短切碳纤维含量对C_(sf)/SiC复合材料力学性能的影响

EFFECT OF SHORT CARBON FIBER CONTENT ON THE MECHANICAL PROPERTIES OF COMPOSITE C_(sf)/SiC

以Si作为主要烧结助剂,采用热压烧结法制备了短切碳纤维-碳化硅(short carbon fiber reinforced SiC composite,Csf/SiC)复合材料。采用X射线衍射仪、扫描电镜、硬度仪以及力学性能试验机等,研究了Csf含量对所制备材料的结构、组成、形貌及复合材料的弯曲强度、Vickers硬度和断裂韧性的影响。结果表明:采用热压法能制备出致密且Csf分布均匀的Csf/SiC复合材料。Csf/SiC复合材料的弯曲强度随Csf含量增加先增大后减小,含15%(体积分数,下同)Csf的Csf/SiC样品强度最高,达到466MPa,并且Csf含量小于30%的Csf/SiC样品强度高于无纤维SiC材料。材料的Vickers硬度随Csf含量增加而降低。Csf/SiC样品的断裂韧性随Csf含量增加而逐渐增大,Csf含量为53%时,达到最大为5.5MPa.m1/2,与无纤维SiC样品相比,增加近2倍。

Short carbon fiber reinforced silicon carbide （Csf/SiC） composites were fabricated by the hot pressing method using Si as the main sintering aid. The effects of the content of the short carbon fibers on microstructure, bending strength, Vickers hardness and fracture toughness of the composites were investigated. The results show that the Csf/SiC composites prepared by hot pressing are dense and the short carbon fibers are homogeneously distributed in the matrix. The bending strength of the composite begins increasing and then decreases with the increase of the short carbon content, and the Csf/SiC composites with 15% （in volume, the same below） Csf has the highest bending strength （466 MPa） and the bending strengths of the composites with less than 30% Csf are all higher than that of monolithic SiC. The Vickers hardness of the composites decreases with the increase of short carbon fiber content. The fracture toughness of the composites increases with the increase of Csf content, and composites with 53% Csf have the highest fracture toughness, 5.5 MPa·m^1/2, which is nearly two times greater than monolithic SiC.