Role of cone angle on the mechanical behavior of cup-stacked carbon nanofibers studied by atomistic simulations

JJ Gu and F Sansoz, CARBON, 66, 523-529 (2014).

DOI: 10.1016/j.carbon.2013.09.029

Classical molecular dynamics simulations are used to study the effects of cone angle on mechanical properties and failure mechanisms in thermally-treated cup-stacked CNFs. We find a 22-fold reduction in elastic modulus and 4-fold decrease in tensile strength of cup-stacked CNFs with a wide range of cone angles between 19.2 degrees and 180 degrees. Our results show significant elastic stiffening for intermediate angles between 38.9 degrees and 112.9 degrees, as well as a minimum in tensile strength at a critical cone angle, due to the competition between weak van-der-Waals forces between layers and strong strengthening mechanisms from surface bonds introduced during thermal treatment. Different failure modes in CNFs subjected to tensile deformation are also predicted as a function of cone angle. This study constitutes an important step toward understanding the origin of strength dispersions observed experimentally in CNFs, and suggests that the design of high-strength CNFs can be optimized structurally by appropriately tuning the cone angle. (C) 2013 Elsevier Ltd. All rights reserved.

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