Experimental investigation on tensile properties of carbon nanotube wires

Carbon nanotube (CNT) wire is a hierarchical material made by braiding fibers or yarns of CNTs. In this work, tensile experiments were conducted to investigate the elasto-plastic deformation and fracture mechanism of the five-yarn wires. The stress-strain curves, and accordingly the Young's modulus, ultimate stress and strain, of the CNT wires at different strain rates were obtained. The plastic aspect of the CNT wires was emphasized. Then influence of the strain rate on the mechanical performance of the CNT wire under monotonic and cyclic tensile loadings was explored. Morphologies of fractured surfaces and micro-structural damage mechanisms of CNT wires with the variation of strain rates were discussed based on scanning electronic microscopy images. It is shown that the CNT wires have Young's modulus of 1.38 GPa, the yield limit of 6.93-8.99 MPa, the quasi-static strength of 124.4 MPa and ultimate strain of 0.153 mm/mm. And they are affected by the strain rate. Under both monotonic and cyclic tensions, the fracture mode of the CNT wire exhibits a ductile mode at comparatively low strain rates and a brittle mode at comparatively high strain rates.