The weight, durability, and performance characteristics of carbon-fiber composites make these materials ideal for the high-specification requirements of aerospace, which is why manufacturers of aircraft ranging from large airliners to helicopters have introduced them to their products over the years.
Typically, however, composites are more expensive than conventional materials. So what does this mean for an emerging sector such as eVTOL where there’s a need for low costs as well as high production rates and high performance?
We spoke with several specialists in composite materials active in the urban air mobility market — Aria Group, Toray Advanced Composites, Hexcel, and Autoscale CNC — to find out more about their approaches to the eVTOL space.
Optimization is regarded as important. Steve Mead, managing director of Toray Advanced Composites — which works with eVTOL developers on developing and qualifying high-performing materials — said: “The real focus is ‘the right material for the right part in the right volumes.’
“There is no ‘one-size-fits-all’ structural material; the best solution will be to use materials optimized to meet specific part requirements, and that needs to include production rates of these parts.”
Toray’s offerings include toughened epoxy resins with intermediate modulus fibers for critical structural applications, and high temperature thermoplastic resins with fibers for rotor blades and interiors.
Mead explained, “A fuselage structure built at, say, 1,000 units per year will likely use very different materials than the engine rotors on that same vehicle, which will need to be produced at a much higher rate.
“Or, consider the interior materials, which need to be very durable given the passenger dynamics — a lot of ‘in and out’ during the day — but will need to be lightweight and low cost. Every one of these applications will need fundamentally different materials, but with one thing in common: affordable, lightweight structural performance.”
Imad Atallah, director of strategic marketing at Hexcel, agreed that composites must “optimally meet the required mechanical performance with the right products, [offer] the ability to build structures at high rate and meet cost targets, and [provide] the ability to mitigate and absorb noise.”
Atallah said, “We plan to offer carbon fiber, prepregs such as quick cure thermosets and thermoplastics, honeycomb solutions for structure and noise dampening, as well as engineered structures and products.”
The big picture
Optimization obviously requires close partnership between a supplier and customer. Atallah said Hexcel “is working with many vehicle manufacturers and designers to understand their requirements and needs to provide value-added offerings.”
Toray’s Mead commented, “Simply offering a vehicle for sale may not be the best approach; bringing true end-to-end solutions that include the vehicle, the infrastructure, and the actual ridesharing services appears to be the model that will enable urban air mobility to develop successfully over time.”
This industry lives and dies on volume — there has to be enough vehicles operating to make the business case work. It’s a whole new paradigm for aerospace.Clive Hawkins, Aria Group president and CEO
Aria Group, another composites specialist with design, production engineering, and low-volume manufacturing experience, also stresses the importance of collaboration.
Clive Hawkins, Aria Group president and CEO, told eVTOL.com the company works with customers to “really understand the viability of these products from a manufacturing standpoint” as well as working on the “overall conceptual design, ergonomics, and human interface with the machine.”
Another challenge for composites suppliers in the eVTOL domain is cost-effective production at high volumes to meet projected demand in the market.
Hawkins believes balancing the sometimes-conflicting requirements between cost-effectiveness and an optimized product needs “fresh thought as to how [aircraft] will be produced from a volume per annum and cost of manufacturing standpoint.”
Aria has set up a new standalone division of the business called Aria Composite Systems (ACS). This unit intends to build on the group’s history, established over the past 25 years, of researching, designing, and rapidly manufacturing composite parts, and helping customers develop new products from concept through to prototype development.
The ACS division will build on work the company has already undertaken in the field. Aria has, Hawkins said, “helped a number of companies take concepts into first-level prototypes, some in the manned space flying [and] some in the static space helping to visualize what these products are going to be as they mature. We’ve built full-size prototypes, flying and static, for various companies.”
A high-profile example was unveiled in January 2020 at the Consumer Electronics Show (CES) in Las Vegas, where the company revealed it had built the SA-1 Personal Air Vehicle prototype unveiled by Hyundai Motor and Uber Elevate.
In a press release issued during the event, Hawkins said, “Our clients provided us with a relatively simple list of requirements, and we were able to take charge of the entire program from there, engineering and developing all the manufacturing, structural, and control aspects necessary to install a working prototype.”
Aria engineered and manufactured hundreds of unique and complex carbon composite components for the eVTOL aircraft in-house, developed the complete assembly and shipping strategy, the show stand concept, a complete electronic control system, and all the tooling to produce the parts.
How do the specialists plan to scale up production? Toray’s Mead says: “We have sufficient scale in our fiber and thermoset prepreg materials capacity to support this market even in the highest build rate scenarios.
“If we do see a need to add capacity in this niche, we will add that capacity either in the USA, or at our facilities in Europe, depending on market needs. We can scale up our thermoplastic capacities quickly, so we will be able to make these decisions once we have a clearer picture of where the market is headed.”
Mead said Toray “will be focusing on resin and prepreg technologies that are capable of meeting high production rates, given that the vehicle build rates are projected to be multiple times higher in the eVTOL market when compared to the current aerospace market.”
He added, “Also, because of the critical issues related to weight, we will likely be focusing more on our higher performing carbon fiber offering, including T1100 fiber, which enable structures to be designed at the lowest possible weight while still meeting the structural requirements of the aircraft.”
Another specialist, the San Francisco Bay Area-based Autoscale CNC — which offers machining, fabrication, and prototype manufacturing — uses large-scale additive manufacturing machines to lay up, mill, and assemble carbon-fiber parts.
The company’s founder and owner, Dan Bolfing, explained: “We’ll cut the molds and lay them up. The machine is so large that we can lay up a part in one area and then use the machine to trim and drill all the components that go to the aircraft.”
The technique means the company does not have to use the traditional method of laying up and cutting carbon fiber before trimming and drilling separately, with the two halves of the mold put together to build a part. “We literally use the machine to build the aircraft,” Bolfing said.
Autoscale CNC has already demonstrated its capabilities for the urban air mobility sphere in a project that involved laminating and machining carbon fiber and glass fiber parts for the interior of a non-flying concept vehicle produced by Zee Aero (which became part of the Kitty Hawk Corporation).
Bolfing believes Autoscale CNC’s approach enables it to bring products to market in “a fast and cost-effective way,” saying: “We can be a one-stop shop. We have 35 years’ experience in all types of composites and machining. We do everything. What makes our machines unique is the price point.”
Aria’s Hawkins feels how eVTOL vehicles are “designed for manufacture” will be “critical” in the market’s fortunes.
He said, “In our opinion, for this industry to be successful somebody has to reconsider the manufacturing process, bringing in the high level of automation that is typical in the aerospace industry and manufacturing processes and technologies that are more suitable to volume.”
Hawkins continued: “This industry lives and dies on volume — there has to be enough vehicles operating to make the business case work. It’s a whole new paradigm for aerospace. The question is, can you build them at the volume and price that is in alignment with the business model?”
The automotive industry could provide clues on how to achieve this, Hawkins feels. “The major aerospace companies can manufacture high-quality performance parts at high prices and fairly low volume, and the automotive industry is king at manufacturing at high volumes and low prices,” he said. “There’s a gap between the two of them that’s needed to fill this industry.”