電気抵抗変化を用いたCFRPマトリックス割れの検知

抄録

For a cryogenic tank of a next generation reusable launching vehicle, a laminated composite tank is one of the key technologies. For the fuel tank made from laminated carbon fiber reinforced composites, matrix cracking is a significant problem that may cause leak of fuel. In the present paper, electrical resistance change method is adopted to detect the matrix cracking of the laminated composites. Tension load in fiber direction causes electric resistance increase, and fiber breakages also cause the electric resistance increase of the CFRP laminates. Moreover, matrix cracking must be detected before charging fuel in the tank. In order to solve these problems, residual electrical resistance under complete unloading condition is measured here. Experimental investigations were performed using cross-ply laminates, and as a result, it can be revealed that the residual electrical resistance shows rapid increase after matrix cracking. FEM analyses were also performed to clarify the mechanism of the increase of electrical resistance due to matrix cracking. Small electrical current exits in the middle 90° ply, and the matrix crack impedes the current. This causes the linear increase of electrical resistance with the number of matrix cracking.