A distinct element method for large scale simulations of carbon nanotube assemblies

Mesoscale simulation techniques are becoming increasingly important due to the interest in complex mechanical problems involving nanomaterials. We propose applying the established macroscopic modeling concept of distinct spherical elements down to the mesoscale to simulate mechanical behavior of carbon nanotube systems. Starting from a microscopic description, the important interactions are encapsulated into two types of contact models that act simultaneously. Each individual nanotube is coarse-grained into a chain of spherical elements interacting by parallel-bonded contacts, representing the short-ranged covalent bonding. An anisotropic van der Waals model with aligning moments acts at the contact between elements located in different tubes to represent the long-ranged interactions. The promising potential of the proposed methodology to model large scale carbon nanotube assemblies is illustrated with several examples, including self-folding of individual nanotubes, mechanical testing of nanotube ropes, self-assembly of a high-porosity nanotube paper, and mechanical testing of a low-porosity nanotube paper.