Research in Japan demonstrates novel electrical pulse method for carbon fiber recycling

The recycling of carbon fiber-reinforced polymers (CFRP) remains an ongoing challenge. In a recent study, researchers from Waseda University (Shinjuku, Japan) developed a novel direct discharge electrical pulse method that demonstrated efficient, effective and environmentally friendly separation of CFRP to recover high-quality carbon fibers. This work is expected to pave the way for a more sustainable world.

Conventional recycling methods often 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.

But while this method is lucrative, can we do better? Waseda’s team of researchers — led by professor Chiharu Tokoro from the Department of Creative Science and Engineering, and including Keita Sato, Manabu Inutsuka and Taketoshi Koita — hope to provide an answer to this question with their novel direct discharge electrical pulse method. Findings were published in Scientific Reports in November 2024.

“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,” says Tokoro, explaining the motivation behind the team’s present work. “However, in applications such as lithium-ion batteries, we discovered that direct discharge, which uses 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.”

This 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. 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 technique is more effective for carbon fiber recovery — it preserves relatively longer fibers with higher strength and also precisely separates CFRP into individual fibers without retaining any residual resin on the surface.

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

“Our research findings have numerous applications, pertaining to the recycling of CFRP from spent aircraft components, automotive waste and wind turbine blades,” adds Tokoro. “Thus, the present innovation supports sustainability across industries by enabling efficient resource recovery and reducing environmental impact.”

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).