JPS6124439A - Sandwich panel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sandwich panel comprising a porous material in the middle and a fiber-reinforced plastics laminate in which the skin layers on both sides The present invention relates to a sandwich panel that has excellent peeling resistance between the skin layers.

Conventional technology In recent years, sandwich panels, which are made by using a honeycomb core as an intermediate material and laminating two or more unidirectional fiber prepregs on each side with the fiber axes perpendicular to each other, are lightweight, high-strength, and high-strength. It has attracted particular attention as a rigid structural material, and is being effectively used as, for example, materials for various aircraft, materials for robots, materials for parabolic antennas, and the like.

In general, unidirectional fiber prepreg has extremely high strength and rigidity in the fiber axis direction, but in the direction perpendicular to the fiber axis, it is obvious that the strength and rigidity are lower than that of the matrix resin. Stay out of bounds. Therefore, in a sandwich panel made by laminating two or more unidirectional fiber prepregs with their fiber axes perpendicular to each other, high strength and stiffness are achieved in the plane direction of the panel, but The fibers have no reinforcing effect in the direction of If they are different, the peel strength between the layers will be significantly reduced, and as a result, the inherent characteristics of the sandwich panel will be impaired, and at the same time, it will be difficult to withstand long-term use.

This is fatal for structural materials that are intended for long-term use, and therefore it is important to improve the delamination strength.
There was a strong demand for the development of an internal switch panel.

Problems to be Solved by the Invention An object of the present invention is to meet such demands and provide a sandwich panel having excellent interlayer peel strength.

Means for Solving the Problems As a result of various studies, the present inventors achieved the objective by using an alternating laminate of unidirectional fiber prepreg and directional fabric prepreg as the skin layer of the sandwich panel. The present invention was completed based on this finding.

That is, the present invention provides a sandwich panel comprising a porous material in the middle and a fiber-reinforced plastics laminate in the skin layers on both sides, wherein the skin layers are comprised of alternating laminates of unidirectional fiber prepreg and directional fabric prepreg. The present invention provides a sandwich panel characterized by:

゛As the intermediate porous abrasive material constituting the sandwich panel of the present invention, for example, a honeycomb core or a porous material having closed cells or open cells can be used. is preferably used. There are no particular restrictions on the shape or material of this honeycomb core, but the materials usually used include metals such as aluminum, glass, aromatic polyamides (for example, "Nomex" manufactured by DuPont), polycarbonate, paper, etc. There are no particular restrictions on the shape or material used for fixing the resin, for example, metals, plastics, glass, and other foams with open or closed cells, or materials obtained by controlled coagulation or solvent extraction. Three-dimensional fabrics or fiber aggregates made of metal fibers, ceramic fibers, glass fibers, carbon fibers, organic fibers, etc. fixed with resin are used.

The unidirectional fiber prepreg used in the present invention is
It is made by impregnating fibers aligned in one direction with resin. When this is used as the innermost layer, it is usually formed by laminating the fibers in a direction perpendicular to the direction of the honeycomb ribbon. The invention is not limited to this, and the angle between the fiber axis direction and the ribbon direction can be appropriately selected depending on the purpose of use.

There are no particular restrictions on the fibers used for this unidirectional fiber prepreg, as long as their performance is sufficiently satisfactory as a plastic reinforcement, such as steel, metal fibers such as boron, ceramics such as silicon carbide, and alumina. Organic fibers such as fibers, carbon fibers, glass fibers, aramid fibers, polyester fibers, nylon fibers, and polyacrylonitrile fibers are used.

Among these, glass fibers, carbon fibers, and aramid fibers are preferably used from the viewpoint of both panel performance and cost.

The resin to be impregnated into these fibers can be appropriately selected from a wide range of thermosetting resins and thermoplastic resins depending on the purpose. Examples of thermosetting resins include epoxy resins, unsaturated polyester resins, epoxy acrylate resins, diallyl phthalate resins, phenol resins, thermosetting polyimide resins, and melamine resins. Examples of thermoplastic resins include polyethylene and polypropylene. , polyvinyl chloride, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, nylon, polymethyl methacrylate), ABS,
Examples include polysulfone, poly(2,6-dimethylphenylene oxide), polyoxymethylene, polyvinyl heptatide, polystyrene, polyvinyl butyral, and the like.

These resins may be used alone, or two or more may be used in a layered or mixed manner.These resins may contain plasticizers, stabilizers, and other additives to improve their physical properties and moldability. Various additives can be added.

The oriented fabric prepreg used in the laminate of the skin layer in the present invention is the core of the invention, and its use can dramatically improve the adhesion between the laminates. This directional fabric refers to a fabric that has different fiber densities in the longitudinal and transverse directions, and may be denser in either the longitudinal or structural directions. In the present invention, the fiber density ratio in both directions is 98:2 to 60:40, particularly 90:10.
A ratio of 65:35 to 65:35 is preferably used. There are no particular restrictions on the weave structure of such directional fabric prepreg, and plain weave, twill weave, satin weave, flat weave, etc. In order to improve the quality, it is preferable that both sides have an uneven shape. In addition, the outermost layer is made of prepreg, a directional fabric with a high fiber density and a smooth shape on the front side, and a low fiber density and uneven shape on the back side (for example, satin weave, which has a high fiber density in the vertical direction and a smooth shape in the horizontal direction). It is preferable to use such a shape when the fiber density in the direction is low in terms of the smoothness of the surface 8 and the adhesion with the unidirectional fiber prepreg.

Further, in order to balance the physical properties in the longitudinal and lateral directions of the panel, it is preferable that the direction of the unidirectional fiber prepreg and the direction of high fiber density in the directional fabric prepreg be perpendicular to each other. Further, there is no particular restriction on the material of the fabric as long as its performance is sufficiently satisfactory as a plastic reinforcing agent, and various fiber materials normally used for the above-mentioned unidirectional fiber prepreg can be effectively used.

The resin to be impregnated into this directional fabric prepreg is as follows:
Depending on the purpose, thermosetting resins and thermoplastic resins can be appropriately selected and used, and examples thereof include various resins used for the unidirectional fiber prepreg described above.

Note that the interlayer adhesion effect due to the use of directional fabrics is particularly noticeable when the resins of each prepreg layer are different.
, the combination of phenolic resin and epoxy resin surprisingly improves the interlayer adhesion strength.

Furthermore, as for the resin of the prepreg used for the innermost layer of the skin layer in contact with the intermediate porous material, an epoxy resin is preferably used since the adhesion between the prepreg and the porous material is important.

The skin layer in the sandwich panel of the present invention is composed of an alternating laminate of the above-mentioned unidirectional fiber prepreg and directional woven fabric prepreg, and the forming of such a panel is carried out by stacking the prepreg and the intermediate porous layer in a predetermined order. This is carried out by laminating flexible materials and using a press method or an autoclave method. In this case, the required pressure and temperature depend on the type of resin and the type of porous material, but molding can be carried out within the pressure and temperature range of commonly used methods.

Effects of the Invention The sandwich panel of the present invention is a structural material that is lightweight and has excellent toughness, especially peeling resistance between each layer in the skin layer, and can be used as, for example, various aircraft materials, robot materials, parabolic antenna materials, etc. It can also be effectively used for flooring and wall materials.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Each resin listed in Table 1 was used as it was, or after being dissolved or diluted with a solvent as necessary, impregnated into a oriented glass satin fabric (warp to weft ratio of 8:2) and dried. A oriented glass satin fabric prepreg was obtained as the outer layer. In addition, for comparison, a unidirectional glass fiber prepreg (for outer layer) was created by impregnating a unidirectional glass fiber roving with the resin or resin solution described above. The basis weight of resin and glass fabric or glass fiber is 100 each.
g/milk 2 and 27Q, 9/m2.

On the other hand, the inner layer of the sandwich panel skin layer is made of unidirectional glass fiber roving, 70 parts by weight of diglycidyl ether type epoxy resin of bisphenol A with an epoxy value of 188, and 30 parts by weight of a curing agent, respectively. 23% by weight of 4,4' based on the resin.
-Diamino Schiff A curable composition impregnated with nylmethane was used. The fabric weight of the glass fiber and epoxy resin of this product is 250 ji/m each.
2 and 150 I/m2. In addition, as a porous material, honeycomb core [manufactured by Hexel Co., Ltd., HRH1o-/8-3.0]
(2) ) was used.

Regarding the construction of the sandwich panel, an intermediate honeycomb core was sandwiched between the panels, and a unidirectional glass fiber epoxy resin prepreg was used as the inner layer, and a directional glass satin fabric prepreg or a unidirectional glass fiber prepreg was used as the outer layer.

At this time, the unidirectional glass fiber prepreg used for the inner layer has its fiber direction perpendicular to the ribbon direction of the honeycomb, while the direction of the oriented glass satin fabric prepreg used for the outer layer is such that the direction of high fiber density is in the direction of the honeycomb ribbon. When using unidirectional glass fiber prepreg for the outer layer, the fiber direction was laminated parallel to the honeycomb ribbon. In addition, when laminating the oriented glass satin fabric prepreg, care was taken so that the smooth side of the satin fabric would appear on the panel and surface.

Panel molding was carried out using a hot press method under a pressure of 3 kg/an2, with the press temperature being the same for the first stage at 120°C (1 hour), and the second stage being at a temperature of 120°C (1 hour), depending on the resin used. A suitable temperature of 120° C. or higher was selected accordingly, and molding was continued under pressure for 1 hour if the outer layer matrix resin was a thermosetting resin, and for 5 minutes if the outer layer matrix resin was a thermoplastic resin.

Next, after cooling, a 300×75ff sample was cut out so that the longitudinal direction of the sample matched with the direction of the core ribbon, and a climbing drum peel test and a three-point bending test were performed. The results are also listed in Table 1.

From Table 1, it can be seen that when a directional fabric prepreg is used as the outer layer, extremely high interlayer adhesive strength can be obtained without deteriorating the bending properties, compared to when a unidirectional fiber prepreg is used.

Example 2 Example 2 except that a plain weave fabric of various fibers listed in Table 2 (width-width fiber density ratio 7:3, basis weight 2 (SOl/m2)) was used as a substitute for the oriented glass satin fabric in Example 1. Sandwich panels were made in exactly the same manner as in 1, and each test was conducted.In addition, for comparison, unidirectional fiber prepreg (for outer layer, basis weight 2509 /
m2) Panels were similarly prepared and each test was conducted. The results are also listed in Table 2.

Table 2 This table shows that when a oriented plain weave prepreg is used as the outer layer, a significantly higher riming drum peel strength is obtained compared to when a unidirectional fiber prepreg is used, and the oriented woven fabric has an effect on improving interlayer adhesion strength. The effect was clearly recognized. Further, when compared with Example 1, it can be seen that even with the same directional fabric, the satin fabric exhibits a better effect on interlayer adhesion than the plain fabric.

Example 6 The honeycomb core in Example 1 had an apparent specific gravity of 0.
．． 25 phenolic resin foam sheet (thickness 1ON) and a polyether sulfone porous membrane with an apparent specific gravity of 0.30 (
Sandwich panels were made using the same oriented glass satin fabric/phenolic resin prepreg as the outer layer as in Example 1, and the same climbing drum beer test was performed, and the strength was 43 kg and 45 kg, respectively. Ta.

In addition, for comparison, a panel was prepared using unidirectional fiber/phenolic resin prepreg as an outer layer and a climbing drum beer test was performed, and the strength was 8.0 kg and 7.0 #, respectively.

Example 4 Various glass satin fabrics with different warp fiber densities and weft fiber densities with a basis weight of 250:9/m2 were coated with phenolic resin (with a basis weight of 12
A prepreg was prepared by impregnating it with 0II/-, and this was used as the outer layer of the skin to prepare a sandwich panel in the same manner as in Example 1. These samples were subjected to the climbing drum beer test and the bending and bending tests according to the method described in Example 1. A strength test was conducted. The results are shown in the drawing as a graph showing the relationship between the percentage of weft fiber density (chi), climbing drum beer strength (solid line) and bending strength (dashed line).In the drawing, the horizontal axis represents the percentage of weft fiber density; The vertical axis shows the climbing drum beer strength, and the right vertical axis shows the relative value of the bending strength.

Example 5 A Kepler (manufactured by DuPont) fabric having a basis weight of 20097 m'' and a ratio of warp fiber density to weft fiber density of 7:3 was impregnated with the epoxy resin described in Example 1 (epoxy resin basis weight 1).
00 g/m2) oriented Keplerian woven prepreg (on the other hand, a unidirectional glass fiber roving with a basis weight of 1 Bog/rn" was impregnated with epoxy acrylate (epoxy acrylate basis weight 80 g/m2) to produce a unidirectional glass fiber. Created prepreg.

Next, as a porous material, honeycomb core [manufactured by Hexel,
HRH10-1/l, -5,0(2)) was used as the skin layer, and (1) (outer layer) glass fiber prepreg/Kev 2-woven prepreg (inner layer) (2) (outer layer) glass fiber prepreg/Keplar fabric. A panel was made according to Example 1 with the following composition: prepreg/glass fiber prepreg/Keplar woven prepreg (inner layer).

At this time, the Kepler fabrics were laminated so that the longitudinal direction was perpendicular to the direction of the core ribbon and the direction of the glass fibers coincided with the direction of the core ribbon.

The interlayer adhesion between the glass fiber prepreg and the Keplerian fabric prepreg was evaluated using the climbing drum method according to Example 1 (in the case of (2) above, between the second layer and the third layer). The adhesive strength was 43, 9 and 45, respectively, showing extremely high values.

[Brief explanation of the drawing]

The drawings show the ratio of the horizontal fiber density of the glass satin fabric of the fabric prepreg, the climbing drum beer strength, and It is a graph which shows the relationship with the relative value of bending strength.

Claims (1)

[Claims] 1. A sandwich panel consisting of a porous material in the middle and a fiber-reinforced plastic laminate in which the skin layers on both sides are made of a laminate of fiber-reinforced plastics, characterized in that the skin layers are made of an alternating laminate of unidirectional fiber prepreg and directional fabric prepreg. panel.