高温空气下C/SiC复合材料断裂韧性实时测试和微观结构表征分析

为了研究高温空气下C/SiC复合材料断裂韧性和微观结构，采用单边切口梁三点弯曲法实时测试了C/SiC复合材料在高温空气下的断裂韧性，并采用电子扫描显微镜 (scanning electron microscope，SEM)和X 射线衍射分析仪 (X-ray diffraction, XRD)分析了复合材料在不同温度下的破坏断口和失效机制。研究结果表明随测试温度升高，C/SiC复合材料断裂韧性降低，材料的断裂形式由脆性断裂逐渐演变成塑性断裂。从室温升温到1 000 ℃测试温度条件下，C/SiC复合材料的断裂韧性由12.5 MPa·m1/2降低为10.96 MPa·m1/2，降幅仅为12%，C/SiC复合材料高温断裂韧性良好。不同温度下，材料呈现出不同形式的断裂形貌。常温下断口形貌主要可以看到纤维拔出的现象，随着温度的升高，该现象基本消失，断裂截面变得更平整，材料的强度主要取决于基体的强度。

In-situ measurements of fracture toughness and microstructure characterization of C/SiC composites at elevated temperatures in air

To study the fracture toughness and microstructure of C/SiC composites at elevated temperature in air, the fracture toughness of C/SiC composites at elevated temperature in air was in-situ measured by SENB (single edge notch beam) under TPB (three point bending) method. The fracture and failure mechanism of the composites at different temperatures were analyzed by SEM (scanning electron microscope) and XRD (X-ray diffraction). The results show that with the increase of temperature, the fracture toughness of C/SiC composites decreases, and the fracture mode gradually changes from brittle fracture to plastic fracture. The fracture toughness of C/SiC composites decreases from 12.504 MPa·m1/2 to 10.958 MPa·m1/2 with a reduction of 12% from room temperature to 1 000 °C. The material exhibits a good high-temperature fracture toughness. Under different temperatures, the material exhibits different modes of fracture morphology. At the normal temperature, the fracture morphology can mainly show the phenomenon of fiber pull-out. With the increase of temperature, the phenomenon basically disappears, the fracture cross section becomes flatter, and the strength of the material mainly depends on the strength of the substrate.