Plastic deformation and failure mechanisms of collapsed-carbon nanotube fibers by coarse-grained molecular dynamic simulations

• A shape-based coarse-grained model of carbon nanotube fiber was established.
• Plastic deformation of carbon nanotube fiber generates after short elastic-like deformation.
• Plastic deformation of carbon nanotube fiber is closely correlated with strain rate of loading.
• Plastic deformation process of carbon nanotube fibers at different strain rates were revealed.

Continuous macroscopic carbon nanotube (CNT) fiber is made of meso-scale bundles, where most CNTs are well aligned along the fiber axis direction. This paper presents a multi-scale model of the CNT fiber by using shape-based coarse-graining technique. Simulations of monotonic and cyclic tensile tests were conducted to study plastic deformation and micro-structural evolution of the CNT fiber. It is shown that the plastic deformation of the CNT fiber generates after short elastic-like deformation under tensile loading, and is closely correlated with strain rate of the applied load. In addition, plastic deformation process of the CNT fiber is determined by different factors in two strain rate ranges, i.e. inter-bundle interaction at low strain rates and mechanical properties of CNT bundles at high strain rates.