Molecular Dynamics Simulations of Twisting-Induced Helical Carbon Nanotube Fibers for Reinforced Nanocomposites

Carbon nanotube fibers have attracted much interest because of their outstanding multifunctional properties. In this work, double-helix carbon nanotube fibers (DHCNFs) assembled by combined self-twisting and whole-twisting processes are presented, and their mechanical properties were studied based on atomic simulation. We found that the self-twisting of carbon nanotubes (CNTs) can lead to interesting intertube entanglements, with the formation of a helical structure. In addition, the twisting process can cause a remarkable decline of the mechanical properties of CNTs owing to their hollow structure collapse, thus deteriorating the tensile mechanical performances of DHCNFs. Meanwhile, by tuning related twisting parameters, different fracture failure modes, including simultaneous and stepwise breakages, can be found. More importantly, it was revealed that, as nanoenhancements, the helical morphology of DHCNFs can effectively enhance the interlocking effect between CNTs and the matrix, thereby improving the interfacial strength and toughness of DHCNF-reinforced nanocomposites. This work systemically studied the effect of the twisting operation on the mechanical properties of DHCNFs and provided an innovative way of simultaneously enhancing the strength and toughness of CNT-based nanocomposites.