Ultrasonic welding of metal to fiber-reinforced thermoplastic composites: A review

With the increasing application of fiber-reinforced thermoplastic (FRTP) in the industry, many researchers are focusing on the welding of metal/FRTP hybrid structures. Ultrasonic welding is an efficient and cost-effective method for metal/FRTP dissimilar joining. This paper summarizes the current understanding of metal/FRTP ultrasonic welding from four aspects: welding process, joining mechanism, mechanical properties, and galvanic corrosion. It shows that the physical mechanisms, especially the chemical bonding mechanism underlying ultrasonic welding of metal/FRTP are still unclear. Modeling and numerical simulation of metal/FRTP ultrasonic welding is currently lagging behind due to the lack of formulating the metal/FRTP interface interaction. Making macroscopic or microscopic grooves and protrusions on the metal surface is the main method to improve the metal/FRTP joint strength, however, the effect is unstable and quantitative analysis on these grooves and protrusions is required. Overall, the research on metal/FRTP ultrasonic welding still has a lot of space for development.