Appl Phys A DOI 10.1007/s00339-011-6385-1 Predicting the nonlinear tensile behavior of carbon nanotubes using finite element simulation Ehsan Mohammadpour · Mokhtar Awang Received: 29 November 2010 / Accepted: 15 March 2011 © Springer-Verlag 2011 Abstract Carbon nanotubes (CNTs) possess extremely high mechanical properties and could be the ultimate rein- forcing materials for the development of nanocomposites. In this work, a Finite Element (FE) model based on the molecu- lar mechanics theory was developed to evaluate tensile prop- erties of single-walled carbon nanotubes (SWCNTs). The deformation and fracture of carbon nanotubes under ten- sile strain conditions were studied by common FE software, Ansys. In this model, individual carbon nanotube was sim- ulated as a frame-like structure, and the primary bonds be- tween two nearest-neighboring atoms were treated as beam elements. The beam element properties were determined via the concept of energy equivalence between molecular dy- namics and structural mechanics. So far, several researches have studied the elastic behavior of CNTs, and its nonlinear- ity is not well understood. The novelty of the model lies on the use of nonlinear beam elements to evaluate SWNTs ten- sile failure. The obtained calculated mechanical properties show good agreement with existing numerical and experi- mental results. 1 Introduction Carbon nanotubes (CNTs) have attracted considerable at- tention in scientific communities. These nanotubes pre- E. Mohammadpour ( ) · M. Awang Mechanical Engineering Department, Universiti Teknologi PETRONAS, 31750 Seri Iskandar, Perak, Malaysia e-mail: eh.mohammadpour@gmail.com M. Awang e-mail: mokhtar_awang@petronas.com.my sented a very promising material at many areas of ap- plications including ultrastrong composite materials and nanomechanical devices, due to their remarkable proper- ties [1–3]. The significant flexibility of their hexagonal net- work allows the system to sustain very high bending an- gles, kinks, and highly strained regions involving axial, compression, and twisting tension [4]. As a consequence, researchers worldwide have tried to study the mechanical properties of single- and multi-walled nanotubes (SWCNTs and MWCNTs) both experimentally [5] and numerically [6–9]. Due to the complicated and costly techniques, ex- perimental investigation of mechanical properties of CNTs is both challenging and not economical. Difficulties in ex- perimental studies due to the small size of nanotubes are further complicated by the sensitivity of CNTs properties to the specifics of a particular produced nanotube that are hardly possible to keep constant. The number of the car- bon monolayers in the wall, the tube diameter, and its he- licity are some of these specifications [10]. However, the very small size makes computational simulations a feasi- ble tool to study and predict mechanical properties of differ- ent types of CNTs [4]. Yakobson et al. [11, 12] and Buon- giorno et al. [4] studied the mechanism of strain release in nanotubes under different modes of mechanical loads: axial tension and compression, bending, and torsion, for both single- and double-walled CNTs using Molecular Dy- namics (MD) simulation. They have demonstrated that MD simulations of large elastic deformations for CNTs are in good agreement with the experimentally observed patterns. They also showed that nanotube behavior beyond Hooke’s law could be well described by a continuum model with properly chosen parameters, e.g., Poisson’s ratio ν = 0.19, Young’s modulus E = 5.5 TPa, and tube thickness, t = 0.66 Å [10].