Superplastic deformation and energy dissipation mechanism in surface-bonded carbon nanofibers

Molecular dynamics simulations are used to understand the role of surface C-C bonds formed by heat treatment on plastic deformation and fracture mechanisms in cone-stacked carbon nanofibers. The simulations predict that the surface bond density linearly relates to the heat treatment temperature. As the surface bond density increases, it is found that tensile strength and ductile fracture energy in carbon nanofibers rise dramatically by more than 65% and 622%, respectively; hence unveiling a regime of superplastic deformation that is unmatched by standard carbon nanotubes and graphitic nanofibers. We demonstrate that both strengthening and superplasticity effects are enabled by the occurrence of surface bond-induced fiber splaying processes that can effectively resist interlayer sliding and crack propagation during deformation. The findings of this computational study have important implications for designing flaw-tolerant nanocomposite systems. (C) 2015 Elsevier B.V. All rights reserved.