The thermal conductivity of epoxy-resin/metal-powder composite materials from 1.7 to 300K

Abstract

The thermal conductivity of composites made from epoxy-resin Epikote 828 with metal-powder fillers has been measured from 1.7 to 300K. The metals were Cu, Ag, Au, Al, Sn, Pb, stainless steel and bronze, and in almost all cases the particles were spherical or rounded. At 20K and above the thermal conductivity is independent of the particle size and is in good agreement with the relation of Meredith and Tobias (1960) (extension of Rayleigh's theory). Below 20K the thermal conductivity of the composite is lower than predicted by the theory especially for specimens containing smaller particles, and it can even be less than that of the unfilled resin. This is due to an acoustic mismatch of the phonons at the resin-particle interfaces. An effective particle conductivity which takes account of this mismatch can be computed, which when incorporated into the theory leads to reasonable agreement with experiment.