NASA’s Langley Research Center has developed an innovative magnetic and Raman-based method for macroscopic process control during fabrication of carbon-nanotube-based structures. The development of super-strong, lightweight materials based on carbon nanotubes promises new materials with the strength of current carbon composite materials, but at substantially less weight. The development of these new materials is dependent upon nanotube quality, alignment, and load transfer between individual nanotubes in the structure. However, current fabrication process controls are limited to time-consuming microscopy testing at intermittent stages during processing. NASA’s innovative method can be applied during nanotube structure fabrication to obtain real-time feedback on critical processing parameters during fabrication. Moreover, the method is compatible with in-line fabrication processes.
A combination of magnetic and optical methods is applied to characterize the residual catalyst content, nanotube alignment, and load transfer between individual nanotubes during the fabrication process. The techniques used in this method, which have been proven at the micro level, are applied so that scanning and mapping occurs at the macro level. These methods have been successfully used for nondestructive evaluation of large-format carbon nanotube-based structures, primarily yarns and sheets from several inches square to as large as 4 ft. by 8 ft. The new methodology promises to enable high quality and high yields of carbon nanotube-based structural materials for mission critical applications, with an approximately 30% weight reduction over carbon composite materials in applications such as pressure vessels.