A review on functionally graded materials and structures via additive manufacturing: from multi-scale design to versatile functional properties

Functionally graded materials (FGM) and functionally graded structures (FGS) are special types of advanced composites with peculiar features and advantages. This article reviews the design criteria of functionally graded additive manufacturing (FGAM), which is capable of fabricating gradient components with versatile functional properties. Conventional geometrical-based design concepts have limited potential for FGAM and multi-scale design concepts (from geometrical patterning to microstructural design) are needed to develop gradient components with specific graded properties at different locations. FGM and FGS are of great interest to a larger range of industrial sectors and applications including aerospace, automotive, biomedical implants, optoelectronic devices, energy absorbing structures, geological models, and heat exchangers. This review presents an overview of various fabrication ideas and suggestions for future research in terms of design and creation of FGM and FGS, benefiting a wide variety of scientific fields.