Enhancement of static strength and long term durability of steel/epoxy joints through a fiber laser surface pre-treatment

The aim of this work is to investigate the effectiveness of laser irradiation on steel substrates for adhesive bonding. The evolution of surface topography and wettability for various pulse fluencies was investigated. The most suitable processing conditions were then selected and adhesive bonded steel/epoxy single-lap and T-peel joints were prepared for static testing. Moreover, in order to assess joint strength against environmental attack, an additional batch of samples was subjected to hydrothermal cycling before testing. The obtained results were compared with baseline samples fabricated using degreasing and sand blasting surface pre-treatments. Post-failure SEM analyses of fracture surfaces were undertaken to survey the locus of failure within the joint bond-line. Results indicated that laser irradiation effectively enhances the overall mechanical behavior of the joint under shear and peel loading. In addition, it allows to retain joint strength after exposure to aggressive environmental conditions.