Mixed-Mode FRP–Concrete Bond Failure Analysis Using a Novel Test Apparatus and 3D Nonlinear FEM

This study introduces a novel test apparatus that can be used to test the adhesive bond between fiber-reinforced polymer (FRP) laminate and concrete in both double shear and mixed mode (shear/peeling). It was deployed to evaluate the behavior of carbon FRP (CFRP)–concrete interfaces at six peel angles. The apparatus is usable with any servohydraulic load test frame and requires only one-half of the traditional concrete block specimen used in both double shear and mixed-mode tests. Experimental results revealed a decrease in bond capacity as peel angle increased. The reduction is quantified using a power-law relationship with respect to the tangent of the peel angle. A three-dimensional (3D) finite-element model utilizing a cohesive zone model to characterize the FRP–concrete interface was developed to corroborate experimental results and carry out parametric studies. The percentage increase in CFRP–concrete bond capacity resulting from an increase in the FRP modulus or its thickness declined as the peel angle increased.