Significantly increasing the interfacial adhesion of carbon fiber composites via constructing a synergistic hydrogen bonding network by vacuum filtration

Herein, innovative use of vacuum filtration approach to modify the circumferential surface of structural carbon fiber is proposed for improving the interfacial adhesion of composites by constructing a synergistic hydrogen-bond network on fiber surface via the utilization of carbon nanofibers (CNFs), carbon nanotubes (CNTs) and polyvinyl alcohol (PVA). The obtained hybrid reinforcement presents 123.18 MPa of interfacial shear strength, respectively 105.7% and 52.5% exceeding those of untreated fiber and CNF/CNT grafted fiber. Such dramatic improvement can be mainly assigned to the formation of dense hydrogen bonds among the richer hydroxyl groups of CNFs and PVA, and the active sites of CNTs, leading to larger energy consumption at interphase. Meanwhile, CNF/CNT assembled like the spider's web, which could deflect cracks and give rise to the gradual transition of interfacial modulus. This promotes the stress transfer and avoids the stress concentration. The vacuum filtration belongs to a facile, low-cost and eco-friendly strategy, which has been proven successful in obtaining composites with great interfacial adhesion, opening an advanced way for the surface modification of high-performance fibers.