The present application relates to a method and system that can be utilized to manufacturing composite structures in a closed cavity mold. The tool system includes a closed cavity tool with spring members that when in compression apply pressure to a preform located within the closed cavity mold. During a curing cycle, the spring members provide substantially constant pressure to the preform, thereby preventing voids and porosity in the cured composite structure. Further, the substantially constant pressure, provided by the spring members, acts to more effectively conform the preform to the geometry defined by a void in the closed cavity mold during the curing cycle.