Uniform dispersion of the nano fillers in the thermoset resins is usually achieved by ultrasonication method. In the present work, the effect of sonication time on uniform dispersion of 0.05, 0.1, 0.3, 0.5 and 0.7 wt% graphene oxide/epoxy nanocomposites was investigated. For each weight percentage, three sonication times were selected and the compressive properties of the prepared specimens were investigated at high strain rate using Split Hopkinson Pressure Bar and the optimum sonication times were obtained. The experimental results showed that the optimum weight percentage of the graphene oxide was 0.1 wt% at high strain rate. Moreover, the sonication time was found to be considerably effective on mechanical properties enhancement of the composites. For example, for 0.3 wt% GO/ epoxy, the highest compressive strength was obtained for the optimum sonication time which was 120 min. The results also indicated a high rate sensitivity of behavior of the fabricated nanocomposites. The yield stress of the nanocomposites increased from 114 MPa for quasi-static loading to around 203 MPa at high strain rate. Moreover, the energy delivered to the mixture during ultrasonication was computed and a novel diagram was presented to determine the ultrasonication parameters. At the end, the effect of sonication time on mechanical properties of the samples was examined using scanning electron microscopy (SEM)
