Generating active, sustainable contributions to climate protection and prevention of the climate crisis has been an objective of the research activities of the Institute of Textile Machinery and High Performance Material Technology (ITM) at the TU Dresden/Germany for many years. Energy saving, resource efficiency, circular economy and thus active environmental protection are essential drivers for the development of new materials, technologies and machines along the entire textile value-added chain. This is illustrated by the following exemplary research projects of the ITM on selected topics, which are funded by the BMWK, BMBF and DFG.
Material efficiency through low-waste, near-net-shape and load-adapted 2D and 3D reinforcement structures
Material and cost efficiency are essential factors for the development of low-waste biaxial fabrics based on warp-knitting technology for lightweight applications suitable for large-scale production and near-net-shape multiaxial fabrics with locally adjustable, component-specific reinforcing warp yarn density. The production of near-net-shape fabrics enormously reduces the waste in the process chain of composites production. The potential for cost reduction is significant, while maintaining high productivity, thus allowing the realization of new lightweight construction applications, e.g. in electromobility, aviation and renewable energies. The development of a new process for converting warp yarns into weft yarns in the knitting process has also made it possible to produce knitted textile semi-finished products for complex composite components almost without the need for cutting, thus making them significantly more resource-efficient.
Novel load-adapted and near-net-shape woven textile reinforcement structures made of high-performance fibers can be generated with a developed width-adjustable elastomer weaving reed. By means of this weaving reed, locally different warp yarn densities are achievable over the fabric length additionally the warp yarn course within the fabric can be controlled according to force flow paths or the outer contour of a composite component. These developments are therefore important contributions to achieve high material and resource efficiency through maximum utilization of the property potential of the fibers, as well as load-oriented design and preform manufacturing without oversizing.
Multiaxial warp knitting technologies for sustainable textile concrete reinforcements
Compared to conventional construction methods based on steel reinforcement, a textile concrete construction method saves up to 60 % of concrete due to a significant decrease in the required concrete overlap. The CO2 emission per ton of cement – the main component of concrete – amounts to 590 kg and adds up to 8 % of the annual global CO2 emissions for the construction industry. This means that there is an enormous potential for climate protection in this sector that must be further exploited.
The ITM is currently developing textile concrete reinforcements with profiled yarns based on braiding and impregnation forming techniques. The yarn profiling creates an additional form fit with the concrete matrix, thus enabling higher bonding strength between the concrete and the yarn/textile. This allows a reduction of the necessary bonding lengths so that overlapping areas or oversizing of the reinforcement material can be largely avoided. This also increases material efficiency and leads to CO2 savings.
A novel amphibian guiding system made of textile concrete developed at the ITM for use along busy roads combines resource-saving construction methods and high ecological sustainability with nature and species protection. The robust and durable guide system made of carbon fiber-reinforced concrete elements has an amphibian-friendly surface and guides amphibians to road crossings that are safe for them. The design as a textile concrete element saves enormous amounts of concrete (cement), resulting in a decreased CO2 footprint, and is therefore a significant contribution to climate protection as well as to the preservation of biodiversity and global climate protection.
Material efficiency through new forming techniques for 3D semi-finished products
In addition to the direct production of 3D semi-finished products, the forming of plane structures also offers enormous potential for increasing material and resource efficiency. A completely developed new manufacturing process makes it possible to form flat textile semi-finished products directly into complex 3D geometries using elastic 3D tools. This saves 30 % of the reinforcing material that was previously required as a material additive for the forming process. After forming, the reinforcing fibers follow the curvature of the component, which means that the dimensioning of highly stressable FRP components can be carried out in a more resource-efficient manner.
Reprocessing through repair of CFRP structures
A long service life of composite components should be one of the main objectives of development in terms of efficient use of resources, environmental balance and economic efficiency. Nevertheless, or precisely because of this, this also requires solutions for the full repair of these components. Therefore a repair approach was developed in which textile patches are inserted into a repair site that has been locally freed from the matrix. The very defined local matrix degradation is initiated by UV irradiation using semi-conductor oxide catalysis. The further investigation of the basic principles achieved in the project is currently the subject of subsequent projects.
Resource efficiency by use of renewable raw materials
In an interdisciplinary cooperation project, the research institutes Papiertechnische Stiftung (PTS) and ITM are developing innovative, sustainable hybrid paper-textile sandwich materials for lightweight panels with simulation support. They are based on spatially unfolded, fire-resistant paper tapes, which are inserted in a process-integrated and form-fitting manner between 2 woven cover layers. The folding of the paper results in high structural shear and bending stability of the panels. A process developed by the PTS provides the cellulose-based papers with inherent flame-retardant properties (up to DIN 4102 B1) and eliminates the need for separate finishing and coating processes.
Sustainable fibers through recycling and spinning from biopolymers
Based on its research activities, the ITM has gained extensive scientific expertise and a profound understanding of the inter-relationships between carbon fiber properties and their processing behavior, e.g. by yarn formation technology. This is the foundation for the establishment of closed raw material cycles in the composites sector. Concerning the fibers, the ITM considers the entire process chain of industrial yarn formation technology, starting with fiber mixing using the carding process, sliver formation and drawing up to the spinning of hybrid yarns, e.g. from recycled carbon fibers (rCF) and thermoplastic fibers. The rCF yarn structures developed at the ITM can be implemented cost-effectively due to low fiber and manufacturing costs and have the following advantages in terms of climate protection:
• efficiency with mechanical properties in the range of original filaments,
• environmentally friendly due to recycling of fiber waste, and
• energy and resource-saving through efficient recycling.
A long-term reduction in the consumption of primary raw materials requires, among other things, the avoidance of downcycling, the establishment of a complete resource-efficient circular economy and the promotion of products with a long service life. Consequently, the aim of the BMBF research project KuRT/PoCo-rPP together with the project partner "Das Duale System Der Grüne Punkt" is the development of a process concept for the production of sustainable, recycled polypropylene fibers from post-consumer waste. For this purpose, the ITM is developing a melt-spinning process for the production of 100 % recycled multifilament polypropylene fibers using the recyclates provided by the project partner.
The renewable raw material chitin is the world's second most abundant biopolymer and usually a by-product of the food industry. The utilization of chitin for the production of chitosan fibers by developing a sustainable solvent mass spinning process for tailored filament yarns with high performance and functional capabilities is the aim of research activities at the ITM. Chitosan is biocompatible, non-toxic and biodegradable, thus offering very good physiological properties for wide-ranging use in biomedical, dermatological and cosmetic applications. The use of ionic and therefore recyclable solvents allows the sustainable, environmentally friendly spin-coating of chitosan fibers in neutral aqueous coagulation medium without chemically aggressive, environmentally harmful or toxic chemicals.
The development of technologies, processes and materials within the scope of ITM research impressively demonstrates the possibilities in terms of closed material cycles in industrial product development and production. Hence, the work of the ITM provides a significant contribution to environmental protection, resource conservation and sustainability.
The ITM would like to thank the German Federal Ministry of Economics and Climate Protection (BMWK), the German Federal Ministry of Education and Research (BMBF) and the German Research Foundation (DFG) for the financial support of the research projects listed in this article.