Impacts from the stacking morphology on the tensile performance of double-walled carbon nanotube bundles

Carbon nanotube (CNT) based fibers/films are envisioned as the building blocks for next generation high-performance composite materials. However, the mechanical performance of the as-synthesized or asprepared CNT bundles are still well below their constituent CNTs. Here, we systematically assessed the influence from the stacking morphology on the tensile properties of double-walled CNTs (DWNTs)-based bundles through molecular dynamics simulations. We found that the bundles containing zigzag DWNTs exhibit higher Young's modulus, but lower yielding strength (and yielding strain) compared with that of the pure armchair DWNT-based bundles. In particular, an initial off-axial angle perturbation in one of the constituent DWNTs induces evident misalignments in other constituent DWNTs, which remarkably degrades the yielding strength and yielding strain of the bundle structures. Following the Hooke's law, the impacts from the stacking morphology on the overall tensile properties of DWNT bundles can be quantitatively predicted by approximating each DWNT as an elastic column approximation. Overall, this work establishes a comprehensive understanding of the influence from the stacking morphology, which not only provides a perspective explanation of the unexpected low performance of as-synthesized CNT bundles, but also shed light on the design of high-performance CNT based bundles. (C) 2021 Elsevier Ltd. All rights reserved.