The goal of our research is to develop a carbon-carbon-silicon carbide composite that will unite high fracture toughness of carbon-carbon composite with good oxidation and abrasion resistance and good thermal conductivity of silicon carbide. That can be achieved by the preparation of functionally graded C/C-SiC composites. For the production of C/C-SiC composites with a gradient structure of the ceramic matrix – from a carbon matrix in the core to a SiC matrix on the surface new materials based on C/C composite with SiC nano-particles dispersed in the matrix were produced. Since for the thermo-mechanical properties of such materials, the interface between the carbon fibres and the matrix phase is crucial, we studied the influence of SiC precipitation from the matrix phase on the interface structure and the mechanical properties of C/C-SiC composites. The results show that SiC nano-particels are precipitating around the carbon fibres influencing the interface structure and consequently also the mechanical properties.