设计一种沿着厚度方向分为“上中下”3层结构的密度梯度变化预制体，并采用该预制体经化学气相渗透法制备了C／C复合材料。采用恒温氧化实验研究了该预制体结构对C／C复合材料的氧化性能的影响。结果表明，变密度预制体没有改变C／C复合材料的氧化模式，即氧化动力学模式和扩散模式。预制体结构的变化对氧化动力学模式没有影响，但由于变密度预制体改变了C／C复合材料内部孔隙结构的变化，阻碍了氧气在材料内部的扩散，从而提高了C／C复合材料的高温抗氧化性能。
Carbon fiber preform was designed to three layers with variable density along the thickness .Then C/C composites were obtained bychemical vapor infiltration (CVI) .Theinfluence of preform structure on the oxida‐tion behavior of C/C composites was studied by isothermal oxidation test .The results show that the oxidation of C/C composites with variable density preform has the same modes to that of traditional C/C composites ,kinetic rate controlled mode and the diffusion rate controlled mode .The variable density preform has little or no influ‐ence on the kinetic rate controlled mode ,but hinders the oxygen diffusion due to the pore structural change . Therefore ,the high temperature oxidation resistance of C/C composites was improved .
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