INTERNAL-FRICTION AND GAS DESORPTION OF C C COMPOSITES/

C/C composites are the most promising candidates as high heat flux com ponent materials, where temperature dependence of mechanical propertie s and gas desorption behavior at elevated temperature are important pr operties. At the beginning, the newly developed internal friction meas urement apparatus, which enables the accurate measurement of dynamic e lastic properties up to 1373 K along with the measurement of gas desor ption behavior, was used. The materials studied were unidirectional (U D) C/C composites reinforced with mesophase pitch-based carbon fibers, which were heat treated at temperatures ranging from 1473 to 2773 K w hich produced a variety of graphitized microstructures. Two-dimensiona l (2D) C/C composites reinforced with flat woven fabrics of PAN type c arbon fibers were also studied. These materials were heat treated at 1 873 K. From the temperature spectrum of internal friction of 2D C/C co mposites, three internal friction peaks were detected and were related to gas desorption. Also the temperature dependence of Young's modulus of UD C/C composites, negative and positive dependence of Young's mod ulus were observed reflecting microstructure changes resulting from th e heat treatments.