Design case study for a comparative performance analysis of aerospace materials

Reduction of the life cycle cost of aircraft is the main focus of aerospace material development at the moment. By improving the performance of aluminium alloys and using other material systems such as carbon fibre reinforced plastics (CFRP), the life cycle cost can be reduced. This paper presents a design study of a pressurised fuselage section in aluminium and CFRP, focussing on the appropriate design criteria that are to be included for each material to get a sound comparison. Furthermore, a new reference for the aluminium fuselage will be presented applying new alloys and production techniques. Damage tolerance characteristics of both aluminium and CFRP are discussed, and appropriate design philosophies are presented. A correlation between residual strength and stiffening ratio is identified and used for the optimisation of the designs. It is concluded that limited fatigue damage growth and residual strength are the main design drivers for a pressurised fuselage, and the main weakness of CFRP is identified in this field, especially when looking at the compressive strength after impact and sensitivity to damages in tension. The new and improved aluminium alloys show an increase in yield stress and fracture toughness, and by laser-welding the stiffeners to the skin, the performance in compression and the fatigue life of the panel increases.