Influence of nanoporous structure on mechanical strength of aluminium and aluminium alloy adhesive structural joints

Abstract

The influence of surface treatments on the mechanical strength of adhesive joints was investigated. The attention was focused on AA2024 alloy because it is extensively used in both the automotive and aerospace industries. Adhesive joints fabricated with pure aluminium were also investigated in order to evidence possible differences in the surface features after identical treatments. Before joining with a commercial epoxy adhesive, metal substrates were subjected to different kinds of treatment and the surfaces were characterized by SEM analysis. The formation of a microporous surface in the AA2024 alloy, upon etching and anodizing, is discussed on the basis of the role of the intermetallic particles and their electrochemical behaviour with respect to the aluminium matrix. Moreover, nanostructured porous oxide layers on both type of substrate were also formed, as a consequence of the anodizing process. Differences in their morphologies were revealed as a function of both the applied voltage and the presence of alloying elements. On this basis, an explanation of the different values of fracture energy measured by means of T-peel tests carried out on the corresponding joints was attempted.

Self‐Healing Anticorrosion Coatings Based on pH‐Sensitive Polyelectrolyte/Inhibitor Sandwichlike Nanostructures

“…The most extensively used surface pretreatment procedures are based on aggressive chemicals including chromate solutions. [11] It is generally expected that the surface pretreatment produces a porous oxide layer on the metal surface with roughness sufficient for mechanical interlocking. Here, we applied for the first time intensive sonication in water with an ultrasonic horn for surface pretreatment of aluminum alloy.…”

On the effect of pulsed laser ablation on shear strength and mode I fracture toughness of Al/epoxy adhesive joints

“…[4] On the other hand, anodizing processes affect adhesion and durability by mean of an electrochemically formed porous oxide layer that improves chemical interaction between the adhesive and the adherends. [5] Recent works have focused on laser irradiation carried out by mean of excimer, solid state or fiber lasers, e.g. ytterbium (Yb) fiber laser.…”