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.