Investigations on the relationship between processing, microstructure and properties of one-step long-fibre reinforced polymer sandwich components

• Applicant: Professor Dr.-Ing. Peter Elsner (†)
• Subject Area: Plastics Engineering ; Polymer Materials
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 256610470

The aim of the project is the investigation of the relationship between processing, microstructure and properties of long-fibre reinforced polymer sandwich components processed in one step by different foam injection molding technologies. In detail, the well-established MuCell®-technology (Trexel Inc.) representing the state-of-the-art in this field and being therefore the reference technology in this project is compared to the novel LFT-D-foaming technique based on a gravimetric addition of the foaming agent inside a twin crew extruder. Both variants of Thermoplastic foam injection moulding (TSG) result in an integrally produced foam structure made from one material (LFT-D), possessing dense face sheets and hence representing a sandwich structure. All parts of the sandwich (face sheets and core foam) are long-fibre reinforced.For non-reinforced materials, the correlation between material properties, foam structure and processing parameters have been thoroughly researched on, while for long-fibre reinforced foams, these correlations are unknown up today. This gap will be closed by carrying out the proposed project. For this purpose, a modular shearing edge mould offering a variothermic process control to adjust the core/face sheet ratio wil be used and applied for respectively. Changeable mould inlays offer high flexibility regarding the component geometry (fins, beads, screw bosses) as well as the investigation of its influence on the foaming behaviour. In this regard, the question arises how the implemented fibres may influence the foaming process, how the foam/face sheet ratio may adjusted depending on the process parameters and how the fibres may be oriented inside the composite as an artefact from the foaming and injection process. Furthermore, it has to be clarified whether the correlations between process, microstructure and properties known from non-reinforced foams may be transferred to long-fibre reinforced foams. These findings will be correlated with the outcoming mechanical properties and consequently with material models for foam structures. Hereby, the behaviour under near-service, i.e. quasistatic or impact, loads is major interest. In this regard the difference between the two processes variants will be considered as the LFT-D-route allows for longer fibres in the final product in comparison to the MuCell®-technology.

• DFG Programme: Research Grants
• Major Instrumentation: Spritzgießwerkzeug
• Instrumentation Group: 2210 Kunststoffpressen und -spritzgußgeräte
• Participating Person: Professor Dr.-Ing. Kay A. Weidenmann