Increasing the sustainability of fabric reinforced organo sheets

The project Durobast – durable and resource-saving composite structural components based on newly pre-treated and processed bast fibers (funding reference: 2220NR090C) – pursues the entire value chain of bast fiber-reinforced polymer composites starting with the selection of regionally available bast fibers up to the manufacturing of the final part. Bast fibers, such as hemp or flax fibers, are extracted from the plant stem, can be cultivated in Europe and therefore lead to a reduced CO₂-footprint due to transportation. A newly developed fiber modification aims at the reduction of moisture absorption of the hydrophlic natural fiber.

Research at Leibniz-Institut für Verbundwerkstoffe (IVW) focuses on the manufacturing and processing of natural fiber reinforced organo sheets (NF-OB). Organo sheets are composites of woven fabrics made of hemp or flax fibers that are impregnated with polypropylene or polylactic acid (PLA). Suitable process parameters are investigated to manufacture NF-OB with an optimal property profile. The selection of suitable parameters, especially process temperatures, is challenging due to specific fiber properties. While increasing temperatures facilitate fiber impregnation due to decreasing polymer viscosity, these increases may also lead to degradation of fiber components. The use of bio-based polymers such as PLA may also limit the maximum temperature to prevent polymer degradation. Increases of process pressure, on the other hand, can lead to improved impregnation due to compaction of the textile stack and a reduced air content prior to melting of the polymer. The large variety in diameter of natural fibers may lead to unintentional closing of flow paths within the textile structure and may vary largely between manufactured parts. Inadequate selection of process parameters primarily leads to a reduction in mechanical properties. Fiber degradation may also lead to odor formation, which is of particular concern when considering the use of NF-OB in automotive applications.

Manufacturing of NF-OB with an optimized property profile in continuous hot press processes forms the basis of efficient part manufacturing. Thermoforming together with infrared heating can be used to produce shell-like parts. Optimization of this thermoforming process is suported by FE-simulation to investigate the influence of temperature on stresses within the organo sheet as well as a scheme for fastening the semi-finished product in the transport frame.

Results of the project were reported as part of a scientific presentation at the SAMPE Europe 23 Conference in Madrid, Spain, October 3 - 5.

The project partners at nova-Institut will organize a stakeholder workshop on November 8 as part of the Greener Manufacturing Show in Cologne, Germany. The project consortium will discuss their results with experts from science and industry.

Visit our project homepage for further information: www.durobast.de

The project Durobast is funded by the Federal Ministry of Food and Agriculture on the basis of a decision by the German Bundestag (funding reference: 2220NR090C).