Multiphysics Modeling and Process Tailoring of Ultrasonic Welding for Thermoplastic Composites

This study presents a sequentially coupled thermo–mechanical modeling framework designed to accurately and efficiently predict the temperature evolution and guide the selection of processing parameters in ultrasonic welding (USW). Key innovations include computing viscoelastic and frictional heat generation based on the dynamic mechanical response of composite adherends and energy director under ultrasonic excitation. The temperature-dependence of both heat-generation mechanisms is incorporated by using temperature-dependent thermal and mechanical properties and continuously updating the heat-generation calculations throughout the welding process. Material data were obtained from the literature, and a hammering factor was calibrated using welding trials at a 70μm amplitude. Model predictions were validated against infrared thermography from experiments conducted at a 90μm amplitude, showing close agreement in both magnitude and spatial//temporal trends of the temperature field. In addition, the simulated welded area closely matched the experimentally measured area, demonstrating the model’s capability to link process conditions, material behavior, temperature evolution, and weld quality. Finally, the validated model was used to determine an optimal welding time that minimizes fiber distortion while improving process efficiency. Implementing this predicted optimum in subsequent experiments resulted in improved weld quality and reduced processing time, confirming the value of the proposed framework for physics-based parameter selection in ultrasonic welding.