Reinforced fiber composites

Abstract

The present invention provides an excellent reinforced fiber composite material, which can achieve both high fluidity and high mechanical properties during molding, which cannot be achieved by conventional reinforced fiber composite materials formed of discontinuous reinforcing fibers and matrix resins, and can suppress the flow of discontinuous reinforcing fibers caused by the flow of resin when the matrix resin is impregnated into a sheet-like substrate under pressure in the manufacturing process of sheet-like molding materials such as SMC and stamping molding sheets as precursors of the discontinuous reinforced fiber composite material. The reinforced fiber composite material comprises 20wt% or more and less than 70wt% of discontinuous reinforcing fibers and matrix resin, at least a part of the discontinuous reinforcing fibers forms a fiber aggregate, and for at least one bundle of the fiber aggregate, when a certain surface of the fiber aggregate is projected onto a two-dimensional plane, there are at least one region where the number of single fibers constituting the aggregate is reduced, at both ends in the length direction of the minimum circumscribed rectangle of the projection surface, and outside the two ends.

Description

Technical Field

[0001] The present invention relates to a reinforced fiber composite material comprising discontinuous reinforcing fibers and a matrix resin. Background Art

[0002] Fiber-reinforced composite materials including reinforcing fibers and a matrix resin can obtain high mechanical properties and are therefore used in the manufacture of various molded products. Demand for these materials in various fields is increasing year by year.

[0003] In particular, the reinforced fiber composite material with high functional characteristics uses carbon fiber in the reinforcing fiber. As a molding method for carbon fiber composite materials, the most common is to perform autoclave molding, wherein the autoclave molding is to laminate the intermediate substrate in a semi-cured state formed by impregnating the matrix resin into the continuous carbon fiber, which is called prepreg, and heat and pressurize it using a high-temperature autoclave, so that the matrix resin is cured to perform the molding of the continuous fiber reinforced composite material. In addition, in recent years, for the purpose of improving production efficiency, RTM (resin transfer molding) molding, which impregnates the matrix resin in the continuous fiber substrate pre-shaped as the component shape and solidifies it, has also been carried out. The carbon fiber composite material obtained by these molding methods has excellent mechanical properties because it is a continuous fiber. In addition, since the continuous fiber is a regular arrangement, it can be designed into the required mechanical properties by the configuration of the substrate, and the deviation of the mechanical properties is also small. However, on the other hand, since it is a continuous fiber, it is difficult to form a complex shape such as a three-dimensional shape, which is mainly limited to components close to a planar shape.

[0004] As a molding method suitable for complex shapes such as three-dimensional shapes, there are molding using SMC (sheet molding compound) and stamping sheets. SMC molded products can be obtained by cutting the raw filaments of reinforcing fibers in a manner such that the fiber length becomes about 25 mm in a direction orthogonal to the fibers, impregnating the chopped raw filaments with a matrix resin as a thermosetting resin to form a sheet substrate (SMC) in a semi-cured state, and heating and pressurizing it using a heating press. Stamping sheet molded products can be obtained, for example, by impregnating a non-woven felt composed of chopped raw filaments or discontinuous reinforcing fibers cut into about 25 mm with a thermoplastic resin to form a sheet substrate (stamping sheet), temporarily heating it to a temperature above the melting point of the thermoplastic resin using an infrared heater, and cooling and pressurizing it in a mold at a specified temperature.

[0005] In most cases, before pressurization, SMC and stamping formed sheets are cut into a shape smaller than the shape of the molded body and arranged on a molding die, and are stretched (flowed) into the shape of the molded body by pressurization for molding. Therefore, through this flow, complex shapes such as three-dimensional shapes can also be followed. However, SMC and stamping formed sheets will inevitably produce uneven distribution and uneven orientation of chopped strands and non-woven felts in their sheeting process, so the mechanical properties are reduced, or the deviation of their values ​​becomes larger. Moreover, due to the uneven distribution and uneven orientation, warping, shrinkage marks, etc. are prone to occur, especially in thin components.

[0006] In order to compensate for the above-mentioned material shortcomings, for example, Patent Document 1 proposes a chopped fiber bundle and a molding material, wherein the chopped fiber bundle has the following range: for the chopped fiber bundle, starting from the two ends of the fiber orientation direction in the bundle and toward the center of the chopped fiber bundle, the number of reinforcing fibers increases in the orientation direction of the reinforcing fibers.

[0007] In addition, Patent Document 2 proposes a discontinuous fiber reinforced composite material, characterized in that the lengths of the discontinuous fiber bundles are different, and the longer the discontinuous fiber bundle, the smaller the front end angle of the acute angle formed at the end of the discontinuous reinforcing fiber bundle when projected onto a two-dimensional plane.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2008 / 149615

[0011] Patent Document 2: International Publication No. 2017 / 145884 Summary of the invention

[0012] Problems to be solved by the invention

[0013] In general, for composite materials using discontinuous reinforcing fibers, if the discontinuous reinforcing fibers enter the matrix resin, the fluidity of the composite material during molding decreases, but the decrease in fluidity can be suppressed by increasing the amount of discontinuous reinforcing fibers in the form of an aggregate. However, if the discontinuous reinforcing fiber bundle is in a long strip shape when projected onto a two-dimensional plane, when forming a reinforced fiber composite material, structural defects that become the starting point of destruction are easily generated at the portion where the fiber bundles overlap each other and around the ends of the fiber bundles, and there is a tendency for poor mechanical properties.

[0014] In addition, the longer the fiber length of the discontinuous reinforcing fibers, the better the mechanical properties of the reinforced fiber composite material, but the interweaving of the fibers increases and the fluidity is poor. On the contrary, the shorter the fiber length of the discontinuous reinforcing fibers, the better the fluidity of the reinforced fiber composite material, but there is a tendency for the mechanical properties to be poor. That is, the optimal form of the reinforced fiber composite material that emphasizes good fluidity and the optimal form of the reinforced fiber composite material that emphasizes mechanical properties are not necessarily the same form.

[0015] Furthermore, the shorter the fiber length of the discontinuous reinforcing fibers, the better the fluidity when the obtained fiber-reinforced composite material is. However, in the manufacturing process of sheet-like substrates such as SMC and press-molded sheets, which are precursors of the discontinuous reinforcing fiber composite materials, when the matrix resin is impregnated into the sheet-like molding material under pressure, the restraint force between the discontinuous reinforcing fibers is weak, and the discontinuous reinforcing fibers flow aimlessly along with the flow of the resin, which causes anisotropy and deviation in mechanical properties when the obtained discontinuous reinforcing fiber composite material is obtained.

[0016] Here, in the invention described in Patent Document 1, the chopped fiber bundle has an arbitrary length distribution, and the central portion of the chopped fiber bundle other than the two end portions has not been sufficiently studied.

[0017] Furthermore, in the invention described in Patent Document 2, adequate studies have not been conducted on the appropriate ranges of the length and composition ratio of the discontinuous fiber bundle and the central portion of the discontinuous reinforcing fiber bundle excluding both end portions.

[0018] Therefore, an object of the present invention is to provide an excellent reinforced fiber composite material which can achieve both high fluidity and high mechanical properties during molding, which cannot be achieved by conventional reinforced fiber composite materials composed of discontinuous reinforcing fibers and a matrix resin, at a high level, and can suppress the flow of discontinuous reinforcing fibers due to the flow of the resin when the matrix resin is impregnated into a sheet-like base material in the manufacturing process of a sheet-like molding material such as SMC or a press-molded sheet, which is a precursor of the discontinuous reinforced fiber composite material, and achieve a balanced balance in mechanical properties.

[0019] Means of solving the problem

[0020] In order to solve the above-mentioned problems, the reinforced fiber composite material of the present invention has the following features.

[0021] [1] A discontinuous reinforced fiber composite material comprising 20 wt% or more and less than 70 wt% of discontinuous reinforced fibers and a matrix resin, wherein at least a portion of the discontinuous reinforced fibers form a fiber assembly, and for at least one bundle of the fiber assembly, when a certain surface of the fiber assembly is projected onto a two-dimensional plane, at each of the two ends in the length direction of the minimum circumscribed rectangle of the projection surface and outside the two ends, there is one or more regions where the number of single fibers constituting the fiber assembly is reduced (hereinafter referred to as "bow-shaped discontinuous reinforced fiber assembly (A)").

[0022] [2] The discontinuous reinforcing fiber composite material described in [1], wherein when the fiber assembly in which the long side length of the minimum circumscribed rectangle of the discontinuous reinforcing fiber assembly is 30 mm or more is set as the discontinuous reinforcing fiber assembly (1), 2 wt% or more and 15 wt% or less of the entire discontinuous reinforcing fibers form the discontinuous reinforcing fiber assembly (1).

[0023] [3] The discontinuous reinforcing fiber composite material described in [2], wherein at least one bundle of the discontinuous reinforcing fiber assembly (1) is a bow-shaped discontinuous reinforcing fiber assembly (A).

[0024] [4] The discontinuous reinforced fiber composite material described in [1] to [3], when the fiber assembly in which the long side length of the minimum circumscribed rectangle is less than 30 mm in the fiber assembly is set as the discontinuous reinforced fiber assembly (2), the ratio of "number average long side length of the minimum circumscribed rectangle: number average fiber length" of the discontinuous reinforced fiber assembly (2) is "1.5:1.0" to "2.0:1.0".

[0025] [5] The discontinuous reinforcing fiber composite material described in [2] to [4], wherein, when a surface of the discontinuous reinforcing fiber assembly (1) is projected onto a two-dimensional plane, the number average angle of the acute angle of the front end portion in the longitudinal direction relative to the longitudinal direction of the projection plane is 5° or more and 30° or less.

[0026] [6] The discontinuous reinforcing fiber composite material described in [4] to [5], wherein, when a surface of the discontinuous reinforcing fiber assembly (2) is projected onto a two-dimensional plane, the number average angle of the acute angle of the front end portion in the longitudinal direction relative to the longitudinal direction of the projection plane is 5° or more and 30° or less.

[0027] [7] In the discontinuous reinforced fiber composite material described in [1] to [7], the number average obtuse angle formed by the inclined surface of the above-mentioned area with reduced number of single fibers present at a position other than the two end portions of the bow-shaped discontinuous reinforced fiber aggregate (A) with respect to the length direction of the minimum circumscribed rectangle of the projection plane is 135° or more and 175° or less.

[0028] [8] The discontinuously reinforced fiber composite material described in any one of [1] to [8], wherein the number average fiber length of the discontinuously reinforced fibers is 3 mm or more and less than 100 mm.

[0029] Effects of the Invention

[0030] Thus, according to the present invention, it is possible to provide a composite material using discontinuous fibers which can simultaneously achieve excellent fluidity during molding and high mechanical properties and two-dimensional isotropy of the molded product, and which also has less variation in mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 (1) is an example of the bow-shaped discontinuous reinforcing fiber assembly (A) used in the present invention. (2) is an example of the front end angle θ and the obtuse angle α of the bow-shaped discontinuous reinforcing fiber assembly (A). (3) is an example of the minimum circumscribed rectangle of the bow-shaped discontinuous reinforcing fiber assembly (A).

[0032] Figure 2 This is an example of the shape when the bow-shaped discontinuous reinforcing fiber aggregate (A) used in the present invention is two-dimensionally projected.

[0033] Figure 3 This is an example of a process for obtaining a molding material that is a precursor of the discontinuously reinforced fiber composite material used in the present invention.

[0034] Figure 4 (1) is an example of a disc cutter used in the present invention, and (2) is an example of a diagram showing a state where a fiber aggregate is cut by a disc cutter.

[0035] Figure 5 (1) is an example of a non-bow-shaped discontinuous reinforcing fiber aggregate (2). (2) is an example of a tip angle θ obtained by obtaining the above discontinuous reinforcing fiber aggregate (2).

[0036] Figure 6 (1) is an example of the bow-shaped discontinuous reinforcing fiber aggregate (A). (2) is an example of the angle α for obtaining the bow-shaped discontinuous reinforcing fiber aggregate (A). DETAILED DESCRIPTION

[0037] Hereinafter, the present invention will be described in detail together with Examples and Comparative Examples.

[0038] In the present invention, the fiber-reinforced composite material contains 20 wt% or more and less than 70 wt% of discontinuous reinforcing fibers. More preferably, it is 30 wt% or more and 65 wt% or less, and further preferably, it is 40 wt% or more and 60 wt% or less. In order to exhibit high mechanical properties, the composite material contains 20 wt% or more of discontinuous reinforcing fibers, and in order to exhibit high fluidity and formability, the composite material contains less than 70 wt% of discontinuous reinforcing fibers. If more than 70 wt% of discontinuous reinforcing fibers are included, the fluidity and formability are deteriorated, and defects such as pores are easily included in the fiber-reinforced composite material.

[0039] In the present invention, discontinuous reinforcing fibers constitute a fiber aggregate. However, not all discontinuous reinforcing fibers must form a fiber aggregate. For at least one bundle of the fiber aggregate, when a certain surface of the fiber aggregate is projected onto a two-dimensional plane, there are at least one region where the number of single filaments constituting the fiber aggregate is reduced (hereinafter, sometimes referred to as a region where single filaments are reduced) at both ends and outside the two ends in the length direction of its minimum circumscribed rectangle. The fiber aggregate has at least one region where the number of fibers decreases toward the ends, and at least one region where the number of fibers decreases from the ends to the center outside the two ends. Hereinafter, such a fiber aggregate is referred to as a bow-shaped discontinuous reinforcing fiber aggregate (A). By forming the fiber aggregate into a bow shape, the thickness of the fiber bundle in the region where the single filaments are reduced becomes thinner, and it is not easy to produce structural defects that become the starting point of destruction around the ends of the discontinuous reinforcing fiber bundles and the overlapping parts of the discontinuous reinforcing fiber bundles, so it is preferred.

[0040] The shape of the projection surface obtained by projecting a certain surface of the bow-shaped discontinuous reinforcing fiber aggregate (A) onto a two-dimensional plane is preferably as follows: Figure 2 By making the bow-shaped discontinuous reinforcing fiber aggregate (A) present these shapes, structural defects formed around the ends of the discontinuous reinforcing fiber bundles and the parts where the discontinuous reinforcing fiber bundles overlap each other are less likely to occur, so it is preferred.

[0041] In the present invention, the discontinuous reinforcing fibers may not all form the arch-shaped discontinuous reinforcing fiber aggregate (A), and may include discontinuous reinforcing fibers opened to a single filament level when a discontinuous reinforcing fiber sheet is produced, chopped strands formed by directly cutting strands, split chopped strands formed by splitting chopped strands in the width direction, chopped strands that do not satisfy the shape of the arch-shaped discontinuous reinforcing fiber aggregate (A), expanded chopped strands formed by expanding the entire chopped strands, and expanded split strands formed by expanding and splitting the entire chopped strands.

[0042] In the present invention, for a projection surface obtained by projecting a certain surface onto a two-dimensional plane, it is preferred that a discontinuous reinforcing fiber aggregate (1) having a minimum circumscribed rectangle with a long side length of 30 mm or more is contained in the entire discontinuous reinforcing fiber, which is 2 wt% or more and 15 wt% or less. By containing 2 wt% or more of the discontinuous reinforcing fiber aggregate (1), when the matrix resin is pressurized into the sheet-like substrate in the manufacturing process of the sheet-like molding material such as SMC and stamping molding sheet, which is a precursor of the reinforced fiber composite material, the restraint force between the discontinuous reinforcing fibers can be enhanced. Therefore, the purposeless flow of the discontinuous reinforcing fibers accompanying the flow of the resin can be suppressed, and the anisotropy and deviation of the mechanical properties when the discontinuous reinforcing fiber composite material is formed can be reduced. By making the discontinuous reinforcing fiber aggregate (1) less than 15 wt%, the reduction in the fluidity of the discontinuous reinforcing fiber composite material can be suppressed, which is preferred.

[0043] The discontinuous reinforcing fiber assembly (1) preferably includes at least one bundle of arched discontinuous reinforcing fiber assemblies (A). Since the length of the long side of the minimum circumscribed rectangle when the discontinuous reinforcing fiber assembly (1) is projected onto a two-dimensional plane is long, structural defects that become the starting point of destruction may occur around the ends of the discontinuous reinforcing fiber bundles and in the portions where the discontinuous reinforcing fiber bundles overlap each other, but by including at least one bundle of arched discontinuous reinforcing fiber assemblies (1), structural defects that become the starting point of destruction are less likely to occur.

[0044] In order to prevent structural defects that serve as a starting point of destruction from occurring, the arched discontinuous reinforcing fiber aggregate (A) preferably contains 1 wt% to 15 wt% of the arched discontinuous reinforcing fiber aggregate (A) in the entire discontinuous reinforcing fibers.

[0045] The discontinuous reinforcing fiber aggregate contained in the discontinuous reinforcing fibers includes a discontinuous reinforcing fiber aggregate (2) whose long side length of the minimum circumscribed rectangle when projected onto a two-dimensional plane is less than 30 mm, and its "number average minimum circumscribed rectangle long side length: number average fiber length" ratio is preferably "1.5:1.0" to "2.0:1.0". By making the long side length of the number average minimum circumscribed rectangle 1.5 times or more relative to the number average fiber length, it is difficult to generate structural defects that become the starting point of destruction around the end of the discontinuous reinforcing fiber bundle, which is preferred. By making the long side length of the number average minimum circumscribed rectangle 2.0 times or less relative to the number average fiber length, it is possible to suppress the reduction in the fluidity of the discontinuous reinforcing fiber composite material, which is preferred.

[0046] It is preferred that the number average angle of the acute angle θ of the front end relative to the longitudinal direction when projected onto a two-dimensional plane is 5° or more and 30° or less. By setting the number average angle of the acute angle θ of the front end to 5° or more, the fluidity of the discontinuous reinforcing fiber composite material can be suppressed from decreasing. By setting the number average angle of the acute angle θ of the front end to 30° or less, it is not easy to generate structural defects that serve as the starting point of destruction around the end of the discontinuous reinforcing fiber bundle, which is preferred.

[0047] When the bow-shaped discontinuous reinforcing fiber aggregate (A) is projected onto a two-dimensional plane, the number average angle of the obtuse angle α formed by the inclined surface of the region where the single fibers are reduced at positions other than the two ends with respect to the length direction of the minimum circumscribed rectangle in the above-mentioned projection plane is preferably 135° or more and 175° or less. By setting the number average angle of the obtuse angle α to be within the range of 135° or more and 175° or less, when the discontinuous reinforcing fiber bundles overlap each other, the thickness of the fiber bundles is easily reduced, and structural defects that become the starting point of destruction are less likely to occur, which is preferred.

[0048] The number average fiber length of the discontinuous reinforcing fibers is preferably 3 mm or more and less than 100 mm. By setting the number average fiber length to be 3 mm or more and less than 100 mm, good fluidity and mechanical properties can be well balanced, which is preferred.

[0049] The reinforcing fibers used in the present invention preferably include organic fibers such as aramid fibers, polyethylene fibers, and poly(p-phenylene benzoxazole) fibers, inorganic fibers such as glass fibers, carbon fibers, silicon carbide fibers, alumina fibers, Tirano fibers, basalt fibers, and ceramic fibers, metal fibers such as stainless steel fibers and steel fibers, and reinforcing fiber bundles such as boron fibers, natural fibers, and modified natural fibers. Among them, carbon fibers (particularly polyacrylonitrile (PAN)-based carbon fibers) are lightweight among these reinforcing fibers, and have particularly excellent properties in terms of specific strength and specific elastic modulus, and are also excellent in heat resistance and chemical resistance, so they are preferred.

[0050] There is no particular limitation on the carbon fiber, and high-strength, high-elastic modulus carbon fibers can be used. One or more of them can be used. Among them, PAN, asphalt, rayon and other carbon fibers can be mentioned. From the perspective of the balance between the strength and elastic modulus of the resulting molded product, PAN carbon fibers are preferred. The density of the carbon fibers is preferably 1.65 to 1.95 g / cm 3 , and more preferably 1.70 to 1.85 g / cm 3 When the density is too high, the lightweight performance of the obtained carbon fiber composite material is poor, and when the density is too low, the mechanical properties of the obtained carbon fiber composite material may become low.

[0051] In addition, from the perspective of productivity, the carbon fiber used in the present invention is preferably a carbon fiber precursor formed by bundling monofilaments, preferably a carbon fiber precursor with a large number of monofilaments in the carbon fiber precursor. For the number of monofilaments when forming the carbon fiber precursor, it is preferably used in the range of 1,000 to 100,000, and particularly preferably in the range of 10,000 to 70,000. For the carbon fiber, a fiberized carbon fiber precursor formed by splitting the carbon fiber precursor into the desired number of filaments using a fiber splitting slitting machine or the like, or a partially fiberized carbon fiber precursor that has been partially fiberized can be cut into a specified length for use. By fiberizing the precursor into the desired number of filaments, the uniformity is improved when the carbon fiber composite material is made compared to the untreated precursor, and the mechanical properties are excellent, so it is a preferred example.

[0052] Here, the so-called partial fiber splitting treatment includes a width expansion treatment and a partial fiber splitting treatment. As the width expansion treatment, for example, a vibration width expansion method in which the reinforcing fiber strands are passed through a vibration roller and the fiber bundles are expanded in the width direction by heating, rubbing, shaking, etc. of each fiber opening rod, and an air width expansion method in which compressed air is blown to the reinforcing fiber bundle, etc. With regard to the width expansion of the reinforcing fiber strands, a preferred example is an expansion ratio of 300 to 1,200%.

[0053] As a partial fiber splitting treatment, the following method is preferably exemplified: for example, while the expanded and reinforced fiber precursor subjected to the above-mentioned expansion treatment is advanced along the length direction (fiber running direction), a rotating fiber splitting mechanism (for example, an iron plate for fiber splitting treatment) having a plurality of protrusions is inserted into the expanded and reinforced fiber precursor to generate a fiber splitting treatment portion, and at the same time, a tangled portion of monofilament interweaving is formed at a portion in contact with the protrusion in at least one fiber splitting treatment portion. Then, the fiber splitting mechanism is pulled out from the expanded and reinforced fiber precursor, and after passing through the tangled storage portion including the tangled portion, the fiber splitting mechanism is inserted into the expanded and reinforced fiber precursor again.

[0054] As the matrix resin used in the present invention, thermoplastic resin and / or thermosetting resin can be used. As the thermoplastic resin, there is no particular limitation, and it can be appropriately selected within the range that the mechanical properties of the molded product are not greatly reduced. For example, polyolefin resins such as polyethylene resin and polypropylene resin, polyamide resins such as nylon 6 resin and nylon 6,6 resin, polyester resins such as polyethylene terephthalate resin and polybutylene terephthalate resin, polyphenylene sulfide resin, polyether ketone resin, polyether sulfone resin, aromatic polyamide resin, etc. can be used. Among them, any one of polyamide resin, polypropylene resin and polyphenylene sulfide resin is preferred.

[0055] As thermosetting resin, there is no particular restriction either, and it can be appropriately selected within the range that the mechanical properties of the molded product are not greatly reduced. For example, epoxy resin, unsaturated polyester resin, vinyl ester resin, phenolic resin, epoxy acrylate resin, urethane acrylate resin, phenoxy resin, alkyd resin, carbamate resin, maleimide resin, cyanate resin, etc. can be used. Among them, any one of epoxy resin, unsaturated polyester resin, vinyl ester resin, phenolic resin or their mixture is preferred. When using a mixture of thermosetting resins, it is preferred that the mixed thermosetting resins have compatibility or high affinity with each other.

[0056] The viscosity of the thermosetting resin used in the present invention is not particularly limited, but the resin viscosity at room temperature (25° C.) is preferably 100 to 100,000 mPa·s.

[0057] In the matrix resin used in the present invention, various additives may be added to the thermoplastic resin and / or the thermosetting resin according to the application as long as the object of the present invention can be achieved. For example, fillers such as mica, talc, kaolin, hydrotalcite, sericite, bentonite, xonotlite, sepiolite, smectite, montmorillonite, wollastonite, silicon dioxide, calcium carbonate, glass beads, glass flakes, glass microspheres, clay, molybdenum disulfide, titanium oxide, zinc oxide, antimony oxide, calcium polyphosphate, graphite, barium sulfate, magnesium sulfate, zinc borate, calcium borate, aluminum borate whisker, potassium titanate whisker and polymer compounds, materials imparting conductivity such as metals, metal oxides, carbon black and graphite powder, halogen flame retardants such as brominated resins, antimony flame retardants such as antimony trioxide and antimony pentoxide, phosphorus flame retardants such as ammonium polyphosphate, aromatic phosphates and red phosphorus, organic acid metal salt flame retardants such as borate metal salts, carboxylic acid metal salts and aromatic sulfonimide metal salts, zinc borate, zinc, zinc oxide and zirconium Inorganic flame retardants such as compounds, nitrogen flame retardants such as cyanuric acid, isocyanuric acid, melamine, melamine cyanurate, melamine phosphate and guanidine nitride, fluorine flame retardants such as PTFE, silicone flame retardants such as polysiloxane, metal hydroxide flame retardants such as aluminum hydroxide and magnesium hydroxide, other flame retardants, flame retardant additives such as cadmium oxide, zinc oxide, cuprous oxide, cupric oxide, ferrous oxide, ferric oxide, cobalt oxide, manganese oxide, molybdenum oxide, tin oxide and titanium oxide, pigments, dyes, lubricants, release agents, compatibilizers, dispersants, crystallization nucleating agents such as mica, talc and kaolin, plasticizers such as phosphate esters, heat stabilizers, antioxidants, anti-coloring agents, UV absorbers, flow modifiers, foaming agents, antibacterial agents, vibration damping agents, deodorants, sliding modifiers and antistatic agents such as polyether ester amides, etc.

[0058] When a thermosetting resin is used as the matrix resin, additives such as a shrinkage reducing agent may be contained within a range that can achieve the object of the present invention.

[0059] The process of obtaining the molding material as a precursor of the reinforced fiber composite material of the present invention is not particularly limited as long as it is within the scope of achieving the purpose of the present invention. For example, in the case of SMC, Figure 3 As shown, a first carrier sheet is pulled out from a first sheet roll 11 and supplied to a conveyor 12, and a matrix resin paste is applied to a predetermined thickness by a doctor blade using a first resin tank 13 to form a first resin sheet 14. The first resin sheet 14 travels on the conveyor 12 at a constant speed.

[0060] The continuous reinforcing fiber raw yarn 22 is pulled out from the bobbin 21, and is continuously cut into a predetermined length in the cutter 23, and then collides with the disperser 24 to generate discontinuous reinforcing fibers including a plurality of discontinuous reinforcing fiber assemblies, which are dispersed on the first resin sheet 14. Thus, an assembly 31 in which discontinuous reinforcing fibers including discontinuous reinforcing fiber assemblies are randomly dispersed is continuously formed on the traveling first resin sheet 14.

[0061] Next, on the downstream side of the continuously formed aggregate 31, a long second carrier sheet is pulled out from the second sheet roll 15, and a second resin sheet 17 is formed on the second carrier sheet surface with a predetermined thickness coated with a matrix resin paste by the second resin tank 16. The second resin sheet 17 is moved at a constant speed by the conveyor 12, and the second resin sheet 17 is attached and laminated in such a manner that the upper surface of the aggregate 31 contacts the surface coated with the matrix resin paste. Through this lamination process, an aggregate 32 partially impregnated with the matrix resin coated on the first resin sheet 14 and the second resin sheet 17 is continuously formed inside the aggregate 31 in which discontinuous reinforcing fibers including discontinuous reinforcing fiber aggregates are randomly dispersed.

[0062] Next, the assembly 32 is pressurized from both sides or one side by a pressurizing mechanism 33 to impregnate the discontinuous reinforcing fibers with the matrix resin (impregnation step), thereby forming a molding material 34 as a precursor of a discontinuous reinforcing fiber composite material between the first carrier sheet and the second carrier sheet. As an example, a step of winding the molding material 34 into a roll together with the first carrier sheet 14 and the second carrier sheet 17 can be cited.

[0063] Here, the cutting machine 23 is not particularly limited as long as it does not hinder the subject of the present invention, and examples thereof include a guillotine type and a disc knife type. The disc knife type refers to a Figure 4As shown, it includes a cutting roller 41, a clamping roller 50, and a traverse guide 51. The cutting roller 41 has a shape in which the blade 42 of a disc knife protrudes at a predetermined interval on the roller surface 40. The clamping roller 50 is arranged approximately parallel to the rotation axis direction of the cutting roller in a manner adjacent to or in contact with the cutting roller, and has a flat surface shape. When the reinforcing fiber precursor 22 is put into the cutting roller 41, the traverse guide 51 guides the reinforcing fiber precursor 22 while reciprocating the reinforcing fiber precursor 22 to the left and right. In order to play the role of an anvil for the cutting roller 41, the roller surface of the clamping roller 50 is preferably made of an elastic material such as rubber or polyurethane.

[0064] In the case of the disc knife type, in order to obtain the arcuate discontinuous reinforcing fiber aggregate (A) of the present invention, for example, as a preferred example, the following situation can be illustrated: when the traverse guide 51 guiding the reinforcing fiber filament 22 reciprocates from right to left or turns back in the opposite direction, the interval of the blade 42 of the disc knife protruding on the surface 40 of the cutting roller around the reinforcing fiber filament 22 is narrower than the width of the reinforcing fiber filament put into the cutting roller. It is further preferred that the following situation can be illustrated as a preferred example, that is, the relationship between the interval of the blade 42 of the disc knife protruding on the surface of the cutting roller and the width of the reinforcing fiber filament is 0.1:1.0 to 0.9:1.0. As another example, the acceleration of the traverse guide guiding the reinforcing fiber filament while reciprocating from left to right can be illustrated as a preferred example when it turns back from right to left or in the opposite direction is 1G (gravitational acceleration) or more.

[0065] Example

[0066] Next, examples and comparative examples of the present invention will be described.

[0067] First, the characteristics and measurement methods used in Examples and Comparative Examples are described.

[0068] (1) Determination of the length of the minimum circumscribed rectangle of a discontinuous reinforcing fiber assembly in the longitudinal direction

[0069] A sample of 150 mm × 150 mm is cut out from a molding material that is a discontinuous reinforced fiber composite material or a precursor, and the cut sample is heated in an electric furnace heated to 500-600°C for about 1-2 hours to burn organic matter such as the matrix resin, and a discontinuous reinforced fiber sheet is taken out from the sample. Using tweezers, etc., the discontinuous reinforced fibers are carefully extracted from the discontinuous reinforced fiber sheet in units of aggregates so that their shapes are not completely destroyed. At this time, the discontinuous reinforced fibers on the cut surface obtained by cutting out the sample in a manner of forming 150 mm × 150 mm are excluded from the measurement object. For the extracted discontinuous reinforced fiber aggregate, place it on a flat table and project it onto a two-dimensional plane using a camera, etc. For the obtained shape, the minimum circumscribed rectangle is obtained, and the lengths of the long side L and the short side W of the minimum circumscribed rectangle are recorded.

[0070] For discontinuous reinforcing fiber assemblies whose short side length W of the minimum circumscribed rectangle is less than 0.5 mm, they are grouped as discontinuous reinforcing fiber assemblies (3) opened to the single filament level. For discontinuous reinforcing fiber assemblies whose short side length W of the minimum circumscribed rectangle is 0.5 mm or more, discontinuous reinforcing fiber assemblies whose long side length L is 30 mm or more are grouped as discontinuous reinforcing fiber assemblies (1), and discontinuous reinforcing fiber assemblies whose long side length L is less than 30 mm are grouped as discontinuous reinforcing fiber assemblies (2).

[0071] When the discontinuous reinforcing fiber sheet cannot be removed smoothly from the discontinuous reinforcing fiber composite material, the same measurement may be carried out using a discontinuous reinforcing fiber sheet not impregnated with the matrix resin.

[0072] (2) Measurement of weight ratio of discontinuous reinforcing fiber assemblies (1) to (3)

[0073] The total weight of the discontinuous reinforcing fiber aggregate (1), the discontinuous reinforcing fiber aggregate (2), and the discontinuous reinforcing fiber aggregate (3) was measured using a balance capable of measuring to 1 / 10,000 g, and the weight ratio Wa of the discontinuous reinforcing fiber aggregate (1) to the total weight of the discontinuous reinforcing fibers, the weight ratio Wb of the discontinuous reinforcing fiber aggregate (2) to the total weight of the discontinuous reinforcing fibers, and the weight ratio Wc of the discontinuous reinforcing fiber aggregate (3) to the total weight of the discontinuous reinforcing fibers were determined using the following formula.

[0074] Wa=W1 / (W1+W2+W3)×100(%)

[0075] Wb=W2 / (W1+W2+W3)×100(%)

[0076] Wc=W3 / (W1+W2+W3)×100(%)

[0077] W1: Total weight of discontinuous reinforcing fiber assembly (1)

[0078] W2: Total weight of discontinuous reinforcing fiber assembly (2)

[0079] W3: total weight of the discontinuous reinforcing fiber assembly (3).

[0080] (3) Method for measuring the number average tip angle θ of discontinuous reinforcing fiber assemblies

[0081] When the discontinuous reinforcing fiber aggregate (1) and the discontinuous reinforcing fiber aggregate (2) were projected onto a two-dimensional plane using a digital microscope (manufactured by Keyence Corporation), the following results were obtained: Figure 5 As shown, a circle with a radius of 2 mm is drawn with the end acute angle vertex as the center, and the end acute angle vertex in the length direction of the discontinuous reinforcing fiber assembly and the point where the circle intersects with the side at this time are connected with a straight line, and the angle formed at this time is taken as the single-side front end angle θ1 of the discontinuous reinforcing fiber assembly. The same measurement is performed for the paired ends, and the average value of the two front end angles (θ1, θ2) is taken as the front end angle θi of each discontinuous reinforcing fiber assembly. However, in the case where the front end shape is significantly deformed and difficult to measure, only one side may be used, and in the case where both sides are difficult to measure, they are excluded from the measurement object.

[0082] Using each of the obtained tip angles θi, the number average tip angle θ is calculated from the following formula.

[0083] Average front angle θ = Σθi / n

[0084] θi: Angle of the tip of each discontinuous reinforcing fiber assembly (1) and (2)

[0085] n: The number of fiber assemblies having the tip angles of each of the discontinuous reinforcing fiber assemblies (1) and (2) is obtained.

[0086] (4) Method for measuring weight ratio and number average obtuse angle α of bow-shaped discontinuous reinforcing fiber aggregate (A)

[0087] The discontinuous reinforcing fiber assemblies (1) and (2) were visually inspected to determine the equivalent Figure 2 All bundles of the bow-shaped discontinuous reinforcing fiber aggregate (A) shown were extracted, and the total weight of the bow-shaped discontinuous reinforcing fiber aggregate (A) was measured using a balance capable of measuring to 1 / 10,000 g, and the weight ratio Wy of the bow-shaped discontinuous reinforcing fiber aggregate (A) was determined using the following formula.

[0088] At this time, if the discontinuous reinforcing fiber assembly (1) contains at least one bundle of the bow-shaped discontinuous reinforcing fiber assembly (A), it is determined as (Yes), and if it does not contain even one bundle, it is determined as (No).

[0089] Wy=W4 / (W1+W2+W3)×100(%)

[0090] W4: The total weight of the arched discontinuous reinforcing fiber assembly (A) present in the discontinuous reinforcing fiber assembly (1) and the discontinuous reinforcing fiber assembly (2).

[0091] Next, using a digital microscope (manufactured by Keyence Corporation), the bow-shaped discontinuous reinforcing fiber aggregates (A) were respectively Figure 6 When projected onto a two-dimensional plane as shown, a circle with a radius of 0.5 mm is drawn with the obtuse vertex as the center, and the angle formed when the obtuse vertex of the region where the number of filaments begins to decrease and the point where the circle intersects the side at this time are connected by a straight line is set as the obtuse angle α1 of the one side of the arched discontinuous reinforcing fiber assembly (A). In the case of a pair of obtuse angles, the same measurement is performed. In the case of one obtuse angle, its value is used directly. In the case of two obtuse angles, the average value of the two obtuse angles is set as the obtuse angle αi of each arched discontinuous reinforcing fiber assembly (A). However, when the obtuse vertex of the region where the number of filaments begins to decrease is unclear, tangents can be drawn on each side, and the point where the extended lines of the tangents intersect is regarded as the obtuse vertex, and the angle formed by the extended lines of the tangents is regarded as the obtuse angle. In the case of difficulty in measurement such as obvious deformation of the end side shape, only one side can be used, and in the case of obvious deformation of both sides, it is excluded from the measurement object.

[0092] The number average obtuse angle α is calculated from the following formula using the obtained obtuse angles αi.

[0093] Number average obtuse angle α=Σαi / m

[0094] αi: Each obtuse angle of the bow-shaped discontinuous reinforcing fiber assembly (A)

[0095] m: The number of fiber assemblies at each obtuse angle of the bow-shaped discontinuous reinforcing fiber assembly (A) is obtained.

[0096] (5) Method for measuring the number average fiber length l of the discontinuous reinforcing fiber assembly (2)

[0097] When each of the above-mentioned discontinuous reinforcing fiber assemblies (2) is projected onto a two-dimensional plane using a digital microscope (manufactured by Keyence Corporation), the two end sides parallel to the fiber orientation direction in the discontinuous reinforcing fiber assembly are measured to 0.1 mm units, and the average value is taken as the fiber length li of each discontinuous reinforcing fiber assembly (2). However, in the case where the measurement is difficult due to obvious deformation of the shape of the end side, only one side may be used, and in the case where both sides are obviously deformed, it may be excluded from the measurement object.

[0098] Using the obtained respective fiber lengths li, the number average fiber length l was calculated from the following formula.

[0099] Number average fiber length l = Σli / p

[0100] li: Length of each fiber in the discontinuous reinforcing fiber assembly (2)

[0101] p: The number of fiber assemblies of each fiber length of the discontinuous reinforcing fiber assembly (2) is obtained.

[0102] (6) Wf (content ratio of discontinuous reinforcing fibers)

[0103] A sample of 150 mm x 150 mm was cut out from the reinforced fiber composite material and its weight was measured. Then, the sample was heated in an electric furnace at 500 to 600°C for about 1 to 2 hours to burn off organic matter such as the matrix resin, and after cooling to room temperature, the weight of the remaining discontinuous reinforcing fibers was measured. The ratio of the weight of the discontinuous reinforcing fibers to the weight of the sample before burning off organic matter such as the matrix resin was measured as the content of the discontinuous reinforcing fibers.

[0104] (7) Flexural strength and flexural modulus

[0105] The bending strength was measured in accordance with JIS-K7171:2016. Regarding the bending strength, the CV value (coefficient of variation [%) of the bending strength was also calculated, and a CV value of 10% or less was judged as a small deviation (OK), and a CV value of more than 10% was judged as a large deviation (NG). In addition, for the samples subjected to the bending test, the arbitrary direction (0° direction) of the two-dimensional plane and the direction of 90° relative to the 0° direction were measured. When the average value in the 0° direction / the average value in the 90° direction fell within the range of 1.2 to 0.83, it was judged to be isotropic (OK), and the other cases were judged to be anisotropic (NG).

[0106] [Reinforcement fiber, matrix resin]

[0107] The reinforcing fibers and matrix resins used in the examples and comparative examples of the present invention are described below.

[0108] Reinforcement fiber precursor (1):

[0109] A continuous carbon fiber precursor having a fiber diameter of 7 μm, a tensile elastic modulus of 230 GPa, a filament number of 12,000, and a precursor width of 6 mm was used.

[0110] Reinforcement fiber precursor (2):

[0111] A continuous carbon fiber precursor having a fiber diameter of 7.2 μm, a tensile elastic modulus of 242 GPa, a filament number of 50,000, and a precursor width of 10 mm was used.

[0112] Base resin (1):

[0113] A resin was used by mixing 100 parts by mass of a vinyl ester resin (VE) resin (Delaken 790, manufactured by Daw Chemika Co., Ltd.), 1 part by mass of t-butyl perbenzoate (Parbul Z, manufactured by NOF Corporation), 2 parts by mass of zinc stearate (SZ-2000, manufactured by Sakai Chemical Industry Co., Ltd.), and 4 parts by mass of magnesium oxide (MgO#40, manufactured by Kyowa Chemical Industry Co., Ltd.).

[0114] Embodiment 1:

[0115] Use as Figure 3 The apparatus shown in the figure produces an SMC sheet as a precursor of a discontinuous reinforced fiber composite material. A first carrier sheet made of polypropylene is pulled out from a first blank roll (first sheet roll) and supplied to a first conveyor, and a matrix resin paste is applied to a predetermined thickness using a scraper to form a first resin sheet.

[0116] A reinforcing fiber precursor (1) is pulled out at a constant speed, and is continuously cut by a disc knife cutter in a manner that the reinforcing fiber precursor (1) is not relaxed but has a predetermined length, so that it collides with a disperser and is dispersed, and a sheet-like discontinuous reinforcing fiber formed by randomly oriented discontinuous reinforcing fibers including a plurality of discontinuous reinforcing fiber assemblies is continuously generated, and is dropped onto a first resin sheet, wherein the disc knife cutter comprises: a traverse guide for guiding the reinforcing fiber precursor while reciprocating the reinforcing fiber precursor to the left and right, a cutting roller having a shape in which the blade of the disc knife protrudes at a predetermined interval on the roller surface, and a clamping roller arranged substantially parallel to the rotation axis direction of the cutting roller in a manner contacting the cutting roller. At this time, the ratio of the pulling speed to the traverse speed is 3.7:1.0, the return distance of the traverse guide is 100 mm, the ratio of the interval between the blades of the disc knife and the width of the reinforcing fiber precursor (1) is 0.4:1.0, and the rotation speed of the distributor is 400 rpm.

[0117] Next, a second carrier sheet made of polypropylene is pulled out from a second raw material roll (second sheet roll) and supplied to a second conveyor, and a matrix resin paste is applied to a predetermined thickness using a doctor blade to form a second resin sheet.

[0118] A second resin sheet is attached and laminated together with a second carrier sheet on a first resin sheet containing a discontinuous reinforcing fiber assembly, and pressurized from both sides to impregnate the matrix resin into the sheet composed of the discontinuous reinforcing fiber assembly, thereby producing an SMC sheet as a precursor of a discontinuous reinforced fiber composite material. As the resulting SMC sheet, the SMC sheet will not flow in the sheet width direction which is perpendicular to the conveying direction during the impregnation process, and an SMC sheet of a specified width can be obtained. Then, the produced SMC sheet is aged at a temperature of 25±5°C for 1 week after manufacture, and various evaluations are performed.

[0119] The obtained SMC sheet was cut into a specified size, and after peeling off the upper and lower carriers, organic matter such as the matrix resin was burned off, and Wf was measured. The result was 55wt%. The remaining discontinuous reinforcing fibers were evaluated in various ways. The results showed that the discontinuous reinforcing fibers contained 6wt% of the bow-shaped discontinuous reinforcing fiber aggregates. The evaluation results are shown in Table 1.

[0120] Next, the SMC sheet was cut into pieces of 265×265 mm, with the conveying direction (MD direction) in the SMC sheet manufacturing device aligned, and three sheets were overlapped and placed in the central portion (equivalent to 80% in terms of charging rate) of a flat plate mold having a cavity of 300×300 mm. Then, the SMC sheet was cured at a temperature of about 140°C for 5 minutes under a pressure of 10 MPa using a heated press molding machine to obtain a flat plate-shaped molded product of 300×300 mm×3 mm.

[0121] The obtained molded product was cut and its bending strength and bending elastic modulus were measured. The bending strength and bending elastic modulus of the molded product were 450 MPa and 33 GPa, respectively. The CV value was less than 10%, and the deviation was small, indicating that the molded product was excellent in isotropy. The evaluation results are shown in Table 1.

[0122] Embodiment 2:

[0123] The same operation as in Example 1 was carried out except that the return distance of the traverse guide was set to 160 mm to obtain an SMC sheet as a precursor of a composite material, to produce a molded product and to carry out evaluation. The results are shown in Table 1.

[0124] Embodiment 3:

[0125] The same operation as in Example 1 was performed except that the reinforcing fiber precursor (2) was used, the return distance of the traverse guide was set to 160 mm, and the ratio of the distance between the blades of the disc knife and the width of the reinforcing fiber precursor (2) was set to 0.24:1.0 to obtain an SMC sheet as a precursor of a composite material. The molded product was manufactured and evaluated. The results are shown in Table 1.

[0126] Embodiment 4:

[0127] The reinforcing fiber precursor (2) is unwound at a constant speed by a winding machine, and the unwound reinforcing fiber precursor (2) is passed through a vibrating widening roller vibrating in the axial direction at 10 Hz to expand the reinforcing fiber bundle, and then passed through a width limiting roller limited to a width of 50 mm, thereby obtaining an expanded reinforcing fiber precursor (2) with an expanded width of 50 mm. Subsequently, a fiber separation treatment mechanism formed by arranging iron plates for fiber separation treatment with a protruding shape of 0.3 mm in thickness, 3 mm in width, and 20 mm in height at equal intervals of 3 mm in the width direction of the expanded reinforcing fiber precursor (2) is intermittently inserted and pulled out, and then passed through a width limiting roller limited to a width of 10 mm, thereby obtaining a partially fiber-split reinforcing fiber precursor (2) with a width limited to 10 mm.

[0128] The partially split reinforcing fiber precursor (2) obtained was used, the return distance of the traverse guide was set to 160 mm, and the ratio of the interval between the blades of the disc knife and the width of the partially split reinforcing fiber precursor (2) was set to 0.24:1.0, and an SMC sheet as a precursor of a reinforcing fiber composite material was obtained. The same operation as in Example 1 was performed to produce a molded product and evaluate it. The results are shown in Table 1.

[0129] Embodiment 5:

[0130] Organic matter such as the matrix resin was burned off on the SMC sheet, and Wf was measured. As a result, the speed of pulling out the carrier sheet and the gap between the scraper and the carrier sheet were adjusted so as to be 45 wt %, and an SMC sheet as a precursor of a reinforced fiber composite material was obtained. Except for this, the same operation as in Example 4 was performed to manufacture a molded product and evaluate it. The results are shown in Table 1.

[0131] Comparative Example 1:

[0132] A first guillotine cutter with a blade obliquely arranged relative to the yarn feeding direction was used in such a manner that the minimum circumscribed rectangle length was 60 mm and the front end cutting angle was 15°, and a second guillotine cutter with a blade obliquely arranged relative to the yarn feeding direction was used in such a manner that the minimum circumscribed rectangle length was 20 mm and the front end cutting angle was 15°, and the reinforcing fiber raw yarn (2) was conveyed in such a manner that the speed ratio of conveying the first guillotine cutter to the second guillotine cutter was 12:88, and the reinforcing fiber raw yarn (2) was continuously cut by each guillotine cutter in such a manner that it was not relaxed and had a predetermined length, and was collided with a disperser (Distributor) and dispersed, and sheet-like discontinuous reinforcing fibers formed by randomly oriented discontinuous reinforcing fibers containing a plurality of discontinuous reinforcing fiber assemblies were continuously generated, and an SMC sheet as a precursor of a composite material was obtained. Except for this, the same operation as in Example 3 was performed to produce a molded product and evaluate it. The results are shown in Table 2.

[0133] The obtained molded product was poor in bending strength and bending modulus. In particular, since the bow-shaped discontinuous reinforcing fiber aggregate was not contained, structural defects formed at the portions where the discontinuous reinforcing fiber bundles overlapped each other were easily generated. Therefore, the CV value exceeded 10%, resulting in a molded product with large variations.

[0134] Comparative Example 2:

[0135] The reinforcing fiber precursor (2) was continuously cut into a predetermined length without slack by using a second guillotine cutter with only one blade obliquely arranged relative to the yarn feeding direction, so that the minimum circumscribed rectangle length was 20 mm and the front end cutting angle was 15°, and the guillotine cutter was used to collide and disperse the reinforcing fiber precursor (2) with a disperser (Distributor), and a sheet-like discontinuous reinforcing fiber containing a plurality of discontinuous reinforcing fiber assemblies was continuously generated in which the discontinuous reinforcing fibers were randomly oriented, thereby obtaining an SMC sheet as a precursor of a composite material. The same operation as in Example 3 was performed except that the above was performed to produce a molded product and evaluate the product. The results are shown in Table 2.

[0136] The obtained SMC sheet flows in the sheet width direction perpendicular to the conveying direction in the impregnation step, and becomes an SMC sheet exceeding a predetermined width.

[0137] The bending strength and bending modulus of the molded product are poor. In particular, the SMC sheet flows in the width direction of the sheet during the impregnation process, so the average value in the 0° direction / the average value in the 90° direction exceeds the range of 1.2 to 0.83, and the molded product is anisotropic.

[0138]

[0139]

[0140] Industrial Applicability

[0141] The reinforced fiber composite material of the present invention can achieve both high fluidity and high mechanical properties during molding, which cannot be achieved by conventional reinforced fiber composite materials formed of discontinuous reinforcing fibers and matrix resins, at a high level, and can suppress the flow of discontinuous reinforcing fibers caused by the flow of the resin when the matrix resin is impregnated into the sheet-like substrate under pressure in the manufacturing process of sheet-like molding materials such as SMC sheets and press-molded sheets as precursors of the composite material.

[0142] Explanation of symbols

[0143] 1 An example of the shape of a bow-shaped discontinuous reinforcing fiber assembly (A)

[0144] 2 An example of the minimum circumscribed rectangle of a bow-shaped discontinuous reinforcement fiber assembly (A)

[0145] L is an example of the length of the long side of the minimum enclosing rectangle

[0146] W An example of the length of the short side of the minimum bounding rectangle

[0147] θ1, θ2 An example of the acute angle of the tip of the discontinuous reinforcing fiber assembly

[0148] α1, α2 An example of the obtuse angle of the discontinuous reinforcing fiber assembly

[0149] 11 An example of the first sheet roll

[0150] 12 An example of a conveyor

[0151] 13 An example of the first resin tank

[0152] 14 An example of a first resin sheet on which a matrix resin paste is applied to a predetermined thickness

[0153] 15 Example of the second sheet roll

[0154] 16 An example of a second resin tank

[0155] 17 An example of a second resin sheet on which a matrix resin paste is applied to a predetermined thickness

[0156] 21 An example of a reinforcing fiber bobbin

[0157] 22 An example of continuous reinforcing fiber precursor

[0158] 23 An example of a cutting machine

[0159] 24 An Example of Distributor

[0160] 31 An example of an assembly of discontinuous reinforcing fibers randomly scattered on the first resin sheet

[0161] 32 An assembly formed by partially impregnating the first resin sheet and the second resin sheet with the matrix resin

[0162] 33 An example of a pressurized mechanism

[0163] 34 An example of a molding material as a precursor for a discontinuously reinforced fiber composite material

[0164] 40 An example of the cutting roller surface of a disc cutter

[0165] 41 An example of a cutting roller for a disc cutter

[0166] 42 An example of the blade of a circular knife

[0167] 50 An example of a clamping roller for a disc cutter

[0168] 51 An example of a traverse guide for a disc cutter

[0169] 60 An example of a discontinuous reinforcing fiber assembly obtained using a disc knife cutter

[0170] 70 An example of a discontinuous reinforcing fiber assembly (2)

[0171] l1, l2 An example of fiber length of discontinuous reinforcing fiber assembly

Claims

1. A fiber-reinforced composite material comprising 20 wt% or more and less than 70 wt% of discontinuous reinforcing fibers and a matrix resin, wherein at least a portion of the discontinuous reinforcing fibers forms a fiber aggregate, At least one bundle of the fiber assembly is an arcuate discontinuous reinforcing fiber assembly (A), and when a certain surface of the arcuate discontinuous reinforcing fiber assembly (A) is projected onto a two-dimensional plane, at each of two ends in the length direction of the minimum circumscribed rectangle of the projection surface and outside the two ends, there are one or more regions where the number of single fibers constituting the fiber assembly is reduced, in, At both ends in the length direction of the minimum circumscribed rectangle of its projection surface, and outside the two ends, there are respectively one or more regions where the number of single fibers constituting the fiber assembly is reduced, which means that there are at least one region at both ends where the number of fibers decreases toward the ends, and another region outside the two ends where the number of fibers decreases from the ends to the center.

2. The reinforced fiber composite material according to claim 1, wherein the fiber assembly in which the length of the long side of the minimum circumscribed rectangle is 30 mm or more is set as the discontinuous reinforcing fiber assembly 1, The discontinuous reinforcing fiber aggregate 1 is formed by 2 wt % or more and 15 wt % or less of the entire discontinuous reinforcing fibers. 3 . The reinforced fiber composite material according to claim 2 , wherein at least one bundle of the discontinuous reinforcing fiber aggregate 1 is a bow-shaped discontinuous reinforcing fiber aggregate (A).

4. The reinforced fiber composite material according to any one of claims 1 to 3, wherein the fiber assembly in which the length of the long side of the minimum circumscribed rectangle is less than 30 mm is set as the discontinuous reinforcing fiber assembly 2, The ratio of "number average minimum circumscribed rectangle long side length: number average fiber length" of the discontinuous reinforcing fiber aggregate 2 is "1.5:1.0" to "2.0:1.0".

5. The reinforced fiber composite material according to claim 2 or 3, wherein when a certain surface of the discontinuous reinforcing fiber assembly 1 is projected onto a two-dimensional plane, the number average angle of the acute angle of the front end portion in the longitudinal direction relative to the longitudinal direction of the projection plane is greater than or equal to 5° and less than or equal to 30°.

6. The reinforced fiber composite material according to claim 4, wherein, for the discontinuous reinforcing fiber aggregate 2, when a certain surface thereof is projected onto a two-dimensional plane, the number average angle of the acute angle of the front end portion in the longitudinal direction relative to the longitudinal direction of the projection plane is greater than or equal to 5° and less than or equal to 30°.

7. According to any one of claims 1 to 3, the reinforced fiber composite material, in the arched discontinuous reinforcing fiber aggregate (A), the inclined surface of the region where the number of single fibers is reduced and exists at a position other than the two end portions, with respect to the length direction of the minimum circumscribed rectangle of the projection plane, forms a number average obtuse angle of 135° or more and 175° or less. 8 . The reinforced fiber composite material according to claim 1 , wherein the number average fiber length of the discontinuous reinforcing fibers is 3 mm or more and less than 100 mm.

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