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Twisting is a simple and effective method for assembling individual carbon nanotubes (CNTs) into high-strength, tough, and continuous CNT yarns. However, the unexpectedly low stretching performance of the resulting carbon nanotube bundle (CNTB) structures is a problem that must be resolved. In this study, we investigated the impact of twisting on the structure and stretching performance of CNTBs through molecular dynamics (MD) simulations while considering the presence of disclinations within the CNTB structure. We found that disclinations nucleate in twisted CNTBs, and the longer the disclination line in CNTBs, the lower the Young's modulus. The presence of disclination lines in the twisted CNTBs may be an important reason for the decrease in the tensile properties of the CNT yarns. Although the theoretical equations in textile field can be applied to describe the mechanical properties of CNT yarns, there are significant relative errors between the equations and the MD simulation results presented herein. Therefore, we revised the equations based on the simulation results to reduce the relative error for seven-layer CNTBs to less than 10%. This paper provides new insights into the low tensile performance of CNT yarns and offers potential guidance for the production of high-performance CNT yarns through twisting.
Lu et al. (Thu,) studied this question.