Development of a High Torque Density, Flexible, Composite Driveshaft

An all-composite driveshaft incorporating integral flexible diaphragms is described. An approach was explored which obsoletes the split lines and associated fasteners required to attach metallic flex elements and either metallic or composite spacing tubes in current solutions. Sub-critical driveshaft weights half that of incumbent technology are projected for typical rotary wing shaft lengths. A description of the trade-off required between axial, bending, and torsional stiffness plus torque density and manufacturability is provided. Fully anisotropic material properties were mapped to the deeply sculpted diaphragm geometry and a parametric, numerical study of the complex shell undertaken. Spacing tubes are described, which comprise an integral part of the initial tooling but which remain part of the finished shaft and control natural frequencies and torsional stability. A concurrently engineered manufacturing process and design for performance is described which competes with incumbent metal solutions at lower weight and with the probability of improved damage tolerance and fatigue life.