THE EFFECT OF ALUMINIUM SURFACE TREATMENTS ON THE APPARENT SHEAR STRENGTH OF HYBRID EPOXY SINGLE-LAP JOINTS

Francisco M. dos Santos, Tulio H. Panzera, Alysson H. S. Bueno, Rodrigo T. S. Freire, Cody Campsey
2018 Proceedings of the 4th Brazilian Conference on Composite Materials   unpublished
Adhesive bonding in aluminium plates has been used for some time in aeronautical and automotive applications in order to replace rivets or welding. Surface preparation of aluminium prior to bonding is an important step that guarantees the strength of the joint. The use of silica micro-inclusions in the adhesive layers, and wash primers can improve the adhesion strength by some degree. In this study, an experimental characterisation was conducted in order to verify the influence of the surface
more » ... eatment and silica micro-inclusions in the epoxy adhesive layers as well as the use of wash primer on the apparent shear strength of single-lap joints by tensile loading. Scanning electron microscopy (SEM), surface energy and Ra roughness measurements were conducted to characterize the aluminium surface. The results showed that the use of wash primer decreased the overall apparent shear strength of the joints in 55%. However, the inclusion of silica microparticles in the adhesive layers caused an increase of 24% in the shear strength. The surface treatment carried out with NaOH for one minute without the use of wash primer and with silica microinclusions provided the most resistant joint with mean apparent shear strength of 7.39 MPa. Cohesive break of the wash primer was the main cause of the decrease in strength. The joints without wash primer presented a mixture of cohesive and adhesive failure modes.
doi:10.21452/bccm4.2018.15.02 fatcat:hz4gghh5w5c2fc53qwn3coicka