Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: An impact-absorbing, load-limiting connection device includes a first connection structure, a second connection structure, a guiding mechanism, and at least one impact-absorbing, load-limiting sacrificial element disposed between the first and second connection structure. At least one of the first and second connection structures is moveable with respect to the other in a predetermined direction of movement corresponding to an anticipated main impact direction. The guiding mechanism is configured to guide at least one of the first and second connection structures along the direction of movement and includes at least one transverse force-absorbing guide element configured to absorb a force in a direction transverse to the direction of movement.

Abstract: An impact-absorbing, load-limiting connection device includes a first connection structure, a second connection structure, a guiding mechanism, and at least one impact-absorbing, load-limiting sacrificial element disposed between the first and second connection structure. At least one of the first and second connection structures is moveable with respect to the other in a predetermined direction of movement corresponding to an anticipated main impact direction. The guiding mechanism is configured to guide at least one of the first and second connection structures along the direction of movement and includes at least one transverse force-absorbing guide element configured to absorb a force in a direction transverse to the direction of movement.

Abstract: A subfloor structure of an aircraft airframe, particularly of a helicopter, includes longitudinal beams and crossbeams that intersect each other and are interconnected to form a grid that is fixedly attached to the floor and the bottom skin of the aircraft fuselage. Structural elements such as pyramid frustums and reinforcements are arranged on the beams. The longitudinal beam and the crossbeam have a trapezoidal cross-section that is preferably open on the wider base side, closed by a spine web along the narrow side, and bounded laterally by inclined leg webs that extend downwardly from the spine web at an angle outwardly relative to each other. The subfloor structure grid effectively absorbs the energy of a crash impact having both axial or vertical as well as non-axial or lateral impact force components.

Abstract: A helicopter gimbal rotor arrangement includes a drive shaft with a rotor hub, a rotor blade holder arrangement, and a coupling membrane for transmitting the rotational drive moment from the rotor hub to the rotor blade holder arrangement. The coupling membrane includes a plate element made up of a plurality of concentric rings that are spaced apart radially by annular gaps and are connected to each other by respective connecting webs spanning across the gaps. This plate element as the coupling membrane provides torsional stiffness combined with bending flexibility to allow tilting motions of the rotor blade holder arrangement relative to the rotor hub. Plural plate elements connected in parallel provide a redundant fail-safe arrangement, while plural plate elements connected in series achieve increased flexibility for out-of-plane tilting.

Abstract: A spring component for support bearings of helicopter tail rotors or for support structures for use in outer space encompasses at least two contact support components (11a, 11b) for connecting with the members that are to be supported (e.g. a belt and a control sleeve of a helicopter tail rotor), as well as a web plate (20), which extends between the contact support components (11a, 11b) and which includes a pair of lengthwise webs (21a, 21b) extending in a longitudinal direction. The lengthwise webs are connected to each other by first connecting webs (22a, 22b). Respectively, a further connecting web (23a, 23b) is arranged at a section of the two lengthwise webs (21a, 21b) positioned between the first connecting webs (22a, 22b), wherein each further connecting web extends outwardly toward one of the support components (11a, 11b). In connection with a transverse bending moment acting on the spring component, a twisting of the lengthwise webs (21a, 21b) takes place.

Abstract: Apparatus for damping vibrations of a structure such as the air frame of a helicopter wherein a spring system (1), which has an elastic wall structure forming a tube-shaped hollow body supports a weighted vibrating object (23). At least one region of the wall structure is constructed to be elastically deformable in its plane, with a spring stiffness, tuned to the frequency of the vibration to be damped. The wall structure is formed by several planar spring elements (11a, 11b, 11c, 11d), each of which can be elastically deformed in its plane by an arrangement of longitudinal strips (110a, 110b, 111a, 111b) and connecting cross pieces (120a, 120b, 121a, 121b). A battery of the helicopter can be used as the vibrating weight (23). The vibration damper containing the battery is installed at a location on the helicopter where clear structural vibrations occur in two directions perpendicular to each other and wherein the vibration damper is tuned to the vibrations frequencies in both directions.

Abstract: A helicopter gimbal rotor arrangement includes a drive shaft with a rotor hub, a rotor blade holder arrangement, and a coupling membrane for transmitting the rotational drive moment from the rotor hub to the rotor blade holder arrangement. The coupling membrane includes a plate element made up of a plurality of concentric rings that are spaced apart radially by annular gaps and are connected to each other by respective connecting webs spanning across the gaps. This plate element as the coupling membrane provides torsional stiffness combined with bending flexibility to allow tilting motions of the rotor blade holder arrangement relative to the rotor hub. Plural plate elements connected in parallel provide a redundant fail-safe arrangement, while plural plate elements connected in series achieve increased flexibility for out-of-plane tilting.

Abstract: A sandwich composite panel (2) provides a load bearing structural member as well as noise protection, especially for a helicopter fuselage cell or cabin. The panel (2) includes an inner honey-comb core (6) made up of hollow cell bodies (4) extending trans-versely and sandwiched between first and second cover skins (8, 10) of fiber composite material. In order to achieve a low weight, a simple manufacturing, and good noise absorption, at least one of the cover skins (8) adapted to face the main source of noise (H) is made up of an open mesh fiber composite net (12) and a flexible cover film (16) applied on the outer surface of this fiber composite net (12). The net (12) has a smaller mesh size than the inner cross-sectional size of the hollow cell bodies (4).

Abstract: 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.

Abstract: A multi-blade rotor arrangement free of flapping hinges, for a rotary wing aircraft, includes a rotor head plate (2) made of fiber-reinforced composite material. The head plate (2) includes a plurality of blade connection arms (4) that are elastically flexibly bendable in the blade flapping direction, and at least one plate segment (16, 18) that holds each blade connection arm on two sides thereof radially spaced away from the rotor center in a manner that allows elastic bending in the blade flapping direction. The plate segment is rigidly connected to the rotor mast (122, 222) at mounting locations (20) that are offset in the circumferential direction from the blade connection arms. In this manner, the elastically yielding flapping connection between the rotor blades and the rotor mast is provided by both the elastic bending of the blade connection arms and the elastic deformation of the plate segment portions between the blade connection arms and the mast mounting locations.

Abstract: A mass damper for a dynamically excited part including a housing connected in a vibration-free manner with the part and a spring-mass system that can vibrate in the direction of the excitation of the part. The spring-mass system comprises a leaf-spring arrangement tensioned firmly to the housing on one side and provided on the other side at the free spring end with an inertial mass. Resonance adjustment is performed in a structurally simple and problem-free manner, solely by control interventions on the housing side and without mass shifts in the spring-mass system. The inertial mass is permanently connected with the free end of the leaf spring, and, in the vicinity of the tensioning point or at a distance from the point, a variably adjustable leaf-spring support for adjusting the resonant frequency is provided with variable tensioning geometry or internal stiffness.

Abstract: The helicopter rotor blade connection has a support beam which connects the lift-generating wing section of the rotor blade with the rotor hub, and transmits centrifugal and lateral forces as well as bending and torsional moments. The connection is torsionally elastic and, at least in a main plane, bending elastic. A damping device for damping bending vibrations of the support beam is constructed alternately of elastomer layers and intermediate layers which are stiff in the direction of their extension. According to the invention, the damping device consists of a plurality of separate individual dampers which are arranged with their elastomer and intermediate layers in the direction of the main bending plane of the support beam.

Abstract: A solar generator for use in satellites or spacecraft includes a plurality of solar cells mounted on a support structure panel. The support structure panel includes a honeycomb cell structure core (4) sandwiched between a bottom cover skin (5) and a top cover skin (2). Vibration damping elements (11) are incorporated and bonded into the honeycomb core, and vibration damping film strips (10) are adhesively bonded onto an outer surface of at least one of the outer cover skins. The damping elements (11) respectively include a damping ring (13) made of an elastomeric material, between inner and outer structural rings (14, 12), whereby the outer ring is bonded to the honeycomb core and the inner ring provides a mounting location. The damping film strips are positioned at locations of maximum vibrational excitation in the panel due to noise pressure loading.

Abstract: In the case of a rail wheel having a wheel disk made of plastic and a tire made of metal, these are connected with one another by way of a metallic intermediate ring onto which the tire is shrunk. In this case, the wheel disk has a conical cross-sectional profile on its circumference and the intermediate ring, which is form-locking therewith, is axially divided into two partial rings with a correspondingly partially conical interior surface. The partial rings are in a mutual force-locking connection and are glued to the wheel disk. This ensures a double safety connection between the intermediate ring and the wheel disk.

Abstract: The invention relates to a tubular member, especially for safety steering columns for motor vehicles, made of wound fiber-reinforced materials. The winding angle of the fibers or fiber belts amounts to essentially .+-.45.degree. relative to the tube's longitudinal axis. For taking up high torsional moments and simultaneously low compressive and buckling or bending loads, the tubular member (1) has an expanded outwardly bulging section (3) extending around the entire circumference of the tubular member. This bulging section is preferably a double conical outward bulge. The fibers (2) cross each other at an angle of essentially 90.degree. even in the region of the outwardly bulging section (3), which means that the winding angle of essentially .+-.45.degree. to the tube's longitudinal axis is maintained in the region of the outwardly bulging section (3).

Abstract: A carrier membrane supports area covering solar cells and, preferably, is used for energy supply on a spacecraft. The membrane is stretched in a frame between two opposite sides and consists of plastic sheeting covered by a fiber-reinforced plastic fabric. To save weight, prevent insulation problems and thereby increase service reliability, the fabric is made of plastic reinforced with aromatic polyamide fibers in the form of woven crossing bands. The bands extend in the direction in which the membrane is stretched and transversely of the stretched direction.