高温下C/SiC复合材料弯曲断裂性能实时测试和微观结构表征分析

In-situ Measurements of Bending Fracture Behavior and Microstructure Analysis of C/SiC Composites under High Temperatures

采用先驱体浸渍裂解法制备三维编织的C/SiC复合材料,利用自主研发的高温散斑制作技术和改进的三维变形光学测试系统,基于数字图像相关技术测试原理,在高温小尺度下实时表征分析C/SiC复合材料的力学性能。运用X射线衍射和扫描电子显微镜测试分析了材料高温氧化情况、显微组织结构及裂纹扩展情况。研究表明:温度对C/SiC复合材料的性能有很大的影响。随着温度的升高,材料由脆性断裂逐渐转变为韧性断裂;材料的断裂韧性由7.98±0.12MPa·m^(1/2)减小到2.76±0.11MPa·m^(1/2),断裂强度从251.40±2.71MPa减小到86.94±1.82MPa。本文为掌握C/SiC复合材料的高温失效机理提供了一种有效的实验测试技术和方法。

In the present work, the carbon fiber reinforced silicon carbide matrix （C/SiC） composites were prepared by the precursor infiltration and pyrolysis method. The corresponding fracture characteristics of C/SiC composites were studied by combining single edge notch beam and digital image correlation （DIC） techniques at elevated temperatures. The full/local displacement, strain and cracking information of C/SiC composites can be real time monitored and recorded by DIC technique with our developed special speckle patterns at 1500℃ and 1600℃. The results show that the fracture toughness of C/SiC composites decreases from 7.98±0.12MPa · m1/2 to 2.76±0. 11MPa · m1/2 with the increasing of experimental temperatures. And their crack strength decreases from 251.40 ±2.71 MPa to 86. 94 ±1. 82MPa. The high-temperature oxidation, microscopic structure, and cracking growth of C/SiC composites were analyzed by X-ray diffraction and scanning electron microscope. The proposed experimental test method is useful for investigating the high-temperature mechanical characteristics of advanced C/SiC materials and failure mechanisms under different temperatures.