SPAR FOR DUCTED-ROTOR AIRCRAFT

An annular spar for a ducted-rotor of an aircraft may be fabricated from composite material, such as carbon-fiber-reinforced plastic (CFRP). The spar may include an annular plate, a first circumferential flange that extends from an outer edge of the plate, and a second circumferential flange that extends from an inner edge of the plate. The first and second circumferential flanges may taper inwardly toward a center axis of the spar. The spar may be constructed of a plurality of layers of CFRP. One or more of the layers may be fabricated from a single ply of CFRP, and one or more other layers may be fabricated from a plurality of plies of CFRP. The spar may exhibit a coefficient of thermal expansion (CTE) that allows an associated tip gap to remain essentially constant throughout a range of operating temperatures.