碳纳米管（CNT）薄膜以其低密度、优异的柔韧性以及高的比强度、比模量，在新一代的防护装备研制中有重要的应用价值。本文主要通过多尺度实验测试及粗粒化分子动力学模拟（CGMD）等方法，对碳纳米管薄膜的动态力学性能进行了研究。主要研究内容包括：

（1）利用静载拉伸试验机、小型霍普金森拉杆，得到了不同应变率下CNT薄膜的拉伸强度特征。拉伸后CNT薄膜断口的CNT纤维出现被拉直和断裂破坏特征。在拉伸载荷下CNT薄膜的强度与薄膜厚度没有明显的关系，但是表现出明显的应变率强化效应。准静态拉伸强度约为62MPa；应变率在1000s^-1时，拉伸强度约为96MPa；应变率在2000s^-1时，拉伸强度约为116MPa。

（2）开展了强激光驱动微颗粒冲击条件下，CNT薄膜冲击防护性能的研究。发现CNT薄膜通过范德华界面失效及CNT纤维的重取向展现出超高的比吸能。当冲击速度在120~200m/s时，CNT薄膜的比吸能随冲击速度的增加而增加，比吸能范围为0.62~2.93MJ/kg，远高于其他传统的防护材料。在较低冲击速度下，比吸能随厚度的增加而增加；在较高冲击速度下，比吸能随厚度的增加而减小，表现出异常厚度依赖性。

（3）建立了CGMD模型，来研究CNT薄膜的速度与厚度相关的吸能行为与机制。计算得到的比吸能随冲击速度、薄膜厚度的变化关系与实验观察的结果一致。通过分析冲击过程中CNT薄膜的能量耗散模式、变形过程以及动能影响范围，证明了动能主导厚度相关的耗能模式转变。在较高冲击速度下，由于CNT薄膜表面发生冲塞破坏而相对降低了材料的比吸能，解释了尺寸效应的转变机制。

Carbon nanotube (CNT) films have promising application in protective equipment due to its low density, excellent flexibility, high specific strength and specific modulus. In this thesis, the dynamic mechanical behavior of CNT films is studied by multi-scale experiments and coarse-grained molecular dynamics (CGMD) simulation. The main research contents are as follows:

(1) The tensile strength of the CNT films under various strain rates are measured using a quasi-static tensile testing machine and a mini-split Hopkinson tensile bar (mini-SHTB). After tensile tests, CNTs at the fracture of CNT film are straightened and broken. The results show that the tensile strength of the CNT films is almost independent to the thickness of the films. However, it shows obvious strain rate strengthening effects. The tensile strength of the CNT films is about 62MPa under quasi-static loading conditions. It is about 96MPa at the tensile strain rate of 1000s^-1, and increases quickly to 116MPa with increasing the tensile strain rate to 2000s^-1.

(2) The impact resistance of the CNT films is measured by laser-induced particle impact testing (LIPIT). The results show that the failure of the van der Waals interfaces between CNTs and the reorientation of CNT fibers renders the CNT film ultra-high impact resistance. For the impact velocity of 120~200m/s, the specific energy absorption (SEA) of the CNT films increases with increasing the impact velocity. The SEA varies from 0.62 MJ/kg to 2.93 MJ/kg, which is much higher than that of other traditional protective materials. In addition, the SEA increases with increasing the thickness of the film for low impact velocities. However, it increases with decreasing the thickness of the film for relatively high impact velocities, showing an anomalous thickness dependence.

(3) The energy dissipation mechanisms of the CNT films are investigated using coarse-grained molecular dynamics (CGMD) simulations, showing the same impact velocity and size-dependent SEA of the CNT films as observed in experiments. By analyzing the energy dissipation mode, the deformation behavior, and the influence area during the impact process, it is proved that kinetic energy dominates the deformation modes of the CNT films. Under high impact velocity, the plugging failure mode near the surface of the CNT films results in the deterioration of the impact resistance, leading to the decrease of the SEA with increasing the thickness of the CNT film.