Scientists show how deep‑freezing sticky carbon-fiber waste can stop the material from clumping together, allowing manufacturers to remold aerospace scraps into reliable composite components.
Carbon fiber–reinforced polymers (CFRPs) are key materials in the aerospace industry, used to make aircraft lighter and more efficient—but producing them generates a significant amount of leftover prepreg offcuts. These scraps still contain high‑value carbon fibers embedded in uncured epoxy, yet repurposing them isn’t straightforward. Fresh prepreg is intentionally tacky, which causes platelets to clump together when repurposed and can lead to uneven packing and weaker composites.
A recent study published in ACS Applied Polymer Materials demonstrates an alternative approach to handling this issue, which involves cooling prepreg offcuts to cryogenic temperatures before molding them into short‑fiber composites. Watch how they did it in the latest Headline Science video:
Cooling instead of curing
One common way to reduce tack is to thermally age the prepreg before processing. While effective at making the material less sticky, this comes with a trade‑off: heating partially cures the epoxy, which can limit flow during consolidation and reduce bonding between platelets. In this work, the researchers compared the traditional aging approach with a simple cryogenic method: cutting prepreg into small platelets, immersing them in liquid nitrogen, and molding them while still cold.
At −196 °C, the epoxy temporarily behaves like a rigid solid with essentially no viscous deformation. Loop tack tests showed that cryogenically cooled prepreg was just as non‑sticky as prepreg that had been thermally aged for more than 50 minutes.
Impact on final composite performance
When the cryogenically cooled platelets were molded, the resulting composites were strong and stiff, essentially matching the performance of composites made from untreated prepreg. Even without tack, the cold platelets flowed and packed evenly enough to produce low‑porosity parts with high fiber content.
The thermally aged prepreg told a different story. As the aging time increased, the resin continued to cure, reducing how well the platelets could pack and bond. This led to more voids, fewer fibers in the final part, and noticeably lower mechanical performance. After 70 minutes of aging, both strength and stiffness had dropped well below the levels achieved with either untreated or cryogenically cooled prepreg.
The findings suggest that cryogenic processing may offer a practical route for upcycling prepreg waste without sacrificing performance. By temporarily eliminating tack without advancing the cure state, manufacturers may be able to mix and mold waste prepreg more effectively, helping reduce the overall footprint of composite production.
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Video credits:
Written, produced, and edited by Vangie Koonce
Narrated and hosted by Anne Hylden
Series produced by Vangie Koonce, Anne Hylden, Andrew Sobey, Janali Thompson, Kerri Jansen, and Jefferson Beck
Executive produced by Matthew Radcliff
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