JP2016179647A - Method for producing fiber-reinforced plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fiber-reinforced plastic which has a short cycle time and secures excellent flowability and excellent shape followability when shaping and molding an intermediate substrate on a sheet into a three-dimensional shape, and exhibits excellent surface quality and excellent dimensional stability when a fiber-reinforced plastic is pressurized and molded.SOLUTION: There is provided a method for producing a fiber-reinforced plastic for pressurizing a prepreg laminated in which prepregs formed by impregnating a reinforced-fiver with a thermosetting resin are laminated while bringing at least one surface thereof into contact with a mold, and curing the prepreg laminate by heating and molding the prepreg includes: pressurizing a prepreg laminate that has been heated in a range of ±10°C of such a temperature that a coefficient of friction between a prepreg and a mold is lower than the coefficient of friction between the prepreg and the prepreg, and the coefficient of friction between the prepreg and the mold becomes smallest; raising the temperature to a predetermined temperature; and curing the prepreg laminate while keeping the temperature.SELECTED DRAWING: Figure 7

Description

  The present invention ensures good fluidity and excellent shape followability when forming into a three-dimensional shape when pressure-molding fiber reinforced plastic, and exhibits good surface quality and excellent dimensional stability. The present invention relates to a method for producing fiber-reinforced plastic.

  Fiber reinforced plastic made of reinforced fiber and matrix resin is excellent in specific strength and specific elastic modulus, and not only in the field of transportation equipment such as aircraft structural members and automobile structural members, but also in general industrial fields such as pressure vessel members and golf shafts. The application is expanding and the demand is increasing year by year.

  These structural members often use a semi-cured intermediate base material in which continuous reinforcing fibers called prepregs are impregnated with a matrix resin, which are particularly excellent in mechanical properties among fiber reinforced plastics. Above all, the unidirectional prepreg with the fibers aligned in one direction improves the fiber volume content, maximizes the high elastic modulus and strength of the reinforced fiber, and pre-loads a highly functional matrix resin. The material quality is stabilized by impregnating with less variation.

  The most common method for molding fiber reinforced plastics using prepregs is autoclave molding in which prepregs are laminated and heated in a high temperature and high pressure kettle to cure the matrix resin and mold the fiber reinforced plastics. In addition, press molding is widely performed in which a prepreg laminate is preheated, the laminate in a softened state is supplied to a pair of male and female double-sided molds, and then pressed to obtain a molded body having a desired shape. Yes. In particular, press molding is characterized by the ability to mass-produce products with relatively uniform accuracy, and there is a high demand for high-speed, high-precision, and stable quality for mass production. Therefore, there is a high demand from the market regarding improvement of formability.

  Since the fiber reinforced plastic obtained by these molding methods is composed of continuous fibers, it exhibits excellent mechanical properties. In addition, since the continuous fibers are regularly arranged, it is possible to design by considering the required mechanical properties and exposed load conditions by designing the laminated structure, and the degree of freedom in design is high and the variation in mechanical properties is small. . However, on the other hand, the stretchability of the reinforcing fiber itself having a high elastic modulus is poor, and it is difficult to form a complicated three-dimensional shape such as an uneven portion or a corner portion. When a prepreg having such continuous fibers is shaped, the reinforcing fibers are stretched at places where the surface shape cannot be covered, and the reinforcing fibers buckle at the places where the prepregs are left, resulting in wrinkles. Is difficult to form. Even a prepreg having continuous fibers can be subjected to in-plane shear deformation if it is a base material in which a woven fabric is impregnated with a matrix resin, and shaping is easy. There was a problem that wrinkles occurred.

  On the other hand, as a molding method suitable for molding a three-dimensional member such as a concavo-convex portion, there is press molding using SMC (sheet molding compound). In this molding method, the SMC sheet which is made into a semi-cured state by impregnating a chopped strand, which is usually cut to about 25 mm, with a thermosetting matrix resin, is heated and pressed using a press. In general, before pressurization, the SMC is cut smaller than the shape of the molded body, placed in a mold, and molded into the shape of the molded body by pressurization. Therefore, it becomes possible to follow complicated shapes such as uneven portions and composite curved surfaces by flow. However, SMC has a problem that uneven distribution of the chopped strands and uneven alignment of the chopped strands are inevitably generated in the sheet processing process, so that in addition to the deterioration of the mechanical characteristics, the dispersion of the mechanical characteristics itself becomes large. . Furthermore, warping, sink marks, etc. are likely to occur especially in thin members, and application to main structural members is often difficult.

  Patent Document 1 discloses a hot forming method in which a prepreg laminate laminated in a flat plate shape is formed into a three-dimensional shape at a stretch as a molding process with excellent productivity. However, there is a problem that wrinkles and fiber stretching occur due to insufficient shape following ability of the prepreg during shaping, and the quality of the fiber reinforced plastic is lowered. As the thickness of the prepreg laminate is reduced to a fiber reinforced plastic, the thickness of the prepreg laminate is reduced. For this reason, the prepreg laminate formed at the part having a large shape change, for example, the corner portion, buckles and becomes wrinkled as the reinforced fiber is cured. Or, there is a molding defect that the fiber is stretched and does not follow the mold shape. In addition, there is a problem that voids are easily generated because it is difficult to apply a molding pressure directly under the reinforcing fiber where the tension is generated.

  Patent Document 2 discloses a technique in which a resin contained in a prepreg laminate is shaped to a temperature at which the resin is heated to a minimum viscosity and softened, and then heated to a curing temperature. However, in reality, the viscosity of the resin is too low and the resin is squeezed out from the pressurized prepreg laminate, while the reinforcing fibers hardly flow. In addition, this resin squeezing makes it difficult to control the fiber volume content Vf of the molded product, and in addition to variations in mechanical properties, the surface lacks resin and deteriorates the surface quality.

JP 2001-38752 A JP 2008-68534 A

  In view of the background art, the object of the present invention is to form an intermediate base material on a sheet into a three-dimensional shape by pressure molding, with a short cycle time, good fluidity, and excellent shape followability. It is an object of the present invention to provide a method for producing a fiber reinforced plastic that exhibits good surface quality and excellent dimensional stability when the fiber reinforced plastic is pressure-molded.

  The manufacturing method of the fiber reinforced plastic of the present invention employs the following means in order to solve the above-described problems. A method for producing a fiber reinforced plastic comprising forming a prepreg laminate in which a prepreg obtained by impregnating a reinforced fiber with a thermosetting resin is laminated, pressing at least one surface of the prepreg in contact with a mold, and curing by heating. The temperature of the friction coefficient between the prepreg and the mold is lower than the friction coefficient between the prepreg and the mold, and the temperature is within a range of ± 10 ° C. at which the friction coefficient between the prepreg and the mold is minimized. This is a method for producing a fiber reinforced plastic, in which the prepreg laminate is pressurized, heated to a predetermined temperature, and cured while maintaining the temperature.

  According to the present invention, it is possible to produce a fiber reinforced plastic that has a flat prepreg laminate with excellent shape following to a three-dimensional shape, good surface quality, and excellent dimensional stability in a short cycle time. it can.

a) is a sectional view showing the procedure of the friction coefficient measuring method in the present invention, and b) is a plan view showing a test piece used in the friction coefficient measuring method in the present invention. It is a conceptual diagram which shows an example of the cut pattern of the cut prepreg used by 1 aspect of this invention. It is a conceptual diagram which shows an example of the cut pattern of the cut prepreg used by 1 aspect of this invention. It is a conceptual diagram which shows an example of the cut pattern of the cut prepreg used by 1 aspect of this invention. It is a conceptual diagram which shows an example of the cut pattern of the cut prepreg used by 1 aspect of this invention. It is a conceptual diagram which shows an example of the cut pattern of the cut prepreg used by 1 aspect of this invention. a) is a front view showing an example of a procedure for molding fiber-reinforced plastic in the present invention, and b) is a top view showing an example of a procedure for molding fiber-reinforced plastic in the present invention.

  Hereinafter, the present invention will be described in detail.

  In the present invention, a prepreg obtained by impregnating a reinforcing fiber with a thermosetting resin is used as a base material. The fiber volume content Vf of the prepreg is preferably in the range of 45 to 65%. Sufficient fluidity can be obtained with a Vf of 65% or less, and the lower the Vf, the better the fluidity. However, if Vf is less than 45%, the mechanical properties required for the structural material may not be obtained. In view of the relationship between fluidity and mechanical properties, Vf is more preferably in the range of 55 to 60%.

  Examples of reinforcing fibers constituting the prepreg include brittle fibers such as carbon fibers, aramid fibers, and glass fibers, and ductile fibers such as metal fibers and synthetic fibers. Among them, carbon fiber is particularly lightweight among these reinforcing fibers, and has particularly excellent properties in specific strength and specific elastic modulus. In addition, it has excellent heat resistance and chemical resistance, so it is suitable for structural members. It is. Of these, PAN (polyacrylonitrile) -based carbon fibers from which high-strength carbon fibers can be easily obtained are preferred.

  Moreover, the thermosetting resin which comprises a prepreg is used as a matrix resin. Examples of thermosetting resins include epoxy resins, vinyl ester resins, phenol resins, unsaturated polyester resins, etc., as long as the resin undergoes a crosslinking reaction by heat and forms at least a partial three-dimensional crosslinked structure. Good. The form of the thermosetting resin in the prepreg is preferably a semi-cured state having excellent tackiness because it is necessary to press-bond the prepregs together during prepreg lamination. Among these, an epoxy resin is preferable in consideration of tackiness in the attaching process and mechanical characteristics when a fiber reinforced plastic is used.

  In the present invention, a prepreg laminate in which prepregs are laminated is pressed while at least one surface thereof is in contact with a mold, and the matrix resin is cured by heating to form a fiber reinforced plastic. At that time, the friction coefficient between the prepreg on the surface constituting the prepreg laminate and the mold, that is, the friction coefficient between the prepreg and the mold surface is the friction coefficient between the prepreg and prepreg constituting the prepreg laminate, that is, between the prepregs. The prepreg laminate is heated and pressed within a temperature range of ± 10 ° C. at which the friction coefficient between the prepreg and the mold is minimized. Then, the temperature is raised to a predetermined temperature, and the matrix resin is cured while maintaining the temperature. When pressure is applied in a temperature range where the friction coefficient between prepregs is lower than the friction coefficient between the prepreg and the mold surface, the prepreg layer excluding the prepreg on the outermost layer of the prepreg laminate preferentially flows, and the There is a problem that the follow-up of the prepreg on the surface layer is delayed, and the surface quality of the fiber-reinforced plastic obtained is deteriorated. Even if the coefficient of friction between the prepreg and the mold surface is lower than the coefficient of friction between the prepregs, the flow is limited if the coefficient of friction between the prepreg and the mold surface is large. The fiber reinforced plastic that exhibits the best surface quality can be obtained by pressurizing within the range of the temperature ± 10 ° C. at which the friction coefficient is minimum.

  From the viewpoint of shortening the molding time, it is better that the time required for raising the temperature to a predetermined temperature after pressurizing the heated prepreg laminate is as short as possible, and the prepreg laminate is sufficiently stretched after pressurization. The temperature should be raised to a predetermined temperature in stages. Moreover, the above-mentioned temperature rise from the temperature at the time of pressurization to a predetermined temperature means a temperature increase at which the temperature difference ΔT from the temperature at the time of pressurization to the predetermined temperature becomes 10 ° C. or more. On the other hand, as the temperature difference ΔT for increasing the temperature increases, the temperature increasing time also becomes longer. Therefore, from the viewpoint of shortening the molding time, the temperature difference ΔT for increasing the temperature preferably does not exceed 80 ° C., more preferably It is preferable to determine the temperature to be maintained after the temperature rise so as not to exceed 40 ° C.

  In the present invention, the fiber-reinforced plastic is molded by raising the temperature in two stages: the temperature at which the prepreg laminate is pressurized and shaped, and the temperature at which the matrix resin is cured by raising the temperature. And the temperature which pressurizes and shapes a prepreg laminated body is controlled, and a prepreg laminated body is heat-pressed and shaped at the temperature suitable for shaping. This makes it possible to mold the fiber reinforced plastic in a short time compared to the process of curing the matrix resin at a constant temperature.

  As shown in FIG. 1, the friction coefficient in the present invention is a test piece in which one central layer 3 is sandwiched between two members 4 and the load obtained when the sandwiched central layer is pulled out, It is defined by the value obtained by dividing by 2 times the load (vertical load) pressed vertically from the outside of the plane. The reason for the double is that there are two interfaces between the central layer and the member that receive frictional resistance. The member 4 is made of the same material and the same surface roughness as the mold, and the value measured using the prepreg as the central layer 3 is the friction coefficient between the prepreg and the mold surface. When forming by performing a process such as applying a lubricant or a mold release agent to the mold, the member 4 is subjected to the same process as the mold, and the surface condition of the member 4 is the same as that of the mold. As a test. When the film is formed between the prepreg laminate and the molding die under the condition that a film or the like is interposed, when the film stretches like the prepreg laminate and slides between the mold surface and the film, the film is used as the central layer 3. And the friction coefficient between the film and the member 4 may be the friction coefficient between the prepreg and the mold surface. On the other hand, when the film and the mold are integrated and the prepreg expands and slides between the prepreg and the film, The surface of the mold is regarded as a film, and the friction coefficient measured using the film as the member 4 is defined as the friction coefficient between the prepreg and the mold surface. Moreover, a prepreg is used as the member 4, and the value when the member 3 is also measured using the prepreg is a friction coefficient between the prepregs.

  As a test method, the central layer 3 is cut out (when the central layer 3 is a prepreg, it is cut out so as to be long in the fiber direction), and the width is 30 mm (when the central layer 3 is a prepreg, the direction perpendicular to the fiber), In the range of 60 mm in length (in the fiber direction when the central layer 3 is a prepreg), the two members 4 and the central layer 3 3 so that the central layer 3 overlaps between the two members 4. Laminate the sheets. In addition, a fiber direction means the orientation direction of a reinforced fiber, and a fiber orthogonal direction means a direction perpendicular | vertical to the orientation direction of a reinforced fiber.

  When the member 4 and the center layer 3 are both prepregs, they are laminated so that they are in the same fiber direction. Then, a spacer 5 made of the same material as that of the central layer 3 having a width of 30 mm (in the same fiber direction when the central layer 3 is a prepreg) is installed so as to be in contact with the overlap portion of the central layer 3 to prepare a test piece. Since the area of the overlap part decreases with the drawing and the area to be pressed with the pressure plate 1 is biased, there is a possibility that a high load may be applied locally due to the pressure plate hitting, so a spacer is arranged in the direction opposite to the drawing, Prevent the platen from tilting.

  A constant vertical load is continuously applied during the test while adjusting the temperature to the test temperature with the pressure plate 1 having a heat source up to a range of 20 mm in length of the overlap portion and the spacer (30 mm in width and 80 mm in length). After applying a vertical load to the test piece with a pressure plate adjusted to the test temperature and holding it for a certain period of time, the central layer is drawn in the longitudinal direction (in the fiber direction when the central layer 3 is a prepreg) at a constant drawing speed. The frictional coefficient is calculated by dividing the pulling load by the vertical load applied to the overlap portion (30 mm width and 80 mm length at the start of the test). Here, since the area of the overlap part where the center layer receives the vertical load is reduced in both the drawing and the area of the overlap part (width 30 mm, length 60 mm-the range of the drawing displacement) converted by the drawing displacement as appropriate, the load is applied by the spacer. The vertical load applied to the overlap part is calculated proportionally to receive the vertical load with the total area (width 30mm, length 20mm), and the pulling load is divided by twice the vertical load. Is the coefficient of friction.

  The coefficient of friction changes not only with temperature but also with drawing speed, normal stress, and time. In the present invention, a temperature-controlled pressure plate is pressed against the test piece by applying a vertical load of 192 N, and after one minute is held, drawing is started. The drawing speed is 0.17 mm / min, and the pulling load at 3 minutes after the start of drawing is divided by the vertical load applied to the overlap at that time to obtain the friction coefficient, and this test is repeated with five test pieces. The average value is defined as the friction coefficient in the present invention.

  In the present invention, the temperature at which the prepreg laminate is heated during shaping is the friction between the prepreg and the mold surface at each test temperature when the test temperature is changed in increments of 10 ° C. according to the method for measuring the friction coefficient. The coefficient is a temperature at which the friction coefficient between the prepreg and the mold surface is smaller than the friction coefficient between the prepregs, and the temperature at which the friction coefficient between the prepreg and the mold surface is minimized. To do. That is, the temperature ± 10 ° C. at which the coefficient of friction between the prepreg and the mold surface is the minimum is the step temperature at which the coefficient of friction between the prepreg and the mold surface measured by changing the test temperature in steps of 10 ° C. shows the minimum value. Means.

  As a preferred embodiment of the present invention, the prepreg laminate is preferably pressed by a double-sided mold. In forming a three-dimensional complicated shape such as an uneven portion or a complex curved surface, good shape followability and good surface quality can be obtained by using a pair of male and female high-force forcing. Moreover, by using a double-sided mold, the prepreg laminate can be uniformly heated quickly from a mold having a large heat capacity.

  Preferably, when pressurizing the prepreg laminate with a double-sided mold, the prepreg laminate is preferably arranged without contacting any mold surface until clamping. When heated in a state where the prepreg laminate is placed on a temperature-controlled mold surface, in the case of a thick prepreg laminate, temperature unevenness and uneven curing of the matrix resin occur in the prepreg laminate. The outermost layer of the prepreg laminate that is in contact with the mold surface may harden and may not exhibit good fluidity. Using a blank folder, etc., by gripping the peripheral edge of the prepreg laminate, it can be placed without contacting any mold surface until mold clamping, while pulling into the double-sided mold during mold clamping By clamping and pressurizing, molding is possible without contacting any mold surface until clamping. More preferably, the temperature of the prepreg laminate held by the blank folder is adjusted with warm air or an IR heater.

  Preferably, in the present invention, a prepreg formed by impregnating a reinforcing fiber aligned in one direction with a thermosetting resin is used as the base material. When using a woven prepreg impregnated with a matrix resin as a reinforced fiber, the shape followability is high by shear deformation in the in-plane direction, but the reinforced fiber is undulated in the thickness direction. The high elastic modulus and high strength characteristics possessed cannot be fully utilized, and there are limits to the mechanical characteristics that can be realized. On the other hand, since the reinforcing fibers are oriented in one direction, the reinforcing fibers can be packed most closely and are straightly arranged, so that the high mechanical properties of the reinforcing fibers can be utilized to the maximum.

  More preferably, at least one prepreg of the prepreg laminate composed of prepregs in which reinforcing fibers are aligned in one direction is composed of reinforcing fibers having a fiber length of 10 to 300 mm by a plurality of cuts. It is good to make it the cut prepreg made. When a prepreg having continuous fibers is shaped into a three-dimensional complex shape, there is a concern that the reinforcing fiber is stretched at a location where the surface shape cannot be covered, and the reinforcing fiber is buckled at a location where the prepreg is left, resulting in wrinkles. Since the fiber becomes discontinuous due to the plurality of cuts, the prepreg can be extended in the fiber direction. The shape following property of the prepreg laminate can be controlled by inserting a cut into only a portion where the surface shape cannot be covered, for example, a corner portion where pressure is hardly applied. By setting the fiber length L of the reinforcing fiber divided by the cutting to 300 mm or less, the above-described stretching of the reinforcing fiber can be effectively suppressed. When the fiber length L is less than 10 mm, since the distance between the cuts approaches, there is a problem that when a load is applied to the fiber reinforced plastic, cracks are easily connected and the strength is reduced. Considering the relationship between the shape followability and the mechanical properties, the fiber length L of the reinforcing fiber is more preferably in the range of 15 to 100 mm. More preferably, the area in which fibers of 10 mm or less are oriented is smaller than 5% of the proportion of the prepreg layer. In addition, the fiber length L is a fiber length divided | segmented by arbitrary notch | incisions and the notch | nearest incision (cutting which becomes a pair) in a fiber direction, as shown to FIGS.

  As an embodiment in which the present invention is implemented, when producing a fiber reinforced plastic in which the projected area of the fiber reinforced plastic to be produced is larger than the projected area of the prepreg laminate, the stretching direction of the prepreg laminate during molding and the reinforcement It is preferable to use a cut prepreg in a layer whose angle α formed with the fiber orientation direction is within ± 20 °. Thereby, the fiber does not stretch in the extending direction, and good shape following property can be realized. The projected area of the fiber reinforced plastic produced is larger than the projected area of the prepreg laminate, for example, using a pair of male and female double-sided molds having a cavity wider than the projected area of the prepreg laminate. There is a method in which the body is pressed (stretched) in the in-plane direction and pressure-molded.

A prepreg with reinforced fibers aligned in one direction has anisotropy in the fluidity between the fiber direction and the direction perpendicular to the fiber when the fiber flows during molding. It is important to laminate the fibers in different directions. In particular, the homogeneity of the flow during molding is an isotropic lamination such as [0/90] _ns , [0 / ± 60] _ns , and [45/0 / −45 / 90] _ns , and a symmetric lamination. In view of the reduction of warpage in the case of fiber reinforced plastic, it is preferable. On the other hand, when stretched in the direction perpendicular to the fiber, the fibers can be easily dispersed and stretched by the flow of the matrix resin, but when stretched in the fiber direction, a sufficient stretch amount cannot be secured due to the high elastic modulus of the reinforcing fiber. . In particular, when the angle α between the stretching direction and the orientation direction of the reinforcing fiber is within ± 20 °, the stretch amount cannot be secured due to the high elastic modulus of the reinforcing fiber, so that the layer is a cut prepreg. Thus, the amount of expansion can be ensured.

  As an embodiment in which the present invention is implemented, the prepreg laminate before molding is a flat plate shape, and the fiber-reinforced plastic to be manufactured is a three-dimensional shape having a curved surface at least partially, and bending is applied during molding It is preferable to use a cut prepreg in the layer on the tension side of the neutral axis of the body. Since the layer to which tension is applied does not stretch, the compressive force that generates wrinkles applied to the layer on the compression side of the neutral axis can be reduced.

  The cutting prepreg in the present invention is preferably provided with a plurality of intermittent cuts in a direction crossing the reinforcing fibers at least partially in view of mechanical properties, and the cutting is in a direction perpendicular to the orientation direction of the reinforcing fibers. The projection length Ws should be within the range of 30 μm to 1.5 mm, so that substantially all of the reinforcing fibers are substantially surrounded by the intermittent cuts in the longitudinal direction of the reinforcing fibers. It is good that it is divided by cutting. By making all the fibers have a predetermined length or less by the pair of cuts, it is possible to ensure followability to the three-dimensional shape and suppress the tension of the reinforcing fibers. By reducing Ws, the amount of fibers cut by each cutting is reduced, and strength improvement is expected. In particular, when Ws is 1.5 mm or less, a great improvement in strength is expected. On the other hand, when Ws is smaller than 30 μm, it is difficult to control the cutting position, and it is difficult to make all the fibers have a predetermined length or less due to the pair of cuttings, and the reinforcing fibers may be stretched during molding. is there. Here, as shown in FIGS. 2, 4, 5, and 6, the “projected length Ws” is a direction perpendicular to the orientation direction of the reinforcing fibers (fiber orthogonal direction 8) in the plane of the prepreg layer. Is the projection plane, and refers to the length when projected perpendicularly to the projection plane from the cut (fiber direction 7).

  As a preferred embodiment of the present invention, when the angle formed by the incision direction of the incision and the orientation direction of the reinforcing fibers is θ, the absolute value of θ is preferably in the range of 2 to 25 °. As shown in FIG. 3, in the case of continuous cutting, the fiber length L can be controlled to be constant, and variations in mechanical characteristics and three-dimensional shape followability can be reduced. As shown in FIGS. 4 to 6, in the case of intermittent cutting, the projection length Ws is made smaller than the cutting length Y because the absolute value of θ is in the above range. Therefore, it is possible to provide industrially stable cuts as small as 1.5 mm or less, and even during continuous cutting, the prepreg is unlikely to break apart and is easy to handle as a prepreg. Excellent. In particular, when the absolute value of θ is 25 ° or less, the mechanical properties, particularly the tensile strength, are remarkably improved. On the other hand, if the absolute value of θ is smaller than 2 °, it becomes difficult to make a stable cut. That is, when the incision direction falls with respect to the fiber orientation direction, the fiber easily escapes from the blade when making the incision, and the shortest distance between the incision rows 13 in the example of FIG. It becomes small and it becomes difficult to insert while ensuring the positional accuracy of the cut. In view of the relationship between the ease of controlling the cutting and the mechanical characteristics, it is more preferably in the range of 5 to 15 °. More preferably, the projection length Ws is in the range of 30 μm to 1.5 mm, and the absolute value of θ is in the range of 2 to 25 °.

  As a preferable cut pattern in the cut prepreg, as shown in FIG. 4, intermittent cuts are inserted linearly and in parallel to form rows 13, and the distance X between rows is in the range of 1 to 5 mm. It is good. When the fiber length L is the same, the shortest distance between the cuts can be maximized by making the straight cuts in the same direction. In addition, the incision is inserted by rolling the perforated rotating round blade on a straight line, or by inserting a cut corresponding to the pulse period by scanning a laser pulse laser at a high speed on a straight line. A highly efficient cutting insertion method can be expected.

  As another preferred cut pattern, as shown in FIG. 5, intermittent cuts are inserted in a straight line, the absolute values of θ are substantially the same, and cuts having positive and negative angles are substantially omitted. It should be half. When laminating the obtained cut prepreg, if the diagonal cut is in one direction, even if the prepreg is in the same fiber direction, the direction of the cut differs depending on whether the prepreg is viewed from the front or the back. Therefore, when manufacturing fiber reinforced plastics, there is a possibility that the labor for controlling the laminating procedure for laminating the same number of the same fiber direction with the same cutting direction so that the cutting direction will be the same every time will be increased. is there. If the absolute value of the inclination of the cut from the fiber direction is the same, and the cut pattern is a half of the positive and negative corner cuts, it is possible to laminate in the same manner as a normal continuous fiber prepreg .

  As a preferred mode of the cutting prepreg, as shown in FIG. 5, among the cuttings close to an arbitrary cutting, there is a cutting with different positive and negative values of θ that is the shortest distance than a cutting with the same positive and negative values of θ. There should be four or more. Since the movement of the fiber end is determined by the relationship between the cutting angle and the fiber direction, the adjacent cuttings have the same shape, an angle in the opposite direction, because the prepreg cut insertion part at the time of three-dimensional shape tracking When viewed macroscopically, in-plane isotropy after molding is ensured.

  Furthermore, as a preferable aspect of the cut prepreg, as shown in FIG. 6, intermittent cuts are inserted with straight lines and substantially the same length Y, and the shortest distance between adjacent cuts is the cut length. It should be longer than Y. From the viewpoint of mechanical properties, the fiber reinforced plastic breaks when the cuts that are discontinuities of the fibers are connected by cracks. By using a cut pattern in which in-plane notches are separated from each other, there is an effect of suppressing crack connection in at least the same plane, and the strength is improved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to the invention as described in an Example. First, the method for measuring the friction coefficient between prepregs and the friction coefficient between the prepreg and the mold surface, the molding method of the fiber reinforced plastic, and the preparation method of the prepreg used in the examples will be described.

(1) Method for measuring friction coefficient between prepregs The friction coefficient between prepregs was measured by the following operations (a) to (c).

  (A) Range of 30 mm in width and 60 mm in length of the second prepreg cut to 30 mm in width and 150 mm in length to the first prepreg cut to 40 mm in width and 150 mm in length with 0 ° as the length direction After stacking a spacer prepreg 30 mm wide and 20 mm long so as to be in contact with the overlap portion of the second layer, a third layer prepreg 40 mm wide and 150 mm long 1 A test piece was prepared by stacking so as to overlap the layer. Thereafter, a release paper having a width of 40 mm and a length of 150 mm was attached to the test piece so as to overlap the first and third layers.

  (B) The upper and lower pressure plates having the heating source in the range including the overlap portion and the spacer length (range of width 30 mm, length 80 mm) were adjusted to a predetermined temperature.

(C) Between the upper and lower pressure plates temperature-controlled at a predetermined temperature, the test piece prepared in (a) with the release paper attached is sandwiched, a constant vertical load of 192N is applied, and after 1 minute, the second layer The prepreg was drawn in the fiber direction at a drawing speed of 0.17 mm / min, and the value obtained by dividing the drawing load by twice the vertical load applied to the overlap portion was calculated as the individual friction coefficient between the prepregs. The reason for the double is that there are two prepreg surfaces that receive frictional resistance. As the pull-out load, the pull-out load after 3 minutes of the test, that is, the pull-out displacement of 0.5 mm was used. Since the area of the overlap portion where the second layer prepreg receives a vertical load decreases with the drawing, the vertical load applied to the overlap portion is converted as follows by the drawing displacement.
Vertical load applied to the overlap part = 192N x (60mm-extraction displacement) / (80mm-extraction displacement)

  That is, the vertical load applied to the overlap portion at the drawing displacement of 0.5 mm is 192 × (60−0.5) ÷ (80−0.5) = 143.7.

  About five test pieces, the individual friction coefficient was measured and the average value was made into the friction coefficient between prepregs.

(2) Method of measuring friction coefficient between prepreg and mold surface The friction coefficient between the prepreg and the mold surface was measured by the following operations (a) to (c).

  (A) The first side metal plate (material: SS400, arithmetic average roughness: 3.2) having a width of 40 mm and a length of 150 mm with the long side as the length direction, and a width of 30 mm with 0 ° as the length direction The prepregs cut to a length of 150 mm are laminated so as to overlap in the range of 30 mm in width and 60 mm in length, and further, a prepreg for a spacer having a width of 30 mm and a length of 20 mm is laminated so as to be in contact with the overlap portion. A third-layer metal plate (material: SS400, arithmetic average roughness: 3.2) having a length of 40 mm and a length of 150 mm was laminated so as to overlap with the first layer to prepare a test piece. Thereafter, a release paper having a width of 40 mm and a length of 150 mm was pasted so as to overlap the first and third layers.

  (B) The upper and lower pressure plates having a heating source in a range including the overlap portion and the spacer length (range of width 30 mm, length 80 mm) were temperature-controlled.

(C) Between the upper and lower pressure plates temperature-controlled at a predetermined temperature, the test piece prepared in (a) with the release paper attached is sandwiched, a constant vertical load of 192N is applied, and after 1 minute, the second layer The prepreg was drawn in the fiber direction at a drawing speed of 0.17 mm / min, and the value obtained by dividing the drawing load by twice the vertical load applied to the overlap was calculated as the individual coefficient of friction between the prepreg and the mold surface. The reason for the double is that there are two prepreg surfaces that receive frictional resistance. As the pull-out load, the pull-out load after 3 minutes of the test, that is, the pull-out displacement of 0.5 mm was used. Since the area of the overlap portion where the second layer of the prepreg receives the vertical load decreases with the drawing, the vertical load applied to the overlap portion was converted as follows by the drawing displacement.
Vertical load applied to the overlap part = 192N x (60mm-extraction displacement) / (80mm-extraction displacement)

  That is, the vertical load applied to the overlap portion at the drawing displacement of 0.5 mm is 192 × (60−0.5) ÷ (80−0.5) = 143.7.

  With respect to the five test pieces, individual friction coefficients were measured, and the average value was taken as the friction coefficient between the prepreg and the mold surface.

(3) Molding method of fiber reinforced plastic Fiber reinforced plastic was molded by the following operations (a) to (d).

  (A) A unidirectional carbon fiber reinforced prepreg produced by the method described in (4) or (5) described later is inserted in a fiber cutter into a roller cutter having a blade disposed on a cylinder, and intermittent linear cuts are made. Inserted with the cut pattern of FIG. The fiber length L is 24 mm, the absolute value of θ is 14 °, and Ws is 0.25 mm. The same number of cuts with a θ of + 14 ° and a cut with θ of −14 ° were inserted into the prepreg. All the incisions were closest to the incision with the opposite inversion angle, and there were incisions with the opposite in positive and negative of the four incision angles closer to the incision with the same sign. . Moreover, there was no adjacent cut within the radius of the cut length Y from every point of the cut. The incision row 13 has a cut length Y of 1 mm and is arranged at a pitch of 1 mm. The incision prepreg is cut by dividing the fibers by incisions corresponding to every other incision row. Produced.

(B) The obtained cut prepreg was cut to a size of 100 mm square in the directions of 0 ° and 45 °, and laminated in a 16-layer pseudo-isotropic manner with a laminated structure of [ _45/0 / −45 / 90] _2s , A 100 mm square prepreg laminate was prepared.

  (C) The mold in the molding is a double-sided mold as shown in FIG. 7, and the lower mold 15 has a concave shape. The long side direction is the length direction, and the width direction is 100 mm, the length direction. The upper die 14 has a convex shape, and a double-sided die having a shape that fills the cavity portion of the lower die is used. The material of the mold is SS400, and the surface arithmetic average roughness of the tool surface in contact with the prepreg laminate is 3.2. In a state where the double-sided mold is heated and adjusted to the shaping temperature T1 in advance, in the center of the lower mold cavity, the length direction of the mold is the 0 ° direction of the prepreg laminate 16 produced in (b). After the prepreg laminate was placed in the mold, the mold was closed, and the temperature was adjusted at temperature T1 for 4 minutes to warm the laminate. At that time, the surface pressure applied to the prepreg laminate is only the weight of the upper mold.

  (D) 3 minutes after closing the mold, the mold was clamped and pressurized with a surface pressure of 3 MPa. Thereafter, the temperature was raised to the molding temperature T2, the temperature was maintained, and the prepreg laminate was cured. After a certain period of time, the prepreg laminate was removed from the double-sided mold to obtain a fiber reinforced plastic.

(4) Method for Producing Unidirectional Carbon Fiber Reinforced Prepreg A Unidirectional carbon fiber reinforced prepreg A was produced by the following operations (a) to (c).

(A) Preparation of thermoplastic resin particles 90 parts by mass of transparent polyamide (product name: “Grillamide (registered trademark)”-TR55, EMSER Werke), epoxy resin (product name: “Epicoat (registered trademark)” 828, Shell Petroleum Chemical Co., Ltd.) 7.5 parts by mass and a curing agent (product name: “Tomide (registered trademark)” # 296, Fuji Chemical Industry Co., Ltd.) 2.5 parts by mass, chloroform 300 parts by mass and methanol 100 parts by mass Was added to a solvent mixture containing a homogeneous solution. Next, the obtained uniform solution was atomized with a spray gun for coating, mixed well, and sprayed toward the liquid surface of 3000 parts by mass of n-hexane in order to precipitate this solution. The precipitated solid was separated by filtration, thoroughly washed with n-hexane, and then vacuum-dried at 100 ° C. for 24 hours to obtain spherical epoxy-modified nylon particles (thermoplastic resin particles). Epoxy-modified nylon particles were classified using a CCE classifier manufactured by CCE Technologies. The 90% particle size of the obtained particles was 28 μm, and the CV value was 60%.

(B) Preparation of thermosetting resin composition (i) 13 parts by mass of “SUMICA EXCEL (registered trademark)” PES5003P (manufactured by Sumitomo Chemical Co., Ltd.) was added to 60 parts by mass of “Araldite (registered trademark)”. ) “MY9655 (manufactured by Huntsman Advanced Materials)” and 40 parts by weight of “Epon (registered trademark)” 825 (manufactured by Momentive Specialty Chemicals) were dissolved and then used as a curing agent, “Aradour ( (Registered Trademark) "96664-1 (manufactured by Huntsman Advanced Materials)" was kneaded in 45 parts by mass to prepare a thermosetting resin composition (1).

  (Ii) 16 parts by weight of PES5003P was added to 60 parts by weight of “Araldite (registered trademark)” MY9655 and 40 parts by weight of “Epon (registered trademark)” 825 in a kneader, and dissolved in (a). 80 parts by mass of the obtained thermoplastic resin particles were kneaded, and then 45 parts by mass of “Aradour (registered trademark)” 9664-1 as a curing agent was kneaded to prepare a thermosetting resin composition (2).

(C) Preparation of prepreg (b) The thermosetting resin composition (1) prepared in (i) was applied to release paper with a knife coater to prepare ^two 36.5 g / m ² resin films. Next, the produced two resin films are laminated on both sides of a sheet-like carbon fiber ("Treka (registered trademark)" T800S-12K, manufactured by Toray Industries, Inc.) arranged in one direction, and the roller temperature The resin was impregnated at 110 ° C. and a roller pressure of 0.25 MPa to prepare a preliminary prepreg. Further, the thermosetting resin composition (2) prepared in (b) (ii) was applied to a release paper with a knife coater to prepare ^two 29 g / m ² resin films, and the preliminary prepreg prepared earlier was used. Laminating on the surface, laminating a resin at a roller temperature of 100 ° C. and a roller pressure of 0.07 MPa, a unidirectional carbon fiber reinforced prepreg A having a unit area mass of 270 g / m ² and a mass fraction of a matrix resin of 34% was produced. .

(5) Production method of unidirectional carbon fiber reinforced prepreg B Unidirectional carbon fiber reinforced prepreg B was produced by the following operations (a) to (c).

(A) Preparation of thermosetting resin composition In a kneader, 40 parts by mass of bisphenol A type epoxy resin (product name: “jER (registered trademark)” 828, manufactured by Mitsubishi Chemical Corporation) and bisphenol A type epoxy resin ("JER (registered trademark)" 1001) and 30 parts by mass of a phenol novolac type epoxy resin ("jER (registered trademark)" 154) were kneaded and then dicyandiamide (DICY7, 4 parts by mass of Mitsubishi Chemical Corporation) and 3 parts by mass of 3- (3,4-dichlorophenyl) 1,1-dimethylurea (DCMU-99, manufactured by Hodogaya Chemical Co., Ltd.) as a curing accelerator As a viscosity modifier, 2 parts by mass of polyvinyl formal (“Vinylec (registered trademark)” K, manufactured by Chisso Corporation) was kneaded to prepare a thermosetting resin composition.

(B) Preparation of prepreg The thermosetting resin composition prepared in (a) was applied to release paper with a knife coater to prepare ^two 26 g / m ² resin films. Next, the produced two resin films are laminated on both sides of a sheet-like carbon fiber ("Treka (registered trademark)" T700S-12K, manufactured by Toray Industries, Inc.) arranged in one direction, and the roller temperature The resin was impregnated at 110 ° C. and a roller pressure of 0.25 MPa to prepare a unidirectional carbon fiber reinforced prepreg B having a unit area mass of 152 g / m ² and a mass fraction of the matrix resin of 34%.

Example 1
(4) Using the unidirectional carbon fiber reinforced prepreg A prepared by the method described in (1), the friction coefficient between the prepregs by the method described in (1), and the friction coefficient between the prepreg and the mold surface by the method described in (2). While measuring as follows, the fiber reinforced plastic was produced by the method of (3) as follows.

(A) Friction coefficient measurement between prepregs The measurement temperature was changed from 60 ° C to 200 ° C in increments of 10 ° C. The results are shown in Table 1.

(B) Measurement of friction coefficient between prepreg and mold surface The measurement temperature was changed from 60 ° C. to 200 ° C. in steps of 10 ° C. and measured. The results are shown in Table 1.

(C) Molding of fiber reinforced plastic The molding temperature T1 was 180 ° C., the molding temperature T2 was 200 ° C., and after reaching 200 ° C., the mold was removed from the mold after 46 minutes to obtain a fiber reinforced plastic.

  The projected area of the obtained fiber reinforced plastic was larger than the projected area of the prepreg laminate, and exhibited good extensibility. Further, the prepreg layer in contact with the mold surface was also well stretched and followed the shape of the obtained fiber reinforced plastic. In addition, squeezing out of the resin from the laminate was not confirmed. The time required for the molding was 4 minutes for the heating time of the laminate, 4 minutes for the heating process from 180 ° C. to 200 ° C. after pressing, and 46 minutes for the curing time after reaching 200 ° C. It took 54 minutes after installation in the mold.

(Example 2)
(5) Using the unidirectional carbon fiber reinforced prepreg B produced by the method described above, the friction coefficient between the prepregs by the method described in (1), and the friction coefficient between the prepreg and the mold surface by the method described in (2). While measuring as follows, the fiber reinforced plastic was produced by the method of (3) as follows.

(A) Interlayer friction coefficient measurement of prepreg Measurement was performed by changing the measurement temperature from 60 ° C to 150 ° C in increments of 10 ° C. The results are shown in Table 2.

(B) Measurement of coefficient of friction between mold surface and prepreg Measurement was performed by changing the measurement temperature from 60 ° C to 150 ° C in 10 ° C increments. The results are shown in Table 2.

(C) Molding of Fiber Reinforced Plastic The forming temperature T1 was 130 ° C. and the molding temperature T2 was 150 ° C. After reaching 150 ° C., the mold was removed from the mold after 30 minutes to obtain a fiber reinforced plastic.

  The projected area of the obtained fiber reinforced plastic was larger than the projected area of the prepreg laminate, and exhibited good extensibility. Further, the prepreg layer in contact with the mold surface was also well stretched and followed the shape of the obtained fiber reinforced plastic. In addition, squeezing out of the resin from the laminate was not confirmed. The time required for molding is 4 minutes for the heating time of the laminate, 4 minutes for the temperature increase process from 130 ° C. to 150 ° C. after pressing, and 30 minutes for the curing time after reaching 150 ° C. It took 38 minutes after installation in the mold.

(Comparative Example 1)
Using the unidirectional carbon fiber reinforced prepreg A produced by the method described in (4), a fiber reinforced plastic was produced by the method described in (3). In the above-described fiber reinforced plastic molding, the shaping temperature T1 and the molding temperature T2 were set to 180 ° C. The projected area of the obtained fiber reinforced plastic was larger than the projected area of the prepreg laminate, and exhibited good extensibility. Further, the prepreg layer in contact with the mold surface was also well stretched and followed the shape of the obtained fiber reinforced plastic. In addition, squeezing out of the resin from the laminate was not confirmed. However, in order to obtain a degree of curing equivalent to the fiber-reinforced plastic described in Example 1, it is necessary to maintain the molding temperature for 97 minutes after pressing, and the time required for molding is 4 minutes for the heating time of the laminate, The curing time was 97 minutes, and 101 minutes were required after the prepreg laminate was placed in the mold.

(Comparative Example 2)
Using the unidirectional carbon fiber reinforced prepreg A produced by the method described in (4), a fiber reinforced plastic was produced by the method described in (3). In the above-described fiber reinforced plastic molding, the shaping temperature T1 and the molding temperature T2 were set to 200 ° C. The projected area of the obtained fiber reinforced plastic was larger than the projected area of the prepreg laminate, and exhibited extensibility. On the other hand, the prepreg layer in contact with the mold surface did not follow the shape of the obtained fiber-reinforced plastic and was cured in the shape before pressing. In addition, squeezing out of the resin from the laminate was not confirmed. The time required for molding was 4 minutes for heating the laminate and 47 minutes for curing, and 51 minutes were required after the prepreg laminate was placed in the mold.

(Comparative Example 3)
Using the unidirectional carbon fiber reinforced prepreg A produced by the method described in (4), a fiber reinforced plastic was produced by the method described in (3). In the above-mentioned fiber reinforced plastic molding, the forming temperature T1 is set to 120 ° C. near the minimum viscosity, the molding temperature T2 is set to 200 ° C., and after reaching 200 ° C., the mold is removed from the mold when 45 minutes have elapsed, thereby reinforcing the fiber. Got plastic.

  The projected area of the obtained fiber reinforced plastic was larger than the projected area of the prepreg laminate, and exhibited extensibility. Further, the prepreg layer in contact with the mold surface also followed the shape of the obtained fiber reinforced plastic. On the other hand, squeezing out of the resin from the laminate was confirmed. The time required for molding is 4 minutes for the heating time of the laminate, 16 minutes for the heating process from 120 ° C. to 200 ° C. after pressing, and 45 minutes for the curing time after reaching 200 ° C., and the prepreg laminate is made of gold. It took 65 minutes after installation in the mold. Since the shaping temperature T1 is low, it takes time to raise the temperature to the molding temperature T2, and the molding time becomes long.

(Comparative Example 4)
Using the unidirectional carbon fiber reinforced prepreg B produced by the method described in (5), a fiber reinforced plastic was produced by the method described in (3). In the above-described fiber reinforced plastic molding, the shaping temperature T1 and the molding temperature T2 were set to 150 ° C. The projected area of the obtained fiber reinforced plastic was larger than the projected area of the prepreg laminate, and exhibited good extensibility. On the other hand, the prepreg layer in contact with the mold surface did not follow the shape of the obtained fiber-reinforced plastic and was cured in the shape before pressing. In addition, squeezing out of the resin from the laminate was not confirmed. The time required for molding was 4 minutes for the heating time of the laminate, and 33 minutes for the curing time. It took 37 minutes after the prepreg laminate was placed in the mold.

(Comparative Example 5)
Using the unidirectional carbon fiber reinforced prepreg B produced by the method described in (5), a fiber reinforced plastic was produced by the method described in (3). In the above-described fiber reinforced plastic molding, the shaping temperature T1 and the molding temperature T2 were set to 130 ° C. The projected area of the obtained fiber reinforced plastic was larger than the projected area of the prepreg laminate, and exhibited good extensibility. Further, the prepreg layer in contact with the mold surface also stretched well and followed the shape of the obtained fiber reinforced plastic. In addition, squeezing out of the resin from the laminate was not confirmed. However, in order to obtain a degree of curing equivalent to the fiber-reinforced plastic described in Example 2, it is necessary to maintain the molding temperature for 71 minutes after pressing, and the time required for molding is 4 minutes for the heating time of the laminate, The curing time was 71 minutes, and 75 minutes were required after the prepreg laminate was placed in the mold.

(Comparative Example 6)
Using the unidirectional carbon fiber reinforced prepreg B produced by the method described in (5), a fiber reinforced plastic was produced by the method described in (3). In the above-mentioned molding of fiber reinforced plastic, the forming temperature T1 is set to 110 ° C. which is near the minimum viscosity, the molding temperature T2 is set to 150 ° C., and after reaching 150 ° C., the mold is removed from the mold when 32 minutes have passed, thereby reinforcing the fiber Got plastic.

  The projected area of the obtained fiber reinforced plastic was larger than the projected area of the prepreg laminate, and exhibited extensibility. Further, the prepreg layer in contact with the mold surface was also well stretched and followed the shape of the obtained fiber reinforced plastic. On the other hand, squeezing out of the resin from the laminate was confirmed. The time required for molding is 4 minutes for the heating time of the laminate, 8 minutes in the temperature raising process from 110 ° C. to 150 ° C. after pressurization, and 34 minutes for the curing time after reaching 150 ° C. It took 46 minutes after installation in the mold. Since the shaping temperature T1 is low, it takes time to raise the temperature to the molding temperature T2, and the molding time becomes long.

1: pressure plate 2: release paper 3: center layer 4: member 5: spacer 6: cutting prepreg 7: fiber direction 8: fiber orthogonal direction 9: intermittent cutting 10: continuous cutting 11: intermittent Diagonal cut (positive angle with respect to fiber direction)
12: Intermittent diagonal cut (negative angle with respect to fiber direction)
13: Row of intermittent cuts 14: Mold (top)
15: Mold (bottom)
16: Pre-preg laminate 17: Mold cavity region 18: Laminate extension direction

Claims (9)

A method for producing a fiber reinforced plastic comprising forming a prepreg laminate in which a prepreg obtained by impregnating a reinforced fiber with a thermosetting resin is laminated, pressing at least one surface of the prepreg in contact with a mold, and curing by heating. The temperature of the friction coefficient between the prepreg and the mold is lower than the friction coefficient between the prepreg and the mold, and the temperature is within a range of ± 10 ° C. at which the friction coefficient between the prepreg and the mold is minimized. A method for producing a fiber-reinforced plastic, wherein after pressurizing the prepreg laminate, the temperature is raised to a predetermined temperature and cured while maintaining the temperature. The method for producing a fiber-reinforced plastic according to claim 1, wherein the prepreg laminate is pressed by a double-sided mold. The manufacturing method of the fiber reinforced plastics of Claim 2 which arrange | positions a prepreg laminated body, without contacting any mold surface until mold clamping. The method for producing a fiber-reinforced plastic according to any one of claims 1 to 3, wherein a prepreg in which reinforcing fibers are aligned in one direction is used as the prepreg. The method for producing a fiber reinforced plastic according to claim 4, wherein at least one prepreg in the prepreg laminate is a cut prepreg partly composed of reinforcing fibers having a fiber length of 10 to 300 mm by a plurality of cuts. A method for producing a fiber reinforced plastic in which the projected area of the fiber reinforced plastic to be produced is larger than the projected area of the prepreg laminate before molding, and the stretching direction of the prepreg laminate and the orientation direction of the reinforcing fibers during molding The manufacturing method of the fiber reinforced plastics of Claim 5 which uses a cutting prepreg for the layer whose angle (alpha) which forms is less than +/- 20 degrees. The prepreg laminate before molding has a flat plate shape, and the fiber-reinforced plastic to be produced has a three-dimensional shape having a curved surface at least partially, and the prepreg laminate to which bending is applied during molding is closer to the tension side than the neutral axis. The method for producing a fiber reinforced plastic according to claim 5 or 6, wherein the layer contains a cut prepreg. The incision prepreg is a length in which the angle formed by the incision direction of the incision and the orientation direction of the reinforcing fibers is within a range of 2 to 25 °, and the incision is projected in a direction perpendicular to the orientation direction of the reinforcing fibers. The manufacturing method of the fiber reinforced plastics in any one of Claims 5-7 whose is 30 micrometers-1.5 mm. The incision prepreg is intermittently inserted with a straight and substantially the same length, and the shortest distance between adjacent incisions is longer than the length of the incision. The manufacturing method of the fiber reinforced plastic of description.