Twist element for a bearingless rotor
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.
1. A twist element for a bearingless rotor, comprising a composite fiber material, having a symmetrical, flattened cross section with an outer contour of a horizontal section through the center of a double cone, wherein the cross section includes a thin root area forming a middle area, and two similar groups of webs, wherein the webs of each of the two similar groups extend from the middle area and are separated from each other vertically by narrows gaps, each gap being substantially narrower than a thickness of each adjacent web, and wherein the thickness of each web increases with increasing distance from the middle area.
2. The twist element as recited in claim 1 , wherein the webs each extend from the middle area to free lateral side edges of the twisted element and wherein the thickness of each web increases continuously from the middle area to the free lateral edges.
3. The twist element as recited in claim 1 , wherein each of the webs have a wedge-shaped cross section having a tip meeting the root area.
4. The twist element as recited in claim 1 , wherein the webs includes unidirectional reinforcement fiber packets disposed at least at an area of lateral sides of the cross-section of the twist element, each of the reinforcement fiber packets having fibers running in a lengthwise direction of the twist element.
5. The twist element as recited in claim 4 , wherein the unidirectional reinforcement fiber packets extend to the outer contour of the cross section of the twist element.
6. The twist element as recited in claim 4 , wherein the fibers of the unidirectional reinforcement fiber packets include carbon fibers.
7. The twist element as recited in claim 4 , wherein each of the webs include at least one slit in a lengthwise direction of the twist element the at least one slit extending from a free lateral side edge of the cross section of the twist element towards the root area.
8. The twist element as recited in claim 7 , wherein each of the at least one slits is configured essentially rectilinearly and wherein longitudinal axes defined by the slits pass through an area in an immediate vicinity of a center point of the cross section.
9. The twist element as recited in claim 8 , wherein the longitudinal axes intersect each other at the center point.
10. The twist element as recited in claim 7 , wherein at least one web includes at least two adjacent unidirectional reinforcement fiber packets and wherein the at least one slit of the at least one web extends between the at least two adjacent unidirectional reinforcement fiber packets.
11. The twist element as recited in claim 7 , wherein each web includes at least two adjacent unidirectional reinforcement fiber packets and at least one reinforcement fiber fabric layer disposed in an immediate vicinity of the at least one slit and between the two adjacent unidirectional reinforcement fiber packets, the at least one reinforcement fiber fabric layer extending from a lateral slit opening of the slit in a U-shaped or loop-shaped manner around a base of the slit and around a contour of the slit.
12. The twist element as recited in claim 1 , wherein at least one reinforcement fiber layer extends over a width of a first web in one of the two similar groups, over the root area, and continuously to a second web of the other of the two similar groups and over the width of the second web, wherein the first and second webs are arranged in a pair across from each other at a top and a bottom of the cross section of the twist element.
13. The twist element as recited in claim 1 , wherein the webs include lateral side surfaces that arc inclined at an angle relative to a vertical center axis of the cross section of the twist element above and below a horizontal center axis of the cross section of the twist element.
14. The twist element as recited in claim 1 , wherein the twist element forms an integral part of one of a rotor blade, a rotor blade connection element, a rotor blade joining element and a rotor head element.
15. A bearingless rotor comprising at least one twist element as recited in claim 1 .
16. A rotorcraft comprising at least one bearingless rotor as recited in claim 15 .
17. The rotorcraft as recited in claim 16 , wherein the rotorcraft is a helicopter.