On microstructural mechanisms causing non-linear stress-strain behavior of porous ceramics under tension

Possible micromechanisms that explain experimental data on stress-strain behavior of porous ceramics (such as cordierite) under tensile cyclic loading are discussed. The data show that, in the first cycle, the stress-strain curve exhibits non-linear behavior, with sharply higher incremental stiffness at the beginning of unloading and noticeable hysteresis. In subsequent cycles, the curves are almost perfectly linear. Whereas the underlying micromechanisms of such behavior are presently not fully clear, we suggest possible mechanisms that involve frictional sliding on microcracks. Such sliding may take place under tensile loads provided the cracks have complex non-flat geometries (such as zigzag ones).