An all-composite driveshaft incorporating integral flexible diaphragms is described and proposed for further refinement. An approach is 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. 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 proposed which competes with incumbent solutions at significantly lower weight and with the probability of improved damage tolerance and fatigue life. This phase I proposal seeks to further remove manufacturing cost and to produce test articles suitable for concept verification and, subsequently, flight qualification during phase II.
