Propeller blade

Abstract

To provide a propeller blade which is suitable as a propeller blade for UAM and drone, and has improved lightning resistance and collision resistance while maintaining light weight.SOLUTION: A propeller blade has a resin layer, in which a plurality of fibrous or ribbon-shaped conductors and a plurality of non-conductive fiber bundles are embedded in a resin, on a side of an external surface of a propeller-shaped structure. The conductor is oriented toward a bottom from a tip of the propeller blade. As arrangement of the conductor and the non-conductive fiber bundle in a resin layer A viewed from an outer side of the propeller blade, there are a plurality of areas A that have an area where the conductor exists on an outermost side (this portion is called "area A" for convenience) and an area where the non-conductive fiber bundle exists on an outermost side, and the conductor can be grounded from a propeller fitting part at the bottom of the propeller blade. The resin layer A is the outermost layer from an electrical standpoint.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a propeller blade.

Background Art

[0002] A propeller blade has an airfoil shape and obtains thrust by pushing air backward by rotating around a drive shaft. In order to efficiently push air backward, the propeller blade has a complex shape in which the angle of attack and the chordwise length change from the root to the tip.

[0003] In recent years, new forms of air utilization such as Urban Air Mobility (UAM) and drones have been developed. These aircraft mainly carry a large number of propeller blades on the airframe, and rotate these propeller blades by power to obtain lift and thrust.

[0004] Since UAM and drones are assumed to fly in urban areas, quietness is required. In particular, from the viewpoint of reducing noise associated with the rotation of the propeller blade, measures such as thinning the propeller blade and reducing the propeller rotation speed by mounting a large number of small propeller blades have been taken. In addition, UAM and drones need to withstand lightning strikes during operation and collisions with foreign objects such as birds and flying stones. Therefore, in addition to quietness, lightning resistance and collision resistance are also required as characteristics of propeller blades for UAM and drones.

[0005] Regarding the compatibility between quietness and lightning resistance and collision resistance, for example, when the propeller blade is thinned or miniaturized, the allowable energy of the propeller blade becomes small with respect to the collision energy of the lightning strike or the collision object. Therefore, it is difficult to achieve both of these characteristics particularly required for UAM and drones.

[0006] In addition, since UAM and drones are mainly electric, in order to increase the flight range and payload due to the heavy weight of the battery and motor, etc., it is of course important to reduce the weight of the airframe, and it goes without saying that weight reduction is also required for the propeller blades mounted in large numbers on the airframe.

[0007] To integrate these situations, it can be said that for propeller blades for UAM and drones, means to achieve improvements in lightning resistance and impact resistance without additional weight increase are required.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] In recent years, aircraft with a large number of propeller blades have been developed for UAM and drones. In these aircraft, due to the need to increase flight range and time, there is a high need for weight reduction, especially for propeller blades with a large number of blades per aircraft. To meet this need for weight reduction, fiber-reinforced composite materials with high specific strength and high specific stiffness are applied to the propeller blades.

[0010] Particularly when using a fiber-reinforced composite material for the skin of a propeller blade, it is easy to obtain the effects of the high specific strength and specific rigidity of the fiber-reinforced composite material. On the other hand, compared with metals, fiber-reinforced resin composite materials have a low conductivity, and tend to suffer greater damage during lightning strikes. Particularly at the location where a lightning strike is input into the fiber-reinforced composite material, the current is particularly concentrated and the damage is the greatest. For this reason, as shown in Patent Document 1 and Patent Document 2, for example, measures such as providing a lightning protection layer of a metal mesh or providing a porous film on the outer layer of the conductive layer to disperse the input of current due to lightning strikes have been proposed. On the other hand, these lightning protection measures have an extremely small effect of supplementing the rigidity of the propeller blade. From the viewpoints of weight reduction and rigidity supplementation, these simply increase the weight of the blade.

[0011] In addition, since the propeller blade is operated by rotating at high speed, it has a risk of high-speed collision with various foreign objects such as birds, hailstones, and flying stones. Generally, fiber-reinforced composite materials have low impact resistance, and additional measures are often implemented to improve the impact resistance. For example, Patent Document 3 describes using polymer fibers or a resin with high impact resistance on the outermost layer of the skin. On the other hand, from the viewpoint of lightning resistance, it is desirable to form a lightning protection layer on the surface layer, and it is difficult to achieve both lightning resistance.

[0012] As described above, in the prior art, there has been no situation where a method for improving lightning resistance and impact resistance while maintaining lightness has been found. Therefore, the present invention shows a method for improving lightning resistance and impact resistance while maintaining lightness, and provides a propeller blade suitable as a propeller blade for UAM and drones.

Means for Solving the Problems

[0013] In order to solve such problems, the present invention adopts the following means. [1] A propeller blade having, on the outer surface side of a structure in which a carbon fiber reinforced composite material is shaped into a propeller shape, a resin layer (this layer is hereinafter referred to as "resin layer A" for convenience) in which a plurality of fibrous or ribbon-like conductors and a plurality of non-conductive fiber bundles are embedded in resin. The conductors are oriented in a direction from the tip to the root of the propeller blade, and as the arrangement of the conductors and non-conductive fiber bundles in resin layer A as viewed from the outside of the propeller blade, there are a region where the conductors are on the outermost side (this portion is hereinafter referred to as "region A" for convenience) and a region where the non-conductive fiber bundles are on the outermost side (this portion is hereinafter referred to as "region B" for convenience), and the arrangement is such that a plurality of region As exist. Also, the conductors are configured to be grounded from the propeller attachment portion at the root of the propeller blade, and resin layer A forms the outermost layer electrically. A propeller blade characterized by this. [2] The propeller blade according to [1], wherein, as the arrangement of the conductors and non-conductive fiber bundles in resin layer A as viewed from the outside of the propeller blade, region A is an island and the region other than region A including region B is a sea in a sea-island structure. [3] The propeller blade according to [1] or [2], having an insulating layer between resin layer A and the structure. [4] The propeller blade according to any one of [1] to [3], wherein in resin layer A, 16 or more region As exist in a 5 cm square. [5] Further having a metal receptor, and the metal receptor is electrically joined to resin layer A. The propeller blade according to any one of [1] to [4]. [6] The propeller blade according to [5], wherein the metal receptor is formed in a region within 20% of the total length of the propeller from the tip of the propeller blade. [7] The propeller blade according to any one of [1] to [6], wherein all or part of the plurality of conductors have an electrical connection on the side of the surface opposite to the outside of the propeller blade of resin layer A. [8] The propeller blade according to any one of [1] to [7], wherein the conductors and non-conductive fiber bundles form a braided structure and are embedded in resin layer A. [9] The propeller blade according to any one of [1] to [8], wherein the conductor is carbon fiber, metal fiber, carbon fiber coated with metal, a mixed fiber thereof, or a metal strip.

[10] The propeller blade according to any one of [1] to [9], wherein the electrical conductivity of the conductor is higher than the electrical conductivity of the carbon fiber contained in the carbon fiber composite material layer existing on the inner layer side than the resin layer A.

[11] The propeller blade according to any one of [1] to

[10] , wherein the non-conductive fiber bundle is composed of organic fiber or glass fiber.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a propeller blade that is lightweight and excellent in lightning resistance and impact resistance characteristics. The propeller blade of the present invention is particularly suitable for flying objects such as UAM and drones.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] The propeller blade according to the present invention has, on the outer surface side of a structure in which a carbon fiber reinforced composite material is shaped into a propeller shape, a resin layer (referred to as "resin layer A" for convenience) in which a plurality of fibrous or ribbon-like conductors and a plurality of non-conductive fiber bundles are embedded in resin. The conductor is oriented in a direction from the tip to the root of the propeller blade, and as the arrangement of the conductor and the non-conductive fiber bundle in resin layer A as viewed from the outside of the propeller blade, there are a region where the conductor is outermost (this part is referred to as "region A" for convenience) and a region where the non-conductive fiber bundle is outermost (this part is referred to as "region B" for convenience), and it is arranged such that there are a plurality of region As. Also, the conductor is configured to be grounded from the propeller attachment part at the root of the propeller blade, and resin layer A forms the outermost layer electrically.

[0017] The propeller blade according to the present invention has an airfoil shape and obtains thrust by pushing air backward by rotating around a drive shaft. Generally, a propeller blade has a skin shaped into an airfoil shape, and has a solid structure having a foam core inside, or a structure in which the inside of the skin is a hollow structure and a reinforcing structure such as a shear web that connects the skin in the thickness direction of the airfoil and extends in the airfoil length direction is provided.

[0018] In the present invention, a structure in which a carbon fiber reinforced composite material is shaped into a propeller shape is a structure in which at least the carbon fiber reinforced composite material forms part of the skin structure of the propeller blade.

[0019] Here, the carbon fiber reinforced composite material is a material obtained by embedding carbon fibers as reinforcing fiber materials in a resin. As the form of carbon fibers, for example, there are forms of continuous fibers and short fibers, and any form may be used in the present invention. Further, regarding the form of the base material of carbon fibers, there are forms oriented in one direction, woven fabric forms, NCF (non-crimp fabric) forms, forms in which short fibers are randomly oriented, etc., but the present invention is not limited to any form. As the resin of the carbon fiber reinforced composite material, for example, thermosetting resins such as epoxy resin, unsaturated polyester resin, vinyl ester resin, phenol resin, epoxy acrylate resin, urethane acrylate resin, phenoxy resin, alkyd resin, urethane resin, maleimide resin, cyanate resin, and thermoplastic elastomers such as polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polytrimethylene terephthalate (PTT) resin, polyethylene (PE) resin, polypropylene (PP) resin, styrene-based resin, polyoxymethylene (POM) resin, polyamide (PA) resin, polycarbonate (PC) resin, polymethyl methacrylate (PMMA) resin, polyvinyl chloride (PVC) resin, polyphenylene sulfide (PPS) resin, polyphenylene ether (PPE) resin, modified PPE resin, polyimide (PI) resin, polyamideimide (PAI) resin, polyetherimide (PEI) resin, polysulfone (PSU) resin, modified PSU resin, polyethersulfone resin, polyketone (PK) resin, polyarylene ether ketone resin (PAEK), polyarylate (PAR) resin, polyether nitrile (PEN) resin, phenol-based resin, phenoxy resin, fluorine-based resins such as polytetrafluoroethylene resin, and furthermore, polystyrene-based resins, polyolefin-based resins, polyurethane-based resins, polyester-based resins, polyamide-based resins, polybutadiene-based resins, polyisoprene-based resins, fluorine-based resins, etc., and copolymers, modified products, and thermoplastic resins blended with two or more of these may also be used.Furthermore, examples of the polyarylene ether ketone resin (PAEK) include polyether ketone (PEK), polyether ether ketone (PEEK), polyether ether ketone ketone (PEEKK), polyether ketone ketone (PEKK), polyether ketone ether ketone ketone (PEKEKK), polyether etherl ketone ether ketone (PEEKEK), polyether ether ether ketone (PEEEK), polyether diphenyl ether ketone (PEDEK), and the like, as well as copolymers, modified products, and resins blended with two or more of these.

[0020] In the present invention, the carbon fiber reinforced composite material needs to form part or all of the skin structure of the propeller blade. As the form of the skin structure, for example, a structure in which a plurality of layers of carbon fiber composite material layers oriented in one direction are stacked may be used, or a structure in which a plurality of layers of carbon fiber reinforced composite material layers in a woven form are stacked may be used. Further, it may be used together with a fiber reinforced composite material using organic fibers such as aramid fibers, polyethylene fibers, polyparaphenylene benzoxazole (PBO) fibers, inorganic fibers such as glass fibers, carbon fibers, silicon carbide fibers, alumina fibers, tyrano fibers, basalt fibers, ceramic fibers, metal fibers such as stainless steel fibers and steel fibers, and other fibers such as boron fibers, natural fibers, and modified natural fibers, or it may be a sandwich structure using a honeycomb core or a porous body.

[0021] The propeller blade of the present invention has a resin layer (resin layer A) in which a plurality of fibrous or ribbon-like conductors and a plurality of non-conductive fiber bundles are embedded in resin on the outer surface side of a structure in which a carbon fiber reinforced composite material is shaped into a propeller shape.

[0022] Here, the conductor has an electrical conductivity of 10 6It refers to substances with a conductivity of 1 S / m or more. The fibrous or ribbon-like conductors that can be preferably used in the present invention are not particularly limited. For example, carbon fibers, metal fibers, metal strips (elongated foil-like metals), mixed fibers of metal fibers and carbon fibers, and carbon fibers coated with metal can be mentioned. Here, each fiber is preferably used in the form of a fiber bundle formed by bundling a plurality of single fibers. As for the metal strip, it is preferable to use one with a thickness of 10 μm or more and 200 μm or less. By using such a conductor, it becomes the lightning strike point during lightning strikes and the current path after lightning strikes. When carbon fibers or carbon fibers coated with metal are used as the conductor, it can contribute to the strength and rigidity of the propeller blade and is suitable. Also, when a material containing metal is used as the conductor, compared with the carbon fiber reinforced composite material that bears the skin layer present inside as seen from the resin layer A, the electrical conductivity is higher, the amount of current reaching this carbon fiber reinforced composite material during lightning strikes decreases, and damage caused by lightning strikes can be suppressed, which is suitable.

[0023] In the present invention, the non-conductive fiber bundle is a collection of a plurality of single fibers with an electrical conductivity of less than 10 6 S / m. The non-conductive fiber bundles that can be preferably used in the present invention are not particularly limited. For example, organic fibers such as aramid fibers, polyethylene fibers, and polyparaphenylene benzoxadole (PBO) fibers, and glass fibers can be mentioned. By using such non-conductive fibers, the lightning strike point during lightning strikes can be induced to the conductor, and thereby the impact caused by lightning strikes can be reduced by the dispersion of the lightning strike point, leading to an improvement in the lightning resistance of the propeller blade. Also, non-conductive fibers generally have a higher elongation than the carbon fibers used in the carbon fiber reinforced composite material present in the inner layer. However, in the present invention, it is preferable to use a non-conductive fiber bundle composed of non-conductive fibers having a higher elongation than the carbon fibers used in the carbon fiber reinforced composite material present in the inner layer. It is preferable to use a non-conductive fiber bundle with an elongation exceeding 2.2%, more preferably a non-conductive fiber bundle with an elongation exceeding 3.5%, and even more preferably a non-conductive fiber bundle with an elongation exceeding 4%. By using such non-conductive fibers, the impact resistance during foreign object collisions can be improved, and the scattering of fragments and the like can be suppressed.

[0024] In the resin layer A, as the mode of the embedded conductor and the non-conductive fiber bundle, for example, it is desirable that the conductor and the non-conductive fiber bundle exist integrally in the form of a woven fabric or a knitted fabric. However, it is not necessarily required that the conductor and the non-conductive fiber bundle have intersections, and the organized conductor and the organized non-conductive fiber bundle may be in a superposed state directly or through a resin layer. Note that the term "organized" refers to a state arranged in a uniaxial direction or a state formed into a network or fabric.

[0025] In the resin layer A, there is no restriction on the arrangement of a plurality of fibrous or ribbon-shaped conductors. However, it is preferable that the plurality of conductors are arranged evenly on the outer periphery of the propeller blade. By arranging them in this way, the region A is easily formed without unevenness, and the current dispersion effect during lightning strike is enhanced. Also, it is not necessary for all the conductors to exist from the root to the tip of the propeller blade, and the number thereof may change in the direction from the root to the tip of the propeller blade according to the surface area of the propeller blade.

[0026] Also, in the resin layer A, there is no particular restriction on the arrangement of a plurality of non-conductive fiber bundles. However, when the non-conductive fiber bundles are arranged evenly, it is preferable because the overall foreign object impact resistance of the propeller blade is improved. Also, when the non-conductive fiber bundles form intersections with each other to form a mesh-like structure, it is preferable because it prevents fragments from scattering during a foreign object impact and leads to an improvement in impact resistance. It may also be in the form of a woven or knitted fabric. Although the specific fabric is not particularly limited, it is preferably in a braided structure formed by fibrous or ribbon-shaped conductors and non-conductive fiber bundles. As a specific example, in the case of a three-axis braided fabric where one axis is a fibrous or ribbon-shaped conductor 101 and the other two axes are non-conductive fiber bundles 102 as shown in FIG. 1, since the non-conductive fiber bundles can wrap the propeller blade without being cut, the impact resistance is further improved, which is preferable.

[0027] In the resin layer A, as the resin (matrix resin) that embeds a plurality of fibrous or ribbon-like conductors and non-conductive fiber bundles, there is no particular limitation as long as it is a resin that can be used for a propeller blade in terms of weather resistance and the like and can hold the conductors and non-conductive fiber bundles. For example, thermosetting resins such as epoxy resin, unsaturated polyester resin, vinyl ester resin, phenol resin, epoxy acrylate resin, urethane acrylate resin, phenoxy resin, alkyd resin, urethane resin, maleimide resin, cyanate resin, and thermoplastic elastomers such as polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polytrimethylene terephthalate (PTT) resin, polyethylene (PE) resin, polypropylene (PP) resin, styrene-based resin, polyoxymethylene (POM) resin, polyamide (PA) resin, polycarbonate (PC) resin, polymethyl methacrylate (PMMA) resin, polyvinyl chloride (PVC) resin, polyphenylene sulfide (PPS) resin, polyphenylene ether (PPE) resin, modified PPE resin, polyimide (PI) resin, polyamideimide (PAI) resin, polyetherimide (PEI) resin, polysulfone (PSU) resin, modified PSU resin, polyether sulfone resin, polyketone (PK) resin, polyarylene ether ketone resin (PAEK), polyarylate (PAR) resin, polyether nitrile (PEN) resin, phenol-based resin, phenoxy resin, fluorine-based resin such as polytetrafluoroethylene resin, and furthermore, polystyrene-based resin, polyolefin-based resin, polyurethane-based resin, polyester-based resin, polyamide-based resin, polybutadiene-based resin, polyisoprene-based resin, fluorine-based resin, etc. These may also be copolymers, modified products, and thermoplastic resins blended with two or more types.Furthermore, examples of the polyarylene ether ketone resin (PAEK) include polyether ketone (PEK), polyether ether ketone (PEEK), polyether ether ketone ketone (PEEKK), polyether ketone ketone (PEKK), polyether ketone ether ketone ketone (PEKEKK), polyether eer ether ketone ether ketone (PEEKEK), polyether ether ether ketone (PEEEK), and polyether diphenyl ether ketone (PEDEK), as well as copolymers, modified products, and resins blended with two or more of these. In particular, in order to improve impact resistance, a resin having higher toughness than the resin used in the carbon fiber reinforced composite material shaped into the above-described propeller shape may be applied.

[0028] In the present invention, the fibrous or ribbon-like conductor in the resin layer A is oriented in the direction from the tip to the root of the propeller blade, and as the arrangement of the conductor and the non-conductive fiber bundle in the resin layer A as viewed from the outside of the propeller blade, it has a region where the conductor is outermost (region A) and a region where the non-conductive fiber bundle is outermost (region B), and is arranged such that a plurality of regions A exist.

[0029] The fact that the conductor is oriented in the direction from the tip to the root of the propeller blade means that the conduction path after lightning strike by the conductor is formed from the tip of the propeller blade toward the root of the propeller blade. Since the skin shape of the propeller blade is formed as a curved surface, when the conductor is oriented and arranged in the direction from the tip to the root of the propeller blade, it generally rarely has a straight shape and is arranged in a curved shape from the tip to the root. Thus, as long as the conduction path after lightning strike by the conductor is formed from the tip of the propeller blade toward the root of the propeller blade, the arrangement of the conductor is not particularly limited, and for example, it may be arranged in a spiral shape.

[0030] Further, the region A is a region where, when the fibrous or ribbon-like conductor contained in the resin layer A is located on the outer layer side of the non-conductive fiber bundle, or when only the conductor is present and the non-conductive fiber bundle is not present, the first component reached when searching in the thickness direction from the outer layer side surface of the resin layer A is not the non-conductive fiber bundle but the conductor.

[0031] Similarly, the region B is a region where, when the non-conductive fiber bundle contained in the resin layer A is located on the outer layer side of the conductor, or when only the non-conductive fiber is present and the conductor is not present, the first component reached when searching in the thickness direction from the outer layer side surface of the resin layer A is not the conductor but the non-conductive fiber bundle.

[0032] Also, in the present invention, for example, as illustrated in FIG. 2, when viewed from the outside of the propeller blade, a plurality of regions A202 are arranged. By arranging a plurality of regions A, the current can be dispersed to the plurality of regions A during lightning strike, the amount of current at each location during lightning strike can be reduced, and a damage reduction effect can be obtained. There is no particular limitation on the density of the region A and the distance between the regions A, but when they are arranged without coarseness, it is preferable because the lightning current can be evenly dispersed. Also, the region A may be intensively arranged at locations where the possibility of lightning strike is particularly high, such as the tip of the propeller blade. In the resin layer A, it is preferable that there are 16 or more regions A in a 5 cm square, more preferably 25 or more regions A in a 5 cm square, and even more preferably 36 or more regions A in a 5 cm square. Although there is no particular limitation on the upper limit, in view of the fact that the effect saturates even if the areal density is increased, it is desirable to set it to 400 or less in a 5 cm square. With such a configuration, lightning strikes can be effectively dispersed. The number of regions A existing in a 5 cm square can be obtained by stacking films cut into 5 cm squares on the outer layer side surface of the resin A and counting the number of regions A existing in the range covered by the films.

[0033] Also, there is no particular limitation on the area ratio between the region A and the region B, but when the area of the region B with respect to the area of the region A (area of the region B / area of the region A) is 5% or more and 600% or less, good lightning resistance can be obtained.

[0034] Further, the difference between the distance (depth) from the outer layer side surface of the resin layer A to the conductor in the overlapping portion of the conductor and the non-conductive fiber in region A and the distance (depth) from the outer layer side surface of the resin layer A to the conductor in the overlapping portion of the conductor and the non-conductive fiber in region B is desirably 40 μm or more. Although there is no upper limit, it does not exceed the thickness of the resin layer A. The difference in the depth from the surface of the resin layer A to the conductor enables effective dispersion of lightning strikes.

[0035] In the present invention, the conductor is configured to be grounded from the propeller mounting portion at the root of the propeller blade. After lightning strikes the propeller blade, the current is controlled to flow from the mounting portion of the propeller blade to the aircraft body. Examples of the grounding method include means of electrically joining the conductor of the resin layer A to the mounting bracket of the propeller blade and electrically joining the mounting bracket on the aircraft body side and the mounting bracket of the propeller blade. Also, it is not necessary for the conductor and the mounting portion of the propeller blade to be directly electrically joined, as long as the conductor and the mounting portion of the propeller blade are finally electrically joined by some method.

[0036] Further, in the present invention, the resin layer A is characterized by forming the outermost layer electrically. The outermost layer electrically means that there is no layer containing a conductive material outside the resin layer A. By adopting such a configuration, the probability of lightning being dispersed and striking in region A provided in the resin layer A is increased, and a sufficient lightning protection effect by region A can be obtained. On the other hand, a layer that does not contain a conductive material, for example, a coating layer containing resin, may be provided on the outer layer of the resin layer A.

[0037] In the present invention, as the arrangement of the conductor and the non-conductive fiber bundle in the resin layer A as viewed from the outside of the propeller blade, it is preferable that the region A is an island and the region other than the region A including the region B is a sea in a "sea-island structure". As an example of this sea-island structure, as shown in FIG. 2(a), a state where the outer periphery of the region A202 is in contact with the other region 201 other than the region A including the region B can be cited. With such a configuration, lightning strikes are more effectively dispersed during lightning strikes, and the impact resistance during foreign object collisions and the effect of preventing fragments from scattering are also improved, which is preferable. In addition, as the region other than the region A including the region B, in addition to the region B, when searching in the thickness direction from the outer layer side surface of the resin layer A, a region that does not reach either the conductor or the non-conductive fiber bundle, that is, a region of only the matrix resin, corresponds to this.

[0038] In the present invention, it is preferable that an insulating layer is provided between the resin layer A and the structure in which the carbon fiber reinforced composite material is shaped into a propeller shape. The current after lightning strikes mainly flows through the conductor contained in the resin layer A. By providing an insulating layer, it is possible to prevent the lightning current from reaching the structure in which the carbon fiber reinforced composite material existing inside as viewed from the resin layer A is shaped into a propeller shape, and damage during lightning strikes can be suppressed. The insulating layer is not particularly limited. For example, a non-conductive fiber reinforced resin layer using organic fibers such as aramid fiber, polyethylene fiber, polyparaphenylene benzoxadole (PBO) fiber, or inorganic fibers such as glass fiber may be provided, or a resin single layer may be provided.

[0039] Furthermore, the propeller blade of the present invention may have a metal receptor electrically connected to the resin layer A. This metal receptor has the effect of attracting lightning strikes to that location and can help suppress damage caused by lightning strikes by using the resin layer A. It is useful to provide it in a region within 20% of the total length of the propeller from the tip of the propeller blade, particularly at the tip of the propeller blade where lightning strikes are likely to occur. Fig. 3 shows an example of a propeller blade equipped with a metal receptor 301 at the tip of the propeller blade. In Fig. 3, the electrical connection between the metal receptor 301 and the conductor in the resin layer A302 is not shown. There is no particular limitation on the material of the metal receptor, but when it is an aluminum alloy, it is lightweight and suitable.

[0040] Also, for the propeller blade of the present invention, it is preferable that all or part of the plurality of fibrous or ribbon-like conductors in the resin layer A have electrical junctions on the side of the surface opposite to the outside of the propeller blade of the resin layer A. By electrically joining at least some of the plurality of conductors on the side of the surface opposite to the outside of the propeller blade of the resin layer A, it becomes possible to reduce the resistance when the current flows through the conductor after a lightning strike. Referring to Fig. 4 for explanation, in this example, the conductor 404 extends in the depth direction, the non-conductive fiber bundle 401 extends in the left-right direction, and on the inner layer side, the conductor 405 is in contact with the conductor 404 and is electrically joined. At this time, since it is electrically joined on the side of the surface opposite to the outside of the propeller blade of the resin layer A, the lightning strike dispersion effect by the region A is not impaired. As a method of electrically joining the conductors on the side of the surface opposite to the outside of the propeller blade of the resin layer A, for example, a method of arranging metal strips so as to contact a plurality of conductors on the side opposite to the outside of the propeller blade of the fibrous or ribbon-like conductor is shown, but it is not limited to this.

[0041] In addition, for the propeller blade of the present invention, it is preferable that the electrical conductivity of the conductor is higher than the electrical conductivity of the carbon fibers contained in the carbon fiber composite material layer existing on the inner layer side of the resin layer A. By adopting such a configuration, it is suitable that no current flows through the carbon fiber composite material layer after lightning strike. As a method for measuring the electrical conductivity of carbon fibers, for example, it can be determined by the method of JIS R 7609. For carbon fibers that have already become a composite material, it may be measured after ashing the matrix resin. The electrical resistance of the conductor may also be measured by the method of JIS R 7609, or by other methods.

Example

[0042] Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not construed as being limited to the descriptions of the items of such examples.

[0043] (Example 1) Polymethacrylimide rigid foam ROHACELL (registered trademark) 110 IG-F manufactured by Polyplastics Co., Ltd. was machined into the core shape of a propeller blade to obtain a porous core. Next, a carbon fiber fabric TRECA (registered trademark) fabric CK6273C manufactured by Toray Industries, Inc. was cut out into the shape of a propeller blade skin. The cut base materials were preformed in four plies each on the upper and lower surfaces of the porous core.

[0044] Subsequently, using a braiding machine (301-TE) manufactured by Kokubun Co., Ltd., a cylindrical base material (a triaxial braiding base material) having a triaxial braided structure composed of 0-degree yarns and ±45-degree yarns was produced. The number of yarns of each yarn was 36 yarns (a total of 108 yarns). As the 0-degree yarn, carbon fiber TRECA (registered trademark) T700SC-12000 manufactured by Toray Industries, Inc. was used, and as the ±45-degree yarn, glass roving RS 220 RL-510 manufactured by Nitto Boseki Co., Ltd. was used.

[0045] The porous core preformed with the previously obtained carbon fiber fabric was inserted into the cylindrical space of the produced triaxial braiding base material to obtain a propeller blade preform.

[0046] As the resin, a two-component epoxy resin (main agent: manufactured by Momentive, curing agent: manufactured by Toray Industries, Inc., acid anhydride-based curing agent) was used.

[0047] The propeller blade preform was placed in a mold preheated to 120°C, and a mold clamping process, a resin injection process using the above resin, a pressure impregnation process, and a demolding process were performed to obtain a propeller blade molded product. In the obtained molded product, there were 40 regions A, each with a size of 5 cm square.

[0048] (Example 2) A propeller blade molded product was obtained in the same manner as in Example 1, except that a copper strip with a width of 4 mm and a thickness of 30 μm was used as the 0-degree yarn of the braiding base material. In the obtained molded product, there were 40 regions A, each with a size of 5 cm square.

[0049] (Example 3) Using the braiding machine used in Example 1, a cylindrical base material (biaxial braiding base material) with a biaxial braided structure composed of ±45-degree yarns was produced. The number of yarns in each direction was 36 (72 in total). As the ±45-degree yarns, glass rovings RS 110 QL-520 manufactured by Nitto Boseki Co., Ltd. were used.

[0050] The porous core and the carbon fiber fabric preform obtained in the same manner as in Example 1 were inserted into the cylindrical space of the obtained biaxial braiding base material, and then a copper strip with a width of 4 mm and a thickness of 20 μm was wound around the center of the longitudinal direction of the propeller blade once in the chord direction. Thereafter, in the same manner as in Example 1, after covering with the same triaxial braiding base material as that obtained in Example 1, a propeller blade molded product was obtained.

[0051] (Example 4) Using a braiding machine (301-TE) manufactured by Kokubun Co., Ltd., a cylindrical base material (biaxial braiding base material) of a biaxial braided structure composed of ±45-degree yarns was produced. The number of yarns for each yarn was 36 (72 yarns in total). As the ±45-degree yarns, NITTO BOSEKI CO., LTD. glass roving RS 220 RL-510 was used.

[0052] After that, the biaxial braiding base material was placed on the porous core preformed with the carbon fiber fabric prepared in the same manner as in Example 1, and then the same triaxial braiding base material as that obtained in Example 1 was placed on it. Thereafter, a propeller blade molded product was obtained in the same manner as in Example 1.

[0053] (Example 5) When placing and molding the porous core covered with the triaxial braiding base material in the mold, a propeller blade molded product was obtained in the same manner as in Example 1, except that an A2017 aluminum alloy thin plate was previously placed in the mold from the tip of the propeller blade to the position of 5% of the total length of the propeller.

[0054] (Comparative Example 1) Using the braiding machine used in Example 1, a cylindrical base material (triaxial braiding base material) of a triaxial braided structure composed of 0-degree yarns and ±45-degree yarns was produced. The number of yarns for each yarn was 36 (108 yarns in total). As the yarns, NITTO BOSEKI CO., LTD. glass roving RS 220 RL-510 was used.

[0055] The obtained triaxial braiding base material was placed on the porous core preformed with the carbon fiber fabric obtained in the same manner as in Example 1, and then a propeller blade was obtained in the same manner as in Example 1.

[0056] (High-current physical damage test) A current of 2 kA was applied to the obtained propeller blade at a position 25% of the total length of the propeller from the tip of the propeller blade, and the size of the damage was measured. The size of the damage was visually judged, and those with small damage were marked as ◎, those with the next smallest damage were marked as 〇, and those with large damage were marked as ×. The results are shown in Table 1.

[0057] (Gelatin Impact Test) For the obtained propeller blade, gelatin formed into a cylindrical shape with a diameter of 100 mm and a weight of 500 g and a density of 1010 kg / m 3 was made to collide at a speed of 500 km / h in the chord direction from the tip of the propeller blade to a point 25% of the total length of the propeller, and the size of the damage was measured. The damage was judged visually, and those with little damage were marked as ◎, those with the next smallest damage were marked as 〇, and those with significant damage were marked as ×. The results are shown in Table 1.

[0058]

Table 1

Industrial Applicability

[0059] The propeller blade according to the present invention is excellent in lightning resistance and impact resistance, and can be suitably used for propellers such as UAM and drones.

Explanation of Reference Numerals

[0060] 101, 404: Conductor (Conductive Fiber) 102, 403: Non-Conductive Fiber 103: Direction from the tip to the root of the propeller blade 201: Region other than Region A 202: Region A 301: Metal Receptor 302: Resin Layer A 303: Foam Core 405: Conductor

Claims

1. On the outer surface side of a structure in which a carbon fiber reinforced composite material is shaped into a propeller shape, there is a resin layer (this layer is referred to as "resin layer A" for convenience) in which a plurality of fibrous or ribbon-like conductors and a plurality of non-conductive fiber bundles are embedded in resin. The conductor is oriented in the direction from the tip to the root of the propeller blade, and as for the arrangement of the conductor and the non-conductive fiber bundle in the resin layer A as viewed from the outside of the propeller blade, there is a region where the conductor is outermost (this part is referred to as "region A" for convenience) and a region where the non-conductive fiber bundle is outermost (this part is referred to as "region B" for convenience), and there are a plurality of regions A arranged. And the conductor is configured to be grounded from the propeller attachment part at the root of the propeller blade, and the resin layer A forms the outermost layer electrically. A propeller blade characterized by this.

2. The propeller blade according to claim 1, wherein the arrangement of the conductor and the non-conductive fiber bundle in the resin layer A as viewed from the outside of the propeller blade is a sea-island structure where region A is an island and the region other than region A including region B is the sea.

3. The propeller blade according to claim 1 or 2, having an insulating layer between the resin layer A and the structure.

4. The propeller blade according to claim 1 or 2, wherein in the resin layer A, there are 16 or more regions A with a side length of 5 cm.

5. Furthermore, it has a metal receptor, and the metal receptor is electrically joined to the resin layer A. The propeller blade according to claim 1 or 2.

6. The propeller blade according to claim 5, wherein the metal receptor is formed in a region within 20% of the total length of the propeller from the wing tip of the propeller blade.

7. The propeller blade according to claim 1 or 2, wherein all or part of the plurality of conductors have electrical joints on the side of the opposite surface as viewed from the outside of the propeller blade of the resin layer A.

8. The propeller blade according to claim 1 or 2, wherein the conductor and the non-conductive fiber bundle form a braided structure and are embedded in the resin layer A.

9. The propeller blade according to claim 1 or 2, wherein the conductor is carbon fiber, metal fiber, carbon fiber coated with metal, or a mixed fiber thereof or a metal strip.

10. The propeller blade according to claim 1 or 2, wherein the electrical conductivity of the conductor is higher than the electrical conductivity of the carbon fibers contained in the carbon fiber composite material layer existing on the inner layer side of the resin layer A.

11. The propeller blade according to claim 1 or 2, wherein the non-conductive fiber bundle is composed of organic fibers or glass fibers.

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