DEMONSTRATION OF MODEL-BASED CONTINUOUS RESISTANCE WELDING OF APC-2 CARBON FIBRE SPECIMENS

Continuous resistance welding (CRW) of thermoplastic composites (TPCs) simplifies joining of high aspect ratio parts (e.g., stiffeners in a fuselage). This process involves applying an electrical current locally by a moving end-effector through independent conductive connectors which are in contact with an implant located at the weld interface. Heat generated via the Joule effect increases the temperature to melt the material locally while pressure is simultaneously applied to attain a weld. One of the main challenges of TPC welding technologies is the control of the temperature at the interface. This critical process parameter cannot be measured directly without the use of thermocouples (TCs). The objective of this work is to address this challenge by implementing a physics-based finite element model to predict the unobservable parameters (i.e., temperature) and to provide the required parameters for control of the process (i.e., speed). To demonstrate the technology, the welding end-effector is mounted onto a robotic head and the capability of the model to adapt to changing conditions during the process is evaluated. The welded substrates are subjected to a qualitative evaluation via water-coupled ultrasonic testing and C-scan evaluation and cross-section optical microscopy. This work highlights the use of simulation to control the continuous welding process while showing the potential for scale-up of the technology.