Review: The thermal expansion of composites based on polymers

In the past 25 years, several approaches have been made to the theoretical study of thermal expansion of composites. These approaches range from the empirical, to sophisticated analyses based on applied mechanics. The alternatives are discussed in the following paper, after which the available experimental data are examined in the light of current theory. The approach of Kerner and similar workers shows reasonable success for those systems where the dispersed particles can be treated as spheres, but this case is of limited technological interest. On the other hand, the equation due to Turner most closely represents those systems in which the fillers are fibrous or plate-like in nature. Apart from particle shape, it appears that any general theory must take into account a number of physicochemical variables which have hitherto been omitted.Attention is drawn to the possible relationship which exists between bulk modulus or Young's modulus, and thermal expansion. This has been pointed out earlier by Barker.