SiC纤维预制体结构对SiCf/BN/SiC复合材料致密化和力学性能的影响OA北大核心

In order to study the effect of silicon carbon(SiC)fiber preform structure on the densification process of SiC matrix by chemical vapor deposition(CVI)process,the pore structure evolution of SiC preform with 2D,2.5D and 3D structures during the densification process was analyzed using simulation method;and SiCf/BN/SiC composites with three kinds of SiC fiber preform structures were prepared by CVI process using boron trichloride-ammonia-hydrogen-nitrogen(BCl3-NH3-H2-N2)and trichloromethylsilane-hydrogen(MTS-H2)gas mixture as precursor.The results show that the densification efficiency of SiCf/BN/SiC composites varies with SiC fiber pre-forms structure.The densification rate of 2.5D preform and 3D preform is the fastest and the slowest,respectively.After 120 h,the density of three kinds of structure SiCf/BN/SiC composites was more than 2.3 g/cm3 and the po-rosity was about 10%.The tensile strength of the three kinds of SiCf/BN/SiC composites was 130～170 MPa.In the process of interlaminar shear,2D SiCf/BN/SiC composites and 2.5D SiCf/BN/SiC composites showed fiber strip-ping in XY plane,while 3D SiCf/BN/SiC composites showed the highest interlaminar shear strength and the fracture of orthogonal Z-direction fibers occurred.Therefore,the densification process and mechanical properties of the com-posite were affected by the SiC fiber preform structure.