Abstract
We consider composites made of two phases and polycrystalline aggregates composed of hexagonal, tetragonal, or trigonal crystals. Within linear elasticity exact relations between effective elastic constants, effective thermal expansion, stored elastic energy, and internal stresses are derived. Two sources of internal stresses are taken into account: external loading and differential or anisotropic thermal expansion. If the fluctuation of elastic constants can be neglected, we obtain solutions for internal stresses and stored energy which are valid for any phase topology.