A new special coating/fiber element for analyzing effect of interface on thermal conductivity of composites

The effects of interface or interphase on micro- and macro-thermal behaviors of square-pattern unidirectional fiber-reinforced composites are investigated. The interfacial phase is modeled by a thin layer coated on the surface of the fiber to resist radial and circumferential thermal expansion of the fiber. Making use of the periodicity of the composite, a basic unit cell containing one fiber is used to analyze numerically the states of temperature by way of a novel special coating/fiber element model developed in this paper. The element is established by employing special fundamental solutions which exactly satisfy the governing equations of heat transfer and the interfacial continuity between the filler and the interfacial phase in the unit cell. Subsequently, the mesh reduction effect, convergence, and accuracy of the present special coating/fiber element are verified by comparison with those from conventional finite element methods. Then, the effective thermal conductivity of several composites is analyzed for various values of the interfacial parameters including thickness and thermal properties under different fiber volume fractions to numerically reveal the role of the interface.