Fiber-reinforced resin composite and method for producing same

Abstract

To provide a fiber-reinforced resin composite body which is excellent in impact resistance while having lightweight property, and a method for manufacturing the same.SOLUTION: A fiber-reinforced resin composite body has a core sandwich structure including a core layer composed of a thermoplastic resin foam, and skin layers which are arranged on both surfaces of the core layer and are composed of a fiber-reinforced resin, wherein the fiber-reinforced resin contains the same kind of a resin as a thermoplastic resin constituting the thermoplastic resin foam as a matrix, and a ratio (maximum thickness / minimum thickness) of a maximum thickness to a minimum thickness of the skin layer in at least one surface of the core layer is 1.10 or more, or at least one layer in the skin layer is formed of tapes of a plurality of fiber-reinforced resin prepregs aligned in one direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fiber-reinforced resin composite including a core layer made of a thermoplastic resin foam, and a method for producing the same. [Background technology]

[0002] In recent years, fiber-reinforced resin composites have been widely used in various products such as electric and electronic devices, automobiles, airplanes, etc. In particular, in order to improve lightness, Patent Documents 1 to 3 propose fiber-reinforced resin composites with a core sandwich structure in which a core layer made of a thermoplastic resin foam is sandwiched between fiber-reinforced resins. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-207523 [Patent Document 2] Japanese Patent Application Publication No. 2019-72859 [Patent Document 3] Japanese Patent Publication No. 2020-163822 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in fiber-reinforced resin composites having a core sandwich structure including a core layer made of a thermoplastic resin foam, there is a demand for further improvement in impact resistance while maintaining light weight.

[0005] In order to solve the conventional problems, the present invention provides a fiber-reinforced resin composite that is lightweight and has excellent impact resistance, and a method for producing the same. [Means for solving the problem]

[0006] The present invention relates to a fiber-reinforced resin composite having a core sandwich structure including a core layer made of a thermoplastic resin foam and skin layers made of a fiber-reinforced resin arranged on both sides of the core layer, wherein the fiber-reinforced resin uses the same type of resin as the thermoplastic resin constituting the thermoplastic resin foam as a matrix resin, and the ratio of the maximum thickness to the minimum thickness of the skin layer (maximum thickness / minimum thickness) on at least one side of the core layer is 1.10 or more.

[0007] The present invention relates to a fiber-reinforced resin composite having a core sandwich structure including a core layer made of a thermoplastic resin foam and skin layers made of a fiber-reinforced resin arranged on both sides of the core layer, wherein the fiber-reinforced resin uses the same type of resin as the thermoplastic resin constituting the thermoplastic resin foam as a matrix resin, and at least on one side of the core layer, at least one layer in the skin layer is formed from tapes of multiple fiber-reinforced resin prepregs aligned in one direction.

[0008] The present invention relates to a method for producing a fiber-reinforced resin composite, which includes a direct consolidation process in which lamination is performed by directly laminating a fiber-reinforced resin prepreg on at least one surface of a core layer, and integral molding is performed by bonding the core layer and the fiber-reinforced resin prepreg together by heating and pressurizing, wherein the lamination includes lamination by an automated tape lamination method using a fiber-reinforced resin prepreg tape, and wherein the heat fusion temperature of the interface between the core layer and the fiber-reinforced resin prepreg is 150°C or higher during the integral molding. [Effects of the Invention]

[0009] The present invention can provide a fiber-reinforced resin composite that is lightweight and has excellent impact resistance. According to the production method of the present invention, a fiber-reinforced resin composite that is lightweight and has excellent impact resistance can be obtained with good productivity. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic perspective view showing the arrangement of a thermoplastic resin foam and a fiber-reinforced resin prepreg in Example 1. FIG. [Figure 2] FIG. 10 is a schematic perspective view showing the arrangement of a thermoplastic resin foam and a fiber-reinforced resin prepreg in Example 2. [Figure 3] FIG. 10 is a schematic perspective view showing the arrangement of a thermoplastic resin foam and a fiber-reinforced resin prepreg in Example 3. [Figure 4] FIG. 10 is a schematic perspective view showing the arrangement of a thermoplastic resin foam and a fiber-reinforced resin prepreg in Example 4. [Figure 5] FIG. 10 is a schematic perspective view showing the arrangement of a thermoplastic resin foam and a fiber-reinforced resin prepreg in Example 5. [Figure 6] FIG. 10 is a schematic perspective view showing the arrangement of a thermoplastic resin foam and a fiber-reinforced resin prepreg in Example 6. [Figure 7] 1 is a schematic perspective view showing the arrangement of a thermoplastic resin foam and a fiber-reinforced resin prepreg in Comparative Example 1. FIG. [Figure 8] 10 is a schematic perspective view showing the arrangement of a thermoplastic resin foam and a fiber-reinforced resin prepreg in Comparative Example 2. FIG. [Figure 9] 10 is a schematic perspective view showing the arrangement of a thermoplastic resin foam and a fiber-reinforced resin prepreg in Comparative Example 3. FIG. [Figure 10] 10 is a schematic perspective view showing the arrangement of a thermoplastic resin foam and a fiber-reinforced resin prepreg in Comparative Example 4. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] As a result of extensive research into solving the above-mentioned problems, the inventors of the present invention have found that in a fiber-reinforced resin composite having a core sandwich structure including a core layer made of thermoplastic resin foam and skin layers made of fiber-reinforced resin, a fiber-reinforced resin composite that is lightweight and has excellent impact resistance can be obtained by using the same type of resin as the thermoplastic resin that constitutes the thermoplastic resin foam, and (1) making the ratio of the maximum thickness to the minimum thickness of the skin layer (maximum thickness / minimum thickness) on at least one side of the core layer 1.10 or more, or (2) forming at least one layer in the skin layer on at least one side of the core layer from a plurality of fiber-reinforced resin tapes aligned in one direction. In particular, in the present invention, a fiber-reinforced resin composite is obtained by laminating a core layer made of a thermoplastic resin foam and a fiber-reinforced resin prepreg having the same type of thermoplastic resin as the thermoplastic resin constituting the thermoplastic resin foam as a matrix resin, and simultaneously heating and pressurizing the laminate to perform integral molding. More specifically, by applying a direct consolidation process using the ATL (Automated Tape Laying) method, fiber-reinforced resin prepreg tapes of various shapes, each of whose surfaces (one side or both sides) is impregnated with a thermoplastic resin, are laminated onto a thermoplastic resin foam, and then heated and pressurized to perform integral molding. This improves interlayer adhesion between the core layer made of the thermoplastic resin foam and the skin layers made of the fiber-reinforced resin, allowing for a fiber-reinforced resin composite to be obtained with high productivity, lightweight, and excellent impact resistance.

[0012] In this specification, when a numerical range is indicated with "to", the numerical range includes both the upper and lower limits. For example, a numerical range of "x to y" is a range including both the upper and lower limits of the numerical range. Furthermore, when multiple numerical ranges are described in this specification, they are considered to include numerical ranges that combine the upper and lower limits of different numerical ranges as appropriate.

[0013] (fiber reinforced resin composite) A fiber-reinforced resin composite according to one or more embodiments of the present invention has a core sandwich structure and includes a core layer made of a thermoplastic resin foam, and skin layers made of a fiber-reinforced resin with the same type of resin as the thermoplastic resin constituting the thermoplastic resin foam, which are arranged on both sides of the core layer, as a matrix resin.

[0014] (core layer) The thermoplastic resin foam constituting the core layer is not particularly limited, and suitable examples include foams containing one or more thermoplastic resins selected from the group consisting of thermoplastic polyurethane resin, acrylic resin, polyolefin resin, polyvinyl chloride resin, polystyrene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyetherimide resin, polymethacrylimide resin, etc. From the viewpoint of light weight, foams containing one or more thermoplastic resins selected from the group consisting of thermoplastic polyurethane resin, acrylic resin, polyolefin resin, polyetherimide resin, and polymethacrylimide resin are preferred, and from the viewpoints of low cost and excellent moldability, chemical resistance, and electrical insulation, polyolefin resin foams containing polyolefin resins are more preferred, and polypropylene resin foams containing polypropylene resins are even more preferred.

[0015] The polypropylene resin may be a homopolypropylene, which is a homopolymer of propylene, or a copolymer of propylene and another olefin. From the viewpoint of crystallinity and rigidity, the propylene copolymer usually contains 50 to 99 mol %, preferably 55 to 98 mol %, more preferably 60 to 97 mol %, even more preferably 65 to 96 mol %, and particularly preferably 70 to 95 mol % of propylene. The copolymer may be a random polypropylene or a block polypropylene. From the viewpoint of moldability, random polypropylene is preferred.

[0016] Other olefins include α-olefins, cyclic olefins, and dienes. The α-olefins may have 2, 4 to 20 carbon atoms, and specific examples include ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, 1-octene, and 1-decene. Examples of cyclic olefins include cyclopentene, norbornene, and tetracyclo[6,2,11,8,13,6]-4-dodecene. Examples of dienes include 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, and 7-methyl-1,6-octadiene. The other olefins may be used alone or in combination of two or more.

[0017] The polypropylene resin preferably has a melt flow rate (MFR) of 3 to 30 g / 10 min, more preferably 4 to 20 g / 10 min, and even more preferably 5 to 18 g / 10 min. When the MFR of the polypropylene resin is within the above range, the surface appearance of the foamed molded article is improved and productivity is also improved.

[0018] The MFR of polypropylene resins can be measured in accordance with the provisions of JIS K 7210, Method B, with an orifice diameter of 2.0959±0.005 mm, an orifice length of 8.000±0.025 mm, at 230°C, and under a load of 21.2 N (2.16 kgf).

[0019] From the viewpoint of excellent thermoformability, the polypropylene resin may be a modified polypropylene resin modified with a radical polymerizable monomer, i.e., a modified polypropylene resin obtained by graft polymerizing a radical polymerizable monomer onto a polypropylene resin chain. Examples of the radical polymerizable monomer include conjugated diene compounds, aromatic vinyl compounds, ethylenically unsaturated carboxylic acids, epoxy group-containing vinyl compounds, hydroxy group-containing vinyl compounds, vinyl ester compounds, amide compounds, aminoalkyl (meth)acrylate compounds, unsaturated sulfonic acid compounds, and unsaturated phosphoric acid compounds.

[0020] Examples of conjugated diene compounds include 1,3-butadiene, 1,3-pentadiene, isoprene, and chloroprene. These conjugated diene compounds may be used alone or in combination of two or more. Among them, isoprene is preferred because it is liquid, easy to handle, and inexpensive.

[0021] Examples of aromatic vinyl compounds include styrene; methylstyrenes such as o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, β-methylstyrene, dimethylstyrene, and trimethylstyrene; chlorostyrenes such as o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, α-chlorostyrene, β-chlorostyrene, dichlorostyrene, and trichlorostyrene; bromostyrenes such as o-bromostyrene, m-bromostyrene, p-bromostyrene, dibromostyrene, and tribromostyrene; o-fluorostyrene, m-fluorostyrene, and p-fluorostyrene. Examples of aromatic vinyl compounds include fluorostyrenes such as o-nitrostyrene, difluorostyrene, and trifluorostyrene; nitrostyrenes such as o-nitrostyrene, m-nitrostyrene, p-nitrostyrene, dinitrostyrene, and trinitrostyrene; vinylphenols such as o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, dihydroxystyrene, and trihydroxystyrene; divinylbenzenes such as o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene; and diisopropenylbenzenes such as o-diisopropenylbenzene, m-diisopropenylbenzene, and p-diisopropenylbenzene. These aromatic vinyl compounds may be used alone or in combination of two or more. Among these, styrene, methylstyrenes such as α-methylstyrene and p-methylstyrene, divinylbenzene monomers, and divinylbenzene isomer mixtures are preferred because of their low cost.

[0022] Examples of ethylenically unsaturated carboxylic acids include (meth)acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, and isocrotonic acid, as well as their anhydrides and derivatives (e.g., amides, imides, esters, etc.) Examples of ethylenically unsaturated carboxylic acid anhydrides include maleic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, and bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylic anhydride. Examples of the derivatives of ethylenically unsaturated carboxylic acids include (meth)acrylic acid ester compounds, and examples of the (meth)acrylic acid ester compounds include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and octyl (meth)acrylate. Examples of suitable acrylic acid monomers include decyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, stearyl (meth)acrylate, tridecyl (meth)acrylate, lauroyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate. In this specification, "(meth)acrylic acid" refers collectively to acrylic acid and methacrylic acid. In this specification, "(meth)acrylate" refers collectively to acrylate and methacrylate. These monomers may be used alone or in combination of two or more. Among these, from the viewpoints of availability and cost, one or more selected from the group consisting of acrylic acid, methacrylic acid, and maleic anhydride are preferred.

[0023] Examples of epoxy group-containing vinyl compounds include glycidyl compounds such as (meth)acrylate, monoglycidyl maleate, diglycidyl maleate, monoglycidyl itaconate, diglycidyl itaconate, monoglycidyl allyl succinate, diglycidyl allyl succinate, glycidyl p-styrenecarboxylate, allyl glycidyl ether, methallyl glycidyl ether, styrene-p-glycidyl ether, and p-glycidyl styrene; epoxy olefins such as 3,4-epoxy-1-butene and 3,4-epoxy-3-methyl-1-butene; and vinylcyclohexene monoxide. These monomers may be used alone or in combination of two or more. Among these, glycidyl acrylate and / or glycidyl methacrylate are preferred, for example, from the standpoint of availability and cost.

[0024] Examples of hydroxy group-containing vinyl compounds include hydroxyethyl acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl acrylate, lactone-modified hydroxyethyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl acrylate.

[0025] Examples of vinyl ester compounds include vinyl acetate and vinyl propionate.

[0026] Examples of the amide compound include (meth)acrylamide, N-methylol methacrylamide, N-methylol acrylamide, diacetone acrylamide, maleic acid amide, etc. In this specification, (meth)acryl is a general term for acryl and methacryl.

[0027] Examples of the aminoalkyl(meth)acrylate compound include N,N-dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, N,N-dimethylaminopropyl(meth)acrylate, N,N-dipropylaminoethyl(meth)acrylate, N,N-dibutylaminoethyl(meth)acrylate, and N,N-dihydroxyethylaminoethyl(meth)acrylate.

[0028] Examples of the unsaturated sulfonic acid compound include styrene sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid.

[0029] Examples of the unsaturated phosphoric acid compound include mono(2-methacryloyloxyethyl) acid phosphate and mono(2-acryloyloxyethyl) acid phosphate.

[0030] Among the above-mentioned radical polymerizable monomers, it is preferable to use one or more selected from the group consisting of conjugated diene compounds and aromatic vinyl compounds, from the viewpoint of easily obtaining a foam with a low density and a high closed cell content.

[0031] The amount of the radical polymerizable monomer used in the graft polymerization is not particularly limited, but may be, for example, 0.01 to 20 parts by weight, 0.05 to 10 parts by weight, or 0.1 to 5 parts by weight relative to 100 parts by weight of the polypropylene resin.

[0032] The modified polypropylene resin can be obtained by graft polymerizing a polypropylene resin and a radical polymerizable monomer in the presence of a radical polymerization initiator.

[0033] The radical polymerization initiator is not particularly limited, and generally, peroxides, azo compounds, etc. can be used as appropriate. However, initiators capable of abstracting hydrogen from radically polymerizable monomers such as polypropylene resins and conjugated diene compounds are preferred, and general examples thereof include organic peroxides such as ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, and peroxyesters. Among these, initiators with particularly high hydrogen abstraction ability are preferred, and examples thereof include peroxyketals such as 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, n-butyl 4,4-bis(t-butylperoxy)valerate, and 2,2-bis(t-butylperoxy)butane; dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, t-butylcumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl- Examples of the peroxyester include dialkyl peroxides such as 2,5-di(t-butylperoxy)-3-hexyne, diacyl peroxides such as benzoyl peroxide, and peroxyesters such as t-butylperoxyoctate, t-butylperoxyisobutyrate, t-butylperoxylaurate, t-butylperoxy3,5,5-trimethylhexanoate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, t-butylperoxybenzoate, and di-t-butylperoxyisophthalate. These may be used alone or in combination of two or more.

[0034] The amount of radical polymerization initiator used is preferably 0.01 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, per 100 parts by weight of polypropylene resin, from the viewpoints of reactivity and the fluidity and mechanical properties of the modified polypropylene resin.

[0035] The order of addition of the components during the graft polymerization reaction is not particularly limited, but may be, for example, (1) a polypropylene resin, a radical polymerizable monomer, and a radical polymerization initiator may be mixed and then melt-kneaded, (2) a polypropylene resin may be melt-kneaded and then a radical polymerizable monomer or a radical initiator may be mixed simultaneously or separately, all at once or in portions, or (3) a polypropylene resin and a radical polymerization initiator may be melt-kneaded and then a radical polymerizable monomer may be mixed all at once or in portions. From the viewpoint of suppressing deterioration of the mechanical properties of the polypropylene resin, (3) is preferred.

[0036] In the graft polymerization reaction, the melt-kneading temperature is not particularly limited as long as the polypropylene resin melts and the radical polymerization initiator decomposes, but is preferably, for example, 150 to 300° C. Specifically, the melt-kneading time, specifically, the time from the addition of the radical polymerization initiator, is generally preferably 1 to 60 minutes.

[0037] Examples of melt-kneading equipment include kneaders such as rolls, co-kneaders, Banbury mixers, Brabenders, single-screw extruders, and twin-screw extruders; horizontal mixers such as twin-screw surface regenerators and twin-screw multi-disc mixers; and vertical mixers such as double helical ribbon mixers. Among these, it is preferable to use a kneader, and extruders such as single-screw extruders and twin-screw extruders are particularly preferable from the standpoint of productivity. In addition, the melt-kneading may be repeated multiple times to thoroughly and uniformly mix the components.

[0038] The method for producing the polypropylene-based resin foam is not particularly limited, and known techniques such as extrusion foaming, injection foaming, blow foaming, bead foaming, etc. can be appropriately used. Among them, polypropylene-based resin foam produced by the bead foaming method is preferred from the viewpoint of easily obtaining foams with a high expansion ratio.

[0039] Polypropylene-based resin foams produced by the bead expansion method are not particularly limited, but can be produced, for example, by melt-kneading a base resin containing a polypropylene-based resin and a polypropylene-based resin composition containing a blowing agent, extruding the resulting mixture, and then cutting the extruded mixture to produce pre-expanded polypropylene-based resin particles, which are then steam-molded in a mold. The blowing agent is not particularly limited, and physical blowing agents or chemical blowing agents can be used as appropriate, with carbon dioxide being preferred. The polypropylene-based resin composition may optionally contain additives such as cell-forming agents, colorants, antistatic agents, flame retardants, stabilizers such as antioxidants, metal deactivators, phosphorus-based processing stabilizers, UV absorbers, UV stabilizers, fluorescent brighteners, metal soaps, and antacid adsorbents, crosslinking agents, chain transfer agents, lubricants, plasticizers, fillers, and reinforcing materials.

[0040] From the viewpoint of lightness, thermoplastic resin foam has a density of 180 kg / m 3 It is preferable that the density is 30 to 150 kg / m or less. 3 More preferably, 60 to 90 kg / m 3 is more preferable.

[0041] The thickness of the core layer is not particularly limited and may be appropriately set depending on the application of the fiber-reinforced resin composite.

[0042] (skin layer) The fiber reinforced resin constituting the skin layer includes reinforcing fibers and a matrix resin.

[0043] The reinforcing fibers may be any fibers commonly used in fiber-reinforced resins, and are not particularly limited. Examples of reinforcing fibers include inorganic fibers, organic fibers, and metal fibers. Examples of inorganic fibers include carbon fibers, glass fibers, silicon carbide fibers, alumina fibers, Tyranno fibers, basalt fibers, and ceramic fibers. Polyacrylonitrile (PAN)-based, rayon-based, lignin-based, and pitch-based carbon fibers are acceptable, but PAN-based fibers are preferred from the viewpoint of strength. Examples of organic fibers include aramid fibers, polyethylene fibers, polyvinyl alcohol fibers, polyester fibers, polyamide fibers, and polyparaphenylene benzobisoxazole (PBO) fibers. One type of reinforcing fiber may be used alone, or two or more types may be used in combination. Among these, from the viewpoints of light weight and high strength, one or more types selected from the group consisting of carbon fibers, glass fibers, and aramid fibers are preferred, with carbon fibers being more preferred. From the viewpoint of strength, the reinforcing fibers are usually used as continuous fibers (long fibers).

[0044] The matrix resin is not particularly limited as long as it is the same type of resin as the thermoplastic resin constituting the thermoplastic resin foam of the core layer, and those described in the section on thermoplastic resin foam can be used as appropriate. In this specification, "same type of resin" means a resin in which the main component monomer constituting the resin is the same, and the main component monomer constituting the resin means a monomer whose content exceeds 50 mol % when the constituent units of the resin are 100 mol %. The matrix resin is preferably a polypropylene-based resin, similar to the thermoplastic resin constituting the thermoplastic resin foam of the core layer. As the polypropylene-based resin, those described in the section on the core layer can be used as appropriate, and redundant description will be omitted.

[0045] The polypropylene resin used as the matrix resin may include a modified polypropylene resin modified with a radically polymerizable monomer, i.e., a modified polypropylene resin obtained by graft-polymerizing a radically polymerizable monomer onto a polypropylene resin chain, from the viewpoint of enhancing adhesion to the reinforcing fibers. The modified polypropylene resin is preferably a polypropylene resin obtained by polymerizing one or more monomers selected from the group consisting of ethylenically unsaturated carboxylic acids and epoxy group-containing vinyl compounds onto a polypropylene resin chain, from the viewpoint of further enhancing adhesion to the reinforcing fibers. The modified polypropylene resin may be a polypropylene resin obtained by graft-polymerizing, in addition to one or more monomers selected from the group consisting of ethylenically unsaturated carboxylic acids and epoxy group-containing vinyl compounds, any other radically polymerizable monomer. From the viewpoint of enhancing adhesion to the reinforcing fibers and heat moldability, the modified polypropylene resin is preferably a modified polypropylene resin modified with one or more compounds selected from the group consisting of epoxy group-containing vinyl compounds and aromatic vinyl compounds. The ethylenically unsaturated carboxylic acids, epoxy group-containing vinyl compounds, aromatic vinyl compounds, and other radically polymerizable monomers described in the core layer section can be used as appropriate, and redundant description will be omitted. The ethylenically unsaturated carboxylic acid is not particularly limited, but from the viewpoints of availability and cost, one or more selected from the group consisting of acrylic acid, methacrylic acid, and maleic anhydride is preferred. The epoxy group-containing vinyl compound is not particularly limited, but from the viewpoints of availability and cost, glycidyl acrylate and glycidyl methacrylate are preferred. The modified polypropylene resin is not particularly limited, but can be obtained, for example, by the production method explained in the section on the core layer, and redundant explanations will be omitted.

[0046] In the modified polypropylene resin used as the matrix resin, the amount of one or more monomers selected from the group consisting of ethylenically unsaturated carboxylic acids and epoxy group-containing vinyl compounds is not particularly limited. For example, from the viewpoint of adhesion to reinforcing fibers and physical properties, the amount is preferably 0.1 to 20 parts by weight, and more preferably 0.5 to 10 parts by weight, per 100 parts by weight of the polypropylene resin.

[0047] The fiber reinforced resin may be a unidirectional fiber reinforced resin containing reinforcing fibers (continuous fibers) aligned in one direction. The unidirectional fiber reinforced resin may also be a unidirectional fiber reinforced resin sheet in which a unidirectional fiber sheet in which reinforcing fibers (continuous fibers) are aligned in one direction is impregnated with a matrix resin, or a unidirectional fiber reinforced resin tape in which a unidirectional fiber reinforced resin sheet is cut to a predetermined width. In this specification, the term "tape" means a width of 6 to 25 mm. The width of the unidirectional fiber reinforced resin tape may be, for example, 6 to 25 mm, 10 to 20 mm, or 12 to 15 mm. The fiber reinforced resin may also be a fiber woven fabric reinforced resin in which a woven fabric using reinforcing fibers (continuous fibers) as warp and weft threads is impregnated with a matrix resin.

[0048] The skin layer may be one layer or two or more layers. Furthermore, the number of skin layers on both sides of the core layer may be the same or different. From the viewpoint of isotropy of mechanical properties, it is preferable that the skin layers on both sides of the core layer are symmetrically or quasi-isotropically laminated, and it is more preferable that they are symmetrically laminated. Furthermore, one skin layer may be composed of one unidirectional fiber-reinforced resin sheet or fiber woven-reinforced resin, or may be composed of two or more unidirectional fiber-reinforced resin tapes. In this specification, when one skin layer is entirely composed of one fiber-reinforced resin, the fiber-reinforced resin is referred to as a sheet, and when one skin layer is entirely composed of two or more fiber-reinforced resins, the fiber-reinforced resin is referred to as a tape.

[0049] The ratio of the maximum thickness to the minimum thickness (maximum thickness / minimum thickness) of the skin layers on one or both sides of the core layer is 1.10 or more, preferably greater than 1.30. This results in a fiber-reinforced resin composite that is lightweight and has excellent impact resistance. Furthermore, a fiber-reinforced resin composite having convex portions or curved surfaces can be obtained. The upper limit of the ratio of the maximum thickness to the minimum thickness is not particularly limited, but from the viewpoint of lightweight, it is preferably 2.0 or less. The minimum thickness of the skin layer is not particularly limited and may be appropriately set depending on the application, etc., but from the viewpoint of impact resistance, for example, it is preferably 0.16 to 1.12 mm, more preferably 0.33 to 0.99 mm, and even more preferably 0.49 to 0.82 mm. The maximum thickness of the skin layer is not particularly limited and may be appropriately set depending on the application, etc., but from the viewpoint of impact resistance, it is preferably 0.33 to 1.32 mm, more preferably 0.49 to 1.12 mm, and even more preferably 0.66 to 0.99 mm.

[0050] At least one skin layer may be made of two or more fiber-reinforced resin tapes aligned in one direction, and more preferably, at least one skin layer is made of two or more unidirectional fiber-reinforced resin tapes aligned in one direction, thereby obtaining a lightweight fiber-reinforced resin composite with excellent impact resistance.

[0051] It is preferable that the area of ​​the lamination surface of at least one of the skin layers is different from the area of ​​the lamination surface of the core layer, which makes it easier to obtain a fiber-reinforced resin composite having a three-dimensional shape with convex portions and curved portions.

[0052] Furthermore, when the skin layer has two or more layers, from the viewpoints of impact resistance and productivity, the laminate may be configured as an angle-ply laminate in which two or more layers of unidirectional fiber-reinforced resin are laminated at any angle. The difference (absolute value) between the angles of the unidirectional fibers contained in the two layers of unidirectional fiber-reinforced resin is preferably 10 to 90°, more preferably 30 to 90°, and particularly preferably 45 to 90°. From the viewpoint of improving impact resistance, the laminate is preferably configured as a cross-ply laminate of two or more layers of unidirectional fiber-reinforced resin. In the cross-ply laminate, the angle between the fibers of adjacent skin layers is 90°. Each skin layer is preferably configured from a unidirectional fiber-reinforced resin fiber sheet or a plurality of unidirectional fiber-reinforced resin tapes arranged in one direction. From the viewpoint of further improving impact resistance, the unidirectional fiber-reinforced resin fiber sheet or the unidirectional fiber-reinforced resin tape is preferably a unidirectional carbon fiber-reinforced resin fiber sheet or a unidirectional carbon fiber-reinforced resin tape, respectively.

[0053] In one or more embodiments of the present invention, from the viewpoint of excellent impact resistance, the fiber-reinforced resin composite preferably has an absorbed energy of 30 J or more, more preferably 35 J or more, even more preferably 40 J or more, and particularly preferably 45 J or more, measured in a ball drop test under conditions of a load energy of 100 J. The upper limit of the absorbed energy is not particularly limited.

[0054] (Applications of fiber reinforced resin composites) In one or more embodiments of the present invention, the fiber-reinforced resin composite has light weight and excellent impact resistance, and therefore can be used in a variety of products such as electrical and electronic devices, automobiles, and airplanes. In particular, a fiber-reinforced resin composite having a three-dimensional shape with uneven or curved surfaces can be suitably used in thin-walled impact-resistant structures that require rigidity, such as suitcases.

[0055] (Method of manufacturing fiber-reinforced resin composite) In one or more embodiments of the present invention, the method for producing a fiber-reinforced resin composite is not particularly limited, and any known method that can produce a fiber-reinforced resin composite having a core sandwich structure including a core layer made of a thermoplastic resin foam and skin layers made of a fiber-reinforced resin and disposed on both sides of the core layer can be used as appropriate.

[0056] The fiber-reinforced resin composite can be produced, for example, by laminating a fiber-reinforced resin prepreg on at least one side of a core layer, and performing integrated molding in which the core layer and the fiber-reinforced resin prepreg are bonded together by heating and pressurizing.

[0057] The method for producing a fiber-reinforced resin composite preferably includes a direct consolidation process, which allows for highly productive production of a fiber-reinforced resin composite in which at least one surface of the core layer has a ratio of maximum thickness to minimum thickness (maximum thickness / minimum thickness) of 1.10 or more, or in which at least one skin layer is formed from a plurality of fiber-reinforced resin tapes aligned in one direction.

[0058] In the direct consolidation process, lamination is performed by directly laminating a fiber-reinforced resin prepreg on at least one surface of a core layer, and integral molding is performed by laminating the core layer and the fiber-reinforced resin prepreg together by applying heat and pressure.

[0059] Fiber-reinforced resin prepregs can be produced using known prepreg production equipment that impregnates reinforcing fibers with a thermoplastic resin material. Preferably, the prepreg is produced by laminating one or more layers of a thermoplastic resin film containing a thermoplastic resin that will serve as a matrix resin on one or both sides of a unidirectional fiber sheet in which reinforcing fibers (continuous fibers) are aligned in one direction or a woven fabric using reinforcing fibers (continuous fibers) as warp and weft yarns, and then applying heat and pressure to impregnate the fiber sheet with the thermoplastic resin. The thickness of the thermoplastic resin film is not particularly limited and can be appropriately set based on the basis weight of the unidirectional fiber sheet or woven fabric, the desired fiber content of the fiber-reinforced resin prepreg, and the like, but may be, for example, 30 to 80 μm.

[0060] The fiber reinforced resin prepreg is not particularly limited, but from the viewpoint of further improving the mechanical properties and light weight of the fiber reinforced resin composite, the fiber volume content is preferably 30 to 60 volume %. From the viewpoint of further improving the mechanical properties and light weight of the fiber reinforced resin composite, the fiber reinforced resin prepreg has a weight per unit area of ​​150 to 300 g / m 2 It is preferable that the thickness is 200 to 250 g / m 2 The thickness of the fiber reinforced resin prepreg is not particularly limited and may be set appropriately depending on the application, etc., but may be, for example, 0.15 to 0.20 mm or 0.16 to 0.18 mm from the viewpoint of lamination workability.

[0061] From the viewpoints of productivity and ease of obtaining a fiber-reinforced resin composite having a three-dimensional shape, the lamination preferably includes lamination by an automatic tape lamination method using a fiber-reinforced resin prepreg tape. The fiber-reinforced resin prepreg tape is not particularly limited, but from the viewpoint of ease of lamination by the automatic tape lamination method, it is preferable that the tape has a thickness of 0.15 to 0.20 mm, a width of 6 to 25.0 mm, and a length (lengthwise size) of 10 to 100 m, and more preferably a thickness of 0.16 to 0.18 mm, a width of 12.5 to 25.0 mm, and a length (lengthwise size) of 50 to 100 m.

[0062] In the direct consolidation process, a tape of fiber-reinforced resin prepreg is laminated on at least one surface of the core layer by an automated tape lamination method, while simultaneously applying heat and pressure using a compaction roller or the like, thereby laminating and integrating the core layer and the fiber-reinforced resin prepreg into an integrated molding.

[0063] In the integral molding, the heat fusion temperature at the interface between the core layer and the fiber-reinforced resin prepreg is preferably 150°C or higher, more preferably 170 to 230°C, and even more preferably 190 to 230°C. This allows the core layer and the fiber-reinforced resin prepreg to be firmly integrated, and the mechanical properties of the fiber-reinforced resin composite, such as impact resistance, tend to be improved. Furthermore, in the integral molding, the pressure is preferably 0.1 to 1.0 N, more preferably 0.2 to 0.8 N, and even more preferably 0.4 to 0.6 N. Specifically, when a compaction roller is used for the integral molding, the pressing force is preferably 100 to 300 N, more preferably 150 to 300 N, and even more preferably 200 to 300 N.

[0064] When two or more layers of fiber reinforced resin prepregs are laminated, the heat fusion temperature at the interface between the fiber reinforced resin prepregs is preferably 150° C. or higher, more preferably 170 to 230° C., and even more preferably 190 to 230° C. This allows the core layer and the fiber reinforced resin prepreg to be firmly integrated, and mechanical properties such as impact resistance of the fiber reinforced resin composite are likely to be improved.

[0065] The integrated molding can include hot melt molding using a thermoforming method comprising a heat and cool press. For example, when a unidirectional sheet-like and / or woven fiber reinforced resin prepreg is used as the fiber reinforced resin prepreg, the thermoforming method comprising a heat and cool press can be used to place two or more layers of fiber reinforced resin prepreg in a mold set to a predetermined temperature, heat the mold, heat-seal the layers of the fiber reinforced resin prepreg, and then cool the mold to a predetermined temperature. After that, a thermoplastic resin foam constituting a core layer is laminated on one side of the integrated two or more layers of fiber reinforced resin prepreg, and pressure is applied simultaneously with the start of cooling to integrate the core layer and the skin layer. [Example]

[0066] Hereinafter, one embodiment of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0067] In the examples and comparative examples, the test methods and evaluation criteria used for various evaluations are as follows:

[0068] <Skin layer thickness> A 5 cm square was cut out from the center of the fiber-reinforced resin composite using a diamond cutter and embedded in epoxy resin. Next, the cross section of the fiber-reinforced resin composite was exposed using the diamond cutter and polished using a polishing machine (MINITECH223, manufactured by Presi). The cross section was then observed using a digital microscope (VHX-200, manufactured by Keyence Corporation) to measure the thickness of the skin layer.

[0069] <Impact resistance> For the impact resistance test, a sample cut into 60 mm square from the center of the fiber-reinforced resin composite was used, and a drop weight test was conducted using a drop ball impact tester (INSTRON "CEAST 9350 model") with a striker diameter of φ20 mm, load energy of 100 J, and impact speed of 6.1 m / s. The amount of energy (J) absorbed in the elastic range during a 100J impact was measured, and impact resistance was evaluated according to the following criteria. The amount of energy absorbed in the elastic range was calculated by numerically integrating the area from the origin to the peak load in an impact load (y-axis) vs. displacement (x-axis) diagram. If the impact resistance rating is B or higher, the product has excellent impact resistance. A:50J or more B: 30J or more but less than 50J C: 25J or more but less than 30J D: Less than 25J

[0070] <Lightweight> The basis weight of the fiber-reinforced resin composite was calculated by dividing the mass of the obtained fiber-reinforced resin composite by its area (150 cm length × 150 cm width), and the lightness was evaluated according to the following criteria. If the lightness was judged to be C or higher, the composite was deemed to be lightweight. A: 2,000g / m 2 below B: 2,000g / m 2 More than 2,500g / m 2 less than C: 2,500g / m 2 More than 3,000g / m 2 less than D: 3,000g / m 2 End

[0071] <Core layer made of thermoplastic resin foam> The core layer is made of a thermoplastic resin foam, (a) has an expansion ratio of 5 to 6 times, (b) has dimensions of 150 mm length x 150 mm width x 6 mm thickness, and (c) has a basis weight of 975±25 g / m 2 A polypropylene resin foam molded article ("Eperan-PP (registered trademark) LBS05" manufactured by Kaneka Corporation, a random copolymer of propylene and α-olefin, melting point 143°C, MFR 8g / 10min) was prepared by the bead foaming method.

[0072] <Fiber-reinforced polypropylene prepreg manufacturing example 1> 100 parts by weight of homopolypropylene (Prime Polypro J106G, manufactured by Prime Polymer Co., Ltd.) and 0.5 parts by weight of 1,3-di(t-butylperoxyisopropyl)benzene (Perbutyl P, manufactured by NOF Corporation) were fed into the hopper of a twin-screw extruder (HK-25D(61D); L / D=61, manufactured by Parker Corporation) set at 200°C and melt-kneaded. Then, a mixture of 5 parts by weight of glycidyl methacrylate (GMA) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 5 parts by weight of styrene monomer (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was injected into the cylinder midway and melt-kneaded to obtain pellets of modified polypropylene. 30 parts by weight of the resulting modified polypropylene pellets (melting point 161°C, MFR 53g / 10min) and 70 parts by weight of random polypropylene (random copolymer of propylene and α-olefin, melting point 133°C, MFR 24g / 10min, "Y-2045GP" manufactured by Prime Polymer Co., Ltd.) were dry blended, and the mixture was fed into the hopper of a twin-screw extruder (HK-25D; L / D=41, manufactured by Parker Corporation) set at 180°C and melt-kneaded to obtain mixed polypropylene pellets A. The obtained pellets A were fed into a T-die extrusion film molding machine (L / D=26) to obtain a film A having a thickness of 45 μm. The obtained film A and PAN-based carbon fiber ("T710-24K" manufactured by Toray Industries, Inc.) were fed into a prepreg manufacturing device and prepreg-shaped with a width of 300 mm, a thickness of 230 μm, and a basis weight of 240 g / m 2 A unidirectional carbon fiber reinforced polypropylene prepreg 1 having a fiber volume content of 52% was obtained. This 300 mm wide unidirectional carbon fiber reinforced polypropylene prepreg 1 was slit to a width of 25 mm to obtain a UD tape. Furthermore, this 300 mm wide unidirectional carbon fiber reinforced polypropylene prepreg 1 was slit to a width of 150 mm to obtain a unidirectional carbon fiber reinforced polypropylene prepreg 2.

[0073] <Fiber-reinforced polypropylene prepreg manufacturing example 2> 30 parts by weight of modified polypropylene pellets obtained in the same manner as in Production Example 1 and 70 parts by weight of random polypropylene (a random copolymer of propylene and α-olefin, melting point 135°C, MFR 27 g / 10 min, "F329RA" manufactured by Prime Polymer Co., Ltd.) were dry-blended, and the mixture was supplied to the hopper of a twin-screw extruder (HK-25D; L / D=41, manufactured by Parker Corporation) set at 180°C and melt-kneaded to obtain mixed polypropylene pellets B. The obtained pellets B were fed into a T-die extrusion film molding machine (L / D=26) to obtain a film B having a thickness of 45 μm. The obtained film B and a carbon fiber plain weave cloth ("Torayca (registered trademark) Kuro CO6343B" manufactured by Toray Industries, Inc.) were fed into a continuous press machine to form a film having a thickness of 250 μm and a basis weight of 280 g / m. 2and a 3K plain weave carbon fiber reinforced polypropylene prepreg (hereinafter also referred to as 3K plain weave cloth-containing CFRTP) having a fiber volume content of 55%.

[0074] Example 1 Using an automatic tape laminating machine, the UD tape obtained in Production Example 1 was arranged over the entire surface of both sides of the above-mentioned 150 mm square polypropylene resin foam, so as to form a symmetrical lamination with an orientation angle of (90° / 0° / 90°) as shown in Figure 1 and Table 1. Each prepreg layer was formed by arranging six UD tapes in the same direction. One UD tape obtained in Production Example 1 was partially laminated in the center of the outermost layer on both sides, over an area of ​​25 mm wide x 150 mm long, so as to form a symmetrical lamination with an orientation angle of 0°. Here, the orientation angle is the angle with respect to the longitudinal direction Y of the polypropylene resin foam Z constituting the core layer, as shown in Figure 1. The same applies below. During lamination of the UD tape, the interface between the core layer and the unidirectional fiber-reinforced polypropylene prepreg, as well as between the layers of unidirectional fiber-reinforced polypropylene prepreg, were bonded together by laser-controlled heating of the surface to 230°C and heating and pressurizing with a pressing force of 300N using a compaction roller, and the mixture was allowed to cool naturally to room temperature (20±5°C) to obtain a fiber-reinforced resin composite.

[0075] Example 2 Using an automatic tape laminating machine, the UD tape obtained in Production Example 1 was arranged over the entire surface of both sides of the polypropylene-based resin foam described above, so as to form a quasi-isotropic symmetric lamination with orientation angles of (45° / 90° / 135°) as shown in Figure 2 and Table 1. The 90° prepreg layer was formed by arranging six UD tapes in the same direction. The 45° and 135° prepreg layers were each formed by arranging nine UD tapes in the same direction. One UD tape obtained in Production Example 1 was partially laminated in the center of the outermost layer on both sides, covering an area of ​​25 mm wide x 150 mm long, so as to form a quasi-isotropic symmetric lamination with an orientation angle of 0°. Otherwise, a fiber-reinforced resin composite was obtained in the same manner as in Example 1.

[0076] Example 3 Using an automatic tape laminating machine, the UD tape obtained in Production Example 1 was arranged on the entire surfaces of both sides of the above-mentioned polypropylene-based resin foam so as to form a symmetrical lamination with an orientation angle of (0° / 90° / 0° / 90°) as shown in FIG. 3 and Table 1. Each prepreg layer was formed by arranging six UD tapes in the same direction. One UD tape obtained in Production Example 1 was partially additionally laminated in the center of the outermost layer on both sides over an area of ​​25 mm wide x 150 mm long so as to form a symmetrical lamination with an orientation angle of 90°. Otherwise, a fiber-reinforced resin composite was obtained in the same manner as in Example 1.

[0077] Example 4 Using an automatic tape laminating machine, the UD tape obtained in Production Example 1 was arranged in an area of ​​75 mm wide x 150 mm long at the center of both sides of the polypropylene-based resin foam, so as to form a symmetric lamination with orientation angles of (0° / 90° / 0° / 90° / 0° / 90° / 0°) as shown in FIG. 4 and Table 2. Each prepreg layer was formed by arranging three UD tapes in the same direction. One UD tape obtained in Production Example 1 was arranged in the center of the outermost layer on both sides, so as to form a symmetric lamination with an orientation angle of 90°, and an additional area of ​​25 mm wide x 150 mm long was partially laminated. Otherwise, a fiber-reinforced resin composite was obtained in the same manner as in Example 1.

[0078] Example 5 Using an automatic tape laminating machine, the UD tape obtained in Production Example 1 was arranged in an area of ​​100 mm wide x 150 mm long at the center of both sides of the above-mentioned polypropylene-based resin foam so as to form a symmetric lamination with an orientation angle of (90° / 0° / 90°) as shown in Figure 5 and Table 2. Each prepreg layer was formed by arranging four UD tapes in the same direction. One UD tape obtained in Production Example 1 was arranged in the center of the outermost layer on both sides, and an additional area of ​​25 mm wide x 150 mm long was partially laminated to form a symmetric lamination with an orientation angle of 0°. Otherwise, a fiber-reinforced resin composite was obtained in the same manner as in Example 1.

[0079] Example 6 Using a digital servo press (ZEN Former MPS675DS, manufactured by HODEN Precision Processing Laboratory Co., Ltd.) equipped with a high-speed heat and cool press molding machine (Go Molding System, GMS, manufactured by Go Seisakusho Co., Ltd.), two layers of the 3K plain weave carbon fiber reinforced polypropylene prepreg obtained in Production Example 2 were laminated onto both surfaces of the above-mentioned polypropylene resin foam, as shown in FIG. 6 and Table 2. Specifically, a laminate formed by laminating two layers of 3K plain weave carbon fiber reinforced polypropylene prepreg (150 mm length × 150 mm width) obtained in Production Example 2 was placed in a mold set at a mold temperature of 220°C and heated, and after the layers were heat-sealed, the mold was cooled to a mold temperature of around 200°C, and then a polypropylene resin foam was placed on the two integrated layers of prepreg, and the clearance between the top and bottom of the mold was closed to 6.1 mm and the press was held, and cooling began immediately.When the mold had cooled to 50°C, the product with the one-sided skin layer formed was removed from the mold.To form a skin layer on the other side, the same procedure was performed except that the clearance between the top and bottom of the mold was set to 6.3 mm, and skin layers were formed on both sides of the core layer. Next, using an automatic tape laminating machine, one UD tape obtained in Production Example 1 was arranged side by side at the center of the outermost layers on both sides of the obtained laminate, and an additional layer of 25 mm wide x 150 mm long was partially laminated thereon so as to form an orientation angle of 0°, as shown in Figure 6. Otherwise, a fiber-reinforced resin composite was obtained in the same manner as in Example 1.

[0080] (Comparative Example 1) Using an automatic tape laminating device, the UD tapes obtained in Production Example 1 were arranged on the entire surfaces of both sides of the above-mentioned polypropylene-based resin foam so that the orientation angles were (0° / 0° / 0° / 0°), as shown in Fig. 7 and Table 3. Each prepreg layer was formed by arranging six UD tapes in the same direction. Otherwise, a fiber-reinforced resin composite was obtained in the same manner as in Example 1.

[0081] (Comparative Example 2) Using an automatic tape laminating device, the UD tape obtained in Production Example 1 was arranged on the entire surfaces of both sides of the above-mentioned polypropylene-based resin foam so that there were four layers on each side, with a mixture of orientation angles of (0°) and (90°) in the same plane, as shown in Fig. 8 and Table 3. Otherwise, a fiber-reinforced resin composite was obtained in the same manner as in Example 1.

[0082] (Comparative Example 3) Using a digital servo press (ZEN Former MPS675DS, manufactured by HODEN Seimitsu Kako Kenkyusho Co., Ltd.) equipped with a high-speed heat and cool press molding device (Go Molding System, GMS, manufactured by Go Seisakusho Co., Ltd.), four layers of the unidirectional carbon fiber reinforced polypropylene prepreg 2 obtained in Production Example 1 were laminated onto the entire surfaces of both sides of the above-mentioned polypropylene resin foam, as shown in FIG. 9 and Table 3. Specifically, a laminate formed by laminating four layers of the unidirectional carbon fiber reinforced polypropylene prepreg 2 (150 mm long x 150 mm wide) obtained in Production Example 1 was placed in a mold set at a mold temperature of 220°C and heated. After the layers were thermally fused together, the mold was cooled to a mold temperature of approximately 200°C. A polypropylene resin foam was placed on top of the four integrated layers of unidirectional carbon fiber reinforced polypropylene prepreg 2, and the mold was pressed and held with the clearance between the top and bottom of the mold closed to 6.6 mm. Cooling was then immediately initiated. Once cooled to 50°C, the prepreg layer with a one-side skin layer formed was removed from the mold. Each prepreg layer was formed by arranging four unidirectional carbon fiber reinforced polypropylene prepreg 2 in the same direction. The formation of the skin layer on the other side was performed in the same manner, except that the clearance between the top and bottom of the mold was set to 7.3 mm. Skin layers were formed on both sides of the core layer, and a fiber-reinforced resin composite was obtained.

[0083] Comparative Example 4 As shown in FIG. 10 and Table 3, a fiber-reinforced resin composite was produced in the same manner as in Comparative Example 3, except that a skin layer was formed using a laminate of two layers of 3K plain weave carbon fiber-reinforced polypropylene prepreg obtained in Production Example 2 instead of a laminate of four layers of unidirectional carbon fiber-reinforced polypropylene prepreg 2 (150 mm long x 150 mm wide) obtained in Production Example 1.

[0084] For the fiber reinforced resin composites of the Examples and Comparative Examples, the thickness of the skin layer, impact resistance, and lightness were measured and evaluated as described above, and the results are shown in Tables 1 to 3 below.

[0085] [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] As can be seen from Tables 1 and 2 above, the fiber reinforced resin composites obtained in the Examples were lightweight and had a three-dimensional shape with excellent impact resistance. On the other hand, as can be seen from Table 3 above, the fiber reinforced resin composites of the Comparative Examples were poor in impact resistance. [Explanation of symbols]

[0089] A~H Fiber reinforced resin prepreg (skin layer) Z Thermoplastic resin foam (core layer) X horizontal direction Y vertical direction

Claims

1. A fiber-reinforced resin composite having a core sandwich structure including a core layer made of a thermoplastic resin foam and skin layers made of a fiber-reinforced resin arranged on both sides of the core layer, The fiber reinforced resin uses the same type of resin as the thermoplastic resin constituting the thermoplastic resin foam as a matrix resin, At least on one surface of the core layer, the ratio of the maximum thickness to the minimum thickness of the skin layer (maximum thickness / minimum thickness) is 1.10 or more; A fiber-reinforced resin composite having an absorbed energy of 30 J or more measured under a load energy of 100 J in a ball drop test.

2. A fiber-reinforced resin composite having a core sandwich structure including a core layer made of a thermoplastic resin foam and skin layers made of a fiber-reinforced resin arranged on both sides of the core layer, The fiber reinforced resin uses the same type of resin as the thermoplastic resin constituting the thermoplastic resin foam as a matrix resin, At least one of the skin layers is formed from a plurality of fiber-reinforced resin prepreg tapes arranged in one direction on at least one surface of the core layer, A fiber-reinforced resin composite having an absorbed energy of 30 J or more measured under a load energy of 100 J in a ball drop test.

3. The fiber reinforced resin composite according to claim 2, wherein the fiber reinforced resin prepreg tape has a width of 6 mm or more and 25 mm or less and a thickness of 0.15 to 2.0 mm.

4. The fiber-reinforced resin composite according to any one of claims 1 to 3, wherein the area of ​​the lamination surface of at least one skin layer among the skin layers is different from the area of ​​the lamination surface of the core layer.

5. The fiber-reinforced resin composite according to any one of claims 1 to 4, wherein the thermoplastic resin constituting the core layer and the skin layer is a polypropylene-based resin.

6. 6. The fiber-reinforced resin composite according to claim 5, wherein the thermoplastic resin constituting the skin layer is a modified polypropylene-based resin modified with one or more compounds selected from the group consisting of epoxy group-containing vinyl-based compounds and aromatic vinyl compounds.

7. The fiber-reinforced resin composite according to any one of claims 1 to 6, wherein the skin layer is an angle-ply laminate of carbon fiber reinforced resin containing carbon fibers aligned in one direction.

8. The method for producing a fiber-reinforced resin composite according to any one of claims 1 to 7, The method includes a direct consolidation process in which a fiber reinforced resin prepreg is directly laminated on at least one surface of a core layer, and an integrated molding process in which the core layer and the fiber reinforced resin prepreg are bonded together by heating and pressurizing are simultaneously performed, a method for producing a fiber-reinforced resin composite, wherein the lamination includes lamination by an automated tape lamination method using a fiber-reinforced resin prepreg tape, and in the integrated molding, a heat fusion temperature at the interface between the core layer and the fiber-reinforced resin prepreg is 150°C or higher.

9. 9. The method for producing a fiber-reinforced resin composite according to claim 8, wherein the integral molding in which the core layer and the fiber-reinforced resin prepreg are bonded together by heating and pressurizing includes hot melt molding by a thermoforming molding method using a heat and cool press.

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