Experimental study on the effect of steel yielding on the bond behavior between CFRP and steel plate

To study the effect of steel yielding on the bond behavior between carbon fiber reinforced polymer (CFRP) and steel plate, a series of tensile tests and finite element analysis were conducted with CFRP-steel double strap bonded joints. With the steel plate thickness and bond length as the variables, the load-displacement curves, effect bond length and failure mode of the bonded joints were obtained through static tensile testing. The results show that the joints with 15 mm thick steel plate maintains elastic until failure. On the other hand, joints with 8 mm thick steel plate with bond length longer than effective bond length exhibit steel yielding when fail. The load-displacement curve becomes nonlinear and ductile with the yielding of the steel plate and the displacement at failure is extensively increased. The failure mode of the bonded joints is CFRP delamination when steel is not yield and is a combination of CFRP delamination and steel-adhesive interface debonding when steel is yield. And the area of steel-adhesive debonding is increasing with a larger area of steel yielding. According to the joint and material properties adopted in this work, when the joint with 8 mm steel plate yields, its maximum failure displacement is about 4.2 times of the joint with 15 mm thick steel plate, but the capacity of the 8 mm joint is only 69.92% of the 15 mm joint. In other words, the ductility of the joint due to steel yielding is achieved at the cost of reduction in capacity. From the results of finite element analysis, it can be found that the failure position would move to bonded end with a larger area of steel yielding and the effective bond length would be shorter. © 2022, Editorial Office of Acta Materiae Compositae Sinica. All right reserved.