Effect of interphase on mechanical properties and microstructures of 3D Cf/SiBCN composites at elevated temperatures

Interphase between the fibers and matrix plays a key role on the properties of fiber reinforced composites. In this work, the effect of interphase on mechanical properties and microstructures of 3D C-f/SiBCN composites at elevated temperatures was investigated. When PyC interphase is used, flexural strength and elastic modulus of the C-f/SiBCN composites decrease seriously at 1600 degrees C (92 +/- 15 MPa, 12 +/- 2 GPa), compared with the properties at room temperature (371 +/- 31 MPa, 31 +/- 2 GPa). While, the flexural strength and elastic modulus of C-f/SiBCN composites with PyC/SiC multilayered interphase at 1600 degrees C are as high as 330 +/- 7 MPa and 30 +/- 2 GPa, respectively, which are 97% and 73% of the values at room temperature (341 +/- 20 MPa, 41 +/- 2 GPa). To clarify the effect mechanism of the interphase on mechanical properties of the C-f/SiBCN composites at elevated temperature, interfacial bonding strength (IFBS) and microstructures of the composites were investigated in detail. It reveals that the PyC/SiC multilayered interphase can retard the SiBCN matrix degradation at elevated temperature, leading to the high strength retention of the composites at 1600 degrees C.