Mechanical Properties of Carbon Nanotubes with Randomly Distributed Vacancy Defects

Abstract

Carbon nanotubes (CNTs) o er very high mechanical properties with huge scatter. The scatter in the properties is believed to occur mainly due to the defects originated inherently during production. CNTs under a tensile load having randomly distributed vacancy defects are simulated to investigate the e ect of the spatial distribution of defects on the mechanical properties. A simple random unit generation method was used to allocate the defects randomly in the single-walled nanotube's structure. The simulation was carried out a using classical molecular dynamics (MD) simulation technique in atomic scale. Defect density of 1 % reduced the failure strength, the failure strain and Young's modulus of CNTs by as much as 42 %, 65 % and 2 %, respectively, while a defect density of 8 % lowered the properties by as much as 52 %, 71 % and 14 %, respectively. The scatter in the properties due to the random distribution of the defects was found to increase with increasing number of defects in the SWNTs. For example, for a defect density of 8 %, the standard deviations of the data for 20 sample simulations having di erent distributions normalized to the mean values calculated for the failure strength, the failure strain and Young's modulus were about 11 %, 20 % and 8 %, respectively. The defect arrangement in the SWNT's structure is one of the key factors in determining its mechanical properties and the population of defects.