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Combined paper and textile technology opens up new perspectives for lightweight construction

By the year 2050, carbon emissions shall be reduced by 55% as compared to 1990 levels. Urgent action is required to achieve this goal, especially in the energy, industry, buildings, transports and agriculture areas. For this purpose, it is necessary to cut down on fossil fuel use and substitute electric mobility solutions for conventional powertrains. Also, a sustained reduction in energy usage for the manufacture and use of products is indispensable. So new functional materials and lightweight construction technologies, such as in aircraft construction, will allow significant reductions in energy consumption and carbon emissions.

Project title: » “Development of integrally woven paper/textile sandwich structures for lightweight panels” (Hybrid High Performance Paper Weaves – HyPerWeave)

Project period: » 01/05/2021 – 31/10/2023

Project type: » IGF project No. 21856 BR

Research locations: » Papiertechnische Stiftung (PTS), Functional Materials Dept. Dr. Stefan Knohl, Dr. Cornell Wüstner, and Maria Carmesin

» Technical University of Dresden, Institute of Textile Machinery and High Performance Material Technology (ITM), Dr.-Ing Gerald Hoffmann and Michael Vorhof

As well as various metallic lightweight construction materials, there is a wide variety of fibre composites such as glass and carbon-reinforced plastics (CRP) that show a high potential for lightweight construction applications but a very energy-intensive production, especially in case of carbon. So in the light of the goal to reduce carbon emissions across all industries, the use of glass and natural fibres for reinforcement is worthwhile, because a reduction in CO2 emissions by up to 85% in comparison to pure CRP is feasible, depending on the type of component.

In spite of the comparably low fibre rigidities and strengths, the required mechanical properties of the component can be achieved using sandwich construction designs as already common in automobile construction, aviation and building industry. A sandwich composite is formed with two tension-resistant cover layers and a compression and tension-resistant low-density core.

At present, the cores (mostly folded or honeycomb cores) are produced in an expensive and time-consuming process and are bonded by adhesives only. They are highly susceptible to delamination due to critical short-time loads and alternating loads (vibrations), and the load-carrying capacity of the sandwich panel can be minimized over a longer period. Alternative materials, such as textile spacing structures, have an excellent delamination resistance thanks to the fibre-based locking design of the layers. However, said sandwich-style textile structures do not provide the required shearing strength.

Fig. 1: Schematic view of the process steps for producing the HyPerWeave structure with the development priorities of the co-working research institutes [left]; graphical representation of the paper/textile weave [right] ©ITM

So the goal of the project HyPerWeave (Hybrid High Performance Paper Weaves), which is being worked on in cooperation with the Institute for Textile Machines and High-Performance Material Technology (ITM) of TU Dresden, is to specifically develop an economical production process for sustainable high-performance panels based on available technologies (natural-fibre reinforcement, paper sandwich construction, distance weaving). This is made possible by combining the mechanically favourable arrangement of spatially folded paper surfaces with the positive textile-style engagement of all sub-components (see Figure 1).

The final fixation and consolidation of the HyPerWeave panels is a product-specific operation using high-performance materials (thermoplastics, thermosetting resin) or entirely ecological (e.g. starch-based). Within the project, the specific development of the innovative hybrid paper/textile sandwich materials for lightweight panels is guaranteed by a high number of accompanying simulations along the process steps aimed at the desired material properties. The paper is spatially folded thereby imparting a high structural shearing and bending resistance to the future panels.

The material base is made up of new cellulose-based special papers that are incorporated on a fibre basis in between the woven top and bottom layers using a further-developed new weaving method. In terms of flammability and fire protection, PTS is developing a new method for imparting inherent flame-retardant properties to cellulose-based special papers in order to achieve the Class B2 flammability rating according to DIN 4102 or better. Papers are developed by combining various fibrous materials (e.g. pulp and glass), additives (e.g. wet-strength, binding and retention agents), and flame-retardants (solid organic materials on P-N basis) then to be analysed and evaluated under papermaking aspects.

The method is implemented on the basis of a special paper predominantly made of renewable resources (pulp) and a high-performance paper based on mineral fibres (glass). The paper variants such developed must be shaped into strips suitable for weaving, and this requires testing for laser and mechanical processibility (cutting, creasing). ITM is working on a new weaving method in which the innovative papers are spatially folded and woven by warp and weft into a spacing structure such that the top and bottom layers and the fibre-based core are coupled with one another in a positive form-fit design.

Also, a new material feed, shed formation and fabric guide for the weaving process are being developed and implemented in terms of design and technology. All development steps are based on geometric structures ensuring that the paper folding operation is properly adapted to relevant mechanical load scenarios, and use simulations to develop different weave variants. The newly developed special papers (based on pulp fibre) and high-performance papers (based on glass fibre) are used to realise different functional patterns. Finally, the project team will, in consultation with industrial actors, develop two demonstrators suitable for different applications scenarios (furniture construction using special paper, and lightweight panels for aviation using high-performance paper).

In comparison with conventional sandwich structures, the resultant new HyPerWeave panels will have a significantly improved resistance to delamination and a high resistance to damage. The process chain for panel manufacture will be significantly shorter, eliminating the need for subsequent fireproofing and bonding steps.

Thanks to the newly developed special papers made from a pulp and glass composition that can be individually adjusted to a broad spectrum of properties, and thanks to a wide variety of fabric structures, the HyPerWeave panels can be used for a wide range of different applications. The planned development of the paper/textile composite is expected to open up new fields of application in automobile construction (battery compartments, bodies, etc.), aviation (panels, containers, guide elements, etc.), furniture construction (office and shop furniture, etc.) and building industry (flooring, partition walls, etc.). 

Dr. Cornell Wüstner,

cornell.wuestner@ptspaper.de

Maria Carmesin,

maria.carmesin@ptspaper.de