JP7220448B2 - METHOD FOR MANUFACTURING FIBER REINFORCED COMPOSITE - Google Patents

Description

The present invention relates to a method for producing a fiber-reinforced composite material using a chopped strand prepreg in which reinforcing fibers are impregnated with a thermoplastic resin.

A fiber-reinforced thermoplastic resin prepreg having a thermoplastic resin (CFRTP) as a matrix includes a prepreg using chopped strands (chopped strand prepreg). This is a strip-shaped prepreg obtained by cutting a unidirectionally arranged strand (fiber bundle) having a thermoplastic resin as a matrix into fiber lengths of about 25 mm to 50 mm, for example. Such a prepreg has good fluidity during molding, for example, fluidity during stamping molding, and is suitable for thermoplastic press molding of FRP molded products having various complicated shapes (see Patent Documents 1 to 6).

JP-A-9-155862 JP-A-2-143810 JP-A-7-164439 Japanese Patent No. 4161409 JP 2009-114612 A JP 2010-235779 A

In conventional thermoplastic press molding, it was necessary to apply high pressure in a relatively low viscosity range in order to impregnate reinforcing fibers with resin in the press mold during molding. For this reason, the resin flow during molding causes uncontrollable disturbances in fiber orientation, which causes problems such as variations in product strength and difficulty in manufacturing thin FRP molded products. rice field.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for producing a fiber-reinforced composite material that suppresses voids between fibers and variation in product strength and facilitates press molding of thin FRP molded products.

In order to solve the above-mentioned problems, the method for producing a fiber-reinforced composite material of the present invention is a prepreg having a predetermined thickness by laminating chopped strand prepregs in which reinforcing fibers are impregnated with a thermoplastic resin in a two-dimensional random orientation. As a laminate, the prepreg laminate is heated to a complex viscosity of 20 to 1800 [Pa s] and pressed at 1 to 8 [MPa] to form a sheet with a predetermined thickness. Characterized by cooling.

According to the present invention, the plasticity of the thermoplastic resin of the matrix is utilized, and press molding is performed at an appropriate complex viscosity of 20 to 1800 [Pa s] and an appropriate pressure of 1 to 8 [MPa]. Voids can be efficiently removed by permeating the gaps between the prepregs contained in the resin, and an isotropic fiber-reinforced composite material with suppressed variation in physical properties can be produced. Therefore, it can be thermoplastically press-molded to easily produce a thin-walled FRP molded product.

1 is a process chart showing a method for manufacturing a fiber-reinforced composite material according to the present invention; FIG. 1 is a plan view of a carbon fiber reinforced composite material obtained by the present invention; FIG. FIG. 4 is a diagram showing a viscosity curve in the polymerization process of thermoplastic epoxy resin; It is the perspective view (a) and sectional drawing (b) which show deformation|transformation embodiment of press molding.

An embodiment of the process for producing a fiber-reinforced composite material of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of a manufacturing process of a fiber-reinforced composite material.
(1. Reinforcing fiber opening process)
In this process, first, a carbon fiber strand 1 formed by converging a predetermined number of single fibers (carbon fibers) as reinforcing fibers is passed through several guide rollers 3 in a water tank 2 filled with tap water to spread the fibers. to form an open strand 1A. Here, as the carbon fiber strand 1, carbon fiber TC36P-12K (800tex, 12,000 filaments, manufactured by Formosa Plastics Corporation) was used. The thickness of the spread strand 1A is usually preferably 10 to 60 μm as an average thickness from the viewpoint of ensuring sufficient strength of the product and ensuring sufficient impregnation of the thermoplastic resin. . The carbon fiber strand may be untwisted or twisted.

The type of reinforcing fiber is not limited to the carbon fiber mentioned above. Inorganic fibers, organic fibers, metallic fibers, or hybrid fibers combining these can also be used as reinforcing fibers.

Examples of inorganic fibers include carbon fibers, graphite fibers, silicon carbide fibers, alumina fibers, tungsten carbide fibers, boron fibers, and glass fibers. Organic fibers include aramid fibers, high-density polyethylene fibers, other general nylon fibers, polyesters, and the like.

Examples of metal fibers include fibers of stainless steel, iron, and the like, and carbon fibers coated with metal may also be used. Among these, carbon fiber is most preferable in consideration of mechanical properties such as strength of the final molded product.

After preparing the spread strand 1A, the spread strand 1A is passed through a pair of hot rollers 4 to remove moisture and dried. In the embodiment of the present invention, the temperature of the hot roller pair 4 is set to 100.degree. The temperature is not limited to 100.degree. The width W of the dried open fiber strand 1A was 15 mm to 17 mm.

(2. Thermoplastic resin impregnation step)
This step is a step of impregnating the dried spread strand 1A with a thermoplastic resin as a matrix resin. This impregnation may be performed by applying resin from the upper and lower surfaces of the spread strand 1A using a die for discharging the resin, or by immersing the spread strand 1A in a molten bath of thermoplastic resin. good too.

When immersed, a nip roll or the like may be used to adjust the amount of resin adhered to the spread strand 1A. If a solvent is used for impregnation, the solvent may be volatilized after impregnation, and if a reactive resin is used, the resin may be polymerized by heat treatment.

In the example of FIG. 1, a thermoplastic resin is applied as a matrix resin to both upper and lower surfaces of the dried spread strand 1A using a resin ejection die. Then, the spread strand 1A coated with the thermoplastic resin is immediately passed through the release belt pair 5, and the thermoplastic resin coated on both upper and lower surfaces is pressed under heating to impregnate the spread strand 1A and cool it. As a result, a prepreg tape with a high impregnation rate and high smoothness can be obtained.

In the embodiment of the present invention, a thermoplastic epoxy resin (XNR6850V manufactured by Nagase ChemteX Corporation) was used as the thermoplastic resin. Then, 100 parts by weight of the thermoplastic epoxy resin and 8 parts by weight of a curing agent (XNH6850V, manufactured by Nagase ChemteX Corporation) are sufficiently mixed and stirred to form a resin paste, which is applied to both upper and lower surfaces of the spread strand 1A. bottom. The resin paste is applied to both the upper and lower surfaces of the spread strand 1A at a position immediately before the release belt pair 5 so that the resin volume content (Vf) is 40%, and therefore the fiber volume content (Vf) is 60%. do. A doctor blade or a flat nozzle can be used as the application jig. Incidentally, if the fiber volume content (Vf) is in the range of 10 to 80%, sufficient mechanical strength of the fiber-reinforced composite material can be obtained. This thermoplastic epoxy resin is amorphous and is an in-situ polymerizable resin.

Here, the thermoplastic resin is the thermoplastic epoxy resin described above, as well as polyamide resins represented by nylon 6, nylon 12, nylon 66, and nylon 46, polyesters such as polyethylene terephthalate and polybutylene terephthalate. Polyolefin resins such as polyethylene and polypropylene, polyether ketone resins, polyphenylene sulfide resins, polyetherimide resins, polycarbonate resins, and the like can also be used. Characteristics of these resins include crystalline resins, amorphous resins, and in-situ polymerizable resins whose molecular weight increases during the molding process described later.

However, in fields where heat resistance is required, the thermoplastic resin is preferably a polyester-based resin. Polyethylene terephthalate is more preferable especially in fields where heat resistance, mechanical strength, creep properties, chemical resistance and oil resistance are required. Additives such as hydrolysis inhibitors and heat deterioration inhibitors may also be added depending on the purpose.

Furthermore, in fields where cost, fluidity during shaping, water resistance, hot water resistance, and chemical resistance are required, the thermoplastic resin is preferably a polyolefin resin. Polypropylene is more preferable because it is economically excellent.

When abrasion resistance, oil resistance, and long-term heat resistance are required, the thermoplastic resin is preferably a polyamide resin. Nylon 6 is more preferable. In this case, oxidation deterioration may occur when heated in an oxygen atmosphere, for example, so an oxidation deterioration inhibitor or the like can be added depending on the purpose in order to prevent this.

(3. Cutting process of prepreg tape)
In this step, the prepreg tape obtained in the above step is cut to a predetermined length by the cutter 6 to form chopped strand prepreg 1B. In the embodiment of the present invention, the cut length was adjusted so that the volume of the chopped strand prepreg 1B was 33.5 mm ³ (strand length was about 29 mm).

The shape of the chopped strand prepreg 1B is not particularly limited. It may be polygonal or have curved sides. However, a rectangular shape is preferable because manufacturing is simple and efficient. In this case, it is more preferable that one long side of the rectangle is parallel to the fiber axis direction and the other short side is perpendicular to the fiber axis direction. The cutting method is not particularly limited, but a guillotine method, a Kodak method, a pelletizer, a rotary method, or the like can be employed.

(4. Scattering/Lamination Process)
In this step, the required amount of chopped strand prepreg 1B obtained in the above step is scattered and laminated by free fall onto a deposition board 8 arranged below from a spreader 7 to obtain a prepreg laminate 1C. be. In the embodiment of the present invention, the chopped strand prepreg 1B was spread and laminated on the deposition board 8 arranged 300 mm below the spreader 7 so that the sheet basis weight of the prepreg laminate 1C was 1013 g/m ² .

(5. Temporary fastening process)
In this step, the prepreg laminate 1C obtained in the spraying/laminating step is heated with near-infrared rays or far-infrared rays to soften the resin contained in the prepregs, and the chopped strands/prepregs 1B are bonded to each other to form a prepreg laminate. This is the step of fixing 1C. By passing the prepreg laminate 1C between the pressure rollers 9, a temporary fastening sheet 1D is obtained in which the chopped strands and prepregs included in the prepreg laminate 1C are temporarily fastened together. In this heating/pressurizing step, a belt conveyor having a heating/pressurizing mechanism can be used. The belt conveyor is driven, for example, at a speed of 420 mm/min to pass the prepreg laminate 1C between a pair of upper and lower pressure rollers 9 (a gap of 7 mm). The heating temperature in this step is not particularly limited, but the fiber orientation of the chopped strand prepreg contained in the temporary fixing sheet 1D should be around the glass transition temperature (Tg) or melting point temperature (Tm) of the thermoplastic resin used. is preferable from the viewpoint of maintaining

Here, in the manufacturing method of the present invention, the prepreg laminate 1C obtained in the spreading/laminating step may be press-molded from the following preheating step, or the temporary fixing sheet obtained in the temporary fixing step may be used as a preliminary Press molding may be performed from the heating step.

(6. Preheating step)
This step is a step of heating the base material in order to facilitate the flow of the base material during press molding. It is placed between the molds 10a and heated until the viscosity of the thermoplastic resin contained therein reaches 20 to 1800 [Pa·s]. Here, the term "viscosity" simply means "complex viscosity" (the same shall apply hereinafter). At this time, when the matrix resin is a crystalline resin, it is heated at a temperature above the melting point and below the thermal decomposition temperature. When the matrix resin does not have a melting point, it is heated at a temperature above the glass transition temperature and below the thermal decomposition temperature. In the embodiment of the present invention, heating was performed at 150° C. for 5 minutes (300 sec) under no pressure (or 0.5 MPa or less), and the resin viscosity became 119 [Pa·s]. Moreover, in this preheating step, in addition to heating in the mold as described above, a preheating machine may be used for heating using near-infrared rays or far-infrared rays.

(viscosity curve)
The heating time until the resin viscosity of the prepreg laminate 1C reaches a required viscosity varies depending on the heating temperature. FIG. 2 shows a viscosity curve in the polymerization process of a thermoplastic epoxy resin when heated at a heating temperature of 180.degree.

In the viscosity curve of FIG. 2, the viscosity gradient begins to rise after 2 minutes have passed, and after 4 minutes has passed, the viscosity increases with a substantially uniform steep slope until 11 minutes, after which it becomes a slightly gentle upward slope. The maximum viscosity of 1800 [Pa·s] is reached in about 7 minutes and 30 seconds.

(Method for measuring resin viscosity)
Here, a method for measuring resin viscosity will be described. The resin used for the measurement was a mixture of 100 parts by weight of a thermoplastic epoxy resin (XNR6850V, manufactured by Nagase ChemteX Corporation) and 8 parts by weight of a curing agent (XNH6850V, manufactured by Nagase ChemteX Corporation). , from which the solvent component contained in the mixture is removed.

The viscosity measuring device used for the measurement is a rotational viscometer rheometer (model: MCR302, manufactured by Anton Paar Co., Ltd.). The viscosity was measured under conditions of strain 3% and frequency 1 Hz, the resin was sandwiched between the hot plate and the geometry, the temperature of the hot plate was kept at 180° C., and the viscosity was measured over time. The result is shown in FIG. 2 described above.

(7. Sheet forming process)
In this step, the viscosity of the thermoplastic resin contained in the prepreg laminate 1C or the temporary fixing sheet 1D is maintained at 20 to 1800 [Pa s] as in the preheating step. This is a step of compressing by pressing with a pressure of 8 [MPa] and molding into a sheet of a predetermined thickness. If the viscosity during molding is above the above range and the press pressure is below the lower limit, voids tend to remain inside the resulting fiber-reinforced composite material, which is not preferable. On the other hand, if the viscosity is below the lower limit and the pressing pressure is above the upper limit, the resulting fiber-reinforced composite material tends to be prone to burr formation, resulting in increased weight variation, which is not preferable. Further, if the press pressure is higher than the upper limit, the mold used will be deformed, which is not preferable.

In the embodiment of the present invention, the viscosity of the resin contained in the temporary fastening sheet 1D is set to 119 [Pa·s], and the temperature and pressure are applied for 15 minutes at 150° C. and 4 MPa. As a result of this heat and pressure treatment, a carbon fiber reinforced composite material 1E having a thickness of 2 mm was obtained. The "15 minutes" can be increased or decreased in order to remove voids according to the thickness and basis weight of the temporary fixing sheet 1D and the target composite material. The heating temperature (150° C.) was measured with a thermocouple temperature sensor inserted near the central portion in the thickness direction of the carbon fiber reinforced composite material 1E.
In this press forming, the inter-fiber gaps of the temporary fixing sheet 1D are impregnated with the resin without disturbing the fiber orientation. Therefore, an isotropic carbon fiber reinforced composite material 1E with a low void fraction and little variation in physical properties can be obtained.

(8. Cooling process)
This step is a step of cooling the pressure plate 10 and the mold 10a to a predetermined temperature while maintaining the press pressure described above after the sheet molding, and the reinforcing fiber composite material 1E can be demolded from the mold a. can. The cooling temperature at this time is preferably below the glass transition temperature (Tg) or below the melting point temperature (Tm) of the thermoplastic resin used as the matrix resin.

(chopped strand prepreg)
Next, the size of the chopped strand prepreg used in this embodiment will be described.
(average volume)
The chopped strand prepreg used in this embodiment preferably has an average volume (mm ³ ) per prepreg sheet of 5 to 120 mm ³ , more preferably 4 to 60 m ³ . If the average volume per sheet exceeds the upper limit (60 m ³ or 120 mm ³ ), the number of substrates (the number of chopped strand prepregs 1B) that can be sprinkled per unit area decreases, resulting in increased variation in physical properties. It becomes difficult to ensure isotropy.

(length)
The length of the chopped strand prepreg in the fiber direction is preferably 5 to 50 mm on average, more preferably 10 to 30 mm on average. By adjusting the average length, it becomes easier to ensure high mechanical strength and isotropy as a sheet, and it is possible to suppress the generation of voids in the sheet.

(width)
The width of the chopped strand prepreg in the direction perpendicular to the fiber direction is preferably 10 to 20 mm on average, more preferably 12 to 20 mm on average, and still more preferably 15 to 20 mm on average. By setting the average length in the width direction to 10 mm or more, it becomes easier to obtain a sufficient number of laminated sheets per unit thickness, and it becomes easier to ensure isotropy. Also, by setting the average length in the width direction to 20 mm or less, it becomes easier to prevent tape cracking, thereby making it easier to stabilize the volume of the base material per prepreg and to suppress variations in mechanical strength.

(thickness)
The thickness of the chopped strand prepreg is preferably 55-115 μm on average, more preferably 55-95 μm. By setting the average thickness to 55 μm or more, it becomes easier to prevent tape cracking, thereby making it easier to stabilize the volume of the base material per prepreg sheet and to suppress variations in mechanical strength. In addition, by setting the average thickness to 115 μm or less, it becomes easier to obtain a sufficient number of laminated sheets per unit thickness, thereby making it easier to ensure isotropy.

(number of layers)
The number of layers of chopped strand prepreg laminated in the thickness direction of the reinforced composite material is preferably 9 to 19 layers/mm, more preferably 13 to 19 layers/mm. Having 9 or more layers makes it easier to ensure isotropy, and from the viewpoint of stable production of prepreg, it is preferable to have 19 or less layers.

(Preferred expansion rate of temporary fixing sheet)
A preferable expansion rate of the temporary fixing sheet 1D is 100 to 115%. The expansion rate here is the ratio (%) of expansion from the size (vertical and horizontal length) of the temporary fixing sheet 1D to the target composite material size (vertical and horizontal length). = 100 x (target size of composite material (vertical and horizontal length))/(size of temporary fixing sheet 1D (vertical and horizontal length)). For example, if the target size of the composite material is a rectangular sheet of 600 mm×600 mm, the temporary fixing sheet 1D should be manufactured so that the vertical and horizontal lengths are about 560 mm to 580 mm. When the expansion ratio is 115% or more (the length and width is less than 560 mm), the prepreg contained in the composite material flows too much during sheet molding, and isotropy as a sheet (CV value described later) cannot be obtained. I don't like it because

Due to the above-mentioned suitable expansion ratio (100 to 115%), it is possible to form the sheet without destroying the orientation of the prepregs included in the temporary fixing sheet 1D and maintaining the parallelism of the fiber orientation in the prepreg. becomes. This makes it possible to obtain an isotropic composite material with little variation in physical properties.

(Confirmation test for variations in physical properties)
Five test pieces were cut into strips from an arbitrary position in the first direction of one sheet of the obtained carbon fiber reinforced composite material 1E, and in the second direction perpendicular to the first direction, Similarly, five test pieces were cut into strips. The size of these strip-shaped specimens is 250 mm±1.0 mm in length and 35 mm±0.2 mm in width. According to the JIS K 7164 standard, this was tested for confirmation of physical property variations at a distance between chucks of 150 mm and a test speed of 1.0 mm/min.

Here, the CV value (Coefficient of Variation) is an index (coefficient of variation) representing relative dispersion, and is a value represented by (standard deviation/average value of measured values)×100 (%). A smaller tensile strength CV value indicates less variation in tensile strength.

(Example and Comparative Example)
In Examples 1 to 12 and Comparative Examples 1 to 5 in Table 1 below, the heating temperature was 180 ° C., the types of carbon fiber strand 1 and thermoplastic resin were the same, the preheating time, the press viscosity (press The table below summarizes the results of tests conducted with various resin viscosities during molding and various press pressures. The column of voids and burrs on the far right indicates the void ratio and burr weight ratio determined according to the criteria in Table 2 below.

The void fraction was measured according to JIS K7052. Here, a void rate of less than 0.6% was considered acceptable. The burr weight ratio was obtained by using a sample fiber-reinforced composite material with a size of 600 mm square and a thickness of 2 mm, a resin volume fraction (Vf) of 40%, and a total weight of 995 g. The weight of is displayed in %. Here, a burr weight percentage of less than 0.8% was regarded as acceptable.

The carbon fiber strand 1 used the carbon fiber TC36P-12K (800 tex, 12,000 filaments, manufactured by Formosa Plastics Corporation), but other carbon fiber strands with different thickness (tex) and the number of filaments were used. No significant difference was observed in the results shown in Table 1 in a similar test conducted as described above.

Therefore, when carbon fibers are used as reinforcing fibers in the present invention, the number of filaments is not particularly limited. In addition to 12000 lines (12K) shown in the above embodiment, 1000 lines (1K), 3000 lines (3K), 6000 lines (6K), 15000 lines (15K), 18000 lines (18K), 24000 lines (24K) , 30,000 (30K), 60,000 (60K), etc., depending on the width and thickness of the prepreg used in the present invention.

(Example)
All of Examples 1 to 12 have a press viscosity of 20 to 1800 Pa·s and a press pressure of 1 to 8 MPa. Therefore, the coefficient of variation, void fraction and flash weight fraction all pass.

In Example 1, although the pressing pressure is the lower limit (1 MPa), the void ratio is small due to the low viscosity (27 Pa·s), and the sample passes the test. Examples 2 and 3 have low viscosity (27 Pa·s) as in Example 1, but the pressing pressure is slightly high (4 MPa, 8 MPa), so the flash weight ratio (0.61%, 0.79%) is slightly high. , the void fraction (0.20%, 0.13%) is less than 0.28% of Example 1, which is acceptable. In Example 4, the pressing pressure is the lower limit (1 MPa) and the viscosity (128 Pa·s) is slightly high, so the void ratio (0.32%) is slightly large, but it is acceptable.

Examples 5 to 11 have a good balance between viscosity and press pressure, so all of the coefficient of variation, void ratio, and flash weight ratio pass the test. 0.72%) is slightly large, and Example 10 has a slightly large void fraction (0.48%) because the pressing pressure is the lower limit (1 Pa·s). Example 12 also has a good balance between viscosity and press pressure, so all of the coefficient of variation, void ratio, and flash weight ratio are acceptable. is slightly larger.

(Comparative example)
On the other hand, in Comparative Example 1, the press viscosity was insufficient at 15 (Pa s). %) were unacceptable. In Comparative Example 2, since the pressing pressure was insufficient at 0.5 MPa, the burr weight ratio (0.12%) passed, but the coefficient of variation (36.8%) and void ratio (1.04%) failed. there were.

In Comparative Example 3, since the pressing pressure was 10 MPa, which was excessive, the void ratio (0.14%) passed, but the coefficient of variation (22.0%) and burr weight ratio (0.84%) failed. In Comparative Example 4, the press viscosity (1850 Pa·s) was excessive, so the burr weight ratio (0.29%) passed, but the coefficient of variation (24.1%) and void ratio (0.62%) failed. there were. Comparative Example 5 also had an excessive press viscosity (2780 Pa·s), so the burr weight ratio (0.22%) passed, but the coefficient of variation (24.6%) and void ratio (0.81%) failed. there were.

As described above, when the viscosity of the resin is lower than 20 [Pa s], the fluidity of the resin becomes too high, so the fiber orientation of the prepreg contained in the molded sheet tends to be disturbed, leading to variations in physical properties. Also, even if the press pressure is higher than 8 [MPa], the fiber orientation of the prepreg contained in the molded sheet is likely to be disturbed, leading to variations in physical properties. Also, when the viscosity of the resin is higher than 1800 [Pa·s] or the press pressure is lower than 1 [MPa], voids contained in the molded sheet cannot be removed, resulting in deterioration of physical properties.

Using the isotropic carbon fiber reinforced composite material obtained by the present invention as an intermediate material, heat and pressurize it using a mold having a desired product shape to easily manufacture an FRP product with excellent surface properties and physical properties. can be done. The isotropic carbon fiber reinforced composite material 1E can be used as an alternative to sheet metal due to the characteristics of discontinuous fibers and thermoplastic materials, and can realize high-cycle FRP molded product production. In addition, since the fiber orientation can be maintained during press molding, it is possible to manufacture high-strength, thin-walled FRP molded products at low cost, making it possible to meet a wide range of product needs.

As described above, the isotropic carbon fiber reinforced composite material obtained by the present invention is capable of high cycle and thin wall, so it can be applied to structural members of automobiles at low cost. It can also be advantageously applied as a molding material for frames and housings of devices.

Although the embodiments, examples, and comparative examples of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, in the above embodiment, the carbon fiber strand 1 is passed through the guide rollers 3 in the water in the opening step, but the carbon fiber strand 1 may be opened using another method, such as an air flow.

In addition, in the method of making the chopped strand prepreg 1B into a prepreg laminate 1C having a two-dimensional random fiber orientation using a spreader 7, the prepreg laminate 1C is continuously produced by using a belt conveyor instead of the deposition board 8. It is good also as a method of forming. In this case, the spreader 7 can be combined with a quantitative feeder for the chopped strand prepreg 1B or a plurality of feeders can be arranged to improve productivity.

In addition, instead of allowing the chopped strand prepreg 1B to freely fall from the spreader 7 shown in FIG. It may be directly sprayed or layered. In this case, a prepreg laminate 1</b>C with two-dimensional random fiber orientation and a predetermined thickness is formed in the rectangular recess 21 .

A prepreg laminate 1C obtained by scattering and laminating chopped strand prepregs 1B as shown in FIG. 4(a) is pressed with a punch 30 to obtain a carbon fiber reinforced composite material 1E shown in FIG. 4(b). When pressing with the punch 30, the prepreg laminate 1C is of course heated to a predetermined temperature as described above. This method does not require the pressure roller 9 for temporary fixing shown in FIG. 9, and can omit the step of forming the temporary fixing sheet 1D, so that the production efficiency of the carbon fiber reinforced composite material 1E can be improved.

1: Carbon fiber strand 1A: Spread strand 1B: Chopped strand/prepreg 1C: Prepreg laminate 1D: Temporary fixing sheet 1E: Carbon fiber reinforced composite material 2: Water tank 3: Guide roller 4: Hot roller pair 5: Release belt Pair 6: Cutter 7: Spreader 8: Deposition board 9: Pressure roller 10: Pressure plate

Claims (8)

Chopped strand prepregs in which reinforcing fibers are impregnated with a thermoplastic resin are laminated in a two-dimensional random orientation to form a prepreg laminate having a predetermined thickness, and the prepreg laminate is heated and pressed in a softened state. A temporary fixing sheet is formed by passing it through a roller, and the temporary fixing sheet is heated to a complex viscosity of 20 to 1800 [Pa s] and pressurized at 1 to 8 [MPa] to obtain a predetermined thickness. A method for producing a fiber-reinforced composite material, which is characterized by molding into a sheet -like size with a spread rate of 100 to 115% and then cooling. The method for producing a fiber-reinforced composite material according to claim 1, wherein the prepreg laminate is heated under no pressure or at 0.5 MPa or less until the viscosity reaches 20 to 1800 [Pa·s]. 3. The method for producing a fiber-reinforced composite material according to claim 1, wherein the fiber volume content of said fiber-reinforced composite material is 10 to 80%. The method for producing a fiber-reinforced composite material according to any one of claims 1 to 3, wherein the chopped strand prepreg has an average volume of 5 to 120 mm ³ . The method for producing a fiber-reinforced composite material according to any one of claims 1 to 3, wherein the chopped strand prepreg has an average length of 5 to 50 mm. The method for producing a fiber-reinforced composite material according to any one of claims 1 to 3, wherein the chopped strand prepreg has an average width of 10 to 20 mm. The method for producing a fiber-reinforced composite material according to any one of claims 1 to 3, wherein the chopped strand prepreg has an average thickness of 55 to 115 µm. The method for producing a fiber-reinforced composite material according to any one of claims 1 to 3, wherein the chopped strand prepreg has an average number of layers of 9 to 19 layers/mm.

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