Characterization and modelling of bisphenol-a type epoxy polymer over a wide range of rates and temperatures

Abstract

Epoxy resins are employed in many engineering applications in which mechanical properties at different strain rates and temperatures must be quantified for effective use. It is known that these properties are related through the principle of time-temperature equivalence. In this paper, the application of this equivalence is explored in detail, at both small and large strains, and used as part of a strategy for calibrating a constitutive model that can reproduce the stress-strain behaviour in different mechanical conditions. In order to achieve this, quasi-static compression experiments were performed at temperatures from −40 to +40 °C in a screw-driven load frame; room temperature rate dependent experiments were performed from 0.0005 to 6300 s−1 using a screw-driven load frame, hydraulic compression system and Split Hopkinson Pressure Bar apparatus. Dynamic mechanical analysis and differential scanning calorimetry were also performed. A three-network (TN) polymer model was fit to the mechanical behaviour up to a strain of 0.5. This model, combined with time-temperature based mappings gave a good understanding of the thermomechanical behaviour of the material, and also demonstrates an approach that can be used for a wide range of polymers.