Impact of the non-linear character of the compressive stress–strain curves on thermal and mechanical properties of porous microcracked ceramics

Complementary to recent theoretical work, this paper describes implications of the non-linear stress–strain behavior observed in porous microcracked ceramics. Practical aspects of this behavior under uniaxial compression are discussed. In particular, it is shown that the axial moduli of porous microcracked aluminum titanate and cordierite change upon application of a constant or ladder-like time protocol load. The extent of change depends on material microstructural features, such as texture, porosity and microcrack density, as well as on the applied load. In fact, the underlying mechanism is microcrack closure (or even healing), which causes stiffening of the material; at the same time, a uniaxial compressive load can also open new microcracks, or propagate existing ones via microcrack sliding, thus softening the material. The change in the elastic response of the material is accompanied by changes in other properties, such as thermal expansion.