A constitutive model of metal-ceramic functionally graded material behavior: 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.