CVD-SiC界面改性涂层对气相渗硅制备C_f/SiC复合材料力学性能的影响

在气相渗硅制备C_f/SiC复合材料时,界面改性涂层非常重要。良好的界面改性涂层一方面起到保护碳纤维不受Si反应侵蚀的作用,另一方面起到调节纤维和基体界面结合状况。通过在C纤维表面制备CVD-SiC涂层来进行界面改性,研究CVD-SiC界面改性涂层对GSI C_f/SiC复合材料力学性能和断裂特征的影响,并分析其影响机制。结果表明:无CVD-SiC涂层改性的C_f/SiC复合材料力学性能较差,呈现脆性断裂特征,其强度、模量和断裂韧度分别为87.6MPa,56.9GPa,2.1MPa·m1/2。随着CVD-SiC涂层厚度的增加,C_f/SiC复合材料的弯曲强度、模量和断裂韧度呈现先升高后降低的趋势,CVD-SiC涂层厚度为1.1μm的C_f/SiC复合材料的力学性能最好,其弯曲强度、模量和断裂韧度分别为231.7MPa,87.3GPa,7.3MPa·m1/2。厚度适中的CVD-SiC界面改性涂层的作用机理主要体现在载荷传递、"阻挡"Si的侵蚀、"调节"界面结合状态3个方面。

Effect of CVD-SiC Interface Modification Coating on the Mechanical Properties of Cf/SiC Composite Prepared by Gaseous Silicon Infiltration Process

The interface plays a key role on the mechanical properties of Cf/SiC composite prepared by GSI process.The ideal interface should not only prevent carbon fiber from being etched by Si vapor,but also adjust the bonding force between C fiber and SiC matrix.SiC coating prepared by CVD was chosen as the interface and its effect on the mechanical properties and fracture features of GSI Cf/SiC composite was discussed,and the influencing mechanism was analyzed.The results show that GSI Cf/ SiC composite without CVD-SiC interface has poor mechanical properties,exhibiting brittle fracture feature.The bending strength,elastic module and fracture toughness are 87.6MPa,56.9GPa and 2.1MPa · m1/2,respectively.The mechanical properties of GSI Cf/SiC increase with the increase of the thickness of CVD-SiC coating at first,then decrease with the continuous increase of the thickness of CVD-SiC coating.The Cf/SiC composite with 1.1μm thickness of CVD-SiC coating has the best mechanical properties,and the bending strength,elastic module and fracture toughness are 231.7MPa,87.3GPa and 7.3MPa · m1/2,respectively.The action mechanism of CVD-SiC interface coating on the composite is mainly on the three aspects:load transfer,preventing C fiber from being etched by Si and adjusting fiber/matrix bonding status.