Study of Poisson Ratios of Single-Walled Carbon Nanotubes based on an Improved Molecular Structural Mechanics Model

摘要

The Poisson ratio is a very important mechanical parameter for both single-walled carbon nanotubes (SWCNTs) and graphene. But, the Poisson ratios of SWCNTs and graphene can not be determined by the direct measurement on the nanoscale specimen, and Poisson ratios of SWCNTs and graphene predicted by different models vary in a huge range. An improved molecular structural mechanics model, where the bond angle variations are modeled by the flexible connections of framed structures, is employed in this paper to predict the Poisson ratios of SWCNTs and monolayer graphene sheets. The present results indicate that the Poisson ratios of both SWCNTs and graphene are chirality dependent, as the Poisson ratio of zigzag monolayer graphene sheet is 0.301, and that of armchair graphene is 0.277. The various values of Poisson ratios of SWCNTs and graphene predicted by different models are summarized and discussed in this paper. The values of these Poisson ratios reported in the literature vary from 0.06 to 1.414 although the longitudinal Young's moduli or tensile stiffness of SWCNTs given by these models are quite close to each other. There is no a standard value of the Poisson ratio of SWCNTs and graphene recognized by researchers up to now, and it can be concluded that the accurate prediction of both size and chirality dependent Poisson ratios of SWCNTs and graphene is still an unsolved issue.