Laminar ceramics that exhibit a threshold strength

Thin compressive layers within a Laminar ceramic arrest targe cracks (surfa ce and internal) and produce a threshold strength. This phenomenon increase s the damage tolerance of ceramics and will allow engineers to design relia ble ceramic components for structural applications. The stress intensity fa ctor derived for a crack sandwiched between two compressive Layers suggests that the threshold strength is proportional to the residual compressive st ress and the thickness of the compressive layer and is inversely proportion al to the distance between the compressive layers. Laminates composed of th ick alumina layers (605 +/- 11 micrometers) and thin mullite/alumina compre ssive Layers (37 +/- 1.4 micrometers) fabricated for this study had a thres hold strength of 482 +/- 20 megapascals, in fair agreement with the theory.