短纤维C/C-SiC复合材料的组织结构与断裂机制

Structure and fracture mechanism of short fibre reinforced C/C-SiC composites

采用水悬浮分散法制得含Si短炭纤维料饼,经树脂浸渍、模压成形和炭化后成为预制体,经反复浸渍/炭化增密和高温反应生成SiC,制备了C/C-SiC复合材料。利用光学显微镜、扫描电镜和X射线衍射对其组织结构特征和断裂机制进行研究。结果表明C/C-SiC复合材料的增强相短炭纤维具有垂直于压力方向的平面内随机取向的层状结构,平行于压力方向上分布的纤维较少;基体中的碳化硅为β-SiC,在C/C-SiC复合材料中主要分布在纤维与基体、纤维与纤维之间的各种缝隙中和原来硅颗粒所处的位置附近;C/C-SiC复合材料弯曲破坏属于脆性断裂,微观破坏机制主要表现为短炭炭纤维的“拔鞘”、脱离或脆断,以及基体炭和碳化硅的脆性断裂。

Short carbon fibre reinforced carbon and silicon carbide （C/C-SiC） composites were manufactured in four steps, the dispersion of short carbon fiber and silicon powder by water suspension method; after polymer impregnation, compression moulding and carbonization to obtain the green body consisting of the dispersed fiber and silicon; densification by multiple cycles of polymer impregnation and carbonization; generation of silicon carbide by means of high temperature reaction. The structure feature and fracture mechanism of C/C-SiC composites were studied by means of optical microscope, scanning electron microscopy and X-ray diffraction. The results show that C/C-SiC composites have a laminated structure with preferred orientation of short carbon fibres, and only a few fibres are found in vertical direction. β-SiC is mainly distributed in the gaps between fibres or fibre and matrix, and vicinity of the original sites of silicon powder. The flexural failure of C/C-SiC composites is results from brittle fracture. The micro-fracture mechanisms are shown as the pull-out, separation or brittle failure of the short carbon fibres, and the brittle fracture of carbon and silicon carbide matrixes.