In the reinforcement of composites, natural fibres are becoming increasingly important as an efficient, sustainable alternative to synthetic high-performance fibres for the lightweight construction industry.

Germany based Fuse has set itself the task of developing high-performance technical applications for bio-based fibre raw materials, taking into account the entire value chain from the raw material in the field to the finished composite product. A project is currently underway to produce a hemp-based alpine ski, which started in January 2023 and will run for three years.

Karl Mayer Technische Textilien GmbH is on board as a partner for the production of non-crimp fabrics. The Fuse hemp tapes are processed into reinforcement textiles on Karl Mayer’s COP MAX 5 multiaxial warp knitting machine for their demanding task in winter sports and the HempSki will be a highlight at the Karl Mayer Group stand at the upcoming Techtextil in Frankfurt am Main.

A sport in and with nature

Skiing combines sport with the experience of nature, all especially when the equipment is made from bio-based materials, Karl Mayer says. There are already innovative biogenic reinforcement materials for composites in the ski sector, but only processed in small batches by ski manufacturers. The HempSki project aims to develop a solution that makes it possible to manufacture skis using materials from renewable raw materials and waste streams on an industrial scale. Companies from Germany and Austria are participating in the project alongside research institutions.

Scoring points ecologically and economically

In order to achieve ski production with an improved environmental balance and a closed material cycle, the ski core is made from waste streams of former ski end products, and the previous prepregs made from glass fibre-reinforced plastics are replaced by bio-based variants. The basis of the environmentally friendly semi-finished products is the hemp fibre-based UD-Tape Fuse HMP, which is impregnated with bio-resin.

Hemp is used as an industrial fibre in the tapes. "Industrial fibre means on the one hand that this fibre can be produced very effectively, i.e. automated in large industrial processes, and on the other hand that the quality of the fibres is always the same in order to guarantee the same properties in the product. A natural product cannot offer this, but there are various ways and means of still being able to deliver consistent quality," says Lovis Kneisel CEO of Fuse GmbH.

Fuse UD tapes have already proven themselves in preliminary tests, particularly as a top layer in sandwich elements. They can be processed either dry by hand lamination or wet as prepreg. While corresponding flax fibre-based sandwich elements are already state of the art, the Fuse HMP UD tapes based on hemp are an innovation. The tapes are available with variable basis weights between 100 and 250 gsm and can be processed into composite components with individual properties.

Fuse's bio-based raw materials come 100% from sustainable regional cultivation in Europe. The supply chain is therefore short, direct and transparent.

A high continuous running length of up to 500 m per roll and short process control through direct surface formation from the fibre also make Fuse more efficient than other natural fibre-based flat semi-finished products on the market.

Processing premiere on the COP MAX 5

For the HempSki project, the Fuse HMP UD tapes were processed into textile reinforcement surfaces on a COP MAX 5. The multiaxial warp knitting machine is designed for the production of multiaxial fabrics from carbon fibre tapes. However, a model has now been used for the first time in the Karl Mayer Technische Textilien technical centre for the use of tapes made from natural fibres.

When the rolls of hemp tape were delivered, application engineer Kay Burkhardt and his team were very excited about the subsequent processing on the COP MAX 5. After just a few running metres, it was clear that the bio-based material runs smoothly and without any loss of speed. The biaxial and triaxial fabrics produced show an even fibre distribution and have the desired basis weights. Kay Burkhardt is delighted with this success.

On the COP MAX 4, the application technology team has already processed continuous flax yarns without any problems. The use of tapes represents a further step towards the use of bio-based composites. "If natural fibre tapes are used instead of yarns, spinning is no longer necessary, the value chain is shorter and therefore more efficient. In addition, shorter and therefore more cost-effective fibres can be used in tapes with unidirectional fibre orientation while maintaining the same performance. The fibre achieves optimum performance due to the lack of yarn twist and the resulting load-oriented alignment," says Kay Burkhardt.

Karl Mayer Technical Textiles continues to support the composites industry with know-how and machine technology on the way to greater efficiency and sustainability.

Further steps

Following the construction of the first skis at the SPURart ski manufactory, production is now being transferred to an industrial scale. A partner from the winter sports industry has already been won. In addition, the HempSki project will further qualify the hemp material as a fibre composite for industrial production. Intensive development work and discussions are already underway in the areas of water sports, wake and surfboards, as well as boat building and automotive.

www.karlmayer.com