石墨化处理对三维针刺C/C复合材料力学性能的影响

Effects of graphitization on mechanical properties of 3D needled C/C composites

以T700碳纤维三维针刺整体毡为预制体,利用高压液相浸渍-碳化周期循环致密工艺制备三维针刺中间相沥青基C/C复合材料。用XRD、SEM及力学性能测试研究了三维针刺C/C复合材料的微观结构与弯曲断裂机制。结果表明:随着浸渍-碳化次数的增加,三维针刺C/C复合材料的密度、抗弯强度和杨氏模量逐渐增大,石墨化处理使三维针刺C/C复合材料的石墨层间距减小,石墨化度提高。经2800℃石墨化处理后,三维针刺C/C复合材料中纤维与基体间界面结合减弱,复合材料的抗弯强度减小并表现出韧性断裂特征。

Three dimensional（3D） needled mesophase pitch-based C/C composites were manufactured by high pressure liquid impregnation-carbonization and graphitized at 2600 ℃ and 2800 ℃.The polyacrylonitrile（PAN） based carbon fiber（T700） preform was prepared by three-dimensional needling.The microstructure and flexural fracture mechanism of the 3D needled C/C composites were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and mechanical property tests,respectively.Results indicate that the bulk density,flexural strength and Young’s modulus of the 3D needled mesophase pitch-based C/C composites increase with increasing of impregnation-carbonization times.After graphitization,the graphite layer distances of C/C composites decrease and graphitization degrees increase.When graphitizing at 2800 ℃,the flexural strength of the 3D needled C/C composite decreases because the interface bonding between carbon matrix and carbon fibers is weakened,and the 3D needled C/C composites show non-brittle fracture behavior.