Coupled body-interface nonlocal damage model for FRP detachment

The present paper deals with the modeling of the detachment mechanism of Fiber Reinforced Polymers (FRP) reinforcements from cohesive, i.e. quasi-brittle, materials. A new plastic-damage model able to describe the main features characterizing the macroscopic behavior of cohesive materials is presented. To overcome the analytical and computational problems induced by the softening constitutive law, an integral-type regularization technique is adopted. The evolution of the plastic strain is governed by introducing a suitable yield function. For the FRP-quasi brittle support interface, a cohesive zone model, which accounts for damage, unilateral contact and friction effects, is developed. The provided interface formulation is also able to consider the influence of the degradation state of the support on the interface collapse mechanism, i.e. the coupling of the interface and body damage, evaluated on the bond surface. A numerical procedure is presented and implemented in a finite element code. Some numerical applications are carried out in order to assess the performances of the proposed model, presenting a comparison with experimental data.