Memorizing maximum strain in carbon-fiber-reinforced plastic composites by measuring electrical resistance under pre-tensile stress

Electrical resistance change of fiber-reinforced plastics including continuous carbon fibers has been characterized in tensile tests, in order to provide the composite with the ability to memorize maximum strain. The composites were designed to exhibit obvious residual resistance resulting from fiber fracture, by which maximum strain was memorized after loading–unloading cycles. The composite with a lower volume fraction of carbon fibers was found to be suitable for showing larger resistance change in wider strain range. In order to maintain the increased resistance even after unloading, it was proposed to utilize the composites under pre-stressed condition. The cyclic tensile tests revealed that the pre-stressed composites indicated good sensitivity concerning lower detectable strain limit of less than 0.05% and remarkable residual resistance which brought about memorizing accuracy within ±1%. The applicability of the memorizing capability was demonstrated in a bending test for a concrete beam including the pre-stressed composite.