A review of production techniques, classifications, material gradation rules, and industrial applications of functionally graded materials

Functionally graded materials (FGMs) are advanced composite materials, which greatly improve over fibrous composite materials often subjected to delamination type of failure. The material properties of FGMs vary gradually in single or multiple directions. FGM consists of two or more materials whose combination enables the achievement of specified properties by the desired applications. The article focused on a review of various manufacturing/fabrication methods of FGMs, material gradation rules of FGMs and various industrial applications of FGMs. The literature on the classification of FGMs according to types of gradients, sizes or scales, state of matter, etc. is reviewed and discussed. Along with this, the literature on fabrication methods such as gas-based, liquid-based and solid-based is also reviewed and discussed. Finally, the literature on various industrial applications of the FGMs is reviewed and discussed.