Design, Fabrication and Testing of a Composite Drive Shaft with an Integral Misalignment Feature

In helicopters, the drive shafts are critical components that transfer power from the engines to the main and tail rotors. One of the challenges for the design is to address the relative deflection of the airframe structure to the drive shaft, which results in cyclic misalignment in the drive shaft. The resultant misalignment is a source of cyclic loading and requires a distinct feature to provide a misalignment capability. Current technology uses metallic couplers in the shape of a bellows or flat plates that allow local misalignment. This paper will discuss the technical challenges and issues associated with development and incorporation of a misalignment feature into an integral composite drive shaft. Five topics will be covered: design, structural analysis, material selection, fabrication and structural testing. The design section will focus on the design challenges associated with development of an integral composite shaft. The structural analysis section will cover critical analyses performed during this program. Material selection will address the selection criteria and relevant allowable development. Fabrication issues covered will provide an over view of the manufacturing process and major technical challenges. The final portion will discuss the structural testing performed on the shaft, including static, non-rotating fatigue and rotating fatigue testing.