On the estimation of mechanical properties of single-walled carbon nanotubes by using a molecular-mechanics based FE approach

Carbon nanotubes (CNTs) have attracted considerable attention in scientific communities due to their remarkable mechanical, thermal and electrical properties (high stiffness, high strength, resilience, etc.). In particular, mechanical properties of single wall nanotubes (SWNTs) have a Young's modulus of about 1 TPa if normalized to their diameter showing why they are widely considered as reinforcing elements in advanced low weight composite structures. The determinations of mechanical properties of SWNT are currently investigated both experimentally and theoretically. However, to determine CNTs mechanical properties in a direct experimental way is a challenging and not economical task because of the technical difficulties and the costs involved in the manipulation of nanoscale objects. Due to the handling difficulty, estimation of mechanical properties using computer simulations are being performed by several author with different approaches. In this work a Finite Element Model of SWNTs based on molecular mechanics theory is proposed to evaluate mechanical properties as Young's modulus, ultimate strength and strain. The novelty of the model lies on the use of non-linear and torsional spring elements, to evaluate SWNTs mechanical properties and tensile failure. With this approach, it was possible to model the bond interaction without making any assumption on non-physical variable, i.e. area, inertia of atom interaction when using beam approach. With the proposed model it was able to understand the evolution of the tensile failure of nanotubes. Moreover, it is important to point out that while most of the fracture evolution studies use molecular dynamics theory and technique, the proposed approach leaded to a minor computational time with the possibility to simulate large atoms system. The calculated mechanical properties show good agreement with existing other work and experimental results.