Interfacial Mechanical Properties of the Domestic 3rd Generation 2.5D SiCf/SiC Composite

Continuous silicon carbide fiber reinforced silicon carbide composite (SiCf/SiC) is a critical structural material for the development of next-generation aircraft engines. The interfacial property is one of the important factors determining the material mechanical properties. Therefore, this study characterized the interfacial mechanical properties of domestic third-generation 2.5D SiCf/SiC and investigated its relationship with tensile properties. The residual stress of the 2.5D SiCf/SiC constituents and interfacial sliding stress (IFSS) were quantitatively analyzed by hysteresis characteristics during the cyclic tension loading/unloading test. Statistical distributions of the in-situ fiber strength (sigma(fu)) were obtained based on the fracture mirror radius of pull-out fibers. Interfacial shear strength (ISS) and interfacial debonding energy (G(i)) were obtained through the push-in method. Results show that combination of macroscopic and microscopic methods can comprehensively describe the interfacial mechanical performance of 2.5D SiCf/SiC from crack initiation to final debonding. The IFSS, ISS, and G(i) of 2.5D SiCf/SiC are 56 MPa, (28 +/- 5) MPa, and (2.7 +/- 0.6) J/m(2), respectively. Values of ISS and G(i) indicate weak interface bonding, causing it susceptible to cracking under shear stress, while the large IFSS suggests that relative fiber sliding is inhibited after interface debonding, hindering fiber pull-out. The obtained interfacial properties can predict the proportional limit stress (sigma(PLS)) accurately according to the ACK model. Based on the interfacial properties and the in-situ fiber strength (sigma(fu)), the tensile strength of 2.5D SiCf/SiC is predicted to be higher than the experimental value, which is related to the interfacial radial compressive residual stress and residual tensile stress endured by the fiber.