Optimization of resistance welding parameters for joining the glass fiber-reinforced polypropylene composites

Thermoplastic composites offer a wide range of potential applications, but effective composite–composite joining remains challenging. This research work optimizes glass fiber-reinforced polypropylene (GF/PP) composite joints made using carbon fiber resistance welding (CFRW), focusing on the relationship between lap shear strength and process parameters. Carbon fiber is chosen as the heating element due to its light weight, better strength and high conduction in the composite joining using resistive welding. Welding current, time, and clamping pressure were optimized to minimize the Polypropylene matrix deterioration. Lap shear strength (LSS) test was used as the output parameter for the optimization process. The microscopic analysis of joints was done to confirm the formation of strong joints with sound fiber–matrix bonding. Statistical analysis was performed to get the combination of process parameters with optimum lap shear strength. Optimal performance was achieved with moderate currents (10–15 A), clamping forces of 400–500 N , and contact times of 35–54 s, yielding minimal cracks and no matrix burning. In contrast, higher currents, excessive clamping, or binder plies degraded strength and microstructure. Overall, CFRW demonstrates strong potential for thermoplastic composite assembly when moderate parameters are maintained. The obtained results show that CFRW produces reliable, cost-effective joints suitable for automotive, and aerospace applications.