Appendix 3: Thermal Expansion and Elasticity

Abstract

Materials' thermal expansion coefficient a and stiffness (elastic modulus E) are related. In fact a ceramic (stiff material) will expand less than a polymer. This general trend is observed in the a–E chart (Fig. 2.8) where all classes of materials are considered. This trend is mathematically formulated as a ¼ g G rc v 3E where the Grüneisen 'constant' g G is not a constant but varies within one order of magnitude (0.4 < g G < 4), r is the density and c v the specific heat c v % c p . A simple approach to thermal expansion is proposed by Zarzycki 1982 and Kittel 1983. We shall review briefly here their approaches. A3.2 Qualitative Approach