Modeling of Forced Flow-thermal Gradient CVI: Effects of Control Parameters and Processing Schemes on a Densification

A two-channel temperature-control infiltration reactor aiming at fabricating thicker and more uniform composites was designed. Unsteady numerical simulations containing hydrodynamics, mass transfer, heat transfer and pore structure evolution were carried out. By analyzing the effects of concentration, velocity and temperature on the porosity distribution, different densification schemes were proposed and compared. Results show that a preform of thickness 0.04 m and initial porosity 0.8 can be densified to a uniform and compact one with the maximum porosity of 0.1 within 300 hours through the three-step densification scheme. This scheme not only assures a low and uniform porosity over the whole preform but also avoids the huge pumping pressure which may cause the preform cracking.