MULTIDIMENSIONAL MODELING OF CHEMICAL-VAPOR INFILTRATION - APPLICATION TO ISOBARIC CVI

Multidimensional (2D and 3D) chemical vapor infiltration models are fo rmulated and used to simulate densification of isotropic or anisotropi c preforms of various geometries using Sic deposition from methyltrich lorosilane. A generalized form of the dusty-gas model for mass transpo rt in anisotropic porous structures is used as a flux model in the por e space, and the multidimensional model equations are solved using the Galerkin finite element method. Structures consisting of freely overl apping fibers parallel to a Line (one-directional), parallel to a plan e (two-directional), or without preferred orientation (three-direction al) are employed to model the microstructure of the preforms. The obta ined results show that the effects of preform geometry can lead to par tial pressure and deposition profiles in the preform that are consider ably different from those suggested by one-dimensional analyses of the chemical vapor infiltration process.