Strengthening and failure mechanisms of individual carbon nanotube fibers under dynamic tensile loading

Rate-dependent mechanical properties of individual carbon nanotube (CNT) fibers are essential for developing advanced anti-collision composites. In this work, a free-falling Hopkinson tension bar was designed to measure the dynamic tensile strength of CNT fiber. The strength of pure CNT fiber is found to be more sensitive to strain rate than that of composite CNT fiber. The dynamic failure morphologies of pure and composite CNT fiber were compared with their quasi-static responses. It was observed that the pure CNT fiber tends to break off at the weakest point, leading to unraveling of fiber along the twisted direction. On the other hand, the infiltrated polymer tends to change the failure mode and rate sensitivity of CNT fibers. Furthermore, high speed deformation analysis under dynamic loading revealed that pure CNT fiber tends to fail at the weakest point while the composite CNT fiber breaks into several fragments.