Carbon fiber-reinforced polymers (CFRPs) are widely utilized in the aerospace, automotive, and sporting goods sectors. Nevertheless, their recycling presents a considerable challenge. A recent investigation conducted by researchers at Waseda University introduced an innovative method using direct discharge electrical pulses for the effective, efficient, and eco-friendly separation of CFRPs, allowing for the recovery of high-grade carbon fibers. This research is poised to contribute to a more sustainable future.
As the world swiftly advances towards modernization, carbon fiber-reinforced polymers (CFRPs) are crucially enabling technological and industrial advancements. These composite materials are not only lightweight but also exceptionally strong, making them suitable for various applications such as aviation, automotive industries, wind energy production, and sporting goods.
However, the recycling of CFRPs is a significant hurdle, with waste management emerging as an urgent concern. Traditional recycling approaches often involve high-temperature processing or chemical treatments, leading to substantial environmental repercussions and increased costs. Additionally, recovering high-quality carbon fibers has proven difficult. In this context, electrohydraulic fragmentation has emerged as a viable solution, where powerful shockwave impulses from high-voltage discharge plasmas are utilized to separate different materials at their interfaces.
Although this method shows promise, can improvement be achieved? To explore this question, a group of researchers from Waseda University, guided by Professor Chiharu Tokoro from the Department of Creative Science and Engineering, including Keita Sato, Manabu Inutsuka, and Taketoshi Koita, devised a new direct discharge electrical pulse technique for enhancing CFRP recycling. Their results were published in the journal Scientific Reports on November 30, 2024.
Tokoro explains the motivation for their current research, stating, “In our previous studies, we had developed expertise in generating shock waves in water through electrical pulse phenomena to effectively fragment materials that are hard to process. However, in the case of lithium-ion batteries, we found that direct discharge, which takes advantage of Joule heating and the vapor expansion of the material, is a more effective method for achieving high-efficiency separation than relying on shock waves. We now want to apply this technique to CFRPs, believing it could lead to more efficient separation than existing methods.”
The direct discharge electrical pulse method capitalizes on Joule heating, thermal stress, and the expansion force resulting from plasma creation, eliminating the need for high temperatures or chemicals. The researchers benchmarked this approach against electrohydraulic fragmentation by analyzing various physical properties of the retrieved carbon fibers, such as length, tensile strength, resin adhesion, structural integrity, and energy efficiency related to fiber separation. Their results indicated that this new method is superior for carbon fiber recovery. It maintains relatively longer and stronger fibers while effectively separating CFRPs into individual fibers without leaving any residual resin.
Moreover, the direct discharge technique enhances energy efficiency by a minimum of tenfold compared to conventional methods, while also lowering environmental impact and promoting better resource utilization.
Consequently, this innovation is expected to accelerate the recycling of CFRPs, making a significant contribution toward building a sustainable society. According to Tokoro, “Our research findings have wide-ranging applications, particularly in recycling CFRPs from retired aircraft parts, automotive waste, and wind turbine blades. Thus, the current innovation fosters sustainability across various industries by facilitating efficient resource recovery and minimizing ecological footprint.”
In summary, this research is anticipated to advance the United Nations Sustainable Development Goals pertaining to Industry, Innovation and Infrastructure (SDG 9), as well as Responsible Consumption and Production (SDG 12).
