Abstract: A process for debulking a fiber reinforced composite structure prior to curing includes forming a stackup of a breather pad on a vacuum plate, a mandrel on the breather pad, a first release layer on the mandrel, a plurality of prepreg plies on the release first layer, a second release layer on the top ply, a breather sheet on the second release layer, and an impervious flexible vacuum bag sealed over the breather sheet to the vacuum plate; sealingly enclosing the stackup within a pressure vessel including an impervious flexible membrane which engages the vacuum bag; drawing a vacuum from within the vacuum bag through the breather pad and the vacuum plate; pressurizing the pressure vessel between the shell and the membrane; and maintaining the combination of vacuum and pressure for an interval of time to remove voids and porosity from the laminated prepregs.