Effect of Carbon Fiber Fabric Areal Density on Resistance Welded Joint of Thermoplastic Composites

ABSTRACT Resistance welding (RW) is widely used for joining thermoplastic composites. The heating element (HE), placed between two adherends, generates heat during the welding process and remains in the joint as a load‐bearing unit, playing a crucial role. While carbon fiber HE exhibits excellent compatibility with composites, uneven temperature distribution and excessive HE thickness often compromise joint integrity. To address these challenges, this study investigated the effects of four carbon fiber fabrics (CFFs) with lower areal densities on the fusion behavior of fiber‐reinforced thermoplastics (FRTP). The results indicate that increasing fabric areal density reduces the rate of temperature rise during welding, enhances joint uniformity, and prevents defects such as voids caused by substrate thermal degradation and localized high temperatures. Lap shear strength (LSS) tests revealed that when 90 g/m ² CFF was welded for 90 s, the joint achieved a maximum LSS of 15.63 MPa. The observed failure mode was intralaminar failure, characterized by internal tearing of the HE and fracture between the HE and the laminate. These results elucidate the significant impact of CFF areal density on improving the efficiency and performance of resistance welding in thermoplastic composites.