JPS6258285B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a fiber reinforced composite material. There are various manufacturing methods for fiber-reinforced composite materials, such as the hand lay-up method, cold press method, matte die method, and SMC method, but in recent years, uncured thermosetting resin has been added to a resin foam sheet with an open cell structure. A manufacturing method for fiber-reinforced composite materials has begun to attract attention, in which resin is impregnated, a fiber-reinforced composite material is placed thereon, the material is inserted into a press mold, and the fiber-reinforced material is cured while being impregnated with resin under pressure and heat.

This manufacturing method requires a pressurizing force of 2 to 10 kg/cm ³ and SMC
80Kg/cm ³ It can be molded at lower pressure than the pine die method (30Kg/cm ³ etc.), and the molded product is a sandwich die method in which a highly rigid fiber-reinforced layer is located on the outside and a lightweight, less rigid hardened foam sheet layer is located on the inside. This makes it possible to increase the specific rigidity and specific strength of the structure compared to other manufacturing methods, making it the ideal method for reducing weight.
Suitable for bumpers, oil pans, etc. and panel materials.

Conventionally, thermoplastic resin foam, urethane foam, etc. have been used for the resin foam sheet with an open cell structure produced by this manufacturing method, and glass mat, glass cloth, etc. have been generally used for the fiber reinforcement material. However, in these cases, since the rigidity and strength of the inner cured foam sheet layer during curing were low, there was a problem that the inner foam sheet layer peeled off during demolding and swelled to the outside.
Particularly when molding a thick product of 5 mm or more, this blistering phenomenon frequently occurs, making it difficult to manufacture the product. In order to prevent this, attempts have been made to improve the rigidity of the foam sheet layer by adding short fibers to the resin, but this has not been very effective and the thickness has been limited to only 2 to 3 mm, which is a fatal problem with this manufacturing method. It was a dot.

The feature of this manufacturing method is that the cells of a resin foam sheet with an open cell structure are impregnated with resin, and the foam sheet is compressed to extrude the resin, which is then impregnated into a fiber reinforced material and molded. The sheet plays an important role in resin retention and fluidity. However, as long as a resin foam sheet is used, it has been recognized that there is a limit to eliminating blisters by increasing the rigidity of the foam sheet layer when cured.

Therefore, the present invention proposes a new manufacturing method that allows molding at low pressure without using the conventionally used resin foam sheet with an open cell structure.

The present invention involves impregnating a non-woven glass sheet material with a bulk density of 0.008 to 0.2 g/ ^cm3 , elasticity and continuity of pores with an uncured thermosetting resin, and coating one or both sides of the sheet material with an uncured thermosetting resin. arranging the fiber reinforcement, compressing the sheet material and the fiber reinforcement until the thermosetting resin is sufficiently impregnated into the sheet material and the fiber reinforcement, and curing the thermosetting resin while maintaining the compression. This is a method for manufacturing a fiber-reinforced composite material.

In this manufacturing method, for example, inorganic fibers to which epoxy resin, phenolic resin, etc. are attached as a binder are made into a non-woven sheet material with elasticity and pore continuity and a bulk density of 0.008 to 0.2 g/ ^cm3 . It is unique in that it is used instead of a resin foam sheet with an open cell structure. The characteristics of this non-woven sheet material made of inorganic fibers include resin impregnation,
It has good fluidity, retention, and elasticity. For this reason, elasticity and pore continuity are required. Examples of such nonwoven sheet materials include glass wool sheets used for heat insulating materials and the like.

A glass non-woven sheet material is impregnated with an uncured thermosetting resin, such as an epoxy resin or a polyester resin, and one or both surfaces of the non-woven sheet material are impregnated with a fiber reinforcing material such as glass fiber, carbon fiber, Kevlar fiber, etc. Arrange mats, crosses, etc. Alternatively, a fiber reinforcing material may be placed on one or both sides of the nonwoven sheet material and then impregnated with an uncured thermosetting resin. Then, the nonwoven sheet material and the fiber reinforced material are inserted into a press mold, and heated and pressed at a low pressure of 2 to 10 kg/cm ³ . When pressurized, the resin in the nonwoven sheet material flows and impregnates the entire nonwoven sheet material and fiber reinforcement,
Pressure and heat are maintained until the resin hardens, and after hardening, the mold is removed and the product is made. Since the nonwoven sheet material has elasticity, this composite material can be molded to follow the curved surface of a mold.

In the conventional matte die method, a pressing force of about 30 kg/cm3 ^or more was required because the preformed glass mat has low elasticity and resin retention, but when this nonwoven sheet material is used, it has an open cell structure. Same as resin foam sheet with 2~10Kg/ ^cm3
Can be molded with the pressure of Compared to resin foam sheets, the non-woven sheet material not only has good resin retention, fluidity and elasticity, but also has inorganic fibers such as glass fibers, so even after the resin hardens, the compressed glass fibers will not harden. It serves as a reinforcing material for the sheet layer.
Unlike conventional resin foam sheets with an open cell structure, this does not reduce the strength and elastic modulus of the cured sheet layer and cause blistering. In this way, the nonwoven sheet material not only functions as a resin foam sheet, but also improves the strength of the sheet layer after curing.
It has a major feature of improving the elastic modulus and preventing the product from blistering during molding. Composite materials made using conventional resin foam sheets are not only prone to blistering, but even when blistering does not occur, when subjected to bending tests, the hardened sheet layer may peel under a predetermined load or less. , peeling easily occurred at the interface between the cured sheet layer and the outer fiber reinforced layer, resulting in low reliability of product strength and making it difficult to use in fields that required stable strength. However, when the nonwoven sheet material is used, it does not cause blistering or peeling, and its strength is highly reliable, so it can be safely applied to fields that require strength.

Glass nonwoven sheet materials have not been used in the field of fiber-reinforced composite materials until now, but such materials include glass wool sheets, among which materials with bulk densities of 0.008 to 0.2 g/ ^cm3 are available. It has good resin impregnation and is highly elastic, making it suitable for use. However, materials lighter than this have weak elasticity, and heavier materials are difficult to impregnate and have poor resin retention properties, making them unsuitable for use. The thickness of the nonwoven sheet material may vary depending on the required characteristics of the final product, but is generally preferably about 5 to 50 mm.

Furthermore, the fiber-reinforced composite material produced by the manufacturing method of the present invention has a sandwich structure consisting of an outer fiber-reinforced layer with a high fiber content and high strength and elastic modulus, and an inner hardened sheet layer with a light specific gravity. Therefore, by lowering the specific gravity of the inner hardened sheet layer, the specific strength and specific elasticity of the composite material can be further increased. However, the air in the cured sheet layer is forced out by the flow of the resin during compression, making it look like there are no holes.In order to lower the specific gravity of the cured sheet layer, hollow microballoons are inserted into the thermosetting resin.
For example, glass micro balloons, glass balloons, etc. may be included, and it is effective to add 5 to 20 parts by weight per 100 parts of resin. Due to the resistance of the fibers of the fiber-reinforced material, the micro balloons do not penetrate inside the reinforcing material, so they are less likely to reduce the strength and elastic modulus of the fiber-reinforced layer, and they are less likely to come out to the outside and worsen the appearance. There are advantages.

In addition, low shrinkage agents, internal mold release agents,
It is also possible to appropriately blend pigments, fillers, etc.

Next, an example will be described.

Example 1 Glass wool 1 with bulk density 0.02 g/cm ³ and thickness 20 mm, hardening agent and micro glass balloon 10% by weight
6 polyester resins per ^1m2 of surface area.
A glass mat 2 weighing 450 g/m ² is placed on both sides of the mat, placed in a mold 3, and hardened under pressure and heat.

The pressure is applied at a surface pressure of 4Kg/cm ³ , a mold temperature of 130℃, and a pressurization time of 5 minutes.The thickness of the composite material after curing is approximately 5mm.
It is.

Comparative Example (Conventional Example) Instead of glass wool, an open-cell urethane foam with a specific gravity of 0.02 and a thickness of 20 mm was impregnated with the same resin as in the example and molded under the same conditions. Compare the results of both molded products.

In the examples, none of the samples were blistered during molding, and the bending strength was approximately 20 kg/mm ² with little variation, and the sample broke from the outer glass fiber reinforced layer.
Approximately 80% of the comparative examples (conventional examples) blistered during molding, and for those that did not blister, the bending strength was as low as approximately 10 Kg/mm ² and had a large variation, with peeling occurring from the center of the cured sheet layer. It became a low value.

[Brief explanation of the drawing]

FIG. 1 shows how a glass mat, resin-impregnated glass wool, and glass mat are placed on a mold, pressurized, and heated. Explanation of symbols, 1...Resin-impregnated glass wool, 2
...Glass mat, 3...Mold.

Claims (1)

[Claims] 1. A glass nonwoven sheet material having a bulk density of 0.008 to 0.2 g/cm ³ and having elasticity and pore continuity is impregnated with an uncured thermosetting resin, and one side of the sheet material is impregnated with an uncured thermosetting resin. Alternatively, fiber reinforcement is placed on both sides, the sheet material and the fiber reinforcement are compressed until the thermosetting resin is sufficiently impregnated into the sheet material and the fiber reinforcement, and the thermosetting resin is applied while maintaining the compression. A method for producing a fiber-reinforced composite material, which comprises curing the material. 2. The method for producing a fiber-reinforced composite material according to claim 1, wherein the glass nonwoven sheet material is a glass wool sheet. 3. The method for producing a fiber-reinforced composite material according to claim 1 or 2, wherein the thermosetting resin is a resin containing hollow microballoons.