Carbon nanotube fibers have important application prospects in micro/nano devices, flexible electronics, and high-performance composite materials due to their excellent mechanical and electrical properties. However, the influence of helical structure on the surface dynamic friction behavior of carbon nanotube fibers remains unclear. In this study, helical carbon nanotube fibers with surface angles ranging from 10° to 45° were prepared by a controllable spinning method. Atomic force microscopy (AFM) experiments and molecular dynamics simulations were conducted to investigate the surface friction force distribution under different normal loads. The results show that the surface friction force increases with increasing normal load and exhibits obvious directional dependence. With increasing surface angle, the average friction force first increases, then decreases, and finally increases again, with the 20° sample showing a relatively high average friction force. Surface morphology analysis indicates that the surface angle changes the arrangement of surface bundles, local height fluctuation, and contact state of the fibers, which are important factors affecting the friction force. Molecular dynamics simulation results further show that the higher friction response of the 20° sample is associated with more stable interfacial contact and enhanced local structural response. The surface morphology reconstruction and local contact-state evolution induced by twisting jointly affect the dynamic friction behavior of carbon nanotube fibers. These findings provide a microscopic basis for understanding inter-fiber sliding energy dissipation, regulating interfacial friction, and designing carbon nanotube fiber-reinforced impact-protection composites.
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