JP6706743B2 - Method for producing carbon fiber reinforced plastic and carbon fiber reinforced plastic - Google Patents

Description

The present invention relates to a method for producing a carbon fiber reinforced plastic and a carbon fiber reinforced plastic.

A carbon fiber reinforced plastic (Carbon Fiber Reinforced Plastic: CFRP) is configured by embedding a plurality of carbon fibers as an auxiliary material in a matrix resin. A thermosetting resin is used as a CFRP matrix resin in the market from the viewpoint of lightness and strength.

Patent No. 5665573

In CFRP, it is necessary to impregnate a matrix resin between a plurality of carbon fibers in order to obtain a certain strength. When a thermosetting resin is used as the matrix resin, it takes a long time to impregnate the matrix resin between a plurality of carbon fibers and to cure the matrix resin, resulting in low productivity. In order to solve such problems, a matrix resin using a thermoplastic resin has been developed.

However, since the thermoplastic resin usually has a higher viscosity than the thermosetting resin, the impregnation rate between a plurality of carbon fibers is lowered in the CFRP manufacturing apparatus or manufacturing method for the thermosetting resin that has been conventionally used (( For example, the volume void ratio becomes high), and as a result, the strength may decrease. On the other hand, in order to increase the impregnation rate while using a thermoplastic resin, it is conceivable to use short fibers as the carbon fibers. In that case, the strength reinforcement by carbon fibers is stronger than the case where continuous carbon fibers are used. Is decreased, and as a result, the strength of CFRP tends to be decreased.

Therefore, an object of the present invention is to provide a method for producing a carbon fiber reinforced plastic and a carbon fiber reinforced plastic capable of improving productivity while ensuring strength.

A method for producing a carbon fiber reinforced plastic according to one aspect of the present invention, a cover having a knitting structure in which a thermoplastic resin covering yarn is weft knitted, so that the circumference of the carbon fiber yarn containing a plurality of continuous carbon fibers is A composite yarn structure forming step of manufacturing at least one composite yarn structure by weaving covered and continuous composite yarns, and one composite yarn structure or a plurality of composite yarn structures are laminated. A heating and pressurizing step of heating and pressing the laminated body formed by melting the covering fiber, thereby burying the carbon fiber thread structure in a state in which the carbon fiber thread is woven with the thermoplastic resin. , Is provided.

In the above composite yarn, since the carbon fiber yarn is covered with the cover having the knitting structure in which the thermoplastic resin covering yarn is weft-knitted, a continuous composite yarn is easily woven to form a composite yarn structure. Can be formed. In the above manufacturing method, since the carbon fiber reinforced plastic is obtained by heating and pressing the composite yarn structure, the productivity of the carbon fiber reinforced plastic can be improved. In addition, since the covering yarn that constitutes the cover of the composite yarn is weft-knitted, the adhesion between the carbon fiber yarn and the covering yarn can be improved. Therefore, by heating and pressing the composite yarn structure, it is possible to reduce the volume void ratio of the carbon fiber reinforced plastic when the carbon fiber yarn is embedded in the thermoplastic resin that constitutes the covering yarn. For the same reason, the fiber volume content of the carbon fiber reinforced plastic can be improved. In addition, since the composite yarn structure is formed by weaving continuous composite yarns, the carbon fiber yarn structure that remains after the covering yarn is heated and melted is also formed of continuous carbon fiber yarns. It Therefore, the strength of the carbon fiber yarn can be effectively utilized. As a result, strength can be secured.

In one embodiment, the manufacturing method further comprises a washing step of washing the composite yarn structure, and before the washing step, the plurality of carbon fibers contained in the carbon fiber yarn are bound by a sizing agent. In the washing step, the sizing agent may be removed, and in the heating/pressurizing step, one of the composite yarn structures or the laminated body washed in the washing step may be heated and pressed.

In this case, since the sizing agent for staking a plurality of carbon fibers is removed in the washing step, it is possible to improve the adhesiveness of the interface between the carbon fibers and the thermoplastic resin. As a result, the strength of the carbon fiber reinforced plastic can be improved.

A carbon fiber reinforced plastic according to another aspect of the present invention comprises a carbon fiber thread structure in which carbon fiber threads containing continuous carbon fibers are woven, and a thermoplastic resin in which the carbon fiber thread structure is embedded. And a resin portion that is

This carbon fiber reinforced plastic can be preferably manufactured by the method for manufacturing a carbon fiber reinforced plastic according to the present invention. As a result, it has the same effects as those of the method for producing a carbon fiber reinforced plastic.

The carbon fiber reinforced plastic according to one embodiment includes a plurality of the carbon fiber thread structures, the plurality of the carbon fiber thread structures are laminated, and the resin portion is a plurality of the carbon fibers that are laminated. The thread structure may be embedded.

In one embodiment, the void fraction in the carbon fiber reinforced plastic may be substantially 0%. In this case, it is easy to secure the strength of the carbon fiber reinforced plastic.

In one embodiment, the fiber volume content of the carbon fiber reinforced plastic may be 20% by volume or more. In this case, since the strength of the carbon fiber can be utilized more effectively, the strength of the carbon fiber reinforced plastic can be improved.

A carbon fiber reinforced plastic according to still another aspect of the present invention is such that a carbon fiber yarn containing a plurality of continuous carbon fibers is covered with a cover having a knitting structure in which a covering yarn made of a thermoplastic resin is weft-knitted. It is a molded product obtained by heating and pressing a composite yarn structure obtained by weaving the continuous composite yarns.

In the composite yarn that constitutes the composite yarn structure, the carbon fiber yarn is covered with a cover that is a weft-knitted covering ring. Therefore, in the above-mentioned carbon fiber reinforced plastic which is a molded body obtained by heating and pressing the composite yarn structure, the woven structure made of continuous carbon fiber yarns is embedded in the thermoplastic resin in which the covering yarns are melted. Have a structure. In the above-mentioned composite yarn, since the carbon fiber yarn is covered by the cover having the knitting structure in which the thermoplastic resin covering yarn is weft-knitted, the continuous composite yarn is easily woven to obtain a composite yarn structure. Can be manufactured. Then, since the carbon fiber reinforced plastic can be manufactured by heating and pressing the composite yarn structure, the productivity of the carbon fiber reinforced plastic can be improved. In addition, since the covering yarn that constitutes the cover of the composite yarn is weft-knitted, the adhesion between the carbon fiber yarn and the covering yarn can be improved. Therefore, by heating and pressurizing the composite yarn structure, the carbon fiber reinforced plastic volume void ratio can be reduced when the carbon fiber yarn is embedded in the thermoplastic resin forming the covering yarn. For the same reason, the fiber volume content of the carbon fiber reinforced plastic can be improved. Further, since the composite yarn structure is formed by weaving continuous carbon fiber yarns, the carbon fiber reinforced plastic can effectively utilize the strength of the carbon fiber yarns. As a result, strength can be secured.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of carbon fiber reinforced plastic and carbon fiber reinforced plastic which can improve productivity while ensuring strength can be provided.

It is a figure which partially cuts and shows the composite yarn used for the manufacturing method of the carbon fiber reinforced plastic which concerns on one Embodiment. It is a figure which shows the end surface of the composite yarn shown in FIG. FIG. 3 is a development view of the cover shown in FIGS. 1 and 2. It is drawing which shows the composite yarn actually manufactured. It is a flow chart of a manufacturing method of carbon fiber reinforced plastic concerning one embodiment. It is a top view showing a schematic structure of a compound thread structure manufactured in a compound thread structure formation process with which a manufacturing method of a carbon fiber reinforced plastic concerning one embodiment is provided. It is drawing which shows the composite yarn structure actually manufactured. It is drawing for demonstrating the hot press molding (heating pressurization) process with which the manufacturing method of the carbon fiber reinforced plastics which concerns on one Embodiment is equipped. It is drawing which shows an example of the temperature and pressure conditions in a hot press molding (heating pressurization) process. (A) is a top view which shows the schematic structure of the carbon fiber reinforced plastic manufactured by the manufacturing method of the carbon fiber reinforced plastic which concerns on one Embodiment, (b) is X(b)-X of (a). It is a schematic diagram of a cross-sectional structure along the line (b). It is a drawing which shows the carbon fiber reinforced plastic manufactured in Experiment 1. (A) is a drawing showing an SEM image of the carbon fiber reinforced plastic produced in Experiment 1, and (b) is a drawing showing a micro CT scan image of the carbon fiber reinforced plastic produced in Experiment 1. It is a drawing for explaining a tensile test. It is drawing for demonstrating a three-point bending test. (A) is a drawing showing an SEM image of the carbon fiber reinforced plastic produced in Experiment 2, and (b) is a drawing showing a micro CT scan image of the carbon fiber reinforced plastic produced in Experiment 2. It is a figure which shows the end surface of the other example of a composite thread.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same reference numerals are given to the same elements, and duplicate description will be omitted.

(First embodiment)
FIG. 1 is a drawing schematically showing a configuration of a composite yarn by partially breaking the configuration of a composite yarn used to manufacture a carbon fiber reinforced plastic (CFRP) according to an embodiment. 2 is a drawing schematically showing the end face of the composite yarn shown in FIG. The composite yarn 10 shown in FIGS. 1 and 2 includes a carbon fiber yarn 12 and a cover 14.

The carbon fiber yarn 12 is a core yarn in the composite yarn 10, and is a carbon fiber bundle of a large number of continuous carbon fibers 12a. As the carbon fiber bundle, for example, 1K (1000 filament), 3K (3000 filament) or the like can be used. Hereinafter, unless otherwise specified, the plurality of carbon fibers 12a included in the carbon fiber yarn 12 in the composite yarn 10 are bundled by the sizing agent. The periphery of the carbon fiber thread 12 is covered with a cover 14.

As shown in FIG. 3, which is an expanded view of the cover 14, the cover 14 has a knitting structure in which a covering thread 14a, which is a knitting thread, is knitted in a weft manner, and covers the periphery of the carbon fiber thread 12. The cover 14 is for protecting the carbon fiber threads 12.

In one embodiment, the number of wales in the cover 14, that is, the number of stitches in the same course is, for example, 2 or more and 6 or less. The number of courses per 1 cm of natural length in the cover 14, that is, the number of stitches per 1 cm of natural length of the same wale is, for example, 6 or more and 14 or less.

In one embodiment, as the covering yarn 14a, for example, a fiber yarn having a thickness of 33 dtex (decitex) to 250 dtex (decitex) that can be easily covered is used. The material of the covering thread 14a is a thermoplastic resin. That is, the covering thread 14a is a thermoplastic fiber thread. Examples of the thermoplastic resin include polyethylene resin, polyester resin, nylon (polyamide) resin, polypropylene resin and the like.

The composite yarn 10 can be manufactured by covering the carbon fiber yarn 12 with a cover 14. Specifically, the cover 14 surrounds the periphery of the carbon fiber yarn 12 by weaving (knitting) the continuous covering yarn 14 a. Thereby, the continuous composite yarn 10 is manufactured. FIG. 4 is a drawing showing a composite yarn 10 produced by covering the periphery of a carbon fiber yarn 12 with a cover 14 in which a covering ring yarn 14a is weft-knitted.

Next, a method for manufacturing a carbon fiber reinforced plastic (CFRP) using the composite yarn 10 will be described. FIG. 5 is a flowchart of a CFRP manufacturing method. The CFRP manufacturing method includes a composite yarn structure forming step S10 and a hot press molding step (heating and pressing step) S14. The CFRP manufacturing method may include a cleaning step S12 as shown in FIG. Furthermore, the CFRP manufacturing method may include a composite yarn manufacturing step of manufacturing the composite yarn 10 as described above. Next, each step of the method for manufacturing the composite yarn 10 will be described. Unless otherwise specified, the CFRP manufacturing method described below is a mode including the cleaning step S12.

[Composite yarn structure forming step]
In this step, the composite yarn 10 is woven to form the composite yarn structure 16 as schematically shown in FIG. In FIG. 6, a part of the composite yarn structure 16 is enlarged and schematically shown. In FIG. 6, the carbon fiber yarn 12 is schematically illustrated, and the carbon fibers 12 a and the like included in the carbon fiber yarn 12 are omitted from the illustration. The same applies to other figures after FIG.

The composite yarn structure 16 is a woven fabric in which the continuous composite yarn 10 is used as a warp yarn and a weft yarn, respectively. FIG. 6 shows a sheet-shaped (or cloth-shaped) composite yarn structure 16 in which the composite yarn 10 is plain-woven. The composite yarn structure 16 obtained by weaving the composite yarn 10 can be formed by, for example, a loom. FIG. 7 is a drawing showing an example of the composite yarn structure 16 actually manufactured by plain-weaving the composite yarn 10. In the composite thread structure forming step S10, the number of composite thread structures 16 used for manufacturing the CFRP 24 may be manufactured. For example, one, four, or eight composite yarn structures 16 are manufactured. Hereinafter, unless otherwise specified, the manufacturing process of the CFRP 24 using a plurality of composite yarn structures 16 will be described.

[Washing process]
In this step, the composite yarn structure 16 formed in the composite yarn structure forming step S10 is washed with a sizing agent removing agent, and the sizing agent used for sizing the plurality of carbon fibers 12a contained in the carbon fiber yarn 12 is removed. Remove. As the sizing agent removing agent, one suitable for the type of the sizing agent may be used. Acetone, toluene, xylene etc. are mentioned as an example of a sizing agent removal agent. Examples of the cleaning method include a method of immersing the composite yarn structure 16 in a solution containing a sizing agent removing agent, shower cleaning, spray cleaning, ultrasonic cleaning, and the like. After washing the composite yarn structure 16 in the washing step S12, the composite yarn structure 16 is dried.

[Hot press molding process]
In the hot press molding step S14, as schematically shown in FIG. 8, a laminate 18 formed by laminating a plurality of composite yarn structures 16 is hot press molded.

When forming the laminated body 18, a plurality of composite yarn structures 16 may be fixed by stitching with a carbon fiber yarn. The hot press molding is performed by the hot press device 20. Specifically, the laminated body 18, which is a member to be molded, is arranged between the pair of press plates 22A and 22B included in the hot press device 20, and the laminated body 18 is subjected to a predetermined temperature condition by the pair of press plates 22A and 22B. While applying temperature, the pressure is applied under a predetermined pressure condition to perform hot press molding.

FIG. 9 is a schematic view showing an example of hot press conditions when carrying out hot press molding, and shows an example of temperature change and pressure change in the hot press molding step S14. In FIG. 9, the horizontal axis represents the time from the start of heating of the laminated body 18, one of the vertical axes represents the temperature at the central portion in the thickness direction of the laminated body 18, and the other of the vertical axes. Indicates the pressure applied to the laminated body 18.

When carrying out the hot press molding, first, the laminated body 18 is held by the pair of press plates 22A and 22B. An example of the first pressure P1 that acts on the laminated body 18 from the pair of press plates 22A and 22B is 0 MPa to 5 MPa.

With the laminated body 18 held in this way, the temperature of the pair of press plates 22A and 22B is increased from the start of heating to time t1 so that the temperature in the central portion of the laminated body 18 in the thickness direction reaches the temperature Ta. Increase (heating step).

The time t1 is, for example, 1 minute to 30 minutes, and can be determined according to the performance, size, etc. of the hot press device 20. The time t1 may be appropriately set according to the number of the composite yarn structures 16 forming the laminated body 18 and the like within a range that is possible depending on the performance and size of the heat pressing device 20. For example, when the laminate 18 has four composite yarn structures 16, the time t1 is 14 minutes, and when the laminate 18 has six composite yarn structures 16, the time t1 is 15 minutes. Yes, and if the laminate 18 has eight composite yarn structures 16, the time t1 may be 16 minutes.

The temperature Ta may be higher than the melting point Mp (degrees) of the thermoplastic resin forming the covering thread 14a. The temperature Ta is usually Mp+75 degrees or less. When the covering thread 14a is made of nylon 6, the melting point of nylon 6 is 225 degrees, so an example of the temperature Ta is 230 degrees.

After raising the internal temperature of the laminate 18 to the temperature Ta, the temperature and pressure are kept constant. The covering thread 14a is melted while maintaining the state until time t2 (melting step). An example of (t2-t1) is 0 to 30 minutes. At time t2, the pressure applied to the stacked body 18 is increased to the second pressure P2 higher than the first pressure P1. An example of the second pressure P2 is 1 MPa to 15 MPa. After that, the laminated body 18 is heated at the temperature Ta and the laminated body 18 is pressurized at the second pressure P2 to heat press the laminated body 18 until time t3 (pressing step). An example of (t3-t2) is 1 minute to 30 minutes, for example, 15 minutes. After time t3, the temperature of the pair of press plates 22A and 22B is sequentially decreased to cool the laminated body 18, and the temperature inside the laminated body 18 is equal to or lower than the glass transition temperature Tg of the thermoplastic resin forming the covering thread 14a. Down to solidify the thermoplastic resin (cooling step). The cooling time is, for example, 1 minute to 300 minutes.

The CFRP 24 schematically shown in FIGS. 10A and 10B is obtained by hot-press molding the laminated body 18 based on the hot-pressing conditions as shown in FIG. The times t1, t2, t3 and the first and second pressures P1, P2 in the CFRP manufacturing process may be optimized according to the desired characteristics (strength, etc.) of the CFRP 24 to be manufactured. Not limited to values.

Next, the structure of the CFRP 24 manufactured as described above will be described with reference to FIGS. 10(a) and 10(b). FIG. 10A is a plan view showing a schematic configuration of the CFRP according to the embodiment, and FIG. 10A shows the CFRP partially enlarged. FIG. 10B is a schematic diagram of a cross-sectional configuration along the line X(b)-X(b) of FIG.

The CFRP 24 has a plurality of carbon fiber thread structures 26, and a resin portion 28 that embeds the carbon fiber thread structures 26 and is made of a thermoplastic resin.

The carbon fiber yarn structure 26 is composed of the carbon fiber yarn 12 which remains in the composite yarn structure 16 after the covering ring 14a is melted. Since the composite yarn structure 16 is a woven body of continuous composite yarns 10, the carbon fiber yarn structure 26 corresponds to a continuous woven body of carbon fiber yarns 12. In the present embodiment, the carbon fiber yarn structure 26 has a structure in which continuous carbon fiber yarns 12 are plain-woven.

Since the manufacturing method includes the cleaning step S12, the sizing agent for sizing the plurality of carbon fibers 12a is removed from the CFRP 24. However, since the plurality of carbon fibers 12a that have made up the carbon fiber yarn 12 are integrated by the thermoplastic resin that makes up the resin portion 28, the composite yarn 10 shown in FIG. A group of a plurality of carbon fibers 12a included in the constituent carbon fiber yarn 12 is referred to as a carbon fiber yarn 12.

The resin portion 28 functions as a matrix in the CFRP 24. The resin portion 28 is formed by melting and solidifying the covering thread 14a. Therefore, the resin portion 28 is made of the thermoplastic resin forming the covering thread 14a.

In one embodiment, the volume void fraction of CFRP 24 is substantially 0%. “Substantially 0% or less” means that the volume void ratio is 0.1% or less. In the present specification, the “void” is a concept that includes not only the voids in the resin portion 28 but also the unimpregnated regions between the carbon fibers 12a. The volume void fraction of CFRP24 can be 0.00000% or less. When the volume occupied by voids in the CFRP 24 is V1, the volume occupied by the resin portion 28 is V2, the volume occupied by the carbon fibers 12a is V3, and the volume void rate is α (%), the volume void rate α (%) is It is defined in (1). The volume void fraction α (%) can be measured with a micro CT scanner. The volume void ratio (%) in the present specification is a numerical value when a Micro-CT Scan (model number: BRUKER SKYSCAN 1172) manufactured by BRUKER micro CT is used as a micro CT scanner.
α={V1/(V1+V2+V3)}×100 (1)

In one embodiment, the fiber volume content of CFRP 24 can be 20 vol% or more. The fiber volume content is preferably 40% by volume or more, more preferably 50% by volume or more. The fiber volume content can be up to 90% by volume. When the fiber volume content rate of CFRP24 is β (volume %), the fiber volume content rate β (volume %) is defined by the formula (2) and measured in accordance with JIS K7075.
β={V3/(V2+V3)}×100...(2)
V2 and V3 in the equation (2) are the volume occupied by the resin portion 28 and the volume occupied by the carbon fiber 12a in the CFRP 24, as in the case of the volume void ratio α.

Next, the manufacturing method of CFRP24 and the effect of CFRP24 are demonstrated.

In the manufacturing method of the CFRP 24, the composite yarn 10 is manufactured, and the composite yarn 10 is woven to form the composite yarn structure 16. After that, the CFRP 24 is obtained by hot pressing the composite yarn structure 16. Therefore, the CFRP 24 is a hot press molded body of the composite yarn structure 16.

The composite yarn 10 is formed by covering the carbon fiber yarn 12 with a cover 14. Therefore, even if the carbon fiber yarn 12 is a carbon fiber bundle, the composite yarn 10 can be treated in the same manner as a normal yarn, and thus the formation of the composite yarn structure 16 as a woven fabric of the continuous composite yarn 10 is possible. It's easy. Since the covering thread 14a of the composite thread 10 is made of thermoplastic resin, the CFRP 24 can be obtained by hot press molding the composite thread structure 16. Therefore, the productivity of the CFRP 24 can be improved.

In the composite yarn 10, since the periphery of the carbon fiber yarn 12 is covered with the covering ring yarn 14a made of a thermoplastic resin, the covering ring yarn 14a can be arranged close to the carbon fiber yarn 12. This makes it easier to impregnate the inside of the carbon fiber bundle with the thermoplastic resin when the composite yarn structure 16 is hot press molded. Therefore, a lower volume void ratio (for example, substantially 0%) can be realized in the CFRP 24, so that the strength of the CFRP 24 can be secured. As described above, when the composite yarn structure 16 is hot press molded, it is easy to impregnate the inside of the carbon fiber bundle with the thermoplastic resin. Therefore, even if the amount of the thermoplastic resin is small, the thermoplastic resin is contained inside the carbon fiber bundle. Can be impregnated. Therefore, the fiber volume content in the CFRP 24 can be improved. Therefore, the strength of the CFRP 24 is improved.

Further, since the composite yarn structure 16 is formed by the continuous composite yarn 10, the carbon fiber yarn structure 26 in the CFRP 24 can also be formed by the continuous carbon fiber yarn 12. As a result, the strength of the carbon fiber 12a as the continuous fiber forming the carbon fiber yarn 12 can be utilized, so that the strength of the CFRP 24 can be secured. In other words, CFRP24 can obtain higher strength than CFRP manufactured from carbon fibers as short fibers.

The cover 14 included in the composite yarn 10 has a knitting structure in which the covering yarn 14a is weft knitted. When the knitting structure is weft knitting, the knitting is knitted so that the carbon fiber yarn 12 extending in one direction is wound by the covering yarn 14a. Therefore, the carbon fiber yarn 12 is relatively strong by the covering ring 14a of the cover 14. It can be tightened, and the degree of adhesion or the tightening force of the cover 14 to the carbon fiber yarn 12 can be increased. By adjusting the strength of the tension of the covering thread 14a during knitting, the covering thread 14a can be knitted so that the covering thread 14a is properly brought into close contact with the carbon fiber thread 12. As a result, when the composite yarn structure 16 formed by weaving the composite yarn 10 is hot-pressed (heated and pressed), the thermoplastic resin (the covering ring 14a melted) inside the carbon fiber bundle is The permeability (penetration) can be enhanced, and the degree of adhesion between the carbon fiber bundle and the thermoplastic resin can be enhanced. As a result, the strength of the CFRP 24 can be improved. However, in the case of weft knitting, since the fastening force is not enough to damage the carbon fiber yarn 12, even if the carbon fiber yarn 12 is covered with the covering ring 14a, it is possible to prevent the carbon fiber yarn 12 from being damaged.

Since the CFRP 24 is manufactured by hot pressing the composite yarn structure 16, the structure of the CFRP 24 depends on the structure of the composite yarn structure 16. On the other hand, the composite yarn structure 16 is formed by weaving the composite yarn 10 in which the carbon fiber yarn 12 that is a carbon fiber bundle is covered with the cover 14, and therefore, when forming the composite yarn structure 16, The composite yarn structure 16 having various structures can be formed while preventing the carbon fibers 12a from being damaged such as the fibers 12a being cut.

Further, the ratio of the carbon fiber yarn 12 and the thermoplastic covering ring yarn 14a can be set by changing the thickness and density of the thermoplastic covering yarn 14a, so that the CFRP 24 having a mixing ratio according to the purpose can be manufactured. is there. Therefore, for example, the strength of the CFRP 24 can be easily adjusted.

In CFRP24, since the matrix is made of a thermoplastic resin, the recyclability of CFRP24 is superior to that when the matrix is made of a thermosetting resin.

The form in which the thickness of the covering thread 14a is 33 dtex or more and 250 dtex or less has the following advantages. That is, if the thickness of the covering thread 14a in the cover 14 is 33 dtex or more, the coverage of the covering fiber 14a with respect to the carbon fiber thread 12 can be increased, and the gap in the cover 14 in which the covering ring 14a is weft-knitted. It is possible to suitably prevent the carbon fiber yarn 12 from jumping out from the outside. When the thickness of the covering thread 14a is 250 dtex or less, knitting with a knitting machine is easy.

In the form in which the number of stitches of the same course in the cover 14 is 2 or more and 6 or less, the diameter of the tubular knitting of the cover 14 can be reduced, and the degree of adhesion of the covering ring yarn of the cover 14 to the carbon fiber yarn 12 ( The tightening force) can be increased.

The form in which the number of stitches per natural cm of the same wale in the cover 14 is 6 or more and 14 or less has the following advantages. That is, when the number of stitches per 1 cm of natural length of the same wale in the cover 14 is 6 or more, the coverage ratio of the covering thread of the cover 14 to the carbon fiber thread 12 can be increased, and the covering thread of the cover 14 can be increased. It is possible to sufficiently suppress the carbon fiber yarn 12 from jumping outward from the gap.

If the number of stitches per natural length 1 cm of the same wale in the cover 14 is 14 or less, the cover 14 stitches may be too fine, resulting in defective covering (tack scratch) of the covering ring. In addition, it is possible to prevent the composite yarn 10 from being less flexible and difficult to weave with the composite yarn 10.

(Second embodiment)
A modified example of the composite yarn and a CFRP using the same will be described as a second embodiment. In the description of the second embodiment, elements similar to the elements corresponding to those in the first embodiment are designated by the same reference numerals except that the composite yarn is referred to as the composite yarn 10A, and redundant description will be omitted.

As schematically shown in FIG. 16, the composite yarn 10A in the second embodiment has a plurality of carbon fiber yarns 12 and further has a plurality of resin fiber yarns 36 made of a thermoplastic resin. Mainly different from the structure of the composite yarn 10. The second embodiment will be described focusing on this difference. FIG. 16 is a schematic view of an end surface of the composite yarn 10A. In FIG. 16, the carbon fiber yarn 12, the resin fiber yarn 36, and the cover 14 are schematically shown.

The resin fiber yarn 36 extends in the extending direction of the carbon fiber yarn 12 and is arranged parallel to the carbon fiber yarn 12. An example of the thermoplastic resin forming the resin fiber thread 36 may be the same as the example of the thermoplastic resin in the case of describing the covering thread 14a. The thermoplastic resin constituting the resin fiber yarn 36 and the thermoplastic resin constituting the covering yarn 14a may be the same or different. In the composite yarn 10A, the cover 14 in which the covering ring 14a is weft-knitted covers the bundle of the plurality of aligned carbon fiber yarns 12 and the plurality of resin fiber yarns 36.

Also in the composite yarn 10A, the carbon fiber yarn 12 is covered with the cover 14. Therefore, instead of the composite yarn 10 in the first embodiment, the composite yarn 10A is woven to form the composite yarn structure 16 as in the case of the first embodiment, and then hot press-molding the composite yarn structure 16. Even if the CFRP 24 is manufactured, at least the same operational effects as in the case of the first embodiment are obtained. By using the composite yarn 10A, the following operational effects are further obtained.

When the composite yarn 10A has the resin fiber yarn 36, the resin fiber yarn 36 is also melted in the hot press molding step S14 to become the resin portion 28 that constitutes the CFRP 24. Therefore, the fiber volume content β of the CFRP 24 can be adjusted by adjusting the number and size of the resin fiber threads 36.

In the composite yarn 10A, since the resin fiber yarn 36 made of a thermoplastic resin is arranged inside the cover 14, when the composite yarn 10A has a plurality of carbon fiber yarns 12, the distance between the carbon fibers 12a and the thermoplastic resin is large. Can be shortened. As a result, the thermoplastic resin is easily impregnated between the carbon fibers 12a. In particular, as shown in FIG. 16, by disposing the resin fiber thread 36 between the plurality of carbon fiber threads 12, it becomes possible to further shorten the distance between the carbon fiber 12a and the thermoplastic resin. It is easy to further impregnate the thermoplastic resin between the fibers 12a.

The composite yarn 10A may have at least one carbon fiber yarn 12 and at least one resin fiber yarn 36.

Hereinafter, the method for producing CFRP 24 and the action and effect of CFRP 24 will be specifically described with reference to the experimental results.

[Experiment 1]
In Experiment 1, the composite yarn 10 described in the first embodiment was used. The composite yarn 10 was formed by covering the circumference of one carbon fiber yarn 12 with a cover 14 obtained by weaving a covering yarn 14a. For the carbon fiber yarn 12, Torayca yarn 3K (T300B-3000-50B) manufactured by Toray Industries, Inc. was used. Nylon yarn (WN70d/2-24f-VF555-BC manufactured by Toray Industries, Inc.) was used for the covering yarn 14a. CFRP was manufactured using the composite yarn 10 according to the flowchart shown in FIG.

First, the composite yarn structure forming step S10 was performed. That is, four sheet-like composite yarn structures 16 were manufactured by plain weaving the composite yarn 10 as warp and weft.

Then, the cleaning step S12 was performed. In the washing step S12, all the formed composite yarn structures 16 were immersed in acetone and washed for 60 minutes.

Then, the hot press molding process S14 was implemented. In the hot press molding step S14, four composite yarn structures 16 were laminated to form a laminated body 18. When constructing the laminated body 18, the four composite thread structures 16 were sewn together and fixed with carbon fiber threads. Then, the laminated body 18 was set in the hot press apparatus 20 and hot press molding was performed. The temperature condition and the pressure condition were set as shown in FIG. In FIG. 9, time t1 is set to 14 minutes, time t2 is set to 19 minutes, and time t3 is set to 34 minutes. The first pressure P1 was 0.83 MPa and the second pressure P2 was 3 MPa. As a result, a plate-shaped CFRP 24 having a thickness of 0.8 mm could be manufactured.

FIG. 11 is a view showing the manufactured plate-shaped CFRP 24. From FIG. 11, it was demonstrated that a CFRP plate could be manufactured. Further, FIG. 12A is a drawing showing an SEM image of the manufactured CFRP observed by an SEM (scanning electron microscope), and FIG. 12B shows a micro CT scan image of the manufactured CFRP. It is a drawing. As a micro CT scanner, a Micro-CT Scan (model number: BRUKER SKYSCAN 1172) manufactured by BRUKER micro CT was used for acquisition of the micro CT scan image. The volume void ratio α defined by the formula (1) and obtained by measuring the manufactured CFRP24 with the micro CT scanner was 0.00000%. That is, it was demonstrated that CFRP24 having a volume void ratio α of substantially 0% could be manufactured. Further, the fiber volume content β of CFRP24 of Experiment 1 measured according to JIS K7075 and calculated by the formula (2) is 45.6 volume %, and the fiber volume content β is 20 volume% or more and 90 volume or more. It was demonstrated that CFRP24 of not more than% could be produced.

A tensile test and a three-point bending test were performed on the manufactured CFRP24. Test methods of the tensile test and the three-point bending test will be described.

[Tensile test]
The tensile test of CFRP24 was performed using the universal testing machine (model number: AUTOGRAPH AG-I) manufactured by Shimadzu Corporation. Specifically, a rectangular test piece S1 was cut out from the manufactured CFRP 24 as shown in FIG. The length ta in the longitudinal direction of the test piece S1 was 150 mm, and the length tb in the width direction was 20 mm. Since the thickness of the manufactured CFRP 24 was 0.8 mm, the thickness ha of the test piece S1 was 0.8 mm. An aluminum plate 30A having a length L1a (mm) is adhered to the front and back of a region having a length L1a (mm) at one end in the longitudinal direction of the test piece S1 and the length L1a (mm at the other end in the longitudinal direction of the test piece S1. The aluminum plate 30B having a length of L1a (mm) was adhered to the front and back of the area of ). The length L1a was 40 mm, and the thickness hb (mm) of the aluminum plates 30A and 30B was 2.0 mm. In the longitudinal direction of the test piece S1, the distance L1b between the aluminum plates 30A and 30B was 70 mm. The aluminum plates 30A and 30B were clamped by the clamps, and the test piece S1 was pulled in the longitudinal direction at the test speed va (mm/min). The test speed va (mm/min) was 5 mm/min. As a result, the maximum tensile stress σt was about 448 MPa. The tensile stress σt was calculated by the equation (3) when the load was Pt.
σt=Pt/(tb×ha) (3)

[Three-point bending test]
A three-point bending test of CFRP24 was performed using a universal testing machine (AUTOGRAPH AG-I) manufactured by Shimadzu Corporation. Specifically, a rectangular test piece S2 was cut out from the manufactured CFRP 24 as shown in FIG. The length ta in the longitudinal direction of the test piece S2 was 100 mm, and the length tb in the width direction was 10 mm. The support rods 32 were arranged at positions L2a (mm) from both ends of the test piece S2 to support the test piece S2. The length L2a (mm) is the length from the end of the test piece S2 to the axis of the support rod 32. The length L2a (mm) was 30 mm, and the distance L2b (mm) between the axes of the pair of support bars 32, 32 was 40 mm. At the midpoint position between the pair of support rods 32, 32 (the midpoint position in the longitudinal direction of the test piece S2), the rod-shaped indenter 34 presses the upper surface of the test piece S2 at the test speed vb (mm/min). did. The test speed vb (mm/min) was 5 mm/min. As a result, the maximum bending stress σb was 543 MPa. The bending stress σb was calculated by the equation (4) when the load was Pb.
σb=(3×Pb×L2b)/{2×tb×(ha) ² } (4)

[Experiment 2]
In Experiment 2, using the composite yarn 10 having the same structure as in Experiment 1, eight composite yarn structures 16 were formed in the same manner as in Experiment 1 in the composite yarn structure forming step S10. The cleaning step S12 is the same as in the case of Experiment 1, and thus the description thereof is omitted. In the hot press molding step S14, the laminated body 18 in which the eight composite yarn structures 16 are laminated is set in the same hot press apparatus 20 as in the case of Experiment 1, and heat is applied under the temperature condition and the pressure condition shown in FIG. Press molding was performed. In Experiment 2, the time t1 in FIG. 9 was 16 minutes, the time t2 was 21 minutes, the time t3 was 36 minutes, the first pressure P1 was 0.83 MPa, and the second pressure P2 was 3 MPa. As a result, a plate-shaped CFRP 24 having a thickness of 1.5 mm was manufactured.

FIG. 15( a) is a drawing showing an SEM image of the manufactured plate-shaped CFRP 24 observed by an SEM, and FIG. 15( b) is a drawing showing a micro CT scan image of the manufactured CFRP 24. The micro CT scanner used in Experiment 1 was used to acquire the micro CT scan image. The volume void ratio α defined by the formula (1) and obtained by measuring the manufactured CFRP24 with the micro CT scanner was 0.00000%. That is, it was demonstrated that CFRP24 having a volume void ratio α of substantially 0% could be manufactured. Further, the fiber volume content β of CFRP24 of Experiment 2 measured according to JIS K7075 and calculated by the formula (2) is 51.1 volume %, and the fiber volume content β is 20 volume% or more and 90 volume or more. It was demonstrated that CFRP24 of not more than% could be produced.

A tensile test and a three-point bending test were performed on CFRP24 manufactured in Experiment 2 as in Experiment 1. The tensile test was performed under the same test conditions as in Experiment 1 except that the thickness ha of the test piece S1 was 1.5 mm. As a result, the maximum tensile stress σt was about 559 MPa. The three-point bending test was performed under the same test conditions as in Experiment 1 except that the distance L2b (mm) was changed to 60 mm and the thickness ha of the test piece S2 was 1.5 mm. As a result, the maximum bending stress σb was 613 MPa.

In Experiments 1 and 2, the volume void ratio α was substantially 0%. That is, it can be seen that the CFRP 24 having a volume void ratio α of substantially 0% can be manufactured without depending on the number of the composite yarn structures 16 when manufacturing the CFRP 24. In Experiments 1 and 2, since the CFRP 24 is manufactured using the continuous composite yarn 10, the continuous carbon fiber 12a is embedded in the matrix of the CFRP 24, and the strength of the carbon fiber 12a can be effectively utilized. .. Therefore, it can be seen that the CFRP 24 having improved strength can be manufactured.

Although the embodiments and experimental examples of the present invention have been described above, the present invention is not limited to the modes shown in the above-described embodiments and experimental examples, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the CFRP (hot press molded body) 24 mainly formed by hot press molding the laminated body 18 in which the plurality of composite yarn structures 16 are laminated has been described. However, the CFRP 24 may be a hot press molded product in which one composite yarn structure 16 is hot press molded. That is, the CFRP 24 may have only one carbon fiber thread structure 26.

The composite yarn structure is not limited to the plain yarn of the composite yarn, and may be formed by other weaves such as twill weave and satin weave.

In the above-described embodiments and experimental examples, hot pressing is illustrated as a method for obtaining CFRP by heating and pressurizing the composite yarn structure. However, the method of heating and pressing is not limited to hot pressing as long as CFRP as a molded body obtained by heating and pressing the composite yarn structure is obtained.

10, 10A... Composite yarn, 12... Carbon fiber yarn, 12a... Carbon fiber, 14... Cover, 14a... Covering yarn, 16... Composite yarn structure, 18... Laminated body, 24... CFRP (carbon fiber reinforced plastic), 26... Carbon fiber thread structure, 28... Resin part, 36... Resin fiber thread.

Claims (3)

A cover having a knitting structure in which a covering thread made of a thermoplastic resin is weft-knitted covers the periphery of a carbon fiber thread containing a plurality of continuous carbon fibers, and at least one of them is formed by weaving a continuous composite thread. A composite yarn structure forming step of manufacturing two composite yarn structures,
A state in which the carbon fiber yarn is woven by heating and pressing a single laminated yarn structure or a laminated body in which a plurality of the laminated yarn structures are laminated to melt the covering yarn. A heating and pressurizing step of embedding the carbon fiber thread structure of the thermoplastic resin;
A method for producing a carbon fiber reinforced plastic, comprising: Further comprising a washing step of washing the composite yarn structure,
Before the washing step, the plurality of carbon fibers contained in the carbon fiber yarn are bundled by a sizing agent,
In the cleaning step, the sizing agent is removed,
In the heating and pressurizing step, one of the composite yarn structures or the laminate washed in the washing step is hot press molded,
The method for producing the carbon fiber reinforced plastic according to claim 1. A composite yarn structure in which a continuous composite yarn in which the periphery of a carbon fiber yarn containing a plurality of continuous carbon fibers is covered is woven by a cover having a knitting structure in which a covering yarn made of a thermoplastic resin is weft-knitted. Carbon fiber reinforced plastic, which is a molded product formed by heating and pressing the body.