FEM simulations of microstructure effects on thermoelastic properties of sintered ceramics

A model was developed to simulate macroscopic material properties of polycrystalline ceramics from the material properties of the constituting phases and the microstructure. Cubic and random structures were included. The model allows a variation of volume fractions of the phases, grain size and grain boundary areas. Representative for a large number of material properties, elastic tensor, thermal conductivity, coefficient of thermal expansion and thermal stress are calculated for individual microstructures using finite element methods (FEM). Simulations focus on two types of bi-continuous ceramic composites: zirconia toughened alumina (ZTA) and a porous zirconia ceramic which was infiltrated by a spinel-glass. Microstructure of experimental samples is represented by two different model structures: a Voronoi type structure for the ZTA ceramic and a cubic structure of cubes interconnected by cylinders for the infiltrated zirconia system. A substantial impact of microstructure on macroscopic material properties and internal stress distribution is obtained. A good agreement between measured and simulated material properties was found.