Failure mechanism and property improvement of carbon-nanotube fibers

Carbon nanotube (CNT) fibers could retain most of the intrinsic properties of individual CNTs, and thus have potential to enable advanced macro-scale applications, but further improvement on fiber's properties is limited by the less understanding on their failure mechanism. In this work, the strain-rate dependences of CNT fibers' mechanical behaviors were studied in a wide range of the tensile-strain rates. The strain-rate dependences of fibers' mechanical properties are significantly different at high strain rates and low strain rates, suggesting different failure mechanisms. It is found that tube slippage happens at low strain rates, and "cascade-like" breaking due to CNTs mis-alignment dominates at high strain rates. The maximum strength of CNT fibers appears at high strain rates, and is mainly limited by CNT alignment. According to these mechanisms, improvement strategies have been discussed for obtaining reliable and high-performance CNT fibers.