Carbon nanotubes exhibit remarkable mechanical, thermal and electrical properties. These properties, combined with their low density and high aspect ratio, make carbon nanotubes an ideal candidate for reinforcing composites with superior mechanical and physical performance. However, because of the difficulties in experiments and theoretical analyses due to their extremely small size, there is still a lack of the fundamental knowledge regarding the strength and failure behavior of carbon nanotubes.
In this paper, we present an innovative method for modeling the deformation of carbon nanotubes. Fundamental to this method is the notion that carbon nanotubes are geometric, cage-like structures where the load-bearing members are connected at a number of joints. It seems then a logic approach to modeling the deformation of carbon nanotubes at the atomistic or molecular level by emulating the approach in engineering structural analysis. The primary bond between two nearest-neighboring atoms forms the load-bearing member whereas the individual atom acts as the joint of the related load-bearing members. We term this approach the "molecular structural mechanics" method.
This paper reports the following aspects of the mechanical behavior of carbon nanotubes. First, the molecular structural mechanics method has been applied for the prediction of elastic modulus of carbon nanotubes. The results are in good agreement with those of more computationally intensive methods, such as molecular dynamics simulation, tight-binding model and density functional theory. Next, this method enabled us to model the strength of single-walled carbon nanotubes with or without Stone-Wales defects. Finally, we applied this method to analyze the compressive buckling of carbon nanotubes. The complete load-displacement relationship including pre-buckling and post-buckling has been obtained. The effects of tube diameter and chirality on the buckling have also been examined.