Blade for missile

Abstract

To provide a blade for a missile which is excellent in mechanical strength and surface quality and exhibits high rotation efficiency.SOLUTION: A blade for a missile is provided, in which at least an outer peripheral wall surface is formed of a fiber-reinforced resin containing a carbon fiber (A) and a thermoplastic resin (B). In the fiber-reinforced resin, when the total of the carbon fiber (A) and the thermoplastic resin (B) is 100 pts.wt., a content of the carbon fiber (A) is 1 to 50 pts.wt., a content of the thermoplastic resin (B) is 50 to 99 pts.wt., and a weight average fiber length of the carbon fiber (A) is 300 to 2,500 μm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a blade for an aerial vehicle such as an industrial drone. [Background technology]

[0002] Fiber-reinforced resin molded products containing carbon fiber and thermoplastic resin are lightweight and have excellent mechanical properties, and are therefore widely used in sporting goods, aerospace, general industrial applications, etc. Carbon fiber, when combined with thermoplastic resin, exhibits excellent reinforcing effects.

[0003] To maximize the reinforcing effect of carbon fibers, they must be uniformly dispersed throughout the molded product. If the carbon fibers remain in a non-uniform state, i.e., in the form of fiber bundles, reduced mechanical strength and impact strength are observed. Therefore, when used in flying object blades, which require high strength, sufficient reinforcing effect is not obtained, and there is a risk of deflection (flapping, dragging) occurring during blade rotation in actual use. Furthermore, non-uniform fiber dispersion can cause defects such as unevenness on the surface of the molded product. If the surface of a flying object blade is uneven, this can cause air resistance disturbances and hinder stable rotation. For these reasons, there is a demand for flying object blades with excellent mechanical strength, elastic modulus, and surface quality.

[0004] One method for improving the mechanical strength and surface quality of molded articles is to use a terpene resin as a thermoplastic resin (Patent Document 1). However, this method has the problem of insufficient mechanical strength and surface quality due to insufficient fiber dispersion of carbon fibers in the resulting molded article. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-138379 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a flying object blade that has excellent mechanical strength and surface quality and exhibits high rotation efficiency. [Means for solving the problem]

[0007] The present invention, which solves the above-mentioned problems, provides a flying object blade having at least an outer peripheral wall surface formed of a fiber-reinforced resin containing carbon fiber (A) and thermoplastic resin (B), wherein, when the total of the carbon fiber (A) and the thermoplastic resin (B) in the fiber-reinforced resin is 100 parts by weight, the content of the carbon fiber (A) is 1 to 50 parts by weight, the content of the thermoplastic resin (B) is 50 to 99 parts by weight, and the weight-average fiber length of the carbon fiber (A) is 300 to 2500 μm. A flying object equipped with the flying object blade of the present invention is also an aspect of the present invention. [Effects of the Invention]

[0008] The flying object blade of the present invention has excellent mechanical strength and surface quality, and is therefore useful for industrial drones, etc. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below. In this specification, the symbol "to" is primarily used to indicate a range including both ends of the range.

[0010] At least the outer peripheral wall surface of the flying object blade of the present invention (hereinafter sometimes simply referred to as "blade") is formed from a fiber-reinforced resin (hereinafter referred to as CFRTP) containing carbon fiber (A) and thermoplastic resin (B). The carbon fiber (A) serves as a reinforcing material to impart high mechanical properties to the molded product, and the thermoplastic resin (B) serves to firmly hold the carbon fiber (A). Note that "at least the outer peripheral wall surface is formed from CFRTP" means that the entire blade may be formed from CFRTP as a solid body, the outer peripheral wall of the hollow portion may be formed from CFRTP, or the outer peripheral wall covering a separately molded core member may be formed from CFRTP, or a layer of CFRTP may be formed only on the surface of the outer peripheral wall made from a material other than CFRTP.

[0011] The content of carbon fiber (A) in the CFRTP is 1 to 50 parts by weight, assuming that the total of carbon fiber (A) and thermoplastic resin (B) is 100 parts by weight. If the content of carbon fiber (A) is less than 1 part by weight, the mechanical strength of the blade will decrease. The content of carbon fiber (A) is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, even more preferably 15 parts by weight or more, and most preferably 20 parts by weight or more. If the content of carbon fiber (A) exceeds 50 parts by weight, the dispersion of carbon fiber (A) in the blade will decrease, resulting in a decrease in surface quality, and fiber breakage will occur due to collisions between fibers during molding, which will likely cause a decrease in the mechanical strength and surface quality of the blade. The content of carbon fiber (A) is preferably 40 parts by weight or less, more preferably 35 parts by weight or less, and even more preferably 30 parts by weight or less.

[0012] Examples of types of carbon fiber (A) include PAN-based carbon fiber, pitch-based carbon fiber, cellulose-based carbon fiber, vapor-grown carbon fiber, and graphitized fibers thereof. PAN-based carbon fiber is a carbon fiber made from polyacrylonitrile fiber. Pitch-based carbon fiber is a carbon fiber made from petroleum tar or petroleum pitch. Cellulose-based carbon fiber is a carbon fiber made from viscose rayon or cellulose acetate. Vapor-grown carbon fiber is a carbon fiber made from hydrocarbons. Of these, PAN-based carbon fiber is preferred because of its excellent balance between strength and elastic modulus. Carbon fiber coated with a metal such as nickel, copper, or ytterbium can also be used to improve conductivity.

[0013] The carbon fiber (A) may be surface-treated for the purpose of improving the adhesiveness of the thermoplastic resin (B) which is the matrix resin, etc. Examples of the surface treatment method include electrolytic treatment, ozone treatment, and ultraviolet treatment.

[0014] The surface oxygen concentration ratio [O / C] of the carbon fiber (A) is preferably 0.05 to 0.5. The surface oxygen concentration ratio [O / C] is the ratio of the number of oxygen (O) to carbon (C) atoms on the fiber surface measured by X-ray photoelectron spectroscopy. A surface oxygen concentration ratio of 0.05 or more ensures a sufficient number of functional groups on the surface of the carbon fiber (A), resulting in stronger adhesiveness and thus improved bending strength and tensile strength. The surface oxygen concentration ratio [O / C] is more preferably 0.08 or more, and even more preferably 0.10 or more. In addition, the upper limit of the surface oxygen concentration ratio is generally preferably 0.5 or less, more preferably 0.4 or less, and even more preferably 0.3 or less, in view of the balance between the handleability and productivity of the carbon fiber (A).

[0015] The surface oxygen concentration ratio of carbon fiber (A) is determined by X-ray photoelectron spectroscopy according to the following procedure: First, the sizing agent adhering to the surface of carbon fiber (A) is removed with a solvent, the carbon fiber bundle is cut into 20 mm pieces, and the pieces are spread out and arranged on a copper sample support. Then, AlKα1, 2 is used as an X-ray source, and 1 × 10 -8The pressure is maintained at Torr. The kinetic energy (KE) of the main C1s peak is set to 1202 eV as a correction value for peaks associated with charging during measurement. The C1s peak area is determined by drawing a straight baseline in the range of 1191 to 1205 eV as the KE. The O1s peak area is determined by drawing a straight baseline in the range of 947 to 959 eV as the KE. The atomic ratio is then calculated from the ratio of the O1s peak area to the C1s peak area using the instrument-specific sensitivity correction value.

[0016] The means for controlling the surface oxygen concentration ratio [O / C] to 0.05 to 0.5 is not particularly limited, but for example, it can be controlled by modifying the surface of the carbon fiber, and examples of such methods include electrolytic oxidation treatment, chemical oxidation treatment, and gas phase oxidation treatment, and among these, electrolytic oxidation treatment is preferred.

[0017] The average fiber diameter of the carbon fibers (A) is not particularly limited, but from the viewpoint of the mechanical properties and surface quality of the blade, it is preferably 1 to 20 μm, more preferably 3 to 15 μm.

[0018] The carbon fibers (A) may be coated with a sizing agent to prevent fuzzing of the carbon fibers (A) or to improve adhesion between the carbon fibers (A) and the thermoplastic resin (B). Specific examples of sizing agents include epoxy resins, phenolic resins, polyethylene glycol, polyurethane, polyester, emulsifiers, and surfactants. Two or more of these may be used. These sizing agents are contained on the surfaces of the carbon fibers (A) in the molding material. The sizing agent is preferably water-soluble or water-dispersible, and an epoxy resin with excellent wettability with the carbon fibers (A) is preferred. Among these, a multifunctional epoxy resin is more preferred.

[0019] The weight-average fiber length (Lw) of the carbon fiber (A) contained in the CFRTP is 300 to 2500 μm. A weight-average fiber length (Lw) of 300 μm or more further improves the mechanical strength and warp suppression effect of the blade. Lw is preferably 400 μm or more, and more preferably 500 μm or more. On the other hand, a weight-average fiber length (Lw) of 2500 μm or less suppresses entanglement between the single carbon fiber (A) fibers and further improves dispersibility, thereby further improving the mechanical strength, surface quality, and particularly surface smoothness of the blade. Lw is more preferably 2000 μm or less, and even more preferably 1800 μm or less. Here, the "weight-average fiber length" in the present invention refers to a weight-average fiber length calculated using the following formula, which takes into account the contribution of fiber length, rather than simply taking a number average, by applying the calculation method for weight-average molecular weight to the calculation of fiber length. However, the following formula applies when the fiber diameter and density of the carbon fiber (A) are constant. Weight average fiber length = Σ(Mi 2 ×Ni) / Σ(Mi×Ni) Mi: Fiber length (mm) Ni: Number of reinforcing fibers with fiber length Mi

[0020] The weight-average fiber length can be measured by the following method. Using an optical microscope equipped with a hot stage, an appropriate test piece is cut from the blade, and the piece is heated between glass plates on a hot stage appropriately set at 150 to 450°C, matching the melting temperature of the thermoplastic resin (B) used. The piece is then formed into a film and uniformly dispersed. The resulting film is then observed under an optical microscope (50 to 200 magnifications) while the thermoplastic resin (B) is molten. The fiber lengths of 1,000 randomly selected carbon fibers (A) are measured, and the weight-average fiber length (Lw) is calculated using the above formula. Alternatively, the test piece cut from the blade is placed in a solvent that dissolves the thermoplastic resin (B), and appropriately heated to prepare a solution in which the carbon fibers (A) are uniformly dispersed. The solution is then filtered, and the carbon fibers (A) dispersed on the filter paper are observed under an optical microscope (50 to 200 magnifications). The fiber lengths of 1,000 randomly selected carbon fibers (A) are measured, and the weight-average fiber length (Lw) is calculated using the above formula. The filter paper used here may be quantitative filter paper (model number: No. 5C) manufactured by Advantec Co., Ltd.

[0021] The CFRTP preferably contains 20 to 99% of carbon fibers (A) having a fiber length of 300 to 10,000 μm. By containing 20% ​​or more of fibers having a fiber length of 300 to 10,000 μm, the reinforcing effect can be further enhanced, and the mechanical strength of the blade can be increased. The carbon fibers having a fiber length of 300 to 10,000 μm are more preferably 30% or more, and even more preferably 40% or more. Furthermore, by limiting the carbon fibers having a fiber length of 300 to 10,000 μm to 99% or less, the surface quality can be improved. The carbon fibers having a fiber length of 300 to 10,000 μm are more preferably 80% or less, and even more preferably 70% or less.

[0022] The content of the thermoplastic resin (B) in the CFRTP constituting the blade is 50 to 99 parts by weight, assuming that the total of the carbon fiber (A) and the thermoplastic resin (B) is 100 parts by weight.

[0023] The thermoplastic resin (B) preferably has a glass transition point of 30 to 250° C. The glass transition point here is determined by using differential scanning calorimetry (DSC) in accordance with JIS K-7122 (1987), by heating a resin from 30° C. at a temperature increase rate of 10° C. / min to a temperature about 30° C. higher than the end of the melting peak (in the case of a crystalline resin) or to a temperature about 30° C. higher than the end of the glass transition (in the case of an amorphous resin) at a temperature increase rate of 10° C. / min (1 st After holding the temperature for 10 minutes, the sample was cooled at a rate of 10°C / min to a temperature below 30°C, and then heated again from 30°C at a rate of 20°C / min to a temperature approximately 30°C higher than the end of the glass transition (2 nd Run) ndThe glass transition temperature is defined as the point where a line equidistant in the vertical direction from the line extending the low-temperature and high-temperature baselines in a differential scanning calorimetry chart intersects with the curve representing the stepwise change in the glass transition. A glass transition temperature of 30 to 250°C is preferred because it improves the moldability and processability of the blade and allows the blade to exhibit mechanical properties and blade rotation performance even when used in a high-temperature environment. A range of 40 to 240°C is more preferred, a range of 60 to 230°C is even more preferred, and a range of 80 to 220°C is most preferred.

[0024] Examples of such thermoplastic resins (B) include polyetherimide resins, polyimide resins, polyamideimide resins, polysulfone resins, polyethersulfone resins, polyphenylene ether resins, modified polyphenylene ether resins, polyketone resins, polyaryl ketone resins, polyaryl ether ketone resins (particularly polyether ether ketone resins and polyether ketone ketone resins), polyarylate resins, polyamide resins, etc. Two or more of these can also be used in combination. In particular, polyetherimide resins, polyaryl ether ketone resins, and polyethersulfone resins, which have an excellent balance of mechanical properties and heat resistance, are preferred.

[0025] In addition to the carbon fibers (A) and thermoplastic resin (B), the CFRTP may contain 0.1 to 20 parts by weight of a resin compound (C) selected from the group consisting of epoxy resins and phenolic resins, based on 100 parts by weight of the total of the carbon fibers (A) and the thermoplastic resin (B).

[0026] The epoxy resin used as the resin compound (C) is not particularly limited, and examples thereof include bisphenol A type epoxy resins, bisphenol F type epoxy resins, aliphatic epoxy resins, phenol novolac type epoxy resins, etc. Among these, from the viewpoint of an excellent balance between viscosity and heat resistance, bisphenol A type epoxy resins and bisphenol F type epoxy resins are more preferred, and bisphenol A type epoxy resins are even more preferred.

[0027] The epoxy equivalent of the epoxy resin used as the resin compound (C) is preferably 300 to 3000 g / eq. It is more preferably 500 to 2000 g / eq, and even more preferably 800 to 1500 g / eq. If the epoxy equivalent is less than 300 g / eq, the reactivity is high, and self-reaction or reaction with the carbon fiber (A) or the thermoplastic resin (B) occurs during molding, which may hinder fiber dispersion. If the epoxy equivalent is more than 3000 g / eq, the interaction with the carbon fiber (A) bundles is weak, resulting in poor compatibility with the carbon fiber (A) during impregnation. This not only makes impregnation difficult, but also may result in insufficient fiber dispersion during molding. An epoxy equivalent of 300 to 3000 g / eq ensures sufficient fiber dispersion during molding. The epoxy equivalent can be measured according to the test method of JIS K7236 (2009).

[0028] The phenolic resin used as the resin compound (C) refers to a thermoplastic polymer having a phenolic skeleton. The phenolic skeleton may have a substituent, and may be cresol or naphthol. Specific examples of the phenolic resin include phenol novolac resin, o-cresol novolac resin, phenol aralkyl resin, naphthol novolac resin, and naphthol aralkyl resin. Among these, o-cresol novolac resin has an excellent balance between heat resistance and ease of handling, such as melt viscosity.

[0029] The melting point of the phenolic resin used as the resin compound (C) is not particularly limited, but from the viewpoint of improving the heat resistance and handleability of the molding material and suppressing bleed-out during long-term storage of the molding material, it is preferably above 80°C. More preferably, it is above 100°C, and even more preferably above 120°C. The upper limit of the melting point is not particularly limited, but from the viewpoint of handleability, it is preferably 200°C or less. More preferably, it is 180°C or less, and even more preferably 150°C or less.

[0030] The number average molecular weight of the resin compound (C) is preferably 100 to 50,000. If the number average molecular weight is 100 or more, the mechanical strength of the blade can be further improved. The number average molecular weight is more preferably 300 or more, even more preferably 500 or more, and most preferably 1,000 or more. If the number average molecular weight is 50,000 or less, the viscosity of the resin is appropriately low, which results in excellent impregnation into the carbon fibers (A) contained in the blade and further improves the dispersibility of the carbon fibers (A) in the blade. The number average molecular weight of the resin compound (C) is more preferably 25,000 or less, even more preferably 15,000 or less, and even more preferably 10,000 or less. The number average molecular weight of such a compound can be measured using gel permeation chromatography (GPC).

[0031] The resin compound (C) preferably has a heat loss of 5% by weight or less when heated at a rate of 10°C / min (in air) at the molding temperature. It is more preferably 3% by weight or less, and even more preferably 1.5% or less. When the heat loss is 5% by weight or less, the generation of decomposition gases can be suppressed when the resin compound (C) is impregnated into the carbon fiber (A), and the generation of voids can be suppressed during molding. Furthermore, the generation of gases can be suppressed, particularly during molding at high temperatures.

[0032] The weight loss of the resin compound (C) at the molding temperature can be determined by measuring the weight at the molding temperature by thermogravimetric analysis (TGA) using a platinum sample pan in an air atmosphere at a heating rate of 10°C / min.

[0033] The melt viscosity of the resin compound (C) at 350°C is preferably 0.01 to 0.5 Pa·s, more preferably 0.05 to 0.3 Pa·s, and even more preferably 0.07 to 0.2 Pa·s. If the melt viscosity at 350°C is less than 0.01 Pa·s, the mechanical strength of the resin compound (C) is low, which may impair the mechanical strength of the blade. If the melt viscosity is greater than 0.5 Pa·s, the resin compound (C) may not be able to penetrate deep into the carbon fibers (A). By lowering the melt viscosity of the resin compound (C), the resin compound (C) flows and moves more easily within the mixture of the carbon fibers (A), thermoplastic resin (B), and resin compound (C). The melt viscosity of the resin compound (C) can be determined by measuring it using a viscoelasticity measuring instrument with 40 mm parallel plates at 0.5 Hz and 350°C.

[0034] The content of the resin compound (C) in the CFRTP is preferably 0.1 to 20 parts by weight per 100 parts by weight of the total of the carbon fiber (A) and thermoplastic resin (B). If the content of the resin compound (C) is 0.1 part by weight or more, the dispersibility of the carbon fiber (A) within the blade is further improved. It is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and even more preferably 5 parts by weight. On the other hand, if the content of the resin compound (C) is 20 parts by weight or less, it is possible to suppress a decrease in the mechanical strength of the thermoplastic resin (B), thereby further improving the mechanical strength of the blade. It is preferably 15 parts by weight or less, more preferably 12 parts by weight or less, and even more preferably 10 parts by weight or less.

[0035] The CFRTP constituting the blade may contain other components in addition to the components (A) to (C) described above, provided that the object of the present invention is not impaired. Examples of such other components include thermosetting resins, inorganic fillers other than carbon fiber (A), flame retardants, crystal nucleating agents, ultraviolet absorbers, antioxidants, impact absorbers, vibration dampers, antibacterial agents, insect repellents, deodorizers, coloring inhibitors, heat stabilizers, release agents, antistatic agents, plasticizers, lubricants, colorants, pigments, dyes, foaming agents, foam control agents, and coupling agents.

[0036] The average surface roughness of the outer peripheral wall surface of the blade is preferably 0.1 to 3.0 μm. By making the average surface roughness of the outer periphery 0.1 μm or more, paintability can be ensured and an excellent balance of surface air resistance can be achieved. The average surface roughness is more preferably 0.3 μm or more. Furthermore, by making the average surface roughness 3.0 μm or less, the surface air resistance of the blade can be reduced, resulting in even higher rotation efficiency.

[0037] The blade of the present invention preferably has a warpage rate in the blade thickness direction, calculated by the following formula (1), of less than 30% after 2000 cycles of a heat cycle test, in which one cycle is a heat treatment at 80°C for 30 minutes followed by a cooling treatment at -40°C for 30 minutes. Warpage rate in the blade thickness direction (%) = (warpage amount after heat cycle test - warpage amount before heat cycle test) / warpage amount before heat cycle test × 100 (1) By keeping the warpage rate in the blade thickness direction after the heat cycle test to less than 30%, the amount of warpage when the blade is subjected to repeated environmental temperature changes can be reduced, which is preferable because it can suppress flapping during blade rotation (described below) in an environment that simulates actual use. If the warpage rate exceeds 30%, the tip side of the blade will be significantly warped relative to the base side in the blade length direction, which is undesirable because it disrupts air resistance during rotation, reducing rotation efficiency and potentially causing contact with other parts during rotation. A warpage rate of less than 25% is more preferable, less than 20% is even more preferable, and less than 15% is most preferable.

[0038] Furthermore, the blade's bending modulus in the length direction is preferably 1.5 to 10 times that in the chord direction. Increasing the bending modulus in the blade length direction compared to the chord direction is preferable because flapping during rotation can be suppressed. The bending modulus in the blade length direction is more preferably 1.7 times or more, and even more preferably 2.0 times or more, of the bending modulus in the chord direction. On the other hand, if the bending modulus in the blade length direction is 10 times or more of the bending modulus in the chord direction, the difference in modulus between the blade length direction and the chord direction becomes too large, which may result in a decrease in dragging, which is undesirable. A value of 7 times or less is more preferable, 5 times or less is even more preferable, and 3 times or less is most preferable.

[0039] Furthermore, the air resistance coefficient Cd value in the axial shape connecting the leading edge to the trailing edge of the blade is preferably designed to be 0.1 or more and less than 0.4. By setting the Cd value within the above range, the air resistance applied when the blade rotates can be reduced, thereby improving rotation efficiency. A Cd value of 0.15 or more is preferable, and 0.2 or more is even more preferable. On the other hand, if the Cd value is 0.4 or more, the air resistance applied to the blade increases, which may reduce blade rotation efficiency. A value of 0.35 or less is more preferable, and 0.3 or less is even more preferable. For the same reason, the air resistance Fd value in the axial shape connecting the leading edge to the trailing edge of the blade is preferably 1 to 10,000 N, and more preferably 50 N or more. On the other hand, a value of 7,500 N or less is more preferable, a value of 5,000 N or less is even more preferable, and a value of 2,500 N or less is most preferable.

[0040] As described above, at least the outer peripheral wall surface of the blade of the present invention is formed from CFRTP, but if the aim is to further improve rotation efficiency by reducing weight, it is preferable that the interior of the blade is hollow.

[0041] Alternatively, the blade of the present invention may include a core material made of a porous resin material or a metal material, and a CFRTP layer formed to cover the core material. In this case, the porous resin material is preferably a fiber-reinforced resin having voids therein.

[0042] In this embodiment, the thickness of the outer peripheral wall is preferably 0.001 to 100 mm. By setting the outer peripheral wall thickness within the above range, the effect of protecting the gaps inside the blade can be enhanced, deformation during rotation can be suppressed, and excellent rotation efficiency can be achieved. If the thickness of the outer peripheral wall is less than 0.001 mm, the effect of protecting the internal gaps is insufficient, and the blade is prone to deformation during rotation. The thickness of the outer peripheral wall is more preferably 0.01 mm or more, even more preferably 0.1 mm or more, and most preferably 1 mm or more. Furthermore, an outer peripheral wall thickness exceeding 100 mm is undesirable because it increases the weight of the blade and reduces rotation efficiency. The thickness of the outer peripheral wall is more preferably 80 mm or less, even more preferably 60 mm or less, and most preferably 20 mm or less.

[0043] The blade of the present invention can be manufactured by various molding methods, such as injection molding, blow molding, extrusion molding, and press molding. In particular, injection molding or blow molding is preferred. For example, when manufacturing a hollow blade using a single CFRTP, blow molding is preferred. In the case of insert molding, a preformed core material made of a porous resin material or metal material is inserted into the mold of an injection molding machine, and the CFRTP is then injected into the mold to form a single piece with the core material. In this case, it is preferred that the entire surface of the core material be covered by an outer wall made of CFRTP, i.e., that the core material be enclosed within the outer wall.

[0044] The mold shape for molding the blade is preferably a mold having a gate for allowing the resin to flow in the longitudinal direction of the blade. By allowing the resin to flow in the longitudinal direction of the blade, the carbon fibers (A) contained therein can be easily oriented in the longitudinal direction of the blade, thereby achieving excellent mechanical strength. [Example]

[0045] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to the descriptions of these examples.

[0046] 1. Evaluation methods for various characteristics

[0047] (1) Weight average fiber length A 20 mm x 20 mm test piece cut from the blade was placed in a solvent that dissolved the thermoplastic resin (B) used in each example and comparative example, and then heated appropriately to obtain a solution in which the carbon fibers (A) were uniformly dispersed. The solution was then filtered using Advantec quantitative filter paper (No. 5C), and the carbon fibers (A) dispersed on the filter paper were observed under an optical microscope (50 to 200 magnifications). The fiber lengths of 1,000 randomly selected carbon fibers (A) were measured, and the weight-average fiber length (Lw) was calculated using the following formula: Average fiber length = Σ(Mi 2 ×Ni) / Σ(Mi×Ni) Mi: Fiber length (mm) Ni: Number of fibers with fiber length Mi

[0048] (2) Measurement of blade bending modulus Test pieces of the following size were cut out from the blade, and the bending properties of the obtained test pieces were measured in the blade longitudinal direction and chord direction in accordance with ISO 178 (1993). The support distance using a three-point bending test jig (indenter radius 5 mm) was set to 16 times the thickness of the cut test piece in accordance with ISO 178 (1993), and the bending modulus was measured at a test speed of 2 mm / min. The support distance in each test was set using the maximum thickness of each cut test piece. The testing machine used was an "Instron (registered trademark)" universal testing machine, Model 5566 (manufactured by Instron Corporation). Blade length: 150mm x 10mm Chord length direction: Maximum chord length x 10mm

[0049] (3) Measurement of surface smoothness (average surface roughness Ra) The molding material was injection molded, and an 80mm x 80mm test piece was cut out from the resulting blade. The Ra of the surface of the test piece on the mirror side of the mold was measured using a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd.) The smaller the Ra, the smaller the surface roughness, indicating better surface smoothness.

[0050] (4) Blade surface evaluation (fiber dispersion evaluation) A test piece of 80 mm × 80 mm was cut out from the blade, and the number of undispersed carbon fiber (A) bundles present on both the front and back surfaces was visually counted. Evaluation was performed on 50 blades, and the fiber dispersion of the total number was judged according to the following criteria, with A and B being considered as passing. A: Less than 1 undispersed CF bundle B: One undispersed CF bundle C: 2 or more undispersed CF bundles

[0051] (5) Blade dimension evaluation (evaluation of warpage) A 200 mm x 10 mm test piece was cut from the blade, and the difference (t2 - t1) between the height of the center of the test piece when viewed from the side (t1) and the height of the end portion when viewed from the blade tip side was evaluated. Measurements were taken three times per test piece, and the average value was used to evaluate each Example and Comparative Example. Evaluation was made according to the following criteria, with A and B being considered acceptable. A: (t2-t1) = less than 5 mm B: (t2-t1) = More than 5 mm and less than 10 mm C:(t2-t1)=10mm or more

[0052] (6) Measurement of warpage rate in the blade thickness direction A 200 mm × 10 mm test piece was cut from the blade, and the height (t3) of the end of the test piece as viewed from the blade tip side was measured. The test piece was then subjected to a heat cycle test (2000 cycles, each cycle consisting of heating at 80°C for 30 minutes, followed by cooling at -40°C for 30 minutes). The height (t3) of the end of the test piece as viewed from the blade tip side was measured, and the warpage rate (%) in the blade thickness direction was calculated according to (1) below. The warpage rate (%) was calculated by measuring the amount of warpage of the test piece before and after the heat cycle test and determining the deformation rate of the test piece. One measurement was performed per test piece, and each test piece was used for evaluation of each Example and Comparative Example. Evaluation was performed according to the following criteria, with A and B being considered pass. Warpage rate in the blade thickness direction (%) = (warpage amount after heat cycle test - warpage amount before heat cycle test) / warpage amount before heat cycle test × 100 (1) t3: Warpage before heat cycle test t4: Warpage after heat cycle test A: (t4 - t3) / t3 x 100 = less than 20% B: (t4-t3) / t3×100 = over 20% and under 30% C:(t4-t3) / t3×100=30% or more

[0053] (7) Measurement of blade thrust A base was prepared to hold the blades in place, with two blades per set, and the blades were attached to the base. A motor was then activated to rotate the attached blades. At this time, strain gauges were attached with adhesive to the surface of each blade to measure stress. The blades were rotated up to 5000 rpm, and the thrust force at that time was measured. The thrust force was calculated by converting the signal obtained from the strain gauge attached to the blade and processing it with a microcontroller.

[0054] (8) Blade flight performance evaluation (flapping evaluation) A base was prepared to hold the blades in place, with two blades per set, and the blades were attached to the base. The motor to rotate the attached blades was activated, and the blades were rotated up to 5000 rpm. The state of the blades' vertical vibration was then photographed with a high-speed camera, and the vertical contact angle of the blade was measured from the obtained images. The maximum vibration angle was taken as the flapping value, and the evaluation was made according to the following criteria, with A and B being considered pass. A: Maximum contact angle is 15° or less B: Maximum contact angle is over 15° and less than 25° C: Maximum contact angle is 25° or more

[0055] 2.Material

[0056] (1) Carbon fiber The fiber is made from a copolymer mainly composed of polyacrylonitrile, spun, baked, and surface-oxidized. The total number of single fibers is 24,000, the single fiber diameter is 7 μm, the mass per unit length is 1.6 g / m, and the specific gravity is 1.8 g / cm. 3 A continuous carbon fiber with a surface oxygen concentration ratio [O / C] of 0.2 was obtained. The strand tensile strength of this continuous carbon fiber was 4880 MPa, and the strand tensile modulus was 225 GPa. Next, a sizing agent mother solution was prepared by dissolving glycerol polyglycidyl ether as a polyfunctional compound in water to a concentration of 2 wt %, and the sizing agent was applied to the carbon fiber by immersion, followed by drying at 230°C. The amount of sizing agent attached to the carbon fiber thus obtained was 1.0 wt %.

[0057] (2) Carbon fiber reinforced plastic (CFRP) with continuous porous structure Carbon fiber was used as the reinforcing fiber and cut into 5 mm pieces with a cartridge cutter to obtain chopped carbon fiber. A dispersion of water and a surfactant was prepared, and a reinforcing fiber mat was produced using this dispersion and the chopped carbon fiber. The paper-formed carbon fiber mat was dried in a drying oven at 200 °C for 30 minutes to obtain a reinforcing fiber mat. Next, a laminate was prepared by arranging the reinforcing fiber mat and PA6 resin in the following order: PA6 resin / reinforcing fiber mat / reinforcing fiber mat / PA6 resin. Then, the following steps (I) to (IX) were carried out in order to prepare a CFRP having a continuous porous structure. (I) The laminate was placed in a press mold cavity preheated to 250°C and the mold was closed. (II) Then, after maintaining the temperature for 120 seconds, a pressure of 3 MPa was applied and maintained for another 60 seconds. (III) The mold cavity was closed, and the cavity temperature was cooled to 50°C while maintaining the pressure. (IV) The mold was opened and the precursor of the porous body (a) was taken out. (V) Six layers of the precursor of the porous body (a) were stacked and placed in a press molding die cavity preheated to 260°C, and the die was closed. (VI) After maintaining this for 300 seconds, a pressure of 1 MPa was applied and maintained for an additional 60 seconds. (VII) After step (VI), the mold cavity was opened and metal spacers were inserted into the ends of the cavity to adjust the thickness of the porous body (a) to 5 mm. (VIII) After that, the mold cavity was clamped again, and the cavity temperature was cooled to 50°C while maintaining the pressure. (IX) The mold was opened and the porous body (a) was taken out.

[0058] (3) Thermoplastic resin (B) (PA6) Polyamide resin (manufactured by Toray Industries, Inc., nylon 6 resin "Amilan" (registered trademark) CM1001, glass transition point 40°C) was used. (PEI) polyetherimide resin (manufactured by Sabic, "ULTEM" (registered trademark) 1040, glass transition point 216°C) was used. (PEKK) polyether ketone ketone resin (manufactured by Arkema, "KEPSTAN" (registered trademark) 7003, glass transition point 160°C) was used.

[0059] (4) Resin compound (C) (Epoxy resin) Bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, "jER1003"). The melt viscosity at 350°C was less than 0.1 Pa·s. (Phenol resin) o-cresol novolak resin "Phenolite" (registered trademark) KA-1165 manufactured by DIC Corporation. The melting point was 125°C and the melt viscosity at 350°C was less than 0.1 Pa·s. (Terpene Resin) Terpene resin (manufactured by Yasuhara Chemical Co., Ltd., "Clearon M105 (trade name)". Acid value 0 mgKOH / g, melt viscosity at 350°C was not measurable due to low heat resistance and decomposition.

[0060] 3. Blade Preparation

[0061] Example 1 A long-fiber-reinforced resin pellet manufacturing apparatus was used, equipped with a coating die for wire coating attached to the tip of a TEX-30α twin-screw extruder (manufactured by The Japan Steel Works, Ltd.) (screw diameter: 30 mm, L / D = 32). The extruder cylinder temperature was set to 260°C, and the thermoplastic resin (PA6) described above was fed from the main hopper and melt-kneaded at a screw rotation speed of 200 rpm. The molten thermoplastic resin (PA6) was fed into the discharge die opening (diameter: 3 mm) and continuously arranged to coat the carbon fiber. At this time, at least a portion of the carbon fiber was in contact with the thermoplastic resin (PA6) in the internal cross section of the fiber bundle. The resulting strand was cooled and then cut with a cutter to a pellet length of 7 mm to obtain long-fiber pellets. The take-up speed was adjusted so that the carbon fiber was 30 parts by weight per 100 parts by weight of (A) and (B). The length of the carbon fiber in the obtained long-fiber pellets was substantially the same as the pellet length.

[0062] The long fiber pellets thus obtained were injection-molded using an injection molding machine (J450AD, manufactured by The Japan Steel Works, Ltd.) under the following conditions: injection time: 5 seconds, back pressure: 5 MPa, dwell pressure: 200 MPa, dwell time: 20 seconds, cylinder temperature: 270°C, and mold temperature: 80°C to produce a 600 mm x 100 mm x 5 mm blade. Here, the cylinder temperature refers to the temperature of the part of the injection molding machine where the molding material is heated and melted, and the mold temperature refers to the temperature of the mold into which the resin is injected to form the desired shape. The obtained blade was left to stand for 24 hours in a constant temperature and humidity chamber adjusted to a temperature of 23°C and 50% RH before being subjected to characteristic evaluation. The results of the blade evaluation using the above-mentioned methods are summarized in Table 1.

[0063] Example 2 Blades were produced in the same manner as in Example 1, except that the contents of the carbon fiber (A) and the thermoplastic resin (B) were changed as shown in Table 1. The evaluation results are shown in Table 1.

[0064] (Examples 3 and 4) Blades were produced in the same manner as in Example 1, except that the thermoplastic resin (B) was changed as shown in Table 1, and the cylinder temperature was set to 380°C and the mold temperature to 160°C. The evaluation results are shown in Table 1.

[0065] Example 5 A long-fiber-reinforced resin pellet manufacturing apparatus was used, equipped with a coating die for wire coating attached to the tip of a Japan Steel Works, Ltd. TEX-30α twin-screw extruder (screw diameter 30 mm, L / D = 32). The extruder cylinder temperature was set to 260°C, and the thermoplastic resin (PA6) described above was fed from the main hopper and melt-kneaded at a screw rotation speed of 200 rpm. The resin compound (epoxy resin) was heated and melted at 200°C. The discharge rate was adjusted to 7 parts by weight per 100 parts by weight of (A) and (B). This resin compound was then applied to a fiber bundle consisting of carbon fibers. The melted thermoplastic resin (PA6) was then fed into a die opening (diameter 3 mm) from which the thermoplastic resin (PA6) was discharged, and the carbon fibers were continuously coated. At this time, at least a portion of the carbon fibers was in contact with the thermoplastic resin (PA6) in the internal cross section of the fiber bundle. The resulting strand was cooled and then cut into 7 mm pellet lengths using a cutter to produce long-fiber pellets. At this time, the take-up speed was adjusted so that the carbon fiber was 30 parts by weight per 100 parts by weight of the total of (A) and (B). The length of the carbon fiber in the obtained long fiber pellets was substantially the same as the pellet length. Using the long fiber pellets thus obtained, a blade was produced by injection molding in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0066] Example 6 A blade was produced in the same manner as in Example 5, except that the resin compound (C) was changed as shown in Table 1. The evaluation results are shown in Table 1.

[0067] Example 7 A blade was produced in the same manner as in Example 5, except that the injection time during injection molding was changed to 0.5 seconds. The evaluation results are shown in Table 1.

[0068] Example 8 A blade was produced in the same manner as in Example 5, except that the injection time during injection molding was changed to 1 second. The evaluation results are shown in Table 1.

[0069] Example 9 A blade was produced in the same manner as in Example 5, except that the injection time during injection molding was changed to 10 seconds. The evaluation results are shown in Table 2.

[0070] Example 10 Using a blow molding machine (DAC50 manufactured by Placo Corporation), the long fiber pellets obtained in the same manner as in Example 5 were melt-kneaded at 260°C (screw compression ratio = 2.2), extruded into a parison, and after clamping the mold, the parison was subjected to a pressure of 5 kg / cm 2 After blowing air into the mold, the air pressure is increased to 1 kg / cm 2 After the pressure was reduced to 100kJ / min, and the blade was cooled sufficiently, the mold was opened and the blow-molded blade was removed. The obtained blade was left to stand in a constant temperature and humidity chamber adjusted to a temperature of 23°C and a relative humidity of 50% for 24 hours, after which its properties were evaluated. The evaluation results obtained using the above-mentioned methods are summarized in Table 2.

[0071] Example 11 The CFRP with continuous porous structure prepared as described above was precut into a length of 600 mm and a width of 100 mm and processed into a core material for insert molding. Next, using an injection molding machine (Japan Steel Works, Ltd. J450AD), the core material was positioned within an injection molding mold (cavity thickness: 5 mm) using a mechanical clamping mechanism. Insert molding was performed under the following conditions: injection time: 10 seconds, back pressure: 5 MPa, dwell pressure: 200 MPa, dwell time: 20 seconds, cylinder temperature: 270°C, mold temperature: 80°C, to produce a 600 mm x 100 mm x 5 mm blade. The evaluation results are summarized in Table 2.

[0072] Example 12 Blades were produced in the same manner as in Example 5, except that the thermoplastic resin (B) was changed as shown in Table 2, and the cylinder temperature was set to 380°C and the mold temperature to 160°C. The evaluation results are summarized in Table 2.

[0073] Example 13 Blades were produced in the same manner as in Example 10, except that the thermoplastic resin (B) was changed as shown in Table 2 and the melt-kneading temperature was set to 380° C. The evaluation results are shown in Table 2.

[0074] Example 14 Blades were produced in the same manner as in Example 11, except that the thermoplastic resin (B) was changed as shown in Table 2, and the cylinder temperature was set to 380°C and the mold temperature to 160°C. The evaluation results are summarized in Table 2.

[0075] (Comparative Example 1) A blade was produced in the same manner as in Example 1, except that the CFRTP composition was changed as shown in Table 2. The evaluation results are shown in Table 2.

[0076] (Comparative Example 2) Except for changing the molding back pressure during injection molding to 40 MPa, a blade was produced in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0077] [Table 1]

[0078] [Table 2]

Claims

1. A flying object blade, at least an outer peripheral wall surface of which is formed of a fiber reinforced resin containing carbon fiber (A) and a thermoplastic resin (B), In the fiber reinforced resin, when the total amount of the carbon fiber (A) and the thermoplastic resin (B) is taken as 100 parts by weight, the content of the carbon fiber (A) is 1 to 50 parts by weight, the content of the thermoplastic resin (B) is 50 to 99 parts by weight, and the weight average fiber length of the carbon fiber (A) is 300 to 2500 μm.

2. 2. The aeronautical vehicle blade according to claim 1, wherein the warpage rate in the blade thickness direction, calculated by the following formula (1), is less than 30% after 2,000 cycles of a heat cycle test, in which one cycle consists of heating at 80°C for 30 minutes and then cooling at -40°C for 30 minutes: Warpage rate in blade thickness direction (%)=(warpage amount after heat cycle test−warpage amount before heat cycle test) / warpage amount before heat cycle test×100 (1)

3. 2. The flying object blade according to claim 1, wherein the thermoplastic resin has a glass transition temperature of 30 to 250°C.

4. 2. The flying object blade according to claim 1, wherein the average surface roughness Ra of the outer peripheral wall surface is 0.1 to 3.0 μm.

5. 2. The flying object blade according to claim 1, wherein the fiber reinforced resin further contains 0.1 to 20 parts by weight of a resin compound (C) selected from epoxy resins and phenolic resins.

6. 6. The flying object blade according to claim 5, wherein the resin compound (C) has a melt viscosity at 350° C. of 0.01 to 0.5 Pa·s.

7. 2. The flying object blade according to claim 1, wherein the fiber reinforced resin contains 20 to 99% of the carbon fibers (A) having a fiber length of 300 to 10,000 μm.

8. 2. The flying object blade according to claim 1, wherein the flexural modulus in the blade length direction is 1.5 to 10 times the flexural modulus in the chord length direction.

9. 2. The flying object blade according to claim 1, wherein the air resistance coefficient Cd value in the axial shape connecting the leading edge and the trailing edge is 0.1 or more and less than 0.

4.

10. 2. The flying object blade according to claim 1, wherein the air resistance Fd value in the axial direction connecting the leading edge and the trailing edge is 1 to 10,000 N.

11. 2. The flying object blade according to claim 1, having a hollow portion or a core member, the outer peripheral wall of which is formed from said fiber reinforced resin.

12. 12. The flying object blade according to claim 11, wherein the thickness of the outer peripheral wall is 0.001 to 100 mm.

13. A flying object comprising the flying object blade according to any one of claims 1 to 12.

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