Development of damage state in porous ceramics under compression

This article describes a double-scale approach to modelling of damage growth in the porous polycrystalline ceramics under compression. A theoretical way of determination of the compliance tensor components for porous ceramics and their experimental verification was proposed. The mesomechanical approach, described in details in [T. Sadowski, S. Samborski, Comput. Mater. Sci. 28 (2003) 512–517], gives an insight into physical phenomena taking place in the material structure under loading. The phenomenological model contains an analysis of compliance changes in macroscale, due to defects growth. A decomposition of the fourth-order compliance tensor Sijkl was assumed. The partial tensors stand for: elastic matrix compliance, pore influence and crack influence on material behaviour. A loading history called loading–unloading–reloading Procedure (LURP) was applied during experimental testing. A second-order damage tensor Dij in phenomenological model describes damage history and anisotropy. Its components were estimated by an analysis of the current material deformation state and Young’s moduli changes. Results of experiments for two polycrystalline porous ceramics (magnesia and alumina) were compared with the numerical results given by mesomechanical model, which is based on an analysis of the Representative Surface Element (RSE) and needs some additional data to describe polycrystalline structure. They were obtained by Scanning Electron Microscopy (SEM). Numerical results demonstrated that the proposed method is a good approximation of the real ceramics behaviour.