Fatigue behaviour of laser machined 2024 T3 aeronautic aluminium alloy

High power laser applications as welding, machining and marking are widely used in several industrial sectors to take advantage of their high processing velocity, clean processing conditions, and a high versatility. However, the heat affected zone (HAZ) is expected to change the mechanical behaviour of laser processed structural elements. For aeronautic applications, this feature is of first importance because those elements suffer cyclic stress under service conditions. Indeed, the most severe requirements for further industrial implantation are the fatigue specifications. In this communication, fatigue behaviour of laser machined 2024 aluminium alloy is studied to evaluate a possible certification of laser-based machining in the aeronautic industry. For this reason, 1.6 mm thick samples laser machined were carried out using a CO2 laser. The experimental fatigue curves are shown to lie very close to aeronautic requirement despite theoretical fatigue behaviour of the material is significantly more resistant. This is attributed to surface roughness induced by a surface melting zone shown that diminish the fatigue resistance. Fatigue behaviour and surface roughness should be improved using higher power and/or high absorption wavelength as that of YAG laser (λ=1.06 μm).