Grafting of CNTs onto the surface of PBO fibers at high-density for enhancing interfacial adhesion, mechanical properties and stability of composites.

To improve the interfacial adhesion and mechanical performance of PBO fiber composites, CNTs were uniformly grafted onto them at a high-density. The grafting of CNTs with massive reactive groups can improve the surface wettability and interfacial interaction of PBO fibers with epoxy resin. The IFSS and ILSS values of themodified composites (PBO-CNT-3) increased by 103.09 and 62.73%, respectively. As CNTs can strengthen interfacial regions of the composites, the mechanical properties (hardness and modulus) of the interphase were enhanced significantly. This led to the effective transfer of interfacial load, elimination of stress concentration, and improvement in the structural stability of the composites. As a result, the impact strength of the modified composites (PBO-CNT-3) was up to 103.76 kJ/m (an increase of 56.24%) compared to the original composites. The surface morphology and deformation behavior of the fractured composites indicate that the interfacial failure mode of the composites grafted with CNTs changes from adhesive failure to both cohesive and substrate failure. This strategy of grafting CNTs at a high-density opens a new avenue for the interfacial regulation of structural composites, ultra-capacitor, sensor, and catalytic materials.