A process for molding composites in which a film material is placed over the lay-up on the mold and sealed so that a vacuum can be applied to allow atmospheric pressure to help form the composite. A process using a two-sided mould set that shapes both surfaces of the panel. On the lower side is a rigid mould and on the upper side is a flexible membrane or vacuum bag. The flexible membrane can be a reusable silicone material or an extruded polymer film. Then, vacuum is applied to the mould cavity. This process can be performed at either ambient or elevated temperature with ambient atmospheric pressure acting upon the vacuum bag. Most economical way is using a venturi vacuum and air compressor or a vacuum pump.
A process for molding reinforced plastics in which a sheet of flexible transparent material such as nylon or Mylar plastics is placed over the lay-up on the mold and sealed. A vacuum is applied between the sheet and the lay-up. The entrapped air is removed by the vacuum and the part is placed in an oven or autoclave. The addition of pressure further results in higher fiber concentration and provides better adhesion between layers of sandwich construction. Also known as vacuum bagging.
A method for fabricating fiber reinforced resin matrix composite structures having molded outside surfaces with intermittent molded inside surfaces (e.g. an aircraft skin with internal stiffeners) is performed as follows: composite prepreg stiffener sections are preformed and laid up on the inside portion of the rigid portion of the vacuum bag and the lay-up debulked. Elastomeric tubes are then installed in rigid cavity portions of a hybrid vacuum bag and sealing wedges are forced into place to hold the elastomeric tubes and at the same time seal them to the rigid portion of the cavity. The elastomeric tubes extend through and protrude from the sealing wedges. Skin plies are then laid up on a primary mold and the hybrid bag installed on the mold. Index pins are provided to properly orient the hybrid bag to the primary mold or tool. A vacuum is then drawn on the bag, any vacuum leaks are remedied, and the part is ready for curing in either an oven or an autoclave. After curing, the sealing wedges are removed and a vacuum is drawn on the elastomeric tubes to collapse them for easy removal. After removal of the elastomeric tubes and the hybrid bag the completed structural part is removed from the primary tool.
