Carboxymethyl cellulose sizing repairs carbon fiber surface defects in epoxy composites

Carbon fiber inevitably generates a large number of defects coupling with the multi-functional groups on its surface during the production process. As a result, these defects will cause stress concentration at the interface, thereby reducing the performance of carbon fiber reinforced polymer composites (CFRPs). In this work, a self-driven method is adopted to repair the surface defects of CFs to improve the interface properties of CFRPs. The surface of CFs is sized by nano-carboxymethyl cellulose (CMC) with multi-functional groups. Due to the existence of multi-functional groups on the surface defects of CFs and the non-polarity of other areas in CFs, CMC can automatically gather at the defects via polar attraction between the multi-functional groups to achieve the self-driven repair. Besides, due to the film-forming properties of CMC, the surface defects will be used as a fixed points to form a tight layer of nanofiber membrane with the multi-functional groups on the surface of CFs. It is found that the repair of CFs surface defects and the introduction of multi-functional groups will synergistically enhance the interface performance of epoxy-based composite. The modification method is environmental benign, which lays a research foundation for improving the interface properties of CFRPs using natural cellulose.