Impulse resistance welding of thermoplastic composites with sandwich-structure heating elements composed of carbon fiber fabric or stainless steel mesh

For the direct current welding of large carbon-fiber-reinforced composite structural components, issues such as poor welding or resin scorching may occur due to the uneven temperature distribution within the joint area. To address these issues from the perspective of the welding process, this study compressed carbon fiber fabric (90CFF) or 304 stainless steel mesh (200SS) with PEI films to prepare sandwich-structured heating elements. Using the Taguchi method and a variance analysis, this study optimized the best process parameters for impulse resistance welding and identified primary factors influencing the welding performance. The optimized 90CFF-CF/PEEK-SET and 200SS-CF/PEEK-SET achieved average Lap-shear strengths of 19.00 MPa and 26.07 MPa respectively. The fracture morphology indicated that the failure mechanics of 90CFF-CF/PEEK-SET and 200SS-CF/PEEK-SET was a combination of interfacial failure and intralaminar HE failure. An infrared thermography analysis of heating elements and the surface of welding joints indicated that appropriate impulse resistance welding parameters could effectively mitigate edge effects.