Experimental assessment of the effect of surfacecondition on aged adhesive joint performance

Abstract Industries such as aerospace are very interested in the use of structural adhesives as a joining technique. Compared to riveting, they offer better stress distribution, eliminating stress peaks which can be quite problematic with thin sheet materials. The ability to bond different materials allows for a wider range of material combinations that result in weight reduction. Aluminium and other metals are popular in the aerospace industry, but their reactivity to water molecules compromises the bond strength. This presents problems for manufacturers in predicting and monitoring service life. This study addresses degradation at the interface and the importance of proper surface treatment. Two different adhesive types (epoxy and methylacrylate) and adherent materials (AW 5754 H111 and AISI 1.4301) result in four different sample configurations. Several pretreatments are applied, all using different mechanisms to improve adhesion Drozdziel2022 \cite{Ebnesajjad2015} Marques2020. After surface treatment, the contact angle with de-ionised water is measured, which is directly related to surface energy \cite{Ebnesajjad20151}. The samples are tested for residual lap shear strength after being subjected to an ageing trajectory for one week. Statistical analysis is used to establish a relationship between surface energy and residual lap shear strength. The importance of surface treatment is established, but there is no direct relationship between contact angle and joint durability. Corrosion protection appears to be important, and the adherent material and adhesive type determine the optimum surface treatment.