Detection of bending direction and amplitude by electrical resistance measurement of axial carbon fibers in braided composite tube

In this paper, electrical resistance measurement (ERM) was used to detect the direction and amplitude of the bending force on fiber-reinforced polymer composite (FRPC) tubes. The method was based on research into the influence of position on the sensing behaviors of carbon fibers (CFs) as separated resistive elements under flexural tests. CFs were inserted into the fabric reinforcement fabricated by a circular braiding machine as axial tows that are separated by bias tows (Kevlar fibers) to serve as sensors. In experiments, samples of FRPC tubes with four axial tows were fabricated and bent at two different angles relative to the distribution of CFs while deformation was maintained in the elastic zone. The resistance change ratios of the CFs varies from ？1.5% to 0.3% and the zero-crossing point on the tube is at 105°. The results showed that CF resistances would change in a particular pattern as the tube was being bent, and the bending direction and force amplitude could be derived from this pattern