Controlled interfacial adhesion of Twaron® aramid fibres in composites by the finish formulation

In order to investigate the effect of oily finish components on the interphase strength of aramid-epoxy composites, Twaron® aramid yarn has been treated in a one step finish process with combinations of adhesion improving (epoxy-amine) components and processability improving (oily) components. Variations in the macroscopic composite properties (compression shear strength and transverse tensile strength) as a function of the amount of oil are very well predicted by micro-mechanical adhesion results from single filament pull out measurements and micro Raman spectroscopy. They can be explained by differences in the amount and distribution of epoxy, fixated to the yarn surface, shown by XPS, contact angle measurements and atomic force microscopy.