DE3244725C1 - Rotor blade made of fiber composite plastic - Google Patents

Description

The invention relates to a rotor blade made of fiber-reinforced plastic, at least in the blade root area for connection to a rotor hub in the manner described in the preamble of claim 1

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In such a rotor blade known from DE-OS 30 06 088, the fiber structure is the Blade root provided with layers of fiber loops wrapping around the blade angle bearing under the Assumption that with regard to the tensile stresses in the direction of the centrifugal force of the blade in the blade root area cannot do without the - due to the loop shape - endless fiber strand. The loop-shaped one However, fiber strand requires a considerable manufacturing effort because it is used for manual fiber laying techniques.

The invention is therefore based on the object of a rotor blade of the type mentioned at the beginning To do without fiber loops in the leaf root area without reducing its strength.

According to the characterizing part of claim 1, this object is achieved by a quasi-isotropic Fiber structure of the individual cross-fiber layer, which is caused by the proposed change in fiber orientation with the consequence of a reduction in the fiber angle difference in the cross-fiber layer plane not only - through the blade angle bearing and the connection bores made for this purpose - conditional interruptions of the able to bridge the respective unidirectional fiber layer, but also in turn to accommodate high embedment forces. This is explained below using an exemplary embodiment of Invention and the preferred embodiments characterized in the subclaims further clarified. The drawing in

F i g. 1 is a perspective view for a rotor blade connection on a rotor head of a rotary wing aircraft components associated with one another;

FIG. 2 shows an enlarged vertical longitudinal section through the blade root of the rotor blade according to FIG. 1;

F i g. 3 shows, in an exploded view, one of the cross-fiber layers according to FIG. 2 multi-layered leaf roots;

4 one of the unidirectional fiber layers of the multilayer Leaf root according to FIG. 1 or 2.

According to FIG. 1 is a star-shaped rotor head 1 with (for example) four blade holders 2 to 5 are provided, each in the form of a fork radially outwards extend. To connect the respective rotor blade or its blade root 6 to the associated blade holder 2 is an axial-radial elastomer bearing 7, which in which the leaf root 6, which is formed into a tab with a corresponding eye 8, is installed. While this axial-radial elastomer bearing 7 has the function of a absorb the centrifugal forces of the blades, d. H. pressure-resistant, but allowing blade rotation angle movements Connection between the blade root 6 and the two fork legs of the associated blade holder 2 fulfilled, a radial elastomer bearing 9 seated at the root of the same has only a support function; simultaneously its blade root-side bearing part 9.1 can be used to link a blade control lever.

For this blade connection, dispensing with the otherwise usual blade fittings, the rotor blade resp. in particular the leaf root 6 of which is provided with a multilayer structure made of fiber-reinforced plastic, for example glass fibers in a synthetic resin matrix. This follows from the outside to the inside as shown in FIG one layer alternating in layers on a layer 10 of fibers in a crosswise orientation to the longitudinal axis of the blade 11 of fibers in a unidirectional orientation to the longitudinal axis of the blade, with at least two cross-fiber layers

10 with an interposed unidirectional fiber layer

11 are to be selected. The difference in the fiber structure of these in FIG. 3 and 4 shown separately Fiber layers 10 and 11 are due to the different causes of the leaf root stress on the one hand justified, namely both centrifugal forces and bending moments from the blade flapping and blade pivoting movements. In order to simplify production in the unidirectional fiber layers 11 without Fiber loops around the leaf root eye 8 are used for the cross fiber layers 10 (cf. in particular FIG. 3) Thickness according to an alternating fiber orientation selected in such a way that, starting from the respective unidirectional fiber layer 11, in the direction of the outside of the sheet, the individual cross-fiber ply 10 has a fiber layer structure of at least one first layer 10.1 with 90 ° / 0 ° fiber orientation (to the longitudinal axis of the blade), a second Layer 10.2 with ± 45 ° fiber orientation, a third layer 10.3 with + 45 ° fiber orientation and one fourth layer 10.4 with 0 ° / 90 ° fiber orientation (in the transition to the next unidirectional fiber layer 11). This mirror-symmetrical fiber layer structure, in which in the individual cross fiber layer 10 from the outside inwards each to a fiber orientation in

Right angle to the longitudinal axis of the blade, at least one crosswise fiber orientation with a fraction (im Example with half) this fiber angulation follows, has the advantage already highlighted above small fiber angle difference in the fiber layer plane overall. The individual cross-fiber layer is thus 10 particularly capable of compensating for the unavoidable weakening of the unidirectional fiber layers 11 through the eye 8 and connection bores 12 (of the elastomeric bearings 7 and 9); here meet two Cross fiber layers 10 have an excellent bridging function between the interrupted fiber strand sections the intermediate unidirectional fiber layer 11. The single cross fiber layer is at the same time 10 particularly highly resilient due to embedding forces. Since all fiber layers 10 and 11 are easily machined are reproducible, the rotor blade can be manufactured particularly economically.

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Claims (3)

Patent claims: 1. Rotor blade made of fiber-reinforced plastic, at least in the area of the blade root, in particular for Rotors of rotary wing aircraft, for connection to one on the rotor hub radially outwards extending, fork-shaped blade holder via a blade angle bearing that can be subjected to pressure in the longitudinal direction of the blade, which is in the leaf root, which is formed into a correspondingly perforated flap is installed, characterized in that the respective fiber-reinforced plastic sheet area (6) a fibrous structure of at least two layers (10) each of fibers in relation to the longitudinal axis of the blade crosswise orientation and unidirectional from an interposed layer (11) of fibers Has orientation to the longitudinal axis of the blade with changing fiber orientation in the individual Cross fiber layer (10) in such a way that in it from the outside to the inside on a fiber orientation in the right Angle to the longitudinal axis of the blade at least one crosswise fiber orientation with a fraction, preferably with half of this Faserwinkelüng follows. 2. Rotor blade according to claim 1, characterized by a mirror-symmetrical fiber layer structure the individual cross fiber layer (10). 3. Rotor blade according to claim 1 or 2, characterized in that of the respective unidirectional fiber layer (11) in the direction of the outside of the leaf, the individual cross-fiber layer (10) has a fiber layer structure comprises a first layer (10.1) with 90 ° / 0 ° fiber orientation, 'a second layer (10.2) with ± 45 ° fiber orientation, a third layer (10.3) with + 45 ° fiber orientation and one fourth layer (10.4) with 0 ° / 90 ° fiber orientation.