Experimental and theoretical studies of effective thermal conductivity of composites made of silicone rubber and Al2O3 particles

• Effective thermal conductivities of matrix/particle composites measured.
• Effective conductivity increasing nonlinearly with particle volume fraction.
• Higher effective conductivity for particle of larger mean diameter.
• Existing theoretical models reviewed and evaluated with experimental data.
• Models with interfacial contact parameters fitted very well with experiments.

In this study, effective thermal conductivities of composite materials were investigated both experimentally and theoretically. The composites made of silicone rubber and spherical Al2O3 particles of four mean diameters were prepared with various volume fractions. Experimental results indicate that the effective thermal conductivity increases nonlinearly with increasing particle volume fraction and is higher for larger particles, indicating its dependence not only on conductivities and volume fraction, but also on the materials' interfacial geometry. The experimental results were used to evaluate the performance of theoretical models. It was found that the models by Deissler and Boegli and by Maxwell that contain no parameter for interfacial effects were unable to predict the experimental results. On the other hand, the models by Hsu et al. and by Agari and Uno that provide interfacial contact parameters fit very well with the data over the whole ranges of the present experiment.