The effects of shape and mass fraction of nano-SiO2 on thermomechanical properties of nano-SiO2/DGEBA/MTHPA composites: A molecular dynamics simulation study

The doping of nano-SiO2 filler is one of the main methods of improving the thermomechanical properties of epoxy resin (EP) composite insulating materials, and the characteristics of the filler is one of the important factors affecting the modification effect. In this paper, the effects of the shape and mass fraction of nano-SiO2 particles on the microstructure and thermomechanical properties of EP composites were studied by molecular dynamics simulation. The results show that the bonding energy (EBinding) between the spherical SiO2 filler and matrix is the largest, and the fraction free volume (FFV) and the mean square displacement (MSD) of the composite model are the lowest. With the increase of the filler mass fraction, the EBinding between the filler and matrix changed little, whereas both FFV and MSD showed a monotonous downward trend. The introduction of nano-SiO2 fillers can significantly improve the thermomechanical properties of the composites. The shape of the filler has little effect on the glass transition temperature (Tg), coefficient of thermal expansion (CTE), and mechanical properties of the composites. Increasing the mass fraction of the filler can obviously improve the modification effect. When the mass fraction of SiO2 is 15 wt. %, the Tg of the material increased by about 35 K, the glass state CTE decreased by about 35%, and the Young’s modulus and shear modulus increased by 24.56% and 32.45%, respectively.