Développement et caractérisation du soudage par induction en continu utilisant un suscepteur électromagnétique mobile

Abstract

Fusion bonding, also called welding, uses the ability of a thermoplastic polymer to melt or soften when its temperature is risen above the melting temperature (for semi-crystalline thermoplastics) or above the glass transition temperature (for amorphous thermoplastics). In this process, heat is applied at the interface of two parts to be joined. When intimate contact is achieved, molecular diffusion occurs across the interface until it is healed. Finally, the joint cools down, under the application of pressure. Heat can be applied to the joint interface in several ways. This work presents the development of a new continuous induction welding process for glass fibre/poly-ether-imide (GF/PEI) composite. The two laminates to be welded are thin (0,24mm) and flexible. The induction welding process involves the use of a stainless-steel plate named “susceptor”, placed between the two laminates and moved along the weld length with the induction coil. A roller is used to apply pressure and assure a good consolidation. The main advantage of this process is that no foreign material is added to the joint, as the susceptor slides along the weld interface to produce the heat without remaining at the weld interface during the consolidation with the roller. The joints performance is evaluated by tensile testing on lap joints to obtain the failure load of the specimens. These tests lead to the construction of tables, allowing to know the mechanical strength of the specimens according to the welding speed, the intensity of the current in the inductor and the consolidation force of the roller. The fracture zones observed on the tested specimens do not allow the mechanical performance of the welds to be known. The stress concentrations induced at the edges of the joint lead to a fracture in the bulk laminates rather than in the weld itself. The minimum failure load when failure occurs in the laminate, with stress concentrations, is 60% of the strength of the bulk material. The maximum failure load reached is 92 % of the breaking force of the bulk material. In addition, air tightness tests were conducted, and the welds meet the maximum leakage criteria authorized by the project partner company. A numerical simulation of this welding process was performed on ANSYS® to predict the temperature in the weld. A sensitivity study was carried out on various properties of the materials, for which there was considerable uncertainty. Simulated curves fit the experimental curves for a welding speeds between 6 mm/s and 13 mm/s and an intensity between 500 A and 600 A.

Date	28 Nov 2020
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Martine Dubé (Supervisor) & Simon Joncas (Co-supervisor)