A system and method for processing a preform in a vacuum vessel to produce a structural assembly are provided. The system includes a heated die set defining a cavity in which the preform can be formed, bonded, or otherwise processed. The die set is disposed in a cavity of the vacuum vessel from which gas can be evacuated. Thus, a pressurized fluid can be provided to the preform, e.g., to an interior space of the preform to form or constrain the preform in the die cavity, and the vacuum vessel can be evacuated so that the die set, and typically the preform, are exposed to a pressure that is reduced relative to the ambient pressure. Further, the vacuum vessel can constrain the die set in the closed position during processing.