JPH0735065B2 - Method for producing resin-based fiber-reinforced composite material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a resin-based fiber-reinforced composite material suitable for applications requiring high specific strength and high specific elastic modulus. More specifically, the present invention relates to a method for producing a resin-based fiber-reinforced composite material suitable for applications in which a large specific bending strength and specific bending elastic modulus are required.

[Conventional technology]

In the field of so-called advanced composite materials, materials having high strength, elastic modulus, and specific strength and specific elastic modulus obtained by dividing these by specific gravity are desired. Particularly in recent years, the development of the aviation / space industry has been remarkable, and in the electric / electronic industry, the automobile industry, etc., there is an increasing need for materials that are lightweight and can be used at high temperatures. Fiber-reinforced composite materials are useful materials to meet such demands. Among them, resin-based fiber-reinforced composite materials, so-called fiber-reinforced plastics (hereinafter referred to as FRP), have excellent specific rigidity due to their light weight. It is considered to be useful as a material.

Generally, various methods are used for FRP molding, and the length of the reinforcing fiber used is also various, and molding is performed according to each application. As a method for producing FRP using long fibers, there are methods such as hand layup, filament winding, prepreg cloth, etc., but in any method, it is necessary to impregnate the reinforcing fiber with a matrix resin and mold it. Therefore, a suitable production method is selected according to the required characteristics and the number of products to be produced.

The mechanical properties such as strength, elastic modulus and impact strength of the FRP produced in this way depend largely on the length and filling rate of the fiber used for the purpose of strengthening the FRP. If it is increased, the mechanical properties can be improved accordingly. The various molding methods as described above can provide high filling of long fibers and can obtain relatively excellent ones in terms of mechanical properties, but generally have a problem in that the molding time is long and the productivity is high. It can be said that there is.

On the other hand, in the resin injection molding method, a sheet-shaped reinforcing fiber base material that is not impregnated with resin is laminated and filled in the cavity space formed by the male mold and the female mold, and then the resin is pressed into the cavity space. It is a molding method in which the base material is impregnated with the resin and the resin is cured, and it can be said that it is a method having excellent productivity as a molding method of the resin-reinforced composite material in view of its simplicity and the like. However, this method has a drawback that the filling rate of the fibers cannot be increased unnecessarily in order to perform good resin impregnation.

In addition, since the reinforced fibers used in ordinary fiber-reinforced composite materials have a larger specific gravity than the matrix resin, it is important to increase the filling rate of the fibers unnecessarily to increase the specific gravity of the molded product after compounding. FRP
It may also impair the lightness, which is one of the characteristics of the.

[Problems to be solved by the invention]

An object of the present invention is to solve the above problems in the production of conventional resin-based fiber-reinforced composite materials, and to provide a method for producing a resin-based fiber-reinforced composite material in which reinforcement by reinforcing fibers is carried out in a curable manner. .

[Means for solving problems]

The inventors of the present invention have completed the present invention that achieves the above-mentioned object as a result of earnest studies in view of such actual circumstances.

That is, according to the present invention, when producing a resin-based fiber-reinforced composite material in which the matrix resin (A) and the reinforcing fiber (B) consisting of long fibers are essential, the thickness corresponding to 1/3 of the material thickness is used. For reinforcing so that the volume content a of the reinforcing fibers (B) contained in both surface layers and the volume content b of the reinforcing fibers (B) contained in the entire material satisfy a / b ≧ 1.05. The present invention relates to a method for producing a resin-based fiber-reinforced composite material, which comprises presetting a fiber (B) in a molding die in advance and performing resin injection molding.

As the matrix resin (A) used in the present invention,
Examples thereof include a thermosetting resin and a resin in which a thermosetting resin and a thermoplastic resin are mixed. The thermosetting resin used in the present invention is not particularly limited as long as it is a resin that is cured by heat, light, an electron beam or other external energy to at least partially form a three-dimensional cured product.

Preferred thermosetting resins include epoxy resins, maleimide resins and polyimide resins, as well as resins having vinyl terminals, acetylene terminals, allyl terminals, nadic acid terminals or cyanate ester terminals. These can generally be used as a mixture of these resins,
It may be used in combination with a curing agent or a curing catalyst as appropriate.

As the matrix resin (A) used in the present invention, it is also preferable to use a mixture of the above-mentioned thermosetting resin and a thermoplastic resin. As the thermoplastic resin suitable for the present invention, polyacrylate, polyamide, polyester, polycarbonate, polyarylate, polyphenylene sulfide,
Engineering plastics such as polyimide, polyether imide, polysulfone, polyether sulfone, polyether ether ketone, polybenzimidazole can be mentioned. These thermoplastic resins may be polymers or oligomers having a slightly low molecular weight, and oligomers having a functional group capable of reacting with the thermosetting resin at the terminal or in the molecular chain are also preferable.

A mixture of thermosetting resin and thermoplastic resin may give better results than using the thermosetting resin alone. This is because while thermosetting resins generally have the disadvantage of being brittle, low-pressure molding is possible, while thermoplastic resins generally have the advantage of being tough, but low-pressure molding is difficult. This is because, since they have, it is possible to balance the physical properties and the moldability by mixing and using these.

Examples of the reinforcing fiber (B) used in the present invention include fibers that are generally used as an advanced composite material and have good heat resistance and tensile strength. Examples thereof include carbon fiber, graphite fiber, organic fiber, silicon carbide fiber, alumina fiber, boron fiber, tungsten carbide fiber, and glass fiber.
Only one type of reinforcing fiber may be used, or two or more different types of reinforcing fibers may be used in combination. The characteristics of the obtained composite material differ depending on the material and shape of the reinforcing fiber, but regardless of the material of the reinforcing fiber, as the length of the fiber increases, the reinforcing effect with the same amount of fiber increases, so high reinforced In order to obtain the effect, it is preferable to use mainly continuous fibers.

In the present invention, when the continuous fiber as described above is used, the direction in which the fibers are arranged is important. Generally, the effect of fiber reinforcement is such that the maximum effect can be obtained in the direction of the fiber axis, and no significant effect can be expected in the direction perpendicular to the direction, but reinforcement in only a single direction is desired. In some cases, the most effective method is to align straight fibers having substantially no bending into parallel sheets. Further, such sheet-like fibers can be reinforced in a plurality of directions by stacking them at different angles. On the other hand, when it is not desired to reinforce in a specific direction and it is desired to reinforce almost uniformly in all directions, it is preferable to use substantially continuous fibers in a swirl mat shape.

In the present invention, a resin injection molding method is used to manufacture a resin engaging member fiber reinforced composite material using the above-mentioned components, and at that time, mechanical properties of the material, particularly bending properties are improved. Therefore, different reinforcement methods are used for the vicinity of the surface and the vicinity of the center of the material, that is, a reinforcement method for increasing the rigidity of the surface vicinity layer more than the rigidity of the center vicinity layer.

When bending stress is applied to a material, the rigidity of the surface layer is more dominantly related to the rigidity of the surface layer than the rigidity of the central layer.
According to the present invention, the fiber content contained in both surface layers having a thickness corresponding to 1/3 of the wall thickness of the material is set to be higher than other portions (1/3 portion of the remaining central layer). However, the specific gravity of the material can be reduced because the rigidity of the surface layer can be secured and the fiber content can be suppressed to a lower level in the material as a whole.

In the present invention, the volume content a of the reinforcing fibers contained in both surface layers each having a thickness corresponding to 1/3 of the wall thickness of the material, and the volume content b of the reinforcing fibers contained in the entire material, If the relation of is shown, a / b ≧ 1.05. More preferably a / b
The ratio of is in the range of 1.05 to 1.5. This is because if a is relatively smaller than this, the effect of reducing the specific gravity of the material becomes substantially meaningless. Further, in order to sufficiently fulfill such an object, it is preferable to further increase the fiber content in a portion closer to the surface, and a layer having a high fiber content is provided in a portion closer to the center than 1/3 of the wall thickness. Even if they are arranged, it is difficult to obtain the effect. If the molded body is a hollow rod-shaped body such as a triangle, quadrangle, polygon or circle, the outer side 1 /
It suffices that there is a relationship of a / b ≧ 1.05 between the volume content a of the thickness layer of 3 and the volume content b contained in the entire material, and the volume content a of the inner surface layer 1/3 thickness is particularly problematic. do not become.

In the present invention, there is no particular limitation on the method for increasing the volume content of the fibers contained in the surface layer to be higher than the volume content of the fibers contained in the entire material, but the fibers are more closely packed by paralleling each other. Since it can be filled, it is an effective means to make the reinforcing fibers existing in the surface layer, as described above, in a state where straight fibers having substantially no bending are parallel to each other and aligned in a sheet shape. .

On the other hand, by forming a substantially continuous fiber into a swirl mat and arranging it in the vicinity of the center layer, it is possible to prevent the reinforcement of the material from being biased only in a certain direction, improve the impregnation of the matrix resin, etc. Is effective, and adopting such a method is also an effective means.

The amount of the reinforcing fiber used in the present invention is not particularly limited, but in order to fully utilize the effect of the present invention, the volume content of the reinforcing fiber contained in the entire material is 10 to 70%. Is preferable, and particularly preferably 20 to 60%.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

The matrix resin (A) and reinforcing fiber (B) used are as follows.

Matrix resin (A): A-1: Bisphenol A diglycidyl ether type epoxy resin ... "Epicoat 82" manufactured by Yuka Shell Epoxy Co., Ltd.
8 ”(hereinafter abbreviated as E828).

A-2: ethylene glycol dimethacrylate ... (hereinafter,
Abbreviated as EGDMZ).

A-3: Methyl nadic acid anhydride ... “Merryl hymic acid anhydride” manufactured by Hitachi Chemical Co., Ltd. (hereinafter abbreviated as MNA).

A-4: Benzylmethylimidazole ... “BMI-12” manufactured by Yuka Shell Epoxy Co., Ltd. (hereinafter abbreviated as BMI).

A-5: t-butyl peroxybenzoate ... “Perbutyl Z” manufactured by NOF CORPORATION (hereinafter abbreviated as t-BPB).

Reinforcing fiber (B): ・ Roving mat A ... "Lami mat" manufactured by Nitto Boseki Co., Ltd.
Part of the robing mat layer part is used.

Basis weight 600g / m ² · Swirl mat… Asahi Fiberglass Co., Ltd. “Continuous Strado mat”.

A basis weight of 600 g / m ² Examples 1 and 2 and Comparative Examples 1 and 2 A matrix resin (A) having each component ratio shown in Table 1 and a reinforcing fiber (B) shown in Table 2 were laminated. A resin-based fiber reinforced composite material was produced by the following method in combination with a reinforcing material.

That is, using a reaction injection molding machine having two injection lines, the reinforcing material was preset in the mold, and the matrix resin was injected in 2 to 3 seconds.
It was cured at ℃ for 20 minutes to prepare a 270 × 220 × 3 mm flat plate fiber-reinforced composite material. At that time, the mixture of the components (A-1) and (A-2) was supplied from one injection line, and the components (A-3), (A-4) and (A-5) were supplied from the other injection line. The mixture was injected, and each resin raw material was degassed under reduced pressure before the injection. The pressure inside the mold is kept at a reduced pressure by a vacuum pump before injecting the resin raw material, and 2 kg /
The pressure was increased to cm by nitrogen gas.

The numerical values of a and b of each material in the above Examples and Comparative Examples were calculated as follows.

(Example) 1) By observing the cross section of the material, the thickness dr (cm) of the roving mat-containing layer and the thickness ds (cm) of the swirl mat-containing layer
To measure.

2) The fiber volume content Vr of the roving mat-containing layer and the fiber volume content Vs of the swirl mat-containing layer are calculated by the following formulas.

Vr = {Amount of fiber in roving mat containing layer (g / c
m ² ) / Fiber density (g / cm ³ )} / dr Vs = {Fabric unit weight in the swirl mat-containing layer (g / cm ² ).
/ Density of fiber (g / cm ³ )} / ds 3) a and b are calculated by the following formula.

b = {Fabric unit weight (g / cm ² ) / fiber density (g / cm ³ )} / d (d; material thickness) (comparative example) a = b = {total material Fiber weight per unit area (g / cm ² ) / fiber density (g / cm ³ )} / d The characteristic test of the fiber-reinforced composite materials produced in Examples 1 and 2 and Comparative Examples 1 and 2 was performed. The results are shown in Table 3.

[Effects of the Invention] As described above, according to the method for producing a resin-based fiber-reinforced composite material of the present invention, a resin-based fiber-reinforced composite material having both excellent mechanical properties and lightweight can be easily produced. it can. Further, the resin-based fiber reinforced composite material produced by this can have various levels of property setting by appropriately selecting the reinforcing material to be used, and it can be expected to be widely applied in the field of advanced composite materials.

Claims (3)

[Claims] 1. When manufacturing a resin-based fiber-reinforced composite material which essentially comprises a matrix resin (A) and a reinforcing fiber (B) consisting of long fibers, the resin-based fiber-reinforced composite material has a thickness corresponding to 1/3 of the thickness of the material. Reinforcing fibers such that the volume content a of the reinforcing fibers (B) contained in both surface layers and the volume content b of the reinforcing fibers (B) contained in the entire material satisfy a / b ≧ 1.05. A method for producing a resin-based fiber-reinforced composite material, which comprises presetting (B) in a molding die in advance and performing resin injection molding. 2. A reinforcing material formed by aligning straight fibers having substantially no bending in parallel with each other in a sheet shape is present in both surface layers having a thickness corresponding to 1/3 of the thickness of the material. The manufacturing method according to claim 1, wherein presetting is carried out in a molding die. 3. A swirl mat-shaped reinforcing material of substantially continuous fibers is preset in a molding die so as to be present in a central layer corresponding to 1/3 of the wall thickness of the material. Item 3. The manufacturing method according to Item 1 or 2.