Recycling Carbon Fiber: Importance & Process

Carbon fiber is a woven cloth made of crystalline filaments of carbon cured with a polymer, which can be layered and shaped around a mold. It is an ideal material due to its impressive strength-to-weight ratio , meaning it’s very strong, but not heavy. Carbon fiber is five times lighter than steel with an equal elastic modulus, making it a better choice for many applications. Further, it is corrosion-resistant, non-flammable, and non-toxic, properties that make it an ideal material to use in aerospace, medical, construction, and military industries.

Machining Carbon Fiber

Machining Carbon Fiber can be challenging. The layered structure of the carbon fiber material can lead to delamination, uncut fibers, fiber tear-out, uneven tool wear, and poor surface finishes. Luckily, many cutting tool companies, like CoreHog, specially design tooling with different geometries that can help eliminate these manufacturing problems:

• Straight Flute End Mills: Apply all the cutting forces radially, which helps prevent delamination.
• Compression Cutters: Create opposite cutting forces, stabilizing material removal and preventing delamination, fiber pullout, and burrs along the surface.
• Chipbreaker Cutters: Shear the fibers and shorten the chips, preventing fiber buildup around the cutter.
• Diamond Cut End Mills: Utilize both left-hand and right-hand flutes to break up and shear through the fibers, ideal for roughing and profiling carbon fiber.

Explore CoreHog’s Wide Offering of Composite-Laminate Cutters, each specially engineered to cut difficult-to-machine laminate materials like carbon fiber.

Common Carbon Fiber Applications

In the aerospace industry, carbon fiber is used in plane structures to replace alloys, creating lighter planes and thus, reducing fuel consumption. Recreational sports also utilize carbon fiber to decrease weight. It is often seen as a leading material in skis, bikes, and tennis rackets, as the lighter weight can help improve performance. In professional sports leagues like Formula 1 and NASCAR, carbon fiber has grown in prevalence in recent years. Another advantageous quality of carbon fiber is its suitability in X-ray machines, allowing imaging to pass through without interruption, making it useful in many medical devices and implants.

Recycling Carbon Fiber

Why is Recycling Carbon Fiber Difficult?

Carbon fiber sheets require a significant amount of energy to produce. These large sheets are then cut down to the part size needed, and the excess material is often discarded, increasing waste production. This material is not biodegradable and is typically sent to a landfill where it will remain permanently. Further complicating recycling, carbon fiber is built to hold its shape and strength and cannot be melted down and reshaped like many plastics. When recycled, its properties are heavily degraded, rendering it useless for applications that experience heavy forces or loads.

How is Carbon Fiber Recycled?

Solvolysis

Solvolysis uses a chemical solvent to break down the polymer encasing the carbon fiber cloth. The waste carbon fiber is shredded into smaller pieces, increasing the surface area. The solvent, chosen based on the polymers used in the carbon fiber, breaks down the polymer chains, separating the carbon fiber from the polymer. Techniques like centrifugation are used to separate the substances. The carbon fiber can be further purified to restore its properties and then combined with virgin fibers to create new fabric or used by itself. This process enables the recovery of carbon fiber without sacrificing material properties.

Pyrolysis

Pyrolytic utilizes heat to break down the polymer encasing the carbon fiber cloth. The waste carbon fiber is shredded into smaller pieces and then heated in a controlled environment with limited or no oxygen. At high temperatures, the polymer undergoes thermal decomposition, producing gases, vapors, and char. The gases and vapors can be used as an energy source or further processed, while the char, which is carbon fiber and any original additives, is purified to ensure mechanical properties are maintained. The resulting carbon fiber can be used alone or combined with virgin fibers. Pyrolysis is effective for high-quality fiber recovery and energy recovery from gas byproducts.

Carbon Fiber Considerations

As we innovate with new technology, it is important to consider its impact on our planet. Carbon fiber is an amazing material that can improve many aspects across industries; however, the waste generated is not going anywhere but a landfill. Many companies are investing in producing high-quality recycled carbon fiber. With a shift in focus to designing closed-loop systems for composite materials, the future looks bright.

Sarah Wasson

Sarah Wasson works as a technical sales associate for Harvey Performance Company, focusing on the CoreHog brand of custom composite tooling for the aerospace industry. She graduated in May of 2023 from the University of Vermont with a Bachelor of Science in Mechanical Engineering.