The paper presents a new approach in the field of metal–matrix composite characterisation where an electrical conductivity measurement was used to calculate the electron part of composite thermal conductivity by using the Wiedemann–Franz law. The electrical and thermal conductivities of the composite were characterised and their relationship was analysed. Results showed that in comparison with simple analytical models, this method can also be used for predicting the thermal conductivity of the copper matrix–continuous carbon fibre composite in a transverse direction. The unidirectional composite was produced by diffusion bonding and contained 40–60 vol.% of unidirectional fibres. Experiments were performed in directions parallel and normal to the fibre orientation and showed that with an increasing ratio of fibre volume, both thermal and electrical conductivities decreased from 221.6 W/m·K to 38.7 W/m·K and from 35.8 MS/m to 5.3 MS/m, respectively.

The work describes the dependence of the electrical conductivity of carbon materials infiltrated with copper in a vacuumpressure autoclave on copper concentration and on the effective pore radius of the carbon skeleton. In comparison with noninfiltrated material the electrical conductivity of copper infiltrated composite increased almost 500 times. If the composite contained less than 7.2 vol% of Cu, a linear dependence of the electrical conductivity upon cupper content was observed. If infiltrated carbon contained more than 7.2 vol% of Cu, the dependence was nonlinear -the curve could be described by a power formula (x − xc) t . This is a typical formula describing the electron percolation process in regions containing higher Cu fraction than the critical one. The maximum measured electrical conductivity was 396 × 10 4 Ω −1 m −1 for copper concentration 27.6 vol%. Experiments and analysis of the electrical conductivity showed that electron percolation occurred in carbon materials infiltrated by copper when the copper volume exceeded the critical concentration. The analysis also showed a sharp increase of electrical conductivity in composites with copper concentration higher than the threshold, where the effective radius of carbon skeleton pores decreased to 350 nanometres.

Interpenetrating phase composites carbon-tin prepared by the pressure infiltration technology were tested in terms of electrical conductivity, thermal conductivity and sound velocity relating to the tin content (up to 25 vol.%. Sn). Results obtained show that at tin concentration xc = 7.9 vol.% the continuous cluster of the tin component in the carbon skeleton is formed. As a result, the percolation of electrons in composites occurred changing the concentration dependence of electrical conductivity from linear to power. Thermal conductivity and sound velocity of composites increased linearly with increase in tin content without being influenced by the tin cluster structure.K e y w o r d s :