Ceramic-matrix composites (CMCs) are a new type of thermal-structural-functional integrated materials with the advantages of metal materials, ceramic materials and carbon materials. They have the characteristics of material-structural integration. Through the optimization design of each structural unit, synergistic effects can be produced, and high performance and reasonable matching of each performance can be achieved. Therefore, CMCs have high temperature resistance, corrosion resistance, wear resistance, low density, high specific strength, high specific modulus, low thermal expansion coefficient, insensitivity to cracks, no catastrophic damage and other advantages. Compared to metallic alloys, CMCs can have a density reduction of 30-50% and can exceed the working temperature range. With the increase of thrust-weight ratio and turbine inlet temperature, CMCs have become one of the preferred high-temperature structural materials for aero engine. When CMCs are used in hot-section component in aeroengine, i.e., turbine, combustion chamber, combustion liner, and nozzles, the amount of cooling air can be significantly reduced or even zero, the combustion efficiency can be improved, the pollution emission and noise level can be reduced. At elevated temperature, the mechanical behavior of CMCs is much different than that at room temperature. Under cyclic fatigue loading, the interface wear mechanism decreases the fiber/matrix interface shear stress, which affects the fatigue damage and lifetime of CMCs. In this paper, the temperature-dependent fatigue damage evolution of fiber-reinforced CMCs is investigated. The fatigue loading/unloading constitutive model considering the effect of temperature is developed based on the damage mechanisms of the matrix cracking, interface debonding and repeated sliding between the fiber and the matrix. The shear-lag model is used to obtain the micro stress field of the damaged CMCs with matrix cracking and fiber/matrix interface debonding. The stochastic matrix cracking model is used to determine the matrix crack spacing. The fracture mechanics approach is used to determine the fiber/matrix interface debonding length, interface counter-slip length and the new slip length. The relationships between the fatigue loading/unloading hysteresis loops, temperature, applied cycle number, and fiber/matrix interface debonding and sliding are established. The evolution of the fatigue loading/unloading hysteresis loops, interface debonding and sliding length with applied cycle number is analyzed. The effects of the temperature, peak stress level, applied cycle number, interface shear stress, and interface debonding energy on the fatigue loading/unloading damage evolution are discussed based on the developed temperature-dependent fatigue loading/unloading constitutive model. The experimental fatigue damage evolution of SiC/SiC composite at different elevated temperatures is predicted using the present analysis.


Temperature-Dependent Fatigue Damage Evolution of Fiber-Reinforced Ceramic-Matrix Composites

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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