Towards In-line Control of Continuous Resistance Welding for Joining Structural Thermoplastic Composites

The continuous resistance welding (CRW) process consists of an end-effector which moves along the length of a weld seam, heating a conductive implant while compacting the joint locally throughout the melt and solidification stages of the thermoplastic material. The performance of the joint has been shown to be highly dependent on the process temperature at the weld interface; however, this cannot be measured directly during the process in a non-invasive manner. Other parameters such as boundary conditions, substructure properties, or part geometry may vary along the length of the weld. As such, a physics-based simulation is developed founded upon an “MSTEP” framework which defines how the materials (M), shape (S), tooling (T), and equipment (E) interact to determine the process (P). Detailed finite element (FE) models are developed for thermal analysis based on the weld geometry, boundary conditions, and previously developed and validated melt/crystallization models for the thermoplastic matrix. Experimental CRW tests are presented to validate simulations and calibrate suitable control variables.