide PA12.
8. The process as claimed in claim 1 , wherein the proportion of thermoplastic material powder incorporated into the coating is determined so as to obtain the desired tensile strength and the desired failure pattern after tearing.
9. The process as claimed in claim 1 , wherein the step of coating the surface of the first structural element with the coating is carried out by depositing the mixture constituting said coating on the surface of the first structural element and spreading the mixture over said surface so as to form a layer having the desired thickness.
10. The process as claimed in claim 1 , wherein the polymerization phase consists, after coating, in leaving the surface of the first structural element at rest at a given temperature, for the time necessary for the polymerization of the material constituting the coating.
11. The process as claimed in claim 2 , wherein, the formation of the second structural element is carried out by a filament winding technique, the first structural element acting as a winding mandrel for the yarn of composite material, the actual winding means are here combined with means that make it possible to locally heat the deposition zone of the yarn, the thermal energy applied locally being sufficient to bring about the local melting of the thermoplastic material of the second structural element and of the thermoplastic material of the coating, so that the yarn forming the second structural element is welded to the coating that covers the surface of the first structural element.