化学气相浸渗2D Cf/(SiC-C)复合材料的微观结构与强韧性

采用等温等压化学气相浸渗法(ICVI)制备了二维碳纤维增韧碳化硅碳二元基复合材料(2D C_f/(SiC-C)).利用扫描电镜(SEM)和背散射电子成像(BSE)研究了其基体的微观结构, 并与二维碳纤维增韧碳化硅陶瓷基复合材料(2D C_f/SiC)比较了室温力学性能和断口形貌.结果表明：2D C_f/(SiC-C)复合材料的基体是由SiC与热解碳(PyC)组成的多层结构, PyC基体层分布均匀而连续, 且与SiC基体层结合紧密.纤维束内部PyC基体层较厚的2D C_f/(SiC-C)复合材料具有较高的强韧性, 其拉伸强度、断裂应变、断裂韧性和断裂功分别比2D C_f/SiC复合材料的提高了3%、142%、22%和58%.SiC与PyC组成的多层基体使2D C_f/(SiC-C)复合材料的纤维在拔出过程中发生了两次集中拔出, 且第一次集中拔出的纤维对复合材料的强韧性起主要作用.

Microstructures, Strength and Toughness of 2D Cf/(C-SiC) Composites by Chemical Vapor Infiltration

Two dimensional carbon fiber-reinforced silicon carbide-carbon binary matrix composites (2D C_f/(SiC-C)) were fabricated by means of isothermal and isobaric chemical vapor infiltration (ICVI). The matrix structures of the 2D C_f/(SiC-C) composites were characterized by the backscattered electron imaging (BSE) of scanning electron microscope (SEM). Furthermore, their room temperature mechanical properties and fracture surfaces were compared with two dimensional carbon fiber-reinforced silicon carbide matrix composite (2D C_f/SiC). The results indicate that the matrices in the 2D C_f/(SiC-C) composites are multilayered structures composed of SiC and PyC layers. The PyC matrix layers are homogeneous and continuous, which are bonding well with SiC matrix layers. The 2D C_f/(SiC-C) composite with a thicker PyC matrix layer in fiber bundles exhibits better mechanical properties. Meanwhile, its tensile strength, failure strain, fracture toughness and fracture work are 3%, 142%, 22% and 58% higher than those of the 2D C_f/SiC composite, respectively. The multilayered matrices composed of SiC and PyC layers, cause the fibers in the 2D C_f/(C-SiC) composites to pull out twice in a concentrated mode. Moreover, the first pull-out fibers play a leading role in enhancing the strength and toughness.