Not so long ago, the ascent of composites in aerostructures manufacturing seemed an unstoppable progression that could only happen at the expense of metals. Fresh thinking at progressive companies like GKN Aerospace is changing that thinking, with engineers increasingly coming to the conclusion that the two families of materials can coexist in cooperative harmony to give manufacturers the best of both worlds.
GKN technology director Richard Oldfield leads a team working on the application of hybrid structures that combine titanium and composites. The company has devised a way to use degradable hooks to bind the two materials together until they become permanently bonded. Meanwhile, GKN continues to find ways to make more efficient use of the materials individually.
With composites it is increasingly building up structures from a composite powder, so that the manufacturer ends up using 90 percent of the raw material. The traditional approach involves starting with a composite block and then machining away 90 percent of the mass.
With metals, GKN, along with engine maker Rolls-Royce, is testing new sintering techniques in which metallic powder is heated to temperatures below its melting point and then formed into structures. The technique could reduce a four-stage forging process for making turbine blades into a single process. Meanwhile, other work continues to fine-tune the material properties of metals by remixing the powder content.
So for GKN and other aerostructures leaders, no longer must one necessarily choose between composites or metals. “What it comes down to is which material is most competitive and offers the highest [profit] margin [for a specific application], or could it be that this would be from a combination of both,” concluded Oldfield.