This paper presents the mathematical theory, computational algorithm and nu
merical results from a finite element based Resin Transfer Molding (RTM) mo
del, a process that involves resin impregnation of fiber preforms. The uniq
ueness of the present approach is that unlike the conventional methods, it
treats the flow of resin and air as a two-phase flow in a porous media. The
formulations are done in 3D without introducing approximations in the thic
kness direction. This approach enables the user to model the macrolevel phy
sics better, formulates accurate filling of complex parts that may be thick
or contain inserts, predicts air entrapment, and has the ability to incorp
orate heat transfer in both filled and unfilled regions.