Theoretical and experimental study on cracked-dependent debonding behavior between CFRP and cracked steel substrate using cohesive zone model

Abstract

The adhesively bonded CFRP (Carbon Fiber-reinforced Polymer) on cracked steel substrate is prone to premature debonding failures due to significant stress concentration resulting from crack opening displacement (COD). This paper presents a theoretical methodology for the crack-dependent bond response of externally bonded CFRP on cracked steel substrate. A bi-linear bond-slip relationship of adhesive is adapted to model the non-linear property of the CFRP-to-steel interface as a cohesive zone. Closed-form solutions of crack-dependent interfacial stress and CFRP stress are derived, considering the elastic, softened, and debonding phases of adhesive. The presented formulations are verified through experiments and numerical simulations. Additionally, the crack-dependent stress distribution is measured by PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) distributed optical fiber sensors in the experiments. The results show good agreement between the analytical solution, measured strain, and finite element (FE) results. Within the range of commonly used design parameters, the interfacial elastic stiffness in the adhesive bond-slip relationship has a significant effect on the peak CFRP stress and interface debonding.