Chemical vapor infiltration into woven fabrics produces lightweight composites of excellent physical and chemical properties. Deposition of two substances (graded deposition) can provide better thermal stability, corrosion and stress resistance than dcposition of a single substance (Kawai, 1990). The usual fabric consists of several plies of tows woven into a single layer. Each tow is a bundle of filaments (1,000 or more). Commonly those filaments are of carbon with a radius of the order of 4 X cm. There are three void regions in a fabric: (1) holes between the tows that run from ply to ply; (2) spaces between the plies; and (3) gaps around the individual filaments in a tow. Chung et al. (1992) gives a complete description of the geometry of a 13 ply fabric. Deposition occurs by gaseous diffusion into the three void regions with simultaneous chemical reaction to produce the solid deposit.Uniform deposition (densification) and limited void space throughout the fabric are desirable for optimum mechanical properties. The recently developed discrete model has the advantage of predicting the amount of deposition as a function of position and time anywhere in thc multilaycred fabric. The total amount of deposition at any location is the sum of deposit on the filaments (that is, in the gaps), in the spaces and on the walls of the holes. Chung et al. (1993) have recently extended the model to graded deposition of Sic and TiB,, utilizing available information on the kinetics of deposition and diffusivities of thc gaseous precursors, dichloro-dimethylsilane (DDS) and TiCI, (with BCI,). This model can be used to predict deposition profiles in the direction perpendicular to the plane of the plies, that is, in terms of the number of plies. Thus, the uniformity of dcposition can be calculated as a function of the geometry of the fabric (size of holes and spaces, filament spacing and fila-
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