C / C Composite Fatigue Performance,

Carbon-carbon composites(C/Cs) are the only low-density materials that can maintain high strength and toughness at high temperatures up to 2273K, with a high thermal shock resistance, a high resistance to wear and good friction properties. So C/Cs have been used in many areas especially in the aerospace field. As the ideal candidate for high temperature structural materials, C/Cs are involved in fatigue loads inevitably. Fatigue behavior is one of the most important design properties for primary load bearing structures intended for long-term use. However, only a few studies on the fatigue behavior of C/Cs have been reported and the governing mechanisms of the fatigue behavior have not been successfully described. So the study on the fatigue behavior of C/Cs is significant and meaningful.Three-point bending test and static tensile test were conducted for C/Cs, their failure modes were investigated by analyzing their broken sections with SEM observation and stress-strain curves.The tensile fatigue behavior of a cross-ply carbon-carbon laminate was examined at room temperature. Tension-tension cyclic fatigue tests were conducted under load control at a sinusoidal frequency of 10 Hz to obtain stress-cycles relationship. The fatigue limit was found to be 160 Mpa (91.7% of the tensile strength), and no fracture was found at over 10~4 cycles. The residual tensile strengh of specimens that survived fatigue loading was enhangced, and the inner fibers of material were not damaged almostly with small stress loading. The "interface control" played an important role in the fatigue loading. The shape of S-N curve of C/C composites displayed three segments and the damaged form of material by fatigue loading was different in different segment. The formula was given to described the S-N curve of cross-ply carbon-carbon laminate, and it can forecast the fatigue limit of C/Cs commendably.The methods of FEM with nastran was used to analysis the mechanical property of cross-ply carbon-carbon laminate and its tensile fatigue property was analysed in MSCFatigue.