An Analysis of Mechanical and Viscoelastic Behaviour of Nano-SiO2 Dispersed Epoxy Composites

Abstract

The influence of SiO2 nanoparticles dispersion on mechanical and viscoelastic properties of SiO2/epoxy nanocomposites was investigated. In order to develop SiO2/epoxy nanocomposites, SiO2 nanoparticles (≈15 nm) were dispersed in the epoxy resin through ultrasonic mixing. Dynamic mechanical analysis, tensile and fracture tests were performed as per ASTM standards to determine the viscoelastic and mechanical properties. A significant enhancement in viscoelastic, fracture and tensile behaviour was observed in the prepared nanocomposites. With the dispersion of SiO2 nanoparticles in epoxy resin, the value of UTS increases from 34.5 MPa (pristine epoxy) to 49 MPa for 4 wt.% SiO2/epoxy nanocomposite. The average value of fracture toughness (K1C) and fracture energy (G1C) for the pristine epoxy was measured to be 1.09 MN/m3/2 and 2.76 kJ/m2 respectively. However, maximum K1C and G1C were found to be 2.89 MN/m3/2 and 11.54 kJ/m2 respectively for 4 wt.% SiO2 nanoparticles dispersion. The maximum increase in the ultimate tensile strength, toughness, K1C and G1C are observed to be 44%, 144%, 165% and 318% respectively in comparison to pristine epoxy. At room temperature, 5 wt.% SiO2/epoxy nanocomposites have showed maximum increment of about 17% in the storage modulus. The glass transition temperature was found to increase from 62 °C (for pristine epoxy) to 70 °C (for 4 wt.% SiO2/epoxy nanocomposites) whereas, glass transition temperature values start decreasing above 4 wt.% SiO2 nanoparticles dispersion due to the obstruction in cross-linking of polymeric chains. The possible changes in the local structure of epoxy matrix are also indicated by the increase in Tg in ultrasonically processed SiO2/epoxy nanocomposites. Numerical and finite element models were applied to predict Young’s modulus of prepared SiO2/epoxy nanocomposites. The experimental results are in good agreement with the finite element model.