Enhancement of pre-embedding SiC particle on interfacial strength in ultrasonic welded carbon fiber reinforced thermoplastic composite joints

Enhancing the interfacial bonding strength of ultrasonic welded joints in continuous carbon fiber-reinforced thermoplastic composites (CFRTP) is critical for their industrial application. This study introduces a novel reinforcement method by pre-embedding silicon carbide (SiC) particles at the welding interface, which significantly improves the interfacial strength and overall mechanical performance of CFRTP joints. The embedded SiC particles induce a pinning effect that facilitates load transfer among fibers, and suppresses crack propagation, and enhances the joint's lap shear strength. Through comprehensive evaluations, including lap shear tests, morphological analysis of fractures and welding seams, and temperature monitoring at the welding interface, the fracture modes and heat generation mechanisms of SiC particle-reinforced ultrasonic welded CFRTP joints are systematically investigated and clarified. The optimal conditions for reinforcement are identified as 120# SiC particles (with particle size of 120 μm) at a deposition amount of 20 mg, achieving a joint strength of 22.35 MPa at the welding time of 1.0 s, which corresponds to an enhancement of 23.85 % compared to non-reinforced joints. This scalable approach addresses critical demands in aerospace, automotive, and renewable energy sectors through structurally sound, rapid joining of lightweight CFRTP components. In contrast, graphene powder, due to its smaller size, two-dimensional layered structure, and interlayer slippage behavior, fails to enhance the interfacial bonding strength, resulting in shear failure at the interface and reduced mechanical performance. These findings underscore the importance of particle morphology and characteristics in the context of interfacial bonding strength enhancement.