Molecular structural mechanics applied to coiled carbon nanotubes

In this paper, mechanical properties of single-walled helically coiled carbon nanotubes are investigated by means of molecular structural mechanics method in ANSYS finite element code. To specify the geometry of coiled carbon nanotubes, a construction procedure is proposed which offers a full control over the morphology of the coiled nanotubes. In this construction approach, first a development map is drawn on a graphene sheet and then this graphene sheet is rolled to form a defected straight carbon nanotube; then, the sides of these defects are stuck together through a nonlinear analysis and finally, the straight carbon nanotube forms into coiled carbon nanotube. Using this construction procedure, several coiled nanotubes are built and their spring constants are calculated. It is shown that the spring constants found are in good agreement with those obtained from density function theory and tight-binding calculations reported in the literature. Moreover, in order to facilitate the simulation of those macroscopic systems which contain coiled carbon nanotubes, an equivalent continuum model is proposed and its mechanical properties are investigated. It is found that, as the tube diameter increases, both spring constant and shear modulus of the coiled carbon nanotube increase.