Abstract
The Electrical Resistance Change Method (ERCM) is useful for inspection of CFRP (Carbon Fiber Reinforced Plastic) structures, because electrical conductivity of carbon fibers in them can be used as a sensor for damage detection. Fatigue damages need to be detected using the ERCM because these damages decrease residual strength and reliability of CFRP structures. This study experimentally deals with cyclic loading tests of CFRP laminates using the ERCM. Moreover, the mechanism of electrical resistance change caused by cyclic loading was investigated. First, the electrical resistance change was measured by four-probe method for CFRP laminates with stacking sequences of [0/±45/90]_s and [0_2/90_2]_s. As a result, the electrical resistance of CFRP laminates with the stacking sequence of [0/±45/90]_s decreased with the cycle number. By contrast, that with the stacking sequence of [0_2/90_2]_s increased with the cycle number. The mechanism of the resistance decrease of quasi-isotropic laminates under cyclic loading, which could have not been explained by the conventional theories, was revealed in this study. The test results indicate that residual strain in ±45° plies caused by cyclic loading increases fiber-fiber contact, which decreases resistance.
