Influence of the Definition of the Representative Volume Element on Effective Thermoelastic Properties of Thermal Barrier Coatings with Random Microstructure

Coatings produced by air plasma spraying (APS) are characterized by a lamellar structure with high porosity, numerous microcracks and present a random microstructure. The process parameters influence not only the porosity but also the form of the microstructure defects. Different methods have been developed and used to investigate the influence of such random microstructures on the effective mechanical properties. Homogenization methods, based on asymptotic expansion of the involved fields, assume the periodicity of the microstructure. For materials with periodic microstructure they predict accurately and cost efficiently their effective properties. But, for non-periodic microstructures like APS thermal barrier coatings (TBC), the geometrical definition of the so-called representative volume element (RVE) plays a crucial role. In fact, these microstructures are approximated by periodic ones, whose characteristics (extension and phase distribution) are obtained by statistical methods. In this work, several approaches were applied to investigate the influence of the RVE position and geometry on the resulting effective properties of the TBC.