Molecular dynamics study on effects of aspect ratio of carbon nanotubes in thermosetting epoxy based nanocomposites including modeling of crosslinking process

A comprehensive modeling and simulation approach using molecular dynamics (MD) is presented in this paper. The influence of aspect ratio of carbon nanotubes (CNTs) in thermosetting epoxy is studied using MD. The thermo-mechanical properties of epoxy models reinforced by CNTs with various aspect ratios are extracted. CNTs with the higher aspect ratio increase stiffness of the epoxy resin with facilitating premature yield in tension while a noticeable degradation in thermal properties is evidenced. The evolution of internal energy during straining shows that CNTs prolong the constant transition rate of dihedral and van der Waals energy in the elastic region. This might delay conformational changes of epoxy molecules to the lower energy level. Free volume and pair distribution function studies of the molecular models with CNTs compared with the neat epoxy model provide the plausible conclusion that the steric hindrance of CNTs in the three-dimensional epoxy molecular domain may result in the less dense structure of the epoxy.