| Popis: |
This paper analyses the lightweight potential of long-fiber-reinforced and local continuous-fiber-reinforced foam injection molded components. Using the LFT-D foam process [7, 13] and breathing mold technology [11, 12], long-glass-fiber-reinforced polypropylene foams were manufactured with a constant weight per unit area and varying density reductions. As the area moment of inertia increases with the wall thickness to the third power, in these investigations small density reductions were sufficient to increase the flexural rigidity by several hundred% compared to a compact reference sample. The fiber length advantage generated by the direct process (injection molding compounding) also meant that even at higher density reductions the ductility was not reduced by the foaming. In order to achieve even better mechanical properties, foam injection molding can be combined with local continuous-fiber reinforcement. To demonstrate the potential, sandwich integral foam components with local continuous-fiber-reinforced facing were produced in-situ in an injection mold and characterized. Fully-consolidated tape blanks and self-reinforced PP fabrics were positioned on both sides of the cavity and heated. Afterwards a gas-loaded melt was injected between them. A short embossing stroke generated sufficient interfacial adhesion between the facing layers and the core material, and the foaming process was initiated by the pressure drop resulting from the precision opening of the injection compression mold. |
