A constitutive model of metal-ceramic functionally graded material behaviour: formulation and parameter identification

The mechanical performances of industrial components such as wear coatings and thermal barriers can be greatly enhanced by employing ad-hoc designed metal–ceramic functionally graded materials (FGMs). The continuously varying mechanical properties of FGMs can be related to the spatial distribution of their components by a modified rule of mixture, named TTO model, extended to J2 flow theory with isotropic hardening in order to describe the elastic–plastic behavior of metal–ceramic FGMs. An alternative elastic– plastic model is considered here, accounting for a volume-fraction-governed transition from Hencky–Huber–Mises (J2 flow) model, typical of the purely metallic phase, toward a Drucker–Prager constitutive law more suitable to describe the mechanical behavior of ceramics. Potentialities and limitations of a recently proposed inverse analysis procedure, based on indentation tests, for the identification of constitutive parameters involved in this material model are investigated.