Propeller blade

Abstract

To provide a propeller blade structure that satisfies both high productivity and foreign matter collision resistance.SOLUTION: A propeller blade has a structure in which a first member which includes one or a plurality of layers of fiber-reinforced composite material constituting a blade top face, and a second member which includes one or a plurality of layers of fiber-reinforced composite material constituting a blade bottom face are overlaid, where the first member and the second member form a bonding part at least at a blade front edge part and a blade rear edge part. In the bonding part, layers of the fiber-reinforced composite material of the innermost layers of the first member and the second member are bonded directly or via a connection member, and the layer of the fiber-reinforced composite material of the innermost layer of the first member and the layer of the fiber-reinforced composite material of the innermost layer of the second member, and the connection member satisfy specified conditions.SELECTED DRAWING: Figure 2

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 as it rotates 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] Reducing the weight of the propeller blade contributes to an increase in the payload and range of an aircraft. Therefore, high-strength and high-rigidity fiber-reinforced materials are used as structural materials. However, since the propeller blade has a complex shape as described above, its molding difficulty is high and mass production at a high build rate is difficult.

[0004] On the other hand, in recent years, many aircraft having a large number of propeller blades, such as Urban Air Mobility (UAM) and drones, have been actively developed, and in the future, it will be necessary to produce propeller blades at a higher build rate than before.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, aircraft equipped 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 demand for weight reduction, especially for propeller blades with a large number of blades per aircraft. To meet this weight reduction demand, fiber-reinforced composite materials with high specific strength and high specific stiffness are applied to the propeller blades.

[0007] Particularly when using fiber-reinforced composite materials for the skin of the propeller blade, the effects of the high specific strength and specific stiffness of the fiber-reinforced composite materials can be easily obtained. When manufacturing the skin of the propeller blade with fiber-reinforced composite materials, it is often formed by dividing the upper and lower skins and shaping the fiber-reinforced composite materials. For example, in Patent Document 1 and Patent Document 2, the upper and lower fiber-reinforced composite material skins are joined at the leading edge and trailing edge of the blade to form the propeller blade shape.

[0008] On the other hand, since the propeller blade is operated by rotating at high speed, it has a risk of colliding with various foreign objects such as birds, hailstones, and ricochet stones at high speed. Therefore, the propeller blade is required to have collision resistance against such foreign objects. As described above, when joining the upper and lower fiber-reinforced composite material skins at the leading edge and trailing edge of the blade to form the propeller blade shape, there is a risk of cracks entering from the joint at the leading edge of the blade and causing damage during a foreign object collision.

[0009] In response to such problems, for example, Patent Document 3 discloses a method of shifting the parting position from the leading edge. However, it is difficult to implement high-volume production using this method, and it is not suitable for propeller blades for UAM and drones.

[0010] As described above, the conventional technology has problems in achieving both productivity and foreign object collision resistance. Therefore, the present invention provides a propeller blade structure that achieves both high productivity and foreign object collision resistance.

Means for Solving the Problems

[0011] In order to solve such problems, the present invention adopts the following means. [1] A propeller blade having a structure in which a first member including one or more layers of fiber-reinforced composite material layers constituting the upper surface of the blade and a second member including one or more layers of fiber-reinforced composite material layers constituting the lower surface of the blade are overlapped, wherein the first member and the second member form a joint portion at least at the leading edge portion and the trailing edge portion of the blade, and at the joint portion, the first member and the second member are joined such that the innermost layer of the fiber-reinforced composite material layer is directly or through a connecting member, and the innermost layer of the fiber-reinforced composite material layer of the first member, the innermost layer of the fiber-reinforced composite material layer of the second member, and the connecting member satisfy the following Condition 1 and Condition 2.

[0012] Condition 1: The innermost layer of the fiber-reinforced composite material layer of the first member, the innermost layer of the fiber-reinforced composite material layer of the second member, and the connecting member are composed of a fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented.

[0013] Condition 2: The uniaxially oriented reinforcing fibers included in the innermost layer of the fiber-reinforced composite material layer of the first member, the innermost layer of the fiber-reinforced composite material layer of the second member, and the connecting member are oriented in the range of -10 degrees to +10 degrees with respect to the root direction (blade length direction) from the tip of the propeller blade, and the orientation angle of the reinforcing fibers is within 5 degrees between adjacent innermost layers or connecting members. [2] The propeller blade according to [1] above, having a third member including one or more layers of fiber-reinforced resin layers existing on the inner layer side so as to straddle the joint portion of the first member and the second member at the joint portion on the leading edge side of the blade, wherein the outermost layers on the first member and the second member sides of the third member are composed of a fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented, and the orientation angle of the reinforcing fibers is within 5° with respect to both the reinforcing fibers included in the innermost layer of the first member and the reinforcing fibers included in the innermost layer of the second member. [3] The propeller blade according to [1], characterized in that on the outer surface side of the joint portion on the leading edge side of the wing, an external protective layer is provided so as to straddle the joint portion. [4] The propeller blade according to [2], satisfying the following Condition 3 or Condition 4.

[0014] Condition 3: At least one of the innermost layer of the first member, the innermost layer of the second member, and the reinforcing fibers included in the connecting member is interrupted with a fiber length of 10 to 100 mm in the joint portion and the portion forming the peripheral edge thereof.

[0015] Condition 4: The reinforcing fibers included in the outermost layer on the first member and second member sides of the third member are interrupted with a fiber length of 10 to 100 mm in a range corresponding to the length of the joint portion from the separation point of the joint portion of the first member and the second member as a starting point. [5] The propeller blade according to any one of [1] to [4], characterized in that both or either one of the first member and the second member has a porous body or a hollow molded body inside at the leading edge side joint portion of the wing, and the surface shape of the porous body or the hollow molded body on the inner layer side of the wing has a convex shape. [6] The propeller blade according to any one of [1] to [5], characterized in that the innermost layer of the fiber reinforced resin layer included in the first member and the second member is not covered by a layer outside the innermost layer at the leading edge and trailing edge of the wing. [7] The propeller blade according to any one of [1] to [6], further having a porous core, and the porous core is included inside the first member and the second member. [8] Preparing a member including one or more layers of fiber-reinforced composite materials for forming the upper surface and the lower surface of the blade (Step 1), shaping the member into the respective shapes of the upper surface and the lower surface of the propeller (Step 2), and joining the member forming the upper surface of the propeller (the first member) and the member forming the lower surface of the propeller (the second member) directly or via a connecting member (Step 3). A method for manufacturing a propeller blade, wherein in Step 2, the first member and the second member are shaped so as to be joinable at least at the leading edge and the trailing edge of the blade, and at the joint, the surfaces of the fiber-reinforced composite materials are shaped to face each other (the layer forming the facing side is referred to as the "innermost layer"), and the layer of the fiber-reinforced composite material of the innermost layer of the first member, the layer of the fiber-reinforced composite material of the innermost layer of the second member, and the connecting member are composed of a fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented, and in Step 2, the shaping is performed so as to satisfy the following Condition 2'. A method for manufacturing a propeller blade, characterized in that.

[0016] Condition 2': The uniaxially oriented reinforcing fibers included in the layer of the fiber-reinforced composite material of the innermost layer of the first member, the layer of the fiber-reinforced composite material of the innermost layer of the second member, and the connecting member are oriented in the range of -10 degrees to +10 degrees with respect to the direction from the tip to the root of the propeller blade (the blade length direction), and the orientation angle is within 5 degrees between adjacent innermost layers or connecting members. [9] The method for manufacturing a propeller blade according to [8] above, wherein in Step 3, pressure is applied to the joint portion by a mold pressing method using a mold having the shape of the upper surface of the propeller blade and a mold having the shape of the lower surface of the propeller blade, and then the joining is performed.

[10] The method for manufacturing a propeller blade according to [8] or [9] above, wherein in Step 3, a porous core member is disposed in the space formed by the first member and the second member, and the porous core member is joined to the first member and the second member.

[11] The method for manufacturing a propeller blade according to

[10] above, wherein the porous core member has a layer of a fiber-reinforced composite material in which reinforcing fibers are uniaxially oriented on the surface in contact with the first member and the second member, satisfying the following Condition 5. Condition 5: The orientation angle between the reinforcing fibers contained in the innermost layer of the fiber-reinforced composite material of the first member and the reinforcing fibers contained in the innermost layer of the fiber-reinforced composite material of the second member is within 5 degrees.

[12] The method for manufacturing a propeller blade according to any one of [8] to

[11] above, characterized in that after Step 2 or Step 3, a shaping step is provided for the portion that becomes the blade edge to make the blade edge a smooth curved surface.

[13] Further, the method for manufacturing a propeller blade according to any one of [8] to

[12] above, characterized by having a step (Step 4) of further joining an external protective layer so as to straddle the joint portion on the outside of the propeller blade at the joint portion between the first member and the second member.

[14] In a step prior to Step 3, a base material in which cuts are made so that the fiber length of the uniaxially oriented reinforcing fibers becomes 10 to 100 mm is applied to the joint portion and the peripheral portion of the joint portion of the innermost layer of the one or more layers of fiber-reinforced composite material, and at least one of the connecting members. The method for manufacturing a propeller blade according to any one of [8] to

[13] above.

[15] In Step 1 or Step 2, an operation of enclosing a porous body or a hollow molded body having a convex shape on the inner layer side surface shape is further performed at a portion that should become the joint portion on the leading edge side of the blade of both or either one of the first member and the second member. The method for manufacturing a propeller blade according to any one of [8] to

[14] above. [Advantages of the Invention]

[0017] According to the present invention, it is possible to provide a propeller blade that can achieve both productivity and high strength reliability. The propeller blade of the present invention is particularly suitable for aircraft that use a large number of propeller blades such as UAM and drones. [Brief Description of the Drawings]

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0019] The propeller blade according to the present invention has a wing shape and obtains thrust by pushing air backward by rotating around a drive shaft. Generally, when applying a fiber-reinforced composite material to a propeller blade to obtain a lightweight, high-rigidity, and high-strength propeller blade, it is preferable to apply the fiber-reinforced composite material to the skin. Here, the skin is a thin plate-like member forming the wing shape of the propeller blade. The propeller blade of the present invention has a wing-shaped skin, and the skin is formed by laminating a fiber-reinforced composite material in which reinforcing fibers are uniaxially or multiaxially oriented.

[0020] Examples of the reinforcing fibers include organic fibers such as aramid fibers, polyethylene fibers, and poly(paraphenylene benzoxazole) (PBO) fibers, inorganic fibers such as glass fibers, carbon fibers, silicon carbide fibers, alumina fibers, chilaro fibers, basalt fibers, and 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. Among these, carbon fibers are preferred in the present invention. Among these reinforcing fibers, they are lightweight and have particularly excellent properties in terms of specific strength and specific modulus, and are also excellent in heat resistance and chemical resistance. Furthermore, polyacrylonitrile (PAN)-based carbon fibers, from which high-strength carbon fibers can be easily obtained, are more preferred.

[0021] When the reinforcing fibers are uniaxially oriented, it means that the reinforcing fibers are oriented in a certain one direction, and for example, unidirectional prepregs and unidirectional fabrics correspond to this. Also, when the reinforcing fibers are multi-axially oriented, it means that there is a state where reinforcing fibers are oriented in a plurality of directions within one layer, and for example, a fabric-like fiber base material corresponds to this. Generally, in fiber-reinforced composite materials, the material properties vary greatly depending on the fiber orientation direction. For example, when a tensile load is applied in the direction in which the fibers are oriented and when a tensile load is applied in a direction orthogonal to the direction in which the fibers are oriented, generally, when a tensile load is applied in the direction in which the fibers are oriented, both the strength and rigidity increase. On the other hand, various loads are applied to the propeller blade during operation. For this reason, generally, it is not the case that all the reinforcing fibers constituting the skin of the propeller blade are oriented in the same direction, and the propeller blade is generally included in a state where the reinforcing fibers are oriented in a plurality of directions as a whole. In the present invention, it is possible to control the orientation direction of the uniaxially or multi-axially oriented fiber-reinforced composite material for each layer and control the mechanical properties of the propeller blade skin.

[0022] Also, the reinforcing fibers used in the present invention are not particularly limited, and they may be short fibers or continuous fibers, but it is preferable to use continuous fibers from the viewpoint of improving the strength reliability of the propeller blade.

[0023] In addition, the fiber-reinforced composite material in the present invention is a material in which the above-described reinforcing fibers are impregnated with a resin. The type of resin is not particularly limited. 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 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, fluororesin 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, fluororesin, etc., and copolymers, modified products, and thermoplastic resins blended with two or more of these may also be used. Further, as the polyarylene ether ketone resin (PAEK), for example, polyether ketone (PEK), polyether ether ketone (PEEK), polyether ether ketone ketone (PEEKK), polyether ketone ketone (PEKK), polyether ketone ether ketone ketone (PEKEKK), polyether ether ketone ether ketone (PEEKEK), polyether ether ether ketone (PEEEK), and polyether diphenyl ether ketone (PEDEK), etc., and copolymers, modified products, and resins blended with two or more of these may also be used.In the present invention related to the manufacturing method, the meaning of "fiber-reinforced composite material" includes the material in the state before curing when a thermosetting resin or a radiation-curable resin is used.

[0024] The structure of the skin is not particularly limited. For example, in the case of a structure divided into an upper skin having the upper wing shape of the propeller blade and a lower skin having the lower wing shape of the propeller blade, the productivity can be improved, which is preferable. Also, a porous body or a honeycomb core may be provided in the skin to form a sandwich structure.

[0025] In the propeller blade of the present invention, the structure on the inner layer side of the skin is not particularly limited. For example, a porous body may be arranged and used as a core material, or a hollow structure may be formed, and a reinforcing structure such as a shear web that connects the skin in the thickness direction of the wing and extends in the wing length direction may be provided.

[0026] The propeller blade according to the present invention is a propeller blade having a structure in which a first member including one or more layers of fiber-reinforced composite material layers constituting the upper surface of the wing and a second member including one or more layers of fiber-reinforced composite material layers constituting the lower surface of the wing are overlapped, and the first member and the second member form a joint portion at least at the leading edge portion and the trailing edge portion of the wing. At the joint portion, the first member and the second member are joined such that the innermost layer of the fiber-reinforced composite material layer is directly or via a connecting member, and the innermost layer of the fiber-reinforced composite material layer of the first member, the innermost layer of the fiber-reinforced composite material layer of the second member, and the connecting member satisfy the following Condition 1 and Condition 2.

[0027] Condition 1: The innermost layer of the fiber-reinforced composite material layer of the first member, the innermost layer of the fiber-reinforced composite material layer of the second member, and the connecting member are composed of a fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented.

[0028] Condition 2: The layers of the fiber-reinforced composite material in the innermost layer of the first member, the layers of the fiber-reinforced composite material in the innermost layer of the second member, and the unidirectionally oriented reinforcing fibers included in the connecting member are oriented within a range of -10 degrees to +10 degrees with respect to the direction from the tip to the root (blade length direction) of the propeller blade, and the orientation angle is within 5 degrees between adjacent innermost layers or the connecting member.

[0029] Incidentally, to avoid misunderstanding, it should be noted that since the connecting member can be used arbitrarily, when the connecting member is not provided, the "layers of the fiber-reinforced composite material in the innermost layer of the first member and the layers of the fiber-reinforced composite material in the innermost layer of the second member" in Condition 1 means "the layers of the fiber-reinforced composite material in the innermost layer of the first member, the layers of the fiber-reinforced composite material in the innermost layer of the second member, and the connecting member", and Condition 2 "the unidirectionally oriented reinforcing fibers included in the layers of the fiber-reinforced composite material in the innermost layer of the first member, the layers of the fiber-reinforced composite material in the innermost layer of the second member, and the connecting member" means "the unidirectionally oriented reinforcing fibers included in the layers of the fiber-reinforced composite material in the innermost layer of the first member and the layers of the fiber-reinforced composite material in the innermost layer of the second member" (the same applies to Condition 2' and Condition 3).

[0030] Here, referring to FIG. 1 for explanation, the first member including the layer or layers of the fiber-reinforced composite material constituting the upper surface of the blade corresponds to the member 101 that becomes the skin of the upper surface of the blade, and the second member 102 including the layer or layers of the fiber-reinforced composite material constituting the lower surface of the blade corresponds to the member 102 that becomes the skin of the lower surface of the blade. These first and second members include one or more layers of the fiber-reinforced composite material layer, and the layer structure is laminated in the thickness direction of the propeller blade.

[0031] The first member and the second member form a joint portion at least at the leading edge portion and the trailing edge portion of the blade. The embodiment shown in FIG. 1 is an example having joint portions 105 and 106 at the leading edge 103 and the trailing edge 104 of the blade. Such a structure in which the upper and lower skins of the propeller blade are joined at the leading and trailing edges of the blade is simple and easy to manufacture.

[0032] Further, in the propeller blade of the present invention, at the joint of the first member and the second member, the innermost layer of the fiber-reinforced composite material at the joint of the first member and the second member is joined directly or via a connecting member. This will be described with reference to FIG. 2. In the example of FIG. 2(a), at the joint 202 of the first member 203 and the second member 204, the innermost layer 201 of the fiber-reinforced composite material of the first member 203 and the innermost layer 201 of the fiber-reinforced composite material of the second member 204 are directly joined at the joint 202. In the example of FIG. 2(b), a connecting member 204 is arranged between the innermost layer 201 of the fiber-reinforced composite material of the first member 203 and the innermost layer 201 of the fiber-reinforced composite material of the second member 204, and the first member 203 and the second member 204 are joined via the connecting member 204. In the present invention, the connecting member may be a single-layer reinforcing fiber layer or a layer made of a fiber-reinforced composite material, or may be a plurality of reinforcing fiber layers or a layer made of a plurality of fiber-reinforced composite materials. In this case, the reinforcing fibers included in the connecting member are uniaxially oriented reinforcing fibers, and it is preferable that the orientation direction of the reinforcing fibers is oriented from the tip to the root direction (wing length direction) of the propeller blade. Further, when the connecting member is a layer made of a plurality of reinforcing fiber layers or a plurality of fiber-reinforced composite materials, it is preferable that all the reinforcing fibers included in the layer are uniaxially oriented with respect to the root direction (wing length direction) of the propeller blade from the tip.

[0033] Here, the wing length direction of the propeller blade is the direction from the root to the tip of the propeller blade. This refers to the long side direction of the rectangle with the smallest area among the rectangles circumscribing the image in the projected image obtained by projecting parallel light rays such as natural light perpendicularly to the rotation plane of the propeller blade (for convenience, referred to as the "circumscribing rectangle"). Further, the state in which the reinforcing fibers are oriented with respect to the wing length direction means that the reinforcing fibers are oriented within a range of 10° with respect to the wing length direction, and the reinforcing fibers oriented within this range mainly bear the force applied in the longitudinal direction of the propeller blade. As described above, since the propeller blade has a complex airfoil shape, it is difficult to exactly align the fiber orientation direction with the wing length direction. On the other hand, the chord direction is the short side direction of the circumscribing rectangle.

[0034] The propeller blade of the present invention satisfies the above-mentioned condition 1 and condition 2.

[0035] With such a configuration, for example, when a flying object collides with the leading edge of the wing and a crack develops from the tip of the leading edge joint of the propeller blade, the crack will develop in a direction orthogonal to the fiber orientation direction. Therefore, it becomes difficult for the crack to progress linearly, and fiber bridging is also likely to occur. Thus, it is possible to suppress the destruction caused by the progress of the crack from the joint, and in the layer between the joints, since materials with substantially the same elastic modulus in the fiber orthogonal direction are used, anisotropy of the elastic modulus of the material does not occur and the stress between the layers is reduced. Also, due to being pressed during joining at the joint, the reinforcing fibers contained in the innermost layer and the connecting member are press-fitted into each other, and the interface between the innermost layer of the first member and the innermost layer of the second member, or the interface between the innermost layer of the first member, the innermost layer of the second member and the connecting member becomes a complex shape. For example, when a flying object collides with the leading edge of the wing, the progress of the crack from the tip of the leading edge joint of the propeller blade is suppressed, and the destruction caused by the progress of the crack from the joint can be suppressed. Incidentally, the orientation angle of the reinforcing fibers contained in each layer and the joint member can be measured by a fluoroscopy method such as a CT scan.

[0036] Further, the propeller blade of the present invention has a third member including one or a plurality of layers of fiber-reinforced resin layers existing on the inner layer side so as to straddle the joint of the first member and the second member at the joint on the leading edge side of the wing. The outermost layers on the first member and second member sides of the third member are constituted by a fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented, and it is preferable that the orientation angle of the reinforcing fibers is within 5° with respect to both the reinforcing fibers contained in the innermost layer of the first member and the reinforcing fibers contained in the innermost layer of the second member.

[0037] Explaining with reference to FIG. 3, the third member 301 is arranged so as to straddle the joint 501 of the first member and the second member.

[0038] The third member needs to include one or more layers of fiber-reinforced resin. Among these layers of fiber-reinforced resin, it is preferable that the outermost layer of the fiber-reinforced resin layer is in contact with the innermost layer of the first member and the innermost layer of the second member. The reinforcing fibers included in the third member have an orientation angle within 5° with respect to the reinforcing fibers of the innermost layer of the first member and the innermost layer of the second member. With such a configuration, cracks will progress in a direction orthogonal to the fiber orientation direction, so that anisotropy of the material elastic modulus does not occur between layers at the joint and the interlayer stress is reduced, and single fibers are likely to mix with each other between layers at the joint, making it difficult to form distinct layers. Therefore, it becomes difficult for cracks to progress, and crack propagation from the tip of the leading edge joint of the propeller blade can be suppressed. There are no particular restrictions on the fiber-reinforced resin layers other than the outermost layer when the third member includes a plurality of layers of reinforced fiber resin layers. It may be a resin layer of unidirectionally oriented reinforcing fibers, or a fiber-reinforced resin layer containing multi-axially oriented reinforcing fibers.

[0039] Further, the propeller blade of the present invention preferably has an external protective layer on the outer surface side of the joint portion on the leading edge side of the blade, so as to straddle the joint portion. Explaining with reference to FIG. 4, the external protective layer 401 exists on the outer layer side of the joint portion of the first member and the second member so as to straddle the joint portion. As shown in FIG. 4, it is preferable that the inside of the external protective layer is in direct contact with the first member and the second member. The material of the external protective layer is not limited, and it may be composed of a fiber-reinforced composite material, or may be made of metal, especially aluminum alloy. Also, the external protective layer may be attached via an adhesive, or may be joined by mechanical fastening, and it may be joined in any state as long as the impact applied to the external protective layer from the leading edge to the trailing edge direction of the propeller blade is dispersed and transmitted to the first member and the second member. Further, since the outer surface of the external protective layer forms a part of the blade shape, it is desirable that the first member and the second member are smoothly joined at the end of the external protective layer. As shown in FIG. 4, it is preferable to provide recesses for providing the external protective layer to the first member and the second member in advance. By adopting such a configuration, for example, when foreign objects such as birds, stones, and hailstones collide with the propeller blade, it is possible to suppress the breakage due to the progress of cracks from the joint portion of the first member and the second member.

[0040] Further, in the propeller blade of the present invention, it is preferable to satisfy the following Condition 3 or Condition 4.

[0041] Condition 3: At least one of the innermost layer of the first member, the innermost layer of the second member, and the reinforcing fibers included in the connecting member is interrupted with a fiber length of 10 to 100 mm in the portion forming the joint portion and its peripheral portion.

[0042] Condition 4: The reinforcing fibers included in the outermost layer on the first member and second member sides of the third member are interrupted with a fiber length of 10 to 100 mm in the range of a length corresponding to the length of the joint portion from the separation point of the joint portion of the first member and the second member as a starting point.

[0043] In the present invention, the "separation point of the joint" is a point at which the joint between the first member and the second member is released on the inner layer side of the joint, that is, the side inside the propeller blade. When a joint member is used, it is a point at which the joints between the first member, the second member, and the joint member are released (see reference numeral 501 in FIG. 3). Further, the "peripheral edge portion of the joint" is a region included in the length between the separation point of the joint and the outer layer side end point of the joint from the separation point of the joint, and is a circular region in the chordwise cross-section of the propeller blade within the range of the line segment length connecting the separation point and the outer layer side end point.

[0044] The state in which the reinforcing fibers are interrupted with a fiber length of 10 to 100 mm is, for example, a state obtained by inserting a cut 603 into a prepreg containing continuously oriented fibers in one direction, such as the reinforcing fibers 602 shown in FIG. 5, or a state in which short fibers with a fiber length of 10 to 100 mm are oriented. In particular, when using a cut prepreg in which a cut is inserted into a prepreg containing continuous fibers, there are no particular restrictions on the cut insertion pattern. In the joint, when any of the reinforcing fibers of the innermost layer of the first and second members, the connecting member, and the outermost layer of the third member are interrupted with a fiber length of 10 to 100 mm, the boundary between the respective layers becomes unclear. For example, when a foreign object such as a bird, a stone, or hail collides with the propeller blade, it is possible to suppress the destruction due to the propagation of cracks at the joint between the first member and the second member.

[0045] In addition, in the propeller blade of the present invention, it is preferable that either or both of the first member and the second member have a porous body or a hollow molded body inside at the leading edge side joint portion, and the surface shape of the porous body or the hollow molded body on the inner layer side of the blade has a convex shape. The porous body or the hollow molded body can be arranged, for example, like 703 in FIG. 6. By 703, the innermost reinforcing fiber layer of the first member 701 including a plurality of layers of fiber-reinforced composite material layers and the second member 702 including a plurality of layers of fiber-reinforced composite material layers has a large change in the layer shape from the outer shape of the blade, and the chordwise length of the joint portion can be increased. Further, since the surface shape of the porous body or the hollow molded body arranged on the inner layer side of the blade is convex at least in part, it is preferable that the chordwise length of the joint portion can be increased. It is desirable that the convex shape exists at the leading edge side joint portion of the blade, and by the existence of the convex shape at such a position, it is preferable that the chordwise length of the joint portion can be increased. As long as it is a convex shape, the shape on the inner layer side of the blade is not particularly limited, and it may be a curved convex shape or a convex shape composed of a plurality of planes. In this way, it is preferable to arrange the porous body or the hollow molded body at least in one of the first and second members at the leading edge side joint portion to increase the chordwise joint portion area on the leading edge side of the blade. At this time, it is preferable to apply a porous body having an independent bubble structure so that the resin is not impregnated during the molding of the first member and the second member for the porous body, and similarly for the hollow molded body, it is preferable to apply a member having a closed cross-section structure so that the resin is not impregnated during the molding of the first member and the second member. By adopting such a configuration, it is possible to achieve improvements in the moldability, lightweight property, and impact resistance of the propeller blade.

[0046] In addition, for the propeller blade of the present invention, it is preferable that the innermost layer of the fiber-reinforced resin layers included in the first member and the second member is not covered by a layer outside the innermost layer at the leading edge and the trailing edge of the blade. For example, in FIG. 2, the layer structure of the fiber-reinforced resin layer is exposed on the outer layer side at 203 and is not covered by a layer outside the innermost layer. At this time, for example, even if the exposed portion is located on the inner layer side of the outer protective layer and is protected, it is exposed on the outer layer side of the first and second members and is not covered by a layer outside the innermost layer. Such a structure can also be obtained, for example, by forming a pride drop structure at the leading edge or the trailing edge of the blade during molding, or by molding the base material to protrude from the blade shape at the leading edge or the trailing edge of the blade and then machining it into the blade edge shape by machining. By adopting such a configuration, the joint portion of the first and second members can be formed long at the blade edge, and an improvement in impact resistance can be achieved.

[0047] In addition, the propeller blade of the present invention includes a porous core, and it is preferable that the porous core is included inside the first member and the second member. Here, the "porous core" is a member having an outer surface with a shape corresponding to the shape of the inner surface of the first member and the second member made of a porous material. By arranging the porous core inside the first member and the second member, the first member and the second member can be shaped into the shape of a propeller blade using the porous core, and the productivity can be increased. In particular, when using the third member, first, a member to be the third member is arranged at a position corresponding to the leading edge portion of the propeller blade of the porous core, and then, when arranging the members to be the first member and the second member for shaping, it is particularly suitable. It is also possible to improve the impact resistance by utilizing the mechanical properties of the porous core itself. The material of the porous core is not particularly limited, but in order to suppress the resin from penetrating into the porous core during the molding of the first member and the second member, it is preferable to use a porous core having closed cells.

[0048] In addition, in the method for manufacturing a propeller blade of the present invention, a step of preparing a member including one or a plurality of layers of fiber-reinforced composite materials for forming the upper blade surface and the lower blade surface (step 1), a step of shaping the member into the respective shapes of the upper and lower surfaces of the propeller (step 2), and a step of joining the member forming the upper surface of the propeller (the first member) and the member forming the lower surface of the propeller (the second member) directly or via a connecting member (step 3). In step 2, the first member and the second member are shaped so as to be joinable at least at the blade leading edge portion and the blade trailing edge portion, and at the joining portion, the surfaces of the fiber-reinforced composite materials are shaped so as to face each other (the layer forming the facing side is referred to as the "innermost layer"), and the layer of the fiber-reinforced composite material of the innermost layer of the first member, the layer of the fiber-reinforced composite material of the innermost layer of the second member, and the connecting member are constituted by a fiber-reinforced composite material in which reinforcing fibers are uniaxially oriented, and in step 2, shaping is performed so as to satisfy the following condition 2'.

[0049] Condition 2': The uniaxially oriented reinforcing fibers included in the layer of the fiber-reinforced composite material of the innermost layer of the first member, the layer of the fiber-reinforced composite material of the innermost layer of the second member, and the connecting member are oriented in the range of -10 degrees to +10 degrees with respect to the direction from the tip to the root of the propeller blade (the blade length direction), and the orientation angle is within 5 degrees with respect to an adjacent innermost layer or connecting member.

[0050] When the skin of the propeller blade is made of a fiber-reinforced composite material, for example, by impregnating a fiber-reinforced base material with a resin and using a prepreg in a semi-cured state, and shaping this into a skin shape, a prepreg shaped into the shape of the upper or lower surface of the propeller can be obtained.

[0051] Here, the meaning of "shaping" means deforming an object into a target shape. For example, an operation of placing a sheet-shaped prepreg along a mold is included in this.

[0052] At this time, in order to improve productivity, it is preferable to produce prepregs by dividing the skin of the propeller blade into two, an upper surface skin and a lower surface skin, which also leads to the automation of the prepreg shaping process. The prepregs can be prepared by cutting them according to the shape of the skin laminate structure.

[0053] The prepared prepregs can be shaped to the respective shapes of the upper and lower surfaces of the propeller so as to form the designed laminate structure. When shaping, a flat laminate prepreg obtained by laminating one layer of prepreg or a plurality of prepregs in advance may be shaped, or the prepregs may be shaped and laminated one layer at a time, or after preheating a single layer of prepreg or a laminate prepreg prepared in advance, the single layer of prepreg or the laminate prepreg may be pressed between a mold having the skin outer layer side surface shape and a mold having the skin inner layer side surface shape so as to be shaped into a propeller shape. In this way, a member (first member) forming the upper surface of the propeller and a member (second member) forming the lower surface of the propeller are obtained.

[0054] Subsequently, the first member and the second member thus obtained are superposed and joined directly or via a connecting member at the leading edge and trailing edge of the blade. When using a laminate prepreg shaped into a propeller shape, the joining can be performed by heat-curing molding.

[0055] And in the manufacturing method of the present invention, the innermost layer of the fiber-reinforced composite material layer of the first member, the innermost layer of the fiber-reinforced composite material layer of the second member, and the connecting member are composed of a fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented, and in the step 2, the shaping is performed so as to satisfy the condition 2'.

[0056] When obtaining a propeller blade using a prepreg, by placing a prepreg or prepreg laminate for obtaining the skin forming the upper wing surface and a prepreg or prepreg laminate for obtaining the skin forming the lower wing surface in an uncured state, overlapping them and disposing them in a molding die for curing and molding, at the joint, the layers of the upper surface skin and the lower surface skin are likely to be in a disordered structure, which is suitable for achieving an improvement in impact resistance.

[0057] Also, when using a prepreg - made connecting member to join a prepreg or prepreg laminate for obtaining the skin forming the upper wing surface and a prepreg or prepreg laminate for obtaining the skin forming the lower wing surface via the connecting member, the connecting member may be a single - layer uniaxially - oriented prepreg sheet or a multi - layer uniaxially - oriented prepreg sheet. There is no particular limitation on the method of joining via the connecting member. For example, a connecting member made of prepreg is prepared in advance, joined to a prepreg or prepreg laminate for obtaining the skin forming the lower wing surface, and then joined to a prepreg or prepreg laminate for obtaining the skin forming the upper wing surface.

[0058] In addition, in the manufacturing method of the present invention, the means for joining the first member and the second member is not particularly limited, but it is preferable to use a die having the shape of the upper wing surface of the propeller blade and a die having the shape of the lower wing surface of the propeller blade, determine the relative positional relationship between the first member and the second member in the die, and perform the joining by applying pressure to the joint through the die, that is, by the die - pressing method.

[0059] With the first member and the second member obtained in the step 2 arranged to match the shapes of a die having the shape of the upper wing surface of the propeller blade and a die having the shape of the lower wing surface of the propeller blade, when joining the first and second members directly or via a connecting member by clamping the die and applying pressure to the joint, the positions of the upper and lower skins are accurately determined, and the joint of the upper and lower skins is also accurately formed, so that the impact resistance is improved, which is suitable.

[0060] Also, in the method for manufacturing a propeller blade of the present invention, in the step 3, it is preferable to dispose a porous core member in the space formed by the member forming the upper surface of the propeller and the member forming the lower surface, and join the first member and the second member. There are no particular restrictions on the means for disposing the porous core member in the space formed by the member forming the upper surface of the propeller and the member forming the lower surface. For example, the porous core member is disposed between a prepreg or a prepreg laminate for obtaining a skin forming the upper surface of the blade and a prepreg or a prepreg laminate for obtaining a skin forming the lower surface of the blade, and then heat-cured and molded while pressing from the outer surface. Another method is to dispose a precursor of the porous core member containing a foaming agent in the mold between a prepreg or a prepreg laminate for obtaining a skin forming the upper surface of the blade and a prepreg or a prepreg laminate for obtaining a skin forming the lower surface of the blade, foam the foaming agent to form a porous body, and integrate with the prepreg or the prepreg laminate by utilizing the pressure generated by the foaming.

[0061] Also, in the method for manufacturing a propeller blade of the present invention, it is preferable that the porous core member has a layer of a fiber-reinforced composite material in which reinforcing fibers are uniaxially oriented on the surface in contact with the first member and the second member, satisfying the following condition 5.

[0062] Condition 5: The orientation angle is within 5 degrees between the reinforcing fibers contained in the innermost layer of the fiber-reinforced composite material layer of the first member and the reinforcing fibers contained in the innermost layer of the fiber-reinforced composite material layer of the second member.

[0063] By using such a porous core member, the inside of the propeller blade can be strongly reinforced, leading to an improvement in impact resistance. As a method of providing a layer of a fiber-reinforced composite material in the porous core member, there is a method of laminating a prepreg containing unidirectionally oriented reinforcing fibers on the surface of the porous core member. Further, the layer of the fiber-reinforced composite material in the porous core member may be provided on the entire surface of the porous core, but it is preferably present at least in a portion straddling the joint portion between the first member and the second member. When provided at such a position, the effect of reinforcing the joint between the first member and the second member can be obtained.

[0064] Further, in the method for manufacturing a propeller blade of the present invention, it is preferable to have a shaping step of making the blade edge into a smooth curved surface for the portion that becomes the blade edge after step 2 or step 3. When the blade edge is shaped into a smooth curved surface by machining, a propeller blade shape with suppressed air flow turbulence can be obtained. The means for shaping is not particularly limited, but machining can be performed using a 5-axis machining center or the like. In the manufacturing method of the present invention, since the surfaces of the fiber-reinforced composite materials are shaped so as to face each other at the joint portion, unless the shapes of the ends of the first member and the second member are shaped in advance, in the overlapped state, as shown in FIG. 7, the innermost layer of the first member and the second member and the layers outside thereof are laminated, and there is a possibility that it may not be a curved surface. Thus, by performing shaping to cut off the extra portion (the portion indicated by the dotted line in the portion indicated by reference numeral 801), a smooth curved surface is obtained.

[0065] Furthermore, the method for manufacturing a propeller blade of the present invention preferably further includes a step (step 4) of further joining an external protective layer so as to straddle the joint of the first member and the second member forming the upper surface of the propeller outside the propeller blade. As a method of providing the external protective layer, the first member and the second member may be joined through a joining member as necessary and then provided, or may be provided simultaneously with the joining. At this time, it is preferable to previously provide depressions corresponding to the shape of the external protective layer in the first member and the second member. Examples of the method of providing the depressions include providing them by machining after shaping the first member and the second member into the shape of the upper or lower surface of the propeller blade. There is no particular limitation on the method of installing the external protective layer, and bonding by an adhesive or mechanical bonding may be used. The material of the external protective layer is not particularly limited, and it may be made of a fiber-reinforced composite material, or may be made of metal, particularly aluminum alloy.

[0066] In addition, in the method for manufacturing a propeller blade of the present invention, in a step prior to step 3, in the joint and the peripheral portion of the joint of the layer that becomes the innermost layer of the one or more layers of fiber-reinforced composite material, and in at least one of the connecting members, a step of making a cut so that the fiber length of the uniaxially oriented reinforcing fiber becomes 10 to 100 mm is provided. Note that the "peripheral portion of the joint" is as described above.

[0067] As a method of making a cut so that the fiber length of the uniaxially oriented reinforcing fiber becomes 10 to 100 mm, it is convenient to provide a substrate with a cut. Specifically, a prepreg with a cut inserted into a prepreg containing continuous fibers can be used. In this case, there is no particular limitation on the pattern of the inserted cut. Also, since the cut can be made in a sheet state, it is suitable without impairing workability. By intermittently cutting the fiber length to 10 to 100 mm by the cut, the fiber is likely to be oriented in the layer thickness direction, and the layers are likely to be in a disordered state. For example, when a foreign object such as a bird, a stone, or hail collides with the propeller blade, the progress of cracks at the joint can be suppressed.

[0068] In addition, in the method for manufacturing a propeller blade of the present invention, in Step 1 or Step 2, it is preferable to further perform an operation of enclosing a porous body or a hollow molded body having a convex shape on the surface shape on the inner layer side of the blade at a portion that is to become a joint portion on the leading edge side of the blade of both or either one of the first member and the second member. The method of enclosing the porous body or the hollow molded body in the joint portion on the leading edge side of the blade of the first member or the second member is not particularly limited. When laminating prepregs on a plane to produce a laminated prepreg, the porous body or the hollow molded body may be disposed between the layers, and then the laminated prepreg may be shaped into a propeller shape, or it may be disposed between the layers when shaping the prepreg or the laminated prepreg into a propeller shape.

Example

[0069] Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not to be construed as being limited to the descriptions of the items of such examples.

[0070] Note that the direction from the blade root to the blade tip (blade length direction) is the 0° direction, and the direction from the blade tip to the leading edge of the blade (chord direction) is the 90° direction.

[0071] (Example 1) P707AG-15 carbon fiber unidirectional prepreg manufactured by Toray Composite Materials America, Inc. was prepared and cut into the shape of a propeller blade skin. By cutting, a prepreg (prepreg 1) in which carbon fibers were oriented in the 0° direction and a prepreg (prepreg 2) in which carbon fibers were oriented in the 90° direction were obtained.

[0072] Subsequently, an F6273C-07M carbon fiber woven prepreg manufactured by Toray Composite Materials America, Inc. containing a biaxial orthogonal fabric was prepared and cut into the shape of a propeller blade skin. By cutting, a prepreg (prepreg 3) in which the carbon fibers contained in the biaxial orthogonal fabric were oriented in the +45° direction and the -45° direction, respectively, was obtained.

[0073] The prepregs 1, 2, and 3 were laminated in the order of [prepreg 3 / prepreg 1 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 3 / prepreg 1] from the outer surface side corresponding to the upper skin and the lower skin of the propeller blade, respectively, to obtain a prepreg laminate for the upper skin of the propeller blade and a prepreg laminate for the lower skin of the propeller blade. Note that the innermost prepreg of the laminated prepregs for the upper and lower skins is a unidirectional prepreg in which carbon fibers are oriented in the 0° direction.

[0074] Subsequently, the obtained prepreg laminate for the upper skin was used with a male mold and a female mold having a cavity in the shape of the upper skin of the propeller blade. First, the laminated prepreg was placed on the mold surface while applying tension in the chord direction to the male mold, and then the female mold was overlaid and pressed in the cavity to obtain a laminated prepreg shaped into the upper skin. Also, a laminated prepreg shaped into the lower skin was obtained in the same manner as the upper skin using a male mold and a female mold having a cavity in the shape of the lower skin of the propeller blade.

[0075] Subsequently, Rohacell (registered trademark) 110 IG-F, a polymethacrylimide rigid foam manufactured by Polyplastics Co., Ltd., was machined into the shape of the core of the propeller blade to obtain a porous core.

[0076] Thereafter, the male molds having cavities in the shapes of the upper and lower skins were removed from the upper and lower skins, respectively. The porous core was placed on the inner layer side surface of the exposed propeller blade skin, and was sandwiched using female molds having cavities in the shapes of the upper and lower skins. Subsequently, clamping was performed, and then heat curing molding was carried out in an oven to obtain a propeller blade.

[0077] (Example 2) Toray Composite Materials America, Inc. P707AG-15 carbon fiber unidirectional prepreg was prepared and cut to the shape of the connecting member to obtain a connecting member composed of one layer of the unidirectional prepreg with carbon fibers oriented in the 0° direction. The propeller blade was obtained in the same manner as in Example 1, except that the connecting member was placed on the entire surface of the joint between the laminated prepreg shaped into the upper skin and the laminated prepreg shaped into the lower skin and molded. Note that the connecting member was placed on the laminated prepreg shaped into the lower skin and molded.

[0078] (Example 3) To be placed inside the leading edge of the upper skin of the propeller blade, Rohacell (registered trademark) 110 IG-F, a polymethacrylimide rigid foam manufactured by Polyplastics Co., Ltd., was processed to obtain a porous processed product A. The porous processed product A has a substantially triangular prism shape and a height equal to the length from the blade root to the blade tip. Also, one of the side surfaces is a curved surface that follows the outer surface of the upper skin when installed on the upper skin, another side surface is a flat surface, and another side surface is a curved surface that protrudes when viewed from the ridge lines of the two sides in the length direction.

[0079] In the same manner as in Example 1, prepreg 1 and prepreg 2 were obtained. Among them, for a part of prepreg 1, linear cuts were periodically inserted across the entire surface in the 10° direction with respect to the carbon fiber orientation direction so that all carbon fibers were cut by the cuts and the fiber length after cutting was 30 mm. At this time, the length in the direction orthogonal to the carbon fibers of the cuts was 10 mm (this prepreg with the cuts inserted is referred to as prepreg 1').

[0080] A propeller blade was obtained in the same manner as in Example 1, except that the prepreg thus obtained was used. However, for the upper skin, with respect to the side of the outer surface, a laminated prepreg (laminated prepreg A) laminated in the order of [prepreg 3 / prepreg 1 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 1] and a laminated prepreg (laminated prepreg B) laminated in the order of [prepreg 2 / prepreg 1 / prepreg 3 / prepreg 1'] were obtained from the side of the outer surface, and the porous processed material A was inserted between the laminated prepreg A and the laminated prepreg B at a position corresponding to the separation point of the wing leading edge side joint, and the laminated prepreg A and the laminated prepreg B were laminated. Also, for the lower skin, it was laminated in the order of [prepreg 3 / prepreg 1 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 3 / prepreg 1'] from the side of the outer surface.

[0081] (Comparative Example 1) A propeller blade was obtained in the same manner as in Example 1, except that prepreg 2 was used instead of prepreg 1 for the prepregs on the innermost layer side of the upper skin and the lower skin.

[0082] (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 collided with the propeller blade at a speed of 500 km / h in the chord direction at a position 25% of the total length of the propeller from the tip of the blade, and the size of the damage was measured. The damage was judged visually, and those with small damage were marked as ◎, those with slightly smaller damage were marked as 〇, and those with large damage were marked as ×. The results are shown in Table 1.

[0083]

Table 1

Industrial Applicability

[0084] The hollow structure according to the present invention, particularly a propeller blade, is a propeller blade having a hollow structure that is excellent in productivity, lightweight, and of high quality, and can be suitably used for propellers of UAM (Urban Air Mobility), drones, aircraft, and the like.

Explanation of Signs

[0085] 101, 203, 701: First member 102, 204, 702: Second member 201: Layer of fiber-reinforced composite material of the innermost layer of the first member and the second member 105, 106, 202, 302: Joint part 205: Connecting member 301: Third member 401: External protective layer 501: Separation point of the joint part 601: Orientation direction of reinforcing fibers 602: Reinforcing fibers 603: Notch 703: Porous body or hollow molded body 801: Propeller blade surplus molding

Claims

1. A propeller blade having a structure in which a first member including one or more layers of fiber-reinforced composite material layers constituting the upper surface of the blade and a second member including one or more layers of fiber-reinforced composite material layers constituting the lower surface of the blade are superimposed, wherein the first member and the second member form a joint portion at least at the leading edge portion and the trailing edge portion of the blade, and at the joint portion, the first member and the second member are joined such that the innermost layer of the fiber-reinforced composite material layer is directly joined or joined via a connecting member, and the innermost layer of the fiber-reinforced composite material layer of the first member, the innermost layer of the fiber-reinforced composite material layer of the second member, and the connecting member satisfy the following Condition 1 and Condition 2. Condition 1: The innermost layer of the fiber-reinforced composite material layer of the first member, the innermost layer of the fiber-reinforced composite material layer of the second member, and the connecting member are composed of a fiber-reinforced composite material in which reinforcing fibers are uniaxially oriented. Condition 2: The uniaxially oriented reinforcing fibers included in the innermost layer of the fiber-reinforced composite material layer of the first member, the innermost layer of the fiber-reinforced composite material layer of the second member, and the connecting member are oriented in the range of -10 degrees to +10 degrees with respect to the root direction (blade length direction) from the tip of the propeller blade, and the orientation angle of the reinforcing fibers is within 5 degrees between adjacent innermost layers or connecting members.

2. The propeller blade according to claim 1, further comprising a third member including one or more layers of fiber-reinforced resin layers existing on the inner layer side so as to straddle the joint portion of the first member and the second member at the joint portion on the leading edge side of the blade, wherein the outermost layers on the first member and the second member sides of the third member are composed of a fiber-reinforced composite material in which reinforcing fibers are uniaxially oriented, and the orientation angle of the reinforcing fibers is within 5° with respect to both the reinforcing fibers included in the innermost layer of the first member and the reinforcing fibers included in the innermost layer of the second member.

3. The propeller blade according to claim 1, further comprising an external protective layer on the outer surface side of the joint portion on the leading edge side of the blade so as to straddle the joint portion.

4. The propeller blade according to claim 2, satisfying the following Condition 3 or Condition 4. Condition 3: At least one of the innermost layer of the first member, the innermost layer of the second member, and the reinforcing fibers included in the connecting member is such that the reinforcing fibers are intermittent with a fiber length of 10 to 100 mm at the joint portion and the portion forming the peripheral edge thereof. Condition 4: The reinforcing fibers included in the outermost layers on the first member and second member sides of the third member are intermittent with a fiber length of 10 to 100 mm in a range corresponding to the length of the joint portion from the separation point of the joint portion of the first member and the second member as a starting point.

5. Either both or one of the first member and the second member has a porous body or a hollow molded body inside at the joint portion on the leading edge side of the blade, and the surface shape of the porous body or the hollow molded body on the inner layer side of the blade has a convex shape. The propeller blade according to any one of claims 1 to 3.

6. The innermost layer of the fiber-reinforced resin layers included in the first member and the second member is not covered by a layer outside the innermost layer at the leading edge portion and the trailing edge portion of the blade. The propeller blade according to any one of claims 1 to 3.

7. Further comprising a porous core, wherein the porous core is included inside the first member and the second member. The propeller blade according to any one of claims 1 to 3.

8. A step of preparing a member including one or a plurality of layers of fiber-reinforced composite materials for forming the upper surface and the lower surface of the blade (Step 1), a step of shaping the member into the respective shapes of the upper surface and the lower surface of the propeller (Step 2), and a step of joining the member forming the upper surface of the propeller (the first member) and the member forming the lower surface of the propeller (the second member) obtained in Step 2 directly or via a connecting member (Step 3). A method for manufacturing a propeller blade, wherein in Step 2, the first member and the second member are shaped so as to be joinable at least at the leading edge portion and the trailing edge portion of the blade, and at the joint portion, the surfaces of the fiber-reinforced composite materials are shaped so as to face each other (the layer forming the facing side is referred to as the "innermost layer"), and the layer of the fiber-reinforced composite material of the innermost layer of the first member, the layer of the fiber-reinforced composite material of the innermost layer of the second member, and the connecting member are composed of a fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented, and in Step 2, the shaping is performed so as to satisfy the following Condition 2'. A method for manufacturing a propeller blade. Condition 2': The layers of the fiber-reinforced composite material of the innermost layer of the first member, the layers of the fiber-reinforced composite material of the innermost layer of the second member, and the uniaxially oriented reinforcing fibers included in the connecting member are oriented in the range of -10 degrees to +10 degrees with respect to the root direction (blade length direction) from the tip of the propeller blade, and the orientation angle is within 5 degrees between adjacent innermost layers or connecting members.

9. The method for manufacturing a propeller blade according to claim 8, wherein in step 3, pressure is applied to the joint by a molding method using a mold having the shape of the upper surface of the propeller blade and a mold having the shape of the lower surface of the propeller blade, and then the joint is made.

10. The method for manufacturing a propeller blade according to claim 8, wherein in step 3, a porous core member is disposed in the space formed by the first member and the second member, and the porous core member is joined to the first member and the second member.

11. The method for manufacturing a propeller blade according to claim 10, wherein the porous core member has a layer of a fiber-reinforced composite material in which reinforcing fibers are uniaxially oriented on the surface in contact with the first member and the second member so as to satisfy the following condition 5. Condition 5: The orientation angle is within 5 degrees between the reinforcing fibers included in the layer of the fiber-reinforced composite material of the innermost layer of the first member and the reinforcing fibers included in the layer of the fiber-reinforced composite material of the innermost layer of the second member.

12. The method for manufacturing a propeller blade according to claim 8, further comprising a shaping step of making the blade edge into a smooth curved surface with respect to the portion that becomes the blade edge after step 2 or step 3.

13. Furthermore, the method for manufacturing a propeller blade according to claim 8, further comprising a step (step 4) of further joining an external protective layer so as to straddle the joint on the outside of the propeller blade at the joint between the first member and the second member.

14. The method for manufacturing a propeller blade according to claim 8, wherein in a step before step 3, a base material in which cuts are made so that the fiber length of the uniaxially oriented reinforcing fibers is 10 to 100 mm is applied to the joint and the peripheral portion of the joint of the layer that becomes the innermost layer of the one or more layers of fiber-reinforced composite material, and at least one of the connecting members.

15. The method for manufacturing a propeller blade according to claim 8, further comprising an operation of enclosing a porous body or a hollow molded body having a convex shape on the surface shape on the inner layer side of the blade in a portion that should be a joining portion on the leading edge side of the wing of both or either one of the first member and the second member in Step 1 or Step 2.

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