Résumé
Several industrial carbon fillers have been carried out to test their potential to improve the thermal conductivity of epoxy composite materials while maintaining their low electrical conductivity. Large samples (50 × 50 × 4 mm) were prepared, using an industrial high insulating anhydride cured-DGEBA epoxy resin of high viscosity (~8.5-15 Pa.s) and heavy molecular weight (385 g mol$^{-1}$). The best results are obtained from graphite nanoplatelets GnP M: the relative increase in thermal conductivity ($κ$comp) reaches 100% (0.37 Wml$^{-1}$ K$^{-1}$) at load of 1.13 vol% while maintaining the electrical resistivity above 10$^5$ m. These results are interpreted in terms of transport of acoustic phonons in a two-phase system composite. It is shown that the graphite-epoxy composite thermal conductivities can be discussed as a function on the graphite volume fraction, the graphite filler thickness (L$_c$), their aspect ratio and thermal boundary resistance (R$_{int}$). R$_{int}$ is expressed as a function of $κ$comp, $κ_f$ (filler intrinsic thermal conductivity) , filler aspect ratio, and two constant values, one depending on the chemical bonding strength at the interface between the graphite particles and the matrix and the other depending on the filler dispersion homogeneity inside the matrix at the macroscopic scale.