Investigating the effects of length, diameter and chirality on the mechanical properties of defective carbon nanotubes

Carbon nanotubes are obtained from rolling a graphene sheet of a given size and at a specific direction. Due to the strong carbon-carbon covalent bonds, nanotubes have unique mechanical and electrical properties. In this paper, using finite element and molecular mechanics methods, the covalent bonds between the carbon atoms in the nanotube have been modeled using linear beam element. Carbon nanotubes with different diameter and length ranges have been analyzed. The effects of nanotube length, diameter and chirality on nanotubes Young's and shear Modului have been investigated, independently. Also, the decrease in nanotube modulus due to the number and position of vacancy defects has been determined. The results show that, nanotube diameter has a larger effect, compared to nanotube length, on elastic properties, especially Young's modulus. Comparing the results obtained for armchair, zigzag, and chiral nanotubes, vacancy defect had the most effect on chiral nanotube Young's modulus, with a chiral angle of 49.15 degrees.