California-based Overair has announced a strategic collaboration with Toray Composite Materials America on the utilization of Toray’s advanced prepreg system in its Butterfly prototype program.
The Butterfly is a low-noise, zero-emission electric vertical take-off and landing (eVTOL) aircraft that will provide sustainable aerial ridesharing in densely populated cities where traffic is a problem. The aircraft is a sleek and elegantly designed quad-tiltrotor aircraft. The size of the rear props has been increased compared to its previous configuration to allow the aircraft to land if one prop is damaged. Butterfly has an estimated cruise speed of 200 mph (322 km/h), a range of 100 miles (161 km), and a payload of 1,100 lb (499 kg).
Its larger, slow-turning rotor propellers provide more efficient lift, safer flight, quieter acoustics, and draw less power from batteries than aircraft with smaller propellers. This unique propulsion system requires an airframe with high stiffness and high strength while also being lightweight.
To achieve that, the Butterfly prototype aircraft will utilize Toray’s T1100/3960 prepreg system, a material that is formulated for high-performance aerospace applications where the optimal ratio of strength to modulus properties is critical. The T1100/3960 unidirectional and plain weave prepreg is utilized in the Butterfly’s airframe structure and propulsion units.
Toray’s 3960 is a highly-toughened 350°F/177°C cure epoxy resin with a glass transition temperature (Tg) of 400 degrees Fahrenheit (204 degrees Celsius). The company says the material is optimized for increased performance and allows for autoclave and out-of-autoclave curing. The resin is synergistic with the TORAYCA T1100 next-generation intermediate modulus plus (IM+) carbon fiber, which is the highest tensile strength fiber available today.
“Our unique propulsion system requires materials that provide a unique combination of high stiffness and high strength while also maintaining the optimal weight targets for the vehicle,” said Ben Tigner, Co-Founder, and CEO at Overair.
Overair recently completed full-scale testing of Butterfly’s propulsion system. The successful testing program validated Overair’s design choices and Butterfly’s expected performance capabilities. Butterfly’s propeller will be showcased at the Farnborough International Air Show from July 18 to July 22 in Farnborough, England.