Long-term ceramic matrix composite for aeroengine

Three strategies were proposed to prolong the service life of continuous fiber-reinforced silicon carbide ceramic matrix composite(CMC-SiC),which served as thermal-structure components of aeroengine at thermo-mechanical-oxygenic coupling environment.As for some thermal-structure components with low working stress,improving the degree of densification was crucial to prolong the service life,and the related process approaches were recited.If the thermal-structure components worked under moderate stress,the matrix cracking stress(σ^(mc))should be improved as far as possible.The fiber preform architecture,interface shear strength,residual thermal stress,and matrix strengthening were associated withσ_(mc)in this review.Introducing self-healing components was quite significant with the appearance of matrix microcracks when CMC-SiC worked at more severe environment for hundreds of hours.The damage can be sealed by glass phase originating from the reaction between self-healing components and oxygen.The effective self-healing temperature range of different self-healing components was first summarized and distinguished.The structure,composition,and preparation process of CMC-SiC should be systematically designed and optimized to achieve long duration target.

Rare earth monosilicates as oxidation resistant interphase for SiCf/SiC CMC:Investigation of SiC_(f)/Yb_(2)SiO_(5)model composites

Model composites consisting of SiC fiber and Yb_(2)SiO_(5)were processed by the spark plasma sintering(SPS)method.The mechanical compatibility and chemical stability between Yb_(2)SiO_(5)and SiC fiber were studied to evaluate the potential application of Yb monosilicate as the interphase of silicon carbide fiber reinforced silicon carbide ceramic matrix composite(SiC_(f)/SiC CMC).Two kinds of interfaces,namely mechanical and chemical bonding interfaces,were achieved by adjusting sintering temperature.SiC_(f)/Yb_(2)SiO_(5)interfaces prepared at 1450 and 1500℃exhibit high interface strength and debond energy,which do not satisfy the crack deflection criteria based on He-Hutchison diagram.Raman spectrum analyzation indicates that the thermal expansion mismatch between Yb_(2)SiO_(5)and SiC contributes to high compressive thermal stress at interface,and leads to high interfacial parameters.Amorphous layer at interface in model composite sintered at 1550℃is related to the diffusion promoted by high temperature and DC electric filed during SPS.It is inspired that the interfacial parameters could be adjusted by introducing Yb_(2)Si_(2)O_(7)-Yb_(2)SiO_(5)interphase with controlled composition to optimize the mechanical fuse mechanism in SiC_(f)/SiC CMC.