An atomistic based finite bond element model was developed to study the effects of multiple Stone-Wales (5-7-7-5) defects on the mechanical properties of graphene sheets and carbon nanotubes. The element formulation included 8 degrees of freedom reducing computational cost compared to the 12 degrees of freedom used in other finite element models. The coefficients of the elements were determined based upon a previously developed analytical molecular structural mechanics model. The model used the modified Morse potential to predict the Young’s modulus and stress-strain relationship of perfect and defective nanotubes and graphene sheets. The variation of ultimate stress, strain at failure, and Young’s modulus values of carbon nanotubes and graphene sheets were examined as a function of the distance between two defects aligned in the axial and hoop directions. The mechanical properties as a function of the number of defects in the hoop direction were also studied. It was found that the moduli were sensitive to the tube lengths when the total tube length was used to compute the strain. If one uses a local defective length to define the strain, a size independent modulus could be obtained for the defective region. The diameter of the affected region (2nm) from a single defect was defined as the defective length and was used for all different tube lengths examined in the present study. The effects of defect density on mechanical properties of tubes of any lengths were also discussed.

Tensile Behaviors of Graphene Sheets and Carbon Nanotubes with Multiple Stone-Wales Defects. J.R.Xiao, J.Staniszewski, J.W.Gillespie: Materials Science and Engineering A, 2010, 527[3], 715-23