LIU Yaoyao, HAI Weibin, PENG Yuqing, LI Aijun, ZHANG Fangzhou

(School of Materials Science and Engineering, Shanghai University, Shanghai 201800, China)

Abstract: The densification process of 2D laminated SiC fiber preform was simulated under the condition of isothermal chemical vapor infiltration. According to the mass transfer process and reaction kinetics calculations, the dual active site competition model and the pore evolution process are developed. It was found that the pores which are smaller than 10 μm in the preform bundle are preferentially filled, so that the pores between the bundles are gradually filled into the small ones.When the porosity is reduced to 20%, there are equivalent pores of about 50 μm inside the preform. There are two stages in the variation of specific surface area of the preform. When porosity is above 40%, the specific surface area decreases quickly. The simulation results under specific process conditions indicate that densities of the composite are in the range of 2.48–2.38 g·cm−3, while the maximum error is 0.73%. The porosity is in the range of 13.94%–17.75%, with maximum error to be 4.21%. Changes in gas-phase component concentrations indicate that silicon-rich composites are more likely to be formed under this process condition.

Key words: SiCf/SiC composites; chemical vapour infiltration; dual

active site competition model; pore evolution