Mechanical properties of carbon nanotubes form a generalized modified molecular structural mechanics model

Author

Asst. Prof., Dep. Mech. Eng., Shahrood Univ. Shahrood 3619995161, I.R. Iran

Abstract

In this paper, a generalized modified molecular structure mechanics (MSM) model for analysis of carbon nanotubes (CNTs) is put forward. In this method, the interactions between carbon atoms of CNT are modeled using an equivalent beam element of general section. A systematic approach is presented to specify the local directions of each of the beam elements. In contrast to the original MSM method, the contributions from bond angle bending and inversion interactions are distinguished in the present model. For deformation modes corresponding to bond stretching and bond angle bend, nonlinear behaviors according to the modified Morse potential are considered, and for torsion and inversion a linear form is adopted. The proposed model suggests a size and chirality dependence of elastic moduli for CNTs. In particular, with increasing the tube diameter, the Poisson’s ratio of the nanotube decreases and approaches a value of 0.2. Moreover, the nonlinear response of armchair and zigzag CNTs subject to tensile load up to the fracture point is studied. The present model enables capturing the progressive bond breaking and failure of CNTs with Stone-Wales and vacancy defects. The predicted elastic properties and tensile behaviors of nanotubes are found to be very similar to the results reported from the time consuming molecular dynamics simulations.

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Journal of Solid and Fluid Mechanics
Volume 4, Issue 4 - Serial Number 4
May and June 2015
Pages 75-85

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