Modeling of industrial isothermal chemical vapor infiltration process for C/SiC structural composites

Abstract

This study presents a comprehensive CFD model for the densification of carbon fiber-reinforced SiC structural composites using methyltrichlorosilane (MTS) as a precursor in an industrial chemical vapor infiltration (CVI) process. The model integrates off-preform and in-preform phenomena by coupling reactor fluid flow with gas transport within the porous medium. Preform microstructure, characterized by porosity distribution and internal surface area, is analyzed using SEM imaging. The effect of pressure and temperature on CVI process dynamics, including species concentration distribution, densification rate, and evolving pore structure, is investigated. The study indicates that temperature has a more pronounced effect on densification compared to pressure. Simulation results are validated by comparing predicted overall density and residual porosity distribution to experimental measurements, demonstrating good agreement. The temperature-dependent behavior of the Thiele modulus underscores its importance in understanding and optimizing the densification process. The present model is expected to enhance the CVI process by minimizing the number of experimental trials required for various process conditions. © 2025 The American Ceramic Society.