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Nanoindentation measurements of fumed silica epoxy reinforced nanocomposites

Nanoindentation testing is used in this paper in order to investigate the mechanical properties of specimens with varying weight percentage of fumed silica using a low-viscosity liquid epoxy resin as a matrix. Controversial results are reported in the literature regarding the elastic modulus of fumed silica epoxy nanocomposites using conventional tensile tests, thereby there is much scope in investigating comparatively such systems in a nanometer scale. The results show that the hardness and modulus of the nanocomposites steadily decrease with increasing fumed silica content which was attributed to the severe tendency for cluster formation as studied by optical microscope and scanning electron microscope analysis. The variations in elastic modulus as measured using the nanoindentation testing technique revealed small differences from the tensile test data. A material-depending calibration procedure has been used by utilising the epoxy elastic modulus as measured by the tensile tests in order to account for the indentation inherent uncertainties in the tip shape calibration. The results demonstrate that the nanoindentation testing technique is an effective mechanical testing method for epoxy nanocomposites when an appropriate calibration procedure is followed.