Past, Present and Future Composite Structures Applications in Rotorcraft

Abstract

The rotorcraft industry is a roughly $5B/year segment of aerospace, with a 4:1 military to civil sales ratio, that delivers on the order of 5000–6000 aircraft per year. The earliest rotorcraft had composite primary structure: bonded wooden main and tail rotor blades. The first advanced composite main rotor (M/R) and tail rotor blades (bonded glass/epoxy D-spars, honeycomb afterbodies, and fabric skins) went into production in the early ’70’s. Thus, the rotorcraft industry has been designing and certifying nonredundant bonded primary composite structure for over 25 years. More recent design innovations for rotor components include 4-inch-thick solid molded bearingless M/R hubs and yokes (joining the blades to the mast) and a 1.5-inch-thick complex curvature fiber placed carbon grip for the Bell/Boeing MV-22 Osprey tiltrotor. With roughly 50% of its empty weight consisting of glass and carbon reinforced composites, the V-22 probably has the highest weight-percentage of composites of any manned military production aircraft. This degree of composites usage will likely be surpased by the Sikorsky/Boeing RAH-66 Comanche scout/attack helicopter when it goes into production. As with the V-22 and RAH-66, composites are also seeing increased usage in civilian rotorcraft airframes. Specifically, the Bell 427 and MD Helicopter MD900 Explorer light twin helicopters feature all-composite fuselages, while the Bell-Agusta BA609 civil tiltrotor will have carbon epoxy wings, fuselage and empennage much like the V-22. In the future, composite structural applications will become more widespread as designers gain insight and confidence. Repair, maintenance and support of these structures will become the focus of much engineering R&D effort.