The mechanical performance of a thick-walled multi-chamber aluminium extruded profile serving as a protective structure for battery trays in electric vehicles is assessed. Two high-strength aluminium alloys commonly used in the automotive industry are compared. The mechanical behaviour of the AA6082 and AA6005 alloys in peak-strength conditions is compared in a pole-crushing scenario. A material testing campaign is initially conducted to evaluate the mechanical behaviour of each aluminium alloy. Tensile specimens are extracted from various locations of the profile. The results from these experiments are employed to calibrate an isotropic elastic-plastic material model following an inverse modelling approach. An uncoupled damage criterion is also calibrated and included in the material model. Both AA6082 and AA6005 thick-walled extruded profiles are tested under quasi-static and dynamic pole-crushing tests. The experimental results are compared with explicit finite element simulations, and serve as a validation of the applied constitutive model. An optimization of the cross-section for both AA6082 and AA6005 aluminium alloys is presented. A genetic algorithm approach is adopted as the optimization algorithm. Thicknesses and coordinates of the cross-section are optimised to maximize the specific energy absorption capacity of the extrusion. Furthermore, an optimization of the material model is conducted. The yield surface and the work-hardening parameters are optimised, and the results are compared to the geometrical optimization.