Development of a high-performance natural fiber composite for structural components – HyPer-NFK

Author: Kusmin, A.

Multiaxial fabrics are frequently used in industrial lightweight construction as a reinforcing structure for fiber-reinforced composites subjected to high mechanical loads. These are manufactured from continuous-filament rovings based on glass, carbon, or aramid. However, the use of these materials requires a high energy input during fiber production and thus leads to high CO2 emissions during the production of fiber-reinforced composites. Compared to glass-fiber-reinforced plastics, natural-fiber-based composite components emit about 30% less CO2 and save about 40% in energy. For this reason, natural fiber composites (NFC) are already being used for selected, non-structural components with low mechanical properties (EU 2015: 120,000 metric tons). However, due to the additional process step required for yarn production, natural fiber fabrics for NFK are very expensive (flax fabric: 16–20 €/kg). Furthermore, the maximum achievable mechanical properties of the components are reduced by fiber ondulation when using staple fiber yarns. Against this backdrop, the goal of the project is to reduce the manufacturing costs for natural-fiber-based fabrics by 25% while simultaneously increasing the mechanical properties of the composite components produced from them by at least 15%. The combination of these two effects makes the use of natural fiber composites in load-bearing structures possible and more attractive. This is particularly important for applications in technical, mechanically active composite components.
The approach to achieving these goals involves developing a process for processing twist-free natural fiber tapes on multiaxial lay-up machines and eliminating the costly spinning process for natural fiber yarns. To this end, the ITA is investigating consolidation and transport mechanisms during the processing of flax fiber tapes and developing a novel feeding device for natural fiber tapes. Based on this technology, biaxial fabrics (+/-45°) with a weight per unit area of 600 g/m² are produced. These multiaxial fabrics are evaluated by the Institute for Polymer Materials and Plastics Technology (PuK) at Clausthal University of Applied Sciences for their drapability and permeability. The impregnation of the fabrics with a duromer matrix and the determination of the resulting technical properties are also carried out at PuK. Building on the new fabric technology and processing techniques, an instrument panel is being manufactured as a demonstration component. The implementation of the produced material in vehicle interiors is being advanced through discussions and coordination with automotive OEMs. Thus, the project can open up a new area of application for natural fibers. The impact on the participating SMEs is reflected in their revenue, which has the potential to increase by at least 4%—or approximately €13.92 million—over the course of two years.