The influence of Stone–Thrower–Wales defect on vibrational characteristics of single-walled carbon nanotubes incorporating Timoshenko beam element Reza Maleki Moghadam a,n , Seyyed Ahmad Hosseini a , Manouchehr Salehi b a New Technologies Research Center, Amirkabir University of Technology, PO Box 1591633311 Tehran, Iran b Department of Mechanical Engineering, Amirkabir University of Technology, 424 Hafez Avenue, Tehran, Iran HIGHLIGHTS  The influence of STW defect on the vibrational characteristics of SWCNT's is scrutinized.  Effects of various parameters on natural frequencies of defective CNT are studied.  The significant influence of orientation of C–C bond concentrated at STW defect is observed.  The critical position of defect is revealed near the fixed end for both boundary conditions. article info Article history: Received 2 March 2014 Received in revised form 6 April 2014 Accepted 13 April 2014 Available online 24 April 2014 Keywords: Single-walled carbon nanotube Vibrational characteristic Stone–Thrower–Wales defect Timoshenko's beam element Finite element analysis abstract The influence of Stone–Thrower–Wales (STW) defect is scrutinized on the fundamental frequency of single walled carbon nanotube invoking molecular mechanics approach. The modal finite element analysis is carried out by employing Timoshenko's beam element to construct the Carbon–Carbon bond of CNT lattice structure. Hence, three configurations of defective CNTs are taken into account by applying two kinds of boundary conditions. The results demonstrate that the frequencies are dependent on boundary conditions, CNT length, chirality and defect position as the critical position of STW defect is near the fixed end for both cantilever and bridge boundary conditions. Likewise, the results reveal that the natural frequencies extremely depend on the orientation of C–C bond concentrated at the STW defect. Meanwhile, by increasing the number of defects, the models indicate different behaviors ascribing to bond rearrangement imposed by STW defect. The results are in good agreement with those from other literatures. & 2014 Elsevier B.V. All rights reserved. 1. Introduction By discovering carbon nanotubes (CNT) a new way has been paved toward nanostructures and nano electro mechanical sys- tems (NEMS) [1–4]. Owing to extraordinary physical, mechanical and electrical attributes, CNT's can be used as reinforcements, oscillators and sensors [5–7]. It is worth mentioning that by adding small portion of CNT's to neat resin, the fundamental frequencies of CNT reinforced composite can be improved remark- ably without striking changes in mass density of material [8,9]. Therefore vibrational behavior should be analyzed accurately as one of the fundamental characteristics of intact/perfect CNT's. From the modeling technique point of view, there are various procedures to construct perfect or defective CNT's. Gibson et al. [10] reviewed the vibrations of CNT's and their composites. Exerting an atomistic modeling method and molecular structural mechanic the natural frequencies of single-walled carbon nano- tube (SWCN) have been calculated in some researches [11,12]. Sohlberg et al. [13] studied the free vibrational properties of perfect CNT's by using continuum model approach. Wang et al. [14] investigated free vibrations of MWCNTs using Timoshenko's beam model which the results revealed that the frequencies are significantly over-predicted by using Euler's beam theory when the aspect ratios are small and when considering high vibration modes. A free and forced vibrational analysis of SWCNT has been assessed by Arghavan and Singh using space frame elements with extensional, bending and torsional stiffness properties [15]. Hu et al. presented a review of recent studies on continuum Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/physe Physica E http://dx.doi.org/10.1016/j.physe.2014.04.008 1386-9477/& 2014 Elsevier B.V. All rights reserved. n Corresponding author. Mobile: þ98 9122714298. E-mail address: Reza.malekimoghadam@gmail.com (R. Maleki Moghadam). Physica E 62 (2014) 80–89