Threshold strength evaluation on an Al2O3–ZrO2 multilayered system

The fracture behaviour of an alumina–zirconia multilayered ceramic obtained by slip casting has been evaluated and compared to monolithic alumina taken as a reference. It is found that the laminated system exhibits an apparent fracture toughness Kapt,c, calculated experimentally (SEPB) and analytically with a weight function approach, higher than twice the value determined for the monolithic material. Additionally, the experimental rupture tests accomplished indicate the existence of a threshold strength in the multilayer. The increase in Kapt,c in the laminate, associated with a pronounced R-curve behaviour, is discussed in terms of the high compressive stresses in the internal layers and their effect on the effective driving force for crack extension.