Last week saw three milestones in the exploitation of composite materials in aerospace, with Airbus beginning assembly of the first A350's wings at its Broughton factory and the formal opening of the UK's National Composites Centre research park in Bristol.
Most of the A350 XWB wing is made of lightweight carbon composites, including the upper and lower wing covers, stringers, front and rear spars. Airbus claims advanced structural design and superior wing aerodynamics will be significant contributors to the aircraft's expected 25% fuel-saving performance.
That the project represents cutting-edge engineering is in no doubt. Rich Oldfield, technical director at UK engineering group GKN, which makes the wing spars and trailing edges in a dedicated facility 8km from the wing components plant in Filton, Bristol, it bought from Airbus in 2009, says the A350 project is the most technically challenging he has worked on in a career that began with Airbus and included a series of roles in design and manufacture of the A380's wings.
The National Composites Centre, owned and hosted by Bristol University and formally opened by Secretary of State for Business Vince Cable, boasts as its five founding members GKN Aerospace, Airbus, AgustaWestland, Rolls-Royce and Vestas, joined later by composite materials supplier Umeco.
A less visible but possibly equally significant composite materials milestone was the reaching of 2,600 members in the UK's Nanotechnology Knowledge Transfer Network (NanoKTN). The network, an initiative of the UK government's Technology Strategy Board, fosters communication between engineers, academics and manufacturers.
Martin Kemp, formerly with QinetiQ and now NanoKTN's engineering applications theme manager for aerospace, says the nanotechnology is slowly making its way into civil aircraft because aerospace is an inherently conservative industry, owing to its high costs, long product life cycles and the need for expensive certification of new structures and components. But, he believes, in a decade the exceptions in aerospace will be those structures and components that are not enabled by nanotechnology.
Nanotechnology has already made significant impacts in military aircraft, says Kemp, ranging from coatings that enable stealth performance to non-loadbearing composite structures in the Lockheed Martin F-35. The most spectacular example of a nano-enabled feature in a civil aircraft today is probably the electrochromic windows on the Boeing 787, which change from clear to opaque thanks to a nano coating. That technology, says Kemp, exemplifies the value of nanotechnology to aircraft, where weight saving counters the high cost of materials.
But where nanotechnology offers greatest promise in aerospace in the medium term is in composite structures, he says, by overcoming the lack of conductivity. While metal aircraft can disperse a lightning strike naturally, composite aircraft such as the 787 or A350 need to have conductors added, which increases weight and complexity. Nano-enabled resins, however, can be inherently conductive.
Also, where today's resins merely bind carbon fibres, nano-enabled resins can increase a structure's strength, or reduce weight, by introducing a new level of reinforcement. And, adds Kemp, nano-enabled resins offer exciting possibilities when it comes to developing self-healing materials.
"The next generation of composites will be very much nano-enabled," says Kemp. However, when that next generation is likely to appear in commercial applications, he says, is the "million dollar question".
Industry economics mean large structures will not be nano-enabled as soon as technically possible, Kemp believes, as "primary structures are locked in to existing resin technology". Rather, nanotechnology will "creep in around the edges", probably in cabin interior features such as fire-retardant fillers. Engine makers may also beat airframers to the nanotechnology starting gate, with, say, heat-resistant coatings for turbine blades.
Here, Kemp sees much opportunity for collaboration with the automotive industry, which shares aerospace concerns such as fire safety and weight reduction. But, because auto makers use vast quantities of components and materials compared with aerospace manufacturers, they are better able to shoulder the financial burden of development.
In the meanwhile, he adds, it is the job of organisations such as the National Composites Centre or NanoKTN to help designers and engineers realise the potential of what is, in fact, a broad basket of technologies offering many functional benefits that often are not well understood. "The key challenge is to raise awareness," he says.
Source: Flight International
