CREEP BEHAVIOR OF CARBON FIBER COMPOSITES

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High temperature bending and high temperature creep tests of eight layr C/C composites have been investigated and following results have been obtained.(i) C/C composites creep at 1573K.The creep behavior is classified into logarithmic creep.(ii) Slope of displacement-log (time) diagram depends on the applied load and increases as increasing load.(iii) No obvious temperature dependence of yield stress has been observed at 1373-1573K.(iv) C/C composites fracture at lower loads than UTS of fibers.(v) Flow of the matrix strongly affects the yield strength and creep strength of C/C composites.These results strongly suggest that strengthening of the matrix is important to improve long-term high-temperature strength.As conclusions, it is suggested that prediction of long-term deformation characteristics of C/C composite be not possible based on the short-term deformation characteristics. Information of long-term high-temperature deformation characteristics of C/C composites is still lacking and further experimental investigation concerns with effects of deformation conditions are required to improve long-term strength.