Two models, E-S and R-S unit cell models, are presented based on the thermal-electrical analogy technique. The analytical expressions for transverse thermal conductivities of unidirectional composites are derived. The dimensionless effective transverse thermal conductivities ke+ are expressed as a function of the ratio (β) of thermal conductivities of filler to matrix, filler volume fraction vf and the geometry ratio ρ=a/b of the filler. The optimization of transverse thermal conductivities of unidirectional composites is then analyzed under different filler volume fractions vf, thermal conductivity ratios β and different geometric architectures. The present analysis allows for a fairly precise evaluation of configuration performance and comparisons of different arrangements. The results show that if a composite is designed for insulation material, we should choose ρ<1, and if a composite is designed for heat dissipating purpose, we should choose ρ>1.

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