Eurocopter Deutschland Gmbh

Stefan Emmerling

Horst Bansemir

Gerald Kuntze-Fechner

Ulrich Denecke

A twist element for a bearingless rotor is made mostly of composite fiber material and has a cross section with a substantially symmetric, flattened shape that has approximately the contour of a horizontal, central section of a double cone. In addition, a bearingless rotor having at least one such twist element, and a rotorcraft, particularly a helicopter, having at least one rotor with at least one such twist element are provided.

Twist element for a bearingless rotor

Active connection element for connecting at least two structural components with a first end with a first connection area assigned to the first structural component and a second end with a second connection area assigned to the second structural component, a load-diminishing intermediate section through which intermediate section the flux of force between the first and second connection areas extends when the connection element is loaded, in which at least one controllable extension actuator having at least a piezo stack is arranged parallel to the intermediate section. When operated, the piezo stack extends the connection element at least in the area of the intermediate section in a controlled manner in order to actively suppress or insulate vibrations between the structural components. A prestressing device having a prestressing element exercises a compressive prestressing onto the piezo stack.

Rod-shaped high-stress active connection element as well as rotorcraft having such a connection element

A composite structure (3) includes a piezoelectric element (1) sandwiched between fiber composite panels (2). The composite structure can be used as an actuator element. In a method for producing the composite structure, the fiber composite panels are pre-stressed and pre-strained by applying respective pre-stressing forces (F.sub.1, F.sub.2) in opposite directions along two substantially perpendicular axes in the plane of the panel. The pre-stressed and pre-strained condition of the fiber composite panels (2) is maintained, while the panels are adhesively bonded (5) surfacially onto the piezoelectric element (1). After the bonding is completed, the pre-stressing forces are removed from the fiber composite panels. As a result, in the finished composite structure (3), the fiber composite panels (2) are under internal tension, while the piezoelectric element (1) is under internal compression. The pre-stressing forces (F.sub.1, F.sub.2) are particularly selected in magnitude and direction to achieve the required resultant balance of tension and compression within the composite structure (3). The pre-compression of the piezoelectric element (1) should be sufficient so that operating loads on the composite structure do not result in tension loading of the piezoceramic element, while substantially maintaining the useful active strain range of the overall composite structure.

Growing community of inventors

Neubiberg, Germany

Stefan Emmerling