Paper Title
Stepped Isostress Method in 3-Point Bending to Predict the Creep Performance Of Graphene Filled Epoxy Nano-Composites

Abstract
With increasing use of epoxy resins as matrix material in composites for high performance and structural applications, knowledge of their time dependent mechanical behavior and long term performance under applied load becomes necessary from the design aspect. Creep tests of polymers are often carried out in this regard. However, the long test time of classical creep tests (103-104 hrs generally) is both time consuming and cost intensive. Hence accelerated creep tests are used to extrapolate the information to the time scale of conventional tests on measurements conducted for much shorter durations. In this work, we demonstrate the use of Stepped Isostress Method (SSM) in 3-point bending mode (unlike the commonly used tensile mode) in a dynamic mechanical analyser (DMA) as a means of accelerated creep measurement of bulk epoxy nano-composites filled with functionalized graphene based fillers. Epoxy resins cured with a polyetheramine based curing agent and filled with graphene oxide and its amine functionalized derivate have been used as test specimens. The tests have been carried out at temperatures of 40oC and 50oC to probe the applicability of this method at temperatures higher than room temperature conditions. Final master curves reveal that the nano-composites show a marginally better creep response in comparison to the neat epoxy reference. This is anticipated to be due to the improved filler-matrix interfacial interactions leading to better load transfer from the matrix to the fillers.