An experimental investigation of through-thickness electrical resistivity of CFRP laminates

In conjunction with longitudinal and inplane transverse resistivity, the through-thickness electrical resistivity can be utilized in developing simple and cost-effective means of health and usage monitoring of CFRP laminated composites. Most of the research has been concentrated on understanding the electrical conductivity only in the fiber direction. The objective of this work is to investigate the through-thickness electrical resistivity of CFRPs. The paper first describes the external factors that should be eliminated to obtain a true specific resistivity in through-thickness direction. After establishing a procedure to measure the resistivity, the effect of degree of cure, in-plane prepreg tape interfaces within a ply, material system, and ply orientation in a laminate is presented. The following observations are made. The partial curing increases the resistivity. In-plane interfaces within a ply create wide scatter in resistivity values. Significant variation from one carbon-fiber/epoxy system to another can be used for identifying the material system of a CFRP component. The specific resistivity in through-thickness direction increase with increasing angle between the fibers of adjacent plies.