In the last Interviews feature, we showcased research on recycling scrap fiber for a more sustainable future for composites. Now we take a look at upcycling scrap prepreg as a team at the M.C. Gill Composites Center at the University of Southern California (USC) did to make the Gazelle™, a composite prosthetic foot made entirely out of scrap carbon fiber/epoxy prepreg that otherwise would be landfilled.
After the project was nominated for the Innovation in Green Composites Design ACE Award at CAMX 2014, Gaurav Nilakantan of the research team described how the foot was created, the benefits of upcycling and commercial potential for the Gazelle.
What motivated this research work on reusing scrap carbon fiber prepreg? Where do you typically obtain scrap prepreg from?
We originally began this research work under a National Science Foundation G8 Funding Initiative on materials efficiency and sustainable manufacturing with thermoset composite prepregs. The reuse and recycling of composite materials were just two of the many thrust areas of this multinational project in collaboration with three other universities in the UK, Canada and Germany, with our M.C. Gill Composites Center at the University of Southern California leading the overall effort. We quickly discovered during our literature search that while there were multiple academic and industrial efforts targeted at recycling cured carbon fiber/epoxy composite structures through various fiber reclamation techniques in the U.S., we could not find any substantive work being conducted on reusing or upcycling uncured scrap prepreg. All of the uncured scrap carbon fiber prepreg was being disposed in landfills. This was confirmed through several conversations we had with the industry, primarily commercial aircraft and new space, such as Boeing, Northrop Grumman, SpaceX and Virgin Galactic, but we even found an example of a NASCAR racing team that disposed their scrap prepreg in landfills. Some estimates place the annual amount of carbon fiber scrap at 29 million pounds in the U.S.
We decided to tackle this issue head-on and come up with an innovative and feasible solution for the industry to responsibly manage their scrap prepreg stream. We foresaw several advantages to doing so. Firstly, it is widely acknowledged that it is only a matter of time before U.S. environmental regulations catch up with the European Union in terms of mandating levels of reuse and recycling and limiting the amount of legal landfilling. There is a huge economic benefit for those companies that quickly position themselves for impending legislation, especially for regulatory compliance and to avoid potential penalties, fees and carbon taxes. Secondly, unlike “recycling,” which is targeted towards end-of-life composites, the issue of “reuse” must be handled “here-and-now” as prepreg scrap is continuously generated. The volume of scrap is also drastically increasing as the aerospace, automotive and sporting industries increasingly turn to composite prepreg materials. While waste disposal fees, typically $0.75 to $3 per pound of scrap and exponentially higher if the waste is considered hazardous, may not affect the bottom line of very large companies, it still represents a loss of revenue as the carbon fiber and uncured resin in the scrap prepreg is still usable. Virgin carbon fiber prepreg material typically costs around $45 per pound. Upcycling of scrap prepreg could help companies recover some of their material and manufacturing costs. Finally, we envision the creation of several new small businesses and associated manufacturing and design jobs downstream from the aerospace and composites industries, focused on upcycling scrap carbon fiber prepreg and developing and marketing various end-products. We believe we have a solution for that too.