Process and mold development of direct long fiber reinforced foam injection molding on the example of polycarbonate and glasfibers

To achieve the demands of lightweight design in the automotive or aerospace industry it is necessary to optimize certain composite material groups with respect to their lightweight potential. Sandwich composites generally consist of a core which is coated with two face-layers. Task of the core is to transfer shear loads, while the face-layers absorb the tensile and compressive loads occurring at bending stress and are relevant for the surface quality. Current research aims to increase the efficiency of said sandwiches while minimizing the weight per area by using for example (fiber-) reinforced face-layers. It is also attractive to reduce the number of manufacturing steps needed to produce a sandwich composite. This can be achieved by connecting the face and core layers in-situ by a so-called in mould assembly process. As an approach to create these benefits, the thermoplastic foam injection molding (FIM) - a special injection molding process - is used in combination wi th a single material system. Within this work, foamed and/or long fiber reinforced polycarbonate blanks were manufactured using a combined foam injection molding and compounding process. The different blanks - unreinforced polycarbonate (PC), fiber reinforced PC, foamed PC and fiber reinforced and foamed PC - were produced using a special developed and designed injection mold, which - amongst other features like inserts for functional elements - enables an insight into viscosity and shear rates of the injected material system. Several specimen were tested on their Charpy impact strength and their fracture surface was investigated using SEM images to verify the fiber-matrix bonding.