INFLUENCE OF RESIDUAL-STRESSES ON THE MECHANICAL-PROPERTIES OF A LAYERED CERAMIC COMPOSITE

A layered Al2O3-ZrO2 ceramic composite has been fabricated using a col loidal processing method. The technique uses sequential centrifuging o f slurries containing suspended ceramic powders to form a three-layere d structure. The outer layers have a high alumina content while the ce ntral layer contains mainly stabilized zirconia. These laminae are sub jected to residual stresses due to their different thermal expansion c oefficients. These stresses depend on rite configuration of rite syste m as well as on the amount of the zirconia in the two layers. If the r esidual 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 mo del for this problem is presented Vickers indentations were also place d into the tensile layer with the intent to explore the clack propagat ion in such system. Cracks were split after they reached the compressi ve layer. The effects of the layer thickness on the depth of the crack s beneath the interface were systematically explored.