Method for manufacturing a fiber-reinforced resin article and fiber-reinforced resin article

Abstract

This invention provides an advantageous improvement to a method for manufacturing fiber-reinforced resin articles having at least a hollow structure. The method for manufacturing fiber-reinforced resin articles of this invention includes the following steps: a molding step in which a prepreg preform having a core inner portion having a fusible core made of wax material disposed on its inner side is placed in a stamping die and heated to obtain a cured product having a hollow structure; and a core removal step in which the fusible core is removed from the cured product. In the core inner portion, a through-hole is formed in the prepreg preform, and an elastomeric plug is inserted into the through-hole.

Description

Technical Field

[0001] This invention relates to a method for manufacturing fiber-reinforced resin articles and the fiber-reinforced resin articles themselves.

[0002] This application asserts priority based on international application PCT / JP2021 / 011690 filed on March 22, 2021, with the Japan Patent Office, which is the official receiving office, and Japanese Patent Application No. 2021-069189 filed on April 15, 2021, with the Japan Patent Office, the contents of which are incorporated herein by reference. Background Technology

[0003] Fiber-reinforced plastic (FRP) is used in a variety of applications, including automotive reinforcement components.

[0004] A method for manufacturing fiber-reinforced resin articles with hollow structures is proposed by heating and curing a prepreg preform together with a core made of wax material in a stamping die.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2018 / 079824 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The object of the present invention is to provide an advantageous improvement to a method for manufacturing at least a portion of a fiber-reinforced resin article having a hollow structure by heating and curing a prepreg preform together with a core made of wax material in a stamping die.

[0010] The object of the present invention includes providing a method useful for preventing the expansion and deformation of hollow structural parts after the forming process is completed and the stamping die is opened.

[0011] Problems solved by various embodiments of the present invention are sometimes explicitly or implicitly disclosed in this specification.

[0012] Methods for solving problems

[0013] In one aspect of the present invention, a manufacturing method is provided, which is a fiber-reinforced resin manufacturing method having the following steps: a molding step in which a prepreg preform having a core inner portion having a fusible core made of wax material disposed on its inner side is placed in a stamping die and heated to obtain a cured product having a hollow structure; and a core removal step in which the fusible core is removed from the cured product, a through hole is formed in the core inner portion of the prepreg preform, and an elastomer plug is inserted into the through hole.

[0014] In another aspect of the present invention, a manufacturing method is provided, which is a fiber-reinforced resin manufacturing method having the following steps: a molding step in which a prepreg preform having a core inner portion having a fusible core made of wax material disposed on its inner side is disposed in a stamping die and heated to obtain a cured product having a hollow structure; and a core removal step in which the fusible core is removed from the cured product, and a first through hole and a second through hole are formed in the core inner portion of the prepreg preform, a first elastomeric plug is inserted into the first through hole, and a second elastomeric plug is inserted into the second through hole.

[0015] In another aspect of the invention, a fiber-reinforced resin article is provided having a hollow structure, a cavity formed in the hollow structure, a through hole extending from the interior space of the cavity to the outside, and an elastomeric plug blocking the through hole.

[0016] Invention Effects

[0017] An advantageous improvement is provided regarding a method for manufacturing at least a portion of a fiber-reinforced resin article having a hollow structure by configuring a prepreg preform together with a core made of wax material in a stamping die and allowing it to cure. Attached Figure Description

[0018] [ Figure 1 ] Figure 1 This is a flowchart of a method for manufacturing fiber-reinforced resin articles according to the embodiments.

[0019] [ Figure 2 ] Figure 2 It is a schematic three-dimensional representation of a fiber-reinforced resin article.

[0020] [ Figure 3 ] Figure 3 It is a schematic cross-sectional view of a fiber-reinforced resin article.

[0021] [ Figure 4 ] Figure 4 This is a cross-sectional view of a fusible core.

[0022] [ Figure 5 ] Figure 5 This is a cross-sectional view of a prepreg preform manufactured in a manner in which a core is configured inside.

[0023] [ Figure 6 ] Figure 6 It is a cross-sectional view showing an elastomer plug inserted into a through hole in a prepreg preform manufactured in a manner in which a core is configured inside.

[0024] [ Figure 7 ] Figure 7 It is a cross-sectional view showing the situation where the prepreg preform and the fusible core are put into the mold together.

[0025] [ Figure 8 ] Figure 8 It is a cross-sectional view showing the situation where the prepreg preform and the fusible core are put into the mold together.

[0026] [ Figure 9 ] Figure 9 This describes a situation where one end of a metal tube is inserted through an elastomer plug, allowing wax to be discharged from the hollow structure of a fiber-reinforced resin article into a recycling container.

[0027] [ Figure 10 ] Figure 10 This refers to a situation where air flows into the cavity of the hollow structure of a fiber-reinforced resin article through a metal tube that passes through one of the elastomer plugs, while wax is discharged from the cavity into a recycling container through another metal tube that passes through the other elastomer plug.

[0028] [ Figure 11 ] Figure 11 It is a cross-sectional view showing the structure of a partially fusible core. Detailed Implementation

[0029] 1. Manufacturing method of fiber-reinforced resin articles

[0030] One embodiment of the present invention relates to a method for manufacturing fiber-reinforced resin articles (hereinafter also referred to as FRP articles).

[0031] The FRP article manufacturing method involved in the implementation method is as follows: Figure 1 As shown in the process flow diagram, it consists of the following two steps.

[0032] (i) In the forming process, a prepreg preform with a core inner lining containing a fusible core made of wax material disposed on the inside is placed in a stamping die and heated to obtain a cured material with a hollow structure.

[0033] (ii) Core removal process, in which the fusible core is removed from the solidified material.

[0034] The following is a reference to the appendix. Figure 1 The method for manufacturing FRP articles involved in the implementation method is described in detail below.

[0035] 1.1. Forming process

[0036] The forming process is a process in which a prepreg preform with a fusible core made of wax material arranged inside a stamping die is placed and heated to obtain a cured product.

[0037] (Prepreg Preform)

[0038] Prepreg preforms are made in advance outside of a stamping die, using prepreg sheets, tow prepregs, or other prepreg materials as the main material, in a manner that results in a near-net shape.

[0039] When using prepreg sheets, two or more prepreg sheets may be stacked on part or all of the prepreg preform. The portion with multiple stacked prepreg sheets may contain two or more prepreg sheets of the same type, or it may contain two or more different types of prepreg sheets; both are acceptable.

[0040] Prepreg preforms using prepreg sheets can also have portions reinforced by towed prepreg.

[0041] Prepreg preforms can be formed partly or entirely from towed prepregs.

[0042] The fiber reinforcement materials used in prepregs are a variety of types, including continuous fibers, chopped fibers, fabrics, nonwovens, and non-crimped fabrics.

[0043] Prepreg sheets with multiple parallel, continuous fiber bundles as fiber reinforcement are called unidirectional prepregs (UD prepregs).

[0044] Prepreg sheets that use fabrics composed of continuous fiber bundles as fiber reinforcement materials are called cross-prepregs.

[0045] Prepreg sheets that use pads formed by stacking short fiber bundles as fiber reinforcement materials are called SMC (sheet molding compound).

[0046] Towed prepreg is a prepreg that uses a single continuous bundle of fibers as a reinforcing material.

[0047] Examples of fibers used in fiber-reinforced materials include carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, and metal fiber. Sometimes, two or more fibers are used in combination.

[0048] Thermosetting resins used in prepregs include, for example, epoxy resins, urea resins, vinyl ester resins (also known as epoxy acrylate resins), unsaturated polyesters, polyurethanes, and phenolic resins. Two or more thermosetting resins can also be mixed.

[0049] The content of the thermosetting resin composition in the prepreg is not limited, but may be, for example, 15-60% by mass. This content can be 15-20% by mass, 20-25% by mass, 25-40% by mass, 40-50% by mass, 50-60% by mass, etc.

[0050] Various additives can be added to thermosetting resin compositions. These include reactive diluents, flame retardants, defoamers, degassing agents, mold release agents, particulate fillers, colorants, silane coupling agents, etc.

[0051] The prepreg preform is manufactured such that a fusible core is positioned at the location corresponding to the voids formed in the hollow structure of the FRP article to be manufactured. In other words, a prepreg preform is manufactured such that, after curing, the hollow structure portion has a core-encasing portion with a fusible core positioned inside.

[0052] For example, in manufacturing such as Figure 2 and Figure 3 In the case of a hollow FRP article 1 with a square upper and lower surface and four rectangular sides, a prepreg preform is made according to the steps described below.

[0053] First, such as Figure 4 As shown, a fusible core 10 is prepared that has approximately the same shape and size as the cavity inside the FRP article 1.

[0054] The fusible core is formed of wax material, which allows it to be melted and removed as a whole during a core removal process after the molding process.

[0055] Details about the wax material will be discussed later.

[0056] Next, as Figure 5 As shown, a prepreg preform 20 with a substantially near-net-shape is formed by arranging prepreg sheets around the fusible core 10. In this example, the prepreg preform 20 as a whole corresponds to the core inner portion.

[0057] When manufacturing the prepreg preform 20, a through hole H with an inner diameter of less than 10 mm is preferably formed in advance on a portion of the prepreg sheet used for the material.

[0058] Finally, as Figure 6 As shown, the elastomer plug P is inserted from the outside into the through hole H formed in the prepreg sheet.

[0059] A gap may also remain between the through hole H and the elastomer plug P. This gap is blocked by the flow deformation of the prepreg sheet during the curing of the prepreg preform 20.

[0060] The elastomer plug P is tapered in the direction opposite to the insertion direction into the through hole H. That is, the side of the elastomer plug P with the larger cross-sectional area orthogonal to the insertion direction is inserted into the through hole H with the fusible core 10 facing towards it. The reason for this is to prevent the elastomer plug P from falling off due to the pressure inside the cavity after the molding process and before the wax is discharged.

[0061] In one example, to prevent detachment after the molding process, in addition to making the elastomer plug conical as described above, or alternatively, protrusions or depressions may be provided on the side of the elastomer plug.

[0062] The material of the elastomeric plug is not limited; for example, it can be acrylic rubber, fluororubber, silicone rubber, nitrile rubber, or butyl rubber.

[0063] (Curing)

[0064] In this specification, the temperature of the stamping die used to solidify the prepreg is referred to as the forming temperature.

[0065] The molding temperature is any temperature that allows the prepreg preform to cure in less than 1 hour, more preferably less than 40 minutes, and even more preferably less than 20 minutes.

[0066] The molding temperature is, for example, above 100°C, above 120°C, and even above 130°C. The higher the molding temperature, the shorter the curing time required for the prepreg preform.

[0067] If the forming temperature exceeds 160°C, the options for wax materials become narrower. From the viewpoint of reducing the time required to heat the stamping die and reducing energy consumption, the forming temperature can be below 150°C, and further below 140°C.

[0068] The temperature of the stamping die is maintained at the forming temperature by the temperature control mechanism typically provided in the stamping machine before the prepreg is fed into the machine.

[0069] Figure 7 express Figure 6 The example shown is the case where the prepreg preform 20 is inserted into the stamping die 100 consisting of the lower die 102 and the upper die 104.

[0070] Since the stamping die 100 is pre-set to the forming temperature, the temperature rise and accompanying expansion of the fusible core 10 begin immediately after it is fed into the stamping die 100 along with the prepreg preform 20. At this time, it is not necessary to soften or melt the wax material in the fusible core 10.

[0071] The prepreg preform 20 is pressed against the inner surface of the stamping die 100 by the expansion of the fusible core 10. In other words, the pressure generated within the stamping die 100 is applied to the prepreg preform 20 by the expansion of the fusible core 10 against the clamping force.

[0072] The higher the pressure, the fewer the FRP voids formed by the curing of the prepreg.

[0073] In one example, such as Figure 8 As shown, the stamping die 100 used in the forming process may also have a cavity formed by the lower die 102, the upper die 104 and the sliding core 106.

[0074] The movement of the sliding core 106 is controlled by a pressure control mechanism (not shown) using hydraulic pressure or similar methods. Even if the fusible core 10 expands, the sliding core 106 will not move until the pressure inside the die reaches a predetermined value. If the pressure inside the stamping die 100 exceeds the predetermined value, the sliding core 106 moves horizontally to alleviate the pressure. Using this stamping die to manage the forming pressure within a certain range is suitable for stabilizing the quality of FRP articles.

[0075] Here, the wax material is explained as follows.

[0076] Because wax materials expand significantly when softened or melted, it is preferable to soften or melt the wax material during the molding process when high pressure is required to be applied to the prepreg preform. In this case, the expansion accompanying the softening of the wax material needs to begin before the prepreg preform loses its plasticity due to curing.

[0077] One way to accelerate the softening of wax materials is to lower the softening temperature.

[0078] Another method to accelerate the softening of wax materials is to preheat the fusible core to near the softening temperature of the wax material before it is placed into the stamping die. Preheating the fusible core can be achieved simply by placing each prepreg preform into an oven.

[0079] These two methods can be used simultaneously.

[0080] The time from when the wax material begins to soften until it melts and becomes a highly fluid liquid is preferably longer. When this time is sufficiently long, the melted wax material will not flow into the gap between the prepreg and the stamping die because the prepreg solidifies before the wax material melts.

[0081] Considering the long time required for softening to melting, polyolefin waxes are preferred in wax materials. Typical examples of polyolefin waxes are polyethylene wax and polypropylene wax. Preferred examples of polyolefin waxes include thermally decomposable polyethylene wax, which is a thermal decomposition product of polyethylene resin, and thermally decomposable polypropylene wax, which is a thermal decomposition product of polypropylene resin.

[0082] In one example, the fusible core can be provided with a first part consisting of a first wax material having a melting point below the forming temperature, and a second part consisting of a second wax material that is incompatible with the first wax material and has a melting point above the forming temperature. By adjusting the volume ratio of the first part, which softens and expands within the stamping die, to the second part, which does not soften within the stamping die, the pressure generated within the stamping die can be controlled.

[0083] When polyolefin wax is incorporated into the first wax material, a wax containing an organic compound with polar groups is preferably incorporated into the second wax material. This is because waxes primarily composed of hydrocarbons are generally incompatible with waxes composed of organic compounds with polar groups.

[0084] Polar groups refer to functional groups such as hydrocarbon, amino, amide, carbonyl, carboxyl, and ester groups that contain carbon-oxygen or carbon-nitrogen bonds (excluding ether groups).

[0085] Typical examples of waxes containing organic compounds with polar groups include waxes containing one or more organic compounds selected from hydroxy fatty acid amides, fatty acid amides, hydroxy fatty acid esters, and fatty acid esters.

[0086] 1.2. Core Removal Process

[0087] The core removal process (ii) is the process of removing the solidified core obtained from the molding process from the core used in the molding process.

[0088] Even after the forming process is completed and the stamping die is opened, if the pressure inside the cavity remains high, the hollow structure of the solidified material is prone to expansion and deformation. To prevent this, it is preferable to wait until the upper die is lifted before proceeding. Figure 9 As shown, immediately insert one end of the metal tube 200 into the elastic plug P and make it pass through, thereby reducing the pressure inside the cavity.

[0089] If the other end of the metal tube 200 is pre-connected to the recycling container 300, the internal pressure of the cavity can be safely reduced.

[0090] As a variation, a through hole for the metal tube 200 can be pre-formed in the stamping die 100. Before lifting the upper die, the metal tube 200 is inserted into the solidified material 30 inside the stamping die 100 through the through hole to reduce the pressure inside the cavity. In this variation, the metal tube 200 can be inserted either after or before the die is opened.

[0091] To completely expel the wax material from the cavities of the hollow structure of the cured material, one can simply heat the FRP article in an oven to completely melt the fusible core within the hollow structure.

[0092] When the wax material is discharged through the metal tube 200, it is preferable to heat at least a portion of the metal tube to prevent the wax inside the metal tube from solidifying.

[0093] To shorten the time required for wax material to drain, multiple through holes can be created in the hollow structure of the cured material. Air is allowed to flow into the cavity through some of these holes, while wax flows out through the other holes. These through holes can be created using a drilling machine or hole saw after the forming process.

[0094] In one example, such as Figure 10 As shown, air can flow into the cavity through metal tube 201 while wax is discharged from the cavity through metal tube 202. Metal tube 201 is inserted into an elastomer plug P1 that blocks a through-hole in the hollow structure of the cured material 30, and metal tube 202 is inserted into an elastomer plug P2 that blocks another through-hole. The number of through-holes blocked by elastomer plug P1 and the number of through-holes blocked by elastomer plug P2 are not limited to one, but can be two or more.

[0095] One end of the metal tube 201 that is not inserted into the cavity is open to the atmosphere. However, when air flows into the cavity through the metal tube 201, a pressure loss occurs, thus making the pressure inside the cavity lower than atmospheric pressure. To reduce this pressure loss, the metal tube 201 is preferably as short as possible, and its inner diameter is preferably as large as possible.

[0096] It can also be used for Figure 10 The example shown can be modified so that pressurized gas flows into the cavity through metal tube 201. For example, one end of the tube not inserted into the cavity can be connected to a compressor to deliver pressurized air into the cavity. Alternatively, instead of a compressor, a gas cylinder can be connected to deliver pressurized inert gas (e.g., nitrogen) into the cavity.

[0097] In the method of using metal tube 201 to allow gas to flow into the cavity, it is not necessary to use metal tube 202 in the process of wax discharge. Alternatively, the wax can be discharged from the cavity through the through hole formed in the solidified material after the molding process.

[0098] 1.3. Various Implementation Methods

[0099] Various additives may also be added as needed to the fusible core used in the FRP article manufacturing method involved in the implementation.

[0100] In one example, induction heating of a fusible core is achieved by adding particles of a material that generates heat under a high-frequency electromagnetic field. Examples of such materials include strongly magnetic materials, ferrimagnetic materials, and conductive materials. Examples of strongly magnetic materials include iron, nickel, cobalt, ferroalloys, nickel alloys, cobalt alloys, permeable magnetic alloys, and various types of steel. Examples of ferrimagnetic materials include magnetite, nickel-zinc ferrite, manganese-zinc ferrite, and copper-zinc ferrite. Examples of conductive materials include copper, aluminum, and brass.

[0101] In another example, microwave heating of a fusible core is achieved by adding particles of a material that absorbs microwaves and generates heat. Examples of such materials include silicon carbide, ferrite, barium titanate, anatase titanium dioxide, graphite, and carbon black.

[0102] Induction heating or microwave heating of the fusible core is preferred when preheating the fusible core outside the stamping die.

[0103] In the case of a fusible core with a first part and a second part, a colorant such as a pigment or dye can be used to visually distinguish them based on their color difference. The colorant can be added to either the first part or the second part, or to both.

[0104] By making the first part and the second part different colors, it is possible to prevent the configuration of the first part and the second part from being confused, for example, when assembling a fusible core.

[0105] Even after the core removal process, it is appropriate for the first and second parts to have different colors in the operation of melting the first and second parts to distinguish the first wax material and the second wax material.

[0106] In the molding process, where the wax material is melted in at least a portion of the fusible core, a partially fusible core can also be used instead of a fusible core. For example... Figure 11As illustrated in the cross-sectional view, the partially fusible core 14 is composed of a fusible core (fusible portion) 10 containing wax material and an outer skin 12 covering the fusible core. When the wax material is melted in the fusible core (fusible portion), the outer skin can be used to prevent the molten wax material from entering the gap between the prepreg preform and the stamping die.

[0107] To prevent the outer skin 12 from breaking during the molding process when the fusible core (fusible part) 10 deforms or expands, the material of the outer skin 12 of the partially fusible core 14 must be able to elongate and deform at the molding temperature. This elongation and deformation can be elastic, plastic, or a combination of both.

[0108] Therefore, the preferred material for the outer skin 12 is not limited and can be an organic material, particularly a resin material. Preferred materials for the outer skin include synthetic polymers such as polyolefins, polyamides, polyesters, polyurethanes, silicones, and fluororubbers, and further include elastomers composed of these polymers.

[0109] When manufacturing the partially fusible core 14, for example, the fusible core (fusible part) 10 is wrapped with a polymer film prepared for the outer skin 12 and sealed by bonding or welding.

[0110] The outer skin 12 can also be formed using a shrink tube made of the aforementioned polymer. This can be achieved by heat-shrinking the shrink tube into which the fusible core (fusible part) is inserted, and then heat-sealing both ends of the shrink tube.

[0111] The outer skin 12 can also be formed using a low-temperature curing liquid rubber composed of the aforementioned polymer. Simply coat the surface of the fusible core (fusible part) 10 with the liquid rubber and cure it at a temperature at which the wax does not melt.

[0112] The outer skin 12 can also be formed from a UV-curable elastomer. A UV-curable elastomer is a UV-curable resin that cures into an elastomer similar to rubber; examples include UV-curable silicone rubber and UV-curable urethane acrylate. UV-curable elastomers can also cure for a short time at room temperature, which makes them suitable for outer skin materials.

[0113] 1.4. Scope of Application

[0114] The FRP article manufacturing method described in the embodiments can also be applied to the case of manufacturing large-sized FRP articles from two or more partial prepreg preforms.

[0115] In an FRP article manufactured by the FRP article manufacturing method according to the embodiments, FRP can also be formed into a composite with a component made of a material other than FRP, such as metal.

[0116] 2. FRP items

[0117] Another embodiment of the present invention is an FRP article manufactured by the FRP article manufacturing method according to the embodiment described in section 1. above with reference to specific examples.

[0118] Figure 2 The hollow FRP item 1 shown is composed of a single hollow structural part, as follows: Figure 3 As shown, its interior is hollow. The FRP article 1 has a through hole H′ that leads from the interior space of the hollow to the outside. This through hole H′ is blocked by an elastomer plug P. As a result, this structure is because the FRP article 1 is manufactured by the manufacturing method involved in the embodiment.

[0119] In FRP article 1, the elastomer plug P is tapered in shape along the direction from the interior space of the cavity to the outside. In one example, instead of tapering, or in addition to tapering, the elastomer plug P may also have protrusions or indentations on the sides.

[0120] 3. Summary of Implementation Methods

[0121] The embodiments of the present invention include the following, but are not limited to these.

[0122] [Embodiment 1] A manufacturing method is a fiber-reinforced resin manufacturing method having the following steps: a molding step in which a prepreg preform having a core inner portion having a fusible core made of wax material disposed on its inner side is placed in a stamping die and heated to obtain a cured product having a hollow structure; and a core removal step in which the fusible core is removed from the cured product, a through hole is formed in the core inner portion of the prepreg preform, and an elastomer plug is inserted into the through hole.

[0123] [Embodiment 2] According to the manufacturing method of Embodiment 1, at least a portion of the above-mentioned elastomeric plug is conical, and the side with the larger area of ​​the cross section orthogonal to the insertion direction is inserted into the above-mentioned through hole towards the above-mentioned fusible core.

[0124] [Embodiment 3] According to the manufacturing method of Embodiment 1 or 2, the above-mentioned elastomeric plug has a protrusion or a depression on the side.

[0125] [Embodiment 4] According to any one of Embodiments 1 to 3, in the above-mentioned core removal process, one end of the metal tube is inserted into the above-mentioned elastomer plug and made to pass through it, so that all or part of the wax material is discharged from the cavity of the above-mentioned hollow structure portion formed in the above-mentioned solidified material through the metal tube.

[0126] [Embodiment 5] According to the manufacturing method of Embodiment 4, at least a portion of the metal tube is heated in the above-mentioned core removal process.

[0127] [Embodiment 6] According to the manufacturing method involved in Embodiment 4 or 5, the other end of the metal tube is connected to a recycling container.

[0128] [Embodiment 7] According to any one of Embodiments 1 to 3, in the above-mentioned core removal process, one end of the metal tube is inserted into the above-mentioned elastomer plug and made to pass through it, and gas is allowed to flow into the cavity of the above-mentioned hollow structure portion formed in the above-mentioned solidified material through the metal tube.

[0129] [Embodiment 8] According to the manufacturing method of Embodiment 7, the other end of the metal tube is open to the atmosphere.

[0130] [Embodiment 9] The gas is pressurized according to the manufacturing method of Embodiment 7.

[0131] [Embodiment 10] According to any one of Embodiments 1 to 9, in the above-described molding process, the wax material is softened in at least a portion of the fusible core.

[0132] [Embodiment 11] According to any one of Embodiments 1 to 10, in the above-described molding process, the wax material is melted in at least a portion of the fusible core.

[0133] [Embodiment 12] According to the manufacturing method of Embodiment 10 or 11, the fusible core has a first part made of a first wax material and a second part made of a second wax material that is incompatible with the first wax material, wherein the second wax material does not soften in the molding process.

[0134] [Embodiment 13] According to the manufacturing method of Embodiment 12, either the first wax material or the second wax material is mainly composed of hydrocarbons, and the other contains an organic compound having polar groups.

[0135] [Embodiment 14] According to the manufacturing method of any one of Embodiments 1 to 13, the above-mentioned fusible core contains particles of a material that has the property of generating heat under a high-frequency electromagnetic field.

[0136] [Embodiment 15] According to the manufacturing method of any one of Embodiments 1 to 13, the above-mentioned fusible core contains particles of a material that has the property of absorbing microwaves and generating heat.

[0137] [Embodiment 16] According to the manufacturing method of any one of Embodiments 1 to 15, the fusible core is preheated before the above forming process.

[0138] [Embodiment 17] According to the manufacturing method of any one of Embodiments 1 to 16, in the prepreg preform, the fusible core is disposed inside the core inner portion without being covered by the outer skin.

[0139] [Embodiment 18] A manufacturing method is a fiber-reinforced resin manufacturing method having the following steps: a molding step in which a prepreg preform having a core inner portion having a fusible core made of wax material disposed on its inner side is placed in a stamping die and heated to obtain a cured product having a hollow structure; and a core removal step in which the fusible core is removed from the cured product, and a first through hole and a second through hole are formed in the core inner portion of the prepreg preform, a first elastomeric plug is inserted into the first through hole, and a second elastomeric plug is inserted into the second through hole.

[0140] [Embodiment 19] According to the manufacturing method of Embodiment 18, both the first elastomeric plug and the second elastomeric plug are at least partially tapered, and both are inserted into the through hole with the side of the cross section with the larger area orthogonal to the insertion direction facing the fusible core.

[0141] [Embodiment 20] According to the manufacturing method of Embodiment 18 or 19, both the first elastomer plug and the second elastomer plug have protrusions or depressions on their sides.

[0142] [Embodiment 21] According to any one of Embodiments 18 to 20, in the above-mentioned core removal process, one end of the first metal tube is inserted into the first elastomer plug and made to pass through it, and one end of the second metal tube is inserted into the second elastomer plug and made to pass through it. While gas flows into the cavity of the hollow structure portion formed in the above-mentioned solidified material through the first metal tube, all or part of the wax material is discharged from the cavity through the second metal tube.

[0143] [Embodiment 22] According to the manufacturing method of Embodiment 21, at least a portion of the second metal tube is heated in the above-described core removal process.

[0144] [Embodiment 23] According to the manufacturing method of Embodiment 21 or 22, the other end of the second metal tube is connected to the recycling container.

[0145] [Embodiment 24] According to the manufacturing method of any one of Embodiments 21 to 23, the other end of the first metal tube is open to the atmosphere.

[0146] [Embodiment 25] The gas is pressurized according to the manufacturing method of any one of Embodiments 21 to 23.

[0147] [Embodiment 26] According to any one of Embodiments 18 to 25, in the above-described molding process, the wax material is softened in at least a portion of the fusible core.

[0148] [Embodiment 27] According to any one of Embodiments 18 to 26, in the above-described molding process, the wax material is melted in at least a portion of the fusible core.

[0149] [Embodiment 28] According to the manufacturing method of Embodiment 26 or 27, the fusible core has a first part made of a first wax material and a second part made of a second wax material that is incompatible with the first wax material, wherein the second wax material does not soften in the molding process.

[0150] [Embodiment 29] According to the manufacturing method of Embodiment 28, either the first wax material or the second wax material is mainly composed of hydrocarbons, and the other contains an organic compound having polar groups.

[0151] [Embodiment 30] According to any one of Embodiments 18 to 29, the above-mentioned fusible core contains particles of a material that has the property of generating heat under a high-frequency electromagnetic field.

[0152] [Embodiment 31] According to any one of Embodiments 18 to 29, the above-mentioned fusible core contains particles of a material that has the property of absorbing microwaves and generating heat.

[0153] [Embodiment 32] According to any one of Embodiments 18 to 31, the fusible core is preheated before the above-mentioned forming process.

[0154] [Embodiment 33] According to the manufacturing method of any one of Embodiments 18 to 32, in the prepreg preform, the fusible core is disposed inside the core inner portion without being covered by the outer skin.

[0155] [Embodiment 34] A fiber-reinforced resin article having a hollow structure, a cavity formed in the hollow structure, a through hole extending from the interior space of the cavity to the outside, and an elastomeric plug blocking the through hole.

[0156] [Embodiment 35] According to the fiber-reinforced resin article of Embodiment 34, at least a portion of the elastomeric plug is tapered along the direction from the interior space of the cavity toward the outside.

[0157] [Embodiment 36] According to the fiber-reinforced resin article of embodiment 34 or 35, the above-mentioned elastomer plug has a protrusion or depression on the side.

[0158] 4. Experimental Results

[0159] A hollow cuboid of 72mm×36mm×20mm made of FRP was prototyped according to the following steps.

[0160] A 2mm thick piece of SMC (Mitsubishi Chemical Corporation STR120N131) is cut into a predetermined shape, and after forming a cylindrical through hole with an inner diameter of 6mm in a portion of it, it is further bent to produce a prepreg preform with a roughly net shape.

[0161] When making prepreg preforms, a partially fusible core prepared by a separate process is placed inside them.

[0162] The partially fusible core is made by covering the fusible part (fusible core) made of synthetic wax (ITOHWAX E-70G) containing high fatty acid esters with a melting point of 68°C with an outer skin formed by using a 7μm thick nylon 6 film, thereby making a cuboid that fits perfectly inside the prepreg preform.

[0163] Insert a silicone rubber plug into the through hole of the SMC. The silicone rubber plug is a truncated cone-shaped plug with a diameter of 6mm on the upper surface, 10mm on the lower surface, and a height of 4mm. It is inserted into the through hole with the lower surface facing the core.

[0164] With the prepreg preform facing upwards and the core encased within it placed into a mold preheated to the same temperature as the molding temperature, the prepreg was heated and pressurized to solidify. The molding temperature was set to 140°C, and the molding time was set to 10 minutes. After molding, immediately after lifting the upper mold, one end of a stainless steel tube with an outer diameter of 2 mm and an inner diameter of 1 mm was inserted into a silicone rubber stopper. As a result, the melted wax flowed from the inside of the molded part through the stainless steel tube into a container connected to the other end of the stainless steel tube.

[0165] The present invention has been described above with reference to specific embodiments, but these embodiments are provided as examples and do not limit the scope of the invention. The embodiments described in this specification can be modified in various ways to achieve the effects of the invention, and can be combined with features described in other embodiments within a feasible scope.

[0166] Industrial availability

[0167] The invention disclosed in this specification is not limited and can be preferably used in the manufacture of components (including structural components) for automobiles, ships, railway vehicles, aircraft and other transportation equipment, bicycle frames, and various sporting goods including tennis rackets and golf clubs, made from fiber-reinforced resin.

[0168] Symbol Explanation

[0169] 1. Fiber-reinforced resin articles

[0170] 10 Fusible cores

[0171] 12 outer skin

[0172] 14 Partially Fusible Core

[0173] 20 Prepreg Preforms

[0174] 30 cured product

[0175] 100 stamping die

[0176] 102 Lower mold

[0177] 104 upper mold

[0178] 106 Sliding Core

[0179] 200, 201, 202 metal pipes

[0180] 300 recycling containers

[0181] H, H' through holes

[0182] P, P1, P2 elastomer plugs

[0183] WM wax material.

Claims

1. A method for manufacturing fiber-reinforced resin, comprising the following steps: a molding step in which a prepreg preform having a core inner portion having a fusible core made of wax material disposed on its inner side is placed in a stamping die and heated to obtain a cured product having a hollow structure; and a core removal step in which the fusible core is removed from the cured product, a through hole is formed in the core inner portion of the prepreg preform, and an elastomer plug is inserted into the through hole.

2. The fiber-reinforced resin manufacturing method according to claim 1, wherein at least a portion of the elastomer plug is conical, and the side with the larger area of ​​the cross section orthogonal to the insertion direction is inserted into the through hole toward the fusible core.

3. The fiber-reinforced resin manufacturing method according to claim 1 or 2, wherein the elastomer plug has protrusions or depressions on its side.

4. The fiber-reinforced resin manufacturing method according to claim 1 or 2, wherein in the core removal process, one end of a metal tube is inserted into the elastomer plug and made to pass through it, and all or part of the wax material is discharged from the cavity formed in the hollow structure of the cured material through the metal tube.

5. The fiber-reinforced resin manufacturing method according to claim 4, wherein at least a portion of the metal tube is heated during the core removal process.

6. The fiber-reinforced resin manufacturing method according to claim 4, wherein the other end of the metal tube is connected to a recycling container.

7. The fiber-reinforced resin manufacturing method according to claim 1 or 2, wherein in the core removal process, one end of a metal tube is inserted into the elastomer plug and made to pass through it, and gas flows through the metal tube into the cavity formed in the hollow structure of the cured material.

8. The method for manufacturing fiber-reinforced resin according to claim 7, wherein the other end of the metal tube is open to the atmosphere.

9. The method for manufacturing fiber-reinforced resin according to claim 7, wherein the gas is pressurized.

10. The method for manufacturing fiber-reinforced resin according to claim 1 or 2, wherein in the molding step, the wax material is softened in at least a portion of the fusible core.

11. The method for manufacturing fiber-reinforced resin according to claim 1 or 2, wherein in the molding step, the wax material is melted in at least a portion of the fusible core.

12. The fiber-reinforced resin manufacturing method according to claim 10, wherein the fusible core has a first portion composed of a first wax material and a second portion composed of a second wax material incompatible with the first wax material, the second wax material not softening during the molding process.

13. The method for manufacturing fiber-reinforced resin according to claim 12, wherein either the first wax material or the second wax material is mainly composed of hydrocarbons, and the other contains an organic compound having polar groups.

14. The method for manufacturing fiber-reinforced resin according to claim 1 or 2, wherein the fusible core contains particles of a material having the property of generating heat under a high-frequency electromagnetic field.

15. The method for manufacturing fiber-reinforced resin according to claim 1 or 2, wherein the fusible core contains particles of a material having the property of absorbing microwaves and generating heat.

16. The method for manufacturing fiber-reinforced resin according to claim 1 or 2, wherein the fusible core is preheated before the molding process.

17. The method for manufacturing fiber-reinforced resin according to claim 1 or 2, wherein in the prepreg preform, the fusible core is not covered by an outer skin but is disposed inside the core inner package.

18. A method for manufacturing fiber-reinforced resin, comprising the following steps: a molding step in which a prepreg preform having a core inner portion having a fusible core made of wax material disposed on its inner side is disposed in a stamping die and heated to obtain a cured product having a hollow structure; and a core removal step in which the fusible core is removed from the cured product, and a first through hole and a second through hole are formed in the core inner portion of the prepreg preform, a first elastomeric plug is inserted into the first through hole, and a second elastomeric plug is inserted into the second through hole.

19. The method for manufacturing fiber-reinforced resin according to claim 18, wherein both the first elastomer plug and the second elastomer plug are at least partially tapered, and both are inserted into the through hole with the side of the cross-section with the larger area orthogonal to the insertion direction facing the fusible core.

20. The method for manufacturing fiber-reinforced resin according to claim 18 or 19, wherein both the first elastomer plug and the second elastomer plug have protrusions or depressions on their sides.

21. The fiber-reinforced resin manufacturing method according to claim 18 or 19, wherein in the core removal process, one end of the first metal tube is inserted into the first elastomer plug and made to pass through it, and one end of the second metal tube is inserted into the second elastomer plug and made to pass through it, while gas flows into the cavity formed in the hollow structure of the cured material through the first metal tube, and all or part of the wax material is discharged from the cavity through the second metal tube.

22. The fiber-reinforced resin manufacturing method according to claim 21, wherein at least a portion of the second metal tube is heated in the core removal process.

23. The method for manufacturing fiber-reinforced resin according to claim 21, wherein the other end of the second metal tube is connected to a recycling container.

24. The fiber-reinforced resin manufacturing method according to claim 21, wherein the other end of the first metal tube is open to the atmosphere.

25. The method for manufacturing fiber-reinforced resin according to claim 21, wherein the gas is pressurized.

26. The method for manufacturing fiber-reinforced resin according to claim 18 or 19, wherein in the molding step, the wax material is softened in at least a portion of the fusible core.

27. The method for manufacturing fiber-reinforced resin according to claim 18 or 19, wherein in the molding step, the wax material is melted in at least a portion of the fusible core.

28. The method for manufacturing fiber-reinforced resin according to claim 26, wherein the fusible core has a first portion composed of a first wax material and a second portion composed of a second wax material incompatible with the first wax material, the second wax material not softening during the molding process.

29. The method for manufacturing fiber-reinforced resin according to claim 28, wherein either the first wax material or the second wax material is mainly composed of hydrocarbons, and the other contains an organic compound having polar groups.

30. The method for manufacturing fiber-reinforced resin according to claim 18 or 19, wherein the fusible core contains particles of a material having the property of generating heat under a high-frequency electromagnetic field.

31. The method for manufacturing fiber-reinforced resin according to claim 18 or 19, wherein the fusible core contains particles of a material having the property of absorbing microwaves and generating heat.

32. The method for manufacturing fiber-reinforced resin according to claim 18 or 19, wherein the fusible core is preheated before the molding process.

33. The method for manufacturing fiber-reinforced resin according to claim 18 or 19, wherein in the prepreg preform, the fusible core is disposed inside the core inner portion without being covered by an outer skin.

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