Processing and characterization of a model functionally gradient material

A technique for preparing model Functionally Gradient Materials (FGM) using polyester resin and cenospheres is developed. The cenosphere volume fraction in the polyester matrix is continuously varied through a buoyancy assisted casting process. FGMs having cenosphere volume fraction varying from 0 to 0.45 over a length of 250 mm are prepared. The overall properties of the FGM are varied by adding plasticizer to the polyester matrix. The physical, elastic and fracture properties of the prepared FGMs are evaluated as a function of location to generate the property profiles. The results of the material characterization indicate that, the quasi-static and dynamic modulus of the material increases and the material density decreases in the direction of increasing cenosphere volume fraction. The quasi-static fracture toughness increases up to a certain volume fraction of cenospheres and then decreases. Fractographic analyses of the fractured specimens indicate a change in the fracture mechanism as the cenosphere volume fraction increases. Estimate of the composite modulus using the Halpin-Tsai model with porosity correction matches closely with the test results. (C) 2000 Kluwer Academic Publishers.