Experimental investigation of resistance-strain behavior of carbon nanotube fibers and yarns under single and cyclic loads

Carbon nanotube (CNT) fiber made from millions of carbon nanotubes (CNTs) that are highly-aligned in the axial direction, is lightweight and has many desirable properties, such as high strength and high ductility. CNT yarn is fabricated by twisting several CNT fibers to obtain improved electromechanical properties. In this paper, the mechanical behavior and electrical response of CNT fiber and their multi-ply yarns under uniaxial single and cyclic loads were investigated experimentally. The results reveal that the gauge factor of the CNT fiber is about 1.65. For CNT yarn, the sensitivity of the resistance variation decreases slightly with the number of fibers twisted in CNT yarn increasing, while the stability of resistance variation improves. The cyclic test result shows that the relative resistance changes linearly with strain. In addition, preload treatment will improve the stability of electromechanical property for CNT yarn sensors.