Abstract: A method of making a rotor yoke includes preparing a cured composite rotor yoke preform on a single-sided curing tool and machining at least one portion of the cured rotor yoke preform to form a rotor yoke. In one embodiment, preparing the cured composite rotor yoke is accomplished by applying successive layers of uncured polymeric composite material to a single-sided tool in a configuration to produce an uncured rotor yoke preform; disposing a semi-rigid caul to an untooled side of the uncured rotor yoke preform; enclosing the uncured rotor yoke preform and the semi-rigid caul by substantially hermetically sealing a vacuum bag to the tool; substantially evacuating a volume defined by the vacuum bag and the tool of air; and heating the uncured rotor yoke preform, sometimes under pressure, to form the cured composite rotor yoke preform.

Abstract: A helicopter rotor blade includes a structural composite skin defining a cavity therein; a composite spar disposed within the cavity and adhesively bonded to the skin, a portion of the spar exhibiting a C-shape in cross section; and a foam core disposed within the cavity and adhesively bonded to the skin. The structural composite skin forms an external, closed box structure configured to transmit mechanical loads encountered by the rotor blade.

Abstract: A rotor blade of a helicopter is presented. In an embodiment, the rotor blade includes a body; and a heating mat arranged in the body and configured to supply heat to said body. The heating mat includes a first plurality of fibers and a second plurality of fibers electrically connected to the first plurality of fibers. The first plurality of fibers define a positive angle smaller than about +45° relative to a first direction perpendicular to a longitudinal direction of the body. The second plurality of fibers define a negative angle greater than about ?45° relative to the first direction.