JP6746446B2 - Fiber reinforced composite - Google Patents

Description

The present invention relates to a fiber-reinforced composite having excellent rigidity and appearance when heated.

Since fiber-reinforced synthetic resin reinforced with fibers is lightweight and has high mechanical strength, in recent years, lightness and high mechanical strength have been demanded in the fields of automobile, ship, aviation, medical, etc. The field of use is expanding.
As a composite having a fiber-reinforced synthetic resin, a fiber-reinforced composite has been proposed in which a foam is used as a core material and the fiber-reinforced resin is laminated and integrated on the surface of the core material (see Patent Documents 1 and 2). ..

JP, 2005-83365, A JP, 2005-313613, A

There is an increasing demand for a fiber-reinforced composite that can withstand use in a higher temperature environment such as the periphery and a shortening of the molding cycle thereof. The fiber-reinforced composites disclosed in Patent Documents 1 and 2 satisfy the above requirements. I haven't been able to.

For example, a composite having a foamed core material made of polypropylene resin has poor rigidity at the time of heating in a 100° C. environment and peeling between the core material and the surface layer material occurs, so that the composite body has sufficient strength. Can't get Further, in a composite having a foam core made of polystyrene resin or polyurethane resin, shrinkage occurs in the core foam under an environment of 100°C. Further, in order to shorten the molding cycle, it is necessary to set the processing temperature to 130 to 150° C., which causes shrinkage of the core material during the molding process, resulting in poor surface appearance.

In addition, in a composite having a foam core made of a polymethacrylimide resin, the foam of the core is excellent in heat resistance, but since the manufacturing method is special, the shape of the foam is limited to a flat plate, The desired shape cannot be obtained, and the appearance of the composite is poor.

Therefore, an object of the present invention is to provide a fiber reinforced composite body which can obtain rigidity in a high temperature environment (for example, 100° C.), an aesthetic appearance, and a surface cosmetic property during high temperature molding. ..

In order to solve the above problems, the present inventors include a polyamide resin, and a specific skin material is disposed on at least a part of the surface of a core material containing a foamed resin having a specific crystallite size and crystallinity. It was found that excellent rigidity, aesthetic appearance, and surface cosmetics at the time of high temperature molding can be obtained by using such a composite, and the present invention has been completed. ..

That is, the present invention is as follows.
(1)
A composite material in which a skin material containing fibers and a resin is arranged on at least a part of the surface of a core material containing a foamed resin, wherein the foamed resin contains a polyamide resin and has the narrowest peak width in an X-ray diffraction profile. A fiber-reinforced composite having a crystallite size D of 10 nm or more and a crystallinity X of 10 to 50% when calculated based on a peak having

(2)
The fiber-reinforced composite according to (1), wherein the foamed resin contains pre-expanded particles.

(3)
The fiber-reinforced composite according to (1) or (2), wherein the polyamide-based resin contains more than 50% by mass of an aliphatic polyamide resin.

(4)
The method for producing a fiber-reinforced composite body according to any one of (1) to (3), characterized in that the core material and the skin material are simultaneously molded by heating and pressurizing.

INDUSTRIAL APPLICABILITY The fiber-reinforced composite of the present invention can provide a fiber-reinforced composite capable of obtaining rigidity in a high temperature environment (for example, 100° C.), an aesthetic appearance, and a surface cosmetic property during high temperature molding. it can.

Hereinafter, modes for carrying out the present invention (hereinafter, also referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and the present invention is not limited to the following embodiments and can be variously modified and implemented within the scope of the gist.

(Fiber reinforced composite)
The fiber-reinforced composite body of the present embodiment is a composite body in which a skin material containing fibers and a resin is arranged on at least a part of the surface of a core material containing a foamed resin.

The foamed resin in the fiber-reinforced composite of the present embodiment contains a polyamide resin, has a crystallite size D of 10 nm or more when calculated based on a peak having the narrowest peak width in an X-ray diffraction profile, and is crystallized. The degree X is 10 to 50%.

In the fiber-reinforced composite of the present embodiment, the portion of the surface of the core material on which the skin material is arranged may be appropriately determined according to the shape of the core material, for example, in the case of a sheet shape (see Examples described later). , May be all or part of one side or both sides, in the case of a block, may be all or part of the surface seen from a specific direction in a stationary state, and in the case of a line, the extending direction from one end May be all or part of the surface for a given length.

-Core material-
The core material in the fiber-reinforced composite body of the present embodiment contains a foamed resin. The core material may include a member other than the foamed resin depending on the purpose and application. From the viewpoint that the characteristics of the foamed resin are easily obtained, the core material is preferably composed of the foamed resin only.

---Foamed resin---
The foamed resin includes a polyamide resin, and may further optionally include other components, a trace amount of gas, and the like.
The foamed resin is preferably a polyamide resin foam containing a polyamide resin.

--- Polyamide resin ---
Examples of the polyamide-based resin include polyamide, polyamide copolymer, and a mixture thereof.

Examples of the polyamide include nylon 66, nylon 610, nylon 612, nylon 46, nylon 1212 and the like obtained by polycondensation of diamine and dicarboxylic acid; nylon 6, nylon 12 and the like obtained by ring-opening polymerization of lactam; Etc. Examples of polyamide copolymers include nylon 6/66, nylon 66/6, nylon 66/610, nylon 66/612, nylon 66/6T (T represents a terephthalic acid component), and nylon 66/6I (I Represents an isophthalic acid component), nylon 6T/6I, and the like. Among them, aliphatic polyamide is preferable, and nylon 6, nylon 66, nylon 6/66, nylon 66/6 and the like are more preferable. These may be used alone or in combination of two or more.

Examples of the mixture include a mixture of nylon 66 and nylon 6, a mixture of nylon 66 and nylon 612, a mixture of nylon 66 and nylon 610, a mixture of nylon 66 and nylon 6I, a mixture of nylon 66 and nylon 6T. And a mixture of nylon 6 and nylon 6I/6T. Among them, from the viewpoint of increasing the crystallinity of the foamed resin and sufficiently improving the heat resistance and the surface beauty of the composite, the polyamide resin in the case of the mixture is preferably one containing more than 50% by mass of the aliphatic polyamide. It is more preferable that the content is 60 mass% or more.

Further, the melting point of the polyamide-based resin is preferably 150° C. or higher, more preferably 180° C. or higher, from the viewpoint of ensuring sufficient heat resistance of the core material and the fiber-reinforced composite. From the viewpoint of improving the fusion rate of the pre-expanded particles in the molding process, it is preferably 270°C or lower, and more preferably 250°C or lower.

In the present specification, the melting point of the polyamide resin refers to a value measured by differential scanning calorimetry (DSC) according to JIS K7121. The endothermic peak that appears in the measurement is taken as the melting peak of the resin, and the temperature at the highest endothermic peak that appears is taken as the melting point.
A commercially available differential scanning calorimeter may be used as the measuring device, and examples thereof include DSC7 manufactured by Perkin Elmer.
As the measurement conditions, usual conditions may be used, for example, under a nitrogen atmosphere, temperature conditions: the resin is kept at a temperature above its melting point (for example, 300° C. for 5 minutes), and then at 20° C./minute at 50° C. The conditions include the rapid cooling to a certain degree, and then raising the temperature above the melting point (for example, 300° C.) at 20° C./min.

A highly reactive functional group (amino group and carboxyl group) at the end of the polyamide resin is converted into a low-reactivity functional group by adding an end-capping agent in the synthesis of the polyamide resin (polyamide resin). Can be blocked).
In this case, examples of the timing of adding the terminal blocking agent include the time of charging the raw materials, the start of polymerization, the latter half of polymerization, or the end of polymerization.
The terminal blocking agent is not particularly limited as long as it is a monofunctional compound capable of reacting with an amino group or a carboxyl group of a polyamide resin, for example, a monocarboxylic acid, a monoamine, an acid anhydride. , Monoisocyanates, monoacid halides, monoesters, monoalcohols and the like. These may be used alone or in combination of two or more.

The shape of the polyamide-based resin is not particularly limited, and examples thereof include beads, pellets, spheres, and irregularly pulverized products, and the size thereof is the size of the pre-expanded particles after foaming. The thickness is preferably 0.2 to 3 mm from the viewpoint of making it moderate, improving the handleability of the pre-expanded particles and making the packing during molding more dense.

--- Other ingredients ---
Other components other than the polyamide-based resin contained in the foamed resin include stabilizers, impact modifiers, flame retardants, lubricants, pigments, dyes, weather resistance improvers, antistatic agents, impact modifiers, crystal nuclei. Agents, glass beads, inorganic fillers, cross-linking agents, nucleating agents such as talc, and other thermoplastic resins may be added within a range that does not impair the object of the present invention. The content of other components in the foamed resin may be 15 parts by mass or less, and preferably 6 parts by mass or less, with respect to 100 parts by mass of the polyamide resin. It is more preferably 3 parts by mass or less.

In particular, the stabilizer is not particularly limited, and examples thereof include hindered phenol antioxidants, sulfur antioxidants, phosphorus antioxidants, phosphite compounds, thioether compounds, and other organic antioxidants. And heat stabilizers; hindered amine-based, benzophenone-based, imidazole-based light stabilizers and ultraviolet absorbers; metal deactivators and the like. These may be used alone or in combination of two or more.

As the heat stabilizer, a copper compound is preferable from the viewpoint of effectively preventing long-term heat aging in a high temperature environment of 120° C. or higher, and a combination of this copper compound and an alkali metal halide compound is also preferable. Here, as the alkali metal halide compound, lithium chloride, lithium bromide, lithium iodide, sodium fluoride, sodium chloride, sodium bromide, sodium iodide, potassium fluoride, potassium chloride, potassium bromide, iodide Examples thereof include potassium. These may be used alone or in combination of two or more.

Examples of other thermoplastic resins include polyolefin resins such as polyethylene, polypropylene, EVA (ethylene-vinyl acetate copolymer); polyvinyl alcohol; polyvinyl chloride; polyvinylidene chloride; polyphenylene ether resin; methacrylic resin; Polycarbonate type resin; Polyimide type resin; Polyacetal type resin; Polyester type resin; Acrylic type resin; Cellulose type resin; Polyvinyl chloride type, polyurethane type, polyester type, 1,2-polybutadiene type, fluoroelastomer type thermoplastic elastomer A polyacetal-based, polyester-based, fluorine-based thermoplastic engineering plastic; and the like. Further, a modified or crosslinked resin may be used as long as the object of the present invention is not impaired.
These may be used alone or in combination of two or more.

The molecule of the polyamide resin is prepared by using a compound or polymer having a substituent (hereinafter, also referred to as a reactive substituent) that reacts with an amino group or a carboxyl group of the polyamide resin contained in the foamed resin. The degree of cross-linking of the polyamide-based resin may be increased by forming a cross-linking structure via such a substituent inside.
Examples of the reactive substituent include a glycidyl group, a carboxyl group, a metal salt of a carboxylic acid, an ester group, a hydroxyl group, an amino group, a functional group such as a carbodiimide group, and the like, and particularly from the viewpoint of reaction speed. , A glycidyl group and a carbodiimide group are preferred.
These may be used alone or in combination of two or more. Further, the compound, the polymer and the like may have plural kinds of functional groups in one molecule.
The amount of the reactive substituent introduced into the polyamide-based resin is preferably such that crosslinking does not cause gelation of the resin.

--- Gas ---
The gas is to be contained in the manufacturing process (described later) of the foamed resin.
The gas is not particularly limited, but examples thereof include air, carbon dioxide gas, various gases used as a foaming agent, and aliphatic hydrocarbon gas.
Specific examples of the aliphatic hydrocarbon-based gas include butane and pentane.

--- Physical properties of foamed resin ---
The physical properties of the foamed resin in the fiber-reinforced composite body of the present embodiment will be described below.

The foamed resin has a crystallite size D of 10 nm or more and a crystallinity X of 10 to 50% when calculated based on the peak having the narrowest peak width in the X-ray diffraction profile.
The X-ray diffraction profile of the foamed resin can be obtained by a transmission method using an X-ray scattering device.

In the foamed resin, the crystallite size D calculated based on the peak having the narrowest peak width in the X-ray diffraction profile improves the heat resistance of the foamed resin or fiber-reinforced composite obtained, and high temperature molding. From the viewpoint of suppressing heat shrinkage at the time, it is 10 nm or more, preferably 11 nm or more, more preferably 12 nm or more, and from the viewpoint of suppressing a decrease in the fusion rate of the obtained foamed resin, The thickness is preferably 50 nm or less, more preferably 40 nm or less.

Further, in the foamed resin, the crystallinity X calculated based on the X-ray diffraction profile is 10 from the viewpoint of suppressing the heat resistance of the foamed resin or the fiber reinforced composite to be obtained and the heat shrinkage during high temperature molding. % Or more, preferably 20% or more, more preferably 25% or more, and 50% or less, 45% from the viewpoint of suppressing a decrease in the fusion rate of the resulting foamed resin. The following is preferable.

式中、βは、結晶由来の回折ピークの半価全幅（ｒａｄ）であり、ｂは、Ｘ線の広がりの半価半幅（ｒａｄ）であり、λは、Ｘ線の波長（単位：ｎｍ）であり、θは、ピーク位置におけるブラッグ角（単位：°）である。
結晶化度Ｘは、下記式（２）で表される式により算出される。

式中、Ａｃｉ（ｉ＝１〜ｎ）は、ピーク分離した際に得られるｎ個の結晶由来の回折ピークの面積であり、Ａａは、ピーク分離した際に得られる非晶由来の回折ピークの面積である。 The crystallite size D and the crystallinity X refer to those obtained as follows.
Here, the X-ray diffraction profile obtained by X-ray diffraction is subjected to peak separation on the assumption of a Gaussian function for the diffraction peaks derived from crystals and the diffraction peaks derived from amorphous.
The crystallite size D is determined by Scherrer's formula represented by the following formula (1).

In the formula, β is the full width at half maximum (rad) of the diffraction peak derived from the crystal, b is the full width at half maximum of the X-ray (rad), and λ is the wavelength of the X-ray (unit: nm). And θ is the Bragg angle (unit: °) at the peak position.
The crystallinity X is calculated by the formula represented by the following formula (2).

In the formula, Aci (i=1 to n) is an area of n crystal-derived diffraction peaks obtained when the peaks are separated, and Aa is an amorphous-derived diffraction peak obtained when the peaks are separated. Area.

Note that although the correction is performed by the optical system in the above formula (1), β is also influenced by the sample shape and the like (sample thickness and the like) other than the optical system. Needless to say, it is necessary to calculate D that does not depend on the measurement conditions by measuring X-ray diffraction under appropriate conditions, performing appropriate correction, and the like.

The density of the foamed resin is 20 kg/m ³ or more from the viewpoint of improving the appearance of the foamed resin or the fiber-reinforced composite by making the strength of the foamed resin moderate and making it difficult for the cell membrane to break. Is more preferable, 50 kg/m ³ or more is more preferable, and 800 kg/m ³ or less is preferable and 500 kg/m ³ or less is further preferable from the viewpoint of enhancing the lightness of the fiber-reinforced composite. preferable.

From the viewpoint that the closed cell rate S of the foamed resin improves the strength of the foamed resin and makes it difficult for water to be taken into the foamed resin that may occur in the open-cell portion, thereby making it difficult to reduce the density of the foamed resin. , 80% or more, and more preferably 85% or more.
The closed cell rate S (%) is calculated by the formula represented by the following formula (3).
S(%)={(Vx−W/ρ)/(Va−W/ρ)}×100
...(3)
In the formula, Vx is the true volume of the foamed resin (cm ³ ), Va is the apparent volume of the foamed resin (cm ³ ), W is the weight of the foamed resin (g), and ρ is , Density of the base resin of the foamed resin (g/cm ³ ).

The foamed resin preferably has a dimensional change rate at 150° C. of 1.5% or less, and more preferably 1.0% or less, from the viewpoint of suppressing deterioration of physical properties and heat shrinkage in a high temperature environment. preferable.
The dimensional change rate refers to a value measured according to JIS K6767 dimensional stability evaluation/method B.

The fusion rate of the foamed resin, from the viewpoint of increasing the rigidity when stress such as bending strain is applied to the composite, and from the viewpoint of suppressing the lack of pre-expanded particles from the molded body when the foamed resin is cut. , 60% or more, more preferably 70% or more, most preferably 80% or more.
The method for measuring the fusion rate is as described in Examples.

-Skin material-
The skin material in the fiber-reinforced composite of the present embodiment includes fibers and resins, and optionally additives and the like.

--- Fiber ---
Examples of the fibers include fibers having high strength and high elastic modulus, and specifically, carbon fibers, glass fibers, and organic fibers (for example, represented by “Kevlar (registered trademark)” manufactured by DuPont, USA). Polyaramid fiber), alumina fiber, silicon carbide fiber, boron fiber, silicon carbide fiber and the like.
Among them, those having a high specific elastic modulus, which is the ratio of the elastic modulus to the density, specifically, carbon fibers are preferable in order to secure the lightness while maintaining the high rigidity.
These fibers may be used alone or in combination of two or more.

The tensile elastic modulus of the fiber in the present embodiment measured according to JIS-K7127 is preferably 200 to 850 GPa from the viewpoint of ensuring high rigidity.

The fiber content in the present embodiment is preferably 40 to 80 mass% with respect to 100 mass% of the skin material.

Basis weight of the fiber in the present embodiment, the rigidity, in terms of weight reduction, the surface of the core material includes a foamed resin is preferably 50~4000g / m ^2, more preferably 100 to 1000 g / m ² is there.

−− Resin−−
Examples of the resin include thermosetting resins and thermoplastic resins. Epoxy resin, phenol resin, cyanate resin, benzoxazine resin, polyimide resin, unsaturated polyester resin, vinyl ester resin, ABS resin, polyethylene terephthalate resin, nylon resin. , Maleimide resin and the like. Among them, a thermosetting resin that is cured by the addition of external energy such as heat, light, or electron beam is preferable, and specifically, an epoxy resin is preferable.
These resins may be used alone or in combination of two or more.

The glass transition temperature of the resin is preferably 80 to 250° C., and more preferably 80 to 180° C., from the viewpoint of adhesion with the core material, deformation and warpage.
The glass transition temperature can be measured by the midpoint method according to ASTM-D-3418.

When the resin is a thermosetting resin, the curing temperature is preferably 80 to 250° C., more preferably 80 to 150° C., from the viewpoint of adhesion to the core material, deformation and warpage.

The content of the resin in the present embodiment is preferably 20 to 60% by mass, and more preferably 30 to 60% by mass with respect to 100% by mass of the skin material, from the viewpoint of adhesiveness to the core material, deformation and warpage. It is 50% by mass.

(Method for producing fiber reinforced composite)
Hereinafter, the method for producing the fiber-reinforced composite body of the present embodiment will be described.

As an example of the method for producing the fiber-reinforced composite body of the present embodiment, a method of simultaneously molding a core material (for example, a core material composed only of a polyamide-based resin foam) and a skin material by heating and pressing in a molding machine Is mentioned.
In the present embodiment, as the polyamide resin foam as the foamed resin contained in the core material, a foamed molded product, bead particles, or the like may be used.

-Method for producing foamed resin-
Examples of the method for producing the foamed resin include an extrusion foaming method, a foam injection molding method, and an in-mold foam molding method (also referred to as a bead foam molding method).

In the extrusion foaming method, an organic or inorganic foaming agent is press-fitted into a resin in a molten state by using an extruder, and the pressure is released at the extruder outlet to have a plate-shaped, sheet-shaped, or columnar shape. This is a method in which the foamed product is obtained, and the foamed product is placed in a mold and heat-processed, or cut and pasted to form a desired shape.

The foam injection molding method is a method in which a resin having foamability is injection-molded and foamed in a mold to obtain a foam-molded article (foam resin) having pores.

The in-mold foam molding method is to fill a foamed resin particle in a mold and heat the same with steam or the like to foam the particles and at the same time heat-bond the particles together to form a foamed molded product (foamed resin). Is the way to get. This in-mold foam molding method has advantages that the product shape can be easily set freely, and a foam molded article having a high expansion ratio can be easily obtained.
The foamed resin is preferably produced by an in-mold foam molding method from the viewpoint of expansion ratio.

Hereinafter, a method for producing pre-expanded particles used when producing the foamed resin will be described. For example, polyamide-based pre-expanded particles can be used when producing a polyamide-based resin foam.
In the present specification, the pre-expanded particles refer to expandable particles (such as beads) that have not been expanded in the final stage.

The pre-expanded particles can be obtained by containing (impregnating) the above-mentioned polyamide resin with a foaming agent to cause foaming.
The method of incorporating (impregnating) the foaming agent into the polyamide resin is not particularly limited and may be a commonly used method.
As such a method, a method of using an aqueous medium in a suspension system such as water (suspension impregnation), a method of using a pyrolytic foaming agent such as sodium bicarbonate (foaming agent decomposition), or a gas having a critical pressure or higher The method of contacting the base resin with the base material resin in the liquid state (liquid phase impregnation), and the method of contacting the base resin with the gas in the gas phase state under the critical pressure (liquid phase impregnation), etc. Can be mentioned. Gas phase impregnation is particularly preferable as the method of incorporating the foaming agent.

In the gas phase impregnation, the solubility of the gas in the resin is higher and the content of the foaming agent is likely to be higher than in the case of suspension impregnation performed under high temperature conditions. Therefore, in the gas phase impregnation, it is easy to achieve a high expansion ratio, and the bubble sizes in the pre-expanded particles are likely to be uniform.

Further, the foaming agent decomposition method is also inconvenient in that it is carried out under high temperature conditions as in the suspension impregnation. Further, in this method, not all of the added pyrolyzable foaming agent becomes a gas, so the amount of gas generated tends to be relatively small. Therefore, the vapor phase impregnation has an advantage that the content of the foaming agent can be easily increased.
Furthermore, in the vapor phase impregnation, the equipment such as the pressure resistance device and the cooling device is likely to be more compact, and the equipment cost is easily reduced, as compared with the case of the liquid phase impregnation.

The conditions for vapor phase impregnation are not particularly limited, and for example, from the viewpoint of more efficiently promoting the dissolution of gas into the resin, the atmospheric pressure is preferably 0.5 to 6.0 MPa. The ambient temperature is preferably 5 to 30°C.

Here, the foaming agent used when producing the pre-expanded particles is not particularly limited, and examples thereof include compounds that can be air or gas.
Examples of the compound that can be used as a gas include inorganic compounds such as carbon dioxide, nitrogen, oxygen, hydrogen, argon, helium, and neon; trichlorofluoromethane (R11), dichlorodifluoromethane (R12), chlorodifluoromethane (R22), tetra Fluorocarbons such as chlorodifluoroethane (R112) dichlorofluoroethane (R141b) chlorodifluoroethane (R142b), difluoroethane (R152a), HFC-245fa, HFC-236ea, HFC-245ca, HFC-225ca; HFO-1234y, HFO-1234ze(E). ) And other hydrofluoroolefins; saturated hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, neopentane; dimethyl ether, diethyl ether, methyl ethyl ether, isopropyl ether, n-butyl ether, diisopropyl ether. , Furan, furfural, 2-methylfuran, tetrahydrofuran, tetrahydropyran and the like; chlorinated hydrocarbons such as methyl chloride and ethyl chloride; alcohols such as methanol and ethanol; and the like.
These air or gas compounds may be used alone or in combination of two or more.

As the foaming agent, those having little influence on the environment and having no flammability or flammability are preferable, and from the viewpoint of safety during handling, an inorganic compound having no flammability and a flammability is further preferable, From the viewpoint of solubility and ease of handling, carbon dioxide gas (carbon dioxide gas) is particularly preferable.

The method of causing foaming in the polyamide resin containing (impregnating) the foaming agent (foaming agent-impregnated polyamide resin) is not particularly limited. For example, the foaming agent-impregnated polyamide resin is changed from a high pressure atmosphere to a low pressure atmosphere. The foaming agent-impregnated polyamide resin is expanded by expanding the gas as a foaming agent dissolved in the foaming agent-impregnated polyamide resin by blowing it into It is possible to use a method of expanding the gas in the system resin to cause foaming, and in particular, the advantage that the size (cell size) of the cells inside the molded article that is the product is uniform, and the expansion ratio. It is preferable to use the latter method of heating/foaming, because the advantage of controlling the temperature and facilitating the production of a molded product having a low expansion ratio can be obtained.

Here, when the pre-expanded particles are expanded to a desired expansion ratio, one-stage expansion may be performed, or multi-stage expansion including secondary expansion and tertiary expansion may be performed. In addition, when multi-stage foaming is performed, it is easy to prepare pre-expanded particles having a high expansion ratio, and the pre-expanded particles used for molding are from the viewpoint of reducing the amount of resin used per unit volume, up to tertiary foaming. The pre-expanded particles obtained are preferably.
In particular, in the case of multi-stage foaming, it is preferable to subject the pre-foamed particles to a gas pressure treatment before the foaming in each stage. The gas used for the pressure treatment is not particularly limited as long as it is inert to the polyamide resin, but the gas is highly safe, and the global warming potential of the gas is small, such as inorganic gas and hydrofluoroolefin. preferable. Examples of the inorganic gas include air, carbon dioxide gas, nitrogen gas, oxygen gas, ammonia gas, hydrogen gas, argon gas, helium gas, neon gas and the like, and examples of the hydrofluoroolefin include HFO-1234y, HFO-1234ze(E) and the like can be mentioned, and in particular, air and carbon dioxide gas are preferable from the viewpoint of easy handling and economical efficiency. The method of pressurizing treatment is not particularly limited, and examples thereof include a method of filling pre-expanded particles in a pressure tank and supplying gas into the tank.

It is preferable that the foamed resin contains the pre-expanded particles (for example, polyamide-based resin pre-expanded particles containing the polyamide-based resin). Can be obtained by doing.

The method for molding the pre-expanded particles is not particularly limited, but for example, the pre-expanded particles are filled in the cavity of the molding die and heated to cause foaming, and at the same time the pre-expanded particles are melted by heat. After deposition, the product can be solidified by cooling and shaped. Here, the method for filling the pre-expanded particles is not particularly limited, for example, a cracking method for filling the pre-expanded particles in a state where the mold is opened a little, a preliminary compression by pressing with the mold closed. Examples include a compression method of filling expanded particles, a compression cracking method of filling the mold with pre-expanded particles that have been compressed and compressed, and then performing the cracking method.

Before filling the pre-expanded particles into the cavity of the molding die, from the viewpoint of applying a constant gas pressure to the bubbles of the pre-expanded particles to make the size (cell size) of the bubbles inside the particles uniform, It is preferable to subject the pre-expanded particles to a pressure treatment with a gas. The gas used for the pressure treatment is not particularly limited, but examples thereof include an inorganic gas from the viewpoint of flame retardancy, heat resistance, and dimensional stability. The method of the inorganic gas and the pressure treatment is the same as the pressure treatment with the gas applied to the pre-expanded particles in the case of multi-stage foaming.

The heat medium used when molding the pre-expanded particles may be a general-purpose heat medium, and is preferably saturated steam or superheated steam from the viewpoint of suppressing oxidative deterioration of the foamed resin, and is uniform with respect to the foamed resin. From the viewpoint of enabling heating, saturated steam is more preferable.

The method for producing the foamed resin includes, for example, a filling step of filling the pre-expanded particles into the cavity of the mold, and supplying steam having a temperature not higher than the heat fusion temperature of the pre-expanded particles to the cavity for 5 to 30 seconds. By a preheating step of preliminarily heating the pre-expanded particles and supplying steam for 20 to 120 seconds or more to the temperature of the heat-sealing temperature of the pre-expanded particles to foam the pre-expanded particles and heat-bond them. And a fusion-bonding step of obtaining a foamed resin are preferable.

Moreover, it is preferable that the foamed resin is obtained by heating the pre-expanded particles in two steps in the preheating step and the fusion step.
According to this method, in the first step, the pre-expanded particles are preliminarily heated with water vapor having a temperature not higher than the heat-sealing temperature of the pre-expanded particles, so that the temperature distribution in the entire aggregate of the pre-expanded particles is made more uniform. be able to. Then, by the preliminary heating in the first step, in the second step, when the pre-expanded particles are heated with steam having a heat fusion temperature or higher, the foaming in the pre-expanded particles becomes more uniform, resulting in the pre-expanded particles. Makes it easier to form a foam.
Further, according to this method, in the obtained foamed resin, the crystallite size of the resin becomes larger, the crystallinity becomes higher, and by extension, the core material having excellent heat resistance can be obtained.

As described above, the temperature at which the pre-expanded particles are heated is preferably in the vicinity of the heat-sealing temperature (Tf) of the pre-expanded particles.
In the present specification, the heat fusion temperature refers to a temperature at which the pre-expanded particles are heated in saturated steam and the pre-expanded particles are fused to each other. The method for measuring the heat fusion temperature is as described below.
The pre-expanded particles are brought into a state in which the pressure inside the bubbles is atmospheric pressure and does not include a blowing agent such as hydrocarbon. 10 g of the pre-expanded particles were placed in a metal mesh container so that the pre-expanded particles were in contact with each other, and then heated with saturated steam at a predetermined temperature for 30 seconds. Then, the lowest temperature (° C.) of the temperatures at which the pre-expanded particles are fused to each other by 80% or more after heating is set as the heat-fusion temperature of the pre-expanded particles.

The heating temperature in the first step is desirably lower than Tf (°C), preferably Tf-20°C or higher, more preferably Tf-15°C or higher, and Tf-2°C. It is preferably below, and more preferably below Tf-5°C.
The heating time in the first stage is preferably 2 seconds or longer, more preferably 3 seconds or longer, further preferably 20 seconds or shorter, and further preferably 15 seconds or shorter.

The heating temperature in the second step is higher than Tf (° C.), preferably Tf+15° C. or lower, more preferably Tf+10° C. or lower, and particularly preferably Tf+5° C. or lower.
The heating time in the second step is preferably 10 seconds or longer, more preferably 15 seconds or longer, further preferably 60 seconds or shorter, and further preferably 45 seconds or shorter.

When the heating temperature and the heating time of the first step and the second step are in the above ranges, the pre-expanded particles can be sufficiently heat-sealed to each other, and the core material in which the crystallization of the resin is further promoted can be obtained. Obtainable.

As the core material, the foamed resin obtained by the above method may be used as the core material. When the core material includes a member other than the foamed resin, examples of the method for manufacturing the core material include a method of laminating a member other than the foamed resin on the foamed resin obtained by the above method. ..

-Preparation process of skin material-
In the skin material preparation step, the resin is impregnated with the fibers by immersing the fibers in the resin in the molten state or spraying the resin in the molten state onto the fibers to obtain the skin material. The skin material may be prepared as a cloth prepreg. The resin may be impregnated with the fibers and then the resin may be cured by light or heat.

In particular basis weight of the fibers in the sheet-shaped surface material is preferably 50~4000g / m ^2, more preferably from 100 to 1000 g / m ^2, for example as a 200 g / m ^2.
When the shape of the fiber-reinforced composite is also sheet-like, it may be as described for the fiber-reinforced composite of the present embodiment.

-Molding process-
In the molding step, the core material and the skin material may be filled in a molding machine in a desired arrangement state and simultaneously molded.
The core material may be further foamed in the molding step.

In this molding step, for example, when a sheet-shaped composite body whose both surfaces are covered with a skin material is manufactured, the sheet-shaped core material is placed between two sheet-shaped skin materials. May be filled in a molding machine, and when producing a lump-shaped composite covered with a skin material, these are filled in the molding machine so that the lump core material is wrapped with a sheet-shaped skin material. Of course, when manufacturing a linear composite covered with a skin material, these may be filled in a molding machine so that the linear core material is wrapped with the sheet-shaped skin material.

In the molding step, first, without pressure, the temperature is maintained at 80 to 150° C., preferably 100 to 120° C. for 0 to 5 minutes, preferably 1 to 3 minutes, and then 0 to 3 MPa. It is preferable to hold at a pressure of 0.1 to 1 MPa and a temperature of 80 to 150° C., preferably 100 to 140° C. for 5 to 30 minutes, preferably 10 to 20 minutes.
As described above, by holding the material under high temperature conditions without applying pressure before pressurizing, it is possible to uniformly apply heat to the skin material and obtain surface smoothness.

Hereinafter, the physical properties of the fiber-reinforced composite body of the present embodiment will be described.
The flexural modulus of the fiber-reinforced composite of the present embodiment measured in accordance with JIS-K7221 under a 100° C. environment is 1 to 50 GPa from the viewpoint of obtaining excellent rigidity in a high temperature environment. Is preferred.

The flexural modulus of the fiber-reinforced composite body of the present embodiment measured in accordance with JIS-K7221 under a 23° C. environment is preferably 1 to 100 GPa from the viewpoint of obtaining excellent rigidity, and It is preferably 10 to 100 GPa.

The flexural strength of the fiber-reinforced composite body of the present embodiment measured in accordance with JIS-K7221 under a 100° C. environment is 10 to 300 MPa from the viewpoint of obtaining excellent rigidity in a high temperature environment. It is more preferably 35 to 200 MPa.

The bending strength of the fiber-reinforced composite body of the present embodiment measured in accordance with JIS-K7221 under a 23° C. environment is preferably 10 to 400 MPa, more preferably from the viewpoint of obtaining excellent rigidity. Is 70 to 300 MPa.

The apparent density of the fiber-reinforced composite body of the present embodiment is preferably 50 to 1000 kg/m ³ . The apparent density of the fiber-reinforced composite means the ratio (W/V) of the mass W of the fiber-reinforced composite to the volume V of the fiber-reinforced composite.

The dimensions of the fiber-reinforced composite body of the present embodiment may be appropriately determined depending on the purpose and application. The skin material may generally have a thickness of 0.1 to 2 mm.

Hereinafter, the present invention will be described based on Examples and Comparative Examples, but the present invention is not limited thereto.

The methods (A) to (F) for measuring the physical properties of the polyamide resin, pre-expanded particles and expanded resin are shown below.

(A) Crystallite size and crystallinity X-ray diffraction (XRD) measurement of the obtained foamed resin was performed by a transmission method using an X-ray scattering device (trade name: NanoViewer, manufactured by Rigaku Corporation). The measurement conditions were: first slit: 0.4 mmφ, second slit: 0.2 mmφ, X-ray wavelength: 0.154 nm, camera length: 78.8 mm. An imaging plate (IP) was used as the detector. A core material sliced to have a sample thickness of about 0.2 mm was used as the sample. The two-dimensional X-ray diffraction pattern obtained by IP was made one-dimensional by the ring average. The empty cell scattering correction was also performed.
Using the software (trade name: Igor Pro Version 6.3.2.3, manufactured by Wavemetrics), the one-dimensional X-ray diffraction profile thus obtained was assumed to be a Gaussian function as a peak shape, and a diffraction peak derived from a crystal was obtained. And a diffraction peak derived from amorphous were separated.
(A-1) Crystallite size Of the peaks obtained by peak separation, the full width at half maximum β (rad) of the peak having the narrowest peak width is calculated, and the full width at half maximum β is used to calculate the above formula (1). ), the crystallite size D of the core material was calculated.
(A-2) Crystallinity The area of each peak obtained by peak separation was calculated, and the crystallinity X of the core material was calculated using the area according to the above formula (2).

(B) Density Regarding the obtained foamed resin, the weight W (kg) was measured, and then the apparent volume Va (m ³ ) of the core material was measured by the water immersion method. Then, the value W/Va (kg/m ³ ) obtained by dividing the weight W by the apparent volume Va was taken as the density of the core material.

(C) Closed cell rate S
The true volume (Vx) of the foamed resin for which the apparent volume Va was measured in (B) above was measured using an air-comparison hydrometer (manufactured by Beckman Co., Ltd.). Then, the closed cell rate S (%) was calculated according to the above-mentioned formula (3).

(D) Fusing rate: A cutting line having a depth of 5 mm is cut into two parts vertically using a cutter knife on the surface of a plate-shaped foamed resin having a length of 300 mm, a width of 300 mm and a thickness of 20 mm. The foamed resin was divided along the line. Regarding the pre-expanded particles appearing on the divided surface, the number (a) of the pre-expanded particles broken in the particles (the pre-expanded particles are broken by the divided surface) and the pre-expanded particles along the interface The number (b) of those that were broken (the interface between the pre-expanded particles was a dividing surface) was measured, and the fusion rate (%) was calculated according to the following formula (4).
Fusion rate (%)={a/(a+b)}×100
...(4)

(E) Melting point The melting point of the polyamide-based resin was measured according to JIS K7121 using a differential scanning calorimeter (trade name: DSC7, manufactured by Perkin Elmer Co., Ltd.). An 8 mg sample was precisely weighed and used for the measurement. Measurement conditions are as follows: under nitrogen atmosphere, temperature condition: 300° C. for 5 minutes, then temperature decrease rate: 20° C./min to 50° C., then temperature increase rate: 20° C./min from 50° C. to 300° C. The temperature was raised.
The peak indicating the endotherm that appeared was taken as the peak indicating the melting of the resin, and the temperature (° C.) at the peak showing the endotherm that appeared on the highest temperature side was taken as the melting point of the polyamide resin.

(F) Thermal Fusion Temperature The obtained polyamide resin pre-expanded particles were put in a state where the pressure inside the cells was atmospheric pressure and did not contain a blowing agent such as hydrocarbon. 10 g of the pre-expanded particles were placed in a metal mesh container so that the pre-expanded particles were in contact with each other, and then heated with saturated steam at a predetermined temperature for 30 seconds. Then, the lowest temperature (° C.) of the temperatures at which the pre-expanded particles were fused to each other by 80% or more after heating was set as the heat-fusion temperature of the pre-expanded particles.

The evaluation methods (1) to (6) of the fiber-reinforced composite bodies of Examples and Comparative Examples described below will be described below.

(1) Bending elastic modulus Based on JIS-K7221, the bending elastic modulus (GPa) of the fiber reinforced composite body obtained by the Example and the comparative example was calculated|required. Specifically, as a standard state, the fiber-reinforced composite body which was left standing in a room controlled at a temperature of 23° C. and a relative humidity of 50% for 24 hours to adjust the state was measured by AUTOGRAPH AG-5000D (manufactured by Shimadzu Corporation). Then, the bending elastic modulus (in an atmosphere of 23° C.) (GPa) was calculated from the formula defined in JIS. In addition, as a standard state, the fiber reinforced composite body was left standing in a room controlled at a temperature of 23° C. and a relative humidity of 50% for 24 hours, and then left in a constant temperature bath at 100° C. for 1 hour to adjust the condition. The composite prepared by allowing the composite to stand in a constant temperature bath at 100° C. for 1 hour and adjusting the condition is subjected to measurement with AUTOGRAPH AG-5000D (manufactured by Shimadzu Corporation) in a 100° C. constant temperature bath, and is defined by JIS. The flexural modulus (under 100° C. atmosphere) (GPa) was calculated from the above.
The results are shown in Table 1.

(2) Bending strength Based on JIS-K7221, the bending strength (MPa) of the fiber-reinforced composite body obtained by the Example and the comparative example was calculated|required. Specifically, as a standard state, the fiber-reinforced composite body which was left standing in a room controlled at a temperature of 23° C. and a relative humidity of 50% for 24 hours to adjust the state was measured by AUTOGRAPH AG-5000D (manufactured by Shimadzu Corporation). Then, the bending strength (in an atmosphere of 23° C.) (MPa) was calculated from the formula defined in JIS. In addition, as a standard state, the fiber reinforced composite body was left standing in a room controlled at a temperature of 23° C. and a relative humidity of 50% for 24 hours, and then left in a constant temperature bath at 100° C. for 1 hour to adjust the condition. In a 100° C. constant temperature bath, it was subjected to measurement with AUTOGRAPH AG-5000D (manufactured by Shimadzu Corp.), and the bending strength (in a 100° C. atmosphere) (MPa) was calculated from the formula defined in JIS.
The results are shown in Table 1.

(3) Appearance (3-1) Surface smoothness The fiber-reinforced composites obtained in Examples and Comparative Examples were subjected to the same conditions as in (1) Measurement of flexural modulus, and as standard conditions, a temperature of 23° C. and a relative humidity of 50. %, and allowed to stand in a room controlled at 24% for 24 hours, then allowed to stand in a constant temperature bath at 100° C. for 1 hour to visually observe the surface of the fiber-reinforced composite, and to observe the surface material and the core material. The adhesive state of was evaluated as follows.
The results are shown in Table 1.
⊚ (excellent): The surface smoothness and the adhesiveness between the skin material and the core material are good.
◯ (Good): The surface smoothness has no problem in practical use, but some floating (blown) was observed between the skin material and the core material.
Poor (poor): Floating is seen between the skin material and the core material, which is a problem in practical use.

(3-2) Surface aesthetics The surface of the fiber-reinforced composites obtained in Examples and Comparative Examples was visually observed, and the state of the surface layer was evaluated as follows.
The results are shown in Table 1.
Good (good): The resin of the skin material is sufficiently cured, and the surface of the fiber-reinforced composite has no resin shortage or unevenness.
Poor (poor): The resin of the skin material penetrated into the core material side, and the surface of the fiber-reinforced composite body was exposed to fibers and had irregular shapes due to lack of resin.

(4) Thickness The thickness (mm) of the fiber-reinforced composites obtained in Examples and Comparative Examples and the total thickness (mm) of the skin material were measured using a caliper.
The results are shown in Table 1.

(5) Apparent Density After measuring the weight W (kg) of the fiber-reinforced composites obtained in Examples and Comparative Examples, three sides of the sheet-shaped fiber-reinforced composite were measured with a caliper, and the volume V( m ³ ) was calculated. The ratio of the weight W to the volume V (W/V) (kg/m ³ ) was used as the apparent density.
The results are shown in Table 1.

(Example 1)
A cross prepreg having a fiber areal weight of 200 g/m ² and a carbon fiber content of 60% by mass, which is composed of carbon fibers having a tensile elastic modulus of 250 GPa and an epoxy resin having a curing temperature of 80° C., is prepared as a skin material. I prepared two.
Next, a polyamide resin foam as a core material was prepared by the following method.
Nylon 6 as polyamide resin (trade name: UBE Nylon 1022B, manufactured by Ube Industries, Ltd.) 100 parts by mass, talc 0.8 parts by mass as a nucleating agent, hindered phenolic antioxidant (Irganox 1098, manufactured by BASF) 0.3 part by mass was melt-kneaded under heating conditions with an extruder, then extruded into a strand, cooled with water in a cold water tank, and cut to prepare a pellet-shaped base resin.
Carbon dioxide gas as a foaming agent was added to the base resin according to the method described in the example of JP2011-105879A. Then, the base resin containing carbon dioxide gas was heated to cause foaming to obtain pre-expanded particles having a density of 300 kg/m ³ .
By sealing the obtained pre-expanded particles in an autoclave and introducing compressed air over 1 hour until the pressure in the autoclave reached 0.5 MPa, and then maintaining the pressure at 0.5 MPa for 24 hours, The pre-expanded particles were subjected to a pressure treatment.
The pre-expanded particles subjected to the pressure treatment were filled in the cavity (cavity dimensions: length: 300 mm, width: 300 mm, height: 3 mm) of the in-mold molding die, and then the mold was clamped. Then, this mold was attached to an in-mold foam molding machine.
Then, 135° C. saturated steam was supplied for 10 seconds into the cavity (first-stage heating), and then 144° C. saturated steam was supplied for 30 seconds (second-stage heating) to produce pre-expanded particles. The pre-expanded particles were molded by foaming and heat-sealing.
The molded body obtained was cooled by supplying cooling water into the cavity of the mold, and then the mold was opened to take out the polyamide resin foam as the core material.
Using the obtained foam as a core material, one skin material was laminated on each of the upper and lower surfaces of the core material, and the laminated body was kept at 100° C. for 3 minutes without applying pressure, By holding for 15 minutes while pressurizing at 0.4 MPa, the skin material and the core material were simultaneously molded to obtain a fiber-reinforced composite. The fiber-reinforced composite had a good flexural modulus and a good appearance both in the standard state and in a high temperature environment of 100°C.
The details of Example 1 are shown in Table 1.

(Example 2)
Production and evaluation were performed in the same manner as in Example 1 except that two skin materials were laminated on each of the upper and lower surfaces.
The fiber-reinforced composite of Example 2 exhibited a flexural modulus superior to that of Example 1.
Details of Example 2 are shown in Table 1.

(Example 3)
A cross prepreg having a fiber areal weight of 200 g/m ² and a carbon fiber content of 60% by mass, which is composed of carbon fibers having a tensile elastic modulus of 250 GPa and an epoxy resin having a curing temperature of 140° C., is prepared as a skin material. Production and evaluation were performed in the same manner as in Example 1 except that two sheets were prepared.
Details of Example 3 are shown in Table 1.

(Example 4)
After obtaining pre-expanded particles having a density of 300 kg/m ^{3 in} the same manner as in Example 1, the pre-expanded particles obtained were enclosed in an autoclave, and compressed air was kept at 1 MPa until the pressure in the autoclave reached 0.3 MPa. It is introduced over a period of time, and then a pressure treatment of maintaining the pressure at 0.3 MPa for 24 hours is performed, and thereafter, by heating at 230° C., further foaming is caused and a density: 150 kg/m 2. except ³ and the point was produced and evaluated in the same manner as in example 1.
Details of Example 4 are shown in Table 1.

(Example 5)
As in Example 4, after obtaining pre-expanded particles having a density of 150 kg/m ³ , the pre-expanded particles obtained were enclosed in an autoclave, and compressed air was supplied until the pressure in the autoclave reached 0.3 MPa. After introducing for 1 hour, the pressure is maintained at 0.3 MPa for 24 hours, and then pressure treatment is performed, and then by heating at 230° C., further foaming is caused, and the density: 60 kg/ Production and evaluation were performed in the same manner as in Example 4 except that m ³ was used.
Details of Example 5 are shown in Table 1.

(Example 6)
Production and evaluation were carried out in the same manner as in Example 1 except that a polyamide resin foam as a core material was prepared by the following method.
As a polyamide resin, nylon 666 (nylon 66/6) (trade name: Novamid 2430A, manufactured by DSM Co., Ltd.) 100 parts by mass, talc 0.8 parts by mass as a nucleating agent, hindered phenolic antioxidant (Irganox 1098, 0.3 parts by mass (manufactured by BASF) was melt-kneaded under heating conditions with an extruder, then extruded into a strand, cooled with water in a cold water tank, and cut to produce a pellet-shaped base resin.
Carbon dioxide gas as a foaming agent was added to the base resin according to the method described in the example of JP2011-105879A. Then, the base resin containing carbon dioxide gas was heated to cause foaming to obtain pre-expanded particles having a density of 300 kg/m ³ .
By sealing the obtained pre-expanded particles in an autoclave and introducing compressed air over 1 hour until the pressure in the autoclave reached 0.4 MPa, and then maintaining the pressure at 0.4 MPa for 24 hours, The pre-expanded particles were subjected to a pressure treatment.
The pressure-treated pre-expanded particles were filled into the cavity (cavity dimensions: vertical length: 300 mm, horizontal length: 300 mm, height: 3 mm) of the in-mold molding die, and then the mold was clamped. Then, this mold was attached to an in-mold foam molding machine.
Thereafter, 105° C. saturated steam was supplied into the cavity for 10 seconds, and then 116° C. saturated steam was supplied into the cavity for 30 seconds to foam the pre-expanded particles and heat-seal the pre-expanded particles. The particles were shaped.
The molded body obtained was cooled by supplying cooling water into the cavity of the mold, and then the mold was opened to take out the polyamide resin foam as the core material.
Details of Example 6 are shown in Table 1.

(Example 7)
Other than using 50 parts by mass of nylon 6 (trade name: UBE nylon 1022B, Ube Industries, Ltd.) and nylon 6I/6T (trade name: Grivory G16, manufactured by EMS) as polyamide resins. Production and evaluation were carried out in the same manner as in Example 4.
Details of Example 7 are shown in Table 1.

(Comparative Example 1)
Production and evaluation were performed in the same manner as in Example 1 except that the pre-expanded particles were molded in one step.
Details of Comparative Example 1 are shown in Table 1.

(Comparative example 2)
Except for using a cross prepreg having a tensile elastic modulus of 250 GPa and an epoxy resin having a curing temperature of 140° C., a fiber basis weight of 200 g/m ² , and a carbon fiber content of 60% by mass. Production and evaluation were performed in the same manner as in Comparative Example 1.
Details of Comparative Example 2 are shown in Table 1.

(Comparative example 3)
Example 7 except that 30 parts by mass of nylon 6 (trade name: UBE nylon 1022B, manufactured by Ube Industries, Ltd.) and 70 parts by mass of nylon 6I/6T (trade name: Grivory G16, manufactured by EMS) were used as the polyamide resin. Production and evaluation were performed in the same manner as in.
Details of Comparative Example 3 are shown in Table 1.

The fiber-reinforced composite body of the present embodiment has excellent rigidity and aesthetic appearance in a high temperature environment such as 100° C., and excellent surface aesthetics during high temperature molding. The fiber-reinforced composite of the present invention can be suitably used particularly in the automobile field.

Claims (4)

At least a part of the surface of the core material containing a foamed resin is a composite in which a skin material containing fibers and a resin is arranged,
The foamed resin contains a polyamide-based resin and has a crystallite size D of 10 nm or more and a crystallinity X of 10 to 50% when calculated based on a peak having the narrowest peak width in an X-ray diffraction profile. is there,
A fiber-reinforced composite characterized by the following. The fiber-reinforced composite according to claim 1, wherein the foamed resin contains pre-expanded particles. The fiber-reinforced composite according to claim 1 or 2, wherein the polyamide-based resin contains more than 50% by mass of an aliphatic polyamide resin. The method for producing a fiber-reinforced composite body according to any one of claims 1 to 3, wherein the core material and the skin material are simultaneously molded by heating and pressurizing.