Comportement en fatigue anisotherme des composites unidirectionnels à matrice titane renforcée par des fibres de carbure de silicium

Abstract : The purpose of this study is to investigate the behavior of the composite SCS-6/Ti6242, a titanium alloy reinforced with continuous SiC fibers, designed for average temperature applications in particular for critical engine aircraft components, under combined thermal and mechanical loads. The thermal-mechanical tests under stress control using a stress ratio of zero and a temperature cycle between 100°C and 450°C, are chosen to simulate the actual loading of the composite part during engine operation. Observations of fracture surfaces under optical and scanning electron microscopy are consistent with a failure controlled by fibre fracture as in monotonous and fatigue matrix cracks. A finite element model is made to estimate the stress in the various components based on the homogeneous equivalent medium and the appropriate constitutive equations for MMC constituents. Complex load redistribution occurs from matrix to fibers under thermal mechanical cycle. These results are used to explain the observed damage mechanisms and the consequences on lifetime predictions in anisothermal fatigue. The long cracks propagation under isothermal and anisothermal conditions was the subject of an experimental study. An analysis of fracture mechanics using a cohesive zone approach has rationalized the observed growth rates.
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Faten Bourbita. Comportement en fatigue anisotherme des composites unidirectionnels à matrice titane renforcée par des fibres de carbure de silicium. Matériaux. École Nationale Supérieure des Mines de Paris, 2011. Français. ⟨NNT : 2011ENMP0098⟩. ⟨pastel-00712981⟩

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