Research On The Strength Of Ceramic/Metal Functionally Graded Materials

Research on the strength of Ceramic/Metal Functionally Graded Materials (C/M FGM) under the thermal shock loads is one of the key techniques for the future application in the fields of aerospace, astronautics, atomic energy and national defense equipments. The development of the Failure Mechanics, which is based on the features of the meso-/micro-structure of FGM and integrated with the damage/fracture mechanics, material science and physics, is important for the research and application of FGM. The failure mechanics will offer an effective theoretical tool for the material design, optimization and failure analysis.In this paper, the continuum mechanics theory for the FGM is studied and the failure mechanism of FGM with interior defect is analyzed. A statistic model for the damage and fracture behavior is constructed. The primary works of this paper are summarized as follow:1. The micro failure mechanism of C/M FGM under the thermal shock loads is analyzed. The failure of the materials is determined by the interior defect. Under the thermal shock loads, the micro cracks are forming and propagating, until the macro cracks formed inside the FGM. From experimental observation, the damage and fracture of C/M FGM under the thermal shock loads is brittle failure.2. Considered the heterogeneous features of the C/M FGM and the characteristic of the thermal shock, a theoretical model for the thermal shock problem of FGM is developed followed the basic scheme of the continuum mechanics.3. Followed the discussions on the micro mechanism of the crack growth, the macro fracture parameters are obtained by applying the statistic theory. The parameter can reflect the micro-/meso-structure characteristics of C/M FGM. Then a new damage/fracture model is established for the strength analysis of the C/M FGM. The theoretical model is a unity of micro-, meso- and macro-scale analysis.4. The finite element method for the strength problem of C/M FGM underthe thermal shock loads is established. As a numerical example, the PSZ/Ni FGM system is analyzed. The mechanical responses of the FGM under thermal loads are obtained.