Durobast

The project Durobasts pursued a holistic approach to manufacture natural fiber reinforced composites by combining pretreated natural fibers and bio-based polymers to enable future-oriented production.

Natural fibers have a high potential for a more sustainable and resource-saving production of structural components. The selection of regionally available bast fiber (in particular hemp fibers are cultivated in Germany) in combination with bio-based polymers, e.g. polylactic acid (PLA), enable future-oriented production of natural-fiber-reinforced composites. Moisture absorption in natural fibers is a major challenge that must be overcome for higher market penetration. The project Durobast considered the entire process chain, starting from the selection of suitable natural fibers up to the manufacture of components. A particular focus was on fiber treatment through cavity polymerization for reducing moisture absorption. The hollow natural fibers were impregnated with a low-viscosity monomer, which is then polymerized to form a thermoplastic polymer.

The Leibniz-Institut für Verbundwerkstoffe investigated composite components based on semi-finished products, so-called organo sheets. They were produced with textiles made of pure natural fibers combined with polymer films or powder or alternatively as hybrid fabrics or fabrics made with both natural and polymer fibers. The identification of suitable process temperatures was challenging. Impregnation with the thermoplastic polymer can be facilitated by increasing process temperature, while on the other hand exceeding specific temperatures damages the bast fibers, reducing their strength and toughness. Beyond the optimization of organic sheet production, the characterization of their draping behavior was a focal point of the project. FE-based simulation of thermoforming processes allow optimization of part production while minimizing trial and error experimentation.