JP2017164970A - Fiber-reinforced composite and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fiber-reinforced composite that, when shaping and molding a two-dimensional sheet-like intermediate substrate into a three-dimensional shape having a convexoconcave shape, has little molding failure that causes deterioration in strength of members such as wall thickness change of convexoconcave parts and wrinkle, void, and fiber meander on the surface or in the inside thereof, and can easily and securely mold a fiber-reinforced composite having excellent dynamic characteristics and excellent surface quality.SOLUTION: The method for producing a fiber-reinforced composite comprises heating a laminate of a sheet-like prepreg substrate composed of a reinforcing fiber and a thermoplastic resin, then applying a pressure to the laminate along a mold having a three-dimensional curved surface and cooling. In the method, the laminate is constituted so that at least a part thereof is composed of an unmelted part formed by a non-heating region and the other is composed of a molten part; the heated laminate is placed in the mold whose temperature has been adjusted to a temperature lower than the solidification temperature of the laminate; and the molten part is disposed along the mold.SELECTED DRAWING: Figure 1

Description

  The present invention is excellent in appearance and mechanical properties without fiber meandering and unevenness when forming a complex-shaped deep-drawn shape using a sheet-like prepreg base material composed of reinforced fibers and thermoplastic resin aligned in one direction. The present invention relates to a method for manufacturing a deep-drawn complex shape and a molded body thereof.

  Examples of the method for molding the fiber reinforced composite include a method of press molding a fiber reinforced thermoplastic resin molded plate which is an intermediate substrate of the fiber reinforced composite. Examples of the fiber reinforced thermoplastic resin molded plate include a laminate in which a continuous reinforcing fiber called a prepreg is laminated with a base material impregnated with a thermoplastic resin. The molded product thus obtained has excellent mechanical properties because it uses continuous reinforcing fibers. Further, by arranging the continuous reinforcing fibers regularly, it is possible to design the required mechanical properties, and the variation in the mechanical properties is small.

  However, since it is a continuous reinforcing fiber, it is difficult to form a complicated three-dimensional shape, and it is mainly limited to members close to a planar shape. Alternatively, when shaping a three-dimensional shape, the prepreg is cut to a width of a few millimeters to form a tape, and the three-dimensional shape is stacked and laminated so that the narrow tape itself follows the substantially two-dimensional shape. There is a technology called auto tape lay-up that allows a shape to follow even a complicated shape.

  However, the problem of low productivity remains for use in three-dimensional lamination of large area and thick members. On the other hand, stamping molding is known as a process with excellent productivity (for example, Patent Document 1). In stamping molding, a heated and melted base material is placed in a mold, clamped, pressed, cooled and solidified, and molded, so that a large number of molded products can be obtained in a short time. However, there is a problem that wrinkles and bridging (fiber stretching) due to insufficient deformability of the prepreg occur during shaping, and the yield of the fiber-reinforced composite is lowered.

  The thickness of the prepreg laminate is reduced in the process of solidifying into a fiber reinforced composite, so that the prepreg laminate formed in the part having a shape change, for example, the corner R portion, has continuous reinforcing fibers having low extensibility. For this reason, in order to eliminate the circumferential length difference, there arises a molding defect such as buckling and wrinkling, or bridging and not following the mold shape. In addition, voids are likely to occur immediately under bridging because molding pressure is difficult to apply. The generation of voids is a more significant problem in low pressure molding such as oven molding using a vacuum pump as a pressurizing means.

  Examples of the fiber reinforced thermoplastic resin molding plate suitable for forming a complex shape include a laminate of prepregs having notches penetrating from the front surface of the prepreg to the back surface in a direction crossing the reinforcing fibers of the prepreg. This base material is characterized by both excellent mechanical properties and high formability.

  However, when a complex shape is formed using a base material in which prepregs having cuts as described in Patent Document 2 are laminated, if force is applied in the direction of compression, the fibers are kinked and the force cannot be transmitted. Therefore, the mechanical properties cannot be demonstrated.

Japanese Patent Application Laid-Open No. 2014-156012 JP 2014-173031 A

  The object of the present invention is to form and form a two-dimensional sheet-like intermediate base material into a three-dimensional shape having a concavo-convex shape, and to change the thickness of the concavo-convex portion and the strength of the member such as wrinkles, voids, and fiber meandering inside. It is an object of the present invention to provide a method for producing a fiber-reinforced composite that can be molded easily and reliably with excellent mechanical properties and surface quality with few molding defects that cause deterioration.

In order to solve the above problems, the present invention employs the following means. That is,
(1) A method for producing a fiber-reinforced composite in which a laminate of a sheet-like prepreg base material composed of reinforcing fibers and a thermoplastic resin is heated, then pressed along a mold having a three-dimensional curved surface, and cooled. The non-melted part and at least a melted part in which at least a part of the laminate is not heated are provided, and the heated laminate is adjusted to a temperature lower than the solidification temperature of the laminate. A method for producing a fiber-reinforced composite, which is placed on a mold and the melted portion is placed along the mold.
(2) The method for producing a fiber-reinforced composite according to (1), wherein the reinforcing fibers aligned in one direction are used as the sheet-like prepreg base material.
(3) The fiber-reinforced composite according to (1) or (2), wherein the sheet-like prepreg base material provided with a plurality of intermittent cuts, in which at least a part of the reinforcing fibers is divided into a length of 10 to 100 mm, is used. Body manufacturing method.
(4) The method for producing a fiber-reinforced composite according to (3), wherein an absolute value of an angle θ (°) formed by the cut and the orientation direction of the reinforcing fiber is in a range of 2 ° to 45 °.
(5) The ratio L1 / L2 of the shortest cross-sectional length L1 and the longest cross-sectional length L2 longer than L1 among the cross-sectional lengths of the fiber-reinforced composite cut in the direction of pressing the laminate is 0. The manufacturing method of the fiber reinforced composite in any one of (1)-(4) which exists in the range of 3 <L1 / L2 <0.96.
(6) A plurality of bent portions formed in a cross section of the fiber reinforced composite cut in a direction in which the laminate is pressed along the reinforcing fiber orientation direction of the laminate, and the curvature radius R of the bent portion Is in the range of 2 to 5 times the thickness d of the fiber reinforced composite, and has two or more convex portions by the bent portion, the fiber reinforced composite according to any one of (1) to (5) Body manufacturing method.
(7) according to any one of the ratio S / L of the projected area Smm ² and maximum depth Lmm fiber reinforced composite was projected vertically in 1240mm below the range of 50 mm (1) ~ (6) A method for producing a fiber-reinforced composite.
It is.

  According to the present invention, it is excellent in formability to a three-dimensional shape, and easily and reliably has few molding defects that cause member strength deterioration such as thickness change of wrinkles, wrinkles, voids, and fiber meandering, and excellent mechanical properties. It is possible to produce a fiber reinforced composite having properties and surface quality.

It is the schematic which shows an example of the manufacturing method of this invention. It is the schematic which shows an example of the fiber reinforced composite obtained by the manufacturing method of this invention. It is the schematic which shows the position of the bending part provided in the fiber reinforced composite. It is the elements on larger scale of a bending part.

  The present invention is a fiber reinforced fiber that is excellent in shaping into a complicated shape during stamping molding, can be molded in a short time, and has excellent mechanical properties and surface quality applicable to structural materials. The present invention relates to a method for producing a composite. More specifically, a fiber-reinforced composite that easily follows the molding of a three-dimensional shape such as an R portion or an uneven shape, maintains mechanical strength as a structural member, and is suitably used for, for example, aircraft members, automobile members, sports equipment, and the like. It relates to the manufacturing method.

  More specifically, a laminate obtained by laminating a plurality of prepregs including reinforcing fibers oriented in one direction and a thermoplastic resin is preliminarily heated to a temperature equal to or higher than the melting point of the thermoplastic resin, and the thermoplastic resin is melted to form a cavity. Using a mold composed of an upper mold and a lower mold having a concavo-convex shape, a heated and melted laminate is placed in the mold lower than the solidification temperature of the laminate, the mold is clamped, and then pressurized and cooled. When performing stamping molding to obtain a fiber-reinforced composite by solidification, when the laminate is preheated to melt the laminate, at least a part of the laminate is provided with an unheated region during heating to form an unmelted portion, and the laminate This is a method for producing a fiber-reinforced composite, in which the laminate is pressed against the mold that is adjusted to a temperature lower than the solidification temperature, and a melted part other than the unmelted part is placed along the mold.

  Initially, the shaping | molding apparatus which manufactures a fiber reinforced composite_body | complex is demonstrated.

  As the mold for molding the fiber-reinforced composite of the present invention, a mold having a concave portion and a convex portion corresponding to the concave portion and having a cavity between the concave portion and the convex portion can be used. The thickness of the cavity is preferably 0.5 to 10 mm. The shortest cross-sectional length L1 that is the shortest of the lengths measured along the shape of the fiber-reinforced composite and the longest cross-section that is the longest among the cross-sectional lengths cut in the direction of pressing the laminate. It is preferable to use a mold having a ratio L1 / L2 with the length L2 in a range of 0.3 <L1 / L2 <0.96.

  Furthermore, a metal frame, a metal film, or a metal tape can be used as a jig that can be used to form a non-heated region when forming a fiber-reinforced composite. When cooling with a refrigerant, air or water having a temperature lower than the resin melting temperature can be used as a cooling medium.

  Next, the reinforcing fiber constituting the fiber reinforced composite used in the present invention will be described.

  The type of the reinforcing fiber is not particularly limited, and inorganic fiber, organic fiber, metal fiber, or a hybrid fiber having a combination of these can be used. Examples of reinforcing fibers include metal fibers such as aluminum, brass, and stainless steel, polyacrylonitrile-based, rayon-based, lignin-based, pitch-based carbon fibers, graphite fibers, insulating fibers such as glass, aramid resins, Examples thereof include organic fibers such as polybenzoxazole resin, polyphenylene sulfide resin, polyester resin, acrylic resin, nylon resin, and polyethylene resin, and inorganic fibers such as silicon carbide and silicon nitride. These fibers may be subjected to a surface treatment. Examples of the surface treatment include a treatment with a coupling agent, a treatment with a sizing agent, and an adhesion treatment of an additive in addition to a treatment for depositing a metal as a conductor. Moreover, these reinforcing fibers may be used individually by 1 type, and may use 2 or more types together. Among these, carbon fibers are preferable in consideration of mechanical properties such as strength of the final molded product. Moreover, it is preferable that the average fiber diameter of a reinforced fiber is 1-50 micrometers, and it is more preferable that it is 5-20 micrometers.

  In general, the longer the length of the reinforcing fiber contained in the laminate, the better the mechanical properties, but the fluidity during stamping molding decreases. In order to improve the fluidity during stamping molding, it is effective to cut the reinforcing fiber to a certain length, which makes it possible to obtain a substrate that can flow even in complicated three-dimensional shapes such as ribs and bosses. And wrinkles and bridging can be reduced. However, a stamping molding base material made of a cut reinforcing fiber and a resin composition, which is generally called a random material, has a variation in mechanical properties, so that it is difficult to design a part. As a solution, by laminating a plurality of prepregs having cuts, it is possible to obtain a laminate having good mechanical properties and small variations, and excellent fluidity during stamping molding.

  The prepreg that can be used in the method for producing a fiber-reinforced composite of the present invention is preferable from the viewpoints of moldability and mechanical properties if the fiber volume content Vf is 30% or more and 70% or less. The lower the value of Vf, the better the fluidity. However, if the value of Vf is less than 30%, the mechanical properties necessary for the structural material cannot be obtained. Considering the relationship between fluidity and mechanical properties, 30% to 60% is preferable. Such a Vf value can be measured based on JIS K7075 (1991).

  As a resin component constituting the fiber reinforced composite of the present invention, it is necessary to use a thermoplastic resin. Since the thermoplastic resin can be cooled and solidified without a chemical reaction to obtain a predetermined shape, it can be molded in a short time and has excellent productivity. Furthermore, the strength, particularly the impact property, can be improved by using a thermoplastic resin generally having a toughness value higher than that of the thermosetting resin. Examples of the thermoplastic resin having such characteristics suitable for the present invention include polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polytrimethylene terephthalate (PTT) resin, and polyethylene naphthalate (PEN) resin. Polyester such as liquid crystal polyester resin, polyolefin such as polyethylene (PE) resin, polypropylene (PP) resin, polybutylene resin, styrene resin, polyoxymethylene (POM) resin, polyamide (PA) resin, polycarbonate ( PC) resin, polymethylene methacrylate (PMMA) resin, polyvinyl chloride (PVC) resin, polyphenylene sulfide (PPS) resin, polyphenylene ether (PPE) resin, modified PPE resin, polyimide (PI) resin Polyamideimide (PAI) resin, polyetherimide (PEI) resin, polysulfone (PSU) resin, modified PSU resin, polyethersulfone resin, polyketone (PK) resin, polyetherketone (PEK) resin, polyetheretherketone (PEEK) ) Resin, polyether ketone ketone (PEKK) resin, polyarylate (PAR) resin, polyether nitrile (PEN) resin, phenolic resin, phenoxy resin, polytetrafluoroethylene resin, and other fluorine-based resins, polystyrene resin, Polyolefin resins, polyurethane resins, polyester resins, polyamide resins, polybutadiene resins, polyisoprene resins, thermoplastic elastomers such as fluorine resins, copolymers, modified products, and two or more types of It may be a de resin. In particular, PPS resin is used from the viewpoint of heat resistance and chemical resistance, polycarbonate resin and styrene resin are used from the viewpoint of molded product appearance and dimensional stability, and polyamide resin is used from the viewpoint of strength and impact resistance of the molded product. More preferably used. In addition, depending on the required characteristics of the molded product to be obtained, flame retardants, weather resistance improvers, other antioxidants, heat stabilizers, ultraviolet absorbers, plasticizers, lubricants, colorants, compatibilizers, conductive fillers, etc. Can also be added.

  When the prepreg that can be used in the method for producing a fiber-reinforced composite of the present invention has a cut, the strength tends to decrease as the thickness of the divided prepreg increases. If it is assumed to be applied to a structural material, the thickness of the prepreg is preferably 500 μm or less. On the other hand, if the thickness is less than 50 μm, it is difficult to handle the prepreg, and the number of prepregs to be laminated for obtaining a laminate is very large, so the productivity is remarkably deteriorated. Therefore, it is preferable that it is 50 micrometers or more and 300 micrometers or less from a viewpoint of productivity.

  When high fluidity at the time of stamping molding is required, it is preferable to use a prepreg having a notch penetrating from the surface of the prepreg to the back surface in a direction crossing the reinforcing fiber.

  In this invention, you may use both the prepreg without a notch penetrated from the surface of a prepreg to the back surface in the same laminated body, and the prepreg with the notch penetrated from the surface of a prepreg to the back surface. In particular, when high fluidity at the time of stamping molding is required, it is preferable that the reinforcing fiber is cut by a notch penetrating from the front surface to the back surface of the prepreg. The length of the cut reinforcing fiber is not particularly limited, but is preferably 10 mm or more and 100 mm or less from the viewpoint of mechanical properties and fluidity. In particular, 10 mm or more and 50 mm or less is more preferable in order to achieve both sufficient mechanical properties and shaping at the time of stamping molding.

  When using a prepreg having a cut as a prepreg that can be used in the method for producing a fiber-reinforced composite of the present invention, it can be obtained by making a cut using a laser marker, a sample cutting machine, a cutting die or the like. It is preferable that the incision is made using a laser marker because it has the effect of processing a complex incision such as a curve or a zigzag line at high speed, and the incision is performed using a sample cutting machine. Since it has the effect that a large prepreg layer of 2 m or more can be processed, it is preferable. Furthermore, it is preferable that the cut is made by using a punching die because there is an effect that processing can be performed at high speed.

When high mechanical properties are required, it is preferable to use a prepreg containing reinforced fibers oriented in one direction and a thermoplastic resin (a prepreg having no notch penetrating from the front surface to the back surface). . A plurality of the prepregs can be laminated to form a laminate.
The absolute value of the angle θ (°) formed by the incision and the orientation direction of the reinforcing fibers is preferably in the range of 2 ° to 45 °. If the absolute value of θ is greater than 45 °, high fluidity can be obtained. Little improvement in mechanical properties. Particularly, when the absolute value of θ is 45 ° or less, the mechanical characteristics are remarkably improved. On the other hand, if the absolute value of θ is smaller than 2 °, sufficient fluidity and mechanical properties can be obtained, but it is difficult to make a stable cut. That is, when the incision lies on the fiber, when the incision is made, the fiber easily escapes from the blade, and in order to make the fiber length L 100 mm or less, the absolute value of θ is more than 2 °. If it is smaller, at least the shortest distance between the cuts becomes smaller than 0.9 mm, making it difficult to insert the cuts.

  In the next step, the direction of the reinforcing fiber is unidirectional, pseudo-isotropic, or 0 ° / 90 ° alternating lamination, random lamination, etc. A laminated body is prepared by laminating so as to obtain a laminated structure of As a prepreg constituting this laminate, only a prepreg without a cut may be used, or only a prepreg with a cut may be used, or both a prepreg without a cut and a prepreg with a cut may be used. May be used. At this time, for ease of handling, prepregs forming adjacent layers can be laminated by spot welding with an ultrasonic welding machine to form a laminate.

  The laminated body that can be used in the method for producing a fiber-reinforced composite of the present invention is that a plurality of prepregs are laminated so that the directions of the reinforcing fibers are quasi-isotropic. Is preferable in terms of reducing the size. The layered structure is a layer in which four layers of 0 ° / 45 ° / 90 ° / −45 ° are repeated n times symmetrically ([0 ° / 45 ° / 90 ° / −45 °] ns) or 0 ° / 60. It is preferably pseudo-isotropic expressed by symmetrically laminating three repetitions of 3 layers of ° / -60 ° ([0 ° / 60 ° / -60 °] ns) (n is an integer of 1 or more) And s represents a symmetric stacked configuration). By using pseudo isotropic, warping of the laminate can be suppressed. In addition, when forming a fiber-reinforced composite used as a structural material by molding, it is necessary to withstand loads from multiple directions. Also from the viewpoint of mechanical properties, the fiber reinforced composite is preferably laminated in a pseudo isotropic manner to withstand general-purpose use.

  The laminate that can be used in the method for producing a fiber-reinforced composite according to the present invention is a laminate in which prepregs whose reinforced fibers are included in the prepreg have an orientation of 0 degrees and 90 degrees are alternately laminated. This is preferable in that the anisotropy of the strength of the body is reduced.

  The thickness of the integrated laminate according to the present invention is preferably 0.5 to 10 mm. If it is less than 0.5 mm, the number of laminated prepregs is small, and the influence of the overlapping portion of the cut portions becomes large, and it tends to become a starting point of fracture, which is not preferable. When the thickness is 0.5 mm or more, the number of stacked layers increases, and even when the cuts overlap, they can be supplemented with other layers. If it exceeds 10 mm, the circumference difference between the inner layer and the outer layer becomes large at the corner R portion, bridging may occur on the inner layer side, the notched portion on the outer layer side may be widened, an opening portion may be formed, and the strength may be reduced. .

  Next, the fiber reinforced composite obtained by the manufacturing method mentioned later for details is demonstrated.

  As for the obtained fiber reinforced composite, as shown in FIG. 2, the shortest cross-sectional length L1 (202 of the cross-sectional lengths measured along the shape of the fiber reinforced composite 201 cut in the direction in which the laminate is pressed is used. ) And the longest cross-sectional length L2 (203) longer than L1 is preferably in the range of 0.3 <L1 / L2 <0.96. In the case of 0.3 or less, since the difference between L1 and L2 becomes large, a large tension is applied to L2, so that the cut portion is widened and becomes an opening, which may lead to a decrease in strength. In the case of 0.96 or more, the effect of improving the formability by making a notch is not fully utilized, and the efficiency is not good in view of the notch insertion process.

  Further, the fiber reinforced composite 301 is preferably provided with a plurality of bent portions 302 as shown in FIG. As shown in FIG. 4, the bent portions 302 and 402 indicate portions having a certain curvature (radius: R). The radius R on the outer edge side of the bent portion 402 is preferably in the range of 2 to 5 times the thickness d (403) of the fiber reinforced composite 401. If it is less than 2 times, the circumferential length difference becomes large, so that the cut portion may expand and become an opening. If it exceeds 5 times, the effect of improving the formability by making the cut is not fully utilized, and the efficiency is not good in view of the step of inserting the cut.

  Of the plurality of bent portions 302 formed in the fiber reinforced composite 301, when two or more convex shaped portions 303 obtained from the adjacent bent portions 302 are included, the fibers are constrained between the convex shapes and the convex shapes. For this reason, bridging occurs, but when a prepreg laminate having a cut is used, the base material is elongated, so that bridging does not occur and it is preferable to form a beautiful shape.

Furthermore, the projected area Smm ² fiber-reinforced composite 201 a (301, 401) projected in the vertical direction, the ratio S / L between the maximum depth Lmm is preferably in the 1240mm below the range of 50 mm. If it is less than 50 mm, there is a possibility that the cut portion will spread and become an opening. If it exceeds 1240 mm, the effect of improving the formability by making a cut is not fully utilized, and the efficiency is not good in view of the process of inserting the cut. Next, the manufacturing method of a fiber reinforced composite is demonstrated in detail.

  As a method of molding the fiber-reinforced composite of the present invention, there is a sheet-like prepreg that does not penetrate from the surface of the prepreg composed of reinforcing fibers and a thermoplastic resin to the back surface, or a cut that penetrates from the surface of the prepreg to the back surface. A plurality of laminated sheet-shaped prepregs, and the laminated body is heated to a temperature equal to or higher than the melting point of the thermoplastic resin to melt the laminated body. At the time of heating, an unheated region is provided in at least a part of the laminated body. It is a manufacturing method for obtaining a fiber-reinforced composite by applying pressure along a mold having a three-dimensional curved surface adjusted to a temperature lower than the solidification temperature of the laminated body and cooling.

  Here, the solidification temperature is a crystallization temperature in the case of a crystalline polymer, and a glass transition temperature in the case of an amorphous polymer.

  The laminate is heated by a heating device exemplified by a far infrared heater, a heating plate, a high temperature oven, dielectric heating, high frequency heating and the like. The heating time and heating temperature required for heating the material differ depending on the matrix thermoplastic resin used and are not specified, but it is preferable that the heating is performed within the range of the melting point to the decomposition temperature of the matrix resin.

  As a technique for creating a non-heated region, it is effective to prevent heat from being transmitted to a portion that is desired to be unmelted during heating. For example, when heating using a far-infrared heater, place a metal frame or metal film on the part you want to melt, or just stick an aluminum tape and the far-infrared will not pass, so it will be unmelted. it can. Or you may make it not irradiate a far infrared ray only in the location which wants to make it unmelted. Alternatively, only the portion that is desired to be unmelted during heating may be cooled. For example, a cooling medium such as air having a temperature lower than the resin melting temperature may be applied only to a portion that is desired to be unmelted.

  The laminated body heated and melted is transported into a mold using a manual or transport device. The conveyance is preferably performed as quickly as possible, and a conveyance time of 30 seconds or less is preferable because the matrix temperature during pressing is not cooled.

  As a pressure applied to a laminated body in the said pressurization, Preferably it is 0.1-10 Mpa, More preferably, it is 0.2-3 Mpa. The pressure is a value obtained by dividing the pressing force by the area of the laminate. If it is this range, since it can be made to impregnate a thermoplastic resin between the reinforced fiber contained in a prepreg, it is preferable.

  After pressurizing and cooling to a temperature lower than the solidification temperature of the laminate, the upper mold is raised and removed to obtain a fiber-reinforced composite. When demolding, a fiber reinforced composite may be obtained using an extrusion pin or the like.

  Next, examples of the present invention and comparative examples will be described, but the present invention is not limited to these examples. In Table 2, the rows indicate examples or comparative examples. The row shows the presence or absence of unmelted parts of the heated laminate from the left, the next row shows the presence or absence of the cut of the heated laminate, and the next row shows the results of evaluating the formability, that is, the surface quality of the molded fiber reinforced composite. Show. X indicates a level where there is wrinkling in the flat part and bridging in the bent part and there is a practical problem, x indicates a level where there is wrinkle in the flat part and some bridging in the bent part, but there is no practical problem The level at which no wrinkles were observed at the part and no bridging was observed at the R part and no problem in practical use was marked as ◎.

Example 1
The prepreg used in the present invention is made of carbon fiber and nylon 6, and the end portion in the width direction perpendicular to the fiber direction of TenCate Cetex (registered trademark) TC910 is heat-welded to form a sheet having a size of 700 mm square. A unidirectional prepreg substrate was used.

  The sheet-like unidirectional prepreg base material was inserted in a fiber direction into a roller cutter having a blade disposed on a cylinder, and intermittent linear cuts were inserted. When the fiber length is 12 mm and the angle between the cut and the reinforcing fiber is θ, θ is 22 °.

  The fiber direction of the sheet-like prepreg was set to 0 °, and 8 sheet-like prepregs were laminated so as to be (0 ° / 45 ° / 90 ° / −45 °) s to obtain a laminate of prepregs.

  A far infrared heater was used as a method for preheating and melting the laminate. The laminate was heated with a far infrared heater until the laminate center temperature reached 260 ° C. to obtain a heated laminate. An unmelted portion was prepared in the heated laminate by providing an unheated region by placing an aluminum frame on a portion to be unmelted at the time of heating the laminate, the periphery of the laminate, and a width of 50 mm.

  The heated laminate was cold-pressed at a pressure of 3 MPa using a mold composed of an upper mold and a lower mold having cavities and depressions in a cavity heated to 150 ° C. to obtain a fiber-reinforced composite.

  The obtained fiber reinforced composite did not show wrinkles or bridging, had good surface quality, had no practical problem, and was evaluated as ◎.

(Example 2)
Using the prepreg of Example 1, a fiber reinforced composite was molded in the same manner as in Example 1 without inserting a notch, and the surface quality of the obtained fiber reinforced composite was evaluated. Although some bridging was observed on the surface of the fiber reinforced composite, it was at a level having no problem in practical use, and the evaluation was evaluated as “good”.

(Comparative Example 1)
Using the prepreg of Example 1, a cut was inserted in the same manner as in Example 1. A fiber reinforced composite was molded in the same manner as in Example 1 except that no unmelted part was provided when the laminate was heated, and the surface quality of the obtained fiber reinforced composite was evaluated. Wrinkles were observed on the surface of the fiber reinforced composite, and it was judged that there was a problem in practical use.

(Comparative Example 2)
A fiber reinforced composite was molded in the same manner as in Example 1 except that the prepreg of Example 1 was not used, no notch was inserted, and no unmelted portion was provided when the laminate was heated. The surface quality was evaluated. Wrinkles were observed on the surface of the fiber reinforced composite, bridging was observed in the corner R portion, and it was judged that there was a problem in practical use.

  Since the present invention can easily follow the molding of a three-dimensional shape such as the R portion and the concavo-convex shape and maintain the mechanical strength as a structural member, for example, it can be suitably used for aircraft members, automobile members, sports equipment, etc. Can do.

101: Prepreg 102: Laminated body 103: Metal frame 104: Heater 105: Heated laminated body 106: Heated laminated body melting part 107: Heated laminated body unmelted part 108: Lower mold 109: Upper molds 110, 201, 301, 401: Fiber reinforced composite 202: Cross-sectional length 203 of the fiber reinforced composite cut in the direction of pressing the fiber reinforced composite having the shortest peripheral length L1: In the direction of pressing the fiber reinforced composite having the longest peripheral length L2. Section lengths 302 and 402 of the cut fiber reinforced composite: bent portion 303: convex portion 403: thickness measurement point

Claims (7)

A method for producing a fiber-reinforced composite in which a laminate of a sheet-like prepreg base material composed of reinforcing fibers and a thermoplastic resin is heated, then pressed along a mold having a three-dimensional curved surface, and cooled. The unmolded part having at least a part of the laminated body as a non-heated region and the other molten part are provided, and the heated laminated body is adjusted to a temperature lower than the solidification temperature of the laminated body. A method for producing a fiber-reinforced composite, which is placed and the molten part is placed along the mold. The method for producing a fiber-reinforced composite according to claim 1, wherein reinforcing fibers aligned in one direction are used as the sheet-like prepreg base material. The method for producing a fiber-reinforced composite according to claim 1 or 2, wherein the sheet-like prepreg base material provided with a plurality of intermittent cuts, in which at least some of the reinforcing fibers are divided into a length of 10 to 100 mm, is used. The method for producing a fiber-reinforced composite according to claim 3, wherein an absolute value of an angle θ (°) formed by the cut and the orientation direction of the reinforcing fiber is in a range of 2 ° to 45 °. Of the cross-sectional lengths of the fiber reinforced composite cut in the direction of pressing the laminate, the ratio L1 / L2 between the shortest cross-sectional length L1 and the longest cross-sectional length L2 longer than L1 is 0.3 <L1. The method for producing a fiber-reinforced composite according to any one of claims 1 to 4, wherein /L2<0.96. A plurality of bent portions formed in a cross section of the fiber reinforced composite cut in a direction in which the laminate is pressed along the reinforcing fiber orientation direction of the laminate, and the curvature radius R of the bent portion is the fiber. The method for producing a fiber-reinforced composite according to any one of claims 1 to 5, which is in a range of 2 to 5 times the thickness d of the reinforced composite and has two or more convex portions by the bent portion. Fiber-reinforced composite according to claim 1 in a ratio S / L range is at least 50mm 1240mm or less of the fiber-reinforced composite projected area Smm ² and maximum depth Lmm projected in the vertical direction Manufacturing method.