Modeling of an improved Chemical Vapor infiltration Process for Ceramic Composites Fabrication

Abstract

A quasi‐steady‐state approach is applied to model the pressure‐driven, temperature‐gradient chemical vapor infiltration (improved CVI process) for ceramic matrix composites fabrication. The deposited matrix in this study is SiC which is converted from the thermal decomposition of methyltrichlorosilane gas under excess hydrogen. A three‐dimensional unit cell is adopted to simulate the spatial arrangements of reinforcements in discontinuous fiber mats and three‐dimensionally woven fabrics. The objectives of this paper are to predict (1) the temperature and density distributions in a fibrous preform during processing, (2) the advancement of the solidified front, (3) the total fabrication period, and (4) the vapor inlet pressure variation for maintaining a constant flow rate. Furthermore, the effect of boundary temperature and inlet pressure variations on the total proassing period is also studied. The fabrication temperature examined in this paper is in the range between 873 and 1473 K, and the pressure is from 1.0001 to 2.0000 atm (1.0134 × 105 to 2.0265 × 105 Pa). Based upon this analysis, the influence of the reactor condition on the density of the final product in a CVI process can be quantified.