SMC semi-finished products for structural high-temperature applications based on recycled carbon fibers
Fiber-reinforced polymers based on carbon fibers play a key role in many industries with lightweight construction requirements. Novel SMC semi-finished products enable these fibers to be sensibly recycled and integrated into a material cycle.
This applies primarily to aviation and automotive technology, but increasingly also to the leisure and sports sector. In addition to pure lightweight construction and the familiar economic challenges, ecological lightweight construction with the demands for sustainable solutions and recyclable materials has increasingly come into focus in recent years. This objective can only be achieved for carbon fiber reinforced plastics (CFRP) by consistently pursuing a holistic circular economy. The average annual growth rates in CFRP processing industry are 10 - 13 %. In 2023, CFRP demand is expected to be around 197,000 tons. A waste rate of approx. 30 % is expected in production, which corresponds to a quantity of 66,000 tons of virgin carbon fibers to be recycled or recovered. These consist of about 1/3 production waste and 2/3 end-of-life (EoL) components. These conditions call for a holistic and innovative approach. In current recycling processes, components and fibers are usually shredded and subsequently pyrolyzed. This leads to a shortening of the fibers, which only enables "down-cycling" instead of efficient recycling. In “NeuRecA” joint project, therefore, targeted material development for reuse in new CFRP applications is taking place, both for carbon fiber production waste (offcuts from CF textiles and coil remnants) as well as for recycled and processed carbon fibers from the pyrolysis of end-of-life (EoL) components. This can significantly reduce the environmental footprint of carbon fiber-reinforced components and further increase the attractiveness of the material. Compared to new (virgin) carbon fibers, recycled carbon fibers (rCF) consume approx. 5 - 10 % of the primary energy used. In the course of the project work, the carbon fibers are processed in a pyrolysis procedure. This is a thermal-chemical recycling process under an inert gas atmosphere, in which the matrix is converted into a gas phase and the carbon fibers can be recovered without external damage. The carbon fibers thus recovered are then further processed in a spinning process into a staple fiber yarn and, in combination with a high-temperature epoxy resin system, processed into a sheet molding compound (SMC) semi-finished product. In parallel to the semi-finished product development, extensive analytical tests, such as DSC or TMA, are carried out. In addition, the chemical resistance of the semi-finished product is investigated which is of particular interest for potential applications in aerospace sector.
The Sheet Molding Compound (SMC) process is used for the production and processing of semi-finished products, as it allows a high degree of design freedom combined with economical and efficient manufacturing processes. In combination with an appropriate epoxy resin, SMC semi-finished products based on recycled carbon fibers are thus developed which can be used in structural areas subject to high thermal loads. This represents a first important milestone towards sustainable CFRP composites.
Project partner:Blackwave GmbH
Point of contact Leibniz-Institut für Verbundwerkstoffe GmbH:
Dr.-Ing. Florian Gortner I Telefon: +49 631 2017-439
Stefan Buchalik-Bopp, M.Sc. I Telefon: +49 631 2017-436