Structural Instability of Carbon Nanotube

Abstract

Since Iijima reported MWCNTs in 1991, CNTs have captured the intensive attention of researchers worldwide due to the combination of their expected structural perfection, small size, low density, high stiffness, high strength, and excellent electronic properties. CNTs have been widely adopted as microscopic probing tips (Dai et al., 1996; Hafner et al., 2001), nanocomposites reinforcements (Bower et al., 1998; Jin et al., 1998), nanotweezers (Kim & Lieber, 1999), and nanoactuators (Baughman et al., 1999; Fennimore et al., 2003) due to their slender and high aspect ratio structures. Meanwhile, nanotubes are also highly susceptible to buckling under compression, which is a structural instability. Once the buckling of CNTs occurs, the load-carrying capability would suddenly reduce and lead to possible catastrophic failure of the nanotubes, which significantly limit the loading strengths of the probing tips and compressive strengths of nanocomposite structures. Even the physical properties such as conductance of carbon nanotube can be influenced by the occurrence of buckling (Postma et al., 2001). Hence, it is crucial to understand the mechanism of nanotube buckling and even predict the onset of buckling in order to improve the nanotube applications. A review of the relevant literature shows that significant studies have employed both experimental (Falvo et al., 1997; Iijima et al., 1996; Thostenson & Chou, 2004; Waters et al., 2004) and theoretical (Ru, 2000; Yakobson & Avouris, 2001) approaches to investigate the bucking behaviors of CNTs. However due to the difficulties encountered at nanoscale, the experimental investigation of the buckling behaviors of CNTs remains a challenging problem and individual factors that affect buckling could not be easily identified. In theoretical study, the CNTs are commonly treated as beams or thin-shell tubes with certain wall thickness and elastic constants and, thus, it is difficult to consider the chirality and size effects on buckling behavior of CNTs because the continuum assumption disregards the discrete nature of atomic structures (Ru, 2000; Yakobson & Avouris, 2001). Some researchers attempted to introduce the atomic-continuum method combining the atomic detail in the continuum description and examine the various properties of CNTs (Chang, 2004; Guo et al., 2008; Li & Chou, 2003a, 2003b). The atomic-continuum method could shorten the computational time in larger atomic system. As the fast development and rapid advancement of computers, molecular approaches have become important tools and are widely applied to study the factors that would influence the buckling of CNTs (Buehler et al., 2004; Cao & Chen, 2006a, 2006b; Huh & Huh, 2008; Liew et al., 2004; Ozaki et al., 2000). Although some researchers already discussed various aspects of