TuFF Technology: Innovative Recycling Method for Carbon Fiber Composites

Researchers at the University of Delaware, in collaboration with Composites Automation LLC, have developed a groundbreaking method to recycle carbon fiber composites (CFCs) using Tailorable Universal Feedstock for Forming (TuFF) technology. This new approach addresses the challenges of maintaining the mechanical properties of recycled carbon fibers, enabling the production of high-performance composites from recycled materials.

Carbon fiber composites are known for their strength and lightweight properties, making them ideal for industries like automotive, wind energy, and aviation. As demand for carbon fibers increases, so does the need to manage the growing volume of composite waste. Traditional recycling methods often degrade fiber quality, resulting in lower-performance materials. TuFF technology offers a promising solution by ensuring that recycled fibers are highly aligned, preserving their mechanical integrity.

Tackling Fiber Recovery and Conversion Challenges

The researchers focused on two primary challenges: recovering carbon fibers without losing their properties and converting these fibers into high-performance composites. They employed a solvolysis process to recycle short carbon fibers, followed by a crucial cleaning step to remove any residue that could hinder fiber alignment and dispersion. The residue removal is essential for producing high-quality composites. The cleaned fibers were then processed using TuFF technology, creating composites with a high fiber volume fraction (~50%) and retaining their excellent mechanical properties. This method ensures that the recycled fibers maintain their strength and integrity, making them suitable for various applications.

Comparative Fiber Strength Testing

To evaluate the effectiveness of their method, the researchers conducted a series of tests comparing recycled fibers with virgin carbon fibers. The results showed minimal degradation in the strength of the recycled fibers and no significant impact on the adhesion between the fibers and the resin. This success was achieved through careful analysis and optimization of the cleaning process. The team used non-isothermal thermogravimetric analysis (TGA) to determine the optimal conditions for cleaning the fibers, ensuring the removal of polymer residue without damaging the fibers. The cleaned recycled fibers (referred to as cCF) were then used to create TuFF sheets, which were assessed for their fiber alignment and mechanical properties. The TuFF sheets made from both virgin and recycled fibers exhibited excellent alignment and low porosity, which are crucial for maintaining high performance in structural applications.

Method to Ensure Effective Fiber Recycling

The comprehensive method developed by the team involves multiple steps. Initially, they processed the recycled fibers through a solvolysis procedure conducted by Vartega, a key US supplier of recycled carbon fibers. Following this, they implemented a pyrolytic cleaning step under an inert environment to eliminate any residue left from the solvolysis process. This step was critical in ensuring that the fibers could be well-dispersed and aligned in the TuFF process. The TuFF sheets produced from these cleaned recycled fibers were then laminated with epoxy resin and processed in an autoclave to create composite panels. These panels were evaluated for their microstructural quality and mechanical properties, revealing good alignment, low porosity, and impressive mechanical performance. This rigorous approach ensures that the recycled fibers can be effectively reused without compromising their quality.

TuFF Technology's Structural Application Potential

Mechanical testing demonstrated that TuFF composites made from recycled fibers retained their stiffness, though their strength was slightly reduced compared to those made from virgin fibers. Despite this slight reduction, the properties of the recycled fiber composites were significantly better than those typically reported for short, recycled carbon fiber composites. This demonstrates the potential of TuFF technology to produce high-quality recycled carbon fiber composites suitable for structural applications.

The researchers found that the TuFF process, combined with an effective fiber cleaning method, can produce recycled carbon fiber composites with mechanical properties close to those of virgin composites. This approach not only helps manage the increasing volume of composite waste but also addresses the supply deficit of virgin carbon fibers. The findings highlight the importance of fiber surface quality and proper cleaning in achieving high-performance recycled composites. This method offers a sustainable and economically viable solution for the composites industry, potentially leading to significant advancements in recycling carbon fiber composites.