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Cyclic Fatigue Behaviour at Room Temperature and at High Temperature under Inert Atmosphere of a C/SiC Multilayer Composite
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机译：Cyclic Fatigue Behaviour at Room Temperature and at High Temperature under Inert Atmosphere of a C/SiC Multilayer Composite
Cyclic fatigue at room temperature and at high temperature hasbeen investigated on a 2.5D C/SiC multilayer CMC, at the samemaxinium stress level but at various temperatures from roomtemperature to 1500 deg C under inert atmosphere. During cyclicfatigue the mechanical behaviour, exhibited by stress/strain loops,evolves with the number of cycles applied. This evolution can bequantified by 3 parameters the mean elastic modulus, the mechanicalhysteresis, the residual strain. The microstructural damagesassociated have also been observed. From these analyses it has beenpointed out that the matrix exhibit a multiple crack at variousscales in the tows and between the tows, and that the tows aretotally debonded from their surrounding matrix shell. Therefore, asshown by observations of microstructures and by the evolutions of themechanical hysteresis during cyclic fatigue tests, the origin of thecyclic fatigue in this composite can be attributed to a progressivewear of the tow/surrounding matrix interfaces instead of thefibre/matrix interfaces. At high temperatures lower than 1000 deg. C.this compositc exhibits also an original increase of the mean elasticmodulus, associated to a wide increase of the residual strain. Thisphenomenon is not specific to this CMC, but has been observed onother CMC like 0, +60, -60., C/C, 0,9_12 SiC/MAS-L, orheat-treated 2D SiC/SiC. This non classical stiffening can beexplained by a bad closure of cracks in the transversal yarns.
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