Helical carbon nanotube arrays: thermal expansion

An earlier investigation [Comp. Sci. Technol. 62 (2002) 419] of the effective mechanical properties of large arrays of carbon nanotubes, assembled in helical array geometries of circular cross-section, is extended for the prediction of the effective thermal expansion coefficients (CTE) of the array. The analysis utilized anisotropic elasticity to examine the behavior of a layered cylinder with layers consisting of discontinuous carbon nanotubes embedded in a polymeric matrix and with collimation direction in each layer following a helical path prescribed by a linear variation in the tangent of the helix angle with radial position. The effective axial, transverse and shearing coefficients of thermal expansion of the array are determined in terms of the degree of twist, number of layers, properties of the carbon nanotube and surrounding polymer matrix.