SiC纤维表面去碳处理对PIP-SiC_f/SiC复合材料力学性能以及界面影响

Effects of Carbon Coating Removal of SiC Fiber on Mechanical Properties and Interface Characteristics of 2D-SiC_f/SiC Composites

采用强度测试、SEM、HRTEM等分析测试手段对纤维表面去碳前后SiC纤维强度、复合材料力学性能、纤维表面形貌、复合材料断口形貌以及复合材料界面特征进行分析表征。结果表明,去碳处理后,纤维表面的固有缺陷暴露出来,纤维强度下降约15%,但由其制备的复合材料强度下降只有原纤维制备复合材料的1/6;复合材料断口非常平整,纤维增韧效果差。分析表明,由于去碳后纤维表面缺陷增多,界面的物理结合增强以及由于基体开裂导致的纤维物理损伤加剧;去碳处理后纤维表面化学反应活性中心明显增加,导致界面化学结合和纤维化学损伤加剧。过强的界面结合和低的纤维就位强度使复合材料力学性能严重恶化。

The SiC fiber tensile strength and mechanical properties of 2D-SiCf/SiC composites,the fiber surface morphology,composite fracture surface morphology and composite interface characteristics before and after removing carbon coating were analyzed and characterized by bundle tensile test,three-point bending test,SEM and HRTEM.The results show that inherent defects on the surface of SiC fiber are exposed after the carbon coating removal,and the tensile strength of SiC fiber decreases by about 15%.The flexural strength of 2D-SiCf/SiC composites after the carbon coating removal is only 30 MPa,which is the 1/6 times of that of composites prepared by the original fiber.The fracture surface of 2D-SiCf/SiC composites after the carbon coating removal is very even,which proves the fiber reinforced effects to be poor.The analyzed results indicate that because of the increase of defects after the carbon coating removal,the interfacial physical bonding strength and the fiber physical damage will all increase.At the same time,after the carbon coating removal,the chemical action active centers and the oxygen contents on the fiber surface will increase,the situation of that will bring about the interfacial chemical bonding strength and the fiber chemical damage increasing,which has been proved by HRTEM test.The strongly bonded interface and serious fiber damage result in the mechanical properties of 2D-SiCf/SiC composites degrading badly after the carbon coating removal.