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采用化学气相渗透(CVI)工艺分别对整体毡和针刺毡厚壁预制体进行了500 h的致密化,研究了2种预制体的致密化效率、微观结构及密度分布情况。结果表明:预制体结构对C/C复合材料的致密化行为影响较大。致密化前期,整体毡预制体表现出较高的致密化效率,后期效率下降较快,热解炭包裹在纤维之间,材料内部密度分布不均,呈现两边高中间低的现象。针刺预制体在CVI前期致密化效率较低,热解炭主要包裹在纤维束外,致密化后期致密化效率下降较慢,致密后材料内部密度分布均匀。与整体毡预制体相比,针刺预制体的孔隙平直,分布均匀,更有利于碳源气体的深入渗透以获得均匀的密度分布。
The thickening preforms of monolithic felt and acupuncture felt were densified by chemical vapor infiltration (CVI) for 500 h. The densification efficiency, microstructure and density distribution of the two preforms were studied. The results show that preform structure has a great influence on the densification behavior of C / C composites. In the early stage of densification, the whole felt preform showed a higher densification efficiency and a rapid decrease in the latter stage efficiency. Pyrolysis charcoal was wrapped between the fibers, and the internal density of the material was unevenly distributed, showing a phenomenon of low middle and high sides on both sides. The densification efficiency of acupuncture preform in the early stage of CVI is low, the pyrolytic carbon is mainly wrapped in the fiber bundles, the densification efficiency slows down after the densification, and the internal density distribution is even after densification. Compared with the whole felt preform, the preform of acupuncture has straight and uniform pores and is more conducive to the penetration of the carbon source gas to obtain a uniform density distribution.