Effect of defects on the local shell buckling and post-buckling behavior of single and multi-walled carbon nanotubes

The local buckling behavior of perfect/defective and single/multi-walled carbon nanotubes (CNTs) under axial compressive forces has been investigated by the molecular dynamics approach. Effects of different types of defects including vacancy and Stone-Wales (SW) defects and their configurations on CNTs with different chiralities at room temperature are studied. Results show that defects largely reduce the buckling stress and the ratio of immediate reduction in buckling compressive stress of the defective CNT to the perfect one, but have little influence on their compressive elastic modulus. SW defects usually reduce the mechanical properties more than vacancy defects, and zigzag CNTs are more susceptible to defects than armchairs. In addition, increasing the number of defects leads to higher deterioration in mechanical properties of CNTs. The results of simulations show that in the case of slender single-walled CNTs, the behavior is primarily governed by the Euler buckling law. On the other hand, in the local shell buckling mode, two distinct behaviors are observed, including the primary local shell buckling mode for intermediate CNTs, and the secondary local shell buckling mode for short CNTs. In the local buckling response, CNTs with smaller diameters sustain higher buckling stresses than CNTs with larger diameters.