Researchers developed a novel electrical pulse method for carbon fiber recycling enhancing efficiency and sustainability

The world is hurtling rapidly towards a developed future, and carbon fiber-reinforced polymers (CFRPs) play a key role in enabling technological and industrial progress. These composite materials are lightweight and highly strong, making them desirable for applications in various fields, including aviation, aerospace, automotive, wind power generation, and sports equipment.

However, recycling CFRPs presents a significant challenge, with waste management being a pressing issue. Conventional recycling methods require high-temperature heating or chemical treatments, which result in high environmental impact and elevated costs. Moreover, it has been a challenge to recover high-quality carbon fibers. In this regard, electrohydraulic fragmentation has been proposed as a promising option. In this technique, intensive shockwave impulses generated by high-voltage discharge plasmas are applied along the interfaces of different materials to separate the various components.

While this method is lucrative, can we do better? Answering this question, a team of researchers from Waseda University, led by Professor Chiharu Tokoro from the Department of Creative Science and Engineering, and including Keita Sato, Manabu Inutsuka, and Taketoshi Koita, has come up with a novel direct discharge electrical pulse method for efficiently recycling CFRPs. Their findings have been published in the journal Scientific Reports on November 30, 2024.

Tokoro talks about the motivation behind their present work, stating: “In our previous studies, we had already established research expertise in generating shock waves in water using electrical pulse phenomena to efficiently fragment difficult-to-process materials. However, in applications such as lithium-ion batteries, we discovered that direct discharge, which utilizes Joule heating and vapor expansion of the material itself, is more effective for high-efficiency separation than relying on shock waves. We now apply this approach to CFRP, hypothesizing that it could achieve more efficient separation compared to current methods.”

The direct discharge electrical pulse technique leverages Joule heat generation, thermal stress generation, and expansion force due to plasma generation, foregoing the need for heating or chemicals. The researchers compared this method with electrohydraulic fragmentation by examining the corresponding physical properties of the recovered carbon fibers, including length, tensile strength, resin adhesion, and structural degradation, as well as the energy efficiency in terms of fiber separation. They found that their new technique is more effective for carbon fiber recovery. It preserves relatively longer fibers with higher strength and also precisely separates CFRPs into individual fibers without retaining any residual resin on the surface.

Furthermore, the direct discharge approach improves energy efficiency by a factor of at least 10 compared to traditional alternatives, while reducing environmental impact and promoting resource utilization.

Therefore, this technology is anticipated to accelerate CFRP recycling, contributing significantly to the development of a sustainable society. According to Tokoro, "Our research findings have numerous applications, pertaining to the recycling of CFRPs from spent aircraft components, automotive waste, and wind turbine blades. Thus, the present innovation supports sustainability across industries by enabling efficient resource recovery and reducing environmental impact.”

Overall, this work is expected to further the United Nations Sustainable Development Goals of Industry, Innovation and Infrastructure (SDG 9) and Responsible Consumption and Production (SDG 12).
Reference

Authors: Chiharu Tokoro^1,2, Keita Sato¹, Manabu Inutsuka³, and Taketoshi Koita¹
Title of original paper: Efficient recovery of carbon fibers from carbon fiber-reinforced polymers using direct discharge electrical pulses
Journal: Scientific Reports
DOI: https://doi.org/10.1038/s41598-024-76955-0
Affiliations:
¹Department of Creative Science and Engineering, Waseda University, Japan
²Faculty of Engineering, The University of Tokyo, Japan
³Waseda Center for a Carbon Neutral Society, Waseda University, Japan

About Waseda University
Located in the heart of Tokyo, Waseda University is a leading private research university that has long been dedicated to academic excellence, innovative research, and civic engagement at both the local and global levels since 1882. The University has produced many changemakers in its history, including nine prime ministers and many leaders in business, science and technology, literature, sports, and film. The University has strong collaborations with overseas research institutions and is committed to advancing cutting-edge research and developing leaders who can contribute to the resolution of complex global social issues. The University has set a target of achieving a zero-carbon campus by 2032, which is in line with the Sustainable Development Goals (SDGs) adopted by the United Nations in 2015.
To learn more about Waseda University, visit https://www.waseda.jp/top/en.

About Professor Chiharu Tokoro from Waseda University
Chiharu Tokoro has been a Professor at the Department of Creative Science and Engineering at Waseda University, Japan, since 2015, and is also associated with the Faculty of Engineering, The University of Tokyo. She received a B.E. in Resources Engineering from Waseda University in 1998, and an M.E. and Ph.D. in Geosystems Engineering from The University of Tokyo in 2000 and 2003, respectively. Her research interests include resource separation technologies for the realization of a circular economy, environmental remediation and purification technologies for resources, and powder simulation technology for energy-saving process development. She has published over 200 research articles, which have been cited over 2,000 times.