The pace of the metallics revival is quickening. The re-emergence of metallic solutions as alternatives to future wing structures, for example, is an area that is being actively developed by GKN Aerospace, a global Tier 1 supplier that has a very sizable stake in both metallic and composite structural manufacturing for all the major aerospace constructors.
The company believes that additive manufacturing (AM) presents a massive opportunity to create complex shapes, some of which would be impossible to manufacture using conventional methods, with higher functionality and different materials.
Using AM techniques, materials can be fused to form objects from 3-D models, building up structures iteratively instead of taking forgings and then machining material away. AM can produce highly complicated near-net-shape geometries with a good surface finish and, by almost eliminating the machining process, can make great savings in cost and carbon emissions.
GKN has invested heavily in exploring many different associated technologies but is presently focusing on processes such as electron beam melting, selective laser melting, and direct metal deposition techniques. It believes the potential for advanced welding and joining processes, such as laser welding, linear friction welding (LFW), and friction stir welding, is very applicable for future wing structures.
Laser welding techniques developed by GKN have been used on the European Ariane rocket nozzle and are now being applied to critical engine structures on the latest Rolls-Royce Trent XWB. They also are being studied for new aerostructures applications. LFW joins two items of material by rubbing them together until the surface gets hot enough to become plastic. A load then forces them together forming the joint. The technique can form near-net-shape engineered blanks, considerably reducing build costs. This has been developed to reduce the amount of waste material that can emerge from a forging (up to 90%).
The company is also looking closely at using LFW with titanium as well as dissimilar materials and alloys. It believes friction stir welding could replace today’s bolted and riveted metallic joints with large panels. This solid-state jointing process forces together parts under load with a rotating tool, heating and stirring the plasticized metal to bond the components.
The benefits are many and include reducing component weight, improving fatigue performance, reducing the parts count, lowering design and assembly costs, and making maintenance easier.
Little wonder then that at the front line of aerospace structural manufacturing, metallics are well positioned for a significant comeback.