Experimental investigation and modelling of rubber nanoparticle-reinforced epoxy: Temperature and strain-rate effects

The uniaxial compressive behaviours (stress-strain curve and yield stress) of rubber nanoparticle-reinforced epoxy (RNP/epoxy) are studied using the universal testing machine and split-Hopkinson pressure bar over the temperature range of -80 degrees C to +80 degrees C and the strain rate range of 10- 2s- 1 to 103s-1. The experimental results show that the stress-strain curve and yield stress are significantly sensitive to temperature and strain rate under finite deformation. For yield stress analysis, the temperature effect on the RNP/epoxy was more uniform at quasistatic loading, while the softening effect by elevated temperature was dominant at high strain rates and low temperatures, and the hardening effect due to an increase in the strain rate was more pronounced at high temperatures. The simulation results of the unit cell model indicate that the varied mechanical properties of the rubber particles and epoxy matrix at different strain rates and temperatures significantly affect the stress levels of the RNP/epoxy composite. Meanwhile, owing to the presence of rubber nanoparticles, the stress distribution in the epoxy matrix near the particles was extremely non-uniform, leading to matrix damage. These phenomena were confirmed by scanning electron microscopy analysis. Finally, a viscoelastic-viscoplastic constitutive model was established for the compressive behaviour of RNP/epoxy over a wide range of temperatures and strain rates.