CMSE2015

Analytical and numerical modeling of effective elastic and thermal properties of porous materials with convex, concave or anisometric pore shape
Dr. Willi Pabst
Department of Glass and Ceramics University of Chemistry and Technology, Prague (UCT Prague), Czech Republic
The effective elastic and thermal properties of porous ceramics, including highly porous cellular ceramics (ceramic foams) are strongly dependent on the porosity, but also on other details of the microstructure. In this contribution it is shown that pore shape has a far greater influence on the effective Young’s modulus and thermal conductivity than the pore connectivity (closed or open), pore distance (cell wall thickness) and pore size distribution (monodisperse, bidisperse, uniform). It is shown that anisometric pore shape can be analytically modeled via the spheroidal model and that the analytical predictions are well confirmed by numerical results. Further it is shown that closed (isolated) pores or cells always result in a slightly higher Young’s modulus and thermal conductivity than open (overlapping) pores. While porous model materials with convex isometric pores exhibit effective properties that are systematically higher than our exponential prediction and in most cases closer to the power-law prediction (Gibson-Ashby relation for open-cell foams), those with concave pores between convex particles are often below our exponential prediction, especially in the case of dense periodic arrangements of particles. Finally it is shown that, although a universal parameter-free prediction by analytical models does not exist, our cross-property relation between Young’s modulus and thermal conductivity allows a very precise prediction of the Young’s modulus when the thermal conductivity is known and vice versa.