Torsional fracture of carbon nanotube bundles: a reactive molecular dynamics study.

Carbon nanotubes individually show excellent mechanical properties, being one of the strongest known materials. However, when assembled into bundles, their strength reduces dramatically. This still limits the understanding of their scalability. Here, we perform reactive molecular dynamics simulations to study the mechanical resilience and fracture patterns of carbon nanotube bundles (CNTBs) under torsional strain. The results revealed that the fracture patterns of CNTBs are diameter-dependent. The larger the tube diameter, the higher the plasticity degree of the bundle sample when subjected to torsional loading. Tube chirality can also play a role in distinguishing between the CNTBs during the torsion process. Armchair-based CNTBs have higher accumulated energies and, consequently, higher critical angles for the bundle fracture when contrasted with CNTBs composed of zigzag or chiral nanotubes. Remarkably, the CNTB torsional fracture can yield nanodiamondoids.