Urban Air Mobility (UAM) promises to be the next big transportation innovation. Similar to taxis or ride-sharing today, UAM will deliver transportation in the air, removing congestion from our streets and providing a convenient and rapid method to travel within urban centers. Materials will be at the heart of UAM to provide efficient, reliable, and cost-competitive transportation vehicles. Materials have been a key driver of efficiency for aircraft today, and they will be even more important for the emerging UAM marketplace.
Urban Air Mobility is focused on electric vehicles to provide clean, green, and efficient operation. Lightweight materials are key. Reducing the weight of the structure leads to increases in cargo or passenger-carrying capacity, increases the range of the vehicle, and reduces the energy required for operation, thereby improving the overall carbon footprint of the UAM. Composite materials can also be repaired when damaged, and they can be recycled when needed. Scrap from the manufacturing process can be repurposed, and the end-of-life structure can be recycled and reused. Additive manufacturing also can lead to weight reduction of the vehicle and allows complex structures to be generated with little waste and less energy than traditional manufacturing methods.
Reducing the weight of a UAM vehicle is one of the best ways to reduce the carbon footprint of the system. A good rule of thumb for airline travel is $0.01 (1 cent) per hour of operation per kilogram (kg) of weight. If the plane flies 2,000 hours per year, saving 1 kg of weight can lead to more than 3 kg of CO2 emission savings. Lower energy consumption also leads to lower operational costs, more cargo capacity, and less costly propulsion and lift systems. Carbon fiber composites are lightweight and strong, which has made them the material of choice for aerospace systems. Additive manufacturing can further reduce weight by consolidating parts, using efficient designs that only place material where it is needed and enhancing stiffness by using a carbon fiber-filled thermoplastic.
Composite structures can be repaired when damaged. Pleasure boats and yachts are generally constructed with composites and patch repairs have been used for decades to keep these systems maintained with minimal waste. Patch repair kits can be carried with the system so that repairs can be carried out whenever and wherever a UAM is damaged.
When sections are damaged beyond repair or a critical section cannot be repaired, composite materials are recyclable. Carbon fiber can be reclaimed from cured composite sections and re-used in other products. Thermoplastic composites can often be reused through heating and reforming the material. Resin systems can be pyrolyzed to recover the carbon fiber and the pyrolysis process can produce fuel which can be used to help power the pyroloysis process.
Carbon fiber composite materials have been used for primary structures in the aerospace industry for many years, and it has proven to be a safe and reliable material. In fact, carbon fiber composites require less maintenance than a metal airframe, do not corrode, and are much more vibration fatigue resistant. The acoustic performance of the UAM is also a very important consideration, both for the comfort of the passenger as well as for the urban environments where they will operate. Composite materials coupled with honeycomb core materials can be tailored to dampen much of the noise coming from engines and rotating equipment. Composite materials can also be tuned for electromagnetic frequency transmission and absorption which will be an important need for communication and sensor systems that will be part of these systems.
Qualified for Aerospace
Carbon composites and honeycomb core systems have been used in aerospace vehicles for more than 50 years and are well understood. New generation commercial airplanes are constructed with 50% carbon composites by weight. Carbon fiber composites are selected because of their excellent stiffness and strength and low weight so they are the ideal choice for UAM where strength, stiffness, and weight will all be important. The extensive experience in using composites for aerospace can be relied on for the emerging UAM market.
Composites coupled with honeycomb core systems have been used for decades to dampen the noise coming from jet engines. New honeycomb core systems are further reducing the noise in aviation systems and can be used to dampen noise in electric drive and rotor systems. Composite stiffness can be modified and controlled throughout the structure to dampen vibration and provide for a smoother and quieter ride. A quiet UAM system will be key if these systems are to be operated extensively in urban environments.
Antennas and communication systems will be critical for the safe and efficient operation of UAM systems. Radomes are used to protect the antennas, and they are made with composite materials that provide protection from the environment with electromagnetic transparency. With the increasing use of sensors and communication systems that will be required for UAM, a lot of electromagnetic signals will be in the airspace. Composite radomes can be tuned for selective frequencies which will allow UAM communication systems to target just the frequencies they need and filter out the undesired electromagnetic signals.
As the UAM market develops, the number of vehicles produced will exceed current aircraft and rotorcraft volumes of today and will start to approach automotive vehicle production. Automotive production methods require very high capital and tooling costs and only make economic sense for very high-volume production platforms. Composite materials require much less capital equipment and less tooling which means they can be used for small volume production and then can scale up with more automation. Manufacturing technologies such as robotic lay-up and assembly, infusion and compression molding, and additive manufacturing bring more automation to the process. Faster cure and processing of materials provide higher rate production systems while still maintaining quality and performance. The scalability of composites makes it the right material to get started and the right material for higher volume production.
As the UAM industry develops and grows, it will need scalable manufacturing processes than can grow efficiently with the market. Small lot production of composite structures can be carried out with minimal capital investment. Composite structures can be laid-up by hand with simple and low-cost tooling and can be cured with simple ovens.
As production volumes increase, composite manufacturing can be automated. For most aerospace manufacturing today, robotic systems are used to lay down the material on a tool and the material build-up, inspection, and post-processing can largely be automated. This allows cost per part to be reduced as the production volume increases. Infusion and compression molding can be used where large, integrated structures can be created with dry fiber preforms and then infused and cured in a single operation. Additive manufacturing is a fully automated technology that can create structures that are unique and efficient.
With the ability to scale manufacturing as the market develops, composite materials also lend themselves to distributed manufacturing where the vehicles can be produced in smaller lots but closer to where the vehicles will be used. Since high capital equipment costs are not needed, companies can create a series of micro-factories that allow them to reduce risks, move factories closer to the market demand, and create an agile production system that is flexible and affordable.