表面涂碳及复合材料制备对SiC纤维性能的影响

Effect of carbon coating and composite fabrication process on tensile strength of SiC fibers

采用化学气相沉积法对SiC(W芯)纤维进行表面涂碳处理,分别用未涂碳SiC纤维和涂碳SiC纤维作为增强体,通过真空热压制备了SiC/Ti-6Al-4V复合材料,然后从复合材料中萃取出SiC纤维。拉伸实验表明,纤维表面涂碳有效地增加了SiC纤维的抗拉强度,但萃取出的SiC纤维强度明显降低。统计研究表明,SiC纤维的强度服从威布尔分布,碳涂层使纤维的威布尔模数增大但复合材料制备降低了威布尔模数。扫描电镜观察证明SiC纤维的断口呈现出明显的脆性断裂特征,涂碳处理明显减少了SiC纤维的表面缺陷,从而提高了其强度,减少了强度分散性,涂碳处理还可以减少Ti基复合材料制备过程中对纤维表面的损伤。

A thin carbon layer was coated onto SiC fibers （W core） through chemical vapor deposition. Ti-6Al-4V matrix composites reinforced by the SiC fibers without and with carbon coating were prepared respectively by means of hot pressing and then the fibers were extracted from the composites. Tensile strength of the fibers was measured in order to investigate the effects of the carbon coating and the hot pressing. It is found that the tensile strength of the fiber increases greatly after depositing the carbon coating but that of the extracted fiber decreases. The strength distribution of the SiC fibers obeys the Weibull function and the Weibull modulus increases for the carbon coated fibers but decreases for the extracted fibers. A brittle fracture characteristic of the fiber was observed by using scanning electron microscope. However, it is showed that the carbon coating reduces the surface defects of the fibers and therefore increases the strength and reduces the strength dispersity of the SiC fibers. Meanwhile, the carbon coating can also reduce the surface damage of the fibers during the fabrication process of Ti-matrix composites.