Exploring durability of interfaces in flax fibre/epoxy micro-composites

The influence of wet aging on the behaviour of flax/epoxy micro-composites composed of single flax fibres embedded in epoxy micro-droplets has been studied. Interfacial shear strength has been examined by debonding the micro-droplets. The apparent interfacial shear strength decreases with immersion time in water, dropping rapidly during the first 15 min of immersion then stabilizing. Drying samples after short immersion periods allows recovery of properties, indicating a plasticization mechanism. For longer immersion times irreversible degradation is observed. Scanning electron microscopy reveals fibre surface peeling, indicating that an internal interface within the fibre is weaker than the fibre/matrix interface after aging. A simple descriptive model has been used to identify diffusion kinetics, with a critical diffusion time corresponding to a change in degradation mechanism.