Resistance preheating for regulating interfacial heat generation and joint performance in ultrasonic welding of CF/PA6 to AA6061

To mitigate locally non-uniform heat generation during ultrasonic welding of CF/PA6 to AA6061 and thereby enhance joint mechanical performance, a resistance-assisted ultrasonic welding (RA-USW) process based on an embedded stainless-steel mesh was proposed. The mesh was resistance-heated prior to ultrasonic loading to regulate the initial thermal and viscoelastic states of the polymer. Control experiments, near-interface temperature measurements, mechanical testing, and morphological characterization were conducted to investigate the effects of resistance preheating on the local thermal response, interfacial melting behavior, and joint performance. The results showed that RUS-80 exhibited the highest two-point temperature uniformity index (98.58%) and the highest observed mean tensile-shear strength (26.16 ± 1.96 MPa). Its mean strength was 217.7% and 129.0% higher than those of conventional ultrasonic welding (USW) and mesh-assisted ultrasonic welding without resistance preheating (M-USW), respectively. Overall, RA-USW effectively regulated the local thermal response and promoted interfacial melting and load transfer, thereby improving joint performance and providing a feasible approach for high-quality ultrasonic joining of CF/PA6 to metals.