Experiment and modeling on the compressive behaviors for porous silicon nitride ceramics

Two types of porous Si₃N₄ ceramics with different porosity are fabricated by gel casting technique, where the high pure Al₂O₃ and Y₂O₃ are selected as sintering additive. The effective Young's modulus and compression strength are tested by compressive experiments, respectively. The present emphasis is placed on the mechanical characterization of porous Si₃N₄ ceramics by employing finite element (FE) method. Extracting the primary features of bonded networks, the microstructure of real material is reconstructed in the numerical model. For the obtained materials with different porosity, their compressive behaviors are modeled by FE simulation, respectively. Afterwards, the effective Young's modulus and compression strength are calculated from the numerical results. Compared with experiment data, the calculated results provide a sufficient accordance. Moreover, the modeled failure mechanism in microstructure is also verified by experimental observation. Utilizing the present FE model, the influences of grain aspect ratio and properties of grain boundaries on the effective Young's modulus and compression strength are also investigated, which provides an insight into the relationship between microstructure and macro-mechanical properties for porous Si₃N₄ ceramics.