Investigation of mode I fatigue crack growth in CFRP-aluminium adhesive joints: Effects of loading protocols, fiber bridging, and similitude parameters

This study examines mode I fatigue crack growth and thresholds in CFRP-Aluminium adhesive joints under displacement and load-controlled strategies. Crack growth rates were analyzed across various load/displacement ratios using energy release rate (ERR) and cyclic energy dissipationbased similitudes. Fiber bridging, identified as a fatigue failure mechanism for the first time, led to distinct Paris-like curves in displacement-controlled tests and ERR-based parameters failed to align with the similitude hypothesis. A cyclic energy dissipation-based similitude parameter, incorporating displacement ratio effects, is presented to characterize fiber-bridged fatigue crack growth, addressing variations in fiber bridging and different loading parameters more effectively than ERR-based approaches.