Injection molding of glass fiber reinforced polypropylene composite foams with laminate skins

Sandwich panels which consist of discontinuous glass fiber reinforced polypropylene composite foam core and continuous glass-fiber reinforced polypropylene laminate skins were manufactured using industry-scale equipment in a streamlined manner. The process included the two stages: (1) continuous glass-fiber reinforced polypropylene laminates as the face skins were produced using an automated tape layup machine and a hydraulic press and (2) discontinuous glass-fiber reinforced polypropylene composite as the core was foam injection-molded onto the face laminates (i.e., overmolding) with a physical blowing agent, nitrogen. The results suggested that the addition of the laminate skins and foaming by the core-back (or mold opening) technique can greatly reduce weight of material needed to have the same bending stiffness and maximum bending force.