MECHANICAL AND THERMAL-PROPERTIES OF CARBON NANOTUBES

Abstract

This chapter discusses some aspects of the mechanical and thermal properties of carbon nanotubes. The tensile and bending stiffness constants of ideal multi-walled and single-walled carbon nanotubes are derived in terms of the known elastic properties of graphite. Tensile strengths are estimated by scaling the 20 GPa tensile strength of Bacon's graphite whiskers. The natural resonance (fundamental vibrational frequency) of a cantilevered single-wall nanotube of length 1 micron is shown to be about 12 MHz. It is suggested that the thermal expansion of carbon nanotubes will be essentially isotropic, which can be contrasted with the strongly anisotropic expansion in ''conventional'' (large diameter) carbon fibers and in graphite. In contrast, the thermal conductivity may be highly anisotropic and (along the long axis) perhaps higher than any other material. A short discussion of topological constraints to surface chemistry in idealized multi-walled nanotubes is presented, and the importance of a strong interface between nanotube and matrix for formation of high strength nanotube-reinforced composites is highlighted.