Twisted carbon nanotube (CNT) fibers are regarded as an effective assembly for intelligent actuators and artificial muscles, which are inevitable to encounter high-speed collision and impact. In order to reveal the dependence of high-speed mechanical performance on the CNT assembly, the dynamic failure behaviors of untwisted and twisted CNT assemblies under instant stretching are investigated with experimental and numerical methods. The strength of the untwisted and loosely-packed CNT ribbon is more sensitive to strain-rate than densified and twisted CNT fiber owing to its interlaced CNT network. The numerical results demonstrated that the evolution of interior flaws governed the mechanical behavior under different stretching rates. The instant stretching does not allow an efficient stress distribution within the limited time, and thus hinders the flaw evolution, leading to the cascade-like failure mode and a strain-rate hardening effect. It is inferred that the rate-dependent sensitivity may be attributed to the twisted microstructure and untwisted CNT ribbon. This work on the dynamic behavior of twisted CNT ribbon/fiber can help to design the twisted structure under the high-speed applications.

扭曲的碳纳米管（CNT）纤维被认为是智能执行器和人造肌肉的有效组件，它们不可避免地会遇到高速碰撞和冲击。为了揭示高速机械性能对 CNT 组件的依赖性，使用实验和数值方法研究了未扭曲和扭曲的 CNT 组件在瞬时拉伸下的动态失效行为。由于其交错的 CNT 网络，未扭曲和松散堆积的 CNT 带的强度比致密和扭曲的 CNT 纤维对应变率更敏感。数值结果表明，内部缺陷的演变决定了不同拉伸速率下的力学行为。瞬间拉伸不允许在有限时间内有效的应力分布，从而阻碍缺陷演化，导致级联失效模式和应变率硬化效应。据推断，速率相关的灵敏度可能归因于扭曲的微观结构和未扭曲的 CNT 带。这项关于扭曲 CNT 带/纤维的动态行为的工作有助于设计高速应用下的扭曲结构。