GAS-TRANSPORT MODEL FOR CHEMICAL-VAPOR INFILTRATION

A node-bond percolation model is presented for the gas permeability an d pore surface area of the coarse porosity in woven fiber structures d uring densification by chemical vapor infiltration (CVI), Model parame ters include the number of nodes per unit volume and their spatial dis tribution, and the node and bond radii and their variability, These pa rameters relate directly to structural features of the weave. Some unc ertainty exists in the proper partition of the porosity between ''node '' and ''bond'' and between intra-tow and inter-tow, although the tota l is constrained by the known fiber loading in the structure. Applied to cloth layup preforms the model, gives good agreement with the limit ed number of available measurements.