Non-destructive modification of aramid fiber by building nanoscale-coating solution to enhance the interfacial adhesion properties of the fiber-reinforced composites

The poor interfacial adhesion between the aramid fiber (AF) and the matrix limits the application of the final composites. In this study, a novel coating method was adopted to modify AF Through metallization/grafting reaction, the copolymer synthesized by the low-temperature poly-condensation of p-phenylenediamine (PPDA), 4,4′-diaminodiphenyl ether (ODA) and terephthaloyl dichloride (TPC), was added into the dimethyl sulfoxide/sodium hydride (DMSO/NaH) solution, and a nano AF solution was obtained. Then epoxy groups were introduced to the amide bond by grafting Epichlorohydrin (ECH). By further grafting on Poly (propylene glycol) bis (2-aminopropyl ether) (PEA), more functional groups were introduced, which could increase the polarity of the fiber and the interfacial adhesion of the composites. The results show that not only the interfacial shear strength (IFSS) and the flexural strength of the aramid-reinforced composites has a significant increase compared with the untreated fibers, but the modification still maintains the mechanical properties of the fiber, indicating that building nanoscale coating solution is a very effective method to achieve non-destructive modification to ehance its interfacial adhesion with epoxy resin.