Mixed-Mode Debonding in CFRP-to-Steel Fiber–Reinforced Concrete Joints

The external bonding of fiber-reinforced polymer (FRP) sheets is a widely used method for strengthening and rehabilitating existing concrete structures. The premature failure of these structures is frequently attributed to debonding at the FRP–concrete interface, highlighting the need for interface studies. In this study, the interface properties of carbon fiber–reinforced polymer (CFRP) and steel fiber–reinforced concrete (SFRC) were investigated. A series of double-shear tests was designed with variations in the initial angle between the CFRP sheet and SFRC to reflect different mixed-mode scenarios. A streamlined cohesive zone model (CZM) was proposed for both the CFRP–SFRC interface slip and steel fiber slip. The complete process of CFRP sheet delamination from SFRC under mixed-mode conditions was simulated using a finite-element software. The simulated results were in good agreement with the experimental results.