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 .