"Biosheets" for vehicle construction: Ilmenau doctoral student awarded for research into sustainable lightweight construction

When it comes to sustainability in transportation, it is not only the further development of alternative drive technologies beyond fossil fuels that is currently playing a major role in research. Scientists are also working on resource-saving solutions in vehicle construction itself. For example, fiber-plastic composites, known as organic sheets, have now established themselves as semi-finished products for lightweight construction in the mobility sector. Not only are they very easy to shape, but due to their low density they are also only around half as heavy as conventional metal constructions. Therefore, their use, for example for interior and structural components in cars, commercial vehicles, aviation or public transport, saves resources and energy. Nevertheless, they still generate a considerable amount of waste, as they are currently mostly made from synthetic fibers such as glass fibers and standard plastics such as polyamide (PA) or polypropylene (PP).

A sustainable alternative for lightweight construction could be composites made from natural fibers with bioplastics. But there are currently still a few hurdles to overcome when processing them: "For example, natural fibers are less heat-stable and, unlike synthetic fibers such as glass or carbon fibers, are typically unsized and contaminated with dust, which makes it difficult to bond them with the plastic," explains Maximilian Lang. The research assistant at the Plastics Technology Group headed by Prof. Florian Puch addressed these challenges in his master's thesis at the Thüringer Innovationszentrum Mobilität (ThIMo) at Ilmenau University of Technology.

Composite of flax fibers and the bioplastic polylactic acid (PLA)

Which natural fibers and bioplastics are best suited to producing completely bio-based organic sheets, i.e. sheets made from natural raw materials? Which manufacturing processes and impregnation mechanisms are suitable? And what influence do various manufacturing parameters such as the processing temperature, the process pressure and the time spent impregnating the natural fibers have on the quality of the composites? With these questions in mind, Maximilian Lang examined composites made from flax fibers and the bioplastic polylactic acid (PLA) for their fiber and pore content and their mechanical properties.

"In our investigations, we found that the impregnation cannot be controlled as well as with composites made from glass fibers and PP. When we increased the process pressure, the mechanical properties deteriorated, i.e. the resulting composites were less elastic and tensile - presumably because the fibers were damaged in the process. As we could not increase the temperature and pressure indefinitely, we had to take additional measures to increase the impregnation time, for example by using a so-called flatbed laminating system. This resulted in a defined processing window for organic sheets made from flax fibers."

For his research, Maximilian Lang has now been awarded the Sustainability Prize by the VDI Plastics Technology Division for the special quality of his investigations, the scientific excellence of his work and the economic significance of the results.

The award is endowed with prize money of 1,000 euros and was presented to Maximilian Lang on April 24, 2024 at the VDI Annual Injection Moulding Conference in Wiesbaden.