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Inspired by the application of nano‐fillers in composite materials, well‐dispersed aramid nanofibers (ANFs) were prepared and added into the epoxy resin (EP) to improve the toughness and tenacity properties of the ANF/EP composites. The composites were characterized by mechanical property test, surface analysis, thermodynamic property analysis, and contact angle. Results showed that when the EP was added with 0.15 wt% ANF, the tensile strength, bending strength, and impact strength are increased by 28.2%, 81.9%, and 81.8% compared with pure EP, respectively. The thermal stability and infiltration of the composites are improved. The interlaminar shear strength and interfacial shear strength of the aramid fiber were increased by 53.1% and 92.7% compared with the not reinforced EP, demonstrating that the epoxy reinforced with ANF is also beneficial for improving the interfacial bonding strength of aramid fiber and EP. The mechanism of the epoxy reinforcement by ANF and the interface enhancements showed that the ANF could cause several crack bridges and strong hydrogen bond interaction interface. [ABSTRACT FROM AUTHOR]

In this work, the layer-by-layer self-assembly technology was used to modify aramid fibers (AFs) to improve the interfacial adhesion to epoxy matrix. By virtue of the facile layer-by-layer self-assembly technique, poly(l-3,4-Dihydroxyphenylalanine) (l-PDOPA) was successfully coated on the surface of AFs, leading to the formation of AFs with controllable layers (nL-AF). Then, a hydroxyl functionalized silane coupling agent (KH550) was grafted on the surface of l-PDOPA coated AFs. The properties such as microstructure and surface morphology of AFs before and after modification were characterized by FTIR, XPS and FE-SEM. The results confirmed that l-PDOPA and KH550 were successfully introduced into the surface of AFs by electrostatic adsorption. The interfacial properties of AFs reinforced epoxy resin composites before and after coating were characterized by interfacial shear strength (IFSS), interlaminar shear strength (ILSS) and FE-SEM, and the results show that the interfacial adhesion properties of the modified fiber/epoxy resin composites were greatly improved. [ABSTRACT FROM AUTHOR]