Modeling of isobaric-isothermal chemical vapor infiltration: effects of reactor control parameters on a densification

This work deals with the integration of off-preform and in-preform physico-chemical phenomena involved in isothermal isobaric CVI for processing of ceramic-matrix composites (CMC). A global modeling approach featuring coupled reactor fluid mechanics and porous medium gas transport has been developed. The coupling between transport and reaction phenomena inside and outside the preform is rather strong, both physically and numerically. In a model case study of SiC infiltration from methyltrichlorosilane in a fibrous preform, the impact of the free medium on densification is proved, quantified and discussed, especially through flow rate and reactor diameter variations. Important counter-effects of the reactive preform on the surrounding gas-phase composition are shown; also, the effect of true experimental parameters is investigated. The total densification time is affected by the gas flow rate and the density field evolution relies both on the flow rate and the reactor diameter. Such an approach brings new guidelines for the optimization of perform.