The manufacturing/fabrication processes in case of eVTOL parts don’t hold a lot of surprises since the design requirements are more or less at par with the existing aviation standards and the expected performance parameters are also the same.
Just like aerospace, in the fabrication of primary structural parts like wings, fuselage, etc., prepreg materials will be used more heavily as compared to dry fabrics, together with vacuum bagging. One key enabler however, in case of eVTOL parts, for exploring new fabrication methods is the smaller dimension of the parts as compared to traditional aircraft. Because of the smaller dimensions of end parts, faster processes like compression molding will find more applications in eVTOLs as compared to conventional aircraft. Not to mention, for smaller, less complex parts requiring high-volume manufacturing like rotor blades, compression molding will be the preferred process.
For smaller and more complex parts like brackets that require high-resolution manufacturing, 3D printing can be employed since it is already finding sufficient applications in eVTOL prototyping.
Now coming to the volumes, the combined annual production volume, based on the individual manufacturing targets put forward by different leading OEMs, can be expected to surpass the 6,000 units mark within 5 years into commercialization. These are the kinds of volume that the automotive industry is more comfortable working with, rather than aerospace. Also, eVTOL as an application will claim almost its entire share from road-taxis, rather than conventional aircraft. Thus, it would be safe to describe eVTOLs as a common ground between aerospace and automotive, and Figure 3 presents a high-level comparison between all three:
As a consequence, key players from the automotive supply chain are showing huge interest in this industry and have also formed long-term partnerships with the existing players. Porsche’s partnership with Embraer’s subsidiary Eve Air Mobility, Toyota’s partnership with Joby, Lilium’s partnership with Denso, Archer Aviation’s partnership with Stellantis, etc. are but some examples of the automotive-eVTOL synergy. The interest of the automotive industry isn’t however just limited to partnerships. Key automotive OEMs like Honda and Hyundai have come up with their own eVTOL programs as well.
The overlapping interests between the eVTOL and the automotive industry will likely open up more cross-industrial opportunities in the coming time.
The Checklist for Material Selection: Recyclability, Mass Production Compatibility, and Ease of Certification
Being the aerospace industry’s ‘go-to’ material, more than 90% of the composites used in eVTOLs would be carbon fibre, infused with epoxy. From a design point of view, this is because carbon fibre has the highest specific stiffness of any commercially available fibre and it perfectly fulfils all the mechanical requirements like lightweight, high strength-to-weight ratio, impact resistance, etc. On the other hand, from a strategic point of view, this is because almost every eVTOL OEM is planning to pass the certification process as smoothly as possible, without experimenting much with the tried and tested materials.
The same approach can be seen on the matrix level too, where again, more than 95% of the leading players are aiming for thermoset-rich models since the regulatory authorities are more familiar with thermosets and it will ease up the certification process for them a bit. According to Stratview Research, of the overall demand for composite materials from the eVTOL industry, thermoplastics will likely have a single-digit share of the demand till 2030.
What many experts from the aerospace and the composites industry also told Stratview Research during some recent one-on-one interviews is that choosing to stick to thermosets instead of thermoplastics is fine as long as they are able to keep the manufacturing volume within a few thousand aircraft annually. But once the production scales up (which, according to the OEMs, will happen in the next five years), the OEMs will either have to introduce new thermoplastic-rich models or they’ll have to modify their existing thermoset-rich models to thermoplastic-rich ones. In either case, they’ll have to knock on the doors of the regulatory authorities once again.
Currently, among the visible eVTOL OEMs, Texas-based Jaunt Air Mobility is the only one working on a thermoplastic-rich model and in fact, on their company’s website, Jaunt Air mentions ‘99% recyclable’ as one of the specifications of its eVTOL.
For eVTOLs, recyclability becomes all the more important because of its not-so-long (15-20 years) product cycle. If the industry keeps producing thousands of eVTOLs for the next 5-10 years and they all start becoming obsolete after a service period of ~20 years, the industry will have piles of composites to take care of.
Potential Turbulence for eVTOLs:
Some major factors that could further delay the take-off of the eVTOL industry, are:
- Shortage of manufacturing capacity:
The aerospace industry is expected to be back at its full capacity by 2025, making full utilization of the available manufacturing capacity for itself. Under such a scenario, if the industry is faced with a new vertical altogether, with yearly production volumes of a few thousand, a shortage of production capacity can take place. The targeted production volumes also make the integration of automated production lines, inevitable for the OEMs. - Shortage of Raw Materials:
At the end of the 24th annual Carbon Fibre conference, held in November 2021, industry consultants Tony Roberts, principal of AJR Consultant (Lake Elsinore, California), and Dan Pichler, director, carbon fibre, at carbon fibre manufacturer AKSA Akrilik Kimya Sanayii A.S. (Istanbul, Turkey) estimated a potential shortfall of 55, 250 metric tons of carbon fibre in 2026, with all supporting figures. According to them, the deficiency could start appearing as soon as 2023. Now, for vehicles that are >70% composites, such a shortage would mean delayed deliveries, and hence, a huge loss of revenue. - Lack of UAM-supporting Infrastructure: The lack of UAM-supporting infrastructure will largely limit the no. of cities to which it can be expanded. Currently, there are fewer than a hundred cities worldwide that are ready to support UAM. Los Angeles, Miami, New York, Dallas, Paris, Berlin, Rome, Munich, Madrid, Shanghai, Seoul, Tokyo, etc. are among the top target cities of every eVTOL fleet owner.
- Community Acceptance: Apart from manufacturing capacity, supply chain constraints, and delays in certification, the most crucial factor that would determine the success of eVTOLs, would be community acceptance. This will include various factors starting from the willingness of the population to spend, to the noise footprint left by eVTOLs. This is why OEMs and fleet owners are trying to keep the cost per mile as much within the affordable range as possible. OEMs like Joby, Lilium, Vertical Aerospace, etc, are all suggesting a cost/mile of <$5.
What the Future Would Look Like for This New Vertical?
The opportunities associated with eVTOLs might arrive a bit later than the currently projected timeline and that would be majorly because of the uncertain delay in receiving the appropriate certificates from the regulatory authorities. Everything else, starting from pre-orders, UAM infrastructure development, test flights, full-scale demonstrations, and the excitement among the public, is right on track.
So, while there might be some initial delay in the take-off, when the UAM revolution finally arrives, it will be an exciting one to witness.
Authored by Stratview Research, originally published in the JEC Magazine July 2023 issue.