As the aviation industry continues to seek to reduce weight within the airframe, a new nanocomposite material offering all the strength of aluminium for half the weight is on offer from Alpine Advanced Materials. Originally developed by the renowned Lockheed Martin Skunk Works for the F-35 Lightning II, it’s called HX5, and we sat down with David Brantner, Alpine’s chief executive officer, to learn more about the material, its applications within aviation, certification, and digital design.
It’s principally aimed at secondary structures within the aircraft, including latches, brackets, hinges, and so on, but when we sat down with Alpine’s team at the RedCabin Aircraft Cabin Innovation Summit in Atlanta this autumn they also demonstrated options like armrest elements, data connectors for onboard units, and more.
“In general,” Brantner says, “HX5’s high strength lends itself to small- and medium-sized components that have complex designs. The material is also highly coatable, allowing for premium finishes for cabin aesthetics. The benefits of converting to HX5 from aluminum include weight savings, manufacturability, and environmental stability in harsh environments. HX5 resists degradation from chemicals and radiation — it also will not have galvanic corrosion when mated with dissimilar materials.”
This anti-corrosive property is critical in the aviation context, where materials are often subjected not only to operational-side constraints in the under-wing context, but also to the ravages of passengers, their children and their spilt Coca-Cola above the wing.
The very nature of HX5 and its ability to be molded and formed, Brantner says, “benefits digital design and analysis, but the primary benefit is that its low viscosity means the material can be used to manufacture very complex designs. HX5 has some very specific characteristics, but with our level of design expertise and experience using the material, we can anticipate how it will behave and create highly accurate models and designs. Alpine uses moldflow simulation analysis to understand and optimise the fibre orientation to export anisotropic material profiles for finite element analyses with high confidence results, while at the same time optimising the end component’s performance and manufacturability.”
Going into specifics around regulatory and certification requirements, “certification testing can be supplemented with Alpine’s extensive library of test data characterising the material, reducing or eliminating the need for individual material tests depending upon the certification requirements,” Brantner says. “HX5 passes all FST [flammability, smoke and toxicity] requirements for FAR 25.853 and has also passed abuse, cycle and load testing for cabin interior components. Future materials and hybrid solutions are in development, designed to deliver additional high specific-strength materials to replace higher strength alloys.”
Beyond individual components, too, Alpine systematically seeks to identify separate components adjacent to one another that can be combined in a single part design. This streamlines manufacturing, supplying and replacing multiple parts, as well as removing the need for fasteners that add both weight and complexity.
“Across a fleet of aircraft,” Brantner says, “the weight savings of high-volume components can compound to significant fuel savings as well as increased range or cargo capacity.”
At a time where the aviation supply chain is creaking in a number of places, this manufacturability is certainly desirable. Using a composite with injection molding is beneficial both because it is scalable and because it can substantially reduce lead times.
“Some of our customers are telling us they are experiencing 18-24 month lead times for some parts,” Brantner says. “In some cases, it may be possible to design, prototype, test, certify, and manufacture parts using HX5 in less time than it would take to wait for an existing part to be delivered.”
Indeed, the speed at which HX5 has itself come to market, transitioning from a sensitive military aviation context to one in which it can bring benefits to commercial aviation, is itself impressive. The industry can learn much from this speed and the way in which Alpine is seeking to find new and improved applications within the aircraft.