EFFECTIVE SPECIFIC HEATS OF SPHERICAL PARTICULATE COMPOSITES WITH INHOMOGENEOUS INTERPHASES

The effective thermoelastic properties of spherical particulate composites with inhomogeneous interphases are studied. Particular emphasis is put on discussing the influence of the radial distribution of the interphase properties on the effective specific heats. Firstly, the inhomogeneous interphase is modeled by multiple concentric layers and the material properties are assumed to be homogeneous in each layer. The composite-sphere model, in which an interphase layer is embedded between the matrix and inclusion, is applied to derive the effective bulk modulus, thermal expansion coefficient (CTE) and specific heats. Secondly, for the case that the interphase properties vary continuously along the radial direction, a set of differential equations are established to determine the effective themoelastic properties of the composites. When the distribution of the Young's modulus of the interphase follows a power law, the analytical expressions of the effective properties are obtained by solving the differential equations. The effective CTE predicted by the present model is in good agreement with the experimental data. It is found that the distribution of both the interphase elastic moduli and the interphase CTE have great effects on the effective specific heats; however, only the distribution of the interphase CTE has significant impacts on the effective CTE.