Microstructure evolution and mechanical properties of C/C-SiC composites prepared with different prefabricated structures
C/C-SiC composites were prepared by chemical vapor infiltration (CVI) and reactive melt infiltration (RMI) using carbon fiber preforms with stitched and needle-punched structures. The microstructure and pore characteristics of C/C porous composites obtained from the two structural preforms,as well as the microstructure and flexural properties of C/C-SiC composites,were systematically studied. Results show that the pore size of stitched C/C porous composite is multimodal distribution,and the pores are mostly inter-bundle pores. The pore size of needle-punched C/C porous composite is unimodal distribution. Due to the addition of mesh,some inter-bundle pores are transformed into connected small pore networks. The simulated absolute permeability in the Z direction of the latter is slightly greater than that of the former,which is conducive to the subsequent RMI densification process of the latter (high density,low open-porosity and low residual metal). The average flexural strength of stitched C/C-SiC composites is higher than that of needle-punched C/C-SiC composites,both of which exhibit a "pseudo plastic" fracture mode. The needle-punched C/C-SiC composite has a higher density and lower residual Si content,but its fiber volume content is lower,and the integrity of long straight fibers is poor,resulting in lower load-bearing property of the composite.
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