国产三代 2.5D SiC_f/SiC 复合材料的界面力学性能

Continuous silicon carbide fiber reinforced silicon carbide composite (SiC_f/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 SiC_f/SiC and investigated its relationship with tensile properties. The residual stress of the 2.5D SiC_f/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 (σ _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 SiC_f/SiC from crack initiation to final debonding. The IFSS, ISS, and G_i of 2.5D SiC_f/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 (σ _PLS ) accurately according to the ACK model. Based on the interfacial properties and the in-situ fiber strength (σ _fu ), the tensile strength of 2.5D SiC_f/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.