This chapter discusses some aspects of the mechanical and thermal prop
erties of carbon nanotubes. The tensile and bending stiffness constant
s of ideal multi-walled and single-walled carbon nanotubes are derived
in terms of the known elastic properties of graphite. Tensile strengt
hs are estimated by scaling the 20 GPa tensile strength of Bacon's gra
phite whiskers. The natural resonance (fundamental vibrational frequen
cy) 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 car
bon nanotubes will be essentially isotropic, which can be contrasted w
ith the strongly anisotropic expansion in ''conventional'' (large diam
eter) carbon fibers and in graphite. In contrast, the thermal conducti
vity may be highly anisotropic and (along the long axis) perhaps highe
r than any other material. A short discussion of topological constrain
ts to surface chemistry in idealized multi-walled nanotubes is present
ed, and the importance of a strong interface between nanotube and matr
ix for formation of high strength nanotube-reinforced composites is hi
ghlighted.