All things wings

With the drive for increased performance and lower emissions, aircraft wing design is under new levels of scrutiny. And with a parallel need to manufacture airframes at rates higher than have ever been achieved before - with absolute consistency and to ever tighter tolerances - developing manufacturing processes that will realise innovative future wing design is a critical imperative.    Today, GKN Aerospace's wing structures operation is among the top three tier one suppliers to the primes, distinguished by the depth and breadth of technological expertise. It is making a major contribution to wing development - most recently working on the design of the A350 rear spar, CSeries winglet and aileron and Dassault SMS trailing edge moveables.  It is the company's bedrock of enabling technologies that it believes will make a valuable contribution to future wing development programmes, whether turbulent or laminar flow, metal or composite. The list of wing structure opportunities is significant: short- and mid-term upgrades of existing platforms such as the A320neo and the 737MAX, the A350-1000 and 787-10, and longer term prospects including a 777 upgrade and the next generation single aisle (NGSA). GKN Aerospace will offer wing structures such as winglets, spars, advanced moveables, leading and trailing edge sub-assemblies, integrated box structures, assemblies and covers. So what will be the defining technologies of the next generation of wings?  “It will be a combination of technologies to support potential new wing architectures, more integrated composite structures, advanced metallic fabrication and additive technologies,” says GKN Aerospace's vice-president, technology, John Cornforth. “This will be underpinned by increasing levels of automation and high rate production.” Laminar flow wing concepts The most significant architectural change to wings of the future could be the introduction of laminar flow wing concepts. These require significantly different aerodynamic profiles, sweep, surface finish and tolerance control as well as posing significant structural and integration challenges. GKN Aerospace is developing wing upper cover, fixed leading edge and Krueger slat concepts in partnership with Airbus to explore the feasibility of such a change. Looking at the R&D underway within GKN Aerospace's advanced composites activity, this is focused on improving every step of the manufacturing process, examining high rate automated deposition, alternative curing and joining methods, rapid NDT, surface protection and coatings and automated laser repair. Alternatives to autoclave curing being explored are: out of autoclave (OOA) curing using vacuum bag technology and OOA materials, with a development programme completed which created an affordable, lightweight, blended aircraft wing box using these processes; and microwave curing, which could bring average curing times down by as much as 80%. An example of work focused on alternative joining methods is the company's work with ‘waffle skin' structures. In a winglet, these could replace the traditional structural spars, plus ribs and upper and lower skins with a one piece, ‘multi-spar' structure that is co-cured to the skins, speeding and simplifying manufacture and assembly, and lowering weight. Recognising the need to speed and automate composite repair, GKN Aerospace is bringing automated laser ablation to market readiness. Here, lasers vaporise the epoxy resin, leaving the healthy carbon fibres to be brushed away. The technique does not impact the integrity of the surrounding structure and the finished repair is as strong, more consistent and around 50% less costly than a manual repair. This could lead to integration with other aspects of the repair process to create effective automated component repair.   The might of metallics Looking at metallic activities, the pace of innovation at the company is just as dynamic and could see a re-emergence of metallic solutions as compelling alternatives to wing structures of the future. Additive manufacturing (AM) presents a mind-boggling opportunity to create impossible shapes with higher functionality, and using different materials than has been possible before. The process fuses materials to make objects from 3D models, building structures iteratively rather than machining material away from forgings. AM can produce highly complex near-net shape geometries with a relatively good surface finish at little cost in energy and carbon emissions and requiring minimal machining. The term covers many different technologies and GKN Aerospace is focusing on processes such as electron beam melting (EBM), selective laser melting (SLM) and direct metal deposition (DMD) techniques. Equally interesting is the potential for advanced welding and joining processes such as laser welding, linear friction welding and friction stir welding for wing structures of the future. Laser welding techniques, developed by GKN Aerospace for the use on the Ariane rocket nozzle, are being applied to critical engine structures on the Trent XWB with Rolls-Royce and explored for aerostructures applications. Linear friction welding (LFW) joins two pieces of material by rubbing them together until the surface gets hot enough to become plastic. A load then forces the two pieces together, forming a joint. LFW can produce near net shape engineered blanks, significantly reducing the ‘buy to fly' cost. This is an important goal in a sector where up to 90% of the material in an original forging can be wasted. GKN Aerospace is exploring using LFW with titanium as well as evaluating joining dissimilar materials and alloys. Friction stir welding (FSW) could replace existing bolted and/or riveted metallic joints with large panels. This solid state joining process forces together parts under load with a rotating tool, heating and stirring the plasticised metal to bond the components. This promising process could reduce component weight, improve fatigue performance, reduces parts count and stock, lower design and assembly costs and ease maintenance.   GKN Aerospace has complementary niche technologies that are being explored to maximise wing performance and reduce maintenance. Intelligent coatings and ice protection are two examples. The company is exploring ice phobic coatings that stop ice adhering to critical wing surfaces, and damage detection coatings that, when applied to composite structure, provide an easily identifiable ultra-violet indication of impact damage.  “This is an exciting time to be an engineer at GKN Aerospace.” reflects GKN Aerospace's technical director, Richard Oldfield. “We are very serious about the critical role of technology and we intend to be a major contributor to the aircraft programmes of the future. We are a clear illustration of the level of innovation underway across our industry globally, focused on creating and supporting high performance future wing designs.”  www.gknaerospace.com