PFINZTAL, Germany – As carbon fiber reinforced plastic continues to be a major component of the aircraft, it adds to the need for a sustainable recycling concept. Engineers at the Fraunhofer Institute for Chemical Technology (ICT) have recently developed a process for converting recycled carbon fiber into battery and fuel cell materials.
ICT engineer Elisa Seiler said: "Today, wide-body aircraft consists of more than 50% carbon fiber reinforced plastic (CFRP). "The amount of CFRP recycled materials is huge. For example, Airbus 350 has a total weight of more than 65 tons. In addition to this, other related waste quantities are generated during the production process. " "
Seiler and her colleagues participated in the Graphit 2.0 project, which developed a process for recovering battery and fuel cell materials from recycled carbon fiber. They recently produced a prototype of a bipolar plate.
The purpose of the Graphit 2.0 project is to develop a process that enables recycled carbon fiber to be used as secondary graphite for high value energy storage devices such as redox flow batteries.
In the first part of the project, engineers developed a process for obtaining secondary raw materials from carbon fibers by mechanical and thermal processing. This secondary material is used as a substitute for graphite. In the second part of the project, secondary graphite was tested in a bipolar plate for a redox flow battery.
Seiler said: "Electric drive is now a serious topic in the aviation industry." “Manufacturers can directly perform the recycling of saved values by moving materials from one application to the next.
Seyle pointed out: "Carbon fiber is electrically conductive and suitable as a substitute for natural graphite. Natural graphite is also composed of carbon." “[This] resource-critical raw materials must currently be imported from China at a high cost. Recycling CFRP can also be used in additive manufacturing applications.”
Aircraft manufacturers must comply with EU requirements that have been in effect since 2015 - they require that 85% of the average weight of used cars must be recycled. In some countries, such as Germany, CFRP is prohibited from landfills, and waste incineration plants can refuse to accept such materials.
Seiler and her colleagues developed a way to recover carbon fiber from a plastic matrix. They use microwave radiation to burn a plastic matrix around the fibers. Combustion must be carried out under anaerobic conditions so that the fibers do not burn at temperatures up to 900 ° C
Seiler said: "This is called pyrolysis decomposition." "The advantage of microwave radiation is energy efficiency. The entire oven no longer needs to be heated, only the components themselves need to be heated.
“Our polymer engineers embed recycled fibers into thermoplastic materials,” explains Seiler. This composite has similar properties to graphite and is suitable for the production of bipolar plates.
Seiler claims: "Our prototypes have passed all tests for conductivity, density and corrosion resistance." “We have proven that it is generally feasible to use recycled CFRP fibers to produce bipolar plates for batteries and fuel cells. This shows that recycling is a holistic approach.
Seiler said: "The next step is to describe the characteristics of the bipolar plates in the battery cell network and to study life cycle assessment." “Then we want to adjust the technology so that we can make bipolar plates with the recycled CFRP series.”
