Device and process for welding thermoplastic composite material parts

A process for the thermoplastic welding of at least one first part made of thermoplastic composite material with at least one second part (made of thermoplastic composite material by melting the resin of the matrices of said at least one first part and at least one second part by means of a magnetic induction head, comprising the successive steps of:

• positioning at least one first part in a cavity, having a shape suitable for holding said at least one first part, of an insulating insert disposed within a nonmagnetic metallic support of a die of a thermoplastic welding tool, the insulating insert corresponding to an interface between the at least one first part and the at least one second part where a thermoplastic weld seam is formed;
• placing metal inserts on the surf aces of the at least one first part corresponding to the bonding zones in which thermoplastic weld seams are formed;
• positioning at least one second part on the die in the relative position that said at least one second part should have with the at least one first part in the assembly to be produced;
• arranging a bladder so that said bladder and the die define an airtight volume wherein the at least one first part and the at least one second part are enclosed;
• creating a partial vacuum in the airtight volume in order to create, under the effect of the pressure of the air outside the airtight volume, a bearing force of the at least one second part on the at least one first part, at least in the bonding zones;
• contactless displacement of the magnetic induction head close to all the bonding zones so as to create in the metal inserts induced currents and a production of heat via the Joule effect so as to give rise to the local melting of the resin of the matrices of the composite material of the first and second parts, while maintaining the partial vacuum in the airtight volume;
• and,
• after cooling the welded parts to an ambient temperature, or at least to a temperature substantially below a softening point of the resin of the material of said parts, breaking the partial vacuum, disassembling the bladder and removing the assembly of parts welded together from the tool,
• wherein:
• sacrificial parts are positioned at ends, following a direction for producing a weld seam, of the at least one first part in the cavity, formed for the purpose, made in the insulating insert;
• the placing of metal inserts on the surfaces of the at least one first part is extended by extensions at ends of said metal insert on surfaces of said sacrificial parts;
• a nonstick film is deposited between the extensions and each of the first parts and second parts with which said extensions are in contact in position in the tool;
• the displacement of the magnetic induction head in order to produce the weld seam is extended at each of the ends of the weld seam on either side of a working length of said weld seam so as to begin and end the heating of the parts to be welded level with the sacrificial parts.