Propeller blade, and method for manufacturing the same

Abstract

To provide a propeller blade which can achieve both productivity and high strength reliability.SOLUTION: A propeller blade has a member shaped in a propeller shape in which fiber-reinforced composite materials where reinforcement fibers are uniaxially or multiaxially oriented are stacked, wherein the member has at least one layer of the fiber-reinforced composite materials in which the reinforcement fibers are uniaxially oriented, and in a layer in which the reinforcement fibers are oriented at an angle of 60° or more with respect to a bottom direction (wing length direction) from a wing end of the propeller blade, among the layers of the fiber-reinforced composite materials in which the reinforcement fibers are uniaxially oriented, a sheet-like prepreg as a raw material is molded by applying a notch thereto, and in at least the bottom part of the propeller blade, the reinforcement fibers are disconnected at a fiber length of 10 to 100 mm.SELECTED DRAWING: None

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 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 weight reduction need, 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 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 the propeller blade using the prepreg is carried out in the order of cutting out the base material, shaping, and heating and pressurizing for curing. Among these processes, especially the shaping process is a process with high difficulty in propeller blade molding and is likely to become a bottleneck in the production rate. For a molded product in which the chord length, angle of attack, and curved surface shape of the airfoil of the propeller blade continuously change in the wing length 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, manual shaping is carried out. When carrying out the shaping work manually, it takes a long time and there are variations in the work due to manual operation.

[0009] Against this background, there is a high need for automating the shaping process. As a method for automating shaping, an automatic shaping method by hot forming can be mentioned. In hot forming, the temperature of the prepreg laminate is raised to a desired temperature, and the hardness of the laminate is controlled by lowering the resin viscosity to improve formability, and shaping is automatically carried out.

[0010] By performing hot forming, it is possible to shape the prepreg laminate to a certain extent. However, for molded products such as propeller blades where the chord length, angle of attack, and curved surface shape of the airfoil continuously change in the span direction, since continuous fibers are stretched, it is extremely difficult to arrange the prepreg without wrinkles.

[0011] In Patent Document 1, a prepreg base material laminate formed by laminating a plurality of prepreg base materials with finite-length cuts and continuous carbon fibers without cuts as reinforcing fibers, and a prepreg base material disposed on at least one side of the outermost layer of the prepreg base material laminate are used. Although molding using such a prepreg base material laminate is shown, sufficient strength reliability cannot be obtained for propeller blades that require high strength reliability to ensure bird strike resistance.

[0012] In addition, as shown in Patent Document 2, a molding material using a unidirectional carbon fiber sheet and randomly oriented short fiber bundles is shown. However, in the case of a randomly oriented material, fibers are likely to be oriented in the out-of-plane direction, and it is inferior to a continuous fiber material in terms of strength and rigidity. Similarly to Patent Document 1, sufficient strength reliability cannot be obtained for propeller blades that require high strength reliability to ensure bird strike resistance.

[0013] In Patent Document 3, an example is shown in which, when molding a flat lightweight member such as a propeller blade, reinforcing fibers are raised from a prepreg (cut prepreg) having a cut in the skin of the propeller blade to improve the adhesive strength with the core layer. Although the adhesive strength between the skin and the core layer is improved, similarly to Patent Document 1, sufficient strength reliability cannot be obtained for propeller blades that require high strength reliability to ensure bird strike resistance.

[0014] As described above, in the prior art, means for improving formability using cut prepregs and short fiber reinforced materials have been shown, but no method for achieving both strength reliability has been shown, and the compatibility between high build rate and strength reliability has not been achieved.

[0015] Therefore, an object of the present invention is to provide a propeller blade capable of achieving both productivity and high strength reliability.

Means for Solving the Problems

[0016] In order to solve such problems, the present invention provides the following means. [1] A propeller blade having a member formed into a propeller shape by laminating a fiber-reinforced composite material in which reinforcing fibers are uniaxially or multi-axially oriented, the member having at least one layer of a fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented, and among the layers of the fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented, for the layer in which the reinforcing fibers are oriented at an angle of 60° or more with respect to the root direction (blade length direction) from the tip of the propeller blade, at least in the root portion of the propeller blade, the reinforcing fibers are interrupted with a fiber length of 10 to 100 mm. A propeller blade characterized by this. [2] The propeller blade according to [1] above, wherein in the region within 30% of the blade length from the blade root, the ratio of the maximum value to the minimum value of the outer periphery of the vertical cross-section is 1.2 or more. [3] A method for manufacturing a propeller blade, comprising a step of laminating a plurality of sheet-like prepregs in which reinforcing fibers are uniaxially or multi-axially oriented to obtain a laminated prepreg (first step), a step of shaping the laminated prepreg into a propeller shape (second step), and a step of heat-curing the laminated prepreg in a propeller blade molding die (third step). In the sheet-like prepreg in which the reinforcing fibers are uniaxially oriented, in the prepreg containing reinforcing fibers oriented at an angle of 60° or more with respect to the root direction (blade length direction) from the tip of the propeller blade, at least in the portion corresponding to the root of the propeller blade, the reinforcing fibers contained in the prepreg are interrupted with a fiber length of 10 to 100 mm. A method for manufacturing a propeller blade characterized by this. [4] The method for manufacturing a propeller blade according to [3] above, wherein in the second step, pressure is applied to the surface of the laminated prepreg while applying tension to the laminated prepreg to shape the shape of the outer layer side surface or the inner layer side surface of the propeller blade skin. [5] In the second step, the laminated prepreg is preheated and shaped into a propeller shape, and the method for manufacturing a propeller blade according to [3] or [4] above is characterized by this. [6] The second step is a step of disposing the laminated prepreg between a mold having the shape of the outer layer side surface of the propeller blade skin and a mold having the shape of the inner layer side 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 having the shape of the inner layer side surface, and then press-bonding is performed. The method for manufacturing a propeller blade according to any one of [3] to [5] above is characterized by this. [Effect 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 Explanation of the Drawings]

[0018]

Figure 1

[0019] The propeller blade according to the present invention is a propeller blade having a member in which fiber-reinforced composite materials in which reinforcing fibers are uniaxially oriented or multi-axially oriented are laminated and shaped into a propeller shape. The member has at least one layer of a fiber-reinforced composite material in which reinforcing fibers are uniaxially oriented, and among the layers of the fiber-reinforced composite material in which reinforcing fibers are uniaxially oriented, for the layer in which the reinforcing fibers are oriented at an angle of 60° or more with respect to the root direction (blade length direction) from the tip of the propeller blade, at least at the root portion of the propeller blade, the reinforcing fibers are intermittent with a fiber length of 10 to 100 mm. It is characterized by this.

[0020] 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 to obtain a lightweight, high-rigidity, and high-strength propeller blade, a mode in which the outer shape is molded with a fiber-reinforced composite material and a member for supporting the fiber-reinforced composite material forming the outer shape is disposed inside is preferably adopted. Here, examples of the member for supporting the shape of the propeller blade include a solid mode such as a foam and a mode in which the fiber-reinforced composite material is partially reinforced from the inside like a rib. The propeller blade of the present invention has an outer shape of the propeller blade formed of a fiber-reinforced composite material (hereinafter, a member of the fiber-reinforced composite material shaped into a propeller shape may be conveniently referred to as a "skin"). And the skin is formed by laminating a fiber-reinforced composite material in which reinforcing fibers are uniaxially oriented or multi-axially oriented.

[0021] Examples of the reinforcing fibers used for the skin include organic fibers such as aramid fibers, polyethylene fibers, poly(paraphenylene benzoxazole) (PBO) fibers, inorganic fibers such as glass fibers, carbon fibers, silicon carbide fibers, alumina fibers, tyrano fibers, basalt fibers, ceramic fibers, metal fibers such as stainless steel fibers and steel fibers, boron fibers, natural fibers, and modified natural fibers. Among them, in the present invention, it is preferable to use carbon fibers. Carbon fibers are lightweight among these reinforcing fibers, 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, PAN-based carbon fibers, which are more likely to obtain high-strength carbon fibers, are more preferable.

[0022] When the reinforcing fibers are uniaxially oriented, it means that the reinforcing fibers are oriented in a single direction. For example, unidirectional prepregs and uniaxial fabric substrates correspond to this. Also, when the reinforcing fibers are multi-axially oriented, it means that there are reinforcing fibers oriented in multiple directions within a single layer. 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, not all of the reinforcing fibers constituting the skin of the propeller blade are oriented in the same direction, and the propeller blade contains reinforcing fibers oriented in multiple directions. In the present invention, the orientation direction of the uniaxially or multi-axially oriented fiber-reinforced composite material can be controlled for each layer, and the mechanical properties of the propeller blade skin can be controlled.

[0023] In addition, the fiber-reinforced composite material in the present invention is a material in which the above-mentioned 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, 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, 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, polystyrene resin, polyolefin resin, polyurethane resin, polyester resin, polyamide resin, polybutadiene resin, polyisoprene resin, fluororesin, etc., or copolymers and modified products thereof may also be used, or mixtures thereof may also be used. Further, examples of the polyarylene ether ketone resin (PAEK) include polyether ketone (PEK), polyether ether ketone (PEEK), polyether ether ketone ketone (PEEKK), polyether ketone ketone (PEKK), polyether ketone ether ketone ketone (PEKEKK), polyether ether ketone ether ketone (PEEKEK), polyether ether ether ketone (PEEEK), and polyether diphenyl ether ketone (PEDEK).

[0024] The form of the skin is not particularly limited. For example, it may have a structure divided into an upper skin having the upper blade shape on the propeller blade and a lower skin having the lower blade shape on the propeller blade, or it may be in a form where a laminated reinforced fiber composite material is spirally wound to form a propeller shape. Also, a porous body, a honeycomb core, etc. may be provided inside the skin, and a sandwich structure may be adopted.

[0025] The structure inside the skin of the propeller blade of the present invention is not particularly limited. As described above, for example, a porous body may be arranged and used as a core material, or a hollow structure may be adopted, and a reinforcing structure such as a shear web extending in the blade length direction and intervening between the skins in the thickness direction of the blade may be provided.

[0026] Further, the present invention is characterized by having at least one layer of a fiber-reinforced composite material in which the reinforcing fibers are unidirectionally oriented. The unidirectionally oriented fiber-reinforced composite material has no fiber orientation in the layer thickness direction and is likely to obtain high mechanical properties. Also, the anisotropy of the fiber-reinforced composite material can be strongly exhibited, which is preferable.

[0027] Further, in the present invention, among the layers of the fiber-reinforced composite material in which the reinforcing fibers are oriented uniaxially, a layer in which the reinforcing fibers are oriented at an angle of 60° or more with respect to the root direction (blade length direction) from the tip to the root of the propeller blade is characterized in that the reinforcing fibers are interrupted at a fiber length of 10 to 100 mm, at least in the root portion of the propeller blade (this layer may be referred to as the "chord direction interrupted fiber layer" for convenience). Here, the root direction (blade length direction) from the tip to the root of the propeller blade refers to the long side direction of the rectangle with the smallest area among the rectangles circumscribing the image obtained by projecting parallel light rays such as natural light perpendicularly to the rotation plane of the propeller blade (conveniently referred to as the "circumscribing rectangle"). Further, "interrupted" means that the fibers in the layer that were continuous are present in the layer in a state where they are cut, and externally, a discontinuous point is observed when tracing along the longitudinal direction of the fibers. As shown in FIG. 1, this discontinuous point can be formed by making a cut 102 in the fiber-reinforced composite material in which the reinforcing fibers 103 are oriented uniaxially and cutting the fibers. The root portion refers to the region within 30% of the blade length from the blade root. When straight lines intersect, two sets of vertical angles can be recognized at the intersection point, but in the present invention, the angle formed by the blade length direction and the orientation direction of the reinforcing fibers is determined by the smaller angle.

[0028] In the above chordwise intermittent fiber layer, the cuts may be made over the entire area of the propeller blade, or may be made only at the root of the propeller blade. By providing the chordwise intermittent fiber layer, it is possible to absorb the chordwise perimeter change that occurs when shaping the propeller blade and the perimeter change between the inner and outer layers of the skin, and there is an advantage that the formability can be significantly improved without causing a decrease in the strength of the propeller blade. Since the change in the blade shape is particularly large at the root of the propeller blade, this effect is easily obtained. On the other hand, among the layers of the fiber-reinforced composite material in which the reinforcing fibers are oriented in a uniaxial orientation, for the layer in which the reinforcing fibers are oriented at an angle of less than 60° with respect to the tip-to-root direction (blade length direction) of the propeller blade, the fibers included in such a layer of the fiber-reinforced composite material are preferably continuous fibers. The layer oriented at an angle of less than 60° with respect to the blade length direction is less affected by the perimeter change when shaping the propeller blade and the perimeter change between the inner and outer layers of the skin, and has a small adverse effect on formability. On the other hand, since it greatly dominates the strength of the propeller blade, it is preferable to apply continuous fibers.

[0029] The state where the reinforcing fibers are interrupted with a fiber length of 10 to 100 mm means, for example, for a prepreg containing continuously oriented fibers in one direction, a state obtained by inserting a cut 102 into a prepreg in which reinforcing fibers 103 are oriented in one direction 101 as continuous fibers as shown in FIG. 1 (note that the outer edge of FIG. 1 is a notation for convenience in illustration, and in this figure, the actual reinforcing fibers 103 are continuous in the fiber orientation 101), or a state where short fibers with a fiber length of 10 to 100 mm are oriented uniaxially. In particular, when using a cut prepreg obtained by inserting a cut into a prepreg containing continuous fibers, there is no particular limitation on the cut insertion pattern.

[0030] Further, in the propeller blade of the present invention, in the region within 30% of the blade length from the blade root, it is preferable that the ratio of the maximum value to the minimum value of the outer periphery of the vertical cross section is 1.2 or more. The region within 30% of the blade length from the blade root is a region corresponding to a portion included in 30% of the length from the rotation center to the short side of the rectangle on the side farther from the rotation center in the long side direction of the circumscribed rectangle, which passes through the rotation center of the propeller blade, is parallel to the short side of the circumscribed rectangle, and is perpendicular to the rotation plane. When the short sides of the rectangle are equidistant from the rotation center, it corresponds to the portion included in 30% of the length from the rotation center to each short side of the rectangle. Further, the outer periphery of the vertical cross section is the outer peripheral length of the cross section perpendicular to the rotation plane obtained by cutting the propeller blade in parallel with the short side of the circumscribed rectangle. In particular, in the propeller blade in which the ratio of the maximum value to the minimum value of the outer periphery of the vertical cross section is 1.2 or more in the region within 30% of the blade length from the blade root, the improvement in formability is remarkable in the present invention.

[0031] In addition, the manufacturing method of the propeller blade of the present invention includes a step of laminating a plurality of sheet-like prepregs in which reinforcing fibers are uniaxially or multi-axially oriented to obtain a laminated prepreg (first step), a step of shaping the laminated prepreg into a propeller shape (second step), and a step of heat-curing the laminated prepreg in a propeller blade mold (third step). Among the prepregs in the form of a sheet, that is, a flat plate, in which the reinforcing fibers are uniaxially oriented, in the prepreg containing reinforcing fibers oriented at an angle of 60° or more with respect to the direction from the blade tip to the root (blade length direction) of the propeller blade, at least in the portion corresponding to the root of the propeller blade, the reinforcing fibers contained in the prepreg are intermittent with a fiber length of 10 to 100 mm. The portion corresponding to the root is a portion that is expected to become the root portion after being formed into the propeller blade.

[0032] When manufacturing the skin of a propeller blade using a fiber-reinforced composite material, it is preferably adopted to impregnate a fiber-reinforced base material with a resin to obtain a prepreg in a semi-cured state and then shape this prepreg into a propeller shape. In this way, it can be easily shaped into a desired shape and can be made into a high-strength member by curing. At this time, a prepreg in which the reinforcing fibers are unidirectionally oriented or oriented in multiple axes can be used. On the other hand, since the skin of the propeller blade has a complex shape as described above, the unidirectionally or multi-axially oriented reinforcing fibers are stretched, and it is difficult to shape them into a wing shape. Especially when attempting to automate the shaping process, this difficulty is even higher.

[0033] Therefore, in the method for manufacturing a propeller blade of the present invention, in order to obtain a propeller blade having high mechanical properties while improving the formability, particularly the automatic formability, for a prepreg containing reinforcing fibers oriented at an angle of 60° or more with respect to the root direction (blade length direction) of the propeller blade from the tip of the blade, a prepreg in which the reinforcing fibers contained in the prepreg are interrupted with a fiber length of 10 to 100 mm is used. Here, in the prepreg, the cuts are made at least in the portion corresponding to the root, and the cuts may be made throughout the whole. Such a prepreg can be easily obtained by cutting continuous reinforcing fibers so that the fiber length becomes 10 to 100 mm. In the first step, such a prepreg and other prepregs are laminated to form a laminated prepreg. Also, the laminated prepreg can be trimmed in advance with respect to the portions that are planned to be unnecessary when shaping it into the skin of the propeller blade for the second step. Adding such steps is advantageous in terms of automating the process. Also, for a layer of a fiber-reinforced composite material in which the reinforcing fibers are unidirectionally oriented, when the reinforcing fibers are oriented at an angle of less than 60° with respect to the root direction (blade length direction) of the propeller blade from the tip of the blade, it is preferable that the fibers contained in such a layer of the fiber-reinforced composite material are continuous fibers.

[0034] Subsequently, the laminated prepreg is shaped into a propeller shape. When shaping into a propeller shape, it is preferable to perform shaping by pressing against a mold having the shape of the outer layer side surface of the propeller blade skin or a mold having the shape of the inner layer side surface. Examples of the mold having the shape of the outer layer side surface of the propeller blade skin or the mold having the shape of the inner layer side surface include a propeller blade forming mold, a propeller blade core, or a preform mold. The propeller blade forming mold is a mold that forms the blade shape of the propeller blade when the prepreg is heated and cured in subsequent processes. Further, the propeller blade core may be, for example, a porous body remaining in the final molded product, or may be a core for forming a hollow portion inside the propeller blade after removing the prepreg after heating and curing. The preform mold is a mold used only for shaping the laminated prepreg into a propeller shape. Note that the laminated prepreg shaped into a propeller shape in the second step is shaped into the shape of the final propeller blade through the third step. For example, from the viewpoint of suppressing the biting of the prepreg into the propeller blade forming mold and for reasons such as being heated, pressurized, cured, and compressed to form a molded product, it is not necessary to shape the laminated prepreg after the second step to match the shape of the final propeller blade. By pressing the laminated prepreg produced as described above against a mold having the shape of the outer layer side surface or the inner layer side surface of the propeller blade skin, such as a propeller blade forming mold, a propeller blade core, or a preform mold, the shaping can be completed well without fiber tension or the like. Further, by shaping into a propeller shape in this way, automation becomes possible.

[0035] In the third step, the laminated prepreg shaped into a propeller shape obtained through the second step is heated and cured. The heating and curing is performed by placing the laminated prepreg shaped into a propeller shape in a propeller blade forming mold in order to fix it into the blade shape of the propeller blade.

[0036] In the present invention, in the second step, it is preferable to press and shape the laminated prepreg while applying tension to the laminated prepreg against the propeller blade core, preform mold, or propeller blade forming mold. When shaping into a propeller shape while applying tension, by adopting the chordwise intermittent fiber layer, the elongation effect can be effectively utilized to shape it well without wrinkles. There is no particular limitation on the direction in which tension is applied. However, when applying tension to a portion having a curvature in the chordwise direction on the surface of the propeller blade or a portion where the chordwise blade circumference changes significantly in the chordwise direction, it is preferable to apply tension in the chordwise direction to achieve good shaping.

[0037] In the present invention, when shaping the laminated prepreg into a propeller shape, the laminated prepreg is disposed between a mold having the shape of the outer layer side surface of the propeller blade skin and a mold having the shape of the inner layer side surface, and the laminated prepreg is sandwiched and pressed between the two molds to be shaped into a propeller shape. And before pressing the laminated prepreg between the two molds, it is preferable to bring only a part of the laminated prepreg into contact with the mold having the shape of the inner layer side surface, and then perform pressing.

[0038] By disposing the laminated prepreg between a mold having the shape of the outer layer side surface of the propeller blade skin and a mold having the shape of the inner layer side surface, sandwiching and pressing the laminated prepreg between the two molds, it is easy to shape it into a propeller shape and is also advantageous in automation. Also, at the stage before pressing the laminated prepreg between the two molds, when only a part of the laminated prepreg is brought into contact with the mold having the shape of the inner layer side surface and then pressing is performed, the movement of the laminated prepreg in contact with the mold having the shape of the inner layer side surface is fixed, and the outer layer side surface of the laminated prepreg is stretched. When performing pressing while applying tension, it is preferable to change the direction in which tension is applied and increase the pressing force as the contact area between the laminated prepreg and the mold having the shape of the inner layer side surface increases. When manufacturing a propeller blade using the manufacturing method of the present invention, the formability can be effectively improved by providing the chordwise intermittent fiber layer, and it can be shaped well without wrinkles.

[0039] In the manufacturing method of the present invention, when shaping the laminated prepreg into a propeller shape, it is preferable to preheat the previously laminated prepreg. By preheating the laminated prepreg, the elongation effect of the cut prepreg can be easily obtained, the shaping force required when shaping into a propeller shape can be reduced, and the formability can be improved. From the above, the present invention is particularly suitable for automatically obtaining a three-dimensional preform and improving the production rate of propeller blades, and for reducing the working variations during production and maintaining the high quality of propeller blades.

Example

[0040] Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not construed as being limited to the description of the terms of such examples. Note that as the orientation direction of the reinforcing fiber, the direction from the blade root to the blade tip (blade length direction) is 0°, and the direction from the leading edge of the blade to the trailing edge of the blade (chord direction) is 90°.

[0041] (Example 1) P707AG-15 carbon fiber unidirectional prepreg manufactured by Toray Composite Materials America, Inc. was prepared and cut out according to the shape corresponding to each of the upper skin and the lower skin of the propeller blade skin. By adjusting the cutting, a prepreg (prepreg 1) with carbon fibers oriented in the 0° direction and a prepreg (prepreg 2) with carbon fibers oriented in the 90° direction were obtained.

[0042] For prepreg 2, linear cuts in the 10° direction with respect to the orientation direction of the carbon fibers were periodically inserted during cutting, and all the carbon fibers were in a state of being interrupted by the cuts, and the fiber length after the cuts were applied was set to 30 mm. At this time, the length of the cut in the direction orthogonal to the carbon fibers was 10 mm.

[0043] Subsequently, an F6273C-07M carbon fiber fabric prepreg manufactured by Toray Composite Materials America, Inc., in which a carbon fiber fabric, which is an orthogonal biaxial fabric, is impregnated with a resin, was prepared and cut out according to the shape corresponding to each of the upper skin and the lower skin of the propeller blade skin. A prepreg (prepreg 3) was obtained in which the carbon fibers in the fabric were cut out so as to be oriented in the -45° direction and the +45° direction by the cutting.

[0044] Corresponding to each of the upper skin and the lower skin of the propeller blade, the prepreg 1, prepreg 2, and prepreg 3 were laminated in the order of [prepreg 3 / prepreg 1 / prepreg 1 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 2 / prepreg 1 / prepreg 2 / prepreg 3] from the side of the surface on the outer side of the blade, and a laminated prepreg serving as the upper skin and the lower skin of the propeller blade was obtained.

[0045] The obtained laminated prepreg was pressure-bonded to the surface on the inner layer side when used as the skin of a preform mold having a cavity in the shape of a propeller skin while applying tension in the chord direction of the blade, and a state was obtained in which a part of the surface that should be the inner layer surface when used as the skin of the laminated prepreg was shaped on the surface of the preform mold. Then, the preform mold was closed to obtain a laminated prepreg shaped into the shape of the upper skin of the propeller blade. Next, in the same manner as for the upper skin, a laminated prepreg shaped into the shape of the lower skin was obtained. Neither the laminated prepreg that becomes the upper skin nor the laminated prepreg that becomes the lower skin when used as the skin had wrinkles or fiber bulges during shaping.

[0046] The polymethacrylimide rigid foam ROHACELL (registered trademark) 110 IG-F manufactured by Polyplastics Co., Ltd. was machined into the core shape of a propeller blade to obtain a porous core member. Then, the porous core member was sandwiched between a laminated prepreg shaped into the shape of the upper skin and a laminated prepreg shaped into the shape of the lower skin, and then placed in a propeller blade molding die, clamped, and then heat-cured and molded in an oven.

[0047] It was visually confirmed that the surface of the 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 were no disturbances in the layer structure due to wrinkles or voids.

[0048] (Example 2) A porous core member obtained by the same method as described in Example 1 and a mold (mold 1A) that gives the shape of the outer surface of the upper skin of the propeller blade when used as the skin were prepared. Next, the laminated prepreg obtained by the same method as described in Example 1 was preheated to 60°C and pressure-bonded to the porous core member while applying tension in the chord direction to obtain a state in which a part of the surface that should become the inner layer side surface when the laminated prepreg is used as the skin was shaped to the outer surface of the porous core member. Then, this was covered with mold 1A, the laminated prepreg was sandwiched between the porous core member and mold 1A, pressure was applied to complete the shaping of the laminated prepreg, and then mold 1A was removed to obtain a composite (composite A) coated with the laminated prepreg that becomes the upper skin of the propeller blade when the porous core member is used as the skin.

[0049] Next, a mold (mold 1B) that gives the shape of the outer surface of the lower skin of the propeller blade when used as the skin and a laminated prepreg obtained by the same method as described in Example 1 were prepared, and the same operation as above was performed on the remaining half surface of the composite A that was not coated with the laminated prepreg to coat it with the laminated prepreg that becomes the upper skin of the propeller blade when used as the skin. When used as the skin, neither the laminated prepreg that becomes the upper skin nor the laminated prepreg that becomes the lower skin had wrinkles or fiber bulges during shaping.

[0050] After that, the composite coated with the laminated prepreg obtained by the above operation was placed in a propeller blade molding die, clamped, and then heat-cured and molded in an oven.

[0051] 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.

[0052] (Comparative Example 1) A molded product (propeller blade) was obtained in the same manner as in Example 1 except that no notch was provided in Prepreg 2. In the process of obtaining a laminated prepreg shaped to the shape of the upper skin of the propeller blade, the carbon fibers protruded in the layer corresponding to Prepreg 2, and the shaped laminated prepreg was wrinkled.

[0053] 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 checking with a microscope, disturbance in the layer structure due to wrinkles was confirmed, and further, it was confirmed that voids existed at that location. It is clear that the reliability of the molded product is inferior to that of the molded product of the example due to the existence of disturbance in the layer structure and voids.

Industrial Applicability

[0054] The propeller blade according to the present invention is a propeller blade that is particularly excellent in formability during molding, enables manufacturing automation, and has high mechanical properties, and can be suitably used for propellers such as UAM and drones.

Explanation of Signs

[0055] 101: Fiber orientation direction 102: Notch 103: Reinforcing fiber

Claims

1. A propeller blade having a member laminated with a fiber-reinforced composite material in which reinforcing fibers are uniaxially or multiaxially oriented and shaped into a propeller shape, the member having at least one layer of a fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented, and among the layers of the fiber-reinforced composite material in which the reinforcing fibers are uniaxially oriented, for the layers in which the reinforcing fibers are oriented at an angle of 60° or more with respect to the tip-to-root direction (blade length direction) of the propeller blade, at least in the root portion of the propeller blade, the reinforcing fibers are interrupted with a fiber length of 10 to 100 mm. The propeller blade is characterized by this.

2. The propeller blade according to claim 1, wherein in a region within 30% of the blade length from the blade root, the ratio of the maximum value to the minimum value of the outer circumference of the vertical cross section is 1.2 or more.

3. A method for manufacturing a propeller blade, comprising a step of laminating a plurality of sheet-shaped prepregs in which reinforcing fibers are uniaxially or multiaxially oriented to obtain a laminated prepreg (first step), a step of shaping the laminated prepreg into a propeller shape (second step), and a step of heat-curing the laminated prepreg in a propeller blade mold (third step). Among the sheet-shaped prepregs in which the reinforcing fibers are uniaxially oriented, in the prepreg containing reinforcing fibers oriented at an angle of 60° or more with respect to the tip-to-root direction (blade length direction) of the propeller blade, at least in the portion corresponding to the root of the propeller blade, the reinforcing fibers contained in the prepreg are interrupted with a fiber length of 10 to 100 mm. The method for manufacturing a propeller blade is characterized by this.

4. The method for manufacturing a propeller blade according to claim 3, wherein in the second step, pressure is applied to the surface of the laminated prepreg while applying tension to the laminated prepreg to shape the shape of the outer layer side surface or the inner layer side surface of the propeller blade skin.

5. The method for manufacturing a propeller blade according to claim 3 or 4, wherein in the second step, the laminated prepreg is preheated and shaped into a propeller shape.

6. The second step is a step of disposing a laminated prepreg between a mold having the shape of the outer layer side surface of the propeller blade skin and a mold having the shape of the inner layer side surface, 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, bringing only a part of the laminated prepreg into contact with the mold having the shape of the inner layer side surface, and then performing press-bonding. The method for manufacturing a propeller blade according to claim 3 or 4, characterized in that.

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