IIW White Paper

9 Needs and challenges of major industry sectors for future applications

A380) laser welded (skin-stringer) panels are used and efforts are being made to increase the use of such components in future aircraft ( Figure 9.14 ). The challenge, however, is coming from reinforced composite materials technology and competition between the welded metallic option and composite structure for cost and weight savings will decide future aircraft technologies. This trend and development are accompanied with the differences in damage tolerance performances of both manufacturing routes ( Figure 9.15 ). Welding technologies together with new weldable high strength Al-alloys and with the use of “local engineering” are capable to generate damage tolerant, safe components. This position, however, needs to be maintained or reinforced with numerous scientific and technological developments in design and improvements in understanding of the damage tolerance behaviours. It is expected that the major challenge will be in the development of advanced joining technologies for the fabrication of “material-mix” or “multi- material” (e.g. metal-composite components) of future airframe structures.

Figure 9.15 Trends in use of welded panels for European aircraft A380, A340 and A318. ( Reproduced courtesy: AIRBUS)

Development of new filler wires beyond currently used 12%Si containing wires for LBW process will significantly contribute to the potential use of the welded airframe panels.

Additionally, new developments in design, inspection (structural health monitoring), fatigue and fracture aspects will enhance the competitive position of the welded Al-alloy airframe components against adhesively bonded composite structures. In addition to the current use of laser beam welding technology in lower shell regions of the European commercial aircraft, such as the A380, A340 and A318, side and upper fuselage regions of these aircrafts should be new application targets for welded fuselage assemblies. Design requirements of upper fuselage parts, however, are different from lower shell regions and hence higher damage tolerance properties are needed for the welded skin-stringer assemblies. This will be a new challenge for the welding mechanics.

In addition to the challenges of LB welding of thin-walled Al-airframe structures, described above, the following topics are considered as major areas of interest in aerospace applications.

9.18.1 Hot topics Dissimilar materials joining : The drive towards maximum structural efficiency is pushing the need for joining technology for dissimilar materials. Such joints allow point-to-point optimisation of material properties, including strength to weight ratio, high temperature stability, etc. Riveting results in point load stress management and corrosion potential, adding weight and cost while reducing reliability and lifetime. Adhesive bonding and other joining methods, including welding, soldering, and brazing, offer alternatives for structural efficiency and increased temperature performance. NDE of joints combining complex material arrays requires updating and development.

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