Fiber-reinforced plastic and method for manufacturing fiber-reinforced plastic

Abstract

The present invention relates to a fiber-reinforced plastic in which, as at least one surface layer in the thickness direction, there is a layer containing reinforcing fibers that form discontinuous reinforcing fiber bundles in a random stack or discontinuous reinforcing fiber bundles aligned in one direction, with a portion of the discontinuous reinforcing fiber bundles being in contact with both a thermosetting resin and a thermoplastic resin, the thermoplastic resin being exposed to at least a portion of the surface of the surface layer.

Description

Technical Field

[0001] This invention relates to fiber-reinforced plastics and methods for manufacturing fiber-reinforced plastics. Background Technology

[0002] Fiber-reinforced plastics, made by combining thermosetting or thermoplastic resins as a matrix with reinforcing fibers such as carbon fiber or glass fiber, are not only lightweight but also possess excellent mechanical properties such as strength and rigidity, as well as heat resistance and corrosion resistance. Therefore, fiber-reinforced plastics are used in numerous fields, including aerospace, automotive, railway, shipbuilding, civil engineering, and sporting goods.

[0003] However, fiber-reinforced plastics are not suitable for manufacturing parts or structures with complex shapes using a single molding process. In the aforementioned applications, it is necessary to manufacture parts formed from fiber-reinforced plastics, which are then integrated with similar or dissimilar parts. As a method for integrating fiber-reinforced plastics with similar or dissimilar parts, mechanical joining methods such as bolts, rivets, and screws, or joining methods using adhesives can be employed.

[0004] In mechanical bonding methods, the pre-processing of the bonding parts, such as drilling, is required, which increases manufacturing time and costs. Furthermore, drilling can reduce material strength. In adhesive bonding methods, the process involves adhesive preparation, application, and curing, further extending manufacturing time and compromising the reliability of bond strength.

[0005] Fiber-reinforced plastics using thermoplastic resin as the matrix resin can be joined with other components that use thermoplastic resin by welding, thus simplifying the process relatively easily. For example, Patent Document 1 discloses a laminate made of fiber-reinforced resin in which thermosetting resin layers and thermoplastic resin layers form concave-convex boundary surfaces inside the reinforcing fiber bundles. It describes how the thermoplastic resin layers of this laminate can be joined with other components by welding, thereby obtaining a bonded body with excellent bonding strength.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2004 / 060658. Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] In the laminated body using thermoplastic resin described in Patent Document 1, the interface between the thermosetting resin and the thermoplastic resin is located inside the reinforcing fiber bundle. Therefore, the reinforcing fibers bear the load and suppress interfacial delamination between the thermosetting and thermoplastic resins, while achieving excellent bonding strength when fused with other components. However, this laminated body may not be suitable for applications where shape conformance takes precedence over strength.

[0011] The object of the present invention is to provide a fiber-reinforced plastic that can be joined by means of a thermoplastic resin and by welding with other components, exhibiting excellent bonding strength with other components and excellent shape conformability.

[0012] Methods for solving problems

[0013] To address the aforementioned issues, the present invention has the following configuration.

[0014] <1> Fiber-reinforced plastic, wherein at least one surface layer in the thickness direction has a layer comprising reinforcing fibers and a matrix integrally formed of a thermosetting resin and a thermoplastic resin.

[0015] The reinforcing fibers form discontinuous reinforcing fiber bundles that are randomly stacked, or form discontinuous reinforcing fiber bundles that are arranged in a unidirectional direction.

[0016] A portion of the discontinuous reinforcing fiber bundle is in contact with both the thermosetting resin and the thermoplastic resin.

[0017] The thermoplastic resin is exposed on at least a portion of the surface of the surface layer.

[0018] <2> according to <1> The fiber-reinforced plastic, wherein in the surface layer, a region with the thermosetting resin as the main component and a region with the thermoplastic resin as the main component form an interface.

[0019] <3> according to <1> or <2> The fiber-reinforced plastic, wherein the surface layer has a region in which the thermoplastic resin is continuous in the thickness direction from the surface.

[0020] Within the region, the maximum thickness of the portion where the thermoplastic resin meets the discontinuous reinforcing fiber bundle is 10 μm or more.

[0021] <4> according to <1> ~ <3> The fiber-reinforced plastic according to any one of the following methods, wherein the content of the reinforcing fibers in the surface layer is more than 15% by volume and less than 70% by volume.

[0022] <5> according to <1> ~ <4> The fiber-reinforced plastic according to any one of the following methods, wherein, in the surface layer, the average fiber length of the reinforcing fibers is in the range of 5 mm to 100 mm.

[0023] <6> according to <1> ~ <5> The fiber-reinforced plastic according to any one of the following methods, wherein, in the surface layer, the reinforcing fiber is at least one selected from the group consisting of carbon fiber and glass fiber.

[0024] <7> according to <1> ~ <6> In any one of the fiber-reinforced plastics, the ratio of voids in the surface layer that connect to the ends of the discontinuous reinforcing fiber bundles along their length direction is less than 5% by area.

[0025] <8> according to <1> ~ <7> The fiber-reinforced plastic according to any one of the following methods, wherein the long side impregnation distance in the surface layer is 20 μm or more.

[0026] <9> according to <1> ~ <8> The fiber-reinforced plastic according to any one of the following, wherein the thermoplastic resin is present between the discontinuous reinforcing fiber bundles in the surface layer.

[0027] <10> according to <9> The fiber-reinforced plastic, wherein the thermoplastic resin occupies the space between any adjacent discontinuous fiber reinforcement bundles.

[0028] <11> according to <1> ~ <10> The fiber-reinforced plastic according to any one of the following descriptions, wherein the discontinuous reinforcing fiber bundles, the thermoplastic resin, and the thermosetting resin are present in two surface layers in the thickness direction.

[0029] The thermoplastic resin is exposed on the surfaces of the two surface layers.

[0030] <12> according to <1> ~ <11> In any one of the fiber-reinforced plastics, at least a portion of the discontinuous reinforcing fiber bundles constituting the fiber-reinforced plastic are oriented in an out-of-plane direction.

[0031] <13> The manufacturing method of fiber-reinforced plastics, which is <1> ~ <12> The method for manufacturing fiber-reinforced plastics as described in any one of the following statements,

[0032] The manufacturing method includes:

[0033] Step 1 involves impregnating the reinforcing fiber bundles with thermosetting resin;

[0034] Step 2 involves impregnating the reinforcing fiber bundles with thermoplastic resin;

[0035] Step 3 involves cutting the reinforcing fiber bundles to create discontinuous reinforcing fiber bundles;

[0036] Step 4 involves stacking the required number of sheets of the fiber-reinforced plastic substrate with the thermoplastic resin exposed on at least one surface in the thickness direction; and

[0037] Step 5 involves molding the fiber-reinforced plastic through heating and pressurization.

[0038] The procedure 5 is performed after the procedures 1 to 4, or simultaneously with the procedure 2 after the procedures 1, 3 and 4, or simultaneously with the procedure 1 after the procedures 2, 3 and 4.

[0039] <14> according to <13> The method for manufacturing the fiber-reinforced plastic includes: step 6, in which the discontinuous reinforcing fiber bundles flow in the exposed surface layer of the thermoplastic resin in such a way that the ends of the bundles in the longitudinal direction are in contact with the thermosetting resin or the thermoplastic resin.

[0040] <15> according to <13> or <14> In the method for manufacturing fiber-reinforced plastics, in step 6, at least a portion of the discontinuous reinforcing fiber bundles is in contact with both the thermosetting resin and the thermoplastic resin in the exposed surface layer of the thermoplastic resin.

[0041] Furthermore, at least one of the reinforcing fibers constituting the reinforcing fiber bundle flows in a manner in which the thermoplastic resin is continuously connected to the reinforcing fiber in the length direction from its end in the length direction.

[0042] The effects of the invention

[0043] The fiber-reinforced plastic of the present invention allows for bonding with other components via fusion welding by exposing at least a portion of the thermoplastic resin on the surface layer. Furthermore, since a portion of the discontinuous reinforcing fiber bundle is in contact with both the thermoplastic and thermosetting resins, delamination at the interface between the thermosetting and thermoplastic resins is less likely to occur. Moreover, by making the reinforcing fibers discontinuous reinforcing fiber bundles, excellent shape conformability is achieved, making it particularly useful in applications where both strength and shape conformability must be considered. Attached Figure Description

[0044] [ Figure 1 ] Figure 1 This is a top view of one embodiment of the fiber-reinforced plastic of the present invention.

[0045] [ Figure 2 ] Figure 2 This is a cross-sectional schematic diagram of one embodiment of the fiber-reinforced plastic of the present invention.

[0046] [ Figure 3 ] Figure 3 This is a schematic diagram of one embodiment of a prepreg blank that can be used in manufacturing the fiber-reinforced plastic of the present invention.

[0047] [ Figure 4 ] Figure 4This is a cross-sectional schematic diagram of one embodiment of the fiber-reinforced plastic of the present invention, which helps to explain the method for determining the maximum impregnation distance.

[0048] [ Figure 5 ] Figure 5 This is a cross-sectional schematic diagram of one embodiment of the fiber-reinforced plastic of the present invention.

[0049] [ Figure 6 ] Figure 6 This is a cross-sectional schematic diagram of one embodiment of the fiber-reinforced plastic of the present invention.

[0050] [ Figure 7 ] Figure 7 This is a cross-sectional schematic diagram of one embodiment of the fiber-reinforced plastic of the present invention, which helps to explain the method for measuring the average roughness height Rc.

[0051] [ Figure 8 ] Figure 8 This is a cross-sectional schematic diagram of one embodiment of the fiber-reinforced plastic of the present invention, which helps to explain the method for measuring the long side impregnation distance.

[0052] [ Figure 9 ] Figure 9 As an example of the fiber-reinforced plastic of the present invention, an example of the shape of the fiber-reinforced plastic of the present invention is shown. Detailed Implementation

[0053] [Fiber-reinforced plastics]

[0054] The fiber-reinforced plastic of the present invention will now be described with reference to the accompanying drawings, which are provided for ease of understanding and use and do not limit the invention in any way. It should be noted that, unless otherwise specified, in this specification, the term "cross-section of fiber-reinforced plastic" refers to a cross-section cut parallel to the thickness direction.

[0055] The fiber-reinforced plastic of the present invention comprises, as at least one surface layer in the thickness direction, a layer comprising reinforcing fibers and a matrix integrally formed of a thermosetting resin and a thermoplastic resin.

[0056] The reinforcing fibers form discontinuous reinforcing fiber bundles that are randomly stacked, or form discontinuous reinforcing fiber bundles that are arranged in a unidirectional direction.

[0057] A portion of the discontinuous reinforcing fiber bundle is in contact with both the thermosetting resin and the thermoplastic resin.

[0058] The thermoplastic resin is exposed in at least a portion of the surface of the surface layer.

[0059] The fiber-reinforced plastic of the present invention comprises multiple discontinuous reinforcing fiber bundles as reinforcing fibers. Each discontinuous reinforcing fiber bundle is composed of multiple discontinuous reinforcing fibers. By forming bundles of discontinuous reinforcing fibers, a fiber-reinforced plastic with excellent rigidity can be formed.

[0060] Examples of reinforcing fibers include carbon fiber, glass fiber, metal fiber, aromatic polyamide fiber, polyaramid fiber, alumina fiber, silicon carbide fiber, boron fiber, and basalt fiber. Among these, carbon fiber and glass fiber are preferred reinforcing fibers from the perspectives of elastic modulus, strength, and practicality. These reinforcing fibers can be used alone or in combination of two or more as appropriate.

[0061] Carbon fiber is particularly preferred as a reinforcing fiber due to its low specific gravity, high strength, and high elastic modulus. Commercially available carbon fiber products include, for example, Torayca T800G-24K, Torayca T800S-24K, Torayca T700G-24K, Torayca T700S-24K, Torayca T300-3K, and Torayca T1100G-24K (all manufactured by Toray Industries, Inc.).

[0062] These reinforcing fibers can be surface treated. Surface treatments include metal deposition, treatment using coupling agents, treatment using sizing agents, and additive application.

[0063] In this invention, such as Figure 1 As shown, the discontinuous reinforcing fiber bundles 2 can exist in a randomly stacked state in the surface layer of the fiber-reinforced plastic. As an example of a method for obtaining the surface layer of the fiber-reinforced plastic of the present invention, a method can be described as follows: discontinuous reinforcing fiber bundles obtained by pre-cutting the reinforcing fiber bundles are stacked on a carrier to form an inter-stacked state, and then a substrate impregnated with a thermosetting resin and a thermoplastic resin is molded. As an example of the randomly stacked discontinuous reinforcing fiber bundles in the present invention, sheet molding compound (SMC) can be cited. By randomly stacking the discontinuous reinforcing fiber bundles, excellent shape conformability can be achieved, which is advantageous in applications where shape conformability takes precedence over strength.

[0064] In this invention, the discontinuous reinforcing fiber bundles 2 can be randomly stacked. Here, random stacking of discontinuous reinforcing fiber bundles refers to the situation where, when viewed from above, the average value of a small angle (hereinafter sometimes referred to as "two-dimensional orientation angle") obtained by measuring the orientation direction of the projection of one discontinuous reinforcing fiber bundle randomly selected from fiber bundles having overlapping portions onto a plane is 10 degrees or more and 80 degrees or less. This angle is based on the orientation direction of one discontinuous reinforcing fiber bundle randomly selected from fiber bundles having overlapping portions onto a plane. (In the case where the discontinuous reinforcing fiber bundles do not intersect, it is the angle formed by the intersection of the extensions of the orientation directions of the discontinuous reinforcing fiber bundles in the plane.)

[0065] It should be noted that the orientation direction of the discontinuous reinforcing fiber bundle projected onto the plane is the direction of the straight line formed by connecting the visible length directions of the reinforcing fibers contained in a selected discontinuous reinforcing fiber bundle visible in the top view. The selected reinforcing fiber is arbitrary, but preferably exists near the center of the orthogonal direction of the fibers in the discontinuous reinforcing fiber bundle, and the surrounding reinforcing fibers contained in the same discontinuous reinforcing fiber bundle are approximately parallel to the selected reinforcing fiber. When the extensions of the orientation directions of the discontinuous reinforcing fiber bundles do not intersect, the two-dimensional orientation angle is 0 degrees.

[0066] In this invention, the average value of the two-dimensional orientation angle is more preferably 30 degrees or more and 60 degrees or less, further preferably 40 degrees or more and 50 degrees or less, and the closer it is to 45 degrees as the ideal angle, the more preferred.

[0067] Furthermore, in this invention, the discontinuous reinforcing fiber bundles in the surface layer can be arranged in a unidirectional direction. When the discontinuous reinforcing fiber bundles are arranged in a unidirectional direction, the fiber-reinforced plastic exhibits excellent strength, which is advantageous in applications where strength takes precedence over shape conformity. Here, unidirectional arrangement of the discontinuous reinforcing fiber bundles means that the average value of the two-dimensional orientation angle is 0 degrees or more and less than 10 degrees.

[0068] As an example of a method for obtaining the surface layer of the fiber-reinforced plastic of the present invention, the following method can be cited: cutting at least a portion of the reinforcing fiber bundle contained in a prepreg preform in which the reinforcing fibers are arranged in a unidirectional direction, and molding a substrate to form a discontinuous reinforcing fiber bundle. As an example of such a prepreg preform, examples can be cited... Figure 3 The cut prepreg blank 7 is shown.

[0069] It should be noted that when using the notched prepreg preform 7, the notch inserted into the prepreg preform can be an orthogonal notch relative to the length direction 9 of the reinforcing fiber bundle, or it can be an oblique notch. Additionally, as... Figure 3As shown, the cuts 8 can be oblique pairs at an angle θ = ±α to the length direction 9 of the reinforcing fiber bundle. The shape of the cuts and the shape of the discontinuous reinforcing fiber bundle are not particularly limited. In addition, the cut prepreg blank, besides having a... Figure 3 In addition to the slits that divide the reinforcing fibers along the length direction, there may also be slits parallel to the reinforcing fibers that divide the fiber bundles along the width direction.

[0070] The fiber-reinforced plastic of the present invention comprises: reinforcing fibers comprising discontinuous reinforcing fiber bundles formed in the above-described state, and a matrix integrally formed of a thermosetting resin and a thermoplastic resin. Further, a portion of the discontinuous reinforcing fiber bundles is in contact with both the thermosetting resin and the thermoplastic resin, and thermoplastic resin is present on the surface of the surface layer (hereinafter sometimes referred to as "thermoplastic resin exposure").

[0071] Therefore, it is possible to achieve good welding with the same or different types of parts through thermoplastic resin. Thus, compared with fiber-reinforced plastics composed only of thermosetting resin and reinforcing fibers, the time required for the bonding process can be shortened, and the molding of structural parts can be accelerated.

[0072] Examples of shapes in the fiber-reinforced plastics of the present invention include flat plate shapes with uneven sides, L-shaped components with planar and curved surfaces, rib shapes, or uneven shapes in which at least a portion of the discontinuous reinforcing fiber bundles are oriented in an out-of-plane direction, but are not limited to these.

[0073] It should be noted that the so-called out-of-plane orientation of discontinuous reinforcing fiber bundles refers to a combination in which, when a certain discontinuous reinforcing fiber bundle on the surface is horizontally arranged, there are other discontinuous reinforcing fiber bundles on the same surface whose angle with respect to the horizontal is more than 5 degrees.

[0074] In the fiber-reinforced plastic of the present invention, it is preferable that the average fiber length of the reinforcing fibers constituting the discontinuous reinforcing fiber bundles in the surface layer is 5 mm or more and 100 mm or less. By making the average fiber length 5 mm or more, the reinforcing fibers present at the interface between the thermosetting resin and the thermoplastic resin can adequately bear the load. Therefore, the stress at the interface between the thermosetting resin and the thermoplastic resin is reduced, and as a result, interfacial delamination is suppressed, thus easily exhibiting the effect of improving bond strength. In addition, by making the average fiber length 100 mm or less, the shape conformability during molding of the fiber-reinforced plastic is excellent.

[0075] Furthermore, the fiber lengths of the reinforcing fibers in each of the discontinuous reinforcing fiber bundles comprising the surface layer are preferably substantially the same. By making the fiber lengths substantially the same, the unevenness of the mechanical properties of the fiber-reinforced plastic of the present invention can be suppressed.

[0076] Here, "the fiber length is substantially the same" means that the proportion of reinforcing fibers that are 10 mm or more longer or 10 mm or more shorter than the average fiber length (hereinafter sometimes referred to as "fiber bundle length") of the reinforcing fibers constituting a single discontinuous reinforcing fiber bundle included in the surface layer is less than 10% relative to all the reinforcing fibers included in the discontinuous reinforcing fiber bundle. The closer this proportion of reinforcing fibers is to 0%, the better. However, during the manufacturing process, sometimes substrate misalignment, blade damage, or other issues may occur, making it impossible to cut according to the design, resulting in a proportion of reinforcing fibers greater than 0%.

[0077] Furthermore, more preferably, in the discontinuous reinforcing fiber bundles included in the surface layer, the average fiber length of all discontinuous reinforcing fiber bundles, excluding those connected to the side, is substantially the same. "Substantially the average fiber length of the discontinuous reinforcing fiber bundles is substantially the same" means that, in the discontinuous reinforcing fiber bundles included in the surface layer, the proportion of discontinuous fiber reinforcing fiber bundles with a fiber length that is 10 mm or more longer or 10 mm or more shorter than the average fiber bundle length is 10% or less. The closer this proportion of discontinuous reinforcing fiber bundles is to 0%, the more preferred. However, during the manufacturing process, sometimes substrate misalignment, blade damage, etc., may occur, making it impossible to cut according to the design, resulting in the proportion of discontinuous reinforcing fiber bundles being greater than 0%.

[0078] It should be noted that in the fiber-reinforced plastic of the present invention, the exposed surface of the thermoplastic resin can be one side or both sides. That is, in the fiber-reinforced plastic of the present invention, the surface layer on both sides in the thickness direction has a layer comprising discontinuous reinforcing fiber bundles, thermoplastic resin and thermosetting resin, and the thermoplastic resin can be exposed on both sides.

[0079] Hereinafter, in the fiber-reinforced plastic of the present invention, the surface containing the exposed portion of the thermoplastic resin contained in the surface layer will be referred to as the "joining surface". It should be noted that when the thermoplastic resin is exposed on both sides of the fiber-reinforced plastic, the two sides are called the "joining surface".

[0080] There is no particular limitation on the proportion of thermoplastic resin in the surface of the bonding surface; the thermoplastic resin may be exposed on the entire surface of the bonding surface or only on a portion thereof. The greater the proportion of thermoplastic resin exposed on the bonding surface, the larger the area that can be used for bonding, and thus an increase in bonding strength can be expected. The proportion of thermoplastic resin in the surface of the bonding surface is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more.

[0081] Furthermore, in the fiber-reinforced plastic of the present invention, a portion of the discontinuous reinforcing fiber bundle is bonded to both the thermosetting resin and the thermoplastic resin. Due to this structure, when the bonding surface of the fiber-reinforced plastic of the present invention is bonded to the same or different materials to bear a load, the firmly attached reinforcing fibers in the discontinuous reinforcing fiber bundle, existing across the interface between the thermosetting resin and the thermoplastic resin, bear the load. Therefore, the load applied to the interface between the thermosetting resin and the thermoplastic resin is reduced, inhibiting delamination, and thus, the apparent interfacial strength of the thermosetting resin and the thermoplastic resin is improved.

[0082] Furthermore, by bonding the reinforcing fibers with both thermosetting and thermoplastic resins, the interface shape between the thermosetting and thermoplastic resins becomes more complex. As a result, the contact area between the thermosetting and thermoplastic resins increases, and hooking occurs due to the unevenness, which further enhances the apparent interfacial strength.

[0083] The fiber-reinforced plastic of the present invention can take any form, such as forming a mixed layer at the interface between the thermosetting resin and the thermoplastic resin. As a more preferred form, it is preferably as follows: Figure 2 As shown, in the surface layer, an interface 6 is formed between a region primarily composed of thermosetting resin 5 and a region primarily composed of thermoplastic resin 4. By forming such an interface structure, it is easy to confirm the formation of a continuous region of thermoplastic resin (described later) in the fiber-reinforced plastic of the present invention, extending from the surface in the thickness direction.

[0084] In the surface layer of the fiber-reinforced plastic of the present invention, thermoplastic resin is preferably present between discontinuous reinforcing fiber bundles. By forming this configuration, a structure with a complex interface shape between the thermosetting resin and the thermoplastic resin can be adopted, and improved bonding strength can be expected. Such a structure can be confirmed, for example, by cutting a cross-section parallel to the thickness direction with the length direction of a discontinuous reinforcing fiber bundle in the surface layer as a reference.

[0085] Here, for the discontinuous reinforcing fiber bundles with thermoplastic resin between them, Figure 2 Taking a cross-section as an example, in a cross-section cut along the thickness direction of the fiber-reinforced plastic 1, starting from the end of a discontinuous reinforcing fiber bundle 2 along its length direction, the ends or sides of other discontinuous reinforcing fiber bundles 2 along their length directions are connected by a straight line in a manner that minimizes the distance between the fiber bundles without passing through the reinforcing fibers. Although this straight line passes through the thermoplastic resin 4, thermosetting resin 5, and gaps present between the fiber bundles, it is possible to draw a straight line whose total length passing through the thermoplastic resin 4 is more than 30% of the total length of the straight line, indicating that there is thermoplastic resin 4 between the discontinuous reinforcing fiber bundles 2.

[0086] Among the straight lines drawn between discontinuous reinforcing fiber bundles, the proportion of straight lines in which the total length of the thermoplastic resin is 30% or more, and the proportion of straight lines in which the total length of the thermoplastic resin is 50% or more, is preferably 30% or more, more preferably 50% or more, and even more preferably 80% or more.

[0087] Furthermore, in the fiber-reinforced plastic of the present invention, it is preferable that the thermoplastic resin occupies the space between any adjacent discontinuous reinforcing fiber bundles. By forming such a configuration, the thermoplastic resin is sufficiently impregnated between the discontinuous reinforcing fiber bundles, resulting in a structure with a more complex interface between the thermosetting resin and the thermoplastic resin, and an improvement in bond strength can be expected.

[0088] Here, "the thermoplastic resin occupies the space between any adjacent discontinuous reinforcing fiber bundles" means that a straight line can be drawn between the discontinuous reinforcing fiber bundles in which the total length of the thermoplastic resin 4 passes through is 100%. More preferably, a straight line can be drawn between multiple discontinuous reinforcing fiber bundles in which the total length of the thermoplastic resin passes through is 100%.

[0089] In the fiber-reinforced plastic of the present invention, the volume content of the reinforcing fibers in the surface layer is preferably 15% by volume or more and 70% by volume or less. When the volume content is 15% by volume or more, the amount of thermosetting resin and thermoplastic resin is not excessive compared to discontinuous reinforcing fiber bundles, and the specific strength and specific modulus of elasticity tend to be superior. In addition, when the volume content is 70% by volume or less, poor impregnation of thermosetting resin and thermoplastic resin is less likely to occur, and the porosity of the obtained fiber-reinforced plastic is easily reduced. The volume content is more preferably 20% by volume or more and 70% by volume or less, and even more preferably 25% by volume or more and 70% by volume or less.

[0090] Here, the volume content of reinforcing fibers in the surface layer refers to the volume content in the areas where reinforcing fibers are present. The measurement and calculation exclude the surface and interlayer areas of the fiber-reinforced plastic that do not contain reinforcing fibers or have a small number of reinforcing fibers while resin occupies the majority of the area. For the measurement, multiple locations (preferably five or more locations) are measured, the volume content of reinforcing fibers in each location is calculated, and the average value is taken as the volume content of reinforcing fibers in the surface layer.

[0091] In the case of the fiber-reinforced plastic of the present invention, the surface layer has a region in which the thermoplastic resin is continuous in the thickness direction from the surface. From the viewpoint that the discontinuous reinforcing fiber bundles and the thermoplastic resin can easily connect, the reinforcing fibers can easily bear the load acting on the joint surface when joined, and the joint strength is improved, the thickness of the portion in which the thermoplastic resin and the discontinuous reinforcing fiber bundles connect in this region is preferably at most 10 μm, more preferably at most 20 μm, and even more preferably at most 50 μm (hereinafter, this thickness is sometimes referred to as "maximum impregnation distance").

[0092] Here, the continuous region of thermoplastic resin in the thickness direction from the surface refers to, for example, Figure 4 As shown, when observing the cross-section in the thickness direction, the region with the boundary of thermoplastic resin is continuous within the fiber-reinforced plastic, excluding, for example... Figure 5 The area shown is a region that is discontinuous with thermoplastic resin 4, as seen at the boundary of thermoplastic resin 4' when observing the cross-section in the thickness direction.

[0093] In addition, the maximum immersion distance refers to: such as Figure 4 As shown, a reference line 11 is drawn parallel to the joint surface, starting from the point where the continuous thermoplastic resin and reinforcing fiber bundle initially meet in the thickness direction. The intersection of the vertical baseline 12 drawn from the reference line 11 and the boundary line where the continuous area of ​​thermoplastic resin in the thickness direction from the surface meets other constituent elements (thermosetting resin, reinforcing fibers, or voids) is defined. Figure 4 The distance from the farthest intersection point of the reference line 11 among the measurement points (represented by black dots on the vertical baseline 12).

[0094] In this invention, when discontinuous reinforcing fiber bundles are randomly packed, in a cross-section in any direction, and in a cross-section at a 45-degree angle relative to the arrangement direction of the discontinuous reinforcing fiber bundles when the discontinuous reinforcing fiber bundles are arranged in a unidirectional manner, the average roughness height Rc of the cross-sectional curve described later, as defined by JIS B0601 (2001), is preferably 3.5 μm or more, more preferably 10 μm or more. This structure is considered to be formed by the flow of discontinuous reinforcing fiber bundles and thermosetting / thermoplastic resin.

[0095] By achieving an average roughness height Rc of 3.5 μm or more, the contact area between the thermoplastic and thermosetting resins is further increased, and the hooks formed by the unevenness become more complex, thus expecting a further improvement in the apparent interfacial strength. Furthermore, the discontinuous reinforcing fibers present at the interface form chemical and / or physical bonds with both the thermosetting and thermoplastic resins, further enhancing the interfacial strength with these resins.

[0096] Known methods can be used to determine the roughness average height Rc. For example, methods include determining it using cross-sectional images of fiber-reinforced plastics obtained by X-ray CT; determining it using elemental analysis mapping images obtained by energy dispersive X-ray spectrometer (EDS); and determining it using cross-sectional observation images obtained by optical microscope, scanning electron microscope (SEM), or transmission electron microscope (TEM).

[0097] In image observation, thermosetting and / or thermoplastic resins may be stained to adjust contrast. In patterns obtained by any of the above methods, the average roughness height Rc of the cross-sectional curve is measured for a 500 μm square area.

[0098] use Figure 6 and Figure 7 This represents an example of a method for determining the average roughness height Rc. Figure 6 This is a schematic cross-sectional view of the fiber-reinforced plastic of the present invention. Figure 6 In the interface 6 where the thermosetting resin 5 and the thermoplastic resin 4 are in contact, the average roughness height Rc is measured in the region having a discontinuous reinforcing fiber bundle 2 containing discontinuous reinforcing fibers 3 that are in contact with both the thermosetting resin 5 and the thermoplastic resin 4.

[0099] Figure 7 for Figure 6 A magnified view of the area used for measuring the average roughness height Rc. Figure 7 In this process, thermosetting resin 5 and thermoplastic resin 4 are bonded at interface 6. Additionally, at interface 6, there are multiple discontinuous reinforcing fibers 3 contained within a discontinuous reinforcing fiber bundle. Starting from reference line 11, a vertical baseline 12 is drawn from the thermoplastic resin 4, passing towards the thermosetting resin 5, at 5 μm intervals. The measurement point 14 where the vertical baseline 12 drawn from reference line 11 initially intersects with the thermosetting resin 5 is plotted, and the line connecting these plotted points is used as the cross-sectional curve. The obtained cross-sectional curve is filtered according to JIS B0601 (2001), and the average roughness height Rc of the cross-sectional curve is calculated.

[0100] The surface layer of the fiber-reinforced plastic of the present invention preferably has a unit area weight of 10 g / m². 2 The above, more preferably 20g / m 2 The above. The unit area weight of thermoplastic resin is 10 g / m². 2 The above allows for a sufficient thickness to achieve excellent bonding strength.

[0101] There is no particular limit to the upper limit of the unit area weight of thermoplastic resin in the surface layer, but since the content of thermoplastic resin is not excessive compared to the content of reinforcing fibers, fiber-reinforced plastics with excellent specific strength and specific modulus of elasticity can be obtained. Therefore, 500 g / m² is preferred. 2 Below. Here, the weight per unit area of ​​thermoplastic resin refers to the weight per 1m³ of fiber-reinforced plastic. 2 The mass (g) of thermoplastic resin contained in the surface layer.

[0102] The preferred amount of reinforcing fibers per unit area in the surface layer of the fiber-reinforced plastic of the present invention is 30 g / m². 2 Above 2,000g / m 2 The following is a description of the reinforcing fiber content: 30g / m². 2 This reduces the number of substrate sheets required to achieve the specified thickness during fiber-reinforced plastic molding, simplifying the process. Furthermore, the reinforcing fiber content is 2,000 g / m². 2 In the following cases, the drape of fiber-reinforced plastic precursors is easily improved.

[0103] Furthermore, in the surface layer of the fiber-reinforced plastic of the present invention, the ratio of voids connecting to the ends of discontinuous reinforcing fiber bundles along the longitudinal direction is preferably 5% or less. By adopting this configuration, stress concentration at the ends of discontinuous reinforcing fiber bundles along the longitudinal direction can be prevented, and fiber-reinforced plastics with excellent molding quality and strength can be obtained.

[0104] The determination of the percentage of voids connecting to the ends of discontinuous reinforcing fiber bundles along their length direction is performed as follows. First, when the discontinuous reinforcing fiber bundles are randomly packed, multiple cross-sectional images in arbitrary directions are acquired; when the discontinuous reinforcing fiber bundles are arranged in a unidirectional direction, multiple cross-sectional images in the thickness direction (i.e., the direction parallel to the arrangement direction) are acquired. Next, in each acquired image, the area of ​​the voids connecting to the ends of the discontinuous reinforcing fiber bundles along their length direction and the area corresponding to the surface layer are measured. Finally, in all images, the total area of ​​the measured voids is divided by the total area corresponding to the surface layer, and then multiplied by 100. The resulting value is taken as the percentage (%) of voids connecting to the ends of the discontinuous reinforcing fiber bundles along their length direction. The percentage of voids connecting to the ends of the discontinuous reinforcing fiber bundles along their length direction is more preferably 3% or less, and more preferably 1% or less.

[0105] It should be noted that cross-sectional images of fiber-reinforced plastics can be obtained by cutting along the thickness direction at any location, embedding and grinding them, and then observing them using an optical microscope.

[0106] Furthermore, in the surface layer of the fiber-reinforced plastic of the present invention, it is preferable that the reinforcing fibers and the thermoplastic resin are continuously connected in the longitudinal direction of the fiber from the end of the reinforcing fiber (hereinafter, the length of this connected portion is sometimes referred to as the "long side impregnation distance"). By forming this configuration, a structure with a more complex interface shape between the thermosetting resin and the thermoplastic resin passing through the reinforcing fibers can be formed, and an improvement in bonding strength is expected. It is believed that this structure is formed by the flow of discontinuous reinforcing fiber bundles and thermosetting and thermoplastic resins.

[0107] The length of time in which the reinforcing fiber and thermoplastic resin are continuously joined along the length of the fiber from the end of the reinforcing fiber in the longitudinal direction refers to... Figure 8 As shown, a reference line 15 is drawn along the side of any discontinuous reinforcing fiber 3 that is connected to the thermoplastic resin in the longitudinal direction, starting from that end. The reference line extends to the intersection of the boundary line where the thermoplastic resin 4 and the thermosetting resin 5 or the void initially meet. Figure 8 The distance from the reference line 15 to the measurement point 16 (represented by a black dot).

[0108] More specifically, the determination of the long-side impregnation distance is performed as follows: First, five or more discontinuous reinforcing fiber bundles located near the surface are randomly selected, and cross-sectional images in the thickness direction are obtained parallel to the orientation direction of the reinforcing fibers constituting the discontinuous reinforcing fiber bundles. Next, in each obtained image, taking the reinforcing fiber that is in contact with both thermosetting and thermoplastic resins as the object, a reference line is drawn along the length direction of the reinforcing fiber, starting from the end of the reinforcing fiber in contact with the thermoplastic resin. The point where it initially intersects with the thermosetting resin or void is selected, and the distance from the end is measured. The average of all measured values ​​is taken as the long-side impregnation distance. It should be noted that when measuring the long-side impregnation distance, when cutting parallel to the thickness direction of the fiber-reinforced plastic, the side of the reinforcing fiber closest to the surface of the thermoplastic resin exposed in the thickness direction is excluded from the measurement object.

[0109] In the fiber-reinforced plastic of the present invention, from the viewpoint that the reinforcing fibers can easily bear the load acting on the joint surface and the joint strength is further improved, the impregnation distance of the long side is preferably 20 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more.

[0110] The fiber-reinforced plastic of the present invention may consist only of the aforementioned surface layer, or it may have a layered structure containing layers other than the surface layer. By having such a layered structure, the thickness of the fiber-reinforced plastic of the present invention can be increased, enabling its application in structural components. The layers other than the surface layer may be layers comprising continuous or discontinuous reinforcing fibers and a matrix composed of thermosetting resins and / or thermoplastic resins. There are no particular limitations on the type of layers constituting such a layered structure.

[0111] In addition, in the fiber-reinforced plastic of the present invention, there may be a resin layer composed of thermosetting resin and / or thermoplastic resin without reinforcing fibers.

[0112] In the fiber-reinforced plastic of the present invention, other components (hereinafter sometimes referred to as "bonded materials") can be bonded to the thermoplastic resin present on the bonding surface of the fiber-reinforced plastic by a certain heating means, thereby integrating (welding) with the fiber-reinforced plastic through the thermoplastic resin.

[0113] Examples of components that can be bonded include those made of thermosetting resins and / or thermoplastic resins, and those made of metal. Additionally, components made of the fiber-reinforced plastic of this invention can also be used as bonded materials. There are no particular limitations on the method of integrating the fiber-reinforced plastic of this invention with the bonded material; examples include thermal welding, vibration welding, ultrasonic welding, laser welding, resistance welding, induction welding, insert injection molding, and matrix injection molding.

[0114] In the fiber-reinforced plastics of the present invention, the thermosetting resin included in the matrix includes, for example, unsaturated polyester resins, vinyl ester resins, epoxy resins, phenolic resins, urea resins, melamine resins, thermosetting polyimide resins, cyanate ester resins, bismaleimide resins, benzoxazine resins, copolymers thereof, modified forms thereof, and resins blended with at least two of these. To improve impact resistance, an elastomer or rubber component may be added to the thermosetting resin. Furthermore, to control curing, the fiber-reinforced plastics of the present invention may contain a curing agent and a curing accelerator.

[0115] From the perspective of practicality and versatility, epoxy resin, phenolic resin, unsaturated polyester resin, vinyl ester resin, thermosetting polyimide resin, cyanate ester resin, bismaleimide resin, and benzoxazine resin are preferred, with epoxy resin being more preferred.

[0116] Epoxy resins are preferred due to their excellent mechanical properties, heat resistance, and adhesion to reinforcing fibers. Examples of main agents in epoxy resins include bisphenol-type epoxy resins such as bisphenol A, bisphenol F, bisphenol AD, and bisphenol S; brominated epoxy resins such as tetrabromobisphenol A diglycidyl ether; epoxy resins with a biphenyl backbone; epoxy resins with a naphthalene backbone; epoxy resins with a dicyclopentadiene backbone; Novolac-type epoxy resins such as phenol and cresol; and N,N,O-triglycidyl-m-aminophenol. Glycidylamine type epoxy resins such as hydroglyceryl-p-aminophenol, N,N,O-triglycidyl-4-amino-3-methylphenol, N,N,N',N'-tetraglycidyl-4,4'-methylenediphenylamine, N,N,N',N'-tetraglycidyl-2,2'-diethyl-4,4'-methylenediphenylamine, N,N,N',N'-tetraglycidyl-m-phenylenediamine, N,N-diglycidylaniline, and N,N-diglycidyl-o-toluidine, resorcinol diglycidyl ether, and triglycidyl isocyanurate, etc.

[0117] Furthermore, in the fiber-reinforced plastics of the present invention, the thermoplastic resin included as the matrix can be, for example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, polyethylene naphthalate, and liquid crystal polyester; polyolefins such as polyethylene, polypropylene, and polybutene; polyamides such as polyamide 6 and polyamide 66; polyketones, polyetherketones, polyetheretherketones, polyetheretherketones, and polyetherketoneketones; polystyrene resins; urethane resins; polyoxymethylene; polycarbonate; polymethyl methacrylate; polyvinyl chloride; polyphenylene sulfide; polyphenylene ether; modified polyphenylene ether; polyimide; polyamide-imide; polyetherimide; polysulfone; modified polysulfone; polyethersulfone; polyarylate; polyether nitrile; phenolic resin; phenoxy resin; etc. Additionally, the thermoplastic resin can be a copolymer or modifier of the above resins, or a resin formed by blending two or more of the above resins.

[0118] From a heat resistance perspective, it is preferable that the thermoplastic resin contains 60% by mass or more of one or more of polyaryletherketone, polyphenylene sulfide, and polyetherimide. To improve impact resistance, elastomers or rubber components can be added to the thermoplastic resin.

[0119] Furthermore, depending on the intended use, thermosetting and thermoplastic resins may appropriately contain other fillers and additives without prejudice to the purpose of this invention. Thermosetting and thermoplastic resins may contain, for example, inorganic fillers, flame retardants, conductivity enhancers, nucleating agents, ultraviolet absorbers, antioxidants, vibration damping agents, antibacterial agents, insect repellents, deodorizing agents, anti-coloring agents, heat stabilizers, mold release agents, antistatic agents, plasticizers, lubricants, colorants, pigments, dyes, foaming agents, defoaming agents, coupling agents, etc.

[0120] The fiber-reinforced plastic of the present invention has no particular limitation on its use, but is preferably used for computer applications such as aircraft structural components, windmill blades, automobile outer panels and IC trays, and laptop computer casings, and even more preferably for sports applications such as golf clubs and tennis rackets.

[0121] [Manufacturing method of fiber-reinforced plastics]

[0122] The method for manufacturing fiber-reinforced plastics of the present invention includes the following steps:

[0123] Step 1 involves impregnating the reinforcing fiber bundles with thermosetting resin;

[0124] Step 2 involves impregnating the reinforcing fiber bundles with thermoplastic resin;

[0125] Step 3 involves cutting the reinforcing fiber bundles to create discontinuous reinforcing fiber bundles;

[0126] Step 4 involves stacking the required number of sheets of the fiber-reinforced plastic substrate with the thermoplastic resin exposed on at least one surface in the thickness direction; and

[0127] Step 5 involves molding the fiber-reinforced plastic through heating and pressurization.

[0128] The procedure 5 is performed after the procedures 1 to 4, or simultaneously with the procedure 2 after the procedures 1, 3 and 4, or simultaneously with the procedure 1 after the procedures 2, 3 and 4.

[0129] In the method for manufacturing fiber-reinforced plastics of the present invention, the viscosity of the thermosetting resin and the thermoplastic resin is reduced by heating. Under this state, pressure is applied, causing the discontinuous reinforcing fiber bundles, along with the thermosetting and thermoplastic resins, to flow through shaping and / or stretching, etc., enabling the fiber-reinforced plastic to be molded by fully impregnating the thermosetting and thermoplastic resins into the discontinuous reinforcing fiber bundles while conforming to complex shapes.

[0130] When performing step 5 after performing steps 1 to 4, steps 1 to 4 can be performed in any order, and there are no restrictions on the steps. As long as the thermoplastic resin is exposed on at least one side of the surface in the thickness direction, for example, the impregnation of thermosetting resin or thermoplastic resin, the cutting of reinforcing fiber bundles, etc., can be performed after the substrate constituting the fiber-reinforced plastic is laminated. Then, the fiber-reinforced plastic of the present invention is formed through step 5.

[0131] Furthermore, when step 5 is performed simultaneously with step 2, the fiber-reinforced plastic of the present invention can be manufactured efficiently because two steps can be performed at the same time. In this case, steps 1, 3, and 4 can be performed in any order, as long as the thermoplastic resin is exposed on at least one side of the surface in the thickness direction; there are no restrictions on the steps in which they are performed. Then, by performing steps 5 and 2 simultaneously, the fiber-reinforced plastic of the present invention is formed while the thermoplastic resin is impregnated into the discontinuous reinforcing fiber bundles.

[0132] Similarly, when step 5 is performed simultaneously with step 1, the fiber-reinforced plastic of the present invention can be manufactured efficiently because two steps can be performed at the same time. In this case, steps 2, 3, and 4 can be performed in any order, as long as the thermoplastic resin is exposed on at least one side of the surface in the thickness direction; there are no restrictions on the steps in which they are performed. Then, by performing steps 5 and 1 simultaneously, the fiber-reinforced plastic of the present invention is formed while the thermosetting resin is impregnated into the discontinuous reinforcing fiber bundles.

[0133] In step 1, there are no particular limitations on the method of impregnating the reinforcing fiber bundle with thermosetting resin. Examples include: impregnating a discontinuous reinforcing fiber bundle formed by cutting the reinforcing fiber bundle into a specified shape with thermosetting resin; impregnating an intermediate containing thermoplastic resin and discontinuous reinforcing fiber bundle with thermosetting resin; cutting a unidirectional prepreg blank impregnated with thermoplastic resin into a certain width and fiber length using a roller cutter or the like, dispersing it into sheets, and impregnating it with thermosetting resin from one or both sides; or impregnating the unidirectional prepreg blank with thermosetting resin from one or both sides by inserting a cut formed by a rotary cutter, Thomson cutter, automatic cutting machine, laser irradiation, etc., at a specific location; and so on.

[0134] In step 2, there are no particular limitations on the method of impregnating the reinforcing fiber bundle with thermoplastic resin. Examples include: impregnating a discontinuous reinforcing fiber bundle formed by cutting the reinforcing fiber bundle into a specified shape with thermoplastic resin; impregnating an intermediate containing thermosetting resin and discontinuous reinforcing fiber bundle with thermoplastic resin; cutting a unidirectional prepreg blank impregnated with thermosetting resin into a certain width and fiber length using a roller cutter or the like, dispersing it into sheets, and impregnating it with thermoplastic resin from one or both sides; or impregnating the unidirectional prepreg blank with thermoplastic resin from one or both sides by inserting a cut formed by a rotary cutter, Thomson cutter, automatic cutting machine, laser irradiation, etc., at a specific location; and so on.

[0135] In step 3, there are no particular limitations on the method of cutting the reinforcing fiber bundles to form discontinuous reinforcing fiber bundles. Examples include: cutting the unidirectional prepreg blank impregnated with thermosetting resin and / or thermoplastic resin into a certain width and fiber length using a roller cutter or the like; inserting a cut at a specific location on the unidirectional prepreg blank formed by a rotary cutter, a Thomson cutter, an automatic cutting machine, laser irradiation, etc.; and so on.

[0136] In step 4, there are no particular limitations on the method of laminating the required number of sheets of the fiber-reinforced plastic substrate in such a way that the thermoplastic resin is exposed on at least one surface in the thickness direction. Examples include: manual lamination, lamination using a robotic arm, etc.

[0137] In step 5, the heating temperature and pressure vary depending on the types of thermosetting and thermoplastic resins used in the fiber-reinforced plastics according to the present invention. The heating temperature and pressure can be set within the range of temperature and pressure at which both the thermosetting and thermoplastic resins flow. Additionally, as needed, they can be set within the range of temperature and pressure at which the discontinuous reinforcing fiber bundles flow together with the two resins.

[0138] Methods of heating and pressurizing include, for example, heating and pressurizing using heating rollers, pressing molding, autoclave molding, vacuum pressurization molding, and internal pressure molding.

[0139] In addition, the method for manufacturing fiber-reinforced plastics of the present invention preferably further includes step 6: in the exposed surface layer of thermoplastic resin, the substrate is flowed in such a way that the ends of discontinuous reinforcing fiber bundles in the longitudinal direction are connected to thermosetting resin or thermoplastic resin.

[0140] By connecting the ends of the discontinuous reinforcing fiber bundles along their length to a thermosetting or thermoplastic resin, stress concentration at the ends of the discontinuous reinforcing fiber bundles along their length can be prevented, further demonstrating the characteristics of the fiber-reinforced plastic of the present invention, and is therefore preferred.

[0141] Step 6 is preferably performed before or simultaneously with step 5.

[0142] In addition, in step 6, preferably, at least a portion of the discontinuous reinforcing fiber bundle is connected to both the thermosetting resin and the thermoplastic resin in the exposed surface layer of the thermoplastic resin, and the substrate is flowed in such a way that at least one of the reinforcing fibers constituting the reinforcing fiber bundle is continuously connected to the thermoplastic resin in the length direction from the end of the reinforcing fiber.

[0143] By continuously connecting the thermoplastic resin from the end of the reinforcing fiber along its length, the interface shape between the thermosetting resin and the thermoplastic resin passing through the reinforcing fiber becomes more complex, and the bonding between the thermosetting resin and the thermoplastic resin becomes stronger. Therefore, it is preferable to further exhibit the characteristics of the fiber-reinforced plastic of the present invention.

[0144] Furthermore, in step 6, it is preferable to flow the substrate in a manner that has only thermoplastic resin present at the ends of the connecting discontinuous reinforcing fiber bundles along the straight line with other discontinuous reinforcing fiber bundles in the longitudinal direction.

[0145] By having a combination of thermoplastic resin present only along the straight line connecting the ends of the discontinuous reinforcing fiber bundles in the longitudinal direction with other discontinuous reinforcing fiber bundles, it is easy to obtain a structure in which the thermoplastic resin is deeply impregnated between the fiber bundles. As a result, a structure with a more complex interface between the thermosetting resin and the thermoplastic resin can be obtained, and the bonding between the thermosetting resin and the thermoplastic resin becomes stronger, thus further exhibiting the characteristics of the fiber-reinforced plastic of the present invention, which is preferred.

[0146] The fiber-reinforced plastic of the present invention can be manufactured by laminating the substrate constituting the fiber-reinforced plastic alone or together with other prepregs, sheet molding compounds, cut prepregs, etc., using known methods, and then curing the resulting laminate by heating and pressurizing.

[0147] In this case, as long as the thermoplastic resin is exposed on at least one side of the surface in the thickness direction of the manufactured fiber-reinforced plastic, there are no restrictions on the stacking order of the other layers.

[0148] Furthermore, the fiber-reinforced plastic of the present invention can be manufactured by compression molding of a substrate constituting the fiber-reinforced plastic by stretch molding. The fiber-reinforced plastic of the present invention contains discontinuous reinforcing fiber bundles. Therefore, when compression molding is used, as the thermosetting resin and thermoplastic resin contained in the fiber-reinforced plastic flow, the discontinuous reinforcing fiber bundles also flow, resulting in excellent shape conformability of the fiber-reinforced plastic of the present invention. Examples of structures with excellent shape conformability include rib-shaped and convex-concave-convex shapes, where the discontinuous reinforcing fiber bundles are oriented in the out-of-plane direction, but the invention is not limited to these.

[0149] In this case, the shape formed by stretch molding is not particularly limited as long as the substrate can fully follow the shape and maintain sufficient surface quality and bond strength. However, it is preferable to form the product such that the surface area of ​​the surface layer is 100% to 200% of the surface area of ​​the substrate constituting the fiber-reinforced plastic, thereby exhibiting the excellent shape-following characteristics of the fiber-reinforced plastic of the present invention. The range of the surface area of ​​the molded article relative to the surface area of ​​the substrate is preferably 100% to 180%, more preferably 100% to 150%.

[0150] Example

[0151] The present invention will now be described in detail through examples. However, the scope of the present invention is not limited to these examples. It should be noted that, unless otherwise specified, the measurements of various properties were performed at a temperature of 23°C and a relative humidity of 50%.

[0152] <Materials>

[0153] Use the materials shown below.

[0154] • Reinforcing fiber [A]

[0155] Uses carbon fiber [“Torayca (registered trademark)” T700S-24K, manufactured by Toray Industries, Inc., wire harness tensile strength: 4.9 GPa].

[0156] Thermosetting resins [B]

[0157] 30 parts by weight, 40 parts by weight, and 30 parts by weight of epoxy resin main agents [“jER” (registered trademark) 828 (manufactured by Mitsubishi Chemical Corporation)], [“jER” (registered trademark) 1001 (manufactured by Mitsubishi Chemical Corporation)], and [“jER” (registered trademark) 154 (manufactured by Mitsubishi Chemical Corporation)] were added respectively, and the mixture was heated and kneaded at 150°C until the components were miscible. Then, while continuing to knead, the temperature was lowered to 80°C, and 26 parts by weight of curing agent [3,3'DAS (3,3'-diaminodiphenyl sulfone, manufactured by Mitsubishi Chemical Fine Co., Ltd.)] were added, and the mixture was kneaded at 80°C for 30 minutes to obtain thermosetting resin [B].

[0158] Thermoplastic resins [C]

[0159] Sheets using polyamide 6 [“Amilan” (registered trademark) CM4000 (manufactured by Toray Industries, Inc., a ternary copolymer polyamide resin with a melting point of 155°C)].

[0160] <Evaluation Methods>

[0161] Maximum impregnation distance and average roughness height

[0162] The cross-sections of the fiber-reinforced plastics prepared in each embodiment and comparative example were embedded and ground, and then a 500 μm square area near the joint surface was observed using an optical microscope. Based on the difference in contrast of the obtained images, carbon fibers, thermoplastic resins, and thermosetting resins were identified.

[0163] Next, in the continuous region of the thermoplastic resin along the thickness direction from the joint surface, the initial contact point with the reinforcing fiber is extracted, and a line drawn parallel to the joint surface starting from this point is used as a reference line. From this reference line, vertical baselines are drawn from the thermoplastic resin towards the thermosetting resin at 5 μm intervals, and all points where the vertical baselines initially intersect with the thermosetting resin, reinforcing fiber, or voids are plotted. The maximum distance from the plotted points to the reference line is taken as the maximum impregnation distance.

[0164] Furthermore, in Examples 1-1 to 1-4 and Comparative Examples 1-1 and 1-2 described later, a surface at a 45-degree angle relative to any direction was cut out. In Examples 2-1, 2-2 and Comparative Example 2-1, a surface at a 45-degree angle relative to the orientation direction of the mating surface was cut out. After embedding and grinding the cross-section, an area of ​​500 μm square near the mating surface was observed using an optical microscope. Then, a baseline and a vertical baseline were created using the same method as for determining the maximum impregnation distance. The measurement point where the vertical baseline initially intersects with the thermosetting resin was plotted. The line connecting the plotted points was used as the cross-sectional curve, filtered, and the average roughness height was calculated.

[0165] · Long side immersion distance

[0166] Discontinuous reinforcing fiber bundles located near the surface are randomly selected, and fiber-reinforced plastic is cut parallel to the thickness direction, parallel to the orientation direction of the reinforcing fibers constituting the discontinuous reinforcing fiber bundle. Multiple portions where continuous thermoplastic resin in the thickness direction from the joint surface connects to the ends of the reinforcing fibers constituting the discontinuous reinforcing fiber bundles along their length direction are extracted. Within the discontinuous reinforcing fiber bundle, focusing on the reinforcing fibers that connect to both thermosetting and thermoplastic resins, a baseline is drawn along the length direction of the reinforcing fiber, starting from the end of the reinforcing fiber that connects to the thermoplastic resin. The points where the fiber initially intersects with the thermosetting resin or voids are extracted, and their average value is taken as the long-side impregnation distance.

[0167] • Determination of the length of thermoplastic resin passing between discontinuous reinforcing fiber bundles

[0168] In the image used for measuring the long-side impregnation distance, straight lines are drawn from the end of the discontinuous reinforcing fiber bundle along its length, toward the end or side of the other discontinuous reinforcing fiber bundle with the shortest distance, without passing through the reinforcing fibers. The total length passing through the thermoplastic resin is measured. Among these, lines with a total length passing through the thermoplastic resin of 30% or more are considered, and the proportion of lines with a total length passing through the thermoplastic resin of 50% or more is evaluated based on the following criteria.

[0169] A: More than 80%

[0170] B: 50% or more but less than 80%

[0171] C: 30% or more but less than 50%

[0172] D: Less than 30% or no straight lines with a total length of more than 30% passing through the thermoplastic resin.

[0173] • Enhance the volume content of the fiber

[0174] In Examples 1-1 to 1-4 and Comparative Examples 1-1 and 1-2, fiber-reinforced plastics were cut in any direction, embedded, and polished. Cross-sectional images of discontinuous reinforcing fiber bundles in the surface layer were then obtained using an optical microscope. In the cross-sectional images, discontinuous reinforcing fiber bundles oriented approximately perpendicular to the observation plane were selected, and the fiber volume content of these bundles was calculated based on their area ratio. The fiber volume content was calculated across multiple discontinuous reinforcing fiber bundles, and their average value was taken as the volume content of the reinforcing fibers in the surface layer.

[0175] In addition, in Examples 2-1, 2-2, and Comparative Example 2-1, the fiber-reinforced plastic was cut along a direction orthogonal to the orientation direction of the reinforcing fibers in the surface layer, embedded, and polished. Cross-sectional images of the discontinuous reinforcing fiber bundles in the surface layer were then obtained using an optical microscope. Next, the fiber volume content of the discontinuous reinforcing fibers in the cross-sectional images was calculated based on the area ratio. The fiber volume content was calculated at multiple locations, and the average value was taken as the volume content of the reinforcing fibers in the surface layer.

[0176] Tensile shear bond strength

[0177] The fiber-reinforced plastics prepared in the various embodiments and comparative examples were cut into two pieces, each 250 mm wide and 92.5 mm long, and dried in a vacuum oven for 24 hours. Then, the surfaces of the two fiber-reinforced plastics with thermoplastic resin [C] were overlapped. The overlapping area was set to be 250 mm wide × 12.5 mm long.

[0178] Then, by applying a pressure of 3 MPa at a temperature 20°C higher than the melting point of the thermoplastic resin [C] and holding it for 1 minute, the overlapping surfaces were fused together to obtain a one-piece molded article. Tabs were then glued onto the obtained one-piece molded article according to ISO 4587:1995 (JIS K6850 (1994)), and the article was cut to a width of 25 mm to obtain a test piece.

[0179] The obtained test pieces were dried in a vacuum oven for 24 hours, and the tensile shear bond strength was determined based on ISO 4587:1995 (JIS K6850 (1994)). The test results were evaluated based on the following criteria.

[0180] A: Above 30MPa

[0181] B: Above 10MPa and below 30MPa

[0182] C: Less than 10MPa (unacceptable) or not bonded

[0183] <Example 1-1>

[0184] The reinforcing fiber [A] is drawn out into a unidirectionally aligned reinforcing fiber sheet (weight per unit area 120g / m²). 2 ), to produce continuous reinforcing fiber bundles. After thinly coating the obtained continuous reinforcing fiber bundles with thermosetting resin [B], they are continuously inserted into a rotary cutter with blades spaced 25 mm apart in the circumferential direction to produce chopped fiber bundles (discontinuous reinforcing fiber bundles).

[0185] In addition, thermosetting resin [B] is coated on the release film to make two sheets of thermosetting resin [B].

[0186] Then, the chopped fiber bundles are uniformly distributed on one sheet of thermosetting resin [B], and another sheet of thermosetting resin [B] is placed on top of it. The sheet is heated to 100°C without curing the thermosetting resin [B], and simultaneously pressed using rollers at 0.07 MPa to produce an SMC prepreg blank. The volume content of the reinforcing fiber [A] in this SMC prepreg blank is adjusted to be 40%. In this SMC prepreg blank, the distributed chopped fiber bundles are in a packed state.

[0187] Eight SMC prepreg blanks cut into 300mm squares are stacked together, and thermoplastic resin [C] sheets are attached to the surface of one side to obtain a fiber-reinforced uncured plastic laminate.

[0188] The above-mentioned fiber-reinforced uncured plastic laminate was placed in a mold with a surface area of ​​300mm×300mm. In order to eliminate voids, a pressure of 0.6MPa was applied by a press, and the mixture was heated at 180°C for 2 hours to obtain fiber-reinforced plastic.

[0189] The obtained fiber-reinforced plastic exhibits less unevenness in thickness. Furthermore, it is possible to confirm, through cross-sectional observation, the formation of interfaces where regions primarily composed of thermosetting resin [B] and thermoplastic resin [C] are connected, and the inclusion of thermoplastic resin [C] between discontinuous reinforcing fiber bundles. Moreover, in all observed regions, the ends of the discontinuous reinforcing fiber bundles along their length are visually connected to either the thermosetting or thermoplastic resin.

[0190] Furthermore, the structure comprises: a portion of the discontinuous reinforcing fiber bundle located on the surface is bonded to both the thermosetting resin and the thermoplastic resin; at least a portion of the reinforcing fibers constituting the discontinuous reinforcing fiber bundle is bonded to both the thermosetting resin and the thermoplastic resin; and the reinforcing fibers and the thermoplastic resin are continuously bonded in the length direction from the ends of the reinforcing fibers. Additionally, a straight line with a total length passing through the thermoplastic resin of 100% is drawn between the multiple discontinuous reinforcing fiber bundles. The resulting fiber-reinforced plastic exhibits sufficient bond strength.

[0191] <Examples 1-2>

[0192] The fiber-reinforced uncured plastic laminate was placed in a mold with a surface area of ​​350 mm × 350 mm and stretched by applying a pressure of 3 MPa using a press. Otherwise, the fiber-reinforced plastic was obtained in the same manner as in Example 1-1.

[0193] The obtained fiber-reinforced plastic is thinner than that of Example 1-1, but has less unevenness in thickness, and the pressed fiber-reinforced plastic is stretched into a 350 mm square without gaps, exhibiting excellent shape conformation. In addition, the distance between discontinuous reinforcing fiber bundles is wider than that of Example 1-1, so the impregnation of thermoplastic resin [C] into the discontinuous reinforcing fiber bundles can be more clearly seen compared to Example 1-1, and in the entire observed area, the ends of the discontinuous reinforcing fiber bundles in the longitudinal direction are in contact with thermosetting resin or thermoplastic resin within the visual range.

[0194] Furthermore, the structure comprises: a portion of the discontinuous fiber-reinforcing bundle located on the surface is bonded to both the thermosetting resin and the thermoplastic resin; at least a portion of the reinforcing fibers constituting the discontinuous reinforcing fiber bundle is bonded to both the thermosetting resin and the thermoplastic resin; and the reinforcing fibers and the thermoplastic resin are continuously bonded in the length direction from the ends of the reinforcing fibers. Additionally, a straight line with a total length passing through the thermoplastic resin of 100% is drawn between the multiple discontinuous reinforcing fiber bundles. The resulting fiber-reinforced plastic exhibits sufficient bond strength.

[0195] <Examples 1-3>

[0196] Eight SMC prepreg blanks and eight thermoplastic resin [C] sheets, each cut to 300 mm square, were prepared. One thermoplastic resin [C] sheet was placed under each SMC prepreg blank to obtain a fiber-reinforced plastic uncured laminate consisting of alternating layers of SMC prepreg blanks and thermoplastic resin [C] sheets. The fiber-reinforced plastic uncured laminate was cured and bonded using the method described in Examples 1-1 to obtain fiber-reinforced plastic with thermoplastic resin [C] exposed on one side.

[0197] The obtained fiber-reinforced plastic exhibits less unevenness in thickness. Furthermore, it is possible to confirm, through cross-sectional observation, the formation of interfaces where regions primarily composed of thermosetting resin [B] and thermoplastic resin [C] are connected, and the inclusion of thermoplastic resin [C] between discontinuous reinforcing fiber bundles. Moreover, in all observed regions, the ends of the discontinuous reinforcing fiber bundles along their length are visually connected to either the thermosetting or thermoplastic resin.

[0198] Furthermore, the structure comprises: a portion of the discontinuous reinforcing fiber bundle located on the surface layer is bonded to both the thermosetting resin and the thermoplastic resin; at least a portion of the reinforcing fibers constituting the discontinuous reinforcing fiber bundle is bonded to both the thermosetting resin and the thermoplastic resin; and the reinforcing fibers and the thermoplastic resin are continuously bonded in the length direction from the ends of the reinforcing fibers. Additionally, a straight line with a total length of 100% passing through the thermoplastic resin is drawn between the multiple discontinuous reinforcing fiber bundles. Layers composed of thermoplastic resin are observed between the interlayers in the layers other than the surface layer. The resulting fiber-reinforced plastic exhibits sufficient bonding strength.

[0199] <Examples 1-4>

[0200] The fiber-reinforced plastic uncured laminate was placed in a mold with a surface area of ​​350mm × 350mm and stretched by applying a pressure of 3MPa using a press. Otherwise, the fiber-reinforced plastic was obtained in the same manner as in Examples 1-3.

[0201] The obtained fiber-reinforced plastic is thinner than that of Examples 1-3, but has less unevenness in thickness, and the pressed fiber-reinforced plastic is stretched into a 350 mm square without gaps, exhibiting excellent shape conformation. In addition, the distance between discontinuous reinforcing fiber bundles is wider than that of Examples 1-3, so the impregnation of thermoplastic resin [C] into the discontinuous reinforcing fiber bundles can be more clearly seen compared to Examples 1-3, and in the entire observed area, the ends of the discontinuous reinforcing fiber bundles in the longitudinal direction are in contact with thermosetting resin or thermoplastic resin within the visual range.

[0202] Furthermore, the structure comprises: a portion of the discontinuous reinforcing fiber bundle located on the surface layer is bonded to both the thermosetting resin and the thermoplastic resin; at least a portion of the reinforcing fibers constituting the discontinuous reinforcing fiber bundle is bonded to both the thermosetting resin and the thermoplastic resin; and the reinforcing fibers and the thermoplastic resin are continuously bonded in the length direction from the ends of the reinforcing fibers. Additionally, a straight line with a total length of 100% passing through the thermoplastic resin is drawn between the multiple discontinuous reinforcing fiber bundles. Layers composed of thermoplastic resin are observed between the interlayers in the layers other than the surface layer. The resulting fiber-reinforced plastic exhibits sufficient bonding strength.

[0203] <Example 2-1>

[0204] The reinforcing fibers [A] are drawn out into a continuous state arranged in a unidirectional manner to form a reinforcing fiber sheet (weight per unit area 120g / m²). 2 Thermosetting resin [B] is applied to a release film to create two sheets of thermosetting resin [B]. Then, the thermosetting resin [B] is heated at 100°C without curing, and simultaneously pressed together from above and below the reinforcing fiber [A] sheets moving in one direction using rollers at 0.07 MPa to create a unidirectional prepreg blank.

[0205] Then, using a rotary cutter, the cut is inserted at an angle of 14° relative to the length direction of the reinforcing fiber [A] in the unidirectional prepreg blank, with the fiber length of the reinforcing fiber [A] being 25 mm, to obtain a cut prepreg blank with discontinuous reinforcing fiber bundles arranged unidirectionally. The volume content of the reinforcing fiber [A] in the cut prepreg blank is adjusted to be 60%.

[0206] The orientation direction of the reinforcing fiber [A], which will become the bonding surface, is set to 0°, thus becoming [0° / 90°]. 2s (The symbol 's' indicates mirror symmetry) Eight prepreg blanks cut into 300mm squares are stacked, and then thermoplastic resin [C] sheets are attached to the surface of the joint to obtain a fiber-reinforced uncured plastic laminate.

[0207] The fiber-reinforced plastic uncured laminate was placed in a mold with a surface area of ​​300 mm × 300 mm. In order to eliminate voids, a pressure of 0.6 MPa was applied by a press, and the mixture was heated at 180°C for 2 hours to obtain fiber-reinforced plastic.

[0208] The obtained fiber-reinforced plastic exhibits less thickness non-uniformity than in Examples 1-1. Furthermore, the flow interface formed by the region primarily composed of thermosetting resin [B] and the region primarily composed of thermoplastic resin [C], as well as the case where thermoplastic resin [C] is impregnated between discontinuous reinforcing fiber bundles, can be confirmed by cross-sectional observation. Moreover, in all observed regions, the ends of the discontinuous reinforcing fiber bundles along their length are visually connected to either the thermosetting or thermoplastic resin. The configuration is such that at least a portion of the reinforcing fibers constituting the discontinuous reinforcing fiber bundles are connected to both the thermosetting and thermoplastic resins, and the reinforcing fibers and thermoplastic resins are continuously connected along their length from the ends of the reinforcing fibers.

[0209] Furthermore, a straight line with a total length of 100% passing through the thermoplastic resin is drawn between multiple discontinuous reinforcing fiber bundles. Also, a portion of the discontinuous reinforcing fiber bundles located on the surface layer is bonded to both the thermosetting and thermoplastic resins. The resulting fiber-reinforced plastic exhibits sufficient bond strength.

[0210] <Example 2-2>

[0211] The fiber-reinforced uncured plastic laminate was placed in a mold with a surface area of ​​350mm × 350mm and stretched by applying a pressure of 3MPa using a press. Otherwise, the fiber-reinforced plastic was obtained in the same manner as in Example 2-1.

[0212] The obtained fiber-reinforced plastic is thinner than that of Example 2-1, but has less thickness unevenness, and the pressed fiber-reinforced plastic is stretched into a 350 mm square without gaps, exhibiting excellent shape conformation. Furthermore, the impregnation of thermoplastic resin [C] between the discontinuous reinforcing fiber bundles is clearly visible, and in the entire observed area, the ends of the discontinuous reinforcing fiber bundles along the length direction are in contact with both the thermosetting resin and the thermoplastic resin within visual range. The following configuration exists: at least a portion of the reinforcing fibers constituting the discontinuous reinforcing fiber bundles are in contact with both the thermosetting resin and the thermoplastic resin, and the reinforcing fibers and thermoplastic resin are continuously connected along the length direction from the ends of the reinforcing fibers.

[0213] Furthermore, a straight line with a total length of 100% passing through the thermoplastic resin is drawn between multiple discontinuous reinforcing fiber bundles. Also, a portion of the discontinuous reinforcing fiber bundles located on the surface layer is bonded to both the thermosetting and thermoplastic resins. The resulting fiber-reinforced plastic exhibits sufficient bond strength.

[0214] <Comparative Example 1-1>

[0215] Fiber-reinforced plastics were obtained in the same manner as in Examples 1-1, except that thermoplastic resin [C] sheets were not used.

[0216] The obtained fiber-reinforced plastic is already in a cured state. Therefore, when the test piece for tensile shear bond strength is made, the laminate does not bond during pressing and cannot be evaluated.

[0217] <Comparative Examples 1-2>

[0218] Similar to Example 1-1, eight SMC prepreg blanks were laminated, but thermoplastic resin [C] sheets were not used to produce a fiber-reinforced uncured plastic laminate.

[0219] The aforementioned uncured fiber-reinforced plastic laminate was placed in a mold with a surface area of ​​300 mm × 300 mm. To eliminate voids, a pressure of 0.6 MPa was applied using a press, and the laminate was heated at 180°C for 2 hours to obtain a cured product. Then, a thermoplastic resin [C] sheet was overlapped on one surface of the cured product and melted at 180°C for 2 hours, causing the thermoplastic resin [C] to adhere to the cured product, thus obtaining a fiber-reinforced plastic.

[0220] The resulting fiber-reinforced plastics exhibited less unevenness in thickness, but almost no impregnation of thermoplastic resin [C] into the discontinuous fiber bundles, and the bond strength could not be considered adequate.

[0221] <Comparative Example 2-1>

[0222] Without using thermoplastic resin [C] sheets, except as in Example 2-2, slit prepreg blanks were laminated. The fiber-reinforced plastic uncured laminate was placed in a mold with a surface area of ​​350mm × 350mm, and stretched using a press with a pressure of 3MPa to produce a cured product without thermoplastic resin [C]. Then, thermoplastic resin [C] sheets of 350mm × 350mm size were cut and overlapped on one surface of the cured product. These sheets were placed in a mold with a surface area of ​​350mm × 350mm, and a pressure of 3MPa was applied using a press to eliminate voids. The product was then melted at 180°C for 2 hours, allowing the thermoplastic resin [C] to bond to the cured product, thus obtaining fiber-reinforced plastic.

[0223] The cured material, after pressing, can be stretched seamlessly into 350 mm square sections with excellent shape conformation. Furthermore, the resulting fiber-reinforced plastic exhibits less thickness inhomogeneity. However, almost no thermoplastic resin [C] impregnation into the discontinuous fiber bundles is observed, and the bond strength cannot be considered adequate.

[0224] • Evaluation of shape following

[0225] <Example 3-1>

[0226] The orientation direction of the reinforcing fiber [A] that will form the surface layer of the joint is set to 0°, with a size of 200 mm square, to form [0° / 90°]. s In this manner, four prepreg blanks manufactured in Example 2-1 are stacked, and then thermoplastic resin [C] sheets are attached to one side of the surface to obtain a fiber-reinforced uncured plastic laminate.

[0227] A fiber-reinforced uncured plastic laminate is placed in a mold having both planar and curved surfaces, with thermoplastic resin [C] as the top surface. To eliminate voids, a pressure of 3 MPa is applied using a press, and the laminate is heated at 180°C for 2 hours, thereby obtaining a product that... Figure 9 Fiber-reinforced plastic of the shape shown.

[0228] When the surface of the bonded surface of the pressed fiber-reinforced plastic was visually inspected, no wrinkles or other defects were observed on the curved surface. Furthermore, the resin accumulation at the corners of the curved surface was less than that in Comparative Example 3-1 described later.

[0229] <Comparative Example 3-1>

[0230] No incision was inserted; otherwise, fiber-reinforced plastic was obtained in the same manner as in Example 3-1.

[0231] When the surface of the obtained fiber-reinforced plastic joint was visually observed, almost no wrinkles occurred on the curved surface, but in a part of the corner of the curved surface, the resin enrichment was greater than that in Example 3-1, and the shape conformity and homogeneity were poor.

[0232] Table 1 shows the summary, maximum impregnation distance, average roughness height, volume fraction of reinforcing fibers in the surface layer, and evaluation results of tensile shear bond strength of the fiber-reinforced plastics prepared from Examples 1-1 to 1-4, 2-1, 2-2 and Comparative Examples 1-1, 1-2, 2-1.

[0233] It should be noted that the maximum impregnation distance / average roughness height and the long side impregnation distance in the embodiments are values ​​obtained by rounding the units digit. The maximum impregnation distance / average roughness height shown in the comparative examples are reference values ​​obtained with the surface of the cured product as the baseline because the thermoplastic resin did not reach the reinforcing fibers.

[0234] [Table 1]

[0235]

[0236] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2020-126652, filed on July 27, 2020, the contents of which are incorporated herein by reference.

[0237] Explanation of reference numerals in the attached figures

[0238] 1: Fiber-reinforced plastics

[0239] 2: Discontinuous reinforcing fiber bundles

[0240] 3: Discontinuous reinforcing fibers

[0241] 4, 4': Thermoplastic resin

[0242] 5: Thermosetting resins

[0243] 6: Interface

[0244] 7: Cut prepreg blank

[0245] 8: Incision

[0246] 9: Reinforce the length direction of the fiber bundle

[0247] 10: Direction orthogonal to the length direction of the reinforcing fiber bundle

[0248] 11: Baseline

[0249] 12: Vertical baseline

[0250] 13: Measurement points for immersion distance

[0251] 14: Measurement points for average roughness height

[0252] 15: The baseline drawn along the side of the reinforcing fiber.

[0253] 16: Measurement point for the immersion distance of the long side

Claims

1. Fiber-reinforced plastics, among which, As at least one surface layer in the thickness direction, it has a layer comprising reinforcing fibers and a matrix integrally formed of thermosetting resin and thermoplastic resin. The reinforcing fibers form discontinuous reinforcing fiber bundles that are randomly stacked, or form discontinuous reinforcing fiber bundles that are arranged in a unidirectional direction. A portion of the discontinuous reinforcing fiber bundle is in contact with both the thermosetting resin and the thermoplastic resin. At least a portion of the thermoplastic resin is exposed on the surface of the surface layer. In the surface layer, the average fiber length of the reinforcing fibers ranges from 5 mm to 100 mm. In the surface layer, the long side impregnation distance is 50 μm or more.

2. The fiber-reinforced plastic according to claim 1, wherein, In the surface layer, an interface is formed between the region where the thermosetting resin is the main component and the region where the thermoplastic resin is the main component.

3. The fiber-reinforced plastic according to claim 1 or 2, wherein, The surface layer has a region in which the thermoplastic resin is continuous in the thickness direction from the surface. The maximum thickness of the portion where the thermoplastic resin meets the discontinuous reinforcing fiber bundle within the specified area is 10 μm or more.

4. The fiber-reinforced plastic according to claim 1 or 2, wherein, In the surface layer, the content of the reinforcing fiber is more than 15% by volume and less than 70% by volume.

5. The fiber-reinforced plastic according to claim 1 or 2, wherein, In the surface layer, the reinforcing fiber is at least one selected from the group consisting of carbon fiber and glass fiber.

6. The fiber-reinforced plastic according to claim 1 or 2, wherein, In the surface layer, the ratio of voids that connect to the ends of the discontinuous reinforcing fiber bundles along their length is less than 5% by area.

7. The fiber-reinforced plastic according to claim 1 or 2, wherein, In the surface layer, the thermoplastic resin is present between the discontinuous reinforcing fiber bundles.

8. The fiber-reinforced plastic according to claim 7, wherein, The thermoplastic resin occupies the space between any adjacent discontinuous fiber reinforcement bundles.

9. The fiber-reinforced plastic according to claim 1 or 2, wherein, The two surface layers in the thickness direction have the discontinuous reinforcing fiber bundles, the thermoplastic resin, and the thermosetting resin. The thermoplastic resin is exposed on the surfaces of the two surface layers.

10. The fiber-reinforced plastic according to claim 1 or 2, wherein, At least a portion of the discontinuous reinforcing fiber bundles constituting fiber-reinforced plastics are oriented out of plane.

11. A method for manufacturing fiber-reinforced plastic, comprising the method for manufacturing fiber-reinforced plastic according to any one of claims 1 to 10, the method comprising: Step 1 involves impregnating the reinforcing fiber bundles with thermosetting resin; Step 2 involves impregnating the reinforcing fiber bundles with thermoplastic resin; Step 3 involves cutting the reinforcing fiber bundles to create discontinuous reinforcing fiber bundles; Step 4 involves stacking the required number of sheets of the fiber-reinforced plastic substrate with the thermoplastic resin exposed on at least one surface in the thickness direction; and Step 5 involves molding the fiber-reinforced plastic through heating and pressurization. The procedure 5 is performed after procedures 1 to 4, or simultaneously with procedure 2 after procedures 1, 3 and 4, or simultaneously with procedure 1 after procedures 2, 3 and 4.

12. The method for manufacturing fiber-reinforced plastic according to claim 11, comprising: Step 6: In the exposed surface of the thermoplastic resin, the ends of the discontinuous reinforcing fiber bundles are connected to the thermosetting resin or the thermoplastic resin along their length direction.

13. The method for manufacturing fiber-reinforced plastic according to claim 11 or 12, wherein, In step 6, at least a portion of the discontinuous reinforcing fiber bundles are in contact with both the thermosetting resin and the thermoplastic resin in the exposed surface layer of the thermoplastic resin. Furthermore, at least one of the reinforcing fibers constituting the reinforcing fiber bundle flows in a manner in which the thermoplastic resin is continuously connected to the reinforcing fiber in the length direction from its end in the length direction.

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