Mechanical properties of porous ceramics in compression: On the transition between elastic, brittle, and cellular behavior

This paper deals with the uniaxial compression behavior of porous ceramics within a wide range of porosity, varying from 30 to 75 vol%. The load-displacement curves recorded on porous alumina samples showed a transition between a typical brittle behavior at porosity fractions below 60 vol% and a damageable, cellular-like behavior, at higher porosity fractions. This transition in fracture mode was confirmed by in situ compression tests in an X-ray tomograph. Based on a simple model taking into account the competition between the crack length initiating from spherical pores and the mean distance between pores, the porosity at which the transition took place was estimated. The influence of the pore size also depended on the volume fraction of pores: no size effect was noted at the lowest porosity whereas a statistical effect on the size of the solid walls was observed at higher porosity, with an increase in fracture strength with small pores