HU230887B1 - Helicopter rotor blade - Google Patents

Description

Helicopter rotor blade

The present invention relates to a fiber-reinforced composite helicopter rotor blade for light and ultralight helicopters. The helicopter rotor blade of the present invention has a hollow main carrier, an inlet edge and an outlet edge forming the blade body.

Passenger helicopters used to have wooden hollow rotor blades, which were first covered with impregnated canvas. These rotor blades, or rotors, have been shown to be vulnerable and therefore dangerous. Subsequently, the use of light metals such as aluminum and its alloys and titanium in the rotor blade industry has become more widespread due to its lower risk of accident and partly due to its advantages in mass production.

The structure of the rotor blades and the. The materials used to make them are determined by the static and dynamic forces exerted on the finished blade. Rotor blades are subjected not only to centrifugal force due to rotation, but also to complex movements due to helicopter control. That's why the metal rotor blades would! fatigue fractures can occur, and corrosion of metals can cause dangerous damage. This results in blades of such a structure having to be replaced after a certain period of time, even if apparently flawless, under constant visual inspection. Not only do such blades have a definite life span, but their manufacture is also a complex process involving many steps.

Advances in composite materials have also made it possible to use them in the production of rotor blades. The advantage of using composite materials is that they have virtually no "turnaround time" ⁷ , ie no corrosion problem and no fatigue! the resulting malfunction is also significantly reduced. This means that the life of composite rotor blades is significantly extended. They can be used practically until they are mechanically damaged. An example of such a solution is GB 1 438 184 (A), in which the main support of the rotor blade is glass fiber reinforced.

SZTNH-100115159 is made from a composite by gluing together three, approximately U-shaped, individually manufactured components in complex steps.

GB 1 438 184 A (Kamov et al., May 25, 1973) discloses a process for making load-bearing components of helicopter rotor blades. The load-bearing elements of the rotor blades have a hollow cross-section. In the manufacturing process, the hollow bodies are made of at least two parts by placing resin impregnated tissue sheets on a slightly tapered tool. The outer surface of the tool corresponds to the inner surface of the hollow load-bearing elements. The resin impregnated tissue patches placed on the tool are then pressurized by covering and sealing with an elastic bar or foil, and then, after the air has been aspirated, atmospheric pressure presses the impregnated layers onto the tool. In the next step, the component is partially cured by heat treatment. The sufficiently rigid U-shaped parts thus obtained are placed in one half of a tool with an inner surface to lay another layer of impregnated tissue with the opposing U-shaped parts to form the hollow load-bearing component of the rptor blade. In the meantime, a flexible hose is placed between the U-shaped parts, the tool halves are sealed, the fluid is pressed into the hose and pressed into the tool wall to impregnate the impregnated layers and heat cure to completely seal the rotor blade thus formed. The load bearing member forming the first half of the rotor blade is then attached to the composite blades of the rotor blades. with a honeycomb structure sandwich material completely filled out. (Figure 1-3)

SU 431733 A1 (Kamov et al., May 27, 1953) also discloses methods for making rotor blades and their rails. In a process similar to the Kamov process described above, except that the impregnated layers are pressed against the tool wall using a fluid pressure rather than a liquid. (Figure 4)

The disadvantage of the rotor blade according to the above patents is that the main support is made up of several parts. Therefore, in order to achieve sufficient strength, a larger number of layers and, consequently, a greater amount of material must be used, which results in weight gain.

GB 2 148 820 A discloses a helicopter rotor blade made of a composite material, the first main support of which is hollow and is made by winding from fiberglass and synthetic resin. This is built into the body of the rotor blade. The back of the blade (leading edge) consists entirely of honeycomb sandwich material, which is covered with a laminate composite material. The disadvantage of the main roll produced by winding is that it has to be made thicker in order to achieve the required amount of bending and tensile strength, which results in additional material usage and consequently weight gain. The reason for this is that the fiber directions of the fiberglass are not in the direction of the resulting stresses and thus cannot fully absorb the loads.

The leading edges of the rotor blades described above are protected from damage by a sheet metal cover. Metal sheeting, on the other hand, is more prone to icing and therefore it is imperative to install a heating rod.

Detailed Description of the Invention;

Description of illustrations:

Figure 1 (GBGB 1 438 184 A); Shows the alignment of the leading edge of the rotor blade and its main components. The figure shows that the main bracket is glued together from two halves, to which the plywood entry edges are glued.

Figure 2 (GB 1438 184 A): Shows a layering of one half of the main holder onto a tool core. This is sealed with foil and sucked in air.

Figure 3 (GB 1 438 184 A): Shows a die tool in which the joint shown in Figure 1 is glued together.

Figure 4 (SU 431733 Al): Shows the gluing of the elements placed and assembled in the die tool. The figure shows that the assembled elements are clamped to the tool surfaces by means of a hose blown with compressed gas.

Figure 5 (according to the invention): The figure shows the parts a, b, c of the tool, the sheet steel la, the flexible hose 1b and. Laminated layers.

Fig. 6 (according to the invention): shows the main holder 1, the inlet edge 2, the hollow part 2a, the outgoing edge 3 reinforced with honeycomb stiffeners 3, and the gluing surfaces 4 disposed in the mold and forming part or all of the rotor blade.

Figure 7 (according to the invention): Shows a rotor blade tip preferably formed in a drop shape.

Fig. 8 (according to the invention): A perspective view of the complete rotor blade. The figure shows the location of the leading edge 2, the main holder 1, the exit 3 and the connecting element 5 connecting the rotor hub and rotor blade on the rotor blade.

4.-

It is an object of the present invention to provide a rotor blade for light and ultralight passenger helicopters that is resistant to corrosion, a high strength rotor blade that is resistant to various forces in helicopters, and lighter than conventional blades. It is a further object of the present invention to provide a relatively simple production process. The rotor blades of the present invention were developed for a two-blade (semi-rigid) helicopter rotor hub.

The big difference between two-blade (semi-rigid) and multi-blade (self-adjusting) connections is that while the former is rigid (in the rotation plane), the multi-blade rotor hub has a self-adjusting blade connection. In the case of a self-aligning joint, the rotor blade can bend back and forth ("sword distortion") or move (so-called "mat movement") within certain limits, as well as limited movement perpendicular to the rotation plane (so-called flapping motion). While the double-blade system has the disadvantage of "sword deformation, it is permissible in self-alignment. The air resistance at the forward blade is greater than that at the rear (lack of thread speed), so the deflection is also different and the two coefficients deflect the rotor hub from the center of gravity passing through the center of the main propeller shaft and, as a result, vibrate. Requirements for two-blade rotor blade connections could be satisfied only by the use of additional material according to the state of the art patents.

The newly developed rotor blade, due to its structural design, eliminates the aforementioned disadvantage. Despite its low weight, it is corrosion-resistant and high-strength, meeting all aviation requirements. The leading edge 2 and the front surface of the main holder 1 together form a stiffening triangle to reduce or eliminate sword distortion of the rotor blade in the rotational plane at low weight and low material utilization, which causes the major problem of the half rigid rotor hub. The triangle thus formed with the leading edge also greatly reduces the vulnerability of the main carrier 1, especially when filled with a sufficiently rigid hard foam. The entry edge area is also ideal for installing anti-icing heating wire and blade tip lighting wires. However, it should be noted that the leading edge of the rotor blade of the present invention is much less susceptible to icing than conventional ones, and therefore it is not generally necessary to install a heating filament at the leading edge.

-5Dimensions of the rotor blade according to the invention:

Length: 2800 ~ 4000 mm

Maximum weight:

Minimum weight:

7..2 kg + 1.8 kg balancing weight (lead)

4.6 kg + 1.6 kg balancing weight (lead)

Maximum width:

230 mm

Minimum width:

160 mm

Other advantages of the rotor blade we have developed are that it is equally suitable for low (symmetrical) profile, right (Anglo-Saxon) and left (French) rotation, also suitable for coaxial rotors,

It also achieves a circumferential speed of 230 m / s (828 km / h), low air resistance, quieter mode, low profile access and excellent bending indexes, thanks to the special main carrier fabric layering that provides foam energy and vibration absorption as well as injury main body protection.

The above objects have been achieved by using a high strength composite material to produce the rotor blade of the present invention. The rotor blade is made up of three main parts: 2 leading edges, 1 main carrier and 3 leaving edges. The rotor blade has 2 inlet edges, 1 main holder and 3 outlet edges bonded with a high strength adhesive, preferably an epoxy resin adhesive. The main holder 1 of the rotor blade is formed at the end towards the rotor hub to receive a connector for securing the blade to the hub (Fig. 8).

Biaxially arranged fabrics, unidirectional (UD) roving fabrics known in the art, including glass, caviar, carbon or metal fibers, are known for use in fiber reinforcement. Known synthetic resins, such as unsaturated polyester resins, vinyl resins or epoxy resins with various crosslinking, are suitable for laminating. Glass fiber and glass roving are preferably used for fiber reinforcement. Preferably, the synthetic resin is an epoxy resin with an amino-type crosslinker. The advantage of fiberglass over carbon fiber and carbon fiber is that it is less prone to electrical charge.

The incoming edge 2 is made by laminating resinous glass onto the inner surface of a custom mold with 4-8 layers of biaxially arranged fiberglass and then partially or completely cured off at room temperature or elevated temperature so that it can be lifted out of the mold morphologically.

During the manufacturing of the main holder 1, a so-called UD roving fabric is laminated in one direction with a synthetic resin to form the core of the main holder so that 18-23 layers are applied to the largest cross-section of the finished main holder and 10-15 layers gradually reducing the number of layers. . The tool core is configured so that after the composite material has cured, the core can be pulled out of the finished main support bar 1. In the present invention, this is accomplished by forming a die core from a sheet of steel la having a width approximately equal to, but not exceeding the width of the main support, onto which an elastic hose 1b, preferably a silicone hose, is pressed against the inner surface of the main holder. The UD roving fabric is externally deposited on the die core while conventionally impregnating the roving fabrics of the laminates with epoxy resin. UD roving fabric can be used to produce a main carrier having a significantly higher tensile-bending strength, even at a lower weight than conventionally manufactured main supports. At the end of layering, the layers extending over the tool core are dewatered onto the tool core and inserted into the sealable tool shown in Fig. press the laminated layers 1c of resin impregnated roving fabrics (Fig. 5a). The excess laminating resin formed in the tool and allowed to flow through the resin channel is then cured at room temperature or elevated temperature in a known manner to cure the composite main holder. The length and cross-section of the rotor blade and main carrier 1 will, of course, depend on the size of the helicopter, its payload and other circumstances to be considered in the design of the helicopter. The rotor hub end of the main holder 1 of the present invention has a cross section that is capable of accommodating the end of the coupling member for attaching the rotor blade to the rotor hub. Of course, these will be determined by load calculations and experimentation by one of ordinary skill in the art.

In the preparation of the rear exit edge 3, a biaxial glass fabric is laminated to the inner surface of the two moldings formed in accordance with the lower and upper cover surfaces 3a and 3b with a laminar resin 3c with a Kevlar honeycomb stiffener. This honeycomb does not completely fill the cavity between the lower surface 3a and the upper surface 3b of the exit edge 3 of the finished rotor blade. The laminates, i.e. the fabrics impregnated with the synthetic resin, are partially or completely expanded at room temperature or at elevated temperature to remain in shape.

Optionally, in a similar manner to the above, a drop-shaped end member is provided by lamination, partially or fully cured, for positioning on the end of the rotor blade. Alternatively, the outer ends of the lower and upper faces of the exit edge may be formed during lamination to form a drop shape. The use of a drop-shaped end or end member significantly reduces the noise generated by the rotor blades.

Subsequently, in one of the halves of a heat treatment die (6, Fig. 6), the partially or partially deflected leading edge 2, the outer end of which is mechanically and / or mechanically applied to its outer and outer edges, is uniformly coated with high-strength adhesive resin. gluing the flatter weight or weights, and insertion of the lower and upper backs 3a of the outermost or partially meshed, and reinforced honeycomb stiffener 3c. In the case where a separate drop-shaped finishing element is used, it is also placed in the mold by applying a high-strength adhesive resin to the mating parts 4. Preferably, the foamable liquid resin forming a hard foam, preferably a foamed epoxy resin, is filled into the hollow portion 2a formed between the leading edge and the main holder before the two tool halves are sealed. The two. sealing the die half, first curing the rotor blade containing the adhesive and optionally partially cured components at room temperature and then at elevated temperature, and then removing it from the tool. Optionally, after removal from the tool, fill the hollow portion 2a formed between the inlet edge and the main holder with a foam forming foam which is hard foam, preferably a foamed epoxy resin. In the post-machining process, the rotor blade is mechanically secured to the rotor hub end of the rotor blade to connect the end of the rotor blade to the blade of a partially composite coupling member for connecting the rotor blade.

Here's an example:

In the exemplary embodiment, a trapezoidal rotor blade having a wingspan of MACA 0012-0018 (National Advisory Committee for Aeronautics, US) was made having a length of 3850 mm and a maximum width of 230 mm.

Six layers of 400 gr / m ² biaxial glass fabric were laminated to the inner surface of a cavity-shaped 3850 mm long tool using MOS 1285 laminating epoxy resin (HEXION INC. US) and MGS H287 resin crosslinking agent (HEXION INC. US). Upon completion of the lamination, the entrance edges were allowed to cure at room temperature for 24 hours.

In this example, a hollow main support was made at the inner (inner) end of the rotor hub, 60 mm wide and 28 mm thick, and at the outer end 40 mm wide and 15 mm thick. On a sheet of silicon hose not exceeding the width of the main holder, forming a core of the main holder 1, the core is 4 layers first, gradually decreasing the length and gradually increasing the number of layers, and finally at the rotor end one quarter of the total length 500 g / m. ² UD glass fabrics were laminated in the longitudinal direction with roving fibers. MGS 1285 laminating epoxy resin (HEXION INC. US) and MGS H287 resin crosslinker (HEXION INC. US) were used for lamination. Following lamination, the UD glass tissue extending beyond the tool core was folded back into the open, main, a, b, c part holding tool (Figure 5) and closed as shown. By blowing compressed air through the air inlet nozzle of the silicone elastic hose 1b, pressurized laminated layers of resin-impregnated roving fabrics were pressed against the die wall and the composite main holder was allowed to cure at room temperature for 24 hours.

The finished composite main holder was removed from the tool, and on its outer end a weight of 1.8 kg of lead was fixed by screw reinforcement.

The inner 165 mm wide and 100 mm wide outer edges (3) have 4 layers of 163 gr / m ^{2 of} biaxial fiberglass, MGS L285 (HEXION INC. US) laminating resin and MGS H287 (HEXION INC.). US) resin curing agent by lamination. The end of the rotor blade was formed as a drop (Figure 7). After the lamination of the impregnated layer or 3c stiffening element of 5 mm thickness, 0.48 g / m ² NOMEX (DuPont, USA)

-9 quarts of honeycomb were reinforced with the laminating resin and then left at room temperature for 24 hours with your crosslinked ™ laminated covers.

In the next step, the previously produced elements are placed in one half of the heat treatment die of the rotor blade shown in Figure 6; case that the main holder 1 protruded 250 mm from the inner end of the rotor blade, the cavity between the leading edge 2 and the main holder 1 was filled with Sicomin PB25O / DMO3 foam epoxy resin (Siimonim, Frj. The matching surfaces of the elements (4) MGS A2O / S2O HEXION INC. US) was applied with adhesive resin, and the tool was sealed to exert pressure on the elements and their fitting parts, allowed to stand at room temperature for 24 hours and then cured for 8 hours to complete curing. the rotor blade was removed from the tool and painted after finishing, the rotor blade thus manufactured was in compliance with aviation regulations and the 3850 mm long blade weighed 9 kg.

ΙΟ-

Claims (10)

Ι. Fiber-reinforced composite helicopter rotor blade for lightweight and ultralight helicopters with a hollow body symmetrical main support, rigid laminated entry edge and rigid laminated exit edge, ozo / denoted as longitudinal unidirectional (UD) roving fabric arranged in the longitudinal direction of the main support (1) formed of composite material var; the leading edge (2) and the lower and upper cover surface (3a, 3 b) of the exit edge (3) being made of a composite material of biaxial fabric and synthetic resin, a honeycomb stiffening element on the inner surface of the upper and lower cover surface (3a, 3b). (3c) is provided, in that a balancing mass is attached to at least a portion of the leading edge (3) having a hollow structure and at least a portion thereof along the leading edge (2) of the main carrier (1). 2. The helicopter rotor blade of claim 1, wherein said synthetic resin is a synthetic epoxy resin. Helicopter rotor blade according to claim 1 or 2, characterized in that the honeycomb stiffening element (3c) attached to the inner surface of the upper and lower cover surfaces (3a, 3b) of the main carrier (1) is a Kevlar stiffener. 4. Helicopter rotor blade according to any one of claims 1 to 3, characterized in that the rotor blade has a trapezoidal rotor blade of symmetrical profile. 5. Helicopter rotor blade according to any one of claims 1 to 5, characterized in that a drop-shaped end element for reducing the noise caused by the rotor blade is provided at the opposite end of the rotor hub. 6. 1-5. Helicopter rotor blade according to any one of claims 1 to 3, characterized in that the elements of the rotor blade are bonded to each other with high strength adhesive. Helicopter rotor blade according to claim 6, characterized in that the elements of the rotor blade are bonded to each other by a high-strength epoxy adhesive. 8. Helicopter rotor blade according to any one of claims 1 to 3, characterized in that the leading edge (2) is elastic coated. 9. Helicopter rotor blade according to any one of claims 1 to 3, characterized in that the cavity (2a) between the leading edge (2) and the main carrier (1) is filled with a foamable liquid resin forming a hard foam. Helicopter rotor blade according to claim 9, characterized in that the cavity (2a) between the leading edge (2) and the main carrier (1) is filled with a foaming liquid epoxy resin.