Fatigue behavior of alumina-zirconia multilayered ceramics

The influence of sustained and cyclic loading on the crack growth behavior of a multilayered alumina-zirconia composite exhibiting high internal compressive stresses is investigated. The study was conducted on precracked notched samples and focused on evaluating the static and cyclic fatigue resistance to crack extension beyond the first arresting interface (threshold) as well as the mechanisms involved during stable crack growth through the layered structure for each loading condition studied. Although it is found that the layered composite is prone to subcritical crack growth, the effectiveness of operative toughening mechanisms, i.e., compressive residual stresses as well as crack bifurcation and delamination at interfaces, is observed to be independent of the loading conditions. As a consequence, fatigue degradation of the multilayered ceramics studied is restricted to the intrinsic environmental-assisted cracking of the individual layers, pointing them out as toughened composites practically immune to variable stresses and much less static and cyclic fatigue sensitive than other structural ceramics.