Composite blades with tips that bear concentrated loads

Abstract

This invention relates to the field of rotor blade technology, specifically to a composite material rotor blade with a tip that bears concentrated loads. The composite material rotor blade includes a main beam made of pre-impregnated unidirectional glass fiber strips, a first metal joint, a second metal joint, internal piping, and auxiliary structures for blade filling or covering. Internal piping extending through the blade span provides a structural pathway to the fuselage for the operation of tip-mounted equipment. This composite material rotor blade utilizes a tensile structure formed by main and auxiliary glass fiber bundles between the first and second metal joints to create the main beam. This allows for the installation of a load-bearing joint at the blade tip without altering the blade's primary aerodynamic performance, enhancing the load-bearing capacity of the blade tip and meeting the specific functional requirements of mounting power units, noise reduction equipment, or other testing equipment at the rotor tip of a rotor system.

Description

Technical Field

[0001] This invention relates to the field of rotor blade technology, and more specifically to a composite material blade with a blade tip that bears concentrated loads. Background Technology

[0002] As the performance requirements for helicopters continue to increase, helicopter rotor blade structures have evolved from the initial wooden blades, through steel-wood hybrid blades and metal blades, to today's composite material blades. When helicopter rotor blades operate, they are in a high-speed rotating state, and centrifugal force is the primary load on the blades. The aerodynamic lift of the blades and the centrifugal force are superimposed, resulting in a resultant force at a certain angle to the rotor's plane of rotation. The blades, through flapping hinges, flap upwards at a certain angle, ultimately operating under a load condition dominated by thrust along the blade's span.

[0003] Composite material blades possess anisotropic mechanical properties, offering significant advantages over metal blades. For example, composite materials exhibit a much higher specific strength than metal materials along their fiber-major direction. However, composite material blades also have limitations in use. For instance, to meet blade mass characteristics and balance requirements, counterweights are typically placed at the blade tips to eliminate or reduce imbalances between blades caused by manufacturing errors. Since composite structures cannot withstand concentrated loads through simple perforation like metal materials, mechanical perforation cuts the reinforcing fibers, significantly reducing the composite's load-bearing capacity. Therefore, existing composite material blades struggle to meet the specific functional requirements of mounting power units, noise reduction equipment, or other testing equipment at the rotor tip of a rotor system.

[0004] A search revealed that Chinese patent document CN113942643A discloses a composite material blade with a replaceable tip. This composite material blade includes a blade body section and a tip section. The blade body connector is a single lug located within the blade body skin. The single lug also has multiple first bolt holes penetrating the upper and lower surfaces of the lug. The tip connector section includes a tip skin, a tip connector, and a tip filler block. The tip connector is a double lug that mates with the single lug and is located within the tip skin. Both lugs have second bolt holes that mate with the first bolt holes. The blade body connector and the tip connector are inserted together and fixed with bolts.

[0005] Although the aforementioned composite blade has a replaceable tip structure, is simple in structure, and is easy to disassemble and assemble, allowing for quick tip replacement and improving the tip's load-bearing capacity compared to traditional blades, the bolt connection structure in the composite blade significantly reduces the load-bearing capacity of the composite material and decreases the blade's ability to bear spanwise tensile loads.

[0006] For example, Chinese patent document CN110683048A discloses a composite material rotor blade and a method for counterweighting the rotor tip of an unmanned helicopter. The composite material rotor blade has a parabolic trimming section at the front end of the blade body. Inside the parabolic trimming section, a trailing edge counterweight tube, a leading edge counterweight tube, and a lead weight for the rotor tip are arranged. Leading edge counterweight tube screws and trailing edge counterweight tube screws are respectively installed on the leading edge counterweight tube and the trailing edge counterweight tube to seal the tube openings.

[0007] Although the aforementioned composite blades can effectively maintain the original aerodynamic layout and lift characteristics of the rotor system, the load-bearing capacity of the composite blades for concentrated loads at the blade tip is still insufficient to meet the requirements of helicopter rotor systems.

[0008] In summary, during the use of helicopter rotor blades, how to design a composite material rotor blade to improve the load-bearing capacity of the blade tip while ensuring the aerodynamic performance of the rotor, and to meet the specific functional requirements of mounting power units, noise reduction equipment, or other test equipment on the rotor system blade tip, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0009] The purpose of this invention is to provide a composite material blade for use in helicopter rotor blades, which can improve the load-bearing capacity of the blade tip while ensuring the aerodynamic performance of the rotor, and meet the specific functional requirements of mounting power units, noise reduction equipment, or other test equipment on the rotor system blade tip.

[0010] To achieve the above objectives, the present invention adopts the following solution: a composite material blade with a tip that bears concentrated loads is proposed, comprising a main beam made of pre-impregnated glass fiber unidirectional tape, a first metal joint, a second metal joint, internal piping, and auxiliary structures for blade filling or covering;

[0011] The main beam includes a main glass fiber bundle and an auxiliary glass fiber bundle. The main glass fiber bundle connects a first metal joint and a second metal joint. The auxiliary glass fiber bundle is wound around the first metal joint. The main glass fiber bundle and the auxiliary glass fiber bundle form a tensile structure of the main beam between the first metal joint and the second metal joint.

[0012] The first metal connector is located at the root of the composite material blade. The first metal connector is provided with a first pin hole connected to the blade hub. The side wall of the first metal connector is provided with a first arc portion for the main glass fiber bundle and the auxiliary glass fiber bundle to be wound. The side of the first metal connector away from the first arc portion is provided with an installation groove for the internal pipeline to be embedded.

[0013] The second metal joint is located at the tip of the composite material blade. The second metal joint is provided with a second pin hole that is connected to the blade tip mounting component. A through groove is provided between a pair of second pin holes for the main glass fiber bundle to pass through. A second arc portion for the main glass fiber bundle to be wound is provided on both sides of the through groove.

[0014] The internal pipes are embedded in the main beam along the direction from the blade root to the blade tip. The blade root end of the internal pipes extends out of the mounting groove, and the blade tip of the internal pipes extends out of the through groove.

[0015] The auxiliary structure includes a skin and a foam body. The skin covers the outside of the main beam, and a conical cavity is formed between the skin and the main beam. The foam body fills the conical cavity.

[0016] Preferably, the main and auxiliary glass fiber bundles in the main beam employ a progressive variable cross-section design. Based on the change in the cross-sectional size of the main beam, the main beam has a sequentially connected root region, first transition region, belly region, second transition region, and tip region from the blade root towards the blade tip. With this configuration, the tensile load borne by the main beam along the blade span gradually decreases from the blade root to the blade tip. The centrifugal force load transmitted from the concentrated mass mounting point at the blade tip is approximately half of the total blade load at the blade root. The progressive variable cross-section design of the unidirectional fiber bundles in the main beam ensures that the load-bearing capacity of any cross-section along the span is matched to the load at that location.

[0017] Preferably, the first arcuate portion of the first metal joint is provided with a flange that gathers the main glass fiber bundle and the auxiliary glass fiber bundle. This flange serves to limit the movement of the main and auxiliary glass fiber bundles, preventing them from detaching from the first arcuate portion of the first metal joint during the forming of the composite blade.

[0018] Preferably, the main beam has two main glass fiber bundles and three auxiliary glass fiber bundles. The starting ends of the two main glass fiber bundles are wound around one of the second arc sections of the second metal joint, and the ends of the main glass fiber bundles are bent over the first arc section of the first metal joint and then wound around the other second arc section of the second metal joint. The three auxiliary glass fiber bundles are wound around the first arc section of the first metal joint, with the starting ends of the auxiliary glass fiber bundles located in the first transition zone and the ends of the auxiliary glass fiber bundles located in the second transition zone. This configuration, with the main glass fiber bundles divided into two bundles surrounding the two load-bearing pin joints, optimizes the structure of the blade root joint area, significantly improving the blade's load-bearing capacity without needing to comprehensively increase the blade's structural dimensions.

[0019] Preferably, the first metal joint has a pair of first pin holes, which are symmetrically distributed along the pitch axis of the composite blade, and the distance between the two first pin holes is 25% of the blade chord length. With this arrangement, the load-bearing pins in the two first pin holes tend to be balanced, and the stress structure is the most reasonable.

[0020] Preferably, a pair of second pin holes are symmetrically distributed along the pitch axis of the composite blade, and the spacing between the two second pin holes is 30% of the blade chord length. With this arrangement, the load-bearing capacity of the pins in the two second pin holes tends to be balanced, and the stress structure is the most reasonable.

[0021] Preferably, the internal piping is a metal pipe with a channel for gas, liquid or electronic circuits to pass through. The metal pipe has a circular cross-section and its outer diameter is 8% of the blade chord length.

[0022] Preferably, the auxiliary structure also includes a counterweight located at the leading edge of the composite blade. This arrangement ensures that the blade's center of gravity along the airfoil chord is within 25% of the distance from the leading edge.

[0023] Preferably, the skin is made of fiberglass cloth laid in different directions. This arrangement helps the skin structure withstand the torsional loads of the composite blades.

[0024] As a preferred option, the propeller tip mounting components include a propeller tip power unit, noise reduction equipment, and testing equipment.

[0025] Compared with the prior art, the composite material blade with a concentrated load-bearing tip provided by this invention has the following outstanding substantive features and significant progress: This composite material blade with a concentrated load-bearing tip utilizes a tensile structure of a main beam formed by a main glass fiber bundle and an auxiliary glass fiber bundle between a first metal joint and a second metal joint. This achieves the goal of setting a load-bearing joint at the blade tip without changing the main aerodynamic performance of the blade, improving the load-bearing capacity of the blade tip, and meeting the specific functional requirements of mounting power units, noise reduction equipment, or other test equipment at the rotor system blade tip. It also reserves an internal pipeline that runs through the blade span, providing a structural passage that can connect with the fuselage for the operation of the blade tip mounting equipment. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a composite material blade with a tip bearing concentrated load in an embodiment of the present invention;

[0027] Figure 2 yes Figure 1 A schematic diagram of the cross-sectional structure of a composite material blade with a tip that bears concentrated loads;

[0028] Figure 3This is a schematic diagram of the spanwise distribution of the main beam cross-sectional area of ​​a composite material blade with a blade tip bearing concentrated load in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the unidirectional fiber layup of the main beam;

[0030] Figure 5 This is a schematic diagram of the assembly structure of the first metal joint.

[0031] Reference numerals: 1. Main beam; 2. First metal joint; 3. Second metal joint; 4. Internal piping; 5. Auxiliary structure; 6. Pitch axis; 11. Main glass fiber bundle; 12. Auxiliary glass fiber bundle; 13. Paddle root area; 14. First gradient area; 15. Paddle belly area; 16. Second gradient area; 17. Paddle tip area; 21. First pin hole; 22. First arc portion; 23. Mounting groove; 51. Skin; 52. Foam body; 53. Counterweight. Detailed Implementation

[0032] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] like Figure 1-5 As shown in the present invention, a composite material blade with a blade tip that bears concentrated load is proposed in this embodiment of the invention. It aims to improve the load-bearing capacity of the blade tip and meet the specific functional requirements of mounting power units, noise reduction equipment, or other test equipment on the blade tip of a rotor system.

[0034] This invention proposes a composite material blade with a blade tip that bears concentrated loads. By utilizing the main glass fiber bundle and auxiliary glass fiber bundle to form a tensile structure of the main beam between the first metal joint and the second metal joint, the main aerodynamic performance of the blade is not changed while a load-bearing joint is set at the blade tip. This improves the load-bearing capacity of the blade tip and meets the specific functional requirements of mounting power units, noise reduction equipment, or other test equipment at the blade tip of the rotor system. An internal pipeline running through the blade span is reserved to provide a structural passage that can be connected to the fuselage for the operation of the blade tip mounting equipment.

[0035] Example 1

[0036] like Figure 1 As shown, a composite material blade with a tip that bears concentrated loads includes a main beam 1 made of pre-impregnated glass fiber unidirectional tape, a first metal joint 2, a second metal joint 3, internal pipes 4, and an auxiliary structure 5 for filling or covering the blade.

[0037] like Figure 1 Combination Figure 4As shown, the main beam 1 includes a main glass fiber bundle 11 and an auxiliary glass fiber bundle 12. The main glass fiber bundle 11 connects to a first metal joint 2 and a second metal joint 3. The auxiliary glass fiber bundle 12 is wound around the first metal joint 2. The main glass fiber bundle 11 and the auxiliary glass fiber bundle 12 form a tensile structure of the main beam 1 between the first metal joint 2 and the second metal joint 3.

[0038] like Figure 5 As shown, the first metal connector 2 is located at the root of the composite material blade. The first metal connector 2 has a first pin hole 21 connected to the blade hub. The side wall of the first metal connector 2 has a first arcuate portion 22 for the main glass fiber bundle 11 and the auxiliary glass fiber bundle 12 to be wound. The side of the first metal connector 2 away from the first arcuate portion 22 has a mounting groove 23 for the internal conduit 4 to be embedded.

[0039] The second metal connector 3 is located at the tip of the composite blade. The second metal connector 3 has a second pin hole for connection to a tip mounting component, such as a tip power unit, noise reduction equipment, and testing equipment. A through-slot is provided between a pair of second pin holes for the main glass fiber bundle 11 to pass through. Second arc portions for the main glass fiber bundle 11 to be wound around are provided on both sides of the through-slot.

[0040] like Figure 1 Combination Figure 2 As shown, the internal pipe 4 is embedded in the main beam 1 along the direction from the blade root to the blade tip. The blade root end of the internal pipe 4 extends out from the mounting groove 23. The blade tip of the internal pipe 4 extends out from the through groove.

[0041] like Figure 2 As shown, the auxiliary structure 5 includes a skin 51 and a foam body 52. ​​The skin 51 covers the outside of the main beam 1. A conical cavity is formed between the skin 51 and the main beam 1. The foam body 52 fills the conical cavity. For example, the skin 51 is made of fiberglass cloth laid in different directions. It consists of plain-weave high-strength fiberglass cloth laid in at least three directions: 0 degrees, 90 degrees, and 45 degrees. This arrangement helps the skin 51 structure to bear the torsional load of the composite blade.

[0042] The first arc portion 22 of the first metal connector 2 is provided with a flange that gathers the main glass fiber bundle 11 and the auxiliary glass fiber bundle 12. This flange is used to limit the main glass fiber bundle 11 and the auxiliary glass fiber bundle 12, preventing them from detaching from the first arc portion 22 of the first metal connector 2 during the forming process of the composite material blade.

[0043] Preferably, the internal pipe 4 is a metal pipe, which has a channel for gas, liquid or electronic circuits to pass through. The metal pipe has a circular cross-section and its outer diameter is 8% of the blade chord length.

[0044] like Figure 2 As shown, the auxiliary structure 5 also includes a counterweight 53. The counterweight 53 is located at the leading edge of the composite blade. This arrangement ensures that the center of gravity of the blade along the airfoil chord is within 25% of the distance from the leading edge.

[0045] The composite material blade with a concentrated load-bearing tip proposed in Embodiment 1 of this invention can, while satisfying the aerodynamic performance of the rotor, support a concentrated mass load of no more than 50% of the blade's own weight at the blade tip, while maintaining the blade's structural dimensions essentially unchanged, with a weight increase of no more than 10%. This effectively preserves the original aerodynamic layout, lift characteristics, handling performance, and weight specifications of the rotor system. Furthermore, without compromising the overall performance of the aircraft, it achieves functions such as rotor system dynamic configuration conversion, noise reduction technology improvement, and experimental data acquisition.

[0046] Example 2

[0047] The composite material blade with a concentrated load-bearing tip proposed in Embodiment 2 of this invention can utilize currently mainstream and most advanced rotor blade airfoils, and a negative torsion angle can be designed according to aerodynamic requirements. A single-wound, double-hole metal joint is pre-embedded at the blade root for connection to the rotor hub; the hole spacing is 25% of the airfoil chord length, and the two holes are symmetrically distributed on both sides of the pitch axis. A double-wound, double-hole metal joint is pre-embedded at the blade tip; the hole spacing is 30% of the blade chord length, and the two holes are symmetrically distributed on both sides of the pitch axis. The blade body mainly consists of a main beam, skin, and a filling microfiber. The main beam is made of unidirectional glass fiber material laid along the spanwise direction and is the main load-bearing component of the blade; the skin is made of plain-weave high-strength glass cloth laid in different directions to bear the torsional load of the blade; and the filling microfiber is composed of lightweight foam material.

[0048] The unidirectional glass fibers that make up the main beam wrap around the outside of the metal joint at the root of the blade, and at the tip of the blade they are divided into two bundles, which wrap around the outside of the two joint holes of the metal joint respectively.

[0049] A metal conduit is embedded inside the blade along its entire length in the spanwise direction. It exits the blade from the upper surface of the joint area at the blade root and from the tip surface at the blade tip. Depending on the purpose of the external load on the blade, the metal conduit can be used for the transmission of media such as gas and liquid, or for the laying of electronic circuits.

[0050] The main load-bearing structure of the blade consists of three parts: a single-wound double-hole metal joint at the blade root, a main beam, and a double-wound double-hole metal joint at the blade tip. The single-wound double-hole metal joint at the blade root is an integral double-hole metal joint. To facilitate docking with the blade hub and load transfer, a metal joint capable of bearing concentrated loads is required at the blade root.

[0051] The main loads on the blades include spanwise tension, flapping moment, teeter moment, and torsional load. These loads can be transferred through two vertical force pins perpendicular to the blade chord. The spacing between the force pins is 25% of the blade chord length, which helps to control the additional stress generated by the teeter moment within a reasonable range, thus focusing on addressing the spanwise tension generated by centrifugal force.

[0052] The spanwise tension of the blades is entirely borne by the main beam, which transfers the load to the root joint via a wrap-around joint. Currently widely used composite blades often employ a structure where the main beam's unidirectional fibers are divided into two bundles, each wrapping around one of the two load-bearing pin joints. During the wrap-around process, the unidirectional fiber direction rotates 180 degrees, resulting in normal compression perpendicular to the principal direction of the unidirectional fibers at the contact surface between the fibers and the joint. Since the load-bearing capacity of anisotropic composite structures in the normal direction is far lower than their load-bearing capacity in the principal direction, the additional normal compression generated by the wrap-around configuration is a significant cause of failure in the main load-bearing structure.

[0053] In Embodiment 2 of this invention, through CAE simulation calculations and sample mechanical tests, it was found that the commonly used structural form of two bundles surrounding two stressed pin joints results in a failure load of the unidirectional fiber at the joint, which is approximately 1 / 3 of the tensile failure load of the beam with a uniform cross-section of the blade. Therefore, by reasonably optimizing the structure of the joint area at the blade root, the load-bearing capacity of the blade can be significantly improved without increasing the overall size of the blade structure.

[0054] Through optimized simulation calculation iterations, it was found that the load-bearing capacity of the unidirectional fiber swivel joint is related to three variables: the swivel radius r, the height h of the swivel fiber bundle cross-section, and the thickness b of the swivel fiber bundle cross-section. When the cross-sectional area s of the swivel fiber bundle is a constant value, the larger the values ​​of r and h, the greater the load-bearing capacity; and since s = b * h, the larger the value of h, the smaller the value of b.

[0055] Therefore, the blade root adopts a single-wound double-hole joint, which maximizes the circumference r of the surrounding fiber bundle within the limited shape of the blade root, effectively improving the load-bearing capacity of the unidirectional fiber circumference area at the root.

[0056] The blade pitch axis, which is the axis of spanwise tension generated by centrifugal force, is located at 25% of the chord length from the blade leading edge. The integrated joint at the blade root is symmetrical about the pitch axis, with the two force-bearing pins spaced 25% of the chord length apart and positioned 12.5% ​​of the chord length from the pitch axis. This design ensures balanced load-bearing capacity for the two force-bearing pins, resulting in the most rational stress distribution structure.

[0057] The thickness of the single-wound double-hole joint at the blade root is determined based on the h value of the fiber bundle cross-section when the main beam wraps around the joint.

[0058] The single-wound double-hole joint at the blade root has a flange in the unidirectional fiber circling area that promotes fiber convergence.

[0059] The single-wound double-hole connector at the blade root has an installation passage reserved for metal pipes on one side of the upper surface of the blade.

[0060] With b*h=s as a constant, the cross-sectional characteristics of the surrounding fiber bundle are taken as b:h=1:2. This maximizes the h value within the acceptable blade root thickness range, thereby enhancing the load-bearing capacity of the surrounding area.

[0061] The main beam is made of unidirectional prepreg of glass fiber laid along the blade span. It wraps around the outside of the metal joint at the blade root; at the blade tip, it is divided into two bundles, which wrap around the outside of the two joint holes of the metal joint respectively.

[0062] The tensile load along the blade span borne by the main girder gradually decreases from the blade root to the blade tip. The centrifugal load transmitted from the concentrated mass mounting point at the blade tip is approximately half of the total blade load at the blade root. The unidirectional fiber bundles of the main girder employ a progressive variable cross-section design to match the load capacity of any cross-section along the span with the load at that location. The cross-sectional area distribution of the main girder along the span is shown in the table below:

[0063] (Note 1: The connector hole at the blade root is 0L, and the connector hole at the blade tip is 100%L.)

[0064] (Note 2: The section with the largest cross-sectional area of ​​the main beam is 1S.)

[0065] Location Paddle root area First Gradient Zone paddle belly region Second gradient zone Paddle tip area Position of the main beam along its span 0-15%L 15%-30% L 30%-85% L 85%-95% L 95%-100% L Cross-sectional area of ​​the main beam 1S 1-0.7S gradient zone. 0.7 S The direction changes gradually from 0.7 to 0.4 s; the direction changes gradually from 0.4 to 0 s. The total cross-sectional area changes gradually from 0.7 to 0.8 s. 0.8S

[0066] When achieving the above-mentioned cross-sectional area changes, unidirectional fiber laying also follows the following principles:

[0067] (a) The total amount of unidirectional fiber used in the main beam is half of the maximum cross-sectional area 1S, i.e. 0.5S;

[0068] (b) 40% (i.e. 0.2S) of the total fiber amount of the fiber bundle is a complete fiber bundle that simultaneously surrounds both the root and tip joints, and this part of the fiber bundle is distributed on the outer ring of the surrounding area when surrounding the root joint.

[0069] (C) In addition, 60% (i.e. 0.3S) of the total fiber amount of the fiber bundle only surrounds the blade root joint and terminates in two gradient zones, and this part of the fiber bundle is distributed in the inner circle of the surrounding zone when surrounding the blade root joint.

[0070] like Figure 3 As shown, the main glass fiber bundles 11 and auxiliary glass fiber bundles 12 in the main beam 1 are laid using a progressive variable cross-section design. Based on the change in the cross-sectional size of the main beam 1, the main beam 1 has a root region 13, a first transition region 14, a belly region 15, a second transition region 16, and a tip region 17 connected sequentially from the blade root to the blade tip. With this arrangement, the tensile load borne by the main beam 1 along the blade span gradually decreases from the blade root to the blade tip. The centrifugal force load transmitted from the concentrated mass mounting point at the blade tip is approximately half of the total blade load at the blade root. The progressive variable cross-section design of the unidirectional fiber bundles in the main beam 1 ensures that the load-bearing capacity of any cross-section along the span of the main beam 1 matches the load at that location.

[0071] like Figure 4 The main beam 1 has two main glass fiber bundles 11 and three auxiliary glass fiber bundles 12. The starting ends of the two main glass fiber bundles 11 are wound around one of the second arc portions of the second metal joint 3. The ends of the main glass fiber bundles 11 are bent through the first arc portion 22 on the first metal joint 2 and then wound around the other second arc portion of the second metal joint 3. The three auxiliary glass fiber bundles 12 are wound around the first arc portion 22 of the first metal joint 2. The starting ends of the auxiliary glass fiber bundles 12 are located in the first gradient zone 14, and the ends of the auxiliary glass fiber bundles 12 are located in the second gradient zone 16. With this configuration, the main glass fiber bundles 11 are divided into two bundles and wrapped around the two load-bearing pin joints. This optimized structure of the blade root joint area can significantly improve the blade's load-bearing capacity without increasing the overall blade structure size.

[0072] The first metal joint 2 has a pair of first pin holes 21, which are symmetrically distributed along the pitch axis 6 of the composite material blade. The spacing between the two first pin holes 21 is 25% of the blade chord length. With this arrangement, the load-bearing pins in the two first pin holes 21 tend to be balanced, and the stress structure is the most reasonable.

[0073] A pair of second pin holes are symmetrically distributed along the pitch axis 6 of the composite blade, and the spacing between the two second pin holes is 30% of the blade chord length. With this arrangement, the load-bearing pins in the two second pin holes tend to be balanced, and the stress structure is the most reasonable.

[0074] The blade tip features a double-wound, double-hole metal connector. This connector allows for concentrated load attachment at the blade tip. The double holes are two vertical force-bearing pin holes perpendicular to the blade's chord direction.

[0075] The load-bearing capacity of the blade tip joint also follows a pattern related to three variables: the wrapping radius r, the height h of the wrapping fiber bundle cross-section, and the thickness b of the wrapping fiber bundle cross-section. To ensure that the cross-sectional height h of the fiber wrapping area does not exceed the maximum thickness of the airfoil, a double-hole, double-wrap fiber wrapping method is adopted. Although the value of r is reduced, the value of b is halved, thus achieving the maximum load-bearing capacity with the same amount of fiber.

[0076] The blade tip connector has two symmetrical holes distributed on both sides of the pitch axis, with a hole spacing of 30% of the blade chord length. A gap is left at the pitch axis between the two holes for metal pipes to pass through.

[0077] The above-mentioned blade tip joint structure arrangement can maximize the utilization of the airfoil cross-sectional area at the blade tip, thereby minimizing the protrusion of the joint into the airfoil and maintaining the aerodynamic performance of the blade tip.

[0078] Embodiment 2 of this invention proposes a composite material blade with a tip that bears concentrated loads, which meets the specific functional requirements of mounting a power unit, noise reduction equipment, or other test equipment on the tip of a rotor system, and has the following advantages:

[0079] (1) The specific main load-bearing structure enables the main aerodynamic performance of the blade to be maintained without changing the load-bearing joint at the blade tip.

[0080] (2) The blade root joint connection form is similar to that of the mainstream blades, which is compatible with the hub interface of the current mainstream rotor system. It can be replaced, thereby making the most of the existing mature technology system of the rotor system.

[0081] (3) The double-hole structure of the propeller tip bearing joint, which is symmetrically distributed along the pitch axis, can easily and efficiently install mass equipment without the need for additional auxiliary structures.

[0082] (4) Reserve a pipeline that runs through the span of the blade to provide a structural passage that can be connected to the fuselage for the operation of the blade tip attachment equipment.

[0083] (5) The blade has the same shape as the current mainstream composite material blade and similar layout of auxiliary structures, so that the blade can be manufactured without investing in additional process solutions.

[0084] Example 3

[0085] Embodiment 3 of the present invention provides a composite material blade for a rotorcraft with a small engine mounted at the blade tip, as described in Embodiments 1 and 2. The rotorcraft is driven by a small engine mounted at the blade tip to rotate the rotor and generate lift. The engine's fuel tank is located within the fuselage, and fuel is supplied to the engine at the rotor tip via a pressurized supply system and internal piping of the rotor system. The fuel supply piping from the rotor hub to the engine is achieved through metal pipes pre-embedded inside the blade. The small engine is attached to a metal joint at the blade tip. After starting, the engine generates thrust to rotate the rotor and generate lift. During rotor rotation, the centrifugal force of the engine is entirely borne by the blade, which serves the dual function of a lifting surface and a primary load-bearing component.

[0086] Rotorcraft with a power configuration of composite material blades as mentioned in Examples 1 and 2 eliminates the need for complex and bulky structures such as turboshaft engines, transmission systems, and reducers, providing a new direction for the design needs of lightweight and low-cost aircraft.

[0087] This invention is not limited to the specific technical solutions described in the above embodiments. Besides the above embodiments, this invention may have other implementation methods. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A composite material blade with a tip bearing concentrated loads, characterized in that, It includes a main beam made of pre-impregnated glass fiber unidirectional tape, a first metal joint, a second metal joint, internal piping, and auxiliary structures for blade filling or covering; The main beam includes a main glass fiber bundle and an auxiliary glass fiber bundle. The main glass fiber bundle connects a first metal joint and a second metal joint. The auxiliary glass fiber bundle is wound around the first metal joint. The main glass fiber bundle and the auxiliary glass fiber bundle form a tensile structure of the main beam between the first metal joint and the second metal joint. The first metal connector is located at the root of the composite material blade. The first metal connector is provided with a first pin hole connected to the blade hub. The side wall of the first metal connector is provided with a first arc portion for the main glass fiber bundle and the auxiliary glass fiber bundle to be wound. The side of the first metal connector away from the first arc portion is provided with an installation groove for the internal pipeline to be embedded. The second metal joint is located at the tip of the composite material blade. The second metal joint is provided with a second pin hole that is connected to the blade tip mounting component. A through groove is provided between a pair of second pin holes for the main glass fiber bundle to pass through. A second arc portion for the main glass fiber bundle to be wound is provided on both sides of the through groove. The internal pipes are embedded in the main beam along the direction from the blade root to the blade tip. The blade root end of the internal pipes extends out of the mounting groove, and the blade tip of the internal pipes extends out of the through groove. The auxiliary structure includes a skin and a foam body. The skin covers the outside of the main beam, and a conical cavity is formed between the skin and the main beam. The foam body fills the conical cavity. The main beam is configured to bear tensile loads along the blade span, which gradually decrease from the blade root to the blade tip. The unidirectional fiber bundles of the main beam are laid with a progressive variable cross-section design, so that the load-bearing capacity of any cross-section along the span of the main beam matches the load at that location.

2. The composite material blade with a tip bearing concentrated load according to claim 1, characterized in that, The main glass fiber bundles and auxiliary glass fiber bundles in the main beam are laid with a progressive variable cross-section design. According to the change in the cross-sectional size of the main beam, the main beam has a blade root region, a first gradient region, a blade belly region, a second gradient region and a blade tip region connected in sequence from the blade root to the blade tip.

3. The composite material blade with a tip bearing concentrated load according to claim 1, characterized in that, The first arc portion of the first metal connector is provided with a flange that gathers the main glass fiber bundle and the auxiliary glass fiber bundle.

4. The composite material blade with a tip bearing concentrated load according to claim 2, characterized in that, The main beam has two main glass fiber bundles and three auxiliary glass fiber bundles. The starting ends of the two main glass fiber bundles are wound around one of the second arc portions of the second metal joint. The ends of the main glass fiber bundles are bent through the first arc portion of the first metal joint and then wound around the other second arc portion of the second metal joint. The three auxiliary glass fiber bundles are wound around the first arc portion of the first metal joint. The starting ends of the auxiliary glass fiber bundles are located in the first gradient zone, and the ends of the auxiliary glass fiber bundles are located in the second gradient zone.

5. The composite material blade with a tip bearing concentrated load according to claim 1, characterized in that, The first metal connector has a pair of first pin holes, which are symmetrically distributed along the pitch axis of the composite blade, and the hole spacing of the pair of first pin holes is 25% of the blade chord length.

6. The composite material blade with a tip bearing concentrated load according to claim 1, characterized in that, A pair of second pin holes are symmetrically distributed along the pitch axis of the composite blade, and the spacing between the two second pin holes is 30% of the blade chord length.

7. The composite material blade with a tip bearing concentrated load according to claim 1, characterized in that, The internal piping is a metal pipe, and the inside of the metal pipe has a channel for gas, liquid or electronic circuits to pass through. The metal pipe has a circular cross-section, and the outer diameter of the metal pipe is 8% of the blade chord length.

8. The composite material blade with a tip bearing concentrated load according to claim 1, characterized in that, The auxiliary structure also includes a counterweight, which is located at the leading edge of the composite material blade.

9. The composite material blade with a tip bearing concentrated load according to claim 1, characterized in that, The skin is made of glass cloth laid in different directions.

10. The composite material blade with a tip bearing concentrated load according to claim 1, characterized in that, The propeller tip mounting components include a propeller tip power unit, noise reduction equipment, and testing equipment.

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