Thermoformable sandwich composite workpiece for molding three-dimensional products comprises core, fiber reinforced resin and film facing layers enclosed in porous evacuation layers and covering films

摘要

The sandwich construction comprises a preform stack with a core layer(5), fiber reinforced unreacted resin layers(2) and film facing layers(3). The sandwich is enclosed by porous evacuation layers(4) and sealed from the outer atmosphere by covering layers(1). Air is evacuated from the sandwich preform before pressing so that it forms more easily on the molding tool and the resin is cured while the preform is in contact with the tool surface. The closed cell core material(5) stiffens the sandwich construction before it is formed onto the tool. Use of an open pored fleece or fabric with suitable extension for air evacuation of the sandwich allows good drapability over the molding tool. Forming is performed at an elevated temperature which permits easy forming of the thermoplastic parts, but does not initiate premature gelation of the resin. An independent claim is included for the heating and forming equipment which also has the capability to form the workpiece against a molding tool face using positive pressure on the outside of the workpiece.