Ultrasonic welding of continuous fiber reinforced thermoplastic composites − a review on joining mechanisms, process routes, interfacial reinforcement, and intelligent control

Recent advances in the application of continuous fiber-reinforced thermoplastic composites (CFRTP) across aerospace, automotive, and renewable energy sectors have intensified the demand for rapid, reliable joining technologies. Ultrasonic welding offers an efficient solution, producing high-strength joints with minimal heat-affected zones. This review provides a comprehensive analysis of CFRTP ultrasonic welding, distinguishing itself by systematically addressing the thermodynamic and structural responses of continuous fibers. We establish the fundamental mechanisms by which continuous fibers govern interfacial heat generation, resin flow dynamics, and microstructural evolution—revealing their crucial role in joint performance. Key process parameters across static spot and continuous welding modes are critically examined to establish quantitative correlations between process conditions and joint properties. Additionally, ultrasonic welding for dissimilar CFRTP/metal joints is reviewed, highlighting strategies to overcome disparate material properties. Various interfacial reinforcement approaches, including surface structure design, chemical modification, and hybrid joining, are evaluated for their effectiveness. Furthermore, emerging intelligent monitoring methods and machine learning applications for real-time quality monitoring and process optimization are explored. By integrating materials science, process engineering, and digital technologies within a unified framework, this review delivers insights for advancing ultrasonic welding from laboratory development to industrial implementation in next-generation CFRTP structures.