Multilayer Graphene Sheets and Carbon Nanotubes as Electroconductive Coatings of Glass Fibers for Hierarchical Polymer Composites

Carbon nanostructures are used to coat engineering fibers to render electrical conductivity to smart polymer composites for applications such as self-sensing, actuation, deicing, and self-healing. Despite their great potential and wide use, specific metrics for assessing quality control of the air-spraying method used to coat the fibers are still missing. Dedicated studies comparing the advantages and disadvantages of using carbon nanotubes or multilayer graphene sheets also remain scarce and controversial. In this study, glass fiber weaves are coated with either multilayer graphene sheets or with carbon nanotubes using the air-spraying method. Key air-spraying parameters such as volumetric flow rate, spot size, and areal density are proposed as quality control metrics and systematically characterized. The resulting coatings were further evaluated for thickness, structural damage assessment through Raman spectroscopy, electrical resistance distribution on the fiber, and adhesion to the fiber surface. The findings indicate that carbon nanotube coatings produced more uniform, more densely packed, and more efficient electroconductive coatings with higher adhesion to the glass fibers at less weight content. They also require less energy density during the dispersion process to produce a uniform coating. In contrast, multilayer graphene sheets required four times more material to achieve coatings with similar or slightly lower electrical resistance distribution. These coatings were integrated into laminated polymer composites to fabricate smart composites with damage self-sensing capabilities. Both materials exhibited high sensitivity to damage detection and localization.