Tunable strength of SiCf/β-Yb2Si2O7 interface for different requirements in SiCf/SiC CMC: Inspiration from model composite investigation

Abstract

Model composites consisting of SiC fiber embedded in β-Yb2Si2O7 matrix were processed by Spark Plasma Sintering method and the feasibility of tunable SiCf/Yb2Si2O7 interface in SiC-based CMCs were estimated. Weak and strengthened SiCf/Yb2Si2O7 interfaces were achieved by adjusting sintering temperatures. The indentation crack test and fiber push out experiments clearly demonstrated the different debonding mechanisms in the samples. Weak interfaces sintered at 1200 and 1250 °C exhibited crack deflection at interface in indentation test. Their low debond energy at the interface, which were comparable to those of PyC or BN, satisfied the well-recognized interfacial debond and crack deflection criteria for CMCs. The interface was strengthened by atomic bonding in model composite sintered at 1450 °C, leading to crack penetrating into SiC fiber and high debond energy. The strong interface may be promising in SiCf/SiC CMC to withstand higher combustion temperature, because Yb2Si2O7 will provide plastic deformation capacity, which would serve as weak interphase for crack deflection and energy dissipation. Therefore, it is possible to design the capability of SiCf/RE2Si2O7 interface for different requirements by adjusting interfacial strength or debond energy to reach optimal mechanical fuse mechanism in SiCf/SiC CMC.