Assessment of the interfacial properties from fatigue hysteresis loss energy in ceramic-matrix composites with different fiber preforms at room and elevated temperatures.

The fiber/matrix interface shear stress is a key parameter in the fatigue behavior of fiber-reinforced ceramic-matrix composites (CMCs). In this paper, the interface shear stress of three CMCs with different carbon fiber preforms, i.e., unidirectional C/SiC, cross-ply C/SiC and 2.5D woven C/SiC, has been estimated from fatigue hysteresis loss energy at room and elevated temperatures. Under fatigue loading, the fatigue hysteresis loss energy and fatigue hysteresis modulus versus the applied cycles have been analyzed. The theoretical relationships between the fatigue hysteresis loops, the fatigue hysteresis loss energy, the interface slip and the interface shear stress have been established. When the interface shear stress degrades, the fatigue hysteresis loss energy first increases to the maximum value, then decreases to zero; the fatigue hysteresis loops correspond to different interface slip cases. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the evolution of the interface shear stress versus the applied cycles of C/SiC composites has been analyzed. The effects of fiber preforms and test conditions on the interface shear stress degradation have been investigated. The fatigue hysteresis loops of unidirectional, cross-ply and 2.5D woven C/SiC composites have been predicted for different applied cycles at room and elevated temperatures. [ABSTRACT FROM AUTHOR]