Description Functionally graded materials (FGMs) were developed in 1984 for a space plane project to sustain high thermal barriers to overcome the shortcomings of traditional composite materials.1 Traditional composites (fig. 1A) are homogeneous mixtures, therefore involving a compromise between the desirable properties of the component materials. FGMs are a class of advanced materials with spatially varying composition over a changing dimension, with corresponding changes in material properties built in.2 FGMs attain their multifunctional status by mapping performance requirements to strategies of material structuring and allocation (fig. 1B).