Forming simulation and failure analysis of CFRP hole-clinched and adhesive hybrid joints

Abstract

Carbon fiber reinforced polymer (CFRP) and aluminum alloy hybrid joints are increasingly used in lightweight structures, but their reliability is often affected by process-induced damage during mechanical joining. This study presents the first coupled forming-damage-failure analysis of hole-clinched adhesive hybrid joints, integrating simulations and experiments to reveal the interaction between joining defects and structural performance. A progressive damage model (Hashin) for CFRP, a cohesive zone model for the adhesive interface, and a Johnson-Cook model for aluminum alloy are combined to simulate joint formation and subsequent loading. Results show that the localized defects such as interfacial delamination, adhesive degradation, and fiber–matrix cracking originate during forming and critically influence tensile response. Cross-sectional and scanning electron microscopy (SEM) observations validate the simulations. Comparative tensile tests demonstrate that hybrid joints outperform adhesive joints, with a 23.9% increase in peak load and a 105.6% improvement in energy absorption. Failure analysis confirms a multi-scale damage evolution involving adhesive degradation, fiber fracture, and interlock deformation. This work establishes a predictive framework linking process parameters, damage evolution, and joint reliability, offering guidance for the optimized design of CFRP-metal hybrid connections in advanced lightweight structures.