Enhancement of the adhesive joint strength of the epoxy–amine system via the addition of a resole-type phenolic resin

In this paper the enhancement of the adhesive joint strength of the epoxy–amine system via the addition of a resole-type phenolic resin is investigated. Adhesive blends are formulated from a commercial epoxy and a synthesised resole-type phenolic resin. Phenolic contents are varied from 0% to 30%. The blends are characterized using Fourier transform infrared (FTIR) while the adhesive joint strength and the interfacial fracture toughness are studied for the adhesive blend/aluminium joint using single-lap shear and symmetrical and asymmetrical DCB specimens. It is found that the addition of resole improves the strength of the adhesive joint as well as its fracture toughness. The failure mode is found a function of the resole content. Resole contents less that 10% result in adhesive failure, while for resole contents of 20% and 30% the failure surfaces show adhesive and cohesive regions. The results allow concluding that the addition of resole-type phenolic resins constitutes an effective mean to enhance the adhesive properties of the epoxy–amine systems.