Influence of plasma surface treatment on bond strength behaviour of an adhesively bonded aluminium-epoxy system

Abstract Aluminium-epoxy systems are widely studied for uses as adhesive structural bonding. When an amine hardener is used as a curing agent for an epoxy resin, interactions between the hardener and the aluminium create a volume called an interphase, whose properties are distinct from the bulk resin and has a significant influence on the adhesive bond strength. This article reports on the influence of an aluminium surface treatment on the interphase formation and adhesive bond strength. The aluminium surface was degreased with acetone, and then the surface was activated by means of atmospheric plasma treatment with different nitrogen/oxygen gas mixtures. The characterization of the aluminium surface chemistry and surface energy was determined by X-ray photoelectron spectroscopy (XPS) and a sessile drop test, respectively. The interphase formation was investigated by means of X-ray energy dispersion spectrometer (EDS) in a low vacuum scanning electron microscopy (LVSEM). Adhesive bond strength was measured by tensile testing of a single lap aluminium-epoxy-aluminium assembly. Atmospheric plasma treatment showed an improvement of the thermo-mechanical properties of the assembly. Several points were discussed to explain the effect of atmospheric plasma treatment on the adherence and on the interphase formation.