US Patent 9657577 Rotor blade with bonded cover

An airfoil comprises an airfoil body with an internal cavity and inner and outer covers. The airfoil body defines a first major surface of the airfoil, and a rib extends along the internal cavity. The inner cover is bonded to the airfoil body over the internal cavity, and includes a coupling element extending along the internal cavity in cooperative engagement with the rib. The outer cover is bonded to the airfoil body over the inner cover, and defines a second major surface of the airfoil.