The project is devoted to cooperation of the Slovak partners in the study of microstructure and mechanical properties of fibrous composites with ceramic matrix being developed and manufactured in IRSM by the polymer precursor pyrolysis route. Unidirectional composites reinforced with silicon carbide (Nicalon), oxide (Nextel), or basalt fibers are manufactured using selected polysiloxane resins as matrix precursors. These composites possess favorable mechanical properties at elevated temperatures (in case of Nicalon or Nextel fibers even above 1000°C). In IRSM, mechanical properties of the composites will be measured at laboratory and elevated temperatures. In IMR, microscopic quantitative methods will be employed for microstructure characterization of these materials and fractographic analysis for investigation of their fracture characteristics.