High reliability ceramic laminates by design

A design and processing approach has been identified and reduce to practice to obtain ceramic materials with high mechanical reliability, i.e. high failure resistance, limited strength scatter and increased damage tolerance. Different ceramic layers are stacked together to develop a specific residual stress profile after sintering. By changing the composition and the stacking order of the laminae it is possible to produce a material with predefined failure stress as it can be evaluated from the fracture toughness curve associated to the residual stresses. In addition, by tailoring the fracture toughness curve, surface defects can be forced to grow in a stable way before reaching the critical condition, thus obtaining an unique-value strength. In this way, reliable ceramic materials could be safely used in many structural applications. Laminates composed of alumina/zirconia layers designed and fabricated in this work through the proposed approach showed a "constant" strength of ≈ 600 MPa (standard deviation < 10%) even when large surface damages were produced, in very good agreement with the design value.