Enhanced Adhesion Between a Carbon Fiber Heating Element and a Polyphenylene Sulfide Laminate via Ultrasonic-Assisted Resistance Welding

Resistance welding, a method widely used for joining thermoplastic composites, involves embedding a carbon fiber heating element (HE) with high compatibility with resin into the joint interface of polyphenylene sulfide (PPS) laminates to perform the welding. However, there is an uneven temperature distribution in the welding region, which leads to the formation of non-fused regions and affects the joint quality. This study used carbon fiber fabric as HE and applied ultrasonic assistance in the final stage of the welding process to improve heating distribution. The results indicated that the maximum lap shear strength (LSS) of 17 MPa was achieved at a fabric areal density of 120 g/m² without ultrasonic assistance. Through ultrasonic application, the LSS was enhanced by 23% to 21 MPa while simultaneously reducing the required welding time by 25%. The application of ultrasonics introduces a temperature compensation mechanism, which reduces the temperature difference between the overlap center and edges and promotes the resin flow at the overlap edges, resulting in a significantly improved joint quality compared to joints without ultrasonics.