Testing and modeling of shear and peel behavior for bonded steel/FRP connections

This paper presents a technique used to evaluate the shear and peel stiffness of an adhesive system that bonds fiber reinforced plastic (FRP) and steel sections. The technique combines experimental results and analytical solutions and involves the simulation of the shear and peel behavior of the adhesive through two continuous spring systems. The experiments involve shear lap testing of FRP sheets bonded to hollow steel sections. A closed form analytical solution was derived for both the in-plane and out-of-plane behavior of the tested FRP sheets. The measured in-plane load-displacement relations were incorporated into the closed form solution to evaluate the spring constant simulating the shear behavior of the adhesive. The out-of-plane behavior of the FRP sheets was identified experimentally through outer face strain and out-of-plane displacement measurements. A curve fitting approach in which the closed form analytical solution was fitted to the measured out-of-plane displacement profile was then used to evaluate the spring constant simulating the peel behavior of the adhesive. The study focused on a methacrylate adhesive system since preliminary investigation has shown it is suitable for applications involving bonding plastic and metal surfaces. The spring constants evaluated in this study can be used to perform detailed modeling of a bonded FRP/steel connection under a general state of loading.