Micromechanical Thermoelastic Model for Sandwich Composite Shells made of Generally Orthotropic Materials

Analytical solutions based on the two-scale asymptotic homogenization method for thermoelastic problem pertinent to general thin composite shells are obtained. The model allows the determination of both local fields and effective elastic and thermal expansion coefficients of composite sandwich shells made of generally orthotropic materials. Orthotropy in the material characteristics leads to a significantly complex set of thermoelastic local problems and is considered for the first time in the present article. First, a 3D-to-2D general asymptotic homogenization composite shell model based on a set of four unit-cell problems is derived. Secondly, the expansion of the model is continued to the further derivation of formulae for the forces, moments, displacements, strains, stresses, and effective thermoelastic coefficients that are representatives of the sandwich shell. Finally, the theory is illustrated by examples pertaining to thin composite sandwich shells with hexagonal honeycomb, hexagonal-triangular, and star-hexagonal cellular cores of orthotropic materials.