STRUCTURAL MODEL EFFECTS ON THE PREDICTIONS OF CHEMICAL-VAPOR INFILTRATION MODELS

The effects of pore structure evolution on the predictions of chemical vapor infiltration models are investigated in this study. A general m ulticomponent reaction and transport model is used to describe transpo rt and reaction in the pore space, and structure evolution is modeled by representing the void space by a population of cylindrical capillar ies (capillary models) or of the solid phase by a population of solid cylinders (fiber models). The capillaries are assumed to be randomly a rranged in space without preferred orientation, whereas the fibers are taken to be parallel to a line, parallel to a plane, or without prefe rred orientation (one- two- or three-directional structures, respectiv ely). The obtained results show that the way in which the pore structu re evolves during densification plays a dramatic role in determining t he overall behavior of the deposition system. In the case of the fiber structures, the results are influenced significantly not only by the directionality but by the direction of diffusion relative to the fiber axes as well.