Prediction of the mechanical behaviour of porous ceramics using mesomechanical modelling

In this contribution, a mesomechanical modelling of porous polycrystalline ceramics subjected to different kinds of loading is presented. Experiments show different response of the ceramic materials under tension and compression. It is assumed that porosity of the material is distributed homogeneously inside the grains and along the grain boundaries. In the paper, two different crack initiation mechanisms––on account of stress concentration at the pore boundary––is proposed and analysed for tension and compression. In the polycrystalline ceramic material cracks grow mainly inter-granularly due to less value of the fracture surface energy of the grain boundary in comparison to the fracture surface energy of the grains. In theoretical modelling of the material behaviour mesomechanical approach is introduced. Hence the average procedure over the representative surface element containing initial porosity and a set of growing cracks is applied. The proposed description of two different mechanisms of crack nucleation and propagation results in formulation of constitutive relations in order to specify differences in the material behaviour under tension and compression. This paper is an extension of the results obtained by authors for monolithic ceramics without initial porosity [Mech. Mater. 18 (1994) 1; Int. J. Damage Mech. 3 (1994) 212; Int. J. Damage Mech. 4 (1995) 293].