Companies that make composite materials are preparing for high-volume manufacturing of advanced air mobility (AAM) vehicles, but lots of questions remain about how many will be needed and what materials may qualify for certification and production. Representatives from Aerolytics, Toray, Hexcel, BAE Systems, TxV Aero Composites, and the Utah Advanced Materials and Manufacturing Initiative addressed these issues during last week’s Vertical Flight Society Electric VTOL Symposium.
The materials and manufacturing specialists agreed that a key step in manufacturing designs like the new wave of eVTOL aircraft is the qualification of materials and processes that will eventually allow for high-volume manufacturing.
At the same time, standards for all the products that make up these vehicles need to be established. “Standards help promote efficiency, quality, and cost savings in the supply chain,” said Aerolytics president Bill Bihlman. He is working with U.S.-based standards organization SAE on establishing a materials committee to discuss standards.
While manufacturing composite materials is an efficient process, manufacturers may need new processes to carry that efficiency into the production of parts and assemblies that make up these AAM vehicles. “These next-gen materials and manufacturing methods are process-sensitive,” Bihlman explained.
Companies like Aerolytics will probably have to enter into cost-sharing agreements with prospective aircraft manufacturers, to help qualify the materials and processes. It’s one thing to develop a design that can be certified, but there is still the further challenge of taking it to the point where it can be produced in large volumes. One solution advocated by Aerolyatics is to use a traditional hand-layup process at the early stage and then for volume production switch to more advanced methods such as quick-cure thermoset, thermoplastic, or additive manufacturing. In any case, Bihlman maintained that test versions of the new aircraft need to be built using tooling that is as close as possible to the equipment that will be employed in the production phase. This would speed up the transition from prototype to production.
A key question for the AAM industry will be how manufacturers can ramp up production of flying vehicles to a level 10 or more times higher than current aircraft rates. “This surpasses what the aircraft industry has done,” said DeWayne Howell, senior application engineer and project manager at materials company Toray. “This is a brand-new world. We can work together to figure out the right material for the job.”
Various market projections anticipate a need for anywhere from more than 1,000 aircraft to as many as 200,000 in the coming decades. Even a medium-sized production rate of around 28,000 per year will take “a lot of work and preparation,” Howell said, especially with materials and processes.
What the AAM sector has in mind is a quantum leap in rates of output. Global production of all civil aircraft types doesn't exceed 3,000 units per year, with light airplanes accounting for less than a third of that total. Deliveries of all-composite airplanes such as Cirrus Aircraft’s SR series totaled 384 during 2019, and these are made using a hand-layup thermoset process. Icon Aircraft’s light sport A5 amphibious airplane also features a composite airframe. The work needed to produce all the composite parts and assemble them into SR20s and SR22s and A5s is not conducive to a high-volume production process that would yield thousands of units per year at a reasonable cost.
Toray plans to collaborate with manufacturers to figure out how to prototype, manufacture, and certify aircraft efficiently. It believes that AAM aircraft builders need to understand that certification is only one step and that it will take a lot more work to achieve quality standards and high-volume production.
Howell pointed out that the storage of composite materials will be an issue. Some composites require cold storage prior to use, and to maintain high throughput, a manufacturer might need huge warehouses to store materials.
There are new processes that might help reduce manufacturing costs, he explained, such as rapid-molding thermoset, which should compete with the lower cost of thermoplastic processes.
Ultimately, he said, the FAA and EASA need to agree on how these new aircraft and their production processes will be certified so manufacturers don’t have to deal with different approaches from each regulator.
“There is no one material or process that’s going to be the best fit for the application,” said Imad Atallah, director of strategic marketing at Hexcel. The intersection of high build rates and cost are key, he added, as are maintaining aerospace grade and quality. “There are a lot of trade-offs that are going to come into play, including size, automation, the performance of materials, and how we’re supporting them in the field.”
While Hexcel produces both thermoset and thermoplastic materials, it has long specialized in thermoset. Atallah doesn’t envision manufacturers building their own facilities for materials storage but expects them to use just-in-time delivery from manufacturers like Hexcel.
In his view, materials that are already qualified and in use by aircraft manufacturers will drive the first phase of UAM manufacture and will minimize the risks to certification. “To meet the rate and cost needs of these vehicles, materials technology has to evolve," Atallah said. "That’s what’s happening now to support the second phase.”
Hexcel is working on solutions, including rapid curing to speed parts production, resin infusion during part manufacture, and thermoplastic development. “It’s about different solutions for different applications,” Atallah said.
“It’s easy to say regulations are going to be a challenge and that technology needs to evolve," Atallah concluded. "A lot of these challenges are solvable. The elephant in the room is the realization that there’s another huge level of investment for the second phase, to make sense from a rate and cost perspective. It will happen. It’s solvable; it’s just a matter of how and when.”
BAE Systems is applying its experience in manufacturing electric and hybrid-electric power systems for trucks, buses, and marine applications to the challenges in the AAM market. Systems engineering manager Bob Hess sees opportunities to reduce the weight in battery systems, which account for 25 to 30 percent of vehicle weight. “We want to reduce the weight of everything around [these vehicles], so we’re looking for lightweight materials,” he said.
The key to lowering costs is high volume, he explained. Certification costs are high and if they can’t be spread over a larger number of units, then costs per unit won’t come down. And in the case of battery systems, he said, “samples for testing are very expensive.”