Composite Materials for Hybrid Aerospace Gears

Hybrid steel-composite gears, which combine steel teeth with a fiber-reinforced polymer composite core, are a rapidly emerging technology for weight reduction in aerospace drivetrain systems. However, power transmission gears—and especially the requirement of rotorcraft gearboxes to operate under loss of lubrication—are a very challenging application for composite materials, due to the combination of mechanical and thermal loads. In this work, composite materials, including newly developed hybrid laminates featuring multiple grades of carbon fiber, are fabricated. Mechanical and thermal testing, along with ply-level finite element analysis, are employed to assess the suitability of these composite materials for hybrid aerospace gear applications. Particular focus is given to high-temperature epoxy and bismaleimide resins and to hybrid laminates reinforced by multiple grades of carbon fiber. This hybrid drivetrain technology would manifest significant weight reductions without compromising gear performance.