JP2004314508A - Honeycomb structure for sandwich panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an FRP sandwich panel which is light in weight and can hardly be peeled off. <P>SOLUTION: The plane aggregate of hollow pillar-like cells is provided. Expandable resin particles are set in the hollow parts of the cells. Reinforcing fibers are arranged on the two main surfaces of a honeycomb structure in which a resin for an FRP matrix is packed in the openings of the cells to cover the expandable resin particles and placed in a mold. After mold clamping, the resin is melted by heating, and the expandable resin particles are expanded. The molten resin is extruded into the reinforcing fibers, and the resin is cured. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a honeycomb structure used as a core material of a fiber reinforced plastic (hereinafter referred to as FRP) sandwich panel, and a method for manufacturing an FRP sandwich panel using the honeycomb structure.
[0002]
[Prior art]
As a molding method of an FRP product, an RI method (resin injection method), an RTM method (resin transfer molding method), and an S-RIM method (eslim method: structural reaction injection molding) are known. According to these molding methods, a FRP product is obtained by setting a fiber base material as a reinforcing material in a mold, closing the mold, and applying a resin liquid (a molten resin or a one-liquid or two-liquid (A curable resin or a reactive monomer of a type), and impregnated into a fiber base material, and then cured at room temperature or under heating.
[0003]
The most effective way to reduce the weight of an FRP product is to make the inside of the product hollow (hollow), but the manufacturing method is often complicated and difficult to implement. For this reason, FRP products incorporating a lightweight core material (hereinafter referred to as FRP sandwich panels) have been produced. In particular, in FRP products requiring impact resistance, it is better to incorporate a lightweight core material such as foamed polyurethane, foamed polystyrene, foamed polypropylene, etc., rather than hollowing the inside.
[0004]
Such an FRP sandwich panel is made by, for example, forming a lightweight core material by foam molding, providing a reinforcing fiber layer on the outer surface of the core material, setting it in a mold, injecting a resin liquid into the mold, and reinforcing the reinforcing fiber layer. It is manufactured by impregnating a resin liquid with the resin and curing the resin. As the core material, lightweight polyurethane foam (polyurethane foam) is often used. The foam molded body manufactured for the purpose of use as a core material is heated by annealing, that is, heating in air at a temperature 5 to 10 ° C. lower than the thermal deformation temperature of the material for several tens minutes to several hours, and then gradually cooling. After the treatment, the residual internal stress is removed and the unreacted portion is sufficiently hardened, and then used as a core material.
[0005]
As shown in FIG. 1, an FRP sandwich panel manufactured by a molding method such as an S-RIM method using foamed polyurethane as a core material has a relatively thick foamed polyurethane core layer 1 sealed with an FRP layer 2 around the foamed polyurethane core layer 1. The cross-sectional structure is as follows. Even if the foamed polyurethane is lightweight, the weight ratio of the core portion to the entire FRP sandwich panel is large because the volume is relatively large, and for example, the weight of the polyurethane core portion may occupy 25% of the whole. Therefore, attempts have been made to further reduce the weight of the FRP sandwich panel by using a low-density foamed polyurethane, which is further reduced in weight by increasing the expansion ratio, as a core material.
[0006]
However, since low-density foamed polyurethane has particularly low compressive strength, when used as a core material, there is a problem that cells are broken by the pressure of the injected resin liquid, and the FRP resin permeates into the foamed polyurethane core. For this reason, the desired weight reduction could not be achieved. This tendency is particularly remarkable when using open-celled polyurethane as the core material.
[0007]
In order to solve such a problem, it has been proposed to provide a resin layer between the foamed polyurethane core layer and the FRP layer in an FRP sandwich panel including the foamed polyurethane core layer and the FRP layer (for example, see Patent Document 1). ). By forming a resin layer on the surface of the foamed polyurethane core layer, it is possible to prevent the FRP matrix resin from penetrating into the foamed polyurethane core layer, and to reduce the weight of the FRP sandwich panel.
[0008]
[Patent Document 1]
JP-A-5-147048 (page 2-3, FIG. 1)
[0009]
[Problems to be solved by the invention]
However, if a resin layer is provided on the surface of the foamed polyurethane layer, the adhesive strength cannot be expected from the viewpoint of the affinity between the resin layer and the FRP matrix resin. In the obtained FRP sandwich panel, the FRP layer is formed of the foamed polyurethane. There is a problem of peeling from the layer. Further, in manufacturing the FRP sandwich panel, a resin liquid is injected into and impregnated into the FRP reinforcing fiber from outside the mold, but the injection of the resin liquid is complicated and technically difficult.
[0010]
The present invention solves the above problems, and can produce an FRP sandwich panel without injecting a resin liquid from the outside of the mold, and does not cause a problem of peeling from the FRP reinforcing fiber, for an FRP sandwich panel. An object of the present invention is to provide a honeycomb structure and a method for manufacturing an FRP sandwich panel using the honeycomb structure.
[0011]
[Means for Solving the Problems]
According to the present invention, in order to solve the above problems, a planar aggregate of hollow columnar cells, in which expandable resin particles are provided in a hollow portion of the cells, and cover the expandable resin particles. There is provided a honeycomb structure in which an opening of the cell is filled with an FRP matrix resin.
[0012]
According to the present invention, in order to solve the above-mentioned problems, reinforcing fibers are arranged on the two main surfaces of the above-mentioned honeycomb structure, put into a forming die, and after clamping, heating to melt the resin. A method for producing an FRP sandwich panel, characterized in that foaming of the expandable resin particles is performed, a molten resin is extruded into reinforcing fibers, and the resin is cured.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings. FIG. 2 is a perspective view showing one embodiment of the honeycomb structure of the present invention, and FIG. 3 is a longitudinal sectional view taken along AA ′ of FIG. The honeycomb structure 3 is made up of a planar aggregate (honeycomb base material) 9 of hollow columnar cells surrounded by cell walls 4, and expandable resin particles 5 are provided in the hollow portions of the cells. An opening of the cell is filled with an FRP matrix resin 6 so as to cover the resin particles 5.
[0014]
As a material constituting the honeycomb base material 9, a metal such as aluminum, a resin such as aramid, cellulose (paper), or FRP in which a reinforcing fiber is impregnated with a resin can be used. The shape of the cell is not particularly limited, and its cross section may be circular, elliptical, or polygonal (triangular, square, pentagonal, hexagonal, etc.). The size of the cell and the thickness of the cell wall are not particularly limited, and can be appropriately designed according to the purpose and application. The thickness (d in FIG. 3) of the honeycomb structure is preferably 5 mm or more.
[0015]
As the expandable resin particles 5, polystyrene beads as a raw material of so-called expanded polystyrene or the like, or spherical particles of a thermoplastic resin containing a hydrocarbon at the center thereof can be used. The expandable resin particles 5 preferably have an expansion ratio of 100 to 500 times and a particle size of 10 μm to 1 mm.
[0016]
The FRP matrix resin 6 may be any one that is a gel or solid at room temperature, melts and flows out by heating, and then cures. For example, a semi-cured epoxy resin, unsaturated polyester, or the like can be used. . A curing agent, a flame retardant, and the like may be added to the resin 6.
[0017]
As for the volume ratio of the expandable resin particles 5 and the FRP matrix resin 6 in the hollow portion of the cell, the expandable resin particles 5 are preferably 10 to 50%, more preferably 40%, and the FRP matrix resin 6 is preferably 50 to 50%. It is 90%, more preferably 60%.
[0018]
This honeycomb structure can be manufactured, for example, as shown in FIG. First, the honeycomb substrate 9 is pressed into a sheet of the FRP matrix resin 6 having a predetermined thickness (FIG. 4A), and the opening of the cell on one side of the honeycomb substrate 9 is closed with the resin 6 (FIG. 4B). Next, a predetermined amount of the expandable resin particles 5 are filled in the hollow portion of the cell (FIG. 4C), and the opening of the cell is covered with a sheet of the FRP matrix resin 6 having a predetermined thickness (FIG. 4D). Next, pressure is applied by a press or the like to such an extent that the honeycomb base material 9 is not crushed, the opening is closed, and finally, the honeycomb base material 9 is put into a mold, heated and cured (FIG. 4E).
[0019]
5 and 6 show a process of manufacturing an FRP sandwich panel using the above-mentioned honeycomb structure. First, as shown in FIG. 5, reinforcing fibers 7 are arranged on the two main surfaces of the honeycomb structure 3 and placed in the mold 8. As the reinforcing fibers 7, fibers generally used for FRP can be used, and for example, glass fibers, carbon fibers, aramid fibers, ceramic fibers, metal fibers, and the like can be used. These fibers are mixed with organic fibers such as polyethylene fibers, polypropylene fibers, and polyamide fibers as necessary to obtain a sediment, which is then compression-molded or suction-filtrated into a specific shape, or matted with a needle punch. It may be manufactured by molding or the like.
[0020]
After disposing the honeycomb structure 3 and the reinforcing fibers 7 in the mold 8, the mold is clamped and heated. Then, as shown in FIG. 6, the resin 6 is melted, and at the same time or thereafter, the expandable resin particles 5 expand 150 to 200 times to fill the hollow portion in the cell. At this time, since the resin 6 covering the opening of the cell is in a molten state, the resin 6 is extruded from the hollow portion of the cell toward the reinforcing fiber 7 as the expandable resin particles 5 are foamed, and is impregnated with the reinforcing fiber. After that, the particles 5 still try to continue foaming, but since the periphery is restrained by the cell wall surface 4, they act to press the reinforcing fiber 7 against the surface of the mold 8. In this state, the resin 6 is cured, and after cooling, the resin 6 is taken out of the mold 8 to obtain an FRP sandwich panel.
[0021]
The heating temperature is determined according to the expandable resin particles 5 and the resin 6 to be used, that is, so that the expandable resin particles 5 sufficiently foam and the resin 6 reaches a temperature sufficient to melt. Specifically, when polypropylene resin particles are used as the expandable resin particles 5 and epoxy resin is used as the resin 6, the heating is performed at about 120 ° C.
[0022]
【The invention's effect】
By using the honeycomb structure of the present invention, it is not necessary to inject the resin liquid from outside the mold, and the FRP sandwich panel can be easily manufactured.
[Brief description of the drawings]
FIG.
It is sectional drawing of the conventional core built-in FRP molded article.
FIG. 2
It is a perspective view of a honeycomb structure of the present invention.
FIG. 3
It is sectional drawing of AA 'in FIG.
FIG. 4
It is a figure showing a manufacturing process of a honeycomb structure.
FIG. 5
It is a figure showing a manufacturing process of an FRP sandwich panel using a honeycomb structure of the present invention.
FIG. 6
It is a figure showing a manufacturing process of an FRP sandwich panel using a honeycomb structure of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Foamed polyurethane core layer 2 ... FRP layer 3 ... Honeycomb structure 4 ... Cell wall 5 ... Foamable resin particles 6 ... FRP resin 7 ... Reinforcing fiber 8 ... Mold 9 ... Honeycomb base material

Claims (2)

A honeycomb having a planar aggregate of hollow columnar cells, in which expandable resin particles are provided in hollow portions of the cells, and an opening of the cells is filled with an FRP matrix resin so as to cover the expandable resin particles. Structure. A reinforcing fiber is arranged on the two main surfaces of the honeycomb structure according to claim 1, placed in a molding die, and after clamping, heated to melt the resin and expand the expandable resin particles to form the reinforcing fiber. A method for producing an FRP sandwich panel, comprising: extruding a molten resin into a resin and curing the resin.

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