Reduced interfacial adhesion in glass fibre-epoxy composites due to water absorption via molecular dynamics simulations

© 2018 Elsevier Ltd Molecular Dynamics simulations were used to investigate the effects of absorbed water on interfacial adhesion in an epoxy glass composite. The composite comprised SiO2 fibres, γ-Aminopropyltriethoxysilane (AMPTES) fibre sizing, and a diglycidyl ether bisphenol A (DGEBA)/isophorone diamine (IPD) epoxy matrix. An average solubility limit of 2.07 wt.% water was found in the simulated system, equivalent to 0.99 wt.% water in a full composite, while an experimental value of 1.15 wt.% was determined. The work of adhesion was calculated for simulated composites and compared to experimental tensile strength in unidirectional composites. Results for both dry and saturated conditions indicated SiO2-sizing as the critical interface for failure. Scanning electron microscopy of failed composites suggests more cohesive failures in the epoxy for the dry samples, while relatively clean fibre surfaces in the saturated samples indicate adhesive failure at the interface. This study shows how molecular simulation can be applied to sized fibre-reinforced composites