Evaluation of static strength properties of porous ceramics with various pore morphology

Abstract

In this work, static strength properties of porous alumina and zirconia were investigated to clarify porosity effects on strength. Three-point bending tests and hardness tests were conducted by using porous alumina and zirconia as well as dense ones. Respective porous ceramics had three different porosities. It was revealed that both the bending strength and the hardness decreased drastically as increasing porosity. Through a laser scanning microscope, cross sections were observed to characterize spatial and size distributions of pores on their surfaces. Fracture surfaces were also observed by a scanning electron microscope to clarify fracture morphology depending on porosity. In this study, based on the observed pore characteristics, a fracture mechanics procedure was proposed by presuming pores to be surrounded by virtual cracks with specific length. Monte Carlo simulations based on the proposed procedure were carried out by assuming the same properties of virtual-crack distribution as those of pore distribution observed in each material. Strength simulated by using the proposed procedure in every material almost coincided with experimentally observed ones. Consequently, the proposed procedure was confirmed to be efficient in evaluating effects of bulk porosity and pore-distributions on strength of porous ceramics with different pore morphology.