Cure monitoring and residual stress sensing of single-carbon fiber reinforced epoxy composites using electrical resistivity measurement

Temperature sensing and cure monitoring of the single-carbon fiber/epoxy composites were studied by the measurement of electrical resistivity as a new approach. IFSS and the difference in electrical resistivity (ΔR) between before and after curing were highest for the smallest gauge length of the specimen. As curing temperature increased, logarithmic electrical resistivity of steel fiber increased due to the increased the mean path of the free electron. On the other hand, those of semi-conductive carbon and SiC fibers decreased due to the intrinsic electrical properties based on the band theory. Residual stress built in the fiber was highest at the fiber axis direction, whereas residual stress of built in the matrix was relatively higher for the fiber circumference and radius direction. Residual stresses by the calculating method were consistent well with those from the finite element analysis (FEA). The behavior of electrical resistivity was responded well quantitatively with the change of curing temperature and epoxy matrix modulus. Electrical resistance measurement of conductive fiber composites can be applicable for the useful technique to evaluate cure monitoring and residual stress sensing.