Influence of residual stresses on the mechanical properties of a layered ceramic composite

A layered Al2O3-ZrO2 ceramic composite has been fabricated using a colloidal processing method. The technique uses sequential centrifuging of slurries containing suspended ceramic powders to form a three-layered structure. The outer layers have a high alumina content while the central layer contains mainly stabilized zirconia. These laminae are subjected to residual stresses due to their different thermal expansion coefficients. These stresses depend on rite configuration of rite system as well as on the amount of the zirconia in the two layers. If the residual stresses exceed the strength of the inner layer, periodic par allel cracks ale produced. Such cracks of course adversely, influence the structural performance of the composite ann should be avoided A model for this problem is presented Vickers indentations were also placed into the tensile layer with the intent to explore the clack propagation in such system. Cracks were split after they reached the compressive layer. The effects of the layer thickness on the depth of the cracks beneath the interface were systematically explored.