Effect of fatigue loading on bond strength between CFRP sheets and steel plates

This paper describes a series of tests on Carbon Fiber Reinforced Polymers (CFRP) sheet bonded steel plates. The specimens were tensioned to failure after enduring a pre-set number of fatigue cycles at various load ratios (defined as the ratio of the maximum load in the fatigue test to the corresponding static strength). The aim of the study is to investigate the effect of fatigue loading on bond strength and failure modes. Both normal modulus (E = 240 GPa) and high modulus (E = 640 GPa) CFRP sheets were used in the tests. The experimental results were compared with those for specimens subjected to static tension alone. It was found that the failure modes of the CFRP-sheet bonded steel plates were not affected greatly by the fatigue loading except for those bonded with high modulus CFRP, where fiber fracture extended over more than one cross-section. The fatigue loads appear to have less effect on the bond strength of high modulus CFRP-sheet bonded steel plates. Reduction in bond strength from 10% to 20% was observed for normal modulus CFRP-sheet bonded steel plates when the load ratio is less than 30%