Influence of epoxy adhesive on the weldability and mechanical behavior of 22MnB5 in weld bonding

Weld bonding is a hybrid joining technique that integrates structural adhesive bonding with resistance spot welding, combining the benefits of both chemical adhesion and metallurgical fusion. This study presents a comprehensive experimental and numerical framework for analyzing the weld bonding process in 1.5-mm-thick 22MnB5 steel sheets. A primary focus is placed on the rheological behavior and thermal degradation of the epoxy adhesive during squeeze-out, which was characterized experimentally and implemented into a finite element model using Simufact Forming. The model accurately captures the adhesive flow, weld nugget formation, surface indentation, and hardness evolution by coupling temperature-dependent material properties with phase transformation kinetics. Experimental validation confirms the simulation’s ability to predict nugget size (within 0.3 mm accuracy), adhesive spreading, and joint performance under lap shear and cross tension loading. Weld-bonded joints demonstrated enhanced mechanical performance compared to adhesive bonding and resistance spot welding alone, owing to increased nugget size and improved energy absorption. The integrated modeling strategy offers a robust predictive tool for optimizing hybrid joining processes in automotive and structural applications involving ultra-high-strength steels (UHSS).