Simultaneous Measurement of Multiple Electrical Resistance Changes with Strain of CFRP

Abstract

Strain monitoring of CFRP structure by measuring electrical resistance change has attracted attention over the years. High electrical conductivity of carbon fibers enables to measure the strain by making electrodes on the structure’s surface and using bridge circuit as conventional strain gauge. Electrical resistance change method, however, is difficult to specify the gauge length because electric current is applied directly to the structure, and the current path depends on the stacking sequences, fiber volume fraction, and electrode’s location. It is also difficult to measure the electrical resistance changes at different parts simultaneously because the outputs may interfere with each other due to overlapping of current paths inside the structure. In this study, three electrodes are connected to each bridge circuit to prevent electrical interference when the electrical resistance changes are measured simultaneously, whereas electrical resistance measurements normally use two electrodes. The proposed method puts ground electrodes every other so that current path could be limited between the ground electrodes. Only the strain between ground electrodes affects the electrical resistance output, and it makes simultaneous measurements at different position possible.