Novel Concepts to Further Improve the Performance of Aluminium Aircraft Structures

Aircraft structures need to offer reduced operating cost including maintenance, ease of manufacturing and reduced fuel burn. Aluminium alloys are well suited to the application of novel technologies addressing these challenges.

Bonding is shown to combine the advantages of multiple load paths with the joint stiffness and improved fatigue and corrosion performance associated with the absence of rivets. The performance of bonded joints in compression and damage tolerance is demonstrated through tests on typically 1.5 x 1 m demonstrators. The weight impact of bonding alone compared to riveting can be estimated at about 5%.

Structural health monitoring of lower wing stringers and fuselage frames can be used to improve maintenance schedule or save weight. The SHM system is used to demonstrate that the stiffening element is intact which changes the damage tolerance scenario. The impact on weight is typically up to 20% in damage tolerance driven areas. Extrusions in AIRWARE^TM have been produced with channels allowing pressure monitoring and with embedded fibre optics. Both systems have been successfully tested which demonstrate the feasibility of the concept. Maturation of the technology would require a demonstration of the reliability of the systems and/or the application of redundant systems. SHM relies on the fact that no failure should be expected in the equipped major components, so that the demonstration of the health is looked for rather than the detection of defects.

Friction stir welding is perceived as a method to reduce manufacturing cost and improve structures’ corrosion resistance. The weight impact is generally marginal but can be obtained through the suppression of flanges required to rivet, or the combination of material in tailored structures. But the tailoring of the thickness alone to manufacture nearer net shape billet prior to machining is the main advantage, in particular in the case of AIRWARE^TM. The manufacturability of large components in AIRWARE^TM will be presented, showing that the technology will mature as soon as it is adopted on major structural elements of aircraft.

The advanced technologies presented demonstrate the developments beyond new alloys introduction that can improve the aluminium aircraft structures performance in the coming decade.