Fiber-reinforced plastic and method for producing same

Abstract

In order to provide a fiber-reinforced plastic that has a protruding section and exhibits light weight and excellent mechanical properties and excellent quality in terms of appearance, a fiber-reinforced plastic is provided that is composed of a shape having, in at least one location, a plate-shaped section and a protruding section rising from the surface of at least one side of the plate-shaped section, wherein the interior of the plate-shaped section has at least one layer (a unidirectional layer) in which a large number of the reinforcing fibers are arranged in one direction within a matrix resin, the thickness t of the plate-shaped section is 0.3 mm to 1.8 mm, and the ratio w / t between the maximum width w of the protruding section and the thickness t of the plate-shaped section is 0.1 to 27.

Description

Fiber-reinforced plastic and its manufacturing method

[0001] The present invention relates to a fiber-reinforced plastic having a shape including a plate-like portion and a protrusion protruding from at least one side of the plate-like portion, and more specifically, to a fiber-reinforced plastic in which the plate-like portion and the protrusion are formed from a large number of reinforcing fibers and a matrix resin.

[0002] Fiber-reinforced plastics, which are made of reinforcing fibers and a matrix resin, are attracting attention as they are expected to be used in a wide range of fields, including industry, sports, medicine, and information and communications, due to their high specific strength, high specific modulus of elasticity, excellent mechanical properties, and high-performance properties such as weather resistance and chemical resistance.

[0003] Furthermore, in order to improve the mechanical properties of fiber-reinforced plastics or to promote thinner and lighter materials while maintaining their mechanical properties, the cross-sectional shape of the molded product has been devised, and fiber-reinforced plastics with varying thicknesses and rib shapes have been designed. Rib shapes in particular are effective in preventing warping on the large flat surfaces of molded products, but the complex shape poses challenges in terms of moldability and mass production.

[0004] Methods for producing fiber-reinforced plastics with high-performance properties include autoclave molding and press molding. In autoclave molding, semi-cured prepregs, consisting of continuous reinforcing fiber sheets or woven fabrics impregnated with a thermosetting resin as a matrix resin, are laminated and heated and pressurized in a high-temperature, high-pressure oven (autoclave) to harden the thermosetting matrix resin and form a fiber-reinforced plastic. In press molding, the laminated prepregs are placed in a mold and heated and pressurized in a press to harden the thermosetting matrix resin and form a molded product. Alternatively, prepregs impregnated with a thermoplastic resin as a matrix resin are used, and the thermoplastic resin is softened or melted and molded, followed by cooling and demolding. In particular, press molding using thermosetting resins has recently attracted attention as a highly productive molding method because it allows for the production of large quantities of molded products in a short period of time by using prepregs in which reinforcing fibers are impregnated with a thermosetting resin that has a fast curing rate as a matrix resin.

[0005] In the molding method using the prepreg described above, when producing molded products with complex shapes, such as shapes with varying thickness or shapes with ribs, one possible method is to divide the desired fiber-reinforced plastic into plate-like sections, ribbed sections, etc., mold each section separately, and then join them using adhesive or heat fusion. However, the bonding process is time-consuming and costly, and the strength and rigidity of the joints are lower than those of the other sections, so the joints tend to break first, making it difficult to fully utilize the excellent mechanical properties and durability of the fiber-reinforced plastic.

[0006] On the other hand, there is also a method in which the material is shaped in a mold before molding, a preform is made, and then molding is performed. Although this method solves the problem of breakage at the joints mentioned above, the shaping process takes time, which poses issues in terms of production efficiency and cost.

[0007] Furthermore, when using fiber-reinforced plastics to create various components, in addition to the moldability and mass production capabilities described above, high-quality appearance may be required. The unique appearances of fiber-reinforced plastics, such as hairline, washi paper, and woven patterns, are factors that enhance the added value of the product. However, in shapes with varying thickness or ribs, the flow of reinforcing fibers becomes intense during molding, disrupting the unique appearance described above, making it difficult to achieve high-quality appearance. While methods such as increasing the thickness of the molded product to reduce the impact of the flow of reinforcing fibers due to thickness variations or ribs, or attaching a separate layer with high-quality appearance to the design surface, are conceivable, improvements are desired in terms of lightness and production efficiency.

[0008] Attempts to improve such problems of the conventional technology have been proposed (Patent Documents 1 and 2).

[0009] Patent Document 1 proposes a method for manufacturing fiber-reinforced plastics in which at least two prepreg base materials, each having a fiber length adjusted to 10 to 100 mm by inserting slits, are laminated and press-molded to form a rib shape. While this method has been studied from the perspective of the rigidity and material balance of the molded product, its effect on appearance quality has not been studied, and it is intended for molding thick components, leaving issues with weight reduction.

[0010] Patent Document 2 shows that in a fiber-reinforced plastic composed of a laminate of woven fabric prepreg and discontinuous fiber prepreg, when the heat generation amount of the resin in each prepreg satisfies predetermined conditions, a fiber-reinforced plastic with little disorder in the weave can be obtained. This document also describes the appearance quality when ribs are molded, but does not describe the width of the rib or the thickness of the plate-shaped portion, and the reinforcing effect and light weight are not clear.

[0011] International Publication No. 2008 / 038429 International Publication No. 2019 / 031111

[0012] The present invention aims to provide a fiber-reinforced plastic having protrusions, which overcomes the problems of the prior art and is lightweight and has excellent mechanical properties and appearance quality.

[0013] The present invention achieves this object as follows: (1) A fiber-reinforced plastic having a shape including a plate-shaped portion and at least one protrusion protruding from at least one surface of the plate-shaped portion, wherein the plate-shaped portion has at least one layer (unidirectional layer) in which a large number of reinforcing fibers are unidirectionally arranged in a matrix resin, the thickness t of the plate-shaped portion being 0.3 mm or more and 1.8 mm or less, and the ratio w / t of the maximum width w of the protrusion to the thickness t of the plate-shaped portion being 0.1 or more and 27 or less. (2) The fiber-reinforced plastic according to (1) above, wherein the fiber volume fraction (Vf) of the fiber-reinforced plastic is 43% to 58%. (3) The fiber-reinforced plastic according to (1) or (2) above, wherein the ratio w / t of the maximum width w of the protrusion to the thickness t of the plate-shaped portion is 2 or more and 27 or less. (4) The fiber-reinforced plastic according to any one of (1) to (3), wherein the plate-like portion has two or more unidirectional layers therein, and the two unidirectional layers on the side where the protrusions are present have fiber orientation directions that are non-parallel and non-perpendicular to the length direction of the protrusions. (5) The fiber-reinforced plastic according to any one of (1) to (3), wherein the fiber weight of at least one layer of the unidirectional layers in the plate-like portion is 70 g / m ２ More than 100g / m ２(6) The fiber-reinforced plastic according to any one of (1) to (4), wherein the plate-shaped portion has a plurality of layers made of reinforcing fibers and a matrix resin, the protrusions are provided on only one surface of the plate-shaped portion, and the reinforcing fibers forming the outermost layer on the opposite surface are woven. (7) The fiber-reinforced plastic according to (6), wherein the mesh thickness of the woven fabric is 0.25 mm or less. (8) The fiber-reinforced plastic according to any one of (1) to (7), wherein the radius of curvature R of the curved surface formed by the protrusions and the plate-shaped portion is 2 mm or less. (9) The fiber-reinforced plastic according to any one of (1) to (8), wherein the maximum width w of the protrusions is 8 mm or less. (10) The fiber-reinforced plastic according to any one of (1) to (9), wherein the plate-shaped portion has two or more types of unidirectional layers with different fiber basis weights inside. (11) The fiber-reinforced plastic according to (10), wherein the outermost layer on the side of the plate-shaped portion where the protrusions are located is the unidirectional layer, and the fiber weight of the outermost unidirectional layer is smaller than the fiber weight of at least one other unidirectional layer in the plate-shaped portion. (12) The fiber-reinforced plastic according to any of (1) to (11), wherein the plate-shaped portion has a plurality of layers made of reinforcing fibers and a matrix resin, the protrusions are located on only one surface of the plate-shaped portion, and at least one layer other than the outermost layer on the surface where the protrusions are located is a layer (non-unidirectional layer) in which a large number of reinforcing fibers are oriented in at least two directions in the matrix resin. (13) The fiber-reinforced plastic according to any of (1) to (12), wherein the plate-shaped portion has a non-unidirectional layer, and the ratio w / t' of the maximum width w of the protrusions to the total thickness t' of the unidirectional layer located closer to the protrusions than the non-unidirectional layer is 0.1 or more and 27 or less. (14) The fiber-reinforced plastic according to any one of (1) to (13), wherein at least one of the unidirectional layers inside the plate-shaped portion contains reinforcing fibers having a fiber length of 10 to 300 mm. (15) A method for producing a fiber-reinforced plastic, comprising: placing at least one layer of a prepreg, in which a large number of reinforcing fibers arranged in one direction are impregnated with a matrix resin, in a mold; closing the mold; and applying heat and pressure to obtain the fiber-reinforced plastic according to any one of (1) to (14).(16) A golf club comprising the fiber reinforced plastic according to any one of (1) to (14).

[0014] According to the present invention, it is possible to provide a fiber reinforced plastic having protrusions, which is lightweight and has excellent mechanical properties and appearance quality.

[0015] 1 is a conceptual diagram showing an example of a protrusion and a plate-shaped portion that constitute a fiber reinforced plastic according to the present invention. FIG. 2 is an explanatory diagram showing the definitions of the fiber length, the length, angle, and projected length of a slit-inserted prepreg. FIG. 3 is an example of a cut pattern of a slit-inserted prepreg (an example having parallel, continuous slits). FIG. 4 is another example of a cut pattern of a slit-inserted prepreg (an example having parallel, intermittent slits). FIG. 5 is another example of a cut pattern of a slit-inserted prepreg (an example in which the angle with the reinforcing fibers is constant and approximately half of the slits are positive and half are negative). FIG. 6 is another example of a cut pattern of a slit-inserted prepreg (an example in which the shortest distance between adjacent slits is longer than the length of the slits). FIG. 7 is an example of a longitudinal cross-section of a fiber reinforced plastic having protrusions. FIG. 8 is a schematic diagram showing distortion on the surface of the fiber reinforced plastic (the surface opposite to the surface having protrusions). FIG. 9 is another example of a longitudinal cross-section of a fiber reinforced plastic having protrusions (an example in which the outermost layer on the surface opposite to the side having protrusions is a non-unidirectional layer). 1 is a schematic diagram showing an example of the shape of a protrusion protruding from a plate-shaped portion, a conceptual diagram showing the protrusion constituting a fiber-reinforced plastic and the orientation direction of reinforcing fibers in the plate-shaped portion, and another example of a longitudinal cross-sectional view of a fiber-reinforced plastic having a protrusion.

[0016] The fiber-reinforced plastic of the present invention has at least one layer in which a large number of reinforcing fibers are arranged in one direction in a matrix resin (hereinafter, sometimes referred to as a unidirectional layer), and as shown in Fig. 1, for example, is a fiber-reinforced plastic having a shape including a plate-like portion 100 and at least one protrusion 200 protruding from at least one surface of the plate-like portion 100. As described above, the plate-like portion 100 contains at least one unidirectional layer.

[0017] Here, the shape of the protrusion when viewed from above the surface of the plate-like portion is referred to as the planar shape of the protrusion, the direction in which the planar shape of the protrusion extends is referred to as the extension direction of the protrusion (hereinafter sometimes referred to as the length direction), and the direction perpendicular to the length direction in the planar shape is referred to as the width direction of the protrusion. Here, the extension direction of the planar shape refers to the long axis direction if the planar shape is elliptical, the direction of the long side if the planar shape is rectangular, and if the planar shape is any other shape, the direction of the long side of the rectangle with the smallest circumscribing area of ​​the shape. Furthermore, a cross section of the protrusion that is parallel to the length direction of the protrusion and perpendicular to the planar direction of the plate-like portion, so that the length direction of the protrusion is maximized, is referred to as the transverse cross section of the protrusion, and a cross section of the protrusion that is parallel to the width direction of the protrusion and perpendicular to the planar direction of the plate-like portion, so that the width direction of the protrusion is maximized, is referred to as the longitudinal cross section of the protrusion. As an example, when the planar shape of the protrusion is an ellipse as shown in Figure 1, the long axis direction of the ellipse is the length direction 20 of the protrusion, the short axis direction is the width direction 21 of the protrusion, the cross section perpendicular to the planar direction of the plate-like portion along the long axis is the transverse cross section 22 of the protrusion, and the cross section perpendicular to the planar direction of the plate-like portion along the short axis is the longitudinal cross section 23 of the protrusion.

[0018] Furthermore, when a protrusion extends in two different directions, for example, when the planar shape can be defined by a combination of rectangles or ellipses (such as an X-shape, V-shape, H-shape, or Y-shape), the protrusion is interpreted as having multiple length directions. That is, when the planar shape of the protrusion is X-shaped or V-shaped, it is interpreted as having two length directions, and when it is H-shaped or Y-shaped, it is interpreted as having three length directions, and accordingly, the planar shape is decomposed into multiple shapes and interpreted as having multiple transverse and longitudinal cross sections corresponding to the respective directions.

[0019] Figure 7 shows a longitudinal cross section of a protrusion protruding from a plate-like portion. The width of the protrusion 200 may be different at the tip and base as shown in Figure 7, or may be the same. However, it is preferable that the width at the base is wider than the tip, as this makes it easier to remove from the mold when demolding and also alleviates stress concentration when a load is applied during use. Furthermore, when the shape of the tip and base of the protrusion is different as shown in Figure 7, the shape at the base is taken as the planar shape of the protrusion.

[0020] The protrusion 200 and the plate-like portion 100 are preferably connected by a curved surface, with a curvature radius R of preferably 2 mm or less, more preferably 1 mm or less. A curvature radius R of 2 mm or less prevents the volume at the base of the protrusion from becoming excessively large, allowing the protrusion to be sufficiently filled with the unidirectional prepreg described below. This reduces the likelihood of a "resin-rich" surface, which reduces the deterioration of appearance quality due to dents on the design surface (or the surface opposite the surface where the protrusion exists, if only one surface is present). If the curvature radius R is too small, the boundary between the protrusion 200 and the plate-like portion 100 (hereinafter referred to as the joint or contact point) becomes sharp, which can cause the reinforcing fibers to come into contact and be cut, or can make mold processing difficult. Therefore, a curvature radius of approximately 0.2 mm is preferred.

[0021] In the present invention, the maximum width of the protrusion in a longitudinal cross section is defined as the maximum width w of the protrusion. That is, in the case of a shape such as that shown in FIG. 7 , the distance 202 between both ends of the contact point between the plate-like portion 100 and the protrusion 200 is defined as the maximum width w of the protrusion. Furthermore, when the plate-like portion and the protrusion are connected by a curved surface, the maximum width refers to the distance including the curved surface. The maximum width of the protrusion is preferably 8 mm or less, and more preferably 5 mm or less. When the maximum width of the protrusion is 8 mm or less throughout the entire protrusion, a fiber-reinforced plastic with high appearance quality can be obtained even if the plate-like portion is thin, for example, 1.8 mm or less, thereby achieving a thinner and lighter material. Furthermore, when the protrusion extends in two different directions and has multiple longitudinal cross sections as described above, the maximum width in the longitudinal cross section with the largest maximum width is defined as the maximum width of the protrusion.

[0022] The shape of the plate-like portion 100 is not particularly limited, but the thickness 101 of the plate-like portion is in the range of 0.3 to 1.8 mm, and this thickness can be designed as desired by adjusting the amount of fiber and matrix resin used. Methods for adjusting the amount of fiber and matrix resin used include adjusting the number of layers of the fiber base material that constitutes the plate-like portion, changing the amount of matrix resin, or changing the type of fiber.

[0023] When the fiber-reinforced plastic of the present invention is used in structural members, outer panels such as covers, and other parts used in transportation equipment such as automobiles and motorcycles, sports equipment such as bicycles and golf clubs, medical equipment, etc., the thickness t of the plate-like portion is 0.3 to 1.8 mm from the viewpoint of both the required mechanical properties and light weight, and practicality. Furthermore, when rigidity and light weight are particularly required for the plate-like portion, a thickness of 0.5 to 1.2 mm is preferable. In particular, when the fiber-reinforced plastic is used in components that require strict light weight, such as golf club heads, the weight distribution design has a significant impact on the flight distance and hitting feel, and therefore design to the nearest 0.1 g may be required. For example, when the fiber basis weight is 100 g / m ２ In the case of a molded product made of a 100 mm x 100 mm prepreg with a resin mass fraction (Rc) of 40%, a difference of 0.1 mm in the thickness of the plate-shaped portion results in a change in weight of approximately 1 to 2 g, so adjusting the thickness of the plate-shaped portion, which has a significant impact on weight, is extremely important. If the thickness of the plate-shaped portion exceeds 1.8 mm, it is difficult to apply it to components that require weight reduction. In this invention, the thickness of the plate-shaped portion refers to the thickness 101 of the plate-shaped portion at the junction of the plate-shaped portion 100 and the protrusion 200 in the longitudinal cross section (if the plate-shaped portion and the protrusion are connected by a curved surface, the junction of the curved surface and the plate-shaped portion).

[0024] In the present invention, the ratio w / t, the ratio of the maximum width w [mm] of the protrusion to the thickness t [mm] of the plate-shaped portion, is 0.1 or more and 27 or less. The upper limit is preferably 10 or less, and more preferably 5 or less. If w / t exceeds 27, the reinforcing fibers filling the protrusions may be insufficient, resulting in dents on the design surface. Furthermore, resin-rich areas at the base of the protrusions may facilitate the flow of the reinforcing fibers on the design surface, leading to a deterioration in appearance quality due to twisted reinforcing fibers (weave distortion). Figure 8 shows a schematic diagram of the design surface. (A) shows a state in which the reinforcing fibers 401 are aligned in one direction and have no weave distortion, while (B) shows a state in which weave distortion 402 is present. The greater the degree of weave distortion, the worse the appearance quality. From the perspective of appearance quality, the smaller the w / t, the better. However, below a certain point, the effect of appearance quality saturates, and conversely, the reinforcing effect of the protrusions decreases. Therefore, from the viewpoints of appearance quality, the ability to fill the protrusions with reinforcing fibers, and the strength of the protrusions, a w / t ratio of 0.1 or more is preferable, more preferably 2 or more, and even more preferably 3 or more. When w / t is 2 or more, it is possible to further expect that both good appearance quality and improved strength of the molded product will be achieved. Also, for example, if the thickness 101 of the plate-like portion in Figure 7 is different on the left and right sides of the protrusion, the smaller thickness of the plate-like portion will be taken as the thickness t of the plate-like portion.

[0025] In order to obtain a fiber reinforced plastic with high appearance quality, it is preferable that the ratio of the length corresponding to the width of the protrusion to the length corresponding to the thickness of the plate-like portion is 27 or less not only in the longitudinal section based on the above definition but also in all cross sections parallel to the longitudinal section and including the protrusion. However, if there are circumstances where, for example, appearance quality is not required in some sections and it is desired to provide wider protrusions, it is possible to intentionally provide a portion of the cross section other than the longitudinal section where the above ratio exceeds 27.

[0026] The maximum width of the protrusion and the thickness of the plate-like portion can be measured by measuring the distance between both ends of the joint between the protrusion and the plate-like portion with a vernier caliper or a micrometer, or by observing the cross section with a microscope and calculating the width by image analysis.

[0027] The height 203 of the protrusions of the fiber-reinforced plastic of the present invention is not particularly limited and can be designed as desired, but is preferably 0.1 to 50 mm, more preferably 0.1 to 20 mm, and even more preferably 1 to 10 mm. If the thickness 101 of the plate-like portion differs between the left and right sides of the protrusion, the height of the protrusion is determined based on the thickness of the plate-like portion with the smaller thickness. If the height of the protrusion exceeds 50 mm, there is a possibility that unfilled portions will occur where the unidirectional prepreg described below does not fill all the way to the tip of the protrusion. If the height is less than 0.1 mm, the reinforcing effect will be reduced, potentially obscuring the significance of providing the protrusions.

[0028] Furthermore, when the height of the protrusion is 1 to 6 mm, the amount of fiber base material constituting the plate-shaped portion that flows into the grooves in the mold for forming the protrusion does not become too large, and this is most preferable because it is possible to more reliably prevent the occurrence of disturbances in the fiber orientation and surface depressions on the design surface of the fiber-reinforced plastic.

[0029] In the fiber-reinforced plastic of the present invention, it is preferable that at least one layer other than the outermost layer on the surface of the plate-shaped portion 100 having the protrusions is a non-unidirectional layer 102. Furthermore, as shown in Figure 9, it is preferable that the outermost layer on the side opposite to the surface of the plate-shaped portion 100 having the protrusions is a non-unidirectional layer 102.

[0030] Here, the term "non-unidirectional layer" refers to a layer in which the reinforcing fibers are not oriented in only one direction, i.e., a layer in which the fibers are oriented in at least two directions. More specific examples of the non-unidirectional layer include those in which the fibers are oriented in at least two or more predetermined directions, such as woven fabrics, and those in which the fibers are oriented randomly, such as nonwoven fabrics, but are not particularly limited thereto. In the present invention, the term "non-unidirectional layer" refers to one of the layers constituting the plate-shaped portion of a fiber-reinforced plastic, and a material corresponding to the non-unidirectional layer before molding the fiber-reinforced plastic is referred to as a "non-unidirectional reinforcing fiber sheet." As described above, the non-unidirectional reinforcing fiber sheet may be in any form as long as the reinforcing fibers are oriented in multiple directions, rather than in only one direction. It may be a dry sheet containing no matrix resin, or may be one in which at least a portion of the sheet is pre-impregnated with matrix resin.

[0031] As shown in FIG. 9 , when the plate-shaped portion has a non-unidirectional layer 102, the ratio w / t′ of the maximum width w [mm] of the protrusion to the total thickness t′ [mm] of the unidirectional layer is preferably 0.1 or more and 27 or less. The upper limit is more preferably 10 or less, and most preferably 5 or less. If w / t′ exceeds 27, the reinforcing fiber sheet filling the protrusion may be insufficient, resulting in dents on the design surface, or resin may be enriched at the base of the protrusion, which may cause the reinforcing fibers on the design surface to flow more easily, resulting in misalignment of the fiber direction and a decrease in appearance quality. From the perspective of appearance quality, the smaller w / t′ is better, but from the perspective of the filling of the reinforcing fibers into the protrusion and the strength of the protrusion, a ratio of 0.1 or more is preferred, more preferably 2 or more, and even more preferably 3 or more. Furthermore, for example, if the total thickness 103 of the unidirectional layers in FIG. 9 is different on the left and right sides of the protrusion, the smaller total thickness is taken as the total thickness t′.

[0032] The shape of the protrusions protruding from the plate-like portion is not particularly limited, and various shapes can be adopted depending on the purpose. For example, in addition to the elliptical protrusions shown in FIG. 1 when viewed from the top surface of the plate-like portion, examples of protrusions include polygonal (e.g., rectangular), circular, X-shaped, V-shaped, H-shaped, I-shaped, Y-shaped, and L-shaped protrusions. These shapes may also be combined. Note that FIG. 10(A) shows an embodiment having an X-shaped protrusion, FIG. 10(B) shows an I-shaped protrusion, and FIG. 10(C) shows an embodiment having a plurality of I-shaped protrusions.

[0033] The cross-sectional shape and longitudinal cross-sectional shape of the protrusion may be, for example, polygonal (for example, rectangular or triangular), semicircular, or the like.

[0034] The cross-sectional shape and height dimensions of the protrusions can be the same for all of the multiple protrusions, but they can also be changed to match the uneven shape and curvature of the fiber-reinforced plastic, and it is also possible to create parts that do not have the above shapes.

[0035] In the fiber-reinforced plastic of the present invention, the protrusions can be arranged at any position on the plate-shaped portion. Furthermore, the arrangement positions of the protrusions can be confirmed when viewed from above the fiber-reinforced plastic, where the appearance of the protrusions can be seen in their entirety. The arrangement positions of the protrusions are not limited to one position, but can be arranged in two or more positions. In other words, protrusions of the same shape or different shapes can be installed in two or more positions.

[0036] The number of protrusions is counted by determining that the parts where the plate-like parts are visible when viewed from above do not constitute protrusions, and by recognizing the smallest protrusion surrounded by the plate-like parts as one independent protrusion.

[0037] When ribs are provided as protrusions, in order to achieve both weight reduction and increased rigidity of the fiber-reinforced plastic according to the present invention, it is preferable to arrange the ribs not only in one location but in two or more locations. This allows the reinforcement range of the plate-shaped portion to be expanded. Furthermore, when ribs are arranged in two or more locations, the reinforcing effect can be obtained by arranging the length directions of the ribs in a parallel relationship to each other. In this case, each rib may be arranged discontinuously or intermittently. On the other hand, even if the length directions of the multiple ribs are not parallel to each other (e.g., in a V-shape), the length directions can be arranged in any direction according to the mechanical properties required of the fiber-reinforced plastic.

[0038] The shape of the ribs can be designed arbitrarily depending on the mechanical properties required of the fiber-reinforced plastic, including not only a straight line shape in only one longitudinal direction, but also a cross shape (X-shape) or V-shape (including a shape in which multiple crosses are connected) in which ribs in at least two directions intersect at any location and angle, and even a shape in which at least three ribs intersect radially at one location at any angle.

[0039] The fiber-reinforced plastic of the present invention is characterized in that the interior of the plate-shaped portion has at least one layer (unidirectional layer) in which a large number of reinforcing fibers are arranged in one direction in a matrix resin. Here, the "interior of the plate-shaped portion" may be a portion corresponding to the plate-shaped portion, and may be a portion constituting a surface layer or any other inner layer portion. In the present invention, the material corresponding to the unidirectional layer before molding the fiber-reinforced plastic is referred to as a unidirectional prepreg.

[0040] In the fiber-reinforced plastic of the present invention, for example, when preparing a preform that serves as its precursor, it is preferable to arrange at least one layer of unidirectional prepreg so that the fiber orientation direction is not parallel or perpendicular to the length direction of the protrusion. Here, "not parallel or perpendicular" refers to a non-parallel and non-perpendicular state, meaning that it may be oblique to the width direction of the cross section of the protrusion. That is, for example, Figures 11(A) to 11(C) show an embodiment in which the reinforcing fibers constituting the unidirectional prepreg extend in the length direction of the protrusion (rib direction, depth direction in the paper) or in a direction perpendicular thereto. However, instead of adopting such an embodiment, it means that the reinforcing fibers do not extend in the longest direction of the protrusion or in a direction perpendicular thereto, as shown in Figure 11(D). 11(A) shows a state in which the reinforcing fiber 300 is parallel to the length direction (rib direction) of the protrusion 200, Fig. 11(B) shows a state in which the reinforcing fiber 300 is perpendicular to the length direction (rib direction) of the protrusion 200, and Fig. 11(C) shows a state in which the reinforcing fiber 300 is parallel and perpendicular to the length direction (rib direction) of the protrusion 200. On the other hand, Fig. 11(D) shows a state in which the reinforcing fiber 300 is neither parallel nor perpendicular to the length direction (rib direction) of the protrusion 200 (i.e., is non-parallel and non-perpendicular), and therefore the cross section of the reinforcing fiber 300 is flattened.

[0041] In the final fiber-reinforced plastic, the presence of at least one layer formed by arranging unidirectional prepregs so that the orientation direction of the reinforcing fibers is neither parallel nor perpendicular to the length direction of the protrusion means that the amount of reinforcing fibers extending along the longest direction of the protrusion is reduced. Therefore, it is possible to suppress the occurrence of depressions 500 that occur along the fiber alignment direction in the protrusion of the fiber-reinforced plastic as shown in Figure 11(A) and the occurrence of "unfilled" areas of fiber or resin, or so-called "resin-rich" areas, as shown in Figures 11(B) and (C), while also improving the appearance quality.

[0042] If the fiber orientation direction is parallel to the length of the protrusion, the protrusion will be less able to withstand shear loads. This results in insufficient strength of the protrusion, which can lead to cracks forming inside the protrusion along the fiber orientation direction, causing the protrusion to break and peel off from the plate-like portion. Furthermore, if the fiber orientation direction is perpendicular to the length of the protrusion, the reinforcing fibers will have difficulty flowing into the protrusion (the recessed portion of the mold) during molding, which can result in areas of the protrusion that are not filled with reinforcing fibers after molding. Furthermore, if the reinforcing fibers have difficulty flowing, the matrix resin may be squeezed out of the unidirectional prepreg, resulting in areas of resin only (resin-rich).

[0043] Furthermore, when the protrusions extend in two different directions as described above, it is preferable that the fiber orientation direction of at least one layer formed by arranging unidirectional prepregs is not parallel or perpendicular to the length direction of at least one of the protrusions.

[0044] The angle between the fiber orientation direction and the length direction of the protrusions (the angle formed between the orientation direction of the reinforcing fibers and the length direction of the protrusions) is not particularly limited as long as it is neither parallel nor perpendicular within the range of 0 to 90°, but is preferably 5 to 85°. Furthermore, from the viewpoint of the filling property into the protrusions and the bonding strength between the protrusions and the plate-like portion, it is more preferably 30 to 60°.

[0045] When forming a plate-like part by laminating two or more layers of unidirectional prepregs, it is preferable to laminate them so that as many layers as possible have fiber orientation directions that are neither parallel nor perpendicular to the longitudinal direction of the protrusions. In this case, the angle difference between the fiber orientation directions between layers is not particularly limited, and all layers may be aligned in the same direction or different directions. This can be freely selected depending on the desired composite properties. However, having layers whose fiber orientation directions are not parallel to each other is preferable because it has advantages such as the protrusions being able to withstand loads from multiple directions and reducing warpage of the molded product (fiber-reinforced plastic).

[0046] When laminating multiple unidirectional prepregs with different reinforcing fiber orientation directions, generally [0 / 90]n Ｓ Symmetric stacking such as [0 / ±60]n Ｓ , [+45 / 0 / -45 / 90]n Ｓ Such an isotropic lamination and a symmetrical lamination structure in the lamination direction (thickness direction) are considered effective in reducing warpage of the plate-shaped portion of the fiber-reinforced plastic. On the other hand, in the fiber-reinforced plastic of the present invention, warpage can be reduced by forming the protrusions in a rib shape, and therefore it is possible to bias the orientation direction of the fibers in the direction of rigidity required for the fiber-reinforced plastic.

[0047] Furthermore, the lamination order of the unidirectional prepregs can be set arbitrarily, but from the viewpoint of moldability, it is preferable to laminate the layers so that the layer whose fiber orientation direction is neither parallel nor perpendicular to the length direction of the protrusions is positioned close to the protrusions. Preferably, in the plate-shaped part, the unidirectional prepreg is arranged within the fourth layer from the side where the protrusions are located, and most preferably, the unidirectional prepreg is arranged in the outermost layer on the side where the protrusions are located. It is also preferable that the top two layers on the side where the protrusions are located, and even all of the top four layers, are layers whose fiber orientation direction is neither parallel nor perpendicular to the length direction of the protrusions.

[0048] Furthermore, the number of unidirectional prepreg layers can be increased depending on the properties required for the fiber-reinforced plastic. The more unidirectional prepreg layers there are, the more fibers will flow to the protrusions, which is more preferable. Four or more layers are preferable, and six or more layers are more preferable. By stacking in this manner, the reinforcing fibers can easily flow to the protrusions, making it possible to easily fill the ends of the protrusions with reinforcing fibers, which is preferable from the viewpoints of moldability and the mechanical properties of the protrusions.

[0049] Furthermore, when there are two or more protrusions, the filling ability of the prepreg for each protrusion may differ, and it is conceivable that some protrusions may be left "unfilled." In such cases, it is preferable to laminate the unidirectional prepregs so that the fiber orientation direction of the unidirectional prepreg is neither parallel nor perpendicular to the length direction of the protrusions, which are considered to be more difficult to fill. To cite an example of a protrusion that is difficult to fill, the longer the protrusion, the more difficult it is to fill with the prepreg. Therefore, it is preferable that the fiber orientation direction of the unidirectional prepreg is neither parallel nor perpendicular to the length direction of at least the longest protrusion. More preferably, it is preferable that the fiber orientation direction of the unidirectional prepreg is neither parallel nor perpendicular to the length direction of all protrusions. The same applies when the protrusions extend in two different directions as described above.

[0050] In the present invention, it is preferable that the fiber length of at least a portion of the reinforcing fibers be 10 to 300 mm. By setting the fiber length within this range, the reinforcing fibers can easily conform to the shape of the protrusions of the molded article, improving the ability to form into three-dimensional shapes. In addition, since the disorder of the fiber arrangement during shaping and molding is reduced, a fiber-reinforced plastic with small variation in mechanical properties and high surface smoothness can be obtained.

[0051] Specifically, by setting the fiber length to 300 mm or less, the flexibility and fluidity of the reinforcing fibers are improved, and excellent shaping and moldability can be obtained. On the other hand, if the fiber length is 10 mm or more, the distance between the incisions is increased, making it difficult for cracks that occur when a high load is applied to the fiber-reinforced plastic to link, resulting in a fiber-reinforced plastic with high mechanical properties and durability.

[0052] When adjusting the fiber length by cutting the reinforcing fibers with a blade, the reinforcing fibers may move when the blade hits them, and some fibers may escape from the blade or become entangled in the blade, so it is possible that some fibers may have lengths outside the above range, but sufficient improvement effects can be expected by adjusting the fiber lengths of the majority of reinforcing fibers to fall within the above range. Also, some fibers may be cut by hitting the edge of the mold during molding, so fibers shorter than the above range may be present inside the molded product.

[0053] The fiber lengths of all reinforcing fibers in the fiber-reinforced plastic may be adjusted to fall within the range described above, but sufficient effects can be obtained by adjusting only the fiber lengths of the reinforcing fibers in and around parts where the shape of the fiber-reinforced plastic changes, such as protrusions.

[0054] The unidirectional prepreg used in the present invention, in which reinforcing fibers having a fiber length of 10 to 300 mm are arranged in one direction, may be, for example, (1) a reinforcing fiber sheet obtained by forming discontinuous reinforcing fibers obtained by a spinning method such as stretch-break spinning into a sheet and impregnating the sheet with a matrix resin, (2) a reinforcing fiber sheet obtained by forming discontinuous reinforcing fibers (for example, chopped fibers) into a sheet and impregnating the sheet with a matrix resin, or (3) a unidirectional prepreg made of continuous reinforcing fibers, in which continuous or intermittent slits of a finite length are made across the entire surface of the unidirectional prepreg in a direction transverse to the reinforcing fibers, as shown in, for example, FIGS. 2 to 6 (slit-inserted prepreg).

[0055] (1) Draft-break spinning is a spinning method in which tension is applied to continuous fibers in a strand state to cut the fibers into short fibers. The cut ends of the short fibers are not concentrated in one place but are evenly distributed along the entire length of the strand. The cut ends of the reinforcing fibers are randomly arranged so as not to align with each other in single fiber units, forming an aggregate. Because the reinforcing fibers flow in single fiber units, moldability is slightly inferior, but stress transmission is very efficient, allowing for the development of extremely high mechanical properties. Furthermore, because the cut points of the reinforcing fibers are dispersed, excellent quality stability can be achieved.

[0056] The method (2) of arranging discontinuous reinforcing fibers (e.g., chopped fibers) in one direction to form a sheet involves aligning the cut ends of the reinforcing fibers in units of multiple fibers and arranging them in a somewhat regular pattern to form an aggregate. This inevitably results in unevenness in the arrangement and distribution of the reinforcing fibers, which results in slightly lower quality stability, but because the fibers flow in units of multiple fibers, it allows for extremely excellent moldability.

[0057] The method (3) using a cut-insertion prepreg has excellent quality stability and mechanical properties because the reinforcing fibers are regularly arranged, and also has excellent moldability because the prepreg flows in units of multiple fibers.

[0058] The above three embodiments (1), (2), and (3) can be selected appropriately depending on the application. All of them have an excellent balance between mechanical properties and moldability and can be easily manufactured. Among them, the most preferred embodiment is (3), in which continuous or intermittent incisions of finite length are made across the entire surface of a unidirectional prepreg made of continuous reinforcing fibers.

[0059] The method of making incisions in the prepreg is not particularly limited. For example, it is possible to make incisions manually using a cutter, but a method of mechanically making incisions using an automatic cutting machine or the like, which has stable quality and is capable of mass production, is preferred. The method of mechanically making incisions is not particularly limited. For example, there are methods such as inserting incisions at predetermined positions using a cutting machine whose blade moves over a prepreg base material spread on a table, or inserting incisions corresponding to the pulse period by rolling a rotating circular blade of a perforation in a straight line or scanning a pulse laser for laser processing in a straight line at high speed. Both are highly productive incision insertion methods, and can be selected depending on the production equipment owned.

[0060] The prepreg that has undergone this process has multiple intermittent cuts made across at least some of the reinforcing fibers, resulting in at least some of the reinforcing fibers having a fiber length of 10 to 300 mm. The intermittent cuts essentially separate all of the reinforcing fibers, ensuring shapability and fiber flowability during molding.

[0061] The length of the incision, defined as the projected length Ws projected onto a plane perpendicular to the reinforcing fibers in the plane of the prepreg base material, is preferably within the range of 30 μm to 1.5 mm. However, since the base material deforms during shaping and molding, the incision may be longer where the base material stretches and shorter where the base material is crushed by compression. Therefore, when observing the fiber-reinforced plastic after molding, there are some areas where the incision length is not within the above range, but the fiber-reinforced plastic ultimately has a structure in which reinforcing fibers with fiber lengths of 10 to 300 mm are regularly arranged, allowing for the production of molded products with excellent mechanical properties and surface appearance.

[0062] By reducing Ws, the amount of reinforcing fiber broken by each incision is reduced, and strength is expected to improve. In particular, by setting Ws to 1.5 mm or less, a significant improvement in strength is expected. On the other hand, if Ws is less than 30 μm, it is difficult to control the incision position, the fiber length of the reinforcing fiber varies greatly, and the number of reinforcing fibers outside the specified range increases, which may result in reduced formability and fluidity.

[0063] Here, the "projected length Ws projected onto a projection plane perpendicular to the reinforcing fibers" refers to the length of the incision when projected perpendicular to the projection plane (fiber orientation direction 5) on the assumption that the projection plane exists in a direction perpendicular to the orientation direction of the reinforcing fibers (fiber perpendicular direction 6) within the plane of the incision-inserted prepreg, as shown in Figures 2, 4, 5, and 6.

[0064] When the angle between the incision in the prepreg base material and the reinforcing fiber is θ, the absolute value of θ is preferably within the range of 2 to 25°. When the absolute value of θ is 25° or less, the mechanical properties, especially the tensile strength, can be improved. From this viewpoint, it is more preferable that the absolute value of θ is 15° or less. On the other hand, if the absolute value of θ is less than 2°, it may be difficult to make the incision stably. In other words, if the incision is tilted relative to the reinforcing fiber, the reinforcing fiber will easily escape from the blade when making the incision, reducing the positional accuracy of the incision. From this viewpoint, it is more preferable that the absolute value of θ is 5° or more.

[0065] As a method for inserting the incisions, either a method of inserting them continuously at the above angle, as shown in Figure 3, or a method of inserting incisions intermittently at multiple locations, as shown in Figures 4 and 5, can be used. In the case of continuous incisions, the fiber length can be controlled to a constant value, reducing variations in mechanical properties and three-dimensional shape conformity. On the other hand, when inserting incisions intermittently, the incision angle is oblique to the reinforcing fibers, so that the projected length Ws projected onto a projection plane perpendicular to the reinforcing fibers in the plane of the prepreg base material can be reduced relative to the actual incision length Y. Therefore, extremely small incisions, for example, Ws = 1.5 mm or less, can be made industrially and stably. Furthermore, the prepreg is less likely to come apart during lamination than with continuous incisions, and is therefore easier to handle as a prepreg.

[0066] A preferred cut pattern for the incision-inserted prepreg is one in which multiple intermittent diagonal incisions 9 are made in at least a portion of the prepreg base material in a direction transverse to the reinforcing fibers, as shown in Figure 4. The multiple intermittent diagonal incisions 9 are inserted linearly to form rows 11, and preferably these rows 11 are arranged in parallel to one another. This maximizes the distance between adjacent incisions while maintaining a constant length of the reinforcing fibers, thereby homogenizing the fiber-reinforced plastic and increasing its strength. The distance X between the rows is preferably within the range of 1 to 5 mm, for example.

[0067] Another preferred cut pattern for the incision-inserted prepreg is shown in Figure 5. In this embodiment, at least a portion of the prepreg base material has a plurality of intermittent diagonal incisions 9 cut in a direction transverse to the reinforcing fibers, and diagonal incisions 10 are cut in such a way that the absolute value of θ is substantially the same (uniform) as the diagonal incisions 9 but at opposite positive and negative angles. Approximately half of the diagonal incisions 9, 10 are cut. Here, the absolute value of θ is defined as "substantially the same" when the angle is within ±1°. Furthermore, "approximately half" means that, when expressed as a percentage based on the total number of diagonal incisions 9, 10, each is 45 to 55% (the same applies below).

[0068] Furthermore, as shown in Figure 5, when focusing on any one incision A, it is preferable that there are four or more incisions C with different θ values ​​that are closer to incision A than the nearest incision B, which has the same θ value. When the prepreg incision insertion portion conforms to a three-dimensional shape, the movement of the fiber end is determined by the relationship between the incision angle and the fiber direction. Therefore, by having adjacent incisions with the same shape but opposite angles, in-plane isotropy after molding is ensured from a macroscopic perspective.

[0069] When laminating prepregs with slits, if the diagonal slits are present in only one direction, the slit direction will be different depending on whether the prepreg is viewed from the front or back, even if the prepregs have the same fiber direction. Therefore, during fiber-reinforced plastic manufacturing, it may be necessary to control the slit direction so that it is the same each time, or to control the lamination procedure to laminate the same number of prepregs with the same fiber direction but different slit directions. However, if the absolute value of the slit inclination from the fiber direction is the same and the cut pattern is such that approximately half of the slits are at a positive angle and half are at a negative angle, lamination can be handled in the same way as with regular continuous fiber prepregs.

[0070] Furthermore, a preferred embodiment of the slit-inserted prepreg is the one shown in Figure 6. In this embodiment, at least a portion of the slit-inserted prepreg has a plurality of intermittent diagonal incisions 10 formed in a direction transverse to the reinforcing fibers. The intermittent diagonal incisions 10 are linear and have substantially the same length Y, and the shortest distance between adjacent incisions is longer than the length Y of the incision. Here, "substantially the same length" means a difference of ±5% (the same applies below). From the perspective of mechanical properties, fiber-reinforced plastics break when incisions, which are discontinuous points in the fibers, are connected by cracks. By using a cut pattern that separates incisions in a plane, crack connection is suppressed at least within the same plane, improving strength.

[0071] Furthermore, a preferred embodiment of the incision-inserted prepreg is one in which at least a portion of the incision-inserted prepreg has a plurality of intermittent incisions in a direction transverse to the reinforcing fibers, the intermittent incisions are inserted linearly and with substantially the same length Y, and the distance between adjacent incisions on the same line is greater than three times the incision length Y. When incisions are present on the same line, damage caused by the incisions may occur on the extension line of the incisions, and the closer the distance between the incisions, the more likely cracks are to link together. Therefore, by increasing the distance between incisions on the same line as much as possible, crack linkage is suppressed and strength is improved. Furthermore, when intermittent incisions are inserted on the same line and the incisions are close to each other, the incisions are easily recognized as an intermittent linear pattern after molding, while when the incisions are far apart, they are not recognized as a pattern, resulting in excellent surface quality. In addition, the existence of incisions on the same line means that the angle between the line extending one incision and the line connecting the closest points of the incision and the target incision is within 2°.

[0072] Furthermore, while all unidirectional prepregs may have fiber lengths adjusted within the aforementioned range, it is not necessary to arrange reinforcing fibers of such fiber lengths in all layers. In at least one of the unidirectional layers constituting the fiber-reinforced plastic plate-like portion, the fiber length of at least some of the reinforcing fibers needs to be 10 to 300 mm. The layer in which the unidirectional prepregs with adjusted fiber lengths are arranged can be appropriately selected depending on the width, height, curvature, and angle of the protrusions of the fiber-reinforced plastic. That is, for example, sufficient effects can be obtained by adjusting only the fiber lengths of the reinforcing fibers in the protrusions of the fiber-reinforced plastic and in the layer of the plate-like portion directly below the protrusions.

[0073] The fiber weight (FAW) of at least the plate-shaped portion of the fiber reinforced plastic of the present invention is, for example, 50 to 1,000 g / m ２ However, from the viewpoint of deformation resistance and fluidity, it is preferably 50 to 200 g / m ２ and more preferably 70 to 200 g / m ２ , most preferably 70 to 100 g / m ２The fiber weight of the plate-shaped portion can be controlled mainly by adjusting the fiber weight of the unidirectional prepreg that constitutes it, but when the plate-shaped portion is composed of two or more layers, it is preferable that at least one of the layers has a fiber weight in the above range.

[0074] The higher the fiber weight (FAW), the higher the rigidity of the fiber layer. ２ If the fiber weight (FAW) exceeds 50 g / m, the deformation resistance increases, and the fibers have difficulty flowing into the inside of the protrusion (mold recess), which may result in "unfilled" or "resin-rich" structures. Furthermore, when cutting the fibers of a high-basis-weight prepreg base material with a blade, the number of fibers escaping from the blade increases, and fibers with fiber lengths outside the target range increase, resulting in a prepreg base material with low fluidity. Therefore, from the viewpoint of moldability, it is preferable to stack a large number of low-basis-weight prepreg base materials. On the other hand, if the fiber weight (FAW) is 50 g / m, ２ If the thickness is less than 70 g / m, the cost will increase due to an increase in the number of steps required for producing the prepreg base material and laminating. ２ The above is more preferable.

[0075] The outermost layer on the protrusion side has a fiber basis weight of 70 g / m ２ More than 100g / m ２ It is more preferable to arrange the following unidirectional prepreg (unidirectional layer): When the unidirectional prepreg with the relevant fiber basis weight is in the outermost layer on the protrusion side, the reinforcing fibers can easily follow the shape of the grooves that form the protrusions of the mold, and excess resin ("resin-rich") areas are less likely to occur near the tips of the protrusions.

[0076] When two or more layers of unidirectional prepregs are laminated, it is also preferable to use unidirectional prepregs with two or more different fiber basis weights. In other words, it is also preferable to have two or more types of unidirectional layers with different fiber basis weights inside the plate-shaped part. In this case, the layers may be laminated in any order, but for example, it is preferable to arrange a unidirectional prepreg with a lower fiber basis weight than at least one other unidirectional layer in the plate-shaped part as the outermost layer on the side where the protrusion is located. More specifically, a unidirectional prepreg with a high fiber basis weight that is less likely to flow is arranged on the design surface side, and a unidirectional prepreg with a low fiber basis weight (for example, 70 g / m) that is more likely to flow is arranged on the design surface side. ２ More than 100g / m ２By placing a unidirectional prepreg (described below) on the protrusion side during molding, a molded product with little fiber twist and high protrusion packing can be obtained. Furthermore, when protrusions are on both sides of the plate-shaped part, it is possible to achieve both high protrusion packing and reduced lamination steps by using a low fiber weight for the layer closest to the protrusions and a high fiber weight for the intermediate layer.

[0077] The resin mass fraction (Rc) of the molded article (fiber-reinforced plastic) of the present invention is preferably 10 to 70%. It is more preferably 20 to 60%. If the resin mass fraction (Rc) is less than 10%, the amount of resin on the surface of the molded article is small, which can lead to unevenness of the surface due to the unevenness of the fibers, as well as reduced fiber fluidity, which can result in "unfilled" areas during molding. On the other hand, if the resin mass fraction (Rc) exceeds 70%, the amount of resin is so high that excess resin can occur in recesses, etc., of the molded article ("resin-rich"), and the cure shrinkage of the resin can reduce the smoothness of the surface of the molded article.

[0078] The fiber volume content (Vf) of the molded article of the present invention is preferably 43 to 58%. When the fiber volume content (Vf) is 43% or higher, the resin ratio is not excessive relative to the reinforcing fibers, thereby suppressing the occurrence of localized resin-rich areas. The presence of resin-rich areas can increase the molding shrinkage rate in those areas, resulting in dents on the surface, or serve as the starting point for fracture when a load is applied to the molded article, potentially reducing strength. Furthermore, the lower the proportion of reinforcing fibers and the higher the proportion of resin in the molded article, the lower the strength, rigidity, and impact resistance of the molded article. On the other hand, when the fiber volume content (Vf) is 58% or lower, the amount of resin covering the reinforcing fibers is ensured, preventing exposure of the reinforcing fibers on the surface of the molded article and suppressing the occurrence of unevenness on the design surface and "blurring" due to insufficient resin exudation on the surface of the molded article.

[0079] In the present invention, the reinforcing fibers are not particularly limited, but glass fibers, aramid fibers, polyethylene fibers, silicon carbide fibers, and carbon fibers are preferably used. Glass fibers and carbon fibers are particularly preferred because they are lightweight, have high performance, and can provide fiber-reinforced composite materials with excellent mechanical properties. Glass fibers may be used alone, or carbon fibers may be used alone. In addition, both glass fibers and carbon fibers may be used simultaneously to achieve a balance between performance and cost.

[0080] Here, the glass fiber is not particularly limited, but E-glass fiber, S-glass fiber, C-glass fiber, and D-glass fiber are preferably used. From the viewpoint of the balance between cost and strength, E-glass fiber is preferably used, S-glass fiber is preferably used when high strength is required, C-glass fiber is preferably used when acid resistance is required, and D-glass fiber is preferably used when a low dielectric constant is required.

[0081] Although there is no particular limitation on the average fiber diameter of the glass fibers, the average fiber diameter of the glass fibers is preferably 4 to 20 μm, and more preferably 5 to 16 μm. Usually, a diameter of 4 μm or more can provide sufficient effect, while an average fiber diameter exceeding 20 μm tends to decrease the strength.

[0082] It is also preferable to pre-treat the glass fiber with a coupling agent such as an isocyanate compound, an organic silane compound, an organic titanate compound, an organic borane compound, or an epoxy compound in order to obtain better mechanical strength.

[0083] The carbon fiber is not particularly limited, but polyacrylonitrile-based carbon fiber, rayon-based carbon fiber, pitch-based carbon fiber, etc. are preferably used. Among them, polyacrylonitrile-based carbon fiber, which has high tensile strength, is particularly preferably used. The form of the carbon fiber that can be used includes twisted yarn, untwisted yarn, and non-twisted yarn.

[0084] Such carbon fibers preferably have a tensile modulus in the range of 180 to 600 GPa. If the tensile modulus is in this range, the resulting fiber-reinforced plastic can be made rigid, thereby reducing the weight of the resulting molded product. Furthermore, while carbon fibers generally tend to lose strength as the modulus increases, this range allows the strength of the carbon fibers to be maintained. A more preferred modulus is in the range of 200 to 440 GPa, and even more preferably in the range of 220 to 300 GPa. The range may be any combination of the above upper and lower limits. Here, the tensile modulus of carbon fiber is a value measured in accordance with JIS R7608-2007.

[0085] Commercially available carbon fibers include, but are not limited to, the following: Examples of the torayca (registered trademark) include Torayca (registered trademark) T300, Torayca (registered trademark) T300B, Torayca (registered trademark) T400HB, Torayca (registered trademark) T700SC, Torayca (registered trademark) T800HB, Torayca (registered trademark) T800SC, Torayca (registered trademark) T830HB, Torayca (registered trademark) T1000GB, Torayca (registered trademark) T1100GC, Torayca (registered trademark) M35JB, Torayca (registered trademark) M40JB, Torayca (registered trademark) M46JB, Torayca (registered trademark) M55J, Torayca (registered trademark) M60JB, Torayca (registered trademark) M30SC (all manufactured by Toray Industries, Inc.), PX35 (manufactured by ZOLTEK), and the like.

[0086] When a woven fabric as described below is used for the fiber-reinforced plastic of the present invention, the number of carbon fiber filaments constituting the woven fabric is not particularly limited, but is preferably in the range of 1,000 to 70,000 filaments, and more preferably 1,000 to 60,000 filaments, from the viewpoints of weaving productivity, the tensile and flexural modulus, strength, and design properties required for the fiber-reinforced plastic. A multifilament in which many filaments are aligned provides flexibility and can be easily deformed into any shape during molding. Furthermore, since multifilament fibers can compensate for the shortcomings of one fiber with other fibers, variations in the mechanical properties of the molded product are reduced, resulting in stable performance.

[0087] Next, the matrix resin constituting the fiber reinforced plastic of the present invention will be described. The matrix resin preferably uses a thermosetting resin or a thermoplastic resin as the main component.

[0088] Here, the thermosetting resin as the main component of the matrix resin may be a resin that self-cures upon heating, or may contain a curing agent, a curing accelerator, etc. Preferably, the thermosetting resin undergoes a crosslinking reaction upon heating to form at least a partial three-dimensional crosslinked structure, but is not particularly limited thereto. Examples of thermosetting resins include epoxy resin compositions, vinyl ester resin compositions, unsaturated polyester resin compositions, polyurethane resin compositions, benzoxazine resin compositions, phenolic resins, urea resin compositions, melamine resin compositions, and polyimide resin compositions, which are preferred from the viewpoint of ease of handling. Of these, epoxy resin compositions, vinyl ester resin compositions, and unsaturated polyester resin compositions are more preferred from the viewpoint of the performance and environmental resistance of fiber-reinforced plastics. Furthermore, the thermosetting resin composition containing these does not need to be a single type, and may be a mixture of resin compositions, such as a mixture of resin compositions.

[0089] Furthermore, a thermoplastic resin may be blended with a thermosetting resin by dispersing the thermoplastic resin as particles or fibers in the thermosetting resin, or by dissolving the thermoplastic resin in the thermosetting resin, etc. The thermoplastic resin used in this manner is preferably a thermoplastic resin having a bond selected from carbon-carbon bonds, amide bonds, imide bonds, ester bonds, ether bonds, carbonate bonds, urethane bonds, thioether bonds, sulfone bonds, and carbonyl bonds, but may also have a partially crosslinked structure.

[0090] On the other hand, the thermoplastic resin as the main component of the matrix resin is not particularly limited, but from the viewpoints of ease of processability, mechanical properties, and designability, polymethylene methacrylate (PBSMMA) resin, polyurethane (TPU) resin, polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, acrylonitrile butadiene styrene (ABS) resin, polyamide (PA) resin (particularly PA6, PA66, and PA12), polycarbonate (PC) resin, and PC / ABS resin, which is a blend of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) resin, are preferably used.

[0091] Here, when coloring is required as one of the design features of the fiber reinforced plastic, the color is not particularly limited, but the design feature can be enhanced by coloring the thermoplastic resins listed above with black, red, yellow, green, blue, purple, brown, or the like.

[0092] In the present invention, a non-unidirectional reinforcing fiber sheet such as a woven fabric containing reinforcing fibers can be used in combination with the above-mentioned unidirectional prepreg.

[0093] The reinforcing fibers constituting the non-unidirectional reinforcing fiber sheet can be those described above, but it is preferable that at least a portion of the fibers contain fibers other than thermoplastic resin fibers. When producing the fiber-reinforced plastic of the present invention, heating and press molding are performed, and thermoplastic resin fibers become soft due to heat. Therefore, by using fibers other than thermoplastic resin fibers for at least a portion of the reinforcing fibers constituting the non-unidirectional reinforcing fiber sheet, it is possible to suppress variations in the thickness and shape of the molded product.

[0094] As a form of the non-unidirectional reinforcing fiber sheet, for example, a woven fabric is preferably used. Specifically, when the fiber-reinforced plastic of the present invention has protrusions on only one side of the plate-shaped portion, it is preferable to arrange a woven fabric as the reinforcing fiber forming the outermost layer on the opposite side. Woven fabrics woven with warp and weft yarns not only have excellent mechanical properties and durability of shape, but are also used to enhance the design by revealing the weave of the fabric. Note that the fibers constituting this woven fabric can be the same reinforcing fibers as those in the other layers, but different fibers can also be used.

[0095] The weave structure and density of the woven fabric are not particularly limited and can be selected arbitrarily from the viewpoint of the design properties of the fiber-reinforced plastic. Examples of preferred weave structures include plain weave, twill weave, satin weave, ribbed weave, sash weave, hashisu weave, hack weave, imitation weave, and mat weave. Examples of twill weave include three-ply twill, four-ply twill, five-ply twill, six-ply twill, stretched twill, curved twill, broken twill, jumping twill, chevron twill, sash twill, overlapping twill, twisted twill, day and night twill, decorative twill, and shading twill. Examples of satin weave include five-ply twill, seven-ply twill, eight-ply twill, ten-ply twill, irregular twill, spread twill, overlapping twill, Mikage weave, day and night twill, and shading twill. Examples of ribbed weave include warp ribbed weave, horizontal ribbed weave, and variable ribbed weave. Examples of the diadem weave include regular diadem weave, variable diadem weave, irregular diadem weave, opposite diadem weave, and triaxial fabrics in which fibers are woven in three directions.

[0096] The reinforcing fibers constituting the woven fabric may be the glass fiber alone or the carbon fiber alone, as exemplified above, or a combination of different glass fibers or carbon fibers, or a single or multiple combinations of other different reinforcing fibers. Furthermore, because of its excellent performance, cost, and design, at least one type of glass fiber and at least one type of carbon fiber may be interwoven.

[0097] Furthermore, it is preferable that the woven fabric forming the outermost layer opposite the surface on which the protrusions are provided is pre-impregnated with a matrix resin. It is preferable that the matrix resin impregnated into the woven fabric is the same as that of the other layers, but a different resin can also be used. However, if a resin different from that of the other layers is used, it is preferable to check compatibility and adhesion, and insert an adhesive film or the like as necessary.

[0098] The fiber weight of the woven fabric is preferably 10 to 300 g / m ２ and more preferably 30 to 150 g / m ２ The fiber weight of the woven fabric is 10 g / m ２ In the above cases, the plastic flow of the fibers imparted by the pressure generated during press molding can be suppressed, and poor appearance such as meandering of the woven fibers used in the surface layer and resin-richness of the design surface can be suppressed. ２ In the following cases, the fiber reinforced plastic is flexible and has excellent formability, and when impregnated with an epoxy resin composition or the like during molding, the resin easily reaches the center in the thickness direction, and unimpregnated areas (voids) are less likely to remain. As a result, the fiber reinforced plastic exhibits excellent mechanical properties such as compressive strength.

[0099] Furthermore, when glass fiber or carbon fiber is used as the reinforcing fiber, the basis weight of the prepreg obtained by impregnating the woven fabric with the matrix resin is preferably 20 to 400 g / m ２ and more preferably 40 to 300 g / m ２ The basis weight is 20 g / m ２ In this case, the weaving property is good, and the weight is 400 g / m ２ In the following cases, the woven fabric is flexible and easy to shape, and when impregnated with a matrix resin (e.g., an epoxy resin composition) during prepreg production or molding, the resin easily reaches the center in the thickness direction, making it less likely that unimpregnated areas (voids) will remain. As a result, a fiber-reinforced plastic is obtained that exhibits excellent mechanical properties such as compressive strength.

[0100] Furthermore, when a woven fabric is disposed on the outermost layer opposite the surface on which the protrusions are provided, the mesh thickness 107 of the fiber-reinforced plastic woven fabric 104 is preferably 0.25 mm or less, as shown in FIG. 12 . Here, the mesh thickness of the woven fabric refers to the thickness of each of the warp and weft yarns in the woven state (not the thickness of the reinforcing fiber bundles themselves before weaving), and refers to the length of the warp and weft yarns in the thickness direction of the plate-shaped portion in the cross section. Unlike unidirectional prepregs, woven fabrics with woven warp and weft yarns have crimps in the reinforcing fiber bundles, and the greater the mesh thickness of the fabric, the greater the crimp. Furthermore, the greater the crimp, the more likely it is that a step 108 between the warp and weft yarns will occur. Air contained in the pre-molded prepreg is pushed out by the resin flow due to the pressurization during molding. However, if the step between the warp and weft yarns is large, the air will remain in the step and remain on the surface of the molded product as air bubbles 109, which may deteriorate the appearance quality of the molded product. When the mesh thickness of the woven fabric is 0.25 mm or less, the difference in level between the warp and weft threads is not too large, and bubbles are less likely to occur on the surface of the molded product, resulting in a good appearance.

[0101] As a means for adjusting the mesh thickness 107 of the woven fabric in fiber-reinforced plastic to 0.25 mm or less, for example, a method of molding using a prepreg with a thin mesh thickness can be considered. However, when the unidirectional prepreg flows into the grooves of the mold for forming the protrusions during molding, the woven fabric prepreg may also be drawn in along with the flow of the resin and fibers of the unidirectional prepreg, which may cause the shape of the mesh of the woven fabric to change. Therefore, the mesh thickness of the woven fabric as a molded product is not uniformly determined by the mesh thickness of the woven fabric prepreg used. Therefore, in terms of materials, for example, unidirectional prepreg with slits inserted or a fiber basis weight of 100 g / m ２It is also preferable to use a unidirectional prepreg with a low basis weight as described below, and to set the fiber direction of the unidirectional prepreg at as low an angle as possible with respect to the extension direction of the protrusions. This improves the filling of the unidirectional prepreg into the protrusions, making it less likely that resin will become rich at the base of the protrusions, and reducing the movement of the mesh shape of the woven fabric prepreg. In terms of molding conditions, it is also preferable to allow a preheating time between placing the prepreg in a heated mold and applying pressure, in order to optimize the resin viscosity of the prepreg at the time of pressurization. Furthermore, it is also preferable to mold with a temperature difference between the mold on the design surface side and the mold on the protrusion side, so that the mesh of the woven fabric is less likely to move and the unidirectional prepreg can more easily fill the grooves of the protrusions.

[0102] In addition, nonwoven fabric can also be preferably used as the form of the non-unidirectional reinforcing fiber sheet. Nonwoven fabric is preferably used, for example, inside a plate-shaped part where design is not required. Placing nonwoven fabric inside can also result in improving the design of the surface of the molded product.

[0103] The structure and manufacturing method of the nonwoven fabric are not particularly limited, but preferred are nonwoven fabrics manufactured by dry methods such as the carding method, in which short fibers of several centimeters are opened and a thin web is formed using a carding machine, or the airlaid method, in which the opened short fibers are dispersed using an air randomizer and a web is formed on a belt conveyor. In addition, nonwoven fabrics manufactured by dry methods preferably include those in which the fibers are entangled using a needle punching method to physically improve the dimensional stability of the web, or those in which a binder resin such as unsaturated polyester, polyvinyl alcohol (PVA), or a copolymer thereof is applied using a spraying or dipping method to bond the fibers together, thereby chemically improving the dimensional stability of the web. Examples of fiber bonding methods include blending thermoplastic resin fibers during web manufacturing, and attaching thermoplastic resin microparticles to the web and then placing the web in a heated roller or oven to melt the thermoplastic resin and bond the fibers together.

[0104] As another example of nonwoven fabric, a nonwoven fabric produced by a wet method in which short fibers are dispersed in water and scooped up onto a papermaking net can also be preferably used. Note that, in order to improve the dimensional stability and handleability of a nonwoven fabric produced by a wet method in the same way as a nonwoven fabric produced by a dry method, it is also preferable to apply a binder resin such as unsaturated polyester, polyvinyl alcohol (PVA) or a copolymer thereof by a spraying method or a dipping method to chemically bond the fibers together, or to mix fibers of a thermoplastic resin during web production, or to attach thermoplastic resin particles to the web, and then to place the web in a heated roller or oven to melt the thermoplastic resin and bond the fibers together.

[0105] As nonwoven fabrics other than those mentioned above, nonwoven fabrics produced by a spunbond method in which threads obtained by melt-spinning a thermoplastic resin are layered on a belt conveyor, or a meltblown method in which air is blown onto melt-spun threads to turn them into fine fibers, and the fibers are accumulated on a net to form a web, can also be preferably used because they have excellent mechanical properties and are inexpensive.

[0106] The weight of the nonwoven fabric is 10 to 300 g / m ２ In order to absorb deformation of the prepreg during molding and mitigate the effect on the surface of the molded article, thickness and strength are necessary, but if it is too thick, there is a possibility that it will affect the physical properties of the molded article, so it is more preferable that the thickness is 30 to 150 g / m ２ and most preferably 40 to 100 g / m ２ However, it is also possible to adjust the basis weight within the above range by stacking nonwoven fabrics with lower basis weights.

[0107] Furthermore, when the non-unidirectional reinforcing fiber sheet is provided on the surface layer of a plate-shaped portion, its thickness is preferably 0.01 to 1.0 mm, and more preferably 0.05 to 0.5 mm. When the thickness of the non-unidirectional reinforcing fiber sheet is 0.01 mm or more, the plastic flow of the fibers imparted by the pressure generated during press molding can be suppressed, thereby suppressing poor appearance such as meandering of the woven fibers used in the surface layer of the plate-shaped portion and resin-rich design surfaces. On the other hand, when the thickness of the non-unidirectional reinforcing fiber sheet is 1.0 mm or less, the sheet is flexible and has excellent formability. Furthermore, when impregnated with an epoxy resin composition or the like during molding, the resin easily reaches the center in the thickness direction, reducing the likelihood of unimpregnated portions (voids). As a result, the resulting fiber-reinforced plastic exhibits excellent mechanical properties such as compressive strength.

[0108] However, when a nonwoven fabric is used as the non-unidirectional reinforcing fiber sheet, the thickness of the nonwoven fabric can be adjusted by the pressure during press molding, so the nonwoven fabric preferably has a thickness of 0.01 to 3.0 mm.

[0109] Next, an example of the method for producing a fiber-reinforced plastic according to the present invention will be described in detail, but the present invention is not limited to this example.

[0110] The fiber-reinforced plastic of the present invention can be obtained, for example, by laminating a unidirectional prepreg in which a large number of reinforcing fibers are impregnated with a matrix resin with the same or different types of unidirectional prepreg or fiber substrate as necessary, and integrating the laminate by heating and, if necessary, pressurizing the laminate by press molding, autoclave molding, oven molding, or vacuum oven molding.

[0111] As a molding method, various molding methods can be mentioned as described above, and there is no particular limitation, but a press molding method in which a unidirectional prepreg impregnated with a matrix resin is prepared, laminated or shaped as necessary, placed in a mold, and molded by heating and pressurizing with a press can be preferably used. In press molding, molding at high pressure integrates the reinforcing fibers and the matrix resin, thereby reducing the effects of fiber slack and angle variation.

[0112] The cavity (gap) of the mold used in press molding has the final shape of the desired fiber-reinforced plastic, and the mold's shape where the protrusions of the fiber-reinforced plastic meet is recessed. In press molding, the reinforcing fibers and matrix resin flow into the recesses during heat molding, allowing the shape of the fiber-reinforced plastic to be formed. This means that it is not necessary to pre-shape the unidirectional prepreg into the same shape as the fiber-reinforced plastic. This is preferable because it reduces the number of steps required to produce the preform.

[0113] The press molding method is superior in productivity because the pre-molding preparation and post-molding treatment are simpler than other molding methods. Furthermore, when the matrix resin is a thermosetting resin, it is possible to demold the mold while maintaining the mold temperature T substantially constant. Therefore, the mold cooling step required when the matrix resin is a thermoplastic resin is not required, and when combined with a fast-curing resin, high productivity can be achieved.

[0114] The mold temperature T (°C) for press molding preferably satisfies the following relational expression (I) with the exothermic peak temperature Tp (°C) of the thermosetting resin measured by differential scanning calorimetry (DSC): More preferably, the mold temperature T (°C) for press molding more preferably satisfies the following relational expression (II):

[0115] Tp - 60 ≦ T ≦ Tp + 20 (I) Tp - 30 ≦ T ≦ Tp (II) If the mold temperature T (°C) is lower than Tp - 60 (°C), the time required for curing the resin becomes very long and curing may be insufficient. On the other hand, if it is higher than Tp + 20 (°C), a sudden reaction of the resin may cause the formation of voids inside the resin and poor curing. The exothermic peak temperature Tp (°C) measured by DSC is a value measured at a temperature rise rate of 10°C / min.

[0116] The fiber-reinforced plastic of the present invention is preferably produced under conditions in which the thermosetting resin used as the matrix resin has a minimum viscosity of 0.1 to 100 Pa·s as measured by dynamic mechanical analysis (DMA). It is more preferably 0.5 to 10 Pa·s. If the minimum viscosity is less than 0.1 Pa·s, only the resin flows when pressure is applied, and the reinforcing fibers may not be sufficiently filled up to the tips of the protrusions. On the other hand, if the viscosity is greater than 100 Pa·s, the resin has poor fluidity, and the reinforcing fibers and resin may not be sufficiently filled up to the tips of the protrusions. The minimum viscosity measured by DMA is a value measured at a heating rate of 1.5°C / min.

[0117] In the present invention, it is preferable to first laminate a unidirectional prepreg, in which a large number of reinforcing fibers are impregnated with a matrix resin, together with the same or different types of unidirectional prepreg, a non-unidirectional reinforcing fiber sheet, or other fiber substrates, as necessary, to form a preform, and then place the preform in a preheated mold (for example, a concave mold). The mold is then closed and pressurized to obtain a fiber-reinforced plastic having a plate-like portion and at least one protrusion protruding from at least one surface of the plate-like portion. In this case, it is preferable that the fiber orientation direction of at least one layer of unidirectional prepreg in the preform is neither parallel nor perpendicular to the length direction of the protrusion (so that it is non-parallel and non-perpendicular).

[0118] In the present invention, the required number of unidirectional prepregs can be laminated depending on the desired thickness of the fiber-reinforced plastic, but in this case, it is preferable that the fiber orientation direction of all the unidirectional prepregs is not parallel or perpendicular to the width direction (length direction) in the cross section of the protrusion.

[0119] Furthermore, as described above, when a unidirectional prepreg is combined with another unidirectional prepreg, a non-unidirectional reinforcing fiber sheet, or a fiber substrate, it is also preferable to place a non-unidirectional reinforcing fiber sheet in the second or subsequent layer from the surface of the preform (i.e., a layer other than the outermost layer on the side where the protrusions are provided). In particular, when a woven non-unidirectional reinforcing fiber sheet is placed in the outermost layer opposite the surface where the protrusions are provided, the plastic flow of the fibers caused by the pressure during press molding can be suppressed, and poor appearance such as meandering of the woven fibers used in the surface layer and resin-rich design surfaces can be suppressed.

[0120] The non-unidirectional reinforcing fiber sheet may be a dry sheet containing no matrix resin, or a prepreg-like sheet in which at least a portion of the sheet is pre-impregnated with a matrix resin.

[0121] When the non-unidirectional fiber reinforced sheet is a prepreg-like sheet, the matrix resin with which the non-unidirectional fiber reinforced sheet is pre-impregnated is preferably the same resin as that of the other prepregs, but any resin preferable from the viewpoints of adhesion and moldability can be selected.

[0122] Furthermore, when the non-unidirectional fiber-reinforced sheet is a prepreg-like sheet, the fiber volume fraction Vf[a] of the non-unidirectional reinforcing fiber sheet and the fiber volume fraction Vf[b] of the unidirectional prepreg preferably have a relationship of Vf[a] > Vf[b]. In this case, there is room for the matrix resin contained in the unidirectional prepreg to be impregnated into the non-unidirectional reinforcing fiber sheet during press molding. That is, due to the pressure during press molding, the resin contained in the unidirectional prepreg is impregnated into the resin-unimpregnated portion of the non-unidirectional reinforcing fiber sheet, resulting in a molded product that is sufficiently filled with resin, and a fiber-reinforced plastic with excellent mechanical properties, for example, a void fraction of 2% or less, can be obtained.

[0123] Furthermore, Vf[a] is preferably 55 to 99.9%, more preferably 80 to 99%. When Vf[a] is 55% or more, the resin is less susceptible to the flow of resin caused by the pressure applied during press molding, and fiber flow can be suppressed, so that a fiber-reinforced plastic having excellent appearance quality with little fiber disorder and minimal surface irregularities can be obtained.

[0124] The present invention will now be further described with reference to examples and comparative examples, but the present invention is not limited thereto. Conditions and results are shown in Tables 1 to 4.

[0125] <Painting treatment on the design surface of a molded article> A filler (ROMEN Filler Black 9-7606, Mikuni Paint Co., Ltd.) was applied to the surface (design surface) opposite the surface with the protrusions of the molded article. After sufficient drying, the surface was sanded with #400 sanding paper and a primer (Origin Co., Ltd. Origin Primer U-03) was applied. Then, a coating agent (Origin Co., Ltd. Planet HS) was applied twice with a spray gun.

[0126] <Appearance quality: inspection of rib streaks on the design surface> "Rib streaks," a phenomenon in which depressions occur directly below protrusions and distortion occurs due to disturbances in the fiber orientation direction, were confirmed on the design surface of molded products before and after painting. Specifically, the top of the plate was held in the hand with the protrusions facing downward, and the surface (design surface) opposite the surface having the protrusions of the plate-like part was visually observed under a fluorescent lamp (illuminance 1200 lx (lux)) before and after painting using the method described above in <Painting treatment on the design surface of molded products>.

[0127] During this process, the molded product was rotated 360° horizontally and tilted vertically at angles from 0° to 60°, and observed to check for any distortion in the reflected light of the fluorescent lamp along the ribs. As a result, a molded product that showed no distortion or dents at any angle without painting was rated "A," a molded product that showed distortion only at a certain angle before painting but no distortion or dents at any angle after painting was rated "B," a molded product that showed distortion only at a certain angle after painting but no dents after painting was rated "C," and a molded product that showed distortion or dents at any angle after painting was rated "D."

[0128] <Appearance quality: inspection for smearing on the design surface> We checked for "smearing," a phenomenon in which fibers are exposed due to insufficient resin seepage, on the design surface of molded products before painting. Specifically, we held the top of the plate in our hand with the protruding part facing downward, and visually observed the surface (design surface) opposite the surface with the protruding part of the plate-like part before painting under a fluorescent lamp (illuminance 1200 lx (lux)).

[0129] At this time, the molded product was rotated 360 degrees horizontally and then tilted vertically at angles between 0 and 60 degrees while being observed. Those that showed no smearing on the entire design surface at any angle were rated as "A", those that showed partial smearing only at certain angles but that could be hidden by painting were rated as "B", and those that showed smearing on the entire design surface and could not withstand painting were rated as "C".

[0130] <Appearance quality: inspection for air bubbles on the textile design surface> The presence or absence of air bubbles was confirmed on the design surface of the molded product before painting. Specifically, the top of the plate was held in a hand with the protrusions facing downward, and the surface of the plate opposite the surface with the protrusions (the textile design surface) was visually observed under a fluorescent lamp (illuminance 1200 lx (lux)) before painting.

[0131] The molded product was rotated 360° horizontally and tilted vertically at angles between 0° and 60°, and the number of bubbles visible to the naked eye was counted. Those with three or fewer bubbles across the entire surface of the woven fabric design were rated "A," and those with more than three bubbles were rated "B."

[0132] <Measurement of the mesh thickness of the fabric in the cross section of the molded article> The protruding portion was cut out using a disc grinder so as to include the plate-like portion, and the cut surface was polished. The cut surface was then observed using a microscope (Keyence Corporation, VHX-6000) to measure the mesh thickness of the fabric. Note that in the image of a cross section observed with the microscope, the mesh thickness varied slightly depending on the mesh being measured, but the mesh with the maximum thickness was recorded as the mesh thickness of the fabric in the molded article.

[0133] <Inspection of resin-richness of cross section of protrusion> The protrusion was cut out using a disc grinder so as to include the plate-like portion, and the cut surface was polished. The cut surface was then observed using a microscope (Keyence Corporation, VHX-6000) to confirm the presence or absence of resin-richness. In the cross-sectional image, if the resin-rich area in one location relative to the total area of ​​the protrusion and the plate-like portion directly below the protrusion was less than 3%, it was rated as "A", if it was 3% or more but less than 5%, it was rated as "B", and if it was 5% or more, it was rated as "C". However, if there were multiple resin-rich locations, the location with the largest area was used for judgment.

[0134] <Measurement of maximum width w of protrusion and total thickness t' of unidirectional layer inside plate-like portion (unidirectional layer located on the protrusion side of the non-unidirectional layer)> The protrusion was cut out using a disc grinder so as to include the plate-like portion, and the cut surface was polished. The cut surface was then observed using a microscope (Keyence Corporation, VHX-6000), and the maximum width w of the protrusion and the total thickness t' of the unidirectional layer inside the plate-like portion (unidirectional layer located on the protrusion side of the non-unidirectional layer) were calculated from the captured image.

[0135] <Measurement of thickness t of plate-like portion> The thickness of each of the plate-like portions on the left and right sides of the protrusion was measured at one location with a micrometer, and the smaller thickness was taken as the thickness t of the plate-like portion.

[0136] <Measurement of the radius of curvature R of the joint between the protrusion and the plate-like portion> The radius of curvature of the curved surface formed by the plate-like portion and the protrusion was measured on both the left and right sides of the protrusion using a radius gauge, and the larger radius was taken as the radius of curvature R.

[0137] <Measurement of fiber volume content (Vf)> The specific gravity of the molded article was measured using a specific gravity meter (ELECTRONIC DENSIMETER SD-200L, manufactured by ALFA MIRAGE) by the underwater displacement method. Next, the fiber volume content was calculated using the specific gravity of the obtained molded article, the specific gravity of the reinforcing fibers in the prepreg used, and the specific gravity of the matrix resin according to the following formula: Fiber volume content (Vf) (%) = (specific gravity of molded article - specific gravity of resin) / (specific gravity of reinforcing fiber - specific gravity of resin) x 100.

[0138] Example 1: Unidirectional prepreg #P384-S-10 (carbon fiber (4,900 MPa, tensile modulus 235 GPa), FAW = 100 g / m) manufactured by Toray Industries, Inc. ２ Four prepreg base materials, each measuring 100 mm x 100 mm, were cut out from a thermosetting epoxy resin (Rc = 40%). ２ The prepreg substrate laminate (preform) was prepared by laminating the layers so as to obtain a laminate.

[0139] Next, a 100 mm x 100 mm concave mold was prepared as the lower mold, and a 100 mm x 100 mm convex mold having a groove for forming a protrusion (rib) in the center of the convex portion (rib groove, linear shape with a maximum width of 1.5 mm, a tip width of 1.0 mm, a curvature radius of 0.2 mm, a depth of 3 mm, and a length of 60 mm) was prepared as the upper mold, and they were heated to 150°C.

[0140] The prepreg base laminate prepared in advance was placed in the lower mold with the 0° direction during lamination parallel to the rib grooves, and the upper mold was attached to the lower mold. After that, molding and heat-curing of the matrix resin were carried out using a heated press molding machine under conditions of a pressure of 12 MPa, a heating temperature of 150°C, and a pressure time of 3 minutes, to obtain a fiber-reinforced plastic with ribs.

[0141] The resulting fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like section, and external observation of the rib revealed that the carbon fiber was filled all the way to the tip of the rib. Measurements were made using the methods described above in "Measurement of the maximum width w of the protrusions and the total thickness t' of the unidirectional layers inside the plate-like section (the unidirectional layers located closer to the protrusions than the non-unidirectional layers)," "Measurement of the thickness t of the plate-like section," and "Measurement of the radius of curvature R of the joint between the protrusions and the plate-like section." The maximum width w of the protrusions was 1.5 mm, the radius of curvature R of the curved surface formed by the protrusions and the plate-like section was 0.2 mm, and the thickness t of the plate-like section was 0.3 mm, resulting in a w / t ratio of 5. Furthermore, because the plate-like section was entirely composed of unidirectional layers, t = t' for this molded product.

[0142] The molded article thus obtained was inspected by the method described above in <Appearance Quality: Inspection of Rib Streaks on Design Surface>, and no distortion was observed in the reflected light from the fluorescent lamp at any angle, even without painting.

[0143] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0144] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 60%.

[0145] Example 2 A roller cutter with a blade attached to a cylinder was pressed against a unidirectional prepreg P384-S-10 manufactured by Toray Industries, Inc. to insert slits into the reinforcing fibers of this prepreg in the slit pattern shown in FIG. 6 so that the fiber length was 13 mm, the slit width Ws was 0.25 mm, and the slit angle θ was ±14°, thereby obtaining a slit-inserted prepreg.

[0146] Four prepreg base sheets, each measuring 100 mm x 100 mm, were cut out from this cut-inserted prepreg. ２ This prepreg substrate laminate was used to perform molding under the same conditions as in Example 1, to obtain a fiber-reinforced plastic.

[0147] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm x plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 1.5 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 0.2 mm, and the thickness t of the plate-like portion was 0.3 mm, resulting in a w / t ratio of 5. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0148] When inspected in the same manner as in Example 1 using the method described above in <Appearance Quality: Rib Inspection on Design Surface>, there was no distortion in the reflected light from the fluorescent lamp at any angle, even without painting.

[0149] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0150] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 60%.

[0151] In addition, when inspected by the method described in <Inspection of resin-rich area in cross section of protrusion>, the resin-rich area was less than 3% of the total area of ​​the protrusion and the plate-like portion immediately below the protrusion.

[0152] Example 3 Eight prepreg base materials each measuring 100 mm x 100 mm were cut out from the prepreg with slits inserted in the same manner as in Example 2, and the laminated structure was [+45 / -45] ４ This prepreg base laminate was press-molded under the same conditions as in Example 1 to obtain a fiber-reinforced plastic, except that an upper mold was used in which the rib grooves for forming the protrusions (ribs) had a straight line shape with a maximum width of 2.0 mm, a tip width of 1.0 mm, a curvature radius of 0.5 mm, a depth of 3 mm, and a length of 60 mm.

[0153] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 2.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 0.5 mm, the thickness t of the plate-like portion was 0.7 mm, and w / t was 3. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0154] When inspected in the same manner as in Example 1 using the method described above in <Appearance Quality: Rib Inspection on Design Surface>, there was no distortion in the reflected light from the fluorescent lamp at any angle, even without painting.

[0155] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0156] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 60%.

[0157] Example 4 Six prepreg base sheets, each measuring 100 mm x 100 mm, were cut out from the prepreg with slits inserted in the same manner as in Example 2, and the laminated structure was [+45 / -45]. ３This prepreg base laminate was press-molded under the same conditions as in Example 1 to obtain a fiber-reinforced plastic, except that an upper mold was used in which the rib grooves for forming the protrusions (ribs) had a straight line shape with a maximum width of 5.0 mm, a tip width of 1.0 mm, a curvature radius of 1.0 mm, a depth of 3 mm, and a length of 60 mm.

[0158] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 5.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 1.0 mm, the thickness t of the plate-like portion was 0.5 mm, and w / t was 10. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0159] When inspected in the same manner as in Example 1, it was found that before painting, the reflected light from the fluorescent lamp was distorted only at a certain angle, but after painting, there was no distortion at any angle.

[0160] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0161] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 60%.

[0162] [Example 5] Four prepreg base sheets each measuring 100 mm x 100 mm (fiber basis weight 100 g / m) were prepared from the prepreg with slits inserted in the same manner as in Example 2. ２ Furthermore, a unidirectional prepreg P384-S-20 (carbon fiber (4,900 MPa, tensile modulus 235 GPa), FAW = 200 g / m) manufactured by Toray Industries, Inc. was cut out. ２ In the same manner as in Example 2, cuts were made in a thermosetting epoxy resin (Rc=40%), and one prepreg base material (fiber basis weight 200 g / m) was cut into the base material so that each sheet had a size of 100 mm x 100 mm. ２ The laminated structure was [(fiber basis weight 200 g / m ２ ) + 45] [(fiber basis weight 100 g / m ２ ) -45 / +45]２ A prepreg base laminate was prepared by laminating the sheets so as to form a laminate.

[0163] Using this prepreg base laminate, a fiber basis weight of 200 g / m ２ The prepreg was placed on the lower mold side and molded using the same mold and conditions as in Example 4 to obtain a fiber reinforced plastic.

[0164] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 5.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 1.0 mm, the thickness t of the plate-like portion was 0.5 mm, and w / t was 10. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0165] When inspected in the same manner as in Example 1, there was no distortion in the reflected light of the fluorescent lamp at any angle, even without any coating.

[0166] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0167] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 60%.

[0168] Example 6 Six prepreg base sheets, each measuring 100 mm x 100 mm, were cut out from the prepreg with slits inserted in the same manner as in Example 2, and the laminated structure was [+45 / -45]. ３ When laminating the sheets, a non-resin-impregnated glass mat (60 g / m²) is placed between the first and second layers. ２ ) was placed in the lower mold so that the glass mat was the second layer from the bottom, and molding was carried out using the same mold and conditions as in Example 4 to obtain a fiber-reinforced plastic.

[0169] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 5.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 1.0 mm, the thickness t of the plate-like portion was 0.5 mm, and w / t was 10. Furthermore, the total thickness t' of the unidirectional layer located on the protrusion side of the glass mat was 0.4 mm, and w / t' was 13.

[0170] When inspected in the same manner as in Example 1, there was no distortion in the reflected light of the fluorescent lamp at any angle, even without any coating.

[0171] Furthermore, when inspected by the method described in <Appearance Quality: Inspection of Smudges on Design Surface>, smudges were observed on the entire design surface, and it was found that the product was not suitable for painting.

[0172] Furthermore, when measured by the method described in <Measurement of fiber volume content (Vf)>, Vf was found to be 64%.

[0173] Example 7 Nineteen prepreg base materials, each measuring 100 mm x 100 mm, were cut out from the prepreg with slits inserted in the same manner as in Example 2, and the laminate structure was [+45 / -45]. ９ This prepreg base laminate was press-molded under the same conditions as in Example 1 to obtain a fiber-reinforced plastic, except that an upper mold was used in which the rib grooves for forming the protrusions (ribs) had a maximum width of 8.0 mm, a tip width of 1.0 mm, a curvature radius of 2.0 mm, a depth of 3 mm, and a length of 60 mm in a straight line shape.

[0174] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 8.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 2.0 mm, the thickness t of the plate-like portion was 1.8 mm, and w / t was 4. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0175] When inspected in the same manner as in Example 1, there was no distortion in the reflected light of the fluorescent lamp at any angle, even without any coating.

[0176] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0177] Furthermore, when measured by the method described in <Measurement of fiber volume content (Vf)>, Vf was found to be 59%.

[0178] Example 8 Four prepreg base sheets each measuring 100 mm x 100 mm were cut out from the prepreg with slits inserted in the same manner as in Example 2, and the laminated structure was [+45 / -45]. ２ This prepreg base laminate was press molded using the same mold and conditions as in Example 7 to obtain a fiber reinforced plastic.

[0179] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 8.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 2.0 mm, the thickness t of the plate-like portion was 0.3 mm, and w / t was 27. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0180] When inspected in the same manner as in Example 1, it was found that before painting, the reflected light was distorted at all angles, but after painting, the distortion was only observed at a certain angle, but no dents were found.

[0181] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0182] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 60%.

[0183] Example 9: Eleven prepreg base sheets, each measuring 100 mm x 100 mm, were cut out from the prepreg with slits inserted in the same manner as in Example 2, and the laminated structure was [+45 / -45]. ５ The laminate was then laminated so that the thickness was [+45]. Underneath this, a woven fabric prepreg (#CO6343B carbon fiber, tensile strength 3,530 MPa, tensile modulus 230 GPa, basis weight 198 g / m) manufactured by Toray Industries, Inc. was used as a design surface substrate. ２ ) was placed on the lower mold side, and this prepreg base laminate was press-molded using the same mold and conditions as in Example 7 so that the woven fabric prepreg was on the lower mold side, to obtain a fiber-reinforced plastic.

[0184] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 8.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 2.0 mm, the thickness t of the plate-like portion was 1.2 mm, and w / t was 7. Furthermore, the total thickness t' of the unidirectional layer located closer to the protrusion than the non-unidirectional layer was 1.0 mm, and w / t' was 8.

[0185] When inspected in the same manner as in Example 1, there was no distortion in the reflected light of the fluorescent lamp at any angle, even without any coating.

[0186] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0187] Furthermore, when measured by the method described in <Measurement of fiber volume content (Vf)>, Vf was found to be 61%.

[0188] When <Appearance quality: bubble inspection on the woven fabric design surface> was carried out, the number of bubbles that could be visually confirmed was 10.

[0189] Furthermore, when the thickness of the woven fabric in the cross section of the molded article was measured, the thickness was 0.28 mm.

[0190] Example 10 Nine prepreg base sheets, each measuring 100 mm x 100 mm, were cut out from the prepreg with slits inserted in the same manner as in Example 2, and the laminated structure was [+45 / -45]. ４ The prepreg substrate laminate was press-molded using the same mold and conditions as in Example 7 to obtain a fiber-reinforced plastic.

[0191] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 8.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 2.0 mm, the thickness t of the plate-like portion was 0.8 mm, and w / t was 10. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0192] When inspected in the same manner as in Example 1, it was found that before painting, the reflected light from the fluorescent lamp was distorted only at a certain angle, but after painting, there was no distortion at any angle.

[0193] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0194] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 60%.

[0195] Example 11 Nine prepreg base sheets, each measuring 100 mm x 100 mm, were cut out from the prepreg with slits inserted in the same manner as in Example 2, and the laminated structure was [+45 / -45]. ４ This prepreg base laminate was press-molded under the same conditions as in Example 1 to obtain a fiber-reinforced plastic, except that an upper mold was used in which the rib grooves for forming the protrusions (ribs) had a maximum width of 9.0 mm, a tip width of 1.0 mm, a curvature radius of 3.0 mm, a depth of 3 mm, and a length of 60 mm in a straight line shape.

[0196] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 9.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 3.0 mm, and the thickness t of the plate-like portion was 0.8 mm, resulting in a w / t ratio of 11. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0197] When inspected in the same manner as in Example 1, it was found that before painting, the reflected light was distorted at all angles, but after painting, the distortion was only observed at a certain angle, but no dents were found.

[0198] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0199] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 60%.

[0200] Example 12 Nineteen prepreg base materials, each measuring 100 mm x 100 mm, were cut out from the prepreg with slits inserted in the same manner as in Example 2, and the laminate structure was [+45 / -45]. ９ This prepreg base laminate was press-molded under the same conditions as in Example 1 to obtain a fiber-reinforced plastic, except that an upper mold was used in which the rib grooves for forming the protrusions (ribs) had a maximum width of 0.9 mm, a tip width of 0.4 mm, a curvature radius of 0.2 mm, a depth of 3 mm, and a length of 60 mm in a straight line shape.

[0201] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 0.9 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 0.2 mm, the thickness t of the plate-like portion was 1.8 mm, and w / t was 0.5. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0202] When inspected in the same manner as in Example 1, there was no distortion in the reflected light of the fluorescent lamp at any angle, even without any coating.

[0203] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0204] Furthermore, when measured by the method described in <Measurement of fiber volume content (Vf)>, Vf was found to be 59%.

[0205] [Example 13] Two prepreg base sheets each measuring 100 mm x 100 mm (fiber basis weight 100 g / m) were prepared from the prepreg with slits inserted in the same manner as in Example 2. ２ Furthermore, a unidirectional prepreg P384-S-20 (carbon fiber (4,900 MPa, tensile modulus 235 GPa), FAW = 200 g / m) manufactured by Toray Industries, Inc. was cut out. ２ In the same manner as in Example 2, cuts were made in a thermosetting epoxy resin (Rc=40%), and one prepreg base material (fiber basis weight 200 g / m) was cut into the base material so that each sheet had a size of 100 mm x 100 mm. ２ The laminated structure was [(fiber basis weight 100 g / m ２ ) +45 / -45] [(fiber basis weight 200g / m ２ ) + 45] to prepare a prepreg base laminate.

[0206] This prepreg base laminate was used to fabricate a laminate with a fiber basis weight of 100 g / m ２ The prepreg was placed on the lower mold side, and molding was carried out using the same mold and conditions as in Example 2 to obtain a fiber-reinforced plastic.

[0207] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 1.5 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 0.2 mm, and the thickness t of the plate-like portion was 0.3 mm, resulting in a w / t ratio of 5. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0208] When inspected in the same manner as in Example 1, there was no distortion in the reflected light of the fluorescent lamp at any angle, even without any coating.

[0209] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0210] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 60%.

[0211] Furthermore, when inspected by the method described in <Inspection of resin-rich area in cross section of protrusion>, the resin-rich area was 5% or more of the total area of ​​the protrusion and the plate-like portion immediately below the protrusion.

[0212] Example 14: Unidirectional prepreg #P384-S-10 (carbon fiber (4,900 MPa, tensile modulus 235 GPa), FAW = 100 g / m) manufactured by Toray Industries, Inc. ２ , thermosetting epoxy resin, Rc=42%) was cut in the same manner as in Example 2. Four prepreg base materials each measuring 100 mm x 100 mm were cut out from this cut-in prepreg, and the laminated structure was [+45 / -45] ２ This prepreg substrate laminate was used to perform molding under the same mold and conditions as in Example 2, except that the applied pressure was 6 MPa, to obtain a fiber-reinforced plastic.

[0213] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 1.5 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 0.2 mm, and the thickness t of the plate-like portion was 0.3 mm, resulting in a w / t ratio of 5. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0214] As in Example 2, <Appearance quality: Inspection of rib streaks on the design surface>, <Appearance quality: Inspection of smudges on the design surface>, <Measurement of fiber volume fraction (Vf)>, and <Inspection of resin richness on the cross section of protrusions> were performed. In the <Appearance quality: Inspection of rib streaks on the design surface>, there was no distortion in the reflected light from the fluorescent lamp at any angle, even without painting. Furthermore, in the <Appearance quality: Inspection of smudges on the design surface>, no smudges were observed across the entire design surface at any angle. Furthermore, in the <Measurement of fiber volume fraction (Vf)>, Vf was 54%. In the <Inspection of resin richness on the cross section of protrusions>, the resin richness was less than 3%.

[0215] Example 15: Unidirectional prepreg #P384-S-10 manufactured by Toray Industries, Inc. (carbon fiber (4,900 MPa, tensile modulus 235 GPa), FAW = 100 g / m ２ , thermosetting epoxy resin, Rc=55%) was cut in the same manner as in Example 2. Four prepreg base materials each measuring 100 mm x 100 mm were cut out from this cut-in prepreg, and the laminated structure was [+45 / -45] ２ This prepreg substrate laminate was used for molding under the same mold and conditions as in Example 14 to obtain a fiber reinforced plastic.

[0216] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm x plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 1.5 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 0.2 mm, and the thickness t of the plate-like portion was 0.3 mm, resulting in a w / t ratio of 5. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0217] As in Example 2, <Appearance quality: Inspection of rib streaks on the design surface>, <Appearance quality: Inspection of smudges on the design surface>, <Measurement of fiber volume fraction (Vf)>, and <Inspection of resin-richness on the cross-section of protrusions> were performed. In the <Appearance quality: Inspection of rib streaks on the design surface>, there was no distortion in the reflected light from the fluorescent lamp at any angle, even without painting. Furthermore, in the <Appearance quality: Inspection of smudges on the design surface>, no smudges were observed across the entire design surface at any angle. Furthermore, in the <Measurement of fiber volume fraction (Vf)>, Vf was 40%. In the <Inspection of resin-richness on the cross-section of protrusions>, the resin-richness was 5% or more.

[0218] Example 16: Unidirectional prepreg #P384-S-10 manufactured by Toray Industries, Inc. (carbon fiber (4,900 MPa, tensile modulus 235 GPa), FAW = 100 g / m ２ , thermosetting epoxy resin, Rc = 40%), and notches were inserted in the same manner as in Example 2. Four prepreg base materials, each measuring 100 mm x 100 mm, were cut out from this notched prepreg and laminated to form a laminate configuration of [+45 / -45 / 90 / +45] to prepare a prepreg base laminate. This prepreg base laminate was placed in the same mold as in Example 2 so that the 90° layer, in which the fiber orientation direction is perpendicular to the rib groove, was the second layer from the upper mold side, and molded under the same conditions as in Example 2 to obtain a fiber-reinforced plastic.

[0219] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm x plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 1.5 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 0.2 mm, and the thickness t of the plate-like portion was 0.3 mm, resulting in a w / t ratio of 5. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0220] As in Example 2, <Appearance quality: inspection of rib streaks on the design surface> and <Inspection of resin-richness on the cross section of the protrusion> were carried out. In <Appearance quality: inspection of rib streaks on the design surface>, there was no distortion in the reflected light of the fluorescent lamp at any angle, even without painting.

[0221] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0222] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was 60%. Furthermore, in <Inspection of resin richness on cross section of protrusion>, the resin richness was 3% or more and less than 5%.

[0223] Example 17 Eleven prepreg base sheets, each measuring 100 mm x 100 mm, were cut out from the prepreg with slits inserted in the same manner as in Example 2, and the laminated structure was [+45 / -45]. ５ The laminate was then laminated so that the thickness was [+45]. Underneath this, a woven fabric prepreg (#CO6343B carbon fiber, tensile strength 3,530 MPa, tensile modulus 230 GPa, basis weight 198 g / m) manufactured by Toray Industries, Inc. was used as a design surface substrate. ２ Using the same mold as in Example 7, the fabric prepreg was placed on the lower mold side, and press molding was carried out under the same conditions as in Example 1 except that the lower mold temperature was 150°C, the upper mold temperature was 140°C, the preheating time from placing the prepreg base laminate in the mold until pressurization was 10 seconds, and the pressing force was 6 MPa, to obtain a fiber-reinforced plastic.

[0224] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 8.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 2.0 mm, the thickness t of the plate-like portion was 1.2 mm, and w / t was 7. Furthermore, the total thickness t' of the unidirectional layer located closer to the protrusion than the non-unidirectional layer was 1.0 mm, and w / t' was 8.

[0225] When inspected in the same manner as in Example 1, there was no distortion in the reflected light of the fluorescent lamp at any angle, even without any coating.

[0226] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Blurred Design Surface>, no blurring was observed on the entire design surface at any angle.

[0227] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 56%.

[0228] <Appearance quality: inspection of bubbles on the woven fabric design surface> was carried out, and the number of bubbles that could be visually confirmed was two.

[0229] Furthermore, when the thickness of the woven fabric in the cross section of the molded article was measured, the thickness was 0.23 mm.

[0230] Comparative Example 1 Four prepreg base sheets each measuring 100 mm x 100 mm were cut out from a prepreg with slits inserted in the same manner as in Example 2, and the laminated structure was [+45 / -45] ２ This prepreg base laminate was press-molded under the same conditions as in Example 1 to obtain a fiber-reinforced plastic, except that an upper mold was used in which the rib grooves for forming the protrusions (ribs) had a straight line shape with a maximum width of 9.0 mm, a tip width of 1.0 mm, a curvature radius of 2.0 mm, a depth of 3 mm, and a length of 60 mm.

[0231] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 9.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 2.0 mm, the thickness t of the plate-like portion was 0.3 mm, and w / t was 30. Furthermore, because the plate-like portion was entirely composed of unidirectional layers, t = t' for this molded product.

[0232] When inspected in the same manner as in Example 1, distortion of reflected light was observed at all angles both before and after painting, and dents were also observed.

[0233] Furthermore, when inspected using the method described in <Appearance Quality: Inspection of Design Surface Blur>, partial blurring was observed only at certain angles, but it was possible to hide the blurring by painting.

[0234] Furthermore, when measured by the method described in <Measurement of fiber volume fraction (Vf)>, Vf was found to be 60%.

[0235] Comparative Example 2 Two prepreg substrates each measuring 100 mm x 100 mm were cut out from a prepreg with slits inserted in the same manner as in Example 2, and these were laminated so as to form a laminate structure of [+45 / -45]. Furthermore, a woven prepreg (#CO6343B carbon fiber tensile strength 3,530 MPa, tensile modulus 230 GPa, basis weight 198 g / m) manufactured by Toray Industries, Inc. was placed underneath as a design surface substrate. ２ ) was placed on the lower mold side, and this prepreg base laminate was press-molded using the same mold and conditions as in Comparative Example 1 so that the woven fabric prepreg was on the lower mold side, to obtain a fiber-reinforced plastic.

[0236] The obtained fiber-reinforced plastic had a straight rib in the center of a 100 mm x 100 mm plate-like portion, and external observation of the rib revealed that the carbon fiber was filled up to the tip of the rib. Measurements were performed in the same manner as in Example 1, and the maximum width w of the protrusion was 9.0 mm, the radius of curvature R of the curved surface formed by the protrusion and the plate-like portion was 2.0 mm, the thickness t of the plate-like portion was 0.3 mm, and w / t was 30. Furthermore, the minimum total thickness t' of the unidirectional layer located closer to the protrusion than the non-unidirectional layer was 0.1 mm, and w / t' was 90.

[0237] When inspected in the same manner as in Example 1, it was found that the reflected light was distorted at all angles both before and after painting, and that a larger dent than in the molded product of Comparative Example 1 was also observed.

[0238] Furthermore, when inspected by the method described in <Appearance Quality: Inspection of Smudges on Design Surface>, smudges were observed on the entire design surface, and it was found that the product was not suitable for painting.

[0239] Furthermore, when measured by the method described in <Measurement of fiber volume content (Vf)>, Vf was found to be 63%.

[0240]

[0241]

[0242]

[0243]

[0244] The fiber-reinforced plastic of the present invention can be preferably used for components that require strength, rigidity, and light weight, or components with complex shapes that require shape-following properties between other components. It can be used in particular for components with the aforementioned strong requirements, such as bicycle cranks and frames, sports components such as golf club shafts and heads, structural components, exterior panels, and interior materials for automobile doors, seats, members, modules, and frames, and machine parts such as robot arms. It can also be preferably used for structural components and exterior panels for medical devices and information and communication devices.

[0245] 1: Maximum width of protrusion 2: Width of cross section of protrusion 3: Height of protrusion 4: Cut-inserted prepreg 5: Fiber orientation direction 6: Fiber perpendicular direction 7: Intermittent cut 8: Continuous cut 9: Intermittent diagonal cut (positive angle to fiber direction) 10: Intermittent diagonal cut (negative angle to fiber direction) 11: Row of intermittent cuts 20: Length direction of protrusion 21: Width direction of protrusion 22: Cross section of protrusion 23: Longitudinal section of protrusion 100: Plate-like portion 101: Thickness (t) of plate-like portion 102: Non-unidirectional layer 103: Total thickness (t') of unidirectional layer 104: Woven fabric 105: Warp or weft thread of woven fabric 106: Weft or warp thread of woven fabric 107: Thickness of mesh of woven fabric 108: Step between warp and weft threads 109: Air bubble 200: Protrusion 201: Curved surface formed by plate-like portion and protrusion 202: Maximum width (w) of protrusion 203: Height of protrusion 300: Reinforced fiber 400: Surface layer opposite to the surface having the protrusion 401: Reinforced fiber 402: Distortion 500: Recess 600: "Unfilled" area