Characterization of particle diameter and interphase effects on young's modulus of SiO ₂/epoxy particulate composites

This study involves the investigation of spherically shaped filler diameter and interphase effects on the Young's modulus of micro and nano size silicon dioxide (SiO2) particle reinforced epoxy composite materials. Specifically, 10μm and 80nm size SiO2 particles and Epon 862 epoxy are chosen as fillers and a matrix material, respectively. While 10μm and 80nm SiO2 particles are dispersed in the epoxy through a direct shear mixing method, nano-composites are fabricated with hardener at desirable ratios. Both micro- and nano-composites are prepared at 2 different particle loading fractions for tensile testing. It is observed that the nano-composites show significant increase in Young's modulus over microcomposites, showing a linear increase as particle volume fraction increases. This could indicate that for nano-composites, the interphase region between the particle and matrix can considerably affect their mechanical properties. Here, we develop a finite element analysis (FEA) model to investigate the interphase effect on the Young's modulus of both micro- and nano-composites. This model demonstrates how to estimate the effective volume fraction of a particle as filler using a combined experimental/numerical approach. The effective volume fraction is shown to be important in predicting the mechanical response of nano-scale particles reinforced composite materials.