AEROSPACE
LASING ON THE WING
Additive manufacturing tends to deal with
Matthew Dale on some of the laser processing that goes into building aircraft, from treating carbon fibre wing skins to 3D printing lightweight brackets
E
fficient flight is influenced by aeronautical design and weight. In the past few years, metal additive manufacturing has come to fruition for fabricating aircraſt components,
largely because of the weight-saving advantages offered by the technique. Airbus began series production of 3D-printed titanium parts earlier in the year, concentrating first on a double-walled pipe elbow, part of the fuel system of the A400M transport aircraſt. Tese complex components were previously produced from individual cast parts that were then welded together to form one assembly, but are now built additively using machines from Concept Laser.
smaller parts that fit inside the printing machines. Saving weight on larger sections of the aircraſt, like the wings, is also important and most of these components are made from high-strength carbon fibre for this reason. At a conference on laser processing, run by the European Photonics Industry Consortium (EPIC) and held in Vilnius, Lithuania in September, it was stated that the use of these construction methods – both additive manufacturing and techniques for carbon fibre processing – will influence how lasers are adopted by the aeronautics sector in the future.
Lighter and stronger Sections of the wing, fuselage, and the tail assembly are now made largely with carbon fibre. Te established processes for building these structures are by automated fibre placement (AFP) and automated tape laying (ATL), but dry carbon fibre techniques that rely on lasers are improving the fabrication method considerably. Spanish firm MTorres supplies high-speed
ATL machines, Torreslayup, and AFP machines, Torresfiber, used to manufacture wing skins, as well as the stringers and spars that support the skin. ‘Tese processes have seen strong development in the past few years since the first ATL machines have been on the market,’ said Xabier Montón, a research and development engineer at MTorres. ‘Te reason for this is that carbon fibre is being increasingly introduced into the aerospace industry.’ AFP and ATL operate by laying strips of
Surface enhancement via direct metal deposition 14 LASER SYSTEMS EUROPE ISSUE 33 • WINTER 2016
carbon fibre tape across both simple and complex surfaces in multiple layers to form carbon fibre stacks. As the tape is layered, it passes in front of an infrared lamp and under a roller. Pre- impregnated (prepreg) composite fibres bound with an epoxy resin matrix are heated to 45°C by the lamp. Te tape becomes tacky, allowing
further tape to be layered over it and pressed down by the roller. Te resulting structure is then hardened in an autoclave at high temperature and pressure, where the epoxy inside the prepreg material sets. Tis setting process takes time however, and the prepreg material can be expensive. Tese processes are used to build a wide range
of parts, with MTorres using them for the tail assembly and fuselage sections, in addition to the wing components. Since 2012, however, MTorres has introduced alternative dry carbon fibre techniques, which rely on lasers, into its build processes. Dry carbon fibre methods differ from those
that use prepreg material, as the laid-up material does not contain any epoxy resin, but rather additives that allow the material to become tacky. Here, a diode or fibre laser heats the dry material additives to 120-180°C in order to layer and bind
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