Evaluation of the thermophysical properties of functionally gradient materials

Three kinds of geometrical models are presented for functionally gradient materials (FGMs), and thermophysical properties of the models are evaluated in a numerical simulation. The idea of these models is based on that of a random model for dispersed materials. First, the thermal conductivity is evaluated for the models for a steady conduction condition, and the result is used to obtain an 'indirectly' evaluated thermal diffusivity with knowledge of the specific heat capacity and mass density of FGMs. Second, a diffusivity measurement process with a pulse-heating method is simulated to obtain a 'directly' evaluated diffusivity. Indirectly and directly evaluated diffusivity values are compared. Influences of temperature distribution in the models, component material configuration, and number of sublayers in an FGM layer are investigated. It is concluded that the thermal diffusivity should be measured directly.