Effect of Multiple Stone-Wales and Vacancy Defects on the Mechanical Behavior of Carbon Nanotubes Using Molecular Dynamics

Abstract

Carbon nanotubes (CNT) without any defects possess high mechanical properties. However, CNTs suffer from defects which may occur because of production inabilities, purification or be deliberately introduced by irradiation with energetic particles or by chemical treatment. In this study, mechanical properties of defective single-walled carbon nanotubes (SWCNTs) are studied. Two types of defects i.e. Stone-Wales (S-W) and Vacancy with different defect densities are considered in the present investigation. Molecular dynamics (MD) simulations are implemented to study the mechanical properties like Young's modulus, stress, and strain of armchair SWCNTs with an increasing number of S-W and vacancy defects, by varying their relative position and orientation. In the present work, calculations of fundamental mechanical properties of SWCNTs are performed using the MD simulation software Material Studio Presence of one and four vacancy defects; reduces on an average the tensile strength of CNT by 22.61% and 24.42% respectively, and tensile failure strain by 34.17% and 16.74%, respectively for different diameters. However, in case of Stone-Wales defect this reduction in strength (and strain) is only 11.33% (28.88%) and 13.16% (26.70%) for one and four defects, respectively. It can be concluded that for the same defect densities, vacancy defect deteriorates the tensile strength of nanotubes much more since such type of defect creates hole or void in the nanotubes at which the failure of the nanotubes can easily start.