Thermal anisotropic properties of composite materials

Composite materials are made of several constituents with different physical properties, and are often anisotropic, although the single materials are not. The effective thermal conductivity and diffusivity of a multilayer composite are evaluated in the two main directions (x and y), theoretically and numerically, as a function of the reinforcement volume fraction. The matrix of the composite is silica and the second component can be asbestos, or steel or copper. The theoretical results are evaluated by the solution of the heat conduction equation, while the numerical analysis is carried out with a second order finite-difference non-iterative steady-state explicit scheme. The comparison between the theoretical and the numerical results is very good. The maximum anisotropy degree is obtained for each composite when the reinforcement volume fraction is 50%. The ratio between the thermal conductivity in the x and y directions is quite high when copper is used and the two layers have the same thickness. The thermal diffusivities in both directions are calculated accordingly.