The mathematical and associated computational modeling and analysis of mold filling, heat transfer, and polymerization reaction kinetics in Resin Transfer Molding (RTM) are quite complex and not only require accurate computational approaches to capture the process physics during the simulations, but also must permit complex geometric configurations to be effectively analyzed. The process simulations at a macroscopic level require the representative macroscopic constitutive behavior which can be predicted from a microscopic analysis of the representative volume element (RVE) of the fiber preform configurations. This is first presented here for purposes of illustration in reference to determination of the preform flow permeabilities. Next, an effective integrated micro/macro approach and developments including a viable flow solution modeling and analysis methodology with emphasis on providing improved physical accuracy of solutions and computational advantages are described for the transient flow progression inside a mold cavity filled with a fiber preform under isothermal and non-isothermal flow conditions. The improved physical accuracy and the overall effectiveness of the new computational developments for realistic process modeling simulations are first demonstrated for isothermal conditions. Subsequently, the new integrated flow/ thermal methodology and developments are extended for non-isothermal conditions. The highly advective nature of the non-isothermal conditions involving thermal and polymerization reactions also require special numerical considerations and stabilization techniques and are also addressed here. Finally, validations and comparisons are presented with available analytical and experimental results whenever feasible. Emphasis is also placed upon demonstrations for practical engineering problems.