Effect of Kapitza contact and consideration of tube-end transport on the effective conductivity in nanotube-based composites

Recent studies reported that the theoretical predictions of the effective thermal conductivity of nanotube-based composites by conventional micromechanical models are anomalously higher than those measured experimentally and suggested that the contact resistance on the interface could be the contributing factor to the lower measured value. We explore theoretically whether the large disagreement could be attributed to the effect of Kapitza contact resistance. Our simulations show that the thermal contact resistance on the lateral surfaces of the nanotubes could not be a major factor of this marked disparity. By contrast, the heat transport mechanisms at the ends of the nanotubes could be a significant factor to influence the value. We propose a few simple models to simulate the thermal conductivity at the ends of the nanotubes, similar to two springs in serial and/or in parallel. Under the propositions, we find that the experimental data can be better predicted than the conventional theory and that the tube-end transport is, in general, poor.