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A numerical design approach for ceramic multilayer laminates with predetermined stress profiles is here pro- posed and compared with a well established theoretical method. The design procedure allows for the optimization of layer composition, in order to obtain high reliability and at the same time control composition and stress state of each layer. The proposed approach is used to design alumina-mullite-zirconia laminates with high toughness, meeting at the same time the particular functional requirements of a pure alumina surface layer with residual compressive stresses with the aim to increase tribological properties. The main limitation to the use of ceramic materials in structural applications is owed to their low reliability, i.e. their high scatter in failure strength and low fracture tough- ness. This behavior is directly related to the presence of flaws originated during the production processes and the service. Although improvements in material quality, manu- facturing methods and component design have resulted in a drastic reduction of structure failures, the low fracture toughness of ceramics, coupled with their susceptibility to failure by slow crack growth under stresses well below their fracture strength, remains a concern for the reliability of ce- ramic bearings in many engineering applications (1). Many efforts have been made with the purpose to in- crease the reliability of ceramic materials: a promising ap- proach is the design and manufacturing of multilayered structures with a tailored residual stress field. Layers of ce- ramic composites with different composition are stacked, obtaining a graded ceramic, with the purpose to develop a specific residual stress profile as a result of the sintering process. The thermal stresses are due to the mismatch of the mean coefficient of thermal expansion between the layers and between the different grains in the same layer (2, 3). It was shown that in ceramic multilayer laminates with alumina surface layer, a compressive residual stress at the surface has beneficial effects on the wear and friction behav- ior, as a consequence of the reduction of crack nucleation and propagation and the formation of thinner and smoother tribolayers (4). Similarly, a compressive layer placed at a certain depth can significantly increase the toughness of the material (5).

A Computational Approach to Design High Reliability Ceramic Laminates