Towards high-quality multi-spot-welded joints in thermoplastic composite structures

Ultrasonic welding is a promising assembly technique for thermoplastic composites and it is well-suited for spot welding. In this study, two typical welding process control strategies, i.e. displacement-controlled and energy-controlled welding, were selected to manufacture spot-welded joints. The influence of different boundary conditions, provided by different welding jigs, on the welding process and the performance of thus-created welded joints were investigated. The optimum input energy was found dependent on the welding jigs, while the optimum displacement was consistent for achieving the maximum weld strength in both welding jigs. Therefore, displacement-controlled welding showed more potential in producing consistent welds in sequential multi-spot welding.