Ultrasonic welding of fiber reinforced thermoplastic composites: Current understanding and challenges

Ultrasonic welding (USW) provides a cost-efficient method for joining fiber reinforced thermoplastic composite (FRTP) which is increasingly used in various industries as a kind of emerging lightweight material. As a result of the distinct 3D fibrous and porous network structures of FRTP together with the ultrafast and multiphysical features of USW, a great deal of interest has been generated to study the fundamentals and applications of this novel joining technique. This paper presents the current understanding of the USW of FRTP, focusing on the weldability, welding quality, and underlying mechanisms in acoustic transmission, heat generation and joint formation. Then, the challenges to understanding this technique are addressed such as the special physical properties due to fibrous fillers, interphase interaction under ultrasonic energy, and melting and molecular inter-diffusion at the interface. This work contributes to the optimal parameter selection in the USW of FRTP and thereby the wide applications of FRTP.