THE ROLE OF POTENTIAL FUNCTIONS IN THE MECHANICAL BEHAVIOR OF THE SINGLE WALL CARBON NANOTUBES

Abstract

Carbon nanotubes have been identified as the promising agents in reinforcing composite materials to achieve desired mechanical properties. In this study, three different types of single wall carbon nanotubes (SWCNTs) are subjected to molecular dynamics simulation to investigate their mechanical properties taking different interatomic potential functions. With unmodified Brenner's 2nd generation potential, a brittle fracture for all the SWCNTs is observed. But in tight-binding approach, the chiral and armchair SWCNTs exhibit somewhat extended plastic flow region before failure. With unmodified Brenner's potential, high tensile strength and ductility are observed for the armchair and chiral tubes. Y value of these two tubes is less than 1 TPa but more than 1 TPa for a zigzag tube. Much decrease of tensile strength and strain are noticed when we apply smoothing of the Brenner's potential at cut-off region. Failure stresses are dropped to much lower values for the three tubes. Ductility of the armchair and chiral tubes are also affected considerably by the choice of potential. Applying smoothing in the cut-off region to conserve the energy, the results show better agreement with the experimental findings.