CHARACTERIZATION OF A TEST BENCH SYSTEM FOR CONTINUOUS RESISTANCE WELDING OF THERMOPLASTIC COMPOSITE JOINTS

Abstract

Thermoplastic composites (TPCs) are increasingly popular in aerospace structures due to their high stiffness-to-weight ratio, fracture toughness, and weldability. Continuous resistance welding (CRW) can yield high-strength joints in applications with high aspect ratio parts, such as longitudinal or circumferential stiffeners in an aircraft fuselage. In CRW, an electric current is applied locally by an end-effector moving along a continuous conductive implant where temperature is increased via the Joule effect. This implant is placed at the interface to locally melt the TPC and obtain a structural joint. The end-effector also applies consolidation pressure to ensure intimate contact is maintained during melting and solidification. Since the weld interface temperature cannot be measured directly, a physics-based finite element model is used to predict this critical parameter and control the process by manipulating power, pressure, and speed. This paper focuses on the characterization of a CRW system on a test bench to provide experimental data for validation of the physics-based control model. The influence of weld parameters on the welding current are studied. Understanding electrical behavior is critical to attain high quality welds with temperatures that are consistently within the process window across the weld interface. Factors influencing the electrical behavior include electrode contact resistances and heating element dimensions.