Transverse mechanical properties of single-walled carbon nanotube crystals. Part I: determination of elastic moduli

Carbon nanotubes naturally tend to form crystals in the form of hexagonally packed bundles. An accurate determination of the effective mechanical properties of nanotube bundles is important in order to assess potential structural applications such as reinforcement in future composite material systems. Although the intratube axial stiffness is on the order of 1 TPa due to a strong network of carbon–carbon bonds, the intertube interactions are controlled by weaker, nonbonding van der Waals forces which are orders of magnitude less. A direct method for calculating effective material constants is implemented in the present study. The Lennard– Jones potential is used to model the nonbonding cohesive forces. A complete set of transverse moduli is obtained and shown to exhibit a transversely isotropic constitutive behavior. The predicted elastic constants obtained using the direct method are compared with available published results obtained from other methods.