FRP MOLDED PRODUCT AND MANUFACTURING METHOD OF FRP MOLDED PRODUCT

Abstract

An FRP molded product formed by impregnating a fiber base material with a matrix resin using a flow medium, wherein the flow medium has a sheet shape and comprises fibers made of a phenoxy resin, the matrix resin is an epoxy resin, the fiber base material and the flow medium are stacked, at least part of the flow medium is hardened in a state where the part of the flow medium is integrated with the matrix resin by dissolution or adhesion, and the hardened flow medium becomes a design face.

Claims

1. An FRP molded product formed by impregnating a fiber base material with a matrix resin using a flow medium, wherein the flow medium has a sheet shape and comprises fibers made of a phenoxy resin, the matrix resin is an epoxy resin, the fiber base material and the flow medium are stacked, at least part of the flow medium is hardened in a state where the part of the flow medium is integrated with the matrix resin by dissolution or adhesion, and the hardened flow medium becomes a design face.

2. A manufacturing method of an FRP molded product wherein a fiber base material is impregnated with a matrix resin and hardened using a flow medium inside a cavity, comprising: a step of stacking the fiber base material and a sheet-shaped flow medium comprising fibers made of a phenoxy resin inside the cavity, and a step of injecting an epoxy resin as the matrix resin, thereby integrating at least part of the flow medium with the matrix resin by dissolution or adhesion, wherein the flow medium is placed on a surface of a mold inside the cavity, and the hardened flow medium becomes a design face.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0021] FIGS. 1A and 1B are side views showing a flow medium.

[0022] FIG. 2A is a cross-sectional view showing schematically a state before impregnating stacked flow medium and fiber base material with the matrix resin, FIG. 2B an expanded view of the part surrounded with a circle in FIG. 2A, FIG. 2C is a cross-sectional view showing schematically a state where the stacked flow medium and fiber base material are impregnated with a matrix resin and hardened, FIG. 2D is an expanded view of the part surrounded with a circle in FIG. 2C, and FIG. 2E is a cross-sectional view of an actually-manufactured FRP molded product.

[0023] FIGS. 3A to 3E explain a manufacturing method of the FRP molded product.

[0024] FIG. 4 includes maps showing the degrees of fluidity and diffusivity of a matrix resin in an embodiment, where (a) is without the flow medium, and (b) is with the flow medium.

[0025] FIG. 5 is a plot showing the relationship between injection time and impregnation distance of the matrix resin.

[0026] FIGS. 6A to 6D are expanded views from the front face side (design face side) of the FRP molded product, where FIG. 6A and FIG. 6B are without the flow medium, and FIG. 6C and FIG. 6D are with the flow medium.

[0027] FIG. 7 includes a map and a plot of the uneven cross-sectional shape of the front face of the FRP molded product measured with a digital microscope.

[0028] FIG. 8A is a plan view and FIG. 8B is an A-A line arrow view, both of which showing another example of using the flow medium.

[0029] FIG. 9A is a cross-sectional view showing a state where the flow medium is stacked on the front face side (design face side) of the fiber base material and FIG. 9B is a cross-sectional view showing a state after hardening.

[0030] FIG. 10A and FIG. 10B are cross-sectional views for explaining a manufacturing method of the FRP molded product using VaRTM.

[0031] FIG. 11A and FIG. 11B are cross-sectional views for explaining the internal structure of the general FRP molded product.

[0032] FIGS. 12A to 12C are cross-sectional views showing the processes until a dry spot is formed on the front face side (design face side) of the fiber base material.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENT(S)

[0033] An embodiment of the flow medium of this invention is explained.

[0034] As shown in FIG. 1, the flow medium 10 has a sheet shape comprising fibers made of a phenoxy resin. The flow medium 10 is used for improving fluidity/diffusivity of the matrix resin inside the cavity. Included as the flow medium 10 of this invention are a fabric or knit containing fibers made of a phenoxy resin as raw threads, fibers made of a phenoxy resin as raw threads arranged and fixed within a plane, and an unwoven fabric having fibers made of a phenoxy resin bonded.

[0035] Phenoxy resins are thermoplastic resins that have in their molecules a unit expressed by the following general formula (I) and a degree of polymerization of about 18˜70, and can also be copolymers with other ingredients. Phenoxy resins are known to show excellent compatibility with epoxy resins. The ratio occupied with the part made of the unit expressed by the general formula (I) can be 80˜99% of the whole phenoxy resin molecule and even 90˜99%, and setting it within these ranges is preferable in respects of solubility to solvents and compatibility with epoxy resins.

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[0036] A phenoxy resin is mixed with a solvent, an active material is added, and afterwards the solvent is removed to obtain a planar solid matter of phenoxy resin.

[0037] Listed as methods to fiberize a phenoxy resin are, for example, a method where a phenoxy resin is processed into a planar shape, afterwards cut into thin and long thread shapes or cut short and spun into a thread, a method where a liquid-state phenoxy resin is cooled and elongated while being pushed out of a nozzle into a monofilament, and a method where a phenoxy resin solution is fiberized by electrospinning. A multifilament made by twisting together a phenoxy resin filament and a filament made of nylon or another material can be made a raw material of the flow medium 10.

[0038] From the point of view of moldability, the weight-average molecular weight of the phenoxy resin should preferably be 25,000˜50,000, and in the case of melt spinning 35,000˜45,000 is preferred to facilitate fiberizing the phenoxy resin although it is not limited to this range.

[0039] As the method to process the fiberized phenoxy resin into a fabric, knit, or unwoven fabric, a commonly-known technique can be used, and therefore its explanation is omitted here.

[0040] Next, the FRP molded product of this invention is explained.

[0041] As shown in FIG. 2, the FRP molded product 20 is formed by impregnating the fiber base material 30 with the matrix resin 40 using the flow medium 10 and hardening it. In FIG. 2 a fabric flow medium 10 is used. FIG. 2A is a cross-sectional view showing schematically a state before impregnating the stacked flow medium 10 and fiber base material 30 with the matrix resin 40, FIG. 2B is an expanded view of the part surrounded with a circle in FIG. 2A, FIG. 2C is a cross-sectional view showing schematically a state where the stacked flow medium 10 and fiber base material 30 are impregnated with the matrix resin 40 and hardened, FIG. 2D is an expanded view of the part surrounded with a circle in FIG. 2C, and FIG. 2E is a cross-sectional photo of the actually-manufactured FRP molded product 20.

[0042] When FIGS. 2B and 2D are compared, in FIG. 2D hardening occurred in a state where part of the flow medium 10 is integrated with the matrix resin 40. The flow medium 10 containing fibers made of a phenoxy resin is excellent in compatibility with the matrix resin 40 (especially epoxy resins). Therefore, when the matrix resin 40 is injected to the cavity when molding, the matrix resin 40 quickly flows/diffuses due to the effect of the flow medium 10, and at least part of the flow medium 10 dissolves or adheres, eventually hardening in a state where the matrix resin 40 and the flow medium 10 are strongly integrated. The whole flow medium 10 can also dissolve or adhere to the matrix resin 40. In fact, it is evident from the cross-sectional photo in FIG. 2E that hardening occurred in a state where part of the flow medium 10 dissolved or adhered to the matrix resin 40.

[0043] Allowed as the fiber base material 30 are commonly-known materials such as carbon fibers, polyester fibers, polyamide fibers, cellulose fibers, aramid fibers, polypropylene fibers, and glass fibers, and combinations of two or more of them.

[0044] As the form of the fiber base material 30, discontinuous fibers such as a chopped fiber bundle, fabrics made of continuous fibers, or the like can be used. Because discontinuous fibers have more fluidity than fabrics made of continuous fibers, and therefore are excellent in shapability, having advantages in compatibility with three-dimensional shapes, hardly having wrinkles or the like, and producing little scrap materials. Also, a preform of the fiber base material 30 can be used. A discontinuous fiber is manufactured by cutting a fiber bundle made of continuous fibers into a specified length (converting into a chopped form). Then, this discontinuous fiber bundles can be scattered/stacked in random directions and tentatively fixed with a binder into a sheet, manufacturing the fiber base material 30. The “fiber base material 30” in this specification includes its preform.

[0045] The matrix resin 40 can be either thermosetting or thermoplastic.

[0046] As the thermosetting resin, although there is no limitation as far as it has compatibility with the flow medium 10, for example, epoxy resins, urethane resins, vinyl ester resins, unsaturated polyester resins, and phenol resins can be listed. Epoxy resins are especially preferable because they are excellent in compatibility with phenoxy resins that are raw materials of the flow medium 10.

[0047] Preferably used as the thermoplastic resin are in-situ polymerization type PA6, in-situ polymerization type acrylic resins (methyl methacrylate resins), in-situ polymerization type urethane resins, and the like

[0048] These thermoplastic resins and thermosetting resins can be used alone or in a mixture of two or more kinds.

[0049] Next, explained is the manufacturing method of the FRP molded product of this invention. Although in this embodiment a case of using the VaRTM method is explained, this invention is not limited to this but can be applied to other methods such as infusion molding where the FRP molded product is manufactured by impregnating, hardening, or polymerizing the fiber base material with the matrix resin inside the cavity.

[0050] As shown in FIG. 3A, the cavity 52 is formed with the vacuum bag 50 and the mold 51, and the cavity 52 is provided with a resin injection port 52a and a suction port 52b. Gaps between the vacuum bag 50 and the mold 51 are sealed with sealing materials 53. Note that the structure of the cavity 52 is not limited to the one shown, but another can be chosen as appropriate.

[0051] First, as shown in FIG. 3B, the fiber base material 30 and the flow medium 10 are placed stacked inside the cavity 52. Although in FIG. 3 the flow medium 10 is placed on the front face side of the fiber base material 30, it can be placed on the back face side. At this time, if necessary, the interior of the cavity 52 is heated to a specified temperature.

[0052] Next, as shown in FIG. 3C, a resin injection route 55 connected to a resin tank 54 is closed with a valve 56, and a suction route 57 connected to a vacuum pump (not shown) is opened with a valve 58. Then, through the suction port 52b of the suction route 57, the interior of the cavity 52 is suction-evacuated.

[0053] Next, as shown in FIG. 3D, the valve 58 is closed, and the valve 56 is opened, thereby pressure-injecting the matrix resin 40 in the resin tank 54 to the cavity 52 through the resin injection route 55 and the resin injection port 52a.

[0054] By the effect of the flow medium 10, the matrix resin 40 quickly flows/diffuses inside the cavity 52. Once the matrix resin 40 has reached the entire area of the cavity 52, a resin pressure (static pressure) is applied to impregnate the fiber base material 30 and the flow medium 10 sufficiently with the matrix resin 40. Then, the valve 56 is closed and kept closed until specified time passes to harden the matrix resin 40. At this time, because the flow medium 10 containing fibers made of a phenoxy resin is excellent in compatibility with the matrix resin 40 (especially epoxy resins) as mentioned above, at least part (or the whole) of the flow medium 10 dissolves or adheres. Eventually, hardening occurs in a state where the matrix resin 40 and the flow medium 10 are integrated.

[0055] As shown in FIG. 3E, by taking the FRP molded product 20 out of the cavity 52, a series of manufacturing processes is complete.

EMBODIMENT

[0056] Used as the fiber base material was Carbon Cloth 12K plain-woven material (400 g/m.sup.2)×4 ply 90 mm×600 mm by Mitsubishi Rayon Co., Ltd. The fiber base material without a flow medium is shorter than 600 mm.

[0057] Used as the flow medium was raw threads of a phenoxy resin arranged in a plane into a sheet. The flow medium was placed between the resin base material and a mold.

[0058] Used as the phenoxy resin was PKHC manufactured by Gabriel Performance Products, LLC. VaRTM was performed in the above-mentioned conditions. FIG. 4 shows a state when 40 minutes have passed since starting the injection of the matrix resin, where (a) of FIG. 4 is without the flow medium 10, and (b) of FIG. 4 is with the flow medium 10. In FIG. 4, the matrix resin 40 was injected from the left side, and air was sucked from the right side.

[0059] As plotted in FIG. 5, while the impregnation distance is 200 mm or shorter without the flow medium, it reached nearly 400 mm with the flow medium.

[0060] FIGS. 6A to 6D are expanded views of the completed FRP molded product viewed from its front face side (design face side), where FIG. 6A and FIG. 6B are without the flow medium, and FIG. 6C and FIG. 6D are with the flow medium. Without the flow medium, voids occurred in spaces surrounded with warp and weft of carbon fibers. With the flow medium, although the phenoxy resin fibers are seen through, the surface was smooth, and no void occurred.

[0061] FIG. 7 shows a map and a plot of unevenness of the surface of the completed FRP molded product measured with a digital microscope. Unevenness was measured in two directions along the width and the length with and without the flow medium.

[0062] It is evident from the plot that large unevenness occurred along the texture of the fiber base material without the flow medium, and that unevenness is small and plane smoothness is high with the flow medium.

[0063] This invention is an FRP molded product and a manufacturing method of the FRP molded product that can enhance plane smoothness and suppress the occurrence of vulnerable parts, and has industrial applicability.

REFERENCES

[0064] 10: Flow medium [0065] 20: FRP molded product [0066] 30: Fiber base material [0067] 40: Matrix resin [0068] 50: Vacuum bag [0069] 51: Mold [0070] 52: Cavity [0071] 52a: Resin injection port [0072] 52b: Suction port [0073] 53: Sealing material [0074] 54: Resin tank [0075] 55: Resin injection route [0076] 56: Valve [0077] 57: Suction route [0078] 58: Valve [0079] 100: Fiber base material [0080] 100a: Front face side [0081] 101: Flow medium [0082] 102: Matrix resin [0083] 103: FRP molded product [0084] 103a: Front face [0085] 104: Unevenness [0086] 200: Vacuum bag [0087] 201: Mold [0088] 202: Cavity [0089] 203: Fiber base material [0090] 203a: Front face side [0091] 203b: Back face side [0092] 204: Matrix resin [0093] 205: FRP molded product [0094] 206: Unevenness [0095] 207: Flow medium [0096] 208: Dry spot