Experimental and numerical investigation of the effect of metal surface treatments on the delamination behaviour of magnesium alloy-based Fibre Metal Laminates

Abstract

The main goal of this research is to experimentally investigate and numerically model the delamination behaviour of magnesium alloy-based Fibre Metal Laminates (FMLs) making use of metal sheets of different surface treatments as the latter can greatly affect the FML interface bonding strength and delamination behaviour. Before fabricating the FML through hot pressing, the magnesium alloy sheet surfaces were prepared through six different treatments: the first three included sandblasting carried out using different pressures, namely 1, 3 and 5 bar, while the other three treatments contemplated annealing after sandblasting. The effect of the different metal sheet treatments on the FML interface bonding strength and delamination behaviour was studied by means of numerical and experimental analyses. In particular, a novel normal separation test was proposed and carried out to measure the FML interlaminar properties along the normal direction (Mode Ⅰ), whereas the conventional single lap shear test was performed for obtaining the interlaminar properties along the shear direction (Mode Ⅱ). It was found that the bonding strength increased at increasing roughness of the metal sheets and that annealing could improve the bonding strength. Based on the normal separation and single lap shear tests experimental data, a new metal surface roughness dependent traction separation model was developed, accounting for the relationship between the metal sheet surface roughness and interlaminar performances for Mode Ⅰ and Mode Ⅱ. T-peel tests were finally carried out and numerically simulated in order to validate the newly proposed material model, proving a satisfactory agreement between experimental and numerical results.