The project aims at the development and demonstration of a metallic solution combining innovative aluminium alloys of the Al-Cu-Li family and advanced assembling technologies such as Laser Beam Welding and hybrid welding. It will also investigate the potential of innovative split-beam process and will make a comparison with the laser and hybrid arc-laser processes. Aerostructures, including fuselage and wing stiffened panels, are responsible on average for 50% of total aircraft weight.
In order to obtain the required panel properties and a significant weight reduction, the strategy of the project is to combine the most suitable materials with the optimised welding process and an appropriate design. Recently developed low density Al-Cu-Li alloys offer direct weight reduction of about 5% and the improved property balance while conventional alloys allow further weight reduction of up to 20% through adapted design. The assembling process is a major field of improvement for the cost-effective use of aluminium alloys that will be explored in the project. Laser beam welding has demonstrated in the past to be the best suitable welding technology for flat panel production, especially for fuselage. The main advantages are the very low distortion, the absence of defects and reduced post-weld re-work. Hybrid laser welding combines the advantages of laser processes with arc welding resulting in high joint quality and completion rates with increased tolerances to fit up and without compromising joint quality and distortion control.
It is expected to be most suitable for wing panels. The objective is to demonstrate the feasibility of this material and process solution and bring it to a TRL of 4. For this purpose, the welding technology parameters will be optimised for Al-Cu-Li materials, and flat panels representative of the four major parts of the aircraft contributing to the total structure weight (i.e. bottom and crown fuselage and upper and lower wing) will be designed, manufactured and tested.
The project AFSIAL (Advanced fuselage and wing structure based on innovative aluminium lithium alloy - numerical trade off study and experimental stiffened panel validation) funded by Cleansky was mainly aimed to combine the most suitable materials with the optimised design and the best welding process, in order to obtain panels characterized by required properties and significant weight reduction. In detail, the aim of the project was to develop a metallic solution combining innovative aluminium alloys of the Al- Cu- Li family and advanced assembling technologies such as Laser Beam Welding, investigating also the possibility and potentiality expressed by hybrid welding and an innovative simultaneous double- sided dual beam welding of T joints, trying to demonstrate the feasibility of this material and process solution, bringing it to a TRL of 4.
The project Consortium initially consisted of 5 EU partners with overall coordination of ENEA, Italy. Two partners from France (Constellium and ESI Group), one from Great Britain (TWI Ltd) two from Italy (RTM s.p.a. and the same ENEA).
After various events, one of the consortium partners, RTM s.p.a., has bankrupt and its planned activities were not completed.
Initial work was focused on two main goals: the first one was to identify the low density aluminium alloys most suitable for each of the aero structure parts, while the second one was to identify the best welding configuration and the best laser parameter for the development of the welding process and manufacturing of the flat panels with laser (RTM) and hybrid laser (ENEA). In this context, it is included the development of split-beam laser welding in relation to low density aluminium alloys identified both from a performance point of view that energy, made by TWI ltd. This particular aim was an additional target that was originally proposed by the Consortium, as required by the P.O.
The project AFSIAL also aimed to numerically design and optimize a set of representative metallic aircraft panels. To make this, ESI Group (the Consortium partner who has been performing this activity) has also developed a novel procedure which was primarily in the combination of advanced multi-function optimization criteria in conjunction with highly non-linear structural behaviour, involving limit loads and eventual failure.
The last aim of AFSIAL was to manufacture some representative panels according to all specifications (material, welding parameters, numerically design) and to test them.
Unfortunately, the bankruptcy of RTM s.p.a nullified much of this last target. reducing what was expected to be the only attempt of welding wings by ENEA. The attempt also failed because of difficulties encountered in the machining of materials provided by Constellium as explained in other part of these reports.