Interfacial micromechanical behavior of C_f/SiC-SiBC composites with varied PyC interphase thickness via fiber push-in method

The interfacial micromechanical behavior of C_f/SiC-SiBC composites with varying PyC interphase thicknesses was investigated using the fiber push-in technique and compared with conventional C_f/SiC. This work establishes a dual-parameter framework for rational interphase design: optimal macroscopic performance requires not only moderate interfacial shear strength (IFSS) but high interfacial reliability (quantified by the Weibull modulus ( m ) of IFSS). A high m ensures a stable load-transfer network, mitigates stress concentrations, and defines the upper bound of toughening potential, while moderate IFSS enables the realization of this potential through effective energy dissipation. Increasing the PyC interphase thickness of C_f/SiC-SiBC reduces the residual stress magnitude and improves the uniformity of residual stress distribution, thereby reducing the IFSS to a moderate level while significantly increasing m . This concurrent optimization of moderate IFSS and high interfacial reliability ultimately yields superior flexural strength and pronounced pseudo-plasticity.