OS17-3-2 Monitoring of CFRP matrix crack density using electrical potential change method with multiple probes

Abstract

CFRP laminates are adopted for fuel tank structures of next generation space rockets or automobiles using fuel cells. The matrix cracks may cause fuel leak or triggers of fatigue damages. This requires monitoring system of the matrix crack density. Authors have developed an electrical resistance change method for monitoring of a delamination crack of CFRP laminates. The reinforcement fibers are used as self-sensing system. In the present study, the electric potential method is adopted for the matrix crack density monitoring. FEM analyses are performed to investigate the possibility of matrix crack density using multiple electrodes mounted on the specimen single surface. The FEM analyses reveals that the matrix crack density increases electrical resistance at the target segment between electrodes. Experimental confirmations are also performed here. Material used here is carbon/epoxy prepreg produced from Mitsubishi Rayon Co. Ltd. The prepreg is stacked to make three types of laminates. Specimens of 245 mm x 15 mm were cut from each laminate. Eight electrodes were mounted on the specimen single surface by using silver paste after polishing the specimen surface with sand paper. The outermost couple of the electrodes were used to apply electrical current, and the inner other electrodes were used to measure electric voltage changes. The slope of electrical resistance during reloading was the appropriate tool for the detection of the matrix crack density. As a result, the proposed method is shown to be effective for the matrix crack density monitoring.