Gestaltungs- und Verarbeitungsempfehlungen für den Strukturleichtbau mit geschäumten langglasfaserverstärkten Thermoplasten

Thermoplastic foam injection moulding (FIM) with blowing agent loading through sluice systems offers greater design freedom and gentler plasticising compared to compact injection moulding. This thesis therefore uses practical tests to analyse the advantages of FIM in the processing of long glass fibre reinforced thermoplastics (LFT) and to develop design and processing recommendations for lightweight structural construction. In the first step, the influence of FIM on melt viscosity and fibre length after plasticising is investigated in order to derive recommendations for the plasticising parameters. During the tests, the FIM achieves a significant reduction in melt viscosity and fibre breakage. Based on this, the effect of cell formation on fibre-matrix adhesion is discussed. For the development of design recommendations, flow spirals with different wall thicknesses and flow path lengths as well as different ribs are produced and analysed. Using various statistical methods, the relationships between the dimensional accuracy, the mechanical and morphological properties and the moulded part geometry are identified and design recommendations are developed. In addition, the influence of the injection moulding parameters on the mechanical and morphological properties is analysed for certain ribs and wall thicknesses. It is shown that the influence of the injection moulding parameters is not significant, but the moulded part geometry has a significant influence on the mechanical and morphological properties and the moulded part geometry is therefore essential for the use of foamed LFT in lightweight structural design. Finally, to validate the design and processing recommendations, the lye container of a washing machine with several metal inserts is analysed as a complex demonstrator. The foamed lye containers with a weight reduction of 7 % achieve comparable mechanical properties to the compact reference. At the same time, shrinkage at the end of the flow path and warpage can be reduced by the FIM. As part of this work, the potential of the developed design and processing recommendations for lightweight structural construction with foamed LFT can thus be demonstrated in practical tests.