Fiber-reinforced resin molded article

Abstract

[Problem] The technical problem of the present invention is to provide a vibration-damping fiber-reinforced resin molded article having both excellent mechanical properties and vibration damping properties. [Solution] This fiber-reinforced resin molded article is provided with polyimide fibers and a resin. The fiber diameter of the polyimide fiber is in the range of from 10.0 [mu] m to 18.0 [mu] m (inclusive). The volume content of the polyimide fibers in the fiber-reinforced resin molded body is in the range of 40% to 70%. Furthermore, the loss coefficient of vibration attenuation at a natural vibration frequency of 6400 Hz or less in the fiber-reinforced resin molded article measured in an environment at a temperature of 23 DEG C is 0.005 or more.

Description

Technical Field

[0001] The present invention relates to a fiber-reinforced resin molded body having both excellent mechanical properties and vibration damping properties. Background Art

[0002] Fiber-reinforced composite resin materials in which reinforcing fibers are contained in resins are widely used in parts such as transportation machinery and household electronic equipment, and building parts. Generally, parts made of soft materials have high vibration damping properties. Therefore, if soft resins or resins containing rubber are used as resins, vibration damping properties can be improved. However, if such resins are used as resins, rigidity and strength are significantly reduced.

[0003] Therefore, in order to provide a fiber-reinforced resin molded body having good rigidity, strength, etc. while maintaining vibration damping properties, a fiber-reinforced resin molded body is proposed in which a resin such as an epoxy resin is reinforced with reinforcing fibers such as glass fibers and carbon fibers. Since such a fiber-reinforced resin molded body is light in weight and high in rigidity, and also excellent in strength, it is widely used in parts such as transportation machinery and household electronic equipment, and building parts, as well as in the sports goods, automobile industry, and aircraft industry.

[0004] In addition, recently, in order to make the touch and feel of tennis rackets and golf clubs good when hitting the ball, vibration reduction is required for tennis rackets and golf clubs. In addition, for the structural parts of rockets, not only higher strength is required, but also vibration reduction is required to suppress the resonance damage of electronic equipment during launch. For building materials such as walls and roofs, vibration control is also an important issue mainly from the perspective of sound insulation. In addition, vibration reduction is also an indispensable point of view to obtain earthquake-resistant structures. Moreover, in recent years, in order to utilize wind energy, although the use of fiber-reinforced resin molded bodies as windmill blades has been increasing, the noise caused by the vibration of windmill blades often becomes a problem, and vibration reduction is also required for windmill blades.

[0005] In addition, Patent Document 1 discloses a golf club shaft having a vibration damping layer woven from metal fibers in at least a portion of a fiber-reinforced resin shaft in a longitudinal direction. In addition, Patent Document 2 discloses a golf club shaft having one or more layers of polyester film between fiber-reinforced resin layers or on the inner surface of the innermost layer of the fiber-reinforced resin layer.

[0006] In addition, patent document 3 discloses a tennis racket made of a fiber-reinforced composite material, wherein the tennis racket uses an epoxy resin composition as a matrix resin, and the epoxy resin composition contains a specific epoxy resin, rubber particles incompatible with the epoxy resin, and polyvinyl formal. For the fiber-reinforced composite material, while the rubber particles incompatible with the epoxy resin enter the interior of the reinforcing fiber bundle, the reinforcing fiber allows a certain degree of rubber particles to be filtered, and more rubber components are present on the surface of the prepreg than inside the prepreg. That is, it is possible to have more rubber components between the layers of the prepreg after lamination. Compared with the case where a fiber-reinforced composite material is made by using rubber particles soluble in epoxy resin and in which the rubber component is uniformly present, the tennis racket shows higher vibration damping and excellent striking feel. However, for the fiber-reinforced composite material, rubber particles with a lower elastic modulus than the epoxy resin enter the interior of the reinforcing fiber bundle. Therefore, the elastic modulus of the matrix resin in the reinforcing fiber bundle is reduced, and the rigidity and strength of the tennis racket are reduced. Prior art literature Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-261473 Patent Document 2: Japanese Patent Application Publication No. 2008-237373 Patent Document 3: Japanese Patent Application Publication No. 2003-012889 Summary of the invention Technical problem to be solved by the invention

[0008] The present invention has been made in view of the above-mentioned problems in the background art, and a technical object of the present invention is to provide a vibration-damping fiber-reinforced resin molded body having both excellent mechanical properties and vibration-damping properties. Technical means to solve technical problems

[0009] The fiber-reinforced resin molded body of the first aspect of the present invention comprises polyimide fibers and resin. The fiber diameter of the polyimide fibers is in the range of 10.0 μm or more and 18.0 μm or less. The volume content of the polyimide fibers in the fiber-reinforced resin molded body is in the range of 40% or more and 70% or less. The loss coefficient of vibration attenuation is 0.005 or more, and the vibration attenuation is the vibration attenuation of the fiber-reinforced resin molded body at a natural vibration frequency of 6400 Hz or less at a measurement temperature of 23°C.

[0010] In the fiber-reinforced resin molded product according to the first aspect of the present invention, the tensile strength of the polyimide fiber is preferably within a range of 2.5 GPa to 3.5 GPa.

[0011] In the fiber-reinforced resin molded product according to the first aspect of the present invention, the polyimide fiber preferably has a tensile modulus in the range of 100 GPa to 170 GPa.

[0012] A product according to a second aspect of the present invention includes the above-mentioned fiber-reinforced resin molded body.

[0013] In addition, the product of the second aspect of the present invention is preferably selected from the group consisting of transportation equipment, audio / visual equipment, industrial equipment, air conditioning equipment, automotive equipment, building structural materials, wind blades, unmanned equipment, sports equipment and welfare equipment. The above-mentioned sports equipment is preferably selected from the group consisting of golf clubs, skis, snowboards, tennis rackets, badminton rackets, squash rackets, ice hockey sticks and sports bicycles. In addition, the above-mentioned unmanned equipment is preferably selected from the group consisting of robotic arms, drones and radio remote control equipment.

[0014] The prepreg of the third aspect of the present invention is used to manufacture the above-mentioned fiber-reinforced resin molded body. Moreover, the prepreg comprises polyimide fibers and a resin or a resin precursor. In addition, the "resin precursor" recorded here refers to a monomer composition before curing (including a crosslinking agent, etc.), a polymer precursor, etc. Beneficial Effects

[0015] Compared with conventional carbon fiber reinforced resin molded bodies and glass fiber reinforced resin molded bodies, the fiber reinforced resin molded body of the present invention not only has improved vibration attenuation characteristics and excellent vibration damping properties, but also has sufficient mechanical properties by containing a specific amount of polyimide fibers. The fiber reinforced resin molded body of the present invention has high vibration attenuation properties and can improve vibration damping properties without reducing rigidity and strength. Therefore, it is useful for reducing vibration of transportation equipment, high vibration attenuation of audio equipment, improving the hitting feel of golf clubs, improving the impact absorption of tennis rackets, improving the bite sensitivity of fishing rods, improving the earthquake resistance of buildings, and suppressing resonance damage of electronic machinery. DETAILED DESCRIPTION

[0016] <Configuration of Fiber-Reinforced Resin Molded Article According to Embodiment of the Invention> The fiber-reinforced resin molded body according to the embodiment of the present invention is mainly composed of polyimide fibers and resin.

[0017] The polyimide fiber is preferably obtained by polymerization reaction of aromatic tetracarboxylic dianhydride and aromatic diamine. The aromatic tetracarboxylic dianhydride is preferably at least one of pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride. The aromatic diamine is preferably at least one of 4,4'-diaminodiphenyl ether and p-phenylenediamine.

[0018] In addition, the polyimide fiber can be a long fiber or a short fiber cut into any length. In addition, from the viewpoint of maintaining the mechanical strength of the obtained fiber-reinforced resin molded body high, the polyimide fiber has a fiber diameter in the range of 10.0 μm or more and 18.0 μm or less. In addition, the tensile strength of the polyimide fiber is in the range of 2.5 GPa or more and 3.5 GPa or less, thereby maintaining the mechanical strength high. In addition, the tensile strength of the polyimide fiber is more preferably in the range of 3.0 GPa or more and 3.5 GPa or less. In addition, the tensile modulus of the polyimide fiber is in the range of 100 GPa or more and 170 GPa or less, thereby, the vibration damping characteristics of the fiber-reinforced resin molded body can be maintained high. In addition, the tensile modulus of the polyimide fiber is more preferably in the range of 100 GPa or more and 150 GPa or less.

[0019] The volume content of the polyimide fiber in the fiber-reinforced resin molded body according to the embodiment of the present invention is within the range of 40% to 70%, thereby achieving high vibration damping properties and maintaining high mechanical strength. The volume content of the polyimide fiber is more preferably within the range of 40% to 65%, and further preferably within the range of 45% to 65%.

[0020] As the above-mentioned resin, a thermosetting resin is preferred. Examples of the thermosetting resin include epoxy resin, unsaturated polyester resin, phenolic resin, vinyl ester resin, polyurethane resin, diallyl phthalate resin, bismaleimide triazine resin, cyanate ester resin, polyphenylene ether resin, polyimide resin, silicone resin, etc. In addition, the thermosetting resin may also be a copolymer, a modified product, or a resin mixed with two or more resins. On the other hand, the above-mentioned resin may also be a thermoplastic resin. Examples of the thermoplastic resin include polyethylene resin, polypropylene resin, polybutene resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polypropylene terephthalate resin, polyethylene naphthalate resin, polyarylate resin, polystyrene resin, polyvinyl alcohol resin, polyphenylene oxide resin, polyphenylene ether resin, polyamide resin, polyoxymethylene resin, polycarbonate resin, polyurethane resin, polyvinyl chloride resin, polyacrylate resin, polyphenylene sulfide resin, polysulfone resin, polyethersulfone resin, polyacrylic acid resin, polyketone resin, polyetheretherketone resin, polyimide resin, polyetherimide resin, acrylonitrile-butadiene-styrene resin, polyamideimide resin, fluorine-based resin, the above-mentioned elastomer resin, etc. In addition, the thermoplastic resin may also be a copolymer, a modified product, or a resin mixed with two or more resins. Among the above-mentioned resins, from the viewpoint of a good balance of adhesiveness, epoxy resin and polyimide resin are more preferred. In addition, within the scope not damaging the gist of the present invention, functional agents such as flame retardants, light stabilizers, ultraviolet absorbers, smoothing agents, antistatic agents, antioxidants, mold release agents, plasticizers, colorants, antibacterial agents, pigments, conductive agents, silane coupling agents, inorganic coating agents, etc. may be added to the resin.

[0021] Examples of the above-mentioned epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, bisphenol A novolac type epoxy resin, cresol novolac type epoxy resin, diaminodiphenylmethane type epoxy resin, and epoxy resins flame-retarded by halogenating a part of the hydrogen atoms in these epoxy resin structures, etc. In addition, examples of the curing agent for this epoxy resin include amide-based curing agents such as dicyandiamide and aliphatic polyamide, amine-based curing agents such as diaminodiphenylmethane and triethylenediamine, phenol-based curing agents such as phenol novolac resin and bisphenol A novolac resin, acid anhydride-based compounds, thiol-based compounds, phenolic resin, amino resin types, etc.

[0022] In addition, as the above-mentioned polyimide resin, for example, a polyimide resin composed of an aromatic tetracarboxylic dianhydride and an aromatic diamine can be mentioned. As the aromatic tetracarboxylic dianhydride, pyromellitic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,3,3 ',4'-Benzophenonetetracarboxylic dianhydride, 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA), bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 2,2-bis[3,4-(dicarboxyphenoxy)phenyl ] propane dianhydride (BPADA), 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, oxydiphthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl) sulfone dianhydride, bis(3,4-dicarboxyphenyl) sulfoxide dianhydride, thiodiphthalic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl) Aromatic tetracarboxylic dianhydrides such as 9,9-bis[4-(3,4'-dicarboxyphenoxy)phenyl]fluorene dianhydride, cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 2,3,4,5-tetrahydrofuran tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, 3,4-dicarboxy-1-cyclohexyl succinic dianhydride, and 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride.Examples of the aromatic diamine include 4,4'-diaminodiphenyl ether, p-phenylenediamine (PPD), m-phenylenediamine (MPDA), 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 2,2-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane (MDA), 2,2-bis-(4-aminophenyl)propane, 3,3'-diaminodiphenyl sulfone (33DDS), 4,4'-diaminodiphenyl sulfone (44DDS), 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl 1,4-bis(4-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]sulfone (BAPSM), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2-bis(3-aminophenyl)1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)1,1,1,3,3,3-hexafluoropropane, 9,9-bis(4-aminophenyl)fluorene, etc.

[0023] The loss coefficient of vibration attenuation of the fiber-reinforced resin molded body according to the embodiment of the present invention is preferably 0.005 or more, more preferably in the range of 0.005 or more and 0.050 or less, and further preferably in the range of 0.006 or more and 0.050 or less, wherein the vibration attenuation is vibration attenuation at a natural vibration frequency of 6400 Hz or less at a measurement temperature of 23° C. In addition, the natural vibration frequency at a measurement temperature of 23° C. may be 5200 Hz or less, 5150 Hz or less, 5100 Hz or less, 5050 Hz or less, 5000 Hz or less, or 4950 Hz or less.

[0024] Furthermore, for the fiber-reinforced resin molded body of the embodiment of the present invention, for example, if all the fiber directions are in the same direction, the tensile strength in the fiber direction (the length direction of the fiber) is preferably in the range of 0.5 GPa to 2.1 GPa. Such a fiber-reinforced resin molded body, when used as a building material, not only shows earthquake resistance, but also shows light weight and high strength.

[0025] The fiber-reinforced resin molded body of the embodiment of the present invention can be applied to products and parts thereof that require vibration damping. As such products, for example, transportation equipment, audio / visual equipment, industrial equipment, air conditioning equipment, automotive equipment, building structural materials, wind turbines, unmanned equipment, sports equipment, welfare equipment, etc. can be cited. As parts, for example, blades of wind turbines can be cited. In addition, here, as sports equipment, for example, golf clubs, skis, snowboards, tennis rackets, badminton rackets, squash rackets, ice hockey sticks, sports bicycles, etc. can be cited. In addition, for golf clubs, the fiber-reinforced resin molded body of the embodiment of the present invention can be applied to golf club shafts (golfshafts) as its parts. For sports bicycles, the fiber-reinforced resin molded body of the embodiment of the present invention can be applied to frames as its parts. In addition, as unmanned equipment, for example, robotic arms, drones, radio remote control equipment, etc. can be cited. In addition, in these unmanned equipment, the fiber-reinforced resin molded body of the embodiment of the present invention can be applied to the frame or the like as its component. In addition, as welfare tools, for example, prostheses, crutches, wheelchairs, etc. can be cited. In addition, for these wheelchairs, the fiber-reinforced resin molded body of the embodiment of the present invention can be applied to the frame or the like as its component.

[0026] <Method for Manufacturing Fiber-Reinforced Resin Molded Article According to Embodiment of the Present Invention> The fiber-reinforced resin molding of the embodiment of the present invention can be performed by a known method. Examples of the method include: a hand-stack method, a resin injection method, a pressing method and an injection molding method using BMC materials and SMC materials, a continuous pultrusion method, an autoclave molding method, and the like. In addition, these methods can be selected according to the target shape and the type of the matrix resin (e.g., a thermosetting resin, a thermoplastic resin, etc.), and the autoclave molding method is particularly preferred among the above methods.

[0027] For example, in the case of using a unidirectionally arranged prepreg sheet (hereinafter referred to as "UD prepreg") to manufacture a fiber-reinforced resin molded body, the fiber-reinforced resin molded body can be manufactured by the following method. First, after mixing a thermosetting resin and a curing agent to obtain a mixture, the polyimide fiber is wound on a cylindrical winding machine pre-wound with a first release paper in a manner to obtain a desired unit area weight (the first release paper is coated with the mixture and pre-wound on the cylindrical winding machine with the coating surface of the mixture facing the upper side), and then the second release paper coated with the above-mentioned mixture is further attached from above with the coating surface of the mixture facing the lower side. Then, it is heated and dried to an intermediate cured state to manufacture a UD prepreg. In addition, the manufacturing method of the UD prepreg may also be, for example, (a) a fiber winding method, (b) an impregnation method in which a resin is impregnated into a fiber substrate and then heated and dried, (c) a hot melt method in which fibers are heated and pressurized (the fibers are arranged on a sheet coated with a resin), etc. In addition, when manufacturing a unidirectional prepreg sheet, reinforcing fibers other than polyimide fibers may be mixed with the polyimide fibers. Finally, the UD prepreg is stacked according to the design according to the application, and the stack is heated and pressurized under vacuum to manufacture a fiber-reinforced resin molded body.

[0028] <Examples and Comparative Examples> Hereinafter, although an Example and a comparative example are demonstrated concretely, this invention is not limited to these Examples. Example 1

[0029] 1. Preparation of polyimide fiber 136g of p-phenylenediamine (PPD) and 2224g of N-methylpyrrolidone were put into a reaction container to dissolve PPD in N-methylpyrrolidone. Then, 259.0g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 82.30g of pyromellitic dianhydride (PMDA) were put into the above-mentioned reaction container, and PMDA and PPD were polymerized at room temperature. As a result, a polyimide precursor solution with a concentration of 17.7% by mass was obtained. Then, a solution in which 21.41g of 1,3-oxadiazole was dissolved in 40.41g of N-methylpyrrolidone was added to the polyimide precursor solution to prepare a polyimide precursor solution for spinning. Then, using a spinning ejector, the spinning polyimide precursor solution was ejected into a coagulation bath containing water as the main component to obtain a polyimide precursor fiber. Next, the polyimide precursor fiber is washed with water, stretched, and heated to obtain a polyimide fiber.

[0030] The fiber diameter and tensile properties of the obtained polyimide fibers were measured by the following methods.

[0031] (1) Fiber diameter The fineness of the polyimide fiber obtained as described above was measured using an automatic vibration fineness meter DC21 manufactured by Sachi Co., Ltd. The fiber diameter of the polyimide fiber was calculated from the measured fineness and the specific gravity of the polyimide fiber and found to be 14 μm.

[0032] (2) Tensile properties The tensile modulus (cN / dtex) and tensile strength (cN / dtex) of the polyimide fiber obtained as described above were measured according to the method of "JISR7607". Then, the tensile modulus (GPa) of the polyimide fiber was calculated according to the conversion formula of elastic modulus (cN / dtex) × specific gravity ÷ 10. On the other hand, the tensile strength (GPa) of the polyimide fiber was calculated according to the conversion formula of strength (cN / dtex) × specific gravity ÷ 10. As a result, the tensile modulus of the polyimide fiber was 137 GPa and the tensile strength was 3.1 GPa.

[0033] 2. Fabrication of fiber-reinforced resin molded bodies The polyimide fiber obtained as described above was made to have a fiber unit area weight of 116 g / m 2 After being arranged in a specific direction in a manner, an epoxy resin composition obtained by mixing 100 parts by mass of an epoxy main agent (JER828 manufactured by Mitsubishi Chemikaru Co., Ltd.) and 8 parts by mass of a curing agent (ADEKA Hardener EH-3636AS manufactured by ADEKA Co., Ltd.) is impregnated into the arranged polyimide fiber, and the polyimide fiber impregnated with the composition is heated at 120°C for 30 minutes in a constant temperature bath to prepare a UD prepreg. Next, after 15 sheets of the obtained UD prepreg are stacked in a manner that aligns the fiber direction, the stack is clamped in a plate-shaped mold for vacuum bag molding, and the stack is heated and pressurized at 130°C at 6 atmospheres in an autoclave for 90 minutes to obtain a fiber-reinforced resin molded body. In addition, at this time, the heating and cooling rate of the autoclave is 2°C / minute. The thickness of the obtained fiber-reinforced resin molded body is 1.93 mm, and the volume content of the polyimide fiber is 60%.

[0034] In addition, the volume content Vf of the polyimide fiber was determined by the following formula (1). Vf=Faw×N / ρ / T / 10···(1) Here, Faw is the weight per unit area of ​​the polyimide fiber (g / m 2 ), N is the number of UD prepreg layers, ρ is the density of polyimide fiber (g / cm 3 ), T is the thickness of the fiber-reinforced resin molded body (mm). Here, the density of the polyimide fiber is 1.5 g / cm 3 .

[0035] The loss factor of vibration attenuation and tensile properties of the obtained fiber-reinforced resin molded product were measured by the following methods.

[0036] (1) Determination of loss coefficient of vibration attenuation The loss factor of vibration attenuation of the fiber-reinforced resin molded body was measured by loss factor measurement (central vibration method) using a method in accordance with JIS K7391. More specifically, the loss factor of the fiber-reinforced resin molded body at the natural vibration frequency (frequency) was measured using a PULSE analyzer manufactured by Burroughs Kea (hardware: LAN-XI, software: PULSE Labshop, MS18143), with the measurement temperature set to 23°C and the measurement upper limit frequency set to 6400 Hz.

[0037] The results are that the loss coefficient of vibration attenuation at the natural vibration frequency (frequency) of 156 Hz is 0.00747, the loss coefficient of vibration attenuation at the natural vibration frequency (frequency) of 953 Hz is 0.00910, the loss coefficient of vibration attenuation at the natural vibration frequency (frequency) of 2598 Hz is 0.00933, and the loss coefficient of vibration attenuation at the natural vibration frequency (frequency) of 4930 Hz is 0.00959.

[0038] (2) Tensile properties The obtained fiber-reinforced resin molded body was subjected to a tensile test using a universal material testing machine (manufactured by Shimadzu Corporation, AG-50kNXplus) in accordance with the method of ASTM-D3039. As a result, the tensile strength of the fiber-reinforced resin molded body in the fiber direction (the longitudinal direction of the fiber) was 1.55 GPa, and the tensile elastic modulus was 44.8 GPa. Example 2

[0039] The polyimide fiber obtained in Example 1 was made to have a fiber unit weight of 117 g / m 2After the fibers are arranged in a specific direction in a manner, an epoxy resin composition prepared by mixing 100 parts by mass of an epoxy main agent (JER828 manufactured by Mitsubishi Chemikaru Co., Ltd.) and 25 parts by mass of a curing agent (JER キュアW manufactured by Mitsubishi Chemikaru Co., Ltd.) is impregnated into the arranged polyimide fibers, and the polyimide fibers impregnated with the composition are heated at 150°C for 15 minutes in a constant temperature bath to prepare a UD prepreg. Next, 15 sheets of the obtained UD prepreg are stacked in a manner that aligns the fiber directions, and the stack is clamped in a plate-shaped mold for vacuum bag molding, and the stack is heated and pressurized at 175°C and 10 atmospheres for 4 hours using a small test press (manufactured by Toyo Seiki Seisakusho, MINI TESTPRESS-10) to obtain a fiber-reinforced resin molded body. The obtained fiber-reinforced resin molded body had a thickness of 1.93 mm and a volume content of the polyimide fibers of 61%.

[0040] The loss factor of vibration attenuation of the fiber-reinforced resin molded body obtained as described above was measured by the same method as that shown in Example 1. The loss factor of vibration attenuation at a natural vibration frequency (frequency) of 162 Hz was 0.00665, the loss factor of vibration attenuation at a natural vibration frequency (frequency) of 1003 Hz was 0.00825, the loss factor of vibration attenuation at a natural vibration frequency (frequency) of 2736 Hz was 0.01022, and the loss factor of vibration attenuation at a natural vibration frequency (frequency) of 5141 Hz was 0.01248. In addition, the tensile properties of the fiber-reinforced resin molded body were measured by the same method as that shown in Example 1. The tensile elastic modulus was 1.58 GPa and the tensile strength was 45.5 GPa.

[0041] (Comparative Example 1) A fiber-reinforced resin molded body was obtained by the same method as in Example 2 except that the polyimide fiber was replaced with glass fiber (ECG150 1 / 0 manufactured by Nitto Bosei Co., Ltd.). The thickness of the obtained fiber-reinforced resin molded body was 1.94 mm, and the volume content of the glass fiber was 61%. In addition, the loss coefficient of vibration attenuation and tensile properties of the fiber-reinforced resin molded body were measured by the same method as in Example 1. As a result, the loss coefficient of vibration attenuation at a natural vibration frequency (frequency) of 93 Hz was 0.00228, the loss coefficient of vibration attenuation at a natural vibration frequency (frequency) of 583 Hz was 0.00252, the loss coefficient of vibration attenuation at a natural vibration frequency (frequency) of 1623 Hz was 0.00328, the elastic loss coefficient of vibration attenuation at a natural vibration frequency (frequency) of 3158 Hz was 0.00461, the tensile strength was 1.56 GPa, and the tensile elastic modulus was 36.6 GPa.

[0042] (Comparative Example 2) Twelve sheets of unidirectional carbon fiber prepreg (P3252S-17 manufactured by Toray Industries, Inc.) were stacked, and the stack was heated and pressed in the same manner as in Example 1 to obtain a fiber-reinforced resin molded body. The obtained fiber-reinforced resin molded body had a thickness of 1.93 mm and a volume content of carbon fibers of 60%. In addition, the loss coefficient of vibration attenuation and tensile properties of the fiber-reinforced resin molded body were measured by the same method as shown in Example 1. The results showed that the loss coefficient of vibration attenuation at a natural vibration frequency (frequency) of 174 Hz was 0.00108, the loss coefficient of vibration attenuation at a natural vibration frequency (frequency) of 1087 Hz was 0.00082, the loss coefficient of vibration attenuation at a natural vibration frequency (frequency) of 3005 Hz was 0.00148, the loss coefficient of vibration attenuation at a natural vibration frequency (frequency) of 5778 Hz was 0.00257, the tensile strength was 2.4 GPa, and the tensile elastic modulus was 110.4 GPa.

[0043] The present invention is not limited to the above-mentioned modes and embodiments. The fiber-reinforced resin molded body of the present invention exhibits excellent vibration damping characteristics and can be applied to products selected from the group consisting of transportation equipment, audio / visual equipment, industrial equipment, air conditioning equipment, automotive equipment, building structural materials, wind blades, unmanned equipment, sports equipment, and welfare equipment. In addition, the present invention can be appropriately modified within the scope of the present invention.

Claims

1. A fiber-reinforced resin molded body, wherein: The fiber-reinforced resin molded body comprises polyimide fibers and resin. The fiber diameter of the polyimide fiber is 10.0 μm or more and 18.0 μm or less. The volume content of the polyimide fiber is 40% or more and 70% or less, The loss coefficient of vibration attenuation at a natural frequency of 6400 Hz or less at a measurement temperature of 23° C. is 0.005 or more.

2. The fiber-reinforced resin molded body according to claim 1, wherein The polyimide fiber has a tensile strength in the range of 2.5 GPa to 3.5 GPa.

3. The fiber-reinforced resin molded article according to claim 1, wherein The polyimide fiber has a tensile elastic modulus in a range of 100 GPa to 170 GPa. 4 . A product comprising the fiber-reinforced resin molded article according to claim 1 .

5. The product according to claim 4, wherein: The product is selected from the group consisting of transportation equipment, audio / visual equipment, industrial equipment, air conditioning equipment, automotive equipment, building structural materials, wind blades, unmanned equipment, sports equipment and welfare equipment.

6. The product of claim 5, wherein: The sporting goods are selected from the group consisting of golf clubs, skis, snowboards, tennis rackets, badminton rackets, squash rackets, ice hockey sticks and sports bicycles.

7. The product of claim 5, wherein: The unmanned equipment is selected from the group consisting of a robotic arm, a drone and a radio remote control device.

8. A prepreg, wherein: The prepreg is a prepreg for producing the fiber-reinforced resin molded body according to any one of claims 1 to 3, and includes polyimide fibers and a resin or a resin precursor.