Interfacial resistance-based multifunctional health monitoring on ultrasonic welding of carbon fiber-reinforced thermoplastic composites

Ultrasonic welding is a pivotal technique for joining carbon fiber reinforced thermoplastic polymers (CFRTP), with broad applications across various industries. Despite its importance, current methods for predicting the quality of ultrasonic welding joints are complex, and there is a pressing need for accurate, non-destructive, and cost-effective methods to detect damage during service. This study introduces an innovative, multifunctional health monitoring approach for CFRTP ultrasonic welded joints that leverages the conductivity of carbon fibers at the welding interface. By establishing a correlation between welding strength and post-weld interface resistance, we achieved a non-destructive method for predicting joint quality. The simultaneous monitoring of welding power and interface resistance during the process enabled a detailed analysis of the ultrasonic welding dynamics and melt conditions, allowing for real-time interface monitoring. Furthermore, during lap-shear tests, the method employed resistance monitoring to compare stress–strain curves with resistance variation curves, revealing insights into various damage stages and their associated resistance changes, thus enabling damage sensing during service. The proposed method not only holds promise for quality prediction and damage monitoring of complex connection structures but also has the potential to be integrated with neural network deep learning for real-time optimization of welding processes. This advancement is instrumental in promoting and expanding the application of CFRTP in industrial settings.