The delamination of ceramic laminates due to residual thermal stresses

Laminates comprised of zirconia layers separated by thin porous alumina interlayers have been observed to fail by delamination during the sintering process. The delamination has been shown to be caused by the build up of elastic residual stresses on cooling from the sintering temperature to room temperature. These stresses have been measured and give good agreement with those expected assuming that no stress relaxation occurs. Having established the magnitude of the stresses the crack driving force for delamination can then be reliably predicted, This is in good agreement with the observed failure of the laminates, either by spontaneous delamination during cooling or by mechanical testing of those laminates surviving the sintering process intact. The implications for laminate design in terms of number and thickness of the layers and the material properties of the layers are discussed.