ENHANCEMENT OF INTERFACIAL ADHESION IN GLASS FIBER/EPOXY COMPOSITES USING GRAPHENE NANOSHEETS

Glass fiber/graphene multiscale composites were obtained by direct electrophoretic deposition (EPD) of graphene oxide nanosheets (GO) onto glass fibers (GF). Modified Hummer's method and subsequent ultrasonication technique was used to create GO suspension from graphite source. The GO suspension, being a stable aqueous dispersion of graphene oxide in water, was used as a bath for EPD process. The GO, being negatively charged due to liquid oxidation technique, was deposited on glass fibers by placing them in front of an anode. Different voltages were applied up to 10 V/cm under direct current (DC). As reported in Figure 1, electron microscopy characterization of the coated glass fibers revealed a quite uniform coating of GO nanosheets that resulted to completely wrap the glass fibers. The amount of GO deposited on the GF resulted to steadily increase as the voltage applied during the EPD process increased. These hierarchical fibers were aligned within a bicomponent epoxy polymer matrix to create hybrid single-fiber microcomposites. The interfacial adhesion in glass fiber/epoxy composites was evaluated by the single-fiber fragmentation tests. An increase of the interfacial shear strength (ISS) was observed for GO coated glass fibers compared with as-received ones. The increase of ISS values resulted to be proportional to the amount of GO deposited on the GF up to an improvement of a factor 2.18. The observed increase in interlaminar shear strength could be attributed to an improvement of interphase thermo-mechanical properties due to GO coating. Moreover, the nanomodified interphase could provide a better mechanical interlocking between GF and matrix, due to increased surface roughness.