CNT coating and anchoring beads enhance interfacial adhesion in fiber composites

The fiber-matrix interface is a critical component in fiber composites, affecting both their strength and toughness. In this study, glass fibers were treated with thin coating of CNT bundles, creating a strong scaffold using evaporation-driven deposition. Epoxy beads were applied to the coating, implementing the Plateau-Rayleigh liquid instability phenomenon. The coated and beaded fibers were embedded in epoxy matrix and subjected to pullout tests, yielding a significant increase of 140% in strength and 400% in toughness, compared to untreated fibers. Electron microscopy and 3D micro-CT imaging elucidated the improvement mechanisms, including strengthening and toughening of the fiber-matrix interphase by the scaffold and anchoring of the epoxy beads. Composites reinforced by such fibers should potentially lead to significant enhancement of simultaneously both strength and toughness. Similarly, the mechanical and electrical properties of flexible functional composites can be enhanced by weaving the coated and beaded fibers into a smart fabric.