Functionally-graded materials mechanical properties

Keywords functionally graded material, mechanical property, microstructure zirconia, nickel... 

The concept of functionally graded materials (FGMs) is to tailor nonuniform distribution of components and phases in materials, and hence combine mechanical, thermal, electrical, chemical, and other properties that cannot be realized in uniform materials. For example, the material structure may have a smooth transition from a metal phase with good mechanical strength on one side, to a ceramic phase with high thermal resistance on the other side (see Fig. 13). With a gradual variation in composition, FGMs do not have the intermaterial boundaries found in multilayer materials, and hence they exhibit better resistance to thermal stress. 

Functionally graded materials (FGMs) distribute the material functions throughout the material body to achieve the maximum heat resistance and mechanical properties ideal for spacecraft where one side may be exposed to extremely high temperatures and the other side may be exposed to extremely low temperatures. Because FGMs characteristically have continuously varying material properties, many analytical methods developed for conventional composites with distinct phases may not be directly applicable to FGMs. 

KEYWORDS functionally graded material, centrifugal cast, microstructure, mechanical property, TiC, Al alloy... 

Based on the measured thermomechanical properties and the microstructure of the graded layer of TiC-NiaAl functionally graded material, using the analysis method, the interface residual thermal stress of TiC-NiyAl sphere in the sintering process was calculated. The relationship between the stress and the content of NiyAl was presented. The results show that the failure mechanics of TiC-NijAl composite may be different in different content of NiyAl. 

As part of the Japanese National Project on Functionally Graded Materials (FGMs), we have been studying design methodology for the application to be used in future space programs. The purpose of this study is to control the compositional and microstructiu-al distribution in the materials so as to minimize thermal stresses imposed on the materials. This study can be understood as the tailoring of mechanical properties of materials. 

N. Noda and T. Tsuji, Steady Thermal Stresses in a Plate of Functionally Graded Material with Temperature-Dependent Properties, Transactions of the Japan Society of Mechanical Engineers, Vol. 57A(535), 625-631, 1991. 

The use of Engineering Ceramics, introduces entirely new fields to be considered. These include mechanical properties, decorative ceramics, environmental uses, energy applications, bioceramics, composites, functionally graded materials, intelligent ceramics and so on. 

An epoxy infiltration process has been used to fabricate zirconium phosphate with much improved physical and mechanical properties for robust applications in various electrochemical devices. Results show that phase composition, microstructure and properties vary gradually along the depth profile, confirming the functionally-graded character of these materials. 

Functionally-graded ZrP materials with improved physical and mechanical properties of ZrP have been produced by epoxy infiltration. These materials show classical functionlly-graded characteristics with continuous change in composition, physical and mechanical properties. 

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