JPH032652B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a molding method and a molding die for reinforced plastic materials, and particularly to compression molding of materials by utilizing the expansion and contraction action of shape memory alloys.

In recent years, reinforced plastics, especially fiber-reinforced plastic composite materials (hereinafter referred to as FRP), have become increasingly popular.
Because the molded product is lightweight and has high strength, as well as excellent insulation and corrosion resistance, it has become a popular choice for industrial structural materials and household goods, replacing conventionally used materials such as metal, wood, and ceramics. It is used in a wide range of fields. By the way, as the practical use of FRP molded products has spread, various molding methods have been developed, and the currently mainstream methods include the hand wrap method and the compression molding method. The most commonly used compression molding methods are mated die molding and bag molding.

In this matt die molding method, the molding material is
The material is filled into the cavity of a pair of compression molds, and is then pressurized and heated using a pressure machine such as a press to form a desired shape. This method allows molding of relatively small and complex-shaped articles, and has favorable productivity. However, special consideration is required, such as a pressurizer for pressurizing the mold, a heater housed in the mold for heating, or a heating plate attached to the pressurizer. In addition, when molding a complex shape with many irregularities using a molding material with relatively poor fluidity, such as a continuous fiber reinforced molding material or a cross-woven reinforced molding material, filling defects may occur or reinforcing fibers may partially break. There were some drawbacks such as being exposed.

On the other hand, the bag molding method uses either a male mold or a female mold to spread the prepreg material or base material on the mold, and then laminates the molding material using Handle Tap, which impregnates the base material with resin. It is a method of heat forming under vacuum or pressure while covered with a heat-resistant film to provide airtightness, and is used for large molded products having a hemispherical or relatively simple shape. A homogeneous molded product with a small bubble content can be obtained. However, in this case, a large-scale decompression device and pressurization device such as a vacuum pump to remove air from the bag and an autoclave to pressurize the bag are required, and the molding operation is complicated. Furthermore, when molding a molded product having a complex shape with many irregularities, there were problems in the molding process, such as the bag bag not adhering tightly to the molding material laminated on the mold, or the bag bag tearing, resulting in insufficient pressure.

This invention was made in order to eliminate the drawbacks of the conventional products as described above, and it is possible to mold prepregs with poor fluidity by a simple method without requiring large-scale processing equipment or decompression equipment. The object of the present invention is to provide a material molding method and compression molding mold that can mold even materials into complex shapes.

This invention uses a compression molding mold incorporating a reversible spring-shaped memory alloy, and utilizes the reversible shape change of the spring that occurs by heating and cooling the mold itself. Specifically, it utilizes the shape change in the elongation direction of a shape memory alloy spring due to thermal lattice transformation caused by heating as a compressive force. When demolding, the mold is cooled and the shape memory alloy spring is deformed in the contraction direction by thermal lattice transformation in the opposite direction, and the molded product is released from the mold. This is a compression mold. This eliminates the need for large-scale processing equipment such as a processing machine or a pressure reducer, unlike conventional molding methods, and the molding operation is extremely simple. Furthermore, since the mold does not need to be attached to processing equipment and can be easily disassembled, manual lamination of prepreg materials with poor fluidity is easy, and complex moldings can be molded and demolded. Furthermore, since the entire mold is made of metal, there is no damage to the bag bag, and it is a novel product that can apply sufficient pressure to the corners of the mold.

An embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows the molding die before heating when molding a U-shaped FRP product using fibers as a reinforcing material. 1 is the push die, 2 is the upper plate, and 3 is the upper plate of the push die 1. A spring made of a shape memory alloy whose lower end is housed and locked in a recess 1a, which is an engaging part formed on the surface of the second side, and whose upper end is in contact with the upper plate 2. . 4 is a horizontal plate mold, 5 is a lower plate mold, and 6 is a bolt that connects the upper plate 2, the horizontal plate mold 4, and the lower plate mold 5. A molding material 7 is filled into the cavity within the mold. The shape memory alloy mentioned above is one that remembers not only the shape of the high chamber phase but also the shape of the martensitic phase state under deformation at low temperatures, and its critical temperature
Tc region (temperature region between the high-temperature reverse transformation start temperature As to the parent phase and the low-temperature transformation start temperature Ms to the martensitic phase) between the parent phase and the martensite phase by a heating-cooling cycle outside. A reversible thermal lattice transformation occurs, and the above reversible shape change ←→ can be repeated. The reversible shape memory alloy that has been put into practical use here is
There are Ni-Ti (nitinol), Cu-Zn-Al alloys, etc., and Tc can be made within a temperature range of about 200℃ or less by appropriately changing the blending ratio of the component elements that make up the alloy, heat treatment, processing conditions, etc. You can set the desired temperature.

In designing the shape memory alloy spring 3, the spring 3 is designed to have Tc near the optimum molding temperature of the molding material from the viewpoint of both workability and economy. Therefore, if the spring 3 is heated above the Tc region, it will undergo reverse transformation into a high-temperature phase and deform in the elongation direction into the desired shape, and conversely, if it is cooled to a temperature below the Tc region, it will transform into a low-temperature martensitic phase. It exhibits a reversible shape memory effect in which it transforms into its original shape.

Next, the molding procedure will be explained. First, the lower plate mold 5 and the horizontal plate mold 4 are assembled, and after a predetermined amount of molding material 7 is accommodated in these molds, the push mold 1, the spring 3, and the upper plate 2 are assembled. Note that this assembly may be performed by assembling the horizontal plate mold 4, spring 3, and push die 1 on the upper plate 2 with the upper and lower sides reversed, and then attaching the lower plate mold 5 after storing the material 7. . When the compression mold containing the material 7 in the cavity of the mold is heated to a temperature above the Tc region in an eccentric temperature bath, the shape memory alloy spring 3 transforms into a high temperature phase, so the direction of the arrow in Fig. 2 Due to the deformation, the press die 1 is pushed down and the molding material 7 is compressed. The material then heat-cures over time and can be molded into a predetermined shape. After molding, the compression molding mold is
When the spring 3 is cooled to a temperature below this range, the spring 3 transforms into a low-temperature martensitic phase, deforms in the direction of contraction, and returns to its original shape. Therefore, it is sufficient to remove the molded product from the mold.

In the above molding method, the stress (pressure force) generated when the shape of the spring 3 changes due to thermal transformation is the stress required for molding the material to be molded (usually 0.01 to 0.1 Kg/mm). ² ) Can be designed as desired. That is, the pressing force of the press die 1 is adjusted by adjusting the shape of the spring 3 in the high temperature phase region at a temperature above the Tc region, adjusting the thickness of the spring cross section, and installing a plurality of springs. The molding material is not particularly limited as long as it is suitable for molding, but fibers such as glass, synthetic resins, carbon, woven fabrics or non-woven fabrics, reinforcing materials such as mat and unidirectional length, and suitable curing agents and fillers are used. Preferably, a compound such as prepreg SMC or BMC is impregnated with a thermosetting resin blended in a certain ratio and made into a semi-cured state. However, thermoplastic resin materials or resin and rubber compositions may be used if desired. Further, the molding method and compression molding mold of the present invention can be widely applied not only to the molding process of materials, but also as a molding method and molding mold for correcting thermal strain caused in the thermosetting process and age hardening process.

As described above, according to the present invention, there is no need for large-scale pressurizing equipment or depressurizing equipment as in conventional molding methods, and the molding operation is extremely simple, and the mold can be attached to the pressurizing equipment. Since there is no need to do this and disassembly is simple, it is easy to manually stack prepreg materials with poor fluidity, and it is also possible to mold products with complex shapes. Furthermore, since the mold itself is made of metal, there is no fear of film breakage during bag molding, and the mold can be used repeatedly.Furthermore, the corners of the mold are also sufficiently pressurized, so the pressure distribution is uniform. It is also extremely useful industrially, as it allows for uniformity and stabilization of quality.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the molding die before heating, and FIG. 2 is a cross-sectional view of the molding die during heating. 1...Pushing die, 2...Upper plate, 3...Shape memory spring, 4...Horizontal plate die, 5...Lower plate die, 7
...Molding material. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A molding material that is solid or semi-solid at room temperature and is made of an FRP molding material such as prepreg, SMC or BMC, or a thermoplastic resin or a rubber composition,
Using a compression molding die equipped with a push die incorporating an alloy spring having a shape memory effect, the molding material is softened or fluidized in a high temperature atmosphere, and the alloy spring having a shape memory effect undergoes thermal transformation. A material forming method characterized by heat-pressing forming into a predetermined shape using elongation as forming pressure. 2. A push die 1 placed in a space surrounded by the upper plate 2, the lower plate die 5, and the horizontal temporary die 4 on the 4 sides.
and an engaging part formed on the surface of the upper plate 2 side of the press die 1, one end of which is engaged with the engaging part, and the other end of which is in contact with the upper plate 2, shrinks at room temperature, and A compression molding die comprising an alloy spring having a shape memory effect that deforms in the elongation direction at high temperatures, and a cavity surrounded by the pusher die 1, the horizontal plate die 4, and the lower plate die 5.