JPH04276435A - Sandwich panel - Google Patents

Abstract

PURPOSE:To provide a sandwich panel light in weight excellent in strength and rigidity and adhesion property between its surface material and core material. CONSTITUTION:A panel is composed of core material and surface material, and cloth and UD prepreg sheet with the tensile strength of at least 30kg/25mm are laminated in order from the core-side.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sandwich panel, and more particularly to a sandwich panel suitable for structural and interior materials of aircraft, vehicles, ships, buildings, etc.

0002

[Prior Art] A sandwich panel is a molded product made by laminating and bonding surface materials on both sides of a core, but the core material is usually made of metal honeycomb, typically aluminum, or aromatic polyamide nonwoven fabric. There are honeycomb structures such as organic fiber honeycombs or paper honeycombs obtained by processing paper, and foam structures such as polyurethane foam, phenol foam, and various vinyl foams.

[0003] Also, as surface materials, glass fibers,
Fiber-reinforced composite materials using carbon fibers, aramid fibers, etc., metal thin plates such as aluminum, copper, etc. can be used alone or
used in combination.

[0004]Sandwich panels constructed in this manner are lightweight and have excellent strength and rigidity, so in recent years they have been used in transportation equipment such as aircraft, vehicles, and ships. It is also used in the construction field to make buildings taller by reducing weight and to simplify construction work.

The strength, rigidity, etc. of such a sandwich panel are determined by the material, density, shape, etc. of the core material, the material, thickness, etc. of the surface material, and the adhesive strength between the core material and the surface material. The material is appropriately selected depending on the intended use.

[0006] Particularly when fiber-reinforced composite materials are used as surface materials, long fibers are preferably used from the viewpoint of performance. (abbreviated as ) and woven prepreg are used in a single layer or in a stack of two or more layers. In particular, when using UD prepreg, its performance differs significantly depending on the direction, so it is common to use two or more layers stacked at different stacking angles so that the fibers cross diagonally.

[0007] Sandwich panels are required to have various properties, and among these, mechanical properties per unit weight, especially properties such as tensile and bending, are required for fabrics with a certain curvature of the fiber axis. It is known that it is advantageous to use UD prepregs with straight fiber axes rather than prepregs.

[0008] However, when the UD prepreg is adhered to the core material directly or through an adhesive layer, among the surface materials that adhere to the core material, the surface parallel to the fiber direction of the UD prepreg closest to the core material There is no problem when peeling off the material, but when peeling off the surface material at right angles to the fiber direction, the adhesive force between the surface material and the core material is the U closest to this core material.
D is dominated by the bonding force of the resin between the fibers of the D prepreg, and there has been a problem that this bonding force is usually low.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sandwich panel that is lightweight, has excellent strength and rigidity, and has high adhesiveness between the surface material and the core material.

0010

[Means for Solving the Problems] In order to solve the above problems, the present inventors have conducted intensive studies and have developed a fabric having a tensile strength of 30 kg/25 mm or more between the UD prepreg and the core material. By using this method, even when the UD prepreg closest to the core material is peeled off at right angles to the fiber direction, it is possible to prevent the fibers from separating between the fibers and maintain high adhesive strength. Based on this finding, we have arrived at the present invention.

That is, the present invention provides a sandwich panel consisting of a core material and a surface material, in which part or all of the surface material is 30 kg/25 m from the side bonded to the core material.
This sandwich panel is characterized in that a woven fabric having a tensile strength of m or more and a unidirectional fiber prepreg sheet are laminated in this order.

The present invention will be explained in detail below. First, among the surface materials used in the present invention, the unidirectional fiber prepreg sheet is made by aligning reinforcing fibers such as various glass fibers, carbon fibers, graphite fibers, aramid fibers, and silicon carbide fibers in one direction. Later, thermosetting resins such as epoxy resins, phenolic resins, unsaturated polyester resins, vinyl ester resins, imide resins, melamine resins, urea resins, nylon, polyphenylene sulfide,
Examples include fiber-reinforced composite materials impregnated with thermoplastic resins such as polybutylene terephthalate, acrylonitrile-butadiene-styrene copolymer (ABS), polystyrene, polyethylene, and polycarbonate, and preferably,
The resin used is a thermosetting resin that has excellent impregnation properties with fibers.

[0013] These reinforcing fibers may be used alone or in combination of two or more types, and the resin may be used alone or in a mixture of two or more types, and various types may be used depending on the purpose. Modifiers, colorants, flame retardants, etc. may be added.

Next, for textiles having a tensile strength of 30 kg/25 mm or more, there are no particular restrictions on the material, weaving structure, etc., and specific examples include glass, aramid, carbon, graphite, etc. Examples of the weave structure include plain weave, satin weave, and twill weave. In addition, the fabric used here having a tensile strength of 30 kg/25 mm or more may be a raw fabric that is not impregnated with resin, or may be in the form of a so-called prepreg that is impregnated with resin. These textiles may be subjected to various surface treatments in order to improve their adhesion to the resin.

In this case, the tensile strength of the fabric is 30 kg/2
The reason why the tensile strength is 5 mm or more is that if the tensile strength is lower than this, when the UD prepreg closest to the core material is torn off at right angles to the fiber direction, the fabric itself will be cut, and the fibers of the UD prepreg will be cut. This is because peeling between fibers occurs, making it difficult to maintain high adhesive strength.

[0016] Also, the reason why the fabric is bonded to the core material side is to maintain a high adhesion force at the interface between the surface material and the core material. Needless to say, even if a woven fabric is used, high adhesion cannot be maintained.

[0017] Apart from these, in order to improve the properties of the sandwich panel, for example, in order to improve the impact resistance, in addition to the above-mentioned textiles and UD prepregs having a tensile strength of 30 kg/25 mm or more, various types of films such as polyvinyl fluoride, polyetherimide,
Nylon etc., various fabrics such as glass fiber fabrics,
Carbon fiber fabric, aramid fiber fabric, polyetheretherketone fiber fabric, or metal foil such as aluminum foil or copper foil may be used in combination.

[0018] However, these materials are different from the core material.
It must be located closer to the surface of the sandwich panel than the fabric and UD prepreg that have a tensile strength of g/25 mm or more. In this case, as described above, an appropriate core material is selected from among metal honeycombs typified by aluminum, organic fiber honeycombs formed from aromatic polyamide nonwoven fabric, paper honeycombs obtained by processing paper, etc. be able to.

[0019] In addition, the honeycomb structure which is the core material of the present invention generally refers to a honeycomb-like plate-like structure made by combining tubes with a hexagonal planar cross section, but in the present invention, the cross section is not hexagonal. It may be polygonal, such as triangular, square, pentagonal, heptagonal, or octagonal, or may be circular or amorphous, and the shape is not particularly limited, but preferably the diameter of the tube is 2 to 10 mm.
The thickness of the side surface of the cylinder is 0.01 to 1.0 mm, and the height of the cylinder is 5 to 50 mm.

[0020] Furthermore, there are no particular restrictions on the method of adhering the surface material and the core material, and there is no problem in adhering them using an adhesive or using a resin contained in the UD prepreg. As for the molding method, any molding method such as a hot pressure molding method, an autoclave molding method, a vacuum bag molding method, etc. may be used.

[0021]

EXAMPLES The present invention will be explained in detail with reference to Examples below. still,
Each value of the examples shown below was measured according to the following method.

(1) Adhesive peel strength Climbing drum peel method (MIL-STD-4
01B)

(2) Bending strength As shown in Fig. 1, a sandwich panel test piece a with a width of 50 mm and a length of 610 mm was supported at four points with an upper span of 254 mm and a lower span of 508 mm, and a crosshead speed of 25. A 4-point bending test was conducted at 4 mm/min. The amount of displacement was measured using calipers at the center of the test piece.

(Example 1) Hi-CARBORON (carbon fiber manufactured by Asahi Kasei Corporation; tensile strength 400 kgf/mm2,
An epoxy resin (manufactured by Nippon Steel Chemical Co., Ltd.; ER-521) was impregnated with a tensile modulus of elasticity of 24 tonfkgf/mm2 to produce a unidirectional prepreg having a carbon fiber basis weight of 95 g/m2 and a resin content of 37 wt%. This prepreg is 0°/
After laminating four layers in the 90°/90°/0° directions, a glass fiber fabric (KS-5370: manufactured by Kanebo Co., Ltd., plain weave, tensile strength: warp direction: 38 kg) is attached to one side of this prepreg.
/25mm, weft direction 34kg/25mm) was used as the surface material, and on the side with the glass fiber fabric, Nomex honeycomb (S
AH-1/8-3.0 manufactured by Showa Aircraft Industry Co., Ltd.) and press-molded at 140°C and 7 kgf/cm.
2 for 2 hours to form a sandwich panel. A test piece was cut out from the obtained sandwich panel so that the longitudinal direction of the test piece was perpendicular to the fiber direction of the UD prepreg closest to the core material, and subjected to the adhesive peel strength test and bending strength test described above. did. The results are shown in Table 1.

(Comparative Example 1) Among the surface materials, the glass fiber fabric was placed on the surface of the sandwich panel, that is,
A sandwich panel was prepared in exactly the same manner as in Example 1, except that there was no glass fiber fabric between the UD prepreg closest to the core material and the core material, and the same tests were conducted. here,
The reason why glass fiber fabric was used on the surface of the sandwich panel was to obtain a surface material with the same thickness as in Example 1.

(Comparative Example 2) Carbon fiber fabric (Hi-CAR
BORON, plain weave with a basis weight of 195g/m2, tensile strength 400kgf/mm2, tensile modulus 24tonfkg
f/mm2) with epoxy resin (manufactured by Nippon Steel Chemical Co., Ltd.; ER
-521), carbon fiber basis weight 195g/m2
, fabric prepreg with a resin content of 37 wt% was produced. Two layers of this prepreg are laminated, and one side of the prepreg is covered with a glass fiber fabric (KS-5370: manufactured by Kanebo Co., Ltd.).
Plain weave, tensile strength: 38 kg/25 mm in the warp direction, 34 kg/25 mm in the weft direction) is used as the surface material,
Nomex honeycomb (SAH-1/8-3.0 Showa Aircraft Industry Co., Ltd.) is made by processing DuPont's aramid nonwoven fabric Nomex into a honeycomb shape and impregnating it with phenol resin, so that the glass fiber fabric is on the front side of the sandwich panel. ) made by the press molding method, 140
Molding was carried out at 7 kgf/cm2 for 2 hours to form a sandwich panel. A test piece was cut out from this sandwich panel and subjected to the above-mentioned adhesive peel strength test and bending strength test. The results are shown in Table 1.

[0027]

[Table 1]

[0028]

[Effects of the Invention] According to the present invention, it is possible to provide a sandwich panel that is lightweight, has excellent strength and rigidity, and has high adhesiveness between the surface material and the core material, and has extremely practical effects. Remarkable.

[0029]

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a means for measuring bending properties used in Examples.

[Explanation of symbols]

a Sandwich panel test piece

Claims (1)

[Claims] Claim 1: In a panel composed of a core material and a surface material, at least a part or all of the surface material is a woven fabric having a tensile strength of 30 kg/25 mm or more from the side bonded to the core material, in one direction. A sandwich panel characterized in that the fiber prepreg sheets are laminated in this order.