Electromechanical response (EMR) of carbon nanotube (CNT) fiber is a collective contraction behavior of CNT network, as a consequence of the densification process of assembly structure under electromagnetic force, Ampère force. Load drop at first electric stimulus in EMR test is the manifestation of modulus loss that is opposite to the densification process. The contradiction between modulus loss and collective contraction behavior provides a novel perspective to investigate the microstructure change in EMR. Herein, a structure evolution mechanism was proposed to explain the modulus loss in EMR. Distance between CNTs in some nodes increased under the Ampère force from adjacent CNTs, and the increasing distance weakened the bond effect of van der Waals force, resulting in the appearance of load drop. A mathematical model was applied to fit the experimental stress-strain curves of CNT fiber with different current intensities, and the variation of relevant parameters supported the structure evolution mechanism. Structure densification process driven by Ampère force was also testified as the working principle of EMR by analyzing the thermal expansion in EMR. The relationship between Ampère force, external load, van der Waals force and modulus loss was also discussed.

碳纳米管 (CNT) 纤维的机电响应 (EMR) 是 CNT 网络的集体收缩行为，是在电磁力、安培力作用下组装结构致密化过程的结果。EMR测试中第一次电刺激的负载下降是与致密化过程相反的模量损失的表现。模量损失和集体收缩行为之间的矛盾为研究 EMR 中的微观结构变化提供了新的视角。在此，提出了一种结构演化机制来解释 EMR 中的模量损失。在相邻碳纳米管的安培力作用下，一些节点中碳纳米管之间的距离增加，距离的增加削弱了范德华力的键合效应，导致出现负载下降。应用数学模型拟合了不同电流强度下CNT纤维的实验应力-应变曲线，相关参数的变化支持了结构演化机制。通过分析EMR中的热膨胀，安培力驱动的结构致密化过程也被证实为EMR的工作原理。还讨论了安培力、外载荷、范德华力和模量损失之间的关系。