5 – Functionally-graded ceramic composites

Publisher Summary Layered-Graded Materials (LGMs) exhibit a stepwise or progressive change in composition, structure, and properties as a function of position within the material. This innovative design eliminates ever-present sharp boundaries in conventional composites that may impart undesirable physical and mechanical properties. The concept and synthesis of layered and graded materials from the infiltration technique have been introduced. The mechanical and fracture properties of various alumina-based LGMs have been discussed in this chapter in relation to phase composition, microstructure, and residual stress. These materials displayed superior mechanical performance in terms of strength, fracture, and thermal shock resistance. This new approach may be further developed for designing new generation layer composites with an in-situ top wear resistant coating and a flaw-tolerant graded substrate or bulk. A new philosophy and design process for tailoring layer graded composites for both strength and damage tolerance has been highlighted for alumina-based ceramics. This approach allows the design of multifunctional new generation layer composites with a top hard layer for wear resistance and a graded bulk or underlayer for damage tolerance.