Propeller blade, and method for manufacturing the same

Abstract

To provide a propeller blade which is advantageous for improvement of productivity, improvement of shaping property and dynamic characteristics of a propeller blade, and a method for manufacturing the same.SOLUTION: A propeller blade has a member that is shaped in a propeller shape and constitutes a contour of the propeller blade in which a plurality of fiber-reinforced composite material layers are stacked, wherein a notch penetrating into the two or more layers are applied to the plurality of fiber-reinforced composite material layers, and when the thicknesses of the plurality of fiber-reinforced composite material layers are 100%, the length in the stacking direction of the notch is a length in the stacking direction with the thickness of 40% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a propeller blade and a method for manufacturing the same.

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 the 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, the difficulty of its molding is high, and high-rate production 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 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 need for weight reduction, fiber-reinforced composite materials with high specific strength and high specific rigidity are applied to the propeller blades.

[0007] When manufacturing a propeller blade made of a fiber-reinforced composite material, if a prepreg in which a reinforcing fiber base material is impregnated with a resin is used in advance, fiber twisting during molding can be suppressed, and weight variation of the molded product can also be suppressed, enabling the production of high-quality propeller blades.

[0008] The molding process of a propeller blade using a prepreg is carried out in the order of cutting out the base material, shaping, and heating and pressurizing for curing. Among these processes, in particular, the process of deforming the prepreg into a propeller shape, that is, the shaping process, is a process with high difficulty in propeller blade molding and is likely to become a bottleneck in the production rate. That is, for a molded product in which the chordwise length, angle of attack, and curved surface shape of the airfoil continuously change in the spanwise direction, it is extremely difficult to arrange the prepreg made of continuous fibers without wrinkles. Since the size of the propeller blade is at most about several meters, in many cases, shaping is carried out manually, which takes a long time and causes variation in the work due to manual operation.

[0009] As a method for automating shaping, a shaping method by hot forming can be mentioned. Hot forming is a technique for controlling the hardness of the laminate and improving the formability by raising the temperature of the prepreg laminate to a desired temperature and lowering the resin viscosity.

[0010] By carrying out hot forming, it is possible to shape the prepreg laminate to a certain extent. However, for a molded product such as a propeller blade in which the chordwise length, angle of attack, and curved surface shape of the airfoil continuously change in the spanwise direction, it is extremely difficult to arrange the prepreg without wrinkles because the continuous fibers are taut.

[0011] As a method for improving the formability of a prepreg using continuous fibers, there is a means of locally inserting a cut into the prepreg sheet. For example, Patent Document 1 discloses a means of inserting a cut along the fiber direction of a fiber material without cutting the reinforcing fiber material of a unidirectionally oriented reinforcing fiber base material. In this method, while suppressing the influence of strength reduction due to the cut, the spreadability in the direction orthogonal to the fiber can be improved, but the influence of the tension of the continuous fiber still remains.

[0012] Further, Patent Document 2 discloses a method of improving formability by inserting a cut into the ridge line portion of a molded product, but the suitable location for inserting the cut is unclear in the case of a prepreg laminate constituting the skin of a propeller blade. Inserting a cut across a plurality of prepreg layers may cause a significant strength reduction.

[0013] Patent Document 3 discloses a method of inserting a cut so that the cut positions do not overlap in adjacent reinforcing fiber layers in the lamination direction, but controlling the cut insertion position for each layer requires a great deal of labor and hinders the improvement of productivity.

[0014] As described above, in the prior art, there has been no technology that satisfies all three elements of productivity improvement, formability improvement, and mechanical properties of a propeller blade. Therefore, the present invention provides a propeller blade that satisfies all of the above three elements.

Means for Solving the Problems

[0015] In order to solve such problems, the present invention employs the following means. [1] A propeller blade including a member that forms the outer shape of the propeller blade, in which a plurality of layers of fiber-reinforced composite material layers are laminated and shaped into a propeller shape, and the plurality of layers of fiber-reinforced composite material layers are provided with cuts penetrating two or more layers, and when the length of the cut in the lamination direction is 100% of the thickness of the plurality of layers of fiber-reinforced composite material layers, the length in the lamination direction is 40% or less. [2] The cut made in the plurality of fiber-reinforced composite material layers of the propeller blade according to [1] above forms an angle of 45° or less with respect to the blade length direction. [3] The cut made in the plurality of fiber-reinforced composite material layers is made at least at two locations, and fibers having a fiber length of 5 to 100 mm are present in the region sandwiched by the two cuts, in the propeller blade according to [1] or [2] above. [4] In the propeller blade according to any one of [1] to [3] above, the ratio of the maximum value to the minimum value of the blade circumference in the region from the blade root to 30% of the blade length is 1.2 or more, and the cut is provided in the region. [5] The propeller blade according to any one of [1] to [4] above, wherein the cut is not made in the outermost layer of the plurality of fiber-reinforced composite material layers. [6] A method for manufacturing a propeller blade, comprising: a step of preparing two or more sheet-shaped prepregs and laminating the sheet-shaped prepregs to obtain a laminated prepreg (step 1); performing step 1 two or more times to obtain a plurality of laminated prepregs, and adding a cut extending in a plurality of layers in the thickness direction from one surface side of at least one of the laminated prepregs (step 2); laminating the plurality of laminated prepregs so that the cut positions do not overlap in the laminated prepreg with the cut, and then performing a step of heating and curing after shaping into a propeller shape (step 3A). [7] A method for manufacturing a propeller blade, comprising: a step of preparing two or more sheet-shaped prepregs and laminating the sheet-shaped prepregs to obtain a laminated prepreg (step 1); performing step 1 two or more times to obtain a plurality of laminated prepregs, and adding a cut extending in a plurality of layers in the thickness direction from one surface side of at least one of the laminated prepregs (step 2); shaping and laminating the laminated prepreg into a propeller shape so that the cut positions do not overlap, and then performing a step of heating and curing (step 3B). [8] The method for manufacturing a propeller blade according to [6] or [7] above, wherein in step 3A or step 3B, before shaping into a propeller shape, the plurality of laminated prepregs or the laminate of laminated prepregs is preheated. [9] In step 3A or step 3B, the step of shaping into a propeller shape is a step of placing a laminated prepreg between a mold for providing the shape of the outer surface of the propeller blade skin and a mold for providing the shape of the inner surface, and sandwiching and pressing the laminated prepreg with the two molds to shape it into a propeller shape. And before pressing the laminated prepreg with the two molds, a part of the laminated prepreg is brought into contact only with the mold for providing the shape of the inner surface of the propeller blade skin, and then pressing is performed. The method for manufacturing a propeller blade according to any one of [6] to [8] above, characterized in that.

[10] The method for manufacturing a propeller blade according to any one of [6] to [9] above, wherein in the step 2, all or part of the laminated prepreg with a cut is such that the cut penetrates from the front surface to the back surface.

[11] The cut made in the laminated prepreg, when it is a propeller blade, the direction in which the cut extends forms an angle of 45° or less with respect to the blade length direction. The method for manufacturing a propeller blade according to [6] to

[10] above.

[12] In step 2, the cut made in the laminated prepreg is made at at least two or more locations, and in the region sandwiched by the two cuts, there are fibers having a fiber length of 5 to 100 mm. The method for manufacturing a propeller blade according to any one of [6] to

[11] above.

[13] The ratio of the maximum value to the minimum value of the blade circumference in the region from the blade root to 30% of the blade length of the propeller blade is 1.2 or more, and the cut is provided in the region. The method for manufacturing a propeller blade according to any one of [6] to

[12] above. [Effect of the Invention]

[0016] 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

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0018] Hereinafter, the present invention will be described with specific examples. In this specification, the following terms have the following meanings respectively.

[0019] "Shaping": It means deforming an object into a target shape. For example, the operation of placing a sheet-like prepreg along a mold is included in this.

[0020] The propeller blade according to the present invention is a propeller blade including a member that forms the outer shape of the propeller blade, in which a plurality of layers of fiber-reinforced composite material layers are laminated and shaped into a propeller shape, and the plurality of layers of fiber-reinforced composite material layers are provided with cuts penetrating two or more layers. When the length of the cut in the lamination direction is set to 100% of the thickness of the plurality of layers of fiber-reinforced composite material layers, the length in the lamination direction is 40% or less. Note that the length in the lamination direction is the length in the direction in which the thickness of the layer is obtained.

[0021] 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, when applying a fiber-reinforced composite material to a propeller blade in order 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 having the airfoil shape of the propeller blade. The propeller blade of the present invention has an airfoil-shaped skin, and the skin is formed by laminating a fiber-reinforced composite material in which reinforcing fibers are uniaxially or multi-axially oriented.

[0022] Examples of the reinforcing fibers include organic fibers such as aramid fibers, polyethylene fibers, poly(p-phenylene benzoxazole) (PBO) fibers, inorganic fibers such as glass fibers, carbon fibers, silicon carbide fibers, alumina fibers, chlano 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. Among them, in the present invention, carbon fibers are preferable. Among these reinforcing fibers, they are lightweight and have particularly excellent properties in terms of specific strength and specific modulus of elasticity, and are also excellent in heat resistance and chemical resistance. Furthermore, polyacrylonitrile (PAN)-based carbon fibers, which are easy to obtain high-strength carbon fibers, are more preferable.

[0023] The uniaxial orientation of reinforcing fibers means that the reinforcing fibers are oriented in a single direction, and for example, unidirectional prepregs and unidirectional fabric substrates correspond to this. Further, the multi-axial orientation of reinforcing fibers means that there are reinforcing fibers oriented in a plurality of directions within a single layer, and for example, a fabric-like fiber substrate 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 fiber orientation direction and when a tensile load is applied in a direction orthogonal to the fiber orientation direction, generally, when a tensile load is applied in the fiber orientation direction, both the strength and rigidity increase. On the other hand, various loads are applied to the propeller blade during operation. Therefore, generally, it is not the case that all of the reinforcing fibers constituting the skin of the propeller blade are oriented in the same direction, and the propeller blade may contain reinforcing fibers oriented in a plurality of directions. In the present invention, the orientation direction of the uniaxially or multi-axially oriented fiber-reinforced composite material is controlled for each layer to control the mechanical properties of the propeller blade skin.

[0024] Further, the reinforcing fibers used in the present invention are not particularly limited, and 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.

[0025] 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, phenolic resin, epoxy acrylate resin, urethane acrylate resin, phenoxy resin, alkyd resin, urethane resin, maleimide resin, cyanate resin, etc., and 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, polyether sulfone resin, polyketone (PK) resin, polyarylene ether ketone resin (PAEK), polyarylate (PAR) resin, polyether nitrile (PEN) resin, phenolic resin, phenoxy resin, fluororesin such as polytetrafluoroethylene resin, and furthermore, thermoplastic elastomers such as polystyrene resin, polyolefin resin, polyurethane resin, polyester resin, polyamide resin, polybutadiene resin, polyisoprene resin, fluororesin, etc., their 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., their copolymers, modified products, and resins blended with two or more of these may also be used.

[0026] The structure of the skin is not particularly limited. For example, it may have a structure divided into an upper skin having the airfoil shape on the upper side of the propeller blade and a lower skin having the airfoil shape on the lower side of the propeller blade, or it may have a shape in which a reinforcing fiber base material is wound in the circumferential direction in the chordwise cross section of the propeller blade. Further, a porous body or a honeycomb core may be provided in the skin, and a sandwich structure in which the outer periphery is covered with the skin may be adopted.

[0027] There is also no particular limitation on the structure on the inner layer side of the skin of the propeller blade of the present invention. For example, a porous body may be arranged and used as a core material, or a hollow structure may be adopted, and the skin may be connected in the thickness direction of the blade to support the skin, and a reinforcing structure such as a shear web extending in the blade length direction may be provided.

[0028] Further, the plurality of fiber-reinforced composite material layers used in the propeller blade of the present invention are characterized in that cuts are made through two or more layers. For example, in FIG. 1, six layers of fiber-reinforced composite material layers are laminated, and cuts are formed through two layers in the lamination direction in the second and third layers from the bottom. At this time, it is desirable that the reinforcing fibers are cut by the cuts in the layers where the cuts are formed, and it is desirable that the reinforcing fibers cut at this time are continuous fibers. By cutting the continuous fibers in this way, it is possible to suppress the tension of the continuous fibers even when there are changes in the circumferential length in the chordwise direction characteristic of the propeller blade structure and changes in the circumferential length between the inner layer and the outer layer of the skin, and the formability can be remarkably improved. At this time, there is no problem with the angle of the cuts and the orientation direction of the reinforcing fibers in each fiber-reinforced composite material layer. For example, the smaller the angle formed by the fiber orientation direction and the extension direction of the cuts, the more the strength reduction at the cut insertion portion can be suppressed. Further, the shape of the cuts is not particularly limited, and for example, a linear cut or a curved cut may be used.

[0029] Further, in the present invention, when the depth of the notch is 100% of the thickness of the plurality of fiber-reinforced composite material layers, it is characterized in that the notch has a length in the lamination direction of 40% or less. For example, in FIG. 2, eight layers of fiber-reinforced composite material layers having the same thickness in the lamination direction 202 are laminated. At this time, since the notch 203A is inserted through two layers, the length in the lamination direction in which the notch is formed is 25% of the thickness of the fiber-reinforced composite material at the notch portion. Also, since the notch 203B is inserted through three layers, the length in the lamination direction in which the notch is formed is 37.5% of the thickness of the fiber-reinforced composite material at the notch portion. Also. When the notches 203C and 203D are projected in the thickness direction, notches extending over two layers are formed at the same position. In this case, notches of four layers are inserted at the same position, and the length in the lamination direction of the notch at the notch portion is 50% of the thickness of the fiber-reinforced composite material. In addition, when the fiber-reinforced composite material layer has a sandwich structure and a porous body is included in addition to the fiber-reinforced composite material layer, the calculation is performed only based on the thickness of the fiber-reinforced composite material layer without considering the thickness of the porous body. It is preferable that the length in the lamination direction in which the notch is formed is 40% or less of the thickness of the fiber-reinforced composite material at the notch portion, because a decrease in mechanical properties can be suppressed. Also, if it is 5% or more, the number of notches to be inserted can be reduced, leading to an improvement in productivity, which is preferable.

[0030] Further, in the propeller blade of the present invention, it is preferable that the cut made in the plurality of fiber-reinforced composite material layers forms an angle of 45° or less with respect to the blade length direction. Here, the blade length direction of the propeller blade is the direction from the root of the propeller blade toward the blade tip. When projected onto a plane by a light ray perpendicular to the rotation plane of the propeller blade, it is the direction parallel to the long side of the rectangle (hereinafter sometimes referred to as the "circumscribed rectangle") that circumscribes the image of the propeller blade contour and has the minimum area. On the other hand, the chord direction is the direction parallel to the short side of the circumscribed rectangle. Also, the angle formed by the cut and the blade length direction is the angle formed by the straight line connecting the end points of the cut when looking at the cut in the depth direction of the cut and the blade length direction. Note that the cut may be made in a curved manner in its top view. For example, if the cut is linear when viewed from the lamination direction as shown in Fig. 3(a), the direction in which the cut extends is the same straight line direction, and if it is curved, it is like the broken line in Fig. 3(b). In the present invention, as shown in Fig. 4, it is preferable that the cut forms an angle of 45° or less with respect to the blade length direction. Generally, the main load applied to the propeller blade is the load in the blade length direction. By adopting such a configuration, it is possible to reduce the decrease in strength in the blade length direction. Also, the change in the perimeter in the chord direction, which is characteristic of the propeller blade structure, and the fact that the perimeters of the layer on the inner surface side and the layer on the outer surface side of the skin become unequal due to shaping cause problems in shaping. However, when the direction in which the cut extends is formed at an angle of 45° or less with respect to the blade length direction, it is easy to obtain high followability with respect to the deformation in the chord direction, which is also preferable from the viewpoint of formability.

[0031] In addition, in the propeller blade of the present invention, the cuts made in the plurality of layers of fiber-reinforced composite material layers are made at least at two locations, and fibers having a fiber length of 5 to 100 mm are present in the region sandwiched by the two cuts. It is characterized in that. Since there are two or more of the above-mentioned cuts and reinforcing fibers having a fiber length of 5 to 100 mm are present in the region, the elongation effect of the base material can be more easily obtained, and the decrease in the mechanical properties in the fiber orientation direction can be suppressed, which is preferable. It is desirable that all of the fibers present in the region are 5 to 100 mm. The "region sandwiched by two cuts" is a range surrounded by a straight line connecting both ends of adjacent cuts and the cuts.

[0032] In addition, in the propeller blade of the present invention, the ratio of the maximum value to the minimum value of the blade circumference in the region from the blade root to 30% of the blade length is 1.2 or more, and the above-mentioned cut is provided in the region. It is characterized by.

[0033] The region from the blade root to 30% of the blade length is a plane passing through the rotation center of the propeller blade, parallel to the short side of the circumscribed rectangle, and perpendicular to the rotation plane. It corresponds to the portion included in the region up to 30% of the length to the short side of the rectangle on the side far from the rotation center in the long side direction of the circumscribed rectangle. When the short sides of the rectangles exist at an equal distance from the rotation center, it corresponds to the portion included in the region up to 30% of the length to each short side of the rectangle. In addition, the blade circumference is the outer peripheral length of a cross section perpendicular to the rotation plane obtained by cutting the propeller blade parallel to the short side of the circumscribed rectangle.

[0034] In particular, in the present invention, in the region from the blade root to 30% of the blade length, in a propeller blade in which the ratio of the maximum value to the minimum value of the blade circumference is 1.2 or more, the improvement in formability is remarkable.

[0035] In addition, in the propeller blade of the present invention, it is preferable that the above-mentioned cut is not made in the outermost layer of the fiber-reinforced composite material. By not providing the cut in the outermost layer of the fiber-reinforced composite material, it is possible to suppress a decrease in strength particularly against foreign object collision.

[0036] In the method for manufacturing a propeller blade of the present invention, a step of preparing two or more sheet-like prepregs and laminating the sheet-like prepregs to obtain a laminated prepreg (Step 1), Step 1 is carried out two or more times to obtain a plurality of laminated prepregs, and among them, a step of making cuts extending in a plurality of layers in the thickness direction from one surface side of at least one of the laminated prepregs (Step 2), in the case of the laminated prepreg with cuts, the plurality of laminated prepregs are laminated so that the cut positions do not overlap, and then, after shaping into a propeller shape, a step of heating and curing (Step 3A) is included, or, a step of preparing two or more sheet-like prepregs and laminating the sheet-like prepregs to obtain a laminated prepreg (Step 1), Step 1 is carried out two or more times to obtain a plurality of laminated prepregs, and among them, a step of making cuts extending in a plurality of layers in the thickness direction from one surface side of at least one of the laminated prepregs (Step 2), in the case of the laminated prepreg with cuts, the laminated prepregs are shaped and laminated into a propeller shape so that the cut positions do not overlap, and then, a step of heating and curing (Step 3B) is included. Further, the applied cuts have a length that is 40% or less of the length in the lamination direction when the thickness of the fiber-reinforced composite material layer included in the propeller blade after shaping is set to 100%.

[0037] When the skin of a 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 fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented or multi-axially oriented can be obtained. Particularly when applying a prepreg made of continuous fibers, high mechanical properties can be obtained and it is suitable. On the other hand, since the skin has a complex wing shape as described above, there is a problem in the formability into a wing shape due to the uniaxially or multi-axially oriented reinforcing fibers stretching. Particularly when trying to automate the shaping, it becomes even more difficult to solve this problem.

[0038] Therefore, in the method for manufacturing a propeller blade of the present invention, two or more sheet-like prepregs are prepared, and the sheet-like prepregs are laminated to obtain a laminated prepreg. When laminating the prepregs, the prepreg sheets can be laminated on a flat workbench so as to have a designed lamination angle and lamination order to obtain a desired lamination structure. Also, at the time of lamination, a sheet-like prepreg previously cut into the skin shape of the propeller blade may be laminated. In the present invention, at least two or more laminated prepregs are obtained in this way.

[0039] Subsequently, in the method for manufacturing a propeller blade of the present invention, a plurality of cuts are made from one surface side of at least one laminated prepreg in the thickness direction over a plurality of layers. The method of inserting cuts over a plurality of layers is not particularly limited, but a knife-like cutting tool may be used to insert the cuts once, or the cuts may be inserted a plurality of times at the same location. Also, cuts may be inserted at specified locations using something like a Thomson blade. The depth of the cuts may extend across all the layers of the prepreg laminate, or may be limited to some of the layers.

[0040] Also, in the method for manufacturing a propeller blade of the present invention, in the above step 2, it is preferable that all or part of the laminated prepreg with cuts is such that the cuts penetrate from the front surface to the back surface. Inserting cuts across all the layers of the laminated prepreg selected in this way is suitable because the cut depth can be reliably controlled.

[0041] Also, in the method for manufacturing a propeller blade of the present invention, the cuts made in the laminated prepreg are preferably such that, when formed into a propeller blade, the direction in which the cuts extend forms an angle of 45° or less with respect to the blade length direction. By adopting such a configuration, a reduction in the strength in the blade length direction can be achieved. Also, although the change in the perimeter in the chord direction characteristic of the propeller blade structure and the change in the perimeter between the inner layer and the outer layer of the skin cause problems in shaping, when the extension direction of the cuts is formed at an angle of 45° or less with respect to the blade length direction, an elongation effect in the chord direction is easily obtained, which is also preferable from the viewpoint of formability.

[0042] Further, in the method for manufacturing a propeller blade of the present invention, in step 2, the cuts applied to the laminated prepreg are applied at at least two locations, and fibers having a fiber length of 5 to 100 mm are present in the region sandwiched by the two cuts. When there are two or more of the above cuts and the reinforcing fibers are cut at at least two locations and both ends of the reinforcing fibers become cuts, it is preferable that the fiber length is 5 to 100 mm, so that the decrease in the mechanical properties in the fiber orientation direction can be suppressed without impairing the formability.

[0043] Subsequently, in the method for manufacturing a propeller blade of the present invention, in the case of the laminated prepreg with cuts, the plurality of laminated prepregs are laminated so that the cut positions do not overlap, and then, after shaping into a propeller shape, heating and curing are performed, or in the case of the laminated prepreg with cuts, after shaping and laminating into a propeller shape so that the cut positions do not overlap, heating and curing are performed.

[0044] In this step, the laminated prepregs are laminated according to the design. The order of lamination may be any order. Also, in addition to the prepregs, single-layer prepreg sheets, foamed sheets, etc. may be included in the lamination, and these layers may exist between the laminated prepregs.

[0045] When laminating the laminated prepregs with cuts, by laminating them so that the cut positions do not overlap, it is possible to avoid the strength of the propeller blade from decreasing continuously in the depth direction unexpectedly.

[0046] The lamination of the laminated prepregs may be performed on a flat workbench and then shaped into a propeller shape, or may be laminated while being shaped into a propeller shape. In the former case, it is preferable because it is easy to finely control the mutual positional relationship of the laminate. Also, in the latter case, the thickness of the prepreg laminate to be laminated at one time can be reduced, so the formability is improved, which is preferable.

[0047] In the method for manufacturing a propeller blade of the present invention, in step 3A or step 3B, the step of shaping into a propeller shape is a step of placing a laminated prepreg between a mold for providing the shape of the outer surface of the propeller blade skin and a mold for providing the shape of the inner surface, and sandwiching and press-bonding the laminated prepreg with the two molds to shape it into a propeller shape. Further, before press-bonding the laminated prepreg with the two molds, it is preferable that only a part of the laminated prepreg is brought into contact with the mold for providing the shape of the inner surface of the propeller blade, and then press-bonding is performed.

[0048] The propeller blade forming mold is a mold that forms the blade shape of the propeller blade when the prepreg is heat-cured in the subsequent process. The propeller blade forming mold can also be used as a mold for providing the shape of the outer surface of the propeller blade skin. Further, the propeller blade core material is a member located in the inner layer of the skin and can be, for example, a porous body that becomes a part of the final molded product, or a member for forming a hollow portion inside the propeller blade after removing the heat-cured prepreg. The propeller blade core material can also be used as a mold for providing the shape of the inner surface of the propeller blade skin. Further, the preform mold is a mold used to shape the prepreg into a propeller shape.

[0049] The propeller shape is a preform roughly shaped into the shape of the final molded product. For example, from the viewpoint of suppressing the prepreg biting into the mold, it does not have to be exactly the same as the member shape of the final molded product. By press-bonding and shaping the laminated prepreg prepared as described above, the laminate of the laminated prepreg, and other molding materials to the mold, shaping can be successfully completed without fiber tension or the like.

[0050] At the time of press fitting, it is preferable to perform shaping by first bringing the base material into contact with the inner surface side of the skin of the cavity between the mold that gives the shape of the outer surface of the propeller blade skin and the mold that gives the shape of the inner surface, and then press fitting. When applying a shaping force, sandwiching and pressing the laminated prepreg with such a mold structure can apply a high shaping force, which is suitable. Further, when sandwiching and pressing the laminated prepreg or the laminate of the laminated prepregs with a mold, if the base material is first pressed against the convex surface side of the cavity, that is, the inner layer side of the propeller blade, the base material on the inner layer side of the propeller blade is fixed. As a result, the base material on the outer layer side is stretched, and the stretching effect of the laminated prepreg of the present invention can be easily obtained, and shaping can be performed without wrinkles. Further, when tension is applied to the laminated prepreg during shaping, it becomes easier to perform shaping without wrinkles. In particular, when tension is applied in the chord direction, the influence of the change in the perimeter in the chord direction characteristic of the propeller blade structure and the change in the perimeter between the inner and outer layers of the skin can be suppressed, and shaping can be performed without wrinkles.

[0051] Further, in the method for manufacturing a propeller blade of the present invention, in step 3A or step 3B, it is preferable to preheat the plurality of laminated prepregs or the laminate of the laminated prepregs before or after laminating the plurality of laminated prepregs and before shaping into the propeller shape. By preheating the laminated prepreg, the resin softens and the effect of the cut is easily obtained, and the formability is improved.

[0052] Subsequently, in the present invention, the propeller shape thus obtained is characterized by heating and curing the preform. Heating and curing is performed by placing the three-dimensional preform in a heating and curing mold in order to form the blade shape of the propeller blade.

[0053] Further, the method for manufacturing a propeller blade of the present invention is particularly suitable when the shaping process is automated.

[0054] In the method for manufacturing a propeller blade of the present invention, it can be suitably applied when the ratio of the maximum value to the minimum value of the blade circumference in the region from the blade root to 30% of the blade length is 1.2 or more, and when the above-mentioned cut is provided in this region. In particular, the present invention is directed to a propeller blade in which the blade circumference length changes greatly at the blade root portion such that the ratio of the maximum value to the minimum value of the blade circumference length when cutting in the chord direction is 1.2 or more in the region from the blade root to 30% of the blade length. By providing the above-mentioned cut within the region from the blade root to 30% of the blade length, it is possible to improve the formability while maintaining the strength of the propeller blade.

Example

[0055] 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 description of the terms of such examples. In the following description, the orientation direction of the reinforcing fibers will be described with the wing length direction (wing root → wing tip) as 0° and the chord direction (wing leading edge → wing trailing edge) as 90°.

[0056] (Example 1) A propeller blade with a blade length of 1 m was manufactured by the following method.

[0057] P707AG-15 carbon fiber unidirectional prepreg manufactured by Toray Composite Materials America, Inc. was prepared and cut to fit the shape of the upper skin of the propeller blade. By cutting, a prepreg (prepreg 1) with carbon fiber orientation in the 0° direction and a prepreg (prepreg 2) with carbon fiber orientation in the 90° direction were obtained.

[0058] Subsequently, F6273C-07M carbon fiber fabric prepreg manufactured by Toray Composite Materials America, Inc., in which a cross-woven carbon fiber fabric was impregnated with resin, was prepared and cut to fit the shape of the upper skin of the propeller blade. By cutting, a prepreg (prepreg 3) with orthogonal carbon fibers oriented in the -45° direction and +45° direction respectively was obtained.

[0059] A prepreg laminate was obtained using the above prepreg. At this time, as laminates corresponding to the region from the wing root to 30% of the wing length, a prepreg laminate A laminated with [Prepreg 1 / Prepreg 1 / Prepreg 2 / Prepreg 3] and a prepreg laminate B laminated with [Prepreg 1 / Prepreg 1 / Prepreg 1 / Prepreg 2] were obtained. These laminates have a ply drop at a position intermediate between the wing root and the wing tip, and the lamination structure at the wing tip is [Prepreg 1 / Prepreg 2 / Prepreg 3] for prepreg laminate A and [Prepreg 1 / Prepreg 2] for prepreg laminate B.

[0060] Next, for the region corresponding to 10% to 30% of the wing length as viewed from the wing root of the obtained prepreg laminate A and prepreg laminate B, six cuts with a length of 8 cm were made in the 15° direction as shown in Fig. 5 to cut the fibers in the laminated prepreg. Specifically, three sets of cuts, each set consisting of two cuts existing at positions parallelly translated in the chord direction, were inserted from the wing root to the wing tip, and the length between each set of cuts was 50 mm. All carbon fibers oriented in the 90° direction existing in the region of 10% to 30% of the wing length were made discontinuous. Also, for prepreg laminate B, a prepreg laminate B1 was obtained by shifting the cut insertion position 10 mm forward in the chord direction from the cut insertion position of prepreg laminate A, and a prepreg laminate B2 was obtained by shifting the cut insertion position 20 mm forward in the chord direction from the cut insertion position of prepreg laminate A, so that cuts were not inserted at the same positions in each prepreg laminate.

[0061] The prepreg laminate A with cuts inserted, prepreg laminate B1, and prepreg laminate B2 were preheated, and while applying tension in the chordwise direction, they were pressed against a preform mold having the shape of the inner layer side surface of the propeller blade skin in the order of prepreg laminate A, prepreg laminate B1, and prepreg laminate B2 to be shaped. Then, prepreg 3 was further pressed against it to be shaped. For reference, the lamination structure in the region from the blade root to 30% of the blade length in this example is [prepreg 3 / prepreg 1 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 3] in the direction toward the surface of the mold.

[0062] In the same manner as the upper skin, for the lower skin, shaping was performed using a laminated prepreg on a preform mold having the shape of the inner layer side surface of the propeller blade skin. The lamination structure is the same as that of the upper skin, and the locations where cuts were inserted were provided at positions overlapping the cuts inserted in the upper skin when viewed perpendicular to the rotation plane for each of the prepreg laminate A, prepreg laminate B1, and prepreg laminate B2.

[0063] Thereafter, Rohacell (registered trademark) 110 IG - F, a polymethacrylimide rigid foam manufactured by Polyplastics Co., Ltd., was machined into the core shape of the propeller blade to obtain a porous core. With respect to the obtained porous core, the prepreg shaped into the upper skin shape removed from the preform mold and the prepreg shaped into the lower skin shape were overlapped according to the porous core shape, and then this was placed in a propeller blade molding die. After clamping the die, heat - curing molding was carried out in an oven.

[0064] In the obtained propeller blade, the thickness of a single layer of the unidirectional carbon fiber prepreg was 0.152 mm, and the thickness of a single layer of the carbon fiber fabric prepreg was 0.218 mm. Therefore, the propeller blade skin thickness was 2.108 mm. The laminated direction length of the cut inserted into the prepreg laminate A was 0.674 mm, and the ratio of the laminated direction length of the cut to the propeller blade skin thickness was 32%. The laminated direction lengths of the cuts inserted into the prepreg laminate B1 and the prepreg laminate B2 were 0.608 mm, and the ratios of the laminated direction lengths of the cuts to the propeller blade skin thickness were 29%.

[0065] It was visually confirmed that the surface of the obtained molded product was smooth. Also, after polishing the cross-section of the molded product until the fiber-reinforced composite material layer could be confirmed and then confirming with a microscope, it was confirmed that there were no disturbances in the layer structure or voids due to wrinkles.

[0066] (Example 2) In the same manner as in Example 1, a prepreg laminate A with a cut inserted, a prepreg laminate B1, and a prepreg laminate B2 were obtained, laminated in the order of prepreg laminate A / prepreg laminate B1 / prepreg laminate B2 on a flat workbench, and this laminate was preheated and pressed against a preform mold having the shape of the inner layer side surface of the propeller blade skin while applying tension in the chord direction to shape it. Then, the prepreg 3 used in Example 1 was pressed against it to shape it. For reference, the lamination structure in the region from the blade root to 30% of the blade length in this example is [prepreg 3 / prepreg 1 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 3] in the direction toward the surface of the mold.

[0067] In the same manner as the upper skin, for the lower skin, shaping was performed using a prepreg on a preform mold having the shape of the inner layer side surface of the propeller blade skin. The lamination structure is the same as that of the upper skin, and the cuts were inserted at positions overlapping the cuts inserted into the upper skin when viewed perpendicular to the rotation plane for each of the prepreg laminate A, prepreg laminate B1, and prepreg laminate B2.

[0068] In the same manner as in Example 1, a porous core was obtained, and the prepreg shaped into the upper skin shape and the prepreg shaped into the lower skin shape in the same manner as in Example 1 were overlapped to match the porous core shape. Then, this was placed in a propeller blade molding die, and after clamping the die, heat-curing molding was performed in an oven.

[0069] In the obtained propeller blade, the thickness of a single layer of the carbon fiber unidirectional prepreg was 0.152 mm, and the thickness of a single layer of the carbon fiber woven fabric prepreg was 0.218 mm. Therefore, the propeller blade skin thickness was 2.108 mm. The laminated direction length of the cut inserted into the prepreg laminate A was 0.674 mm, and the ratio of the laminated direction length of the cut to the propeller blade skin thickness was 32%. The laminated direction lengths of the cuts inserted into the prepreg laminate B1 and prepreg laminate B2 were 0.608 mm, and the ratio of the laminated direction length of the cut to the propeller blade skin thickness was 29%.

[0070] It was visually confirmed that the surface of the obtained molded product was smooth. Also, after polishing the cross-section of the molded product until the fiber-reinforced composite material layer could be confirmed and then checking with a microscope, it was confirmed that there was no disturbance in the layer structure or voids due to wrinkles.

[0071] (Example 3) In the same manner as in Example 1, a cut-inserted prepreg laminate A, prepreg laminates B1 and B2 were obtained. The prepreg laminate A / prepreg laminate B1 / prepreg laminate B2 were laminated in this order on a flat workbench, and this laminate was preheated. Next, a preform mold for giving the shape of the inner surface of the propeller blade skin and a preform mold for giving the shape of the outer surface of the propeller blade skin were prepared, and the preheated laminate was pressed against the preform mold for giving the shape of the inner surface while applying tension in the chord direction to form a part. Thereafter, the prepreg partially formed on the preform mold for giving the shape of the inner surface was sandwiched between the preform mold for giving the shape of the outer surface, pressed to complete the shaping, the mold was released, and further the prepreg 3 used in Example 1 was pressed against the prepreg B2 side and laminated while being shaped. For reference, the lamination structure in the region from the blade root to 30% of the blade length in this example is [prepreg 1 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 3] in the direction toward the surface of the mold.

[0072] In the same manner as for the upper skin, for the lower skin as well, shaping was performed using a laminated prepreg with a preform mold for giving the shape of the inner surface of the propeller blade skin and a preform mold for giving the shape of the outer surface of the paired propeller blade.

[0073] Thereafter, with respect to the porous core obtained in the same manner as in Example 1, the prepreg shaped into the upper skin shape and the prepreg shaped into the lower skin shape were overlapped according to the porous core shape, and then this was placed in a propeller blade forming mold, and after clamping, heat curing molding was performed in an oven to obtain a propeller blade.

[0074] It was visually confirmed that the surface of the obtained molded product was smooth. Also, after polishing the cross-section of the molded product until the fiber-reinforced composite material layer could be confirmed and then checking with a microscope, it was confirmed that there was no disturbance in the layer structure due to wrinkles or voids.

[0075] (Comparative Example 1) A propeller blade was molded in the same manner as in Example 1, except that no cut was made in the prepreg laminate.

[0076] When shaping the prepreg laminate, a large force was required as compared with Examples 1 to 3, and some shaping was defective, resulting in wrinkles.

[0077] It was visually confirmed that the surface of the molded product was smooth. However, after polishing the cross-section of the molded product until the fiber-reinforced composite material layer could be confirmed and then observing with a microscope, it was confirmed that the layer structure was disturbed due to wrinkles, and furthermore, it was confirmed that voids existed at that location. It is obvious that the reliability of the molded product is inferior to that of the molded products of the examples due to the disturbance of the layer structure and the existence of voids.

Industrial Applicability

[0078] The propeller blade according to the present invention is a propeller blade with excellent productivity and high strength, and can be suitably used for propellers such as UAM and drones.

Explanation of Symbols

[0079] 101, 201: Fiber-reinforced composite material layer 102, 202: Laminating direction 103, 203A, 203B, 203C, 203D, 404, 504: Cut 401: Propeller blade 402, 501: Rotation center of propeller blade 403: Rectangle circumscribing the propeller blade 502: Position 10% of the wing length from the wing root 503: Position 30% of the wing length from the wing root

Claims

1. A propeller blade including a member that is formed into a propeller shape by laminating a plurality of layers of fiber-reinforced composite material layers to form the outer shape of the propeller blade, wherein the plurality of layers of fiber-reinforced composite material layers are provided with cuts penetrating two or more layers, and when the thickness of the plurality of layers of fiber-reinforced composite material layers is taken as 100%, the length of the cuts in the lamination direction is 40% or less in the lamination direction length.

2. The propeller blade according to Claim 1, wherein the cuts provided in the plurality of layers of fiber-reinforced composite material layers form an angle of 45° or less with respect to the blade length direction.

3. The propeller blade according to Claim 1 or 2, wherein the cuts provided in the plurality of layers of fiber-reinforced composite material layers are provided at least at two locations, and fibers having a fiber length of 5 to 100 mm exist in the region sandwiched by the two cuts.

4. The propeller blade according to Claim 1 or 2, wherein the ratio of the maximum value to the minimum value of the blade circumference in the region from the blade root to 30% of the blade length is 1.2 or more, and a cut is provided in this region.

5. The propeller blade according to Claim 1 or 2, wherein the cuts are not provided in the outermost layer of the plurality of layers of fiber-reinforced composite material layers.

6. A method for manufacturing a propeller blade, comprising: preparing two or more sheet-shaped prepregs and laminating the sheet-shaped prepregs to obtain a laminated prepreg (Step 1); performing Step 1 two or more times to obtain a plurality of laminated prepregs, and adding cuts extending through a plurality of layers in the thickness direction from one surface side of at least one of the laminated prepregs (Step 2); laminating the plurality of laminated prepregs so that the cut positions do not overlap, and then shaping into a propeller shape and performing heating and curing (Step 3A).

7. A method for manufacturing a propeller blade, comprising: preparing two or more sheet-like prepregs, and laminating the sheet-like prepregs to obtain a laminated prepreg (step 1); performing step 1 two or more times to obtain a plurality of laminated prepregs, and among them, adding cuts extending in the thickness direction over a plurality of layers from one surface side of at least one laminated prepreg (step 2); shaping and laminating the laminated prepregs into a propeller shape so that the cut positions do not overlap, and then performing heating and curing (step 3B).

8. The method for manufacturing a propeller blade according to claim 6 or 7, wherein in step 3A or step 3B, the plurality of laminated prepregs or the laminate of the laminated prepregs is preheated before being shaped into a propeller shape.

9. The method for manufacturing a propeller blade according to claim 6 or 7, wherein in step 3A or step 3B, the step of shaping into a propeller shape is a step of placing the laminated prepreg between a mold for giving the shape of the outer surface of the propeller blade skin and a mold for giving the shape of the inner surface, and sandwiching and press-bonding the laminated prepreg with the two molds to shape it into a propeller shape, and before press-bonding the laminated prepreg with the two molds, a part of the laminated prepreg is brought into contact only with the mold for giving the shape of the inner surface of the propeller blade skin, and then press-bonding is performed.

10. The method for manufacturing a propeller blade according to claim 6 or 7, wherein in step 2, all or part of the laminated prepreg with cuts is such that the cuts penetrate from the front surface to the back surface.

11. The method for manufacturing a propeller blade according to claim 6 or 7, wherein the cuts made in the laminated prepreg, when formed into a propeller blade, form an angle of 45° or less with respect to the blade length direction in the direction in which the cuts extend.

12. The method for manufacturing a propeller blade according to claim 6 or 7, wherein in step 2, the cuts made in the laminated prepreg are made at at least two or more locations, and fibers having a fiber length of 5 to 100 mm are present in the region sandwiched by the two cuts.

13. The method for manufacturing a propeller blade according to claim 6 or 7, wherein for the propeller blade, the ratio of the maximum value to the minimum value of the blade circumference in the region from the blade root to 30% of the blade length is 1.2 or more, and cuts are provided in this region.

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