Carbon fiber composite reaches 437°C with nanotube scaffold, clears void threshold

Carbon fiber reinforced polymers are integral to modern aviation, forming the structural core of airframes, satellite buses, and launch vehicles. However, these materials have a glass transition temperature (Tg) that limits their high-temperature performance. Researchers at Pusan National University (PNU) in South Korea have developed a composite that maintains its structural integrity up to 437°C (819°F), utilizing a novel manufacturing process that also addresses void content issues.

The process, Vacuum Assisted Nano-Network Co-Impregnation (VANCI), employs carbon nanotubes (CNTs) as a nanoscale scaffold. When CNTs are co-infiltrated with polyimide resin into a carbon fiber fabric under vacuum, they form an interconnected network. This network constrains the polyimide chains, raising the Tg beyond what is achievable through chemistry alone. This phenomenon, known as the nano-confinement effect, is a recognized mechanism for enhancing polymer performance.

Published in Advanced Composites and Hybrid Materials, the study led by Professor Sung Dong-gi demonstrates significant improvements. The composite achieved a Tg of 437°C, up from 395.6°C in conventional carbon fiber reinforced polymers (CFRP). The void content was reduced to 0.8 percent, well below the aerospace standard of 2 percent, compared to 6.8 percent in traditional polyimide composites.

Standard carbon fiber composites, typically using epoxy matrices, are limited by Tg values of 150–200°C. In high-temperature zones like engine nacelles and hypersonic vehicle skins, these materials are impractical, necessitating heavier alternatives like titanium. Polyimide resins, developed for high-temperature applications, offer a solution but are challenging to process due to high viscosity, which can lead to voids that compromise structural integrity.

The PNU team's VANCI process addresses these issues by combining CNTs and polyimide in a single solution, allowing for simultaneous infiltration. The CNT network forms a dense web that constrains the polyimide chains, raising the Tg and reducing void content. This single-step process simplifies manufacturing, reducing variability and cost compared to multi-step methods.

Beyond thermal performance, the CNT network enhances the composite's functional properties. Electrical conductivity increased twelvefold to 0.85 siemens per meter, and thermal conductivity improved by 85 percent. The wear rate decreased by 51 percent, making the material suitable for applications requiring multifunctional capabilities, such as aircraft lightning protection and thermal management in satellite electronics.

Professor Sung emphasized the process's potential for aerospace and defense applications, highlighting its ability to efficiently manufacture ultra-high-temperature composites. The research, funded by the Ministry of Science and ICT of South Korea and the National Research Foundation of Korea, suggests that nanoconfinement could be a generalizable method for enhancing Tg in various polymer systems, offering a new tool for materials scientists.

The study was published online on July 23, 2026, in Advanced Composites and Hybrid Materials, with contributions from graduate students Kim Song-hee and Kim Da-young, and researchers from the Korea Institute of Materials Science.