Debonding development in cracked steel plates strengthened by CFRP laminates under fatigue loading: Experimental and boundary element method analysis

Carbon fiber reinforced polymer (CFRP) laminates can effectively enhance the fatigue life of steel structures. However, few studies have investigated the influence of crack-induced debonding in the CFRP-steel interface on the CFRP strengthening efficiency and the relationship of crack propagation and debonding development. This study experimentally and numerically – with the boundary element method (BEM) – investigated crack propagation and debonding development in CFRP-strengthened cracked steel (Q345, Q460, and Q690) plates. The fatigue test specimens were subjected to a maximum stress of 50% steel yield stress and a stress ratio of 0.1, during which real-time changes in CFRP strain distribution were recorded by digital image correlation (DIC). The CFRP strain gradient calculations showed that crack-induced debonding was crack length-dependent. The numerical fatigue life results were in good agreement with the experimental data when considering debonding and overestimated the experimental data without considering debonding, demonstrating the necessity of considering crack-induced debonding in calculation and design. Furthermore, a relationship was obtained between crack propagation and debonding development.