Development of a novel process chain for the direct production of NFPP tapes

Natural fiber reinforced polymer composites (NFRPC) have been used in the European automotive industry for decades and are mainly processed into semi-structural components such as door panels ( see Figure 1), roof stiffeners and backrests. Here, the fibers are usually present as needled nonwovens and are combined with thermoplastic but sometimes also thermoset matrix systems. The specific mechanical properties of NFRPC are in some cases as good as those of glass fiber-reinforced polymer composites (GFRPC) but do not always fully attain their level. Nevertheless, they have great substitution potential and can already partially replace conventional expensive plastics as well as GFRPC structures today. Flax, hemp and kenaf are mostly used for the production of LFRP semi-finished products.

Compared to conventional reinforcing fibers such as E-glass, natural fibers have the advantage of significantly lower density (ρ_NF ≈ 1.5 g/cm³; ρ_GF ≈ 2.5 g/cm³) and thus outstanding lightweight properties. Furthermore, NFRPC are used due to their good mechanical properties, environmental compatibility, CO₂-neutral energy footprint, good crash and damping behavior and high dimensional stability.

Polypropylene (PP) is usually used as the thermoplastic matrix. In addition to its monetary advantages, PP has a very low density (~ 0.9 g/cm³), excellent processing properties, good mechanical performance and high impact strength.

In a joint project, Leibniz-Institut für Verbundwerkstoffe (IVW) and Kaiserslautern University of Applied Sciences - Pirmasens site (HS) - are researching the direct production of natural fiber tapes in combination with thermoplastic matrix. The aim of the research is to develop an alternative direct, cost-effective and efficient process for the production of unidirectionally oriented NFRPC semi-finished products, thus saving expensive and time-consuming process steps. At the beginning of the process, natural fibers and PP staple fibers are opened, mixed, homogenized by means of carding and processed into a fiber web. This is then merged to form a narrow strand and processed into a tape by means of a testing rig. In this tape, the fibers are aligned in the longitudinal direction of the tape and can then be laid down to form test specimen plates by means of a manual tapelayer (see Fig. 2). In the further progress of the project, the impregnation and depositing process will be optimized, mechanical parameters will be determined and tapes will be used for local reinforcement of components.

Kontakt:

Dr.-Ing. Florian Gortner
Postdoc Press & Joining Technologies
Email: florian.gortner@ivw.uni-kl.de
Phone: +49 631 2017 439

Martin Detzel, M.Sc.
Scientific Staff Press & Joining Technologies
Email: martin.detzel@ivw.uni-kl.de
Phone: +49 631 2017 164