Development of conductive FRP containing carbon phase for self-diagnosis structures

Abstract

The electrical properties of fiber reinforced plastics (FRP) have been investigated in order to develop structural materials with a damage diagnosis function. Electrical conductivity was achieved by adding carbon particles or carbon fiber as a conductive phase into the FRP. The composites containing carbon particles connected by a percolation structure were found to have advantages in terms of response of conductivity to small strains and the size of the detectable strain range, compared to composites containing carbon fiber. A part of the resistance change in the elongated composites containing carbon particles remained after unloading despite deformation being predominantly elastic. This residual resistance was found to depend largely on morphology of the carbon particles and orientation of the glass fiber. A distinct residual resistance was observed in composites containing spherical carbon particles (carbon black) and glass fibers aligned at an angle of 0 degrees with respect to the tensile direction. Electrical time domain reflectometry (ETDR) was used to locate the damaged region in multilayer composites containing CFRP and GFRP. The position of local damage in the multilayer composites was clearly located to a precision of within 20 mm.