JP7201512B2 - Fiber reinforced sheet and manufacturing method thereof - Google Patents

Description

The present invention relates to a fiber-reinforced sheet containing carbon fiber bundles.

In general, a fiber-reinforced sheet exhibits high performance by impregnating a reinforcing fiber bundle with a resin and integrating the resin and the reinforcing fiber.

Thermosetting resins, thermoplastic resins, and the like can be used as resins impregnated into the reinforcing fiber bundles. High-molecular-weight thermosetting resins and general thermoplastic resins have high melt viscosities. It is not easy to impregnate a reinforcing fiber bundle with a resin having a high melt viscosity. For this reason, it is not easy to mold fiber-reinforced sheets into various shapes, and in particular, it is not easy to mold large-sized fiber-reinforced sheets.

In Patent Document 1 below, a base material portion made of a resin-unimpregnated portion is provided with at least one rib portion, and the rib portion is made of a surface layer made of a carbon fiber reinforced thermoplastic resin composite and a thermoplastic resin. A fiber reinforced sheet is disclosed comprising a core portion. Further, paragraph 110 discloses that the resin of the core may have air bubbles for weight reduction.

International Publication No. 2017-056683

As a result of investigation, the present inventors found that when attempting to manufacture a fiber-reinforced sheet having a rib length of 1 m or more by extrusion molding using the fiber-reinforced sheet described in Patent Document 1, There is a problem that warping occurs in the longitudinal direction of the fiber reinforced sheet due to the tension generated by shrinkage of the thermoplastic resin, and a problem that the adhesion between the base material and the core is insufficient due to the warping, resulting in a decrease in mechanical strength. I found

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a long fiber-reinforced sheet that is less warped and has excellent mechanical strength, and a method for producing the same.

As a result of intensive studies, the present inventors have found that by setting the expansion ratio to an amount corresponding to the amount of shrinkage of the thermoplastic resin contained in the core portion, while suppressing the deterioration of mechanical properties due to the use of the foamed thermoplastic resin. , can improve the warpage of fiber reinforced sheets. That is, the gist of the present invention is as follows.

[1] At least one rib portion containing carbon fiber and thermoplastic resin is provided on the base portion,
a skin portion in which the rib portion is made of a carbon fiber reinforced thermoplastic resin composite;
A fiber-reinforced sheet comprising a core portion made of a thermoplastic resin,
A fiber-reinforced sheet, wherein the resin foaming ratio of the core portion is 1.05 to 2.0 times.

[2] The fiber-reinforced sheet according to [1], wherein the base material portion includes a resin-unimpregnated fiber bundle portion or a partially resin-impregnated portion having a surface not impregnated with resin.

[3] The fiber-reinforced sheet of [1] or [2], wherein the base material includes either a glass mat layer or a glass roving layer.

[4] The fiber-reinforced sheet according to any one of [1] to [3], wherein the base material is partially impregnated with an unsaturated polyester resin.

[5] The fiber-reinforced sheet according to any one of [1] to [4], wherein the thermoplastic resin of the core portion contains hollow acrylic particles.

[6] The fiber-reinforced sheet according to any one of [1] to [5], wherein the carbon fiber-reinforced thermoplastic resin composite of the skin portion is a prepreg sheet containing unidirectional continuous fibers.

[7] The fiber-reinforced sheet according to any one of [1] to [6], wherein the rib portion has a width of 0.3 to 2 cm, a height of 0.3 to 7 cm, and a length of 10 cm or more. .

[8] The fiber-reinforced sheet according to any one of [1] to [7], wherein, in the cross-sectional shape of the rib portion perpendicular to the longitudinal direction, the vertex of the rib portion has a curved shape.

[9] A method for producing a fiber-reinforced sheet, comprising:
a carbon fiber reinforced thermoplastic resin composite;
A thermoplastic resin composition containing 0.1 to 4 parts by mass of a foaming agent with respect to 100 parts by weight of the thermoplastic resin;
a base material;
to form at least one convex portion on the surface of the substrate portion.

[10] The method for producing a fiber-reinforced sheet according to [9], wherein the mold temperature during extrusion molding is 200 to 240°C.

[11] The first protective layer forming solution comprises a first liquid containing a modified silicone resin and an epoxy curing agent, and a second liquid containing an epoxy resin and a modified silicone polymerization catalyst. The surface protection method according to any one of [7] to [10], comprising the step of mixing with a liquid agent to prepare a first protective layer forming solution.

The fiber-reinforced sheet of the present invention is preferably used as a partitioning member (sheer web) for structures such as windmills, etc., because the molded article does not warp and the adhesive strength between the substrate and the rib portion is excellent.
In addition, if the base material is made of a material that has excellent interfacial adhesion strength with an adhesive, the mechanical strength of the target object can be improved by bonding the fiber reinforced sheet to the concrete structure, metal structure, or resin structure. be able to.
More specifically, the fiber-reinforced sheet of the present invention is adhered to the pillars and walls of existing buildings to improve earthquake resistance, and the fiber-reinforced sheet is adhered to the structural parts of ships, trains, automobiles, and the like. and can be made lighter than conventional structural members.

FIG. 1 is a front cross-sectional view showing a fiber-reinforced sheet according to a first embodiment of the invention. FIG. 2 is a perspective view showing a fiber-reinforced sheet according to the first embodiment of the invention.

An example of a preferred mode for carrying out the present invention will be described below with reference to the drawings. However, the following embodiments are examples for explaining the present invention, and the present invention is not limited to the following embodiments.

<1. Fiber Reinforced Sheet>
FIG. 1 is a diagram for explaining an embodiment of a fiber-reinforced sheet 1. FIG. As shown in FIG. 1 , the fiber-reinforced sheet 1 has a sheet-shaped base portion 10 and a plurality of rib portions 11 provided on the base portion 10 . The rib portion 11 is composed of a core portion 13 covered with a skin portion 12 on the surface side.

FIG. 2 is a perspective view of a fiber-reinforced sheet. The plurality of rib portions 11 are arranged in the first direction d1 along the base portion 10 . Each rib portion 11 extends linearly in a second direction d2 along the base portion 10 orthogonal to the first direction d1. That is, the fiber reinforced sheet 1 is formed so that the linear rib portion 11 extends in a direction perpendicular to the longitudinal direction (first direction d1) of the fiber reinforced sheet 1. As shown in FIG. Therefore, between two rib portions 11 adjacent to each other in the arrangement direction, there is a layer composed of the base portion 10 without the rib portion 11 .

Although the length of the fiber-reinforced sheet of the present invention is not particularly limited, it is usually 10 cm or longer, preferably 50 cm or longer, more preferably 100 cm or longer, and still more preferably 200 cm or longer, from the viewpoint that the longer the sheet, the more likely warpage occurs. It is usually 50 m or less, preferably 10 m or less, more preferably 5 m or less.

<2. Base Material>
In the fiber-reinforced sheet 1 of the present invention, the thickness of the base material portion 10 is not particularly limited, but is usually preferably 2.0 cm or less, more preferably 1.0 cm or less, and particularly preferably 0.5 cm or less. . When the thickness of the base material portion 10 is not uniform, the average thickness of the entire base material portion is taken as the thickness.

The base material portion 10 of the present invention is not particularly limited as long as it is a material that can be adhered to the rib portion. For example, resin sheets containing thermoplastic resins and thermosetting resins; metal sheets such as iron and aluminum; glass sheets, fibrous substrates made of glass fibers and carbon fibers; A fibrous base material is preferable from the viewpoint of adhesive strength with a resin, and a fibrous base material containing glass fibers is more preferable from the viewpoint of cost. Moreover, the base material part 10 may be composed of one layer or two or more layers.

For example, the form of the fibrous base material containing glass fibers may be surface mat, glass mat, glass cloth, or roving cloth. A cloth is preferred, and a roving cloth is more preferred.

From the viewpoint of adhesion to the rib portion and mechanical strength of the base portion, the base portion 10 of the present invention may contain two or more glass fiber layers, and includes at least a glass cloth layer and a roving cloth layer. is more preferable. More preferably, the layer in contact with the rib portion is provided with a glass cloth layer. Further, in order to reduce the appearance and scattering of glass fibers (skin irritation), the glass roving layer may have a structure of three or more layers, and glass cloth layers may be used on both sides of the glass roving layer.

The base member 10 of the present invention may be impregnated with resin or may have a non-impregnated portion. , The substrate portion 10 preferably has a resin non-impregnated portion, and more preferably, the surface opposite to the surface of the substrate portion 10 provided with the rib portion 11 is not resin-impregnated, and the bonding surface with the rib portion and the fiber layer It is more preferable that the resin is not impregnated in places other than the adhesive surface.

When the base material is impregnated with a resin, the resin to be used includes, for example, thermoplastic resins such as polyolefin resins, polyester resins and polyamide resins, and thermosetting resins such as phenol resins and epoxy resins. Polyolefin resins, polyester resins, and epoxy resins are preferably used from the viewpoint of adhesives with glass fibers, polyester resins are more preferable, and unsaturated polyester resins are still more preferable.

<3. Rib part>
In the fiber-reinforced sheet 1 of the present invention, the height of the rib portion 11 provided on the base material portion 10 is preferably such that the fiber-reinforced sheet 1 does not bend in the second direction d2. Specifically, it is usually 0.3 cm or more, preferably 0.8 cm or more, more preferably 1.2 cm or more, and particularly preferably 2.0 cm or more, and the upper limit is not particularly limited, but it is usually 7 cm or less, preferably 5.1 cm. Below, more preferably 4.0 cm or less, still more preferably 3.0 cm or less.

When the height of the rib portion 11 is within the above range, the fiber reinforced sheet 1 has high bending strength against stress in the direction perpendicular to the second direction d2. The height of the rib portion 11 is the length measured from the surface of the base portion 10 where the rib portion 12 is not present to the surface of the skin portion 12 present at the apex portion of the rib portion 11 .

The width of the rib portion 11 can be arbitrarily adjusted according to the height of the rib portion, but is usually 0.3 cm or more, preferably 0.5 cm or more, more preferably 0.8 cm or more, and particularly preferably 0.8 cm or more. It is 1.0 cm or more, and although the upper limit is not particularly limited, it is usually 5.0 cm or less, preferably 3.0 cm or less, and more preferably 2.0 cm or less.

When the width of the rib portion 11 is within the above range, the fiber reinforced sheet 1 has high bending strength against stress in the direction perpendicular to the second direction d2. The width of the rib portion 11 is the length measured from the surface of the base portion 10 where the rib portion 12 is not present to the surface of the skin portion 12 present at the apex portion of the rib portion 11 .

In addition, the length of the rib portion 11 is usually 10 cm or more, preferably 50 cm or more, more preferably 100 cm or more, and still more preferably 200 cm or more, from the viewpoint that the longer the rib portion 11 is, the more likely it is to warp. is 10 m or less, more preferably 5 m or less.

When manufactured by extrusion molding, there is substantially no upper limit to the length, and the length may be cut according to the intended use.

<4. Skin>
The rib portion 11 of the present invention preferably includes a skin portion 12 and a core portion 13, with the skin portion 12 being the outer layer and the core portion 13 being the core layer. The skin portion 13 is made of a carbon fiber-reinforced thermoplastic resin composite containing carbon fibers and a thermoplastic resin, and is preferably a prepreg sheet in which the carbon fibers are impregnated with the thermoplastic resin.

(4.1 carbon fiber)
Examples of carbon fibers used for the skin portion 13 of the present invention include PAN-based carbon fibers and PITCH-based carbon fibers, and PAN-based carbon fibers are preferably used. The average diameter of the carbon fibers is preferably 4 µm or more, more preferably 6 µm or more. Also, the average diameter of the carbon fibers is preferably 30 μm or less, more preferably 20 μm or less. In the present invention, the average diameter is the arithmetic mean value of the fiber diameters of 100 randomly selected carbon fibers. In addition, the fiber diameter refers to the diameter of a cross section (substantially circular) in a cross section along a direction perpendicular to the length direction of the fiber.

Each carbon fiber is generally a single fiber (filament), and a plurality of carbon fibers together form a carbon fiber bundle (tow). Carbon fiber bundles are preferably used.

The number of carbon fibers constituting each carbon fiber bundle (the number of filaments contained per strand) is usually 1,000 or more, preferably 3,000 or more, more preferably 12,000 or more, and still more preferably 24,000. Although the upper limit is not particularly limited, it is usually 100,000 or less, preferably 50,000 or less, more preferably 48,000 or less, and particularly preferably 30,000 or less.

In general, as the number of filaments in a carbon fiber bundle increases, the mechanical properties and resin impregnability per filament tend to decrease, but the price per unit weight of the carbon fiber bundle also decreases. Carbon fiber bundles with filament counts can be selected.

When using carbon fiber bundles, when using unidirectional continuous fibers, the number is preferably 48,000 or more and 100,000 or less, and when using woven carbon fiber bundles, the number is preferably 12,000 or more and 48,000 or less.

Carbon fiber bundles may be used in various forms. For example, unidirectional continuous fibers in which a plurality of fiber bundles are oriented in one direction (UniDirection fibers), woven fabrics formed by weaving a plurality of fiber bundles, knitted fabrics formed by knitting fiber bundles, and a plurality of fibers It may be used in the form of a non-woven fabric made of bundles and thermoplastic resin fibers. Among these, unidirectional continuous fibers and woven fabrics are preferred, and woven fabrics having high mechanical properties in the longitudinal and transverse directions are more preferred. The woven fabric may be woven by plain weave, twill weave, satin weave, or the like, and isotropic plain weave or twill weave is preferable. Moreover, as the knitted fabric, a non-crimp fabric in which fibers are arranged in a straight manner in each fiber orientation direction is preferable.

The basis weight of the carbon fiber fabric is usually 20-800 g/m ² , preferably 100-40 g/m ² . When the basis weight of the carbon fiber bundle is 20 g/m ² or more, the mechanical strength of the fiber-reinforced composite material formed from the spread carbon fiber bundle of the present invention is improved. Further, when the basis weight of the carbon fiber bundle is 800 g/m ² or less, the carbon fibers can be uniformly impregnated with the matrix resin, and the mechanical strength of the fiber-reinforced composite material is improved. The basis weight is more preferably 150-300 g/m ² .

(4.2 Thermoplastic resin)
Examples of thermoplastic resins contained in the skin portion 12 include polyolefin resins, acrylic resins, polyamide resins, polycarbonate resins, vinyl chloride resins, aromatic polyether ketones, etc., which affect impregnation between fibers. Polyolefin resins with a good balance of viscosity and mechanical properties, vinyl chloride resins with high viscosity but excellent chemical resistance, and aromatic polyether ketones with good heat resistance are preferred. Polyolefin-based resins include, for example, polyethylene-based resins and polypropylene-based resins.

The polypropylene-based resin is not particularly limited, and examples thereof include propylene homopolymers and copolymers of propylene and other olefins. Copolymers of propylene and other olefins may be either block copolymers or random copolymers. Examples of olefins to be copolymerized with propylene include α- - olefins and the like.

Examples of the aromatic polyether ketone include polyether ether ketone, polyether ketone ketone, etc. Polyether ether ketone is preferably used from the viewpoint of heat resistance and mechanical properties.

(4.3 Carbon fiber reinforced thermoplastic resin composite)
The carbon fiber-reinforced thermoplastic resin composite preferably contains the above-described carbon fibers and a thermoplastic resin, and is a prepreg sheet in which the carbon fibers are impregnated with the thermoplastic resin. These prepreg sheets may be laminated for use.

The orientation of the carbon fibers contained in the carbon fiber reinforced thermoplastic resin composite may be unidirectional carbon fibers only, or prepregs containing unidirectional carbon fibers are arranged in different orientations and It may be laminated, or biaxially oriented carbon fibers such as woven fabric may be used.

The carbon fiber content in the carbon fiber reinforced thermoplastic resin composite is preferably 10 to 70% by volume, more preferably 20 to 60% by volume, and even more preferably 30 to 50% by volume. In the fiber-reinforced composite material, the content of the matrix resin is preferably 30-90% by volume, preferably 40-80% by volume, more preferably 30-60% by volume.

The method for impregnating the carbon fiber with the thermoplastic resin is not particularly limited. For example, a method of extruding a molten resin into a film using a sheet die or the like, laminating it on carbon fibers, and then compressing while heating to impregnate the carbon fibers with a thermoplastic resin (film impregnation method), or a method of extruding a thermoplastic resin from a die Examples include an extrusion molding method in which a resin and carbon fibers are pulled out at once, and a film impregnation method is preferably used from the viewpoint of productivity.

(5. Core part)
The core portion 13 of the present invention is made of a foamed thermoplastic resin having an expansion ratio of 1.05 to 2.0 times. The expansion ratio is preferably 1.1 times or more, more preferably 1.15 times or more, while the upper limit is preferably 1.8 times or less, more preferably 1.6 times or less, and further preferably 1.5 times or less. 1.3 times or less is particularly preferable.

When the foaming ratio of the resin contained in the core portion is within the above range, it is possible to suppress warping due to resin shrinkage in the core portion and a decrease in adhesiveness to the substrate while maintaining the mechanical strength of the rib portion.

The thermoplastic resin constituting the core portion of the present invention has the function of improving the mechanical strength of the fiber reinforced sheet, particularly the mechanical strength of the fiber reinforced sheet in the direction perpendicular to the longitudinal direction (winding and unwinding directions). Therefore, it is preferably composed of a material having an appropriate strength, and from the viewpoint of moldability and processability, polyolefin resin, polyester resin, polyamide resin, and the like can be mentioned. As the thermosetting resin, epoxy resin, unsaturated polyester resin, phenol resin, melamine resin, and polyurethane resin can be used. From the viewpoint of mechanical strength, polyolefin resin is preferable, and polypropylene resin is more preferable.

The method for producing the core portion 13 having an expansion ratio of the present invention is not particularly limited as long as it is a known foam molding method, and examples thereof include gas foaming and a method of adding a foaming agent and then heating. From the viewpoint of controllability, a method of heating a thermoplastic resin composition containing a foaming agent to form a foamed thermoplastic resin is preferred.

Examples of the foaming agent include thermally decomposable foaming agents that are gasified by thermal decomposition, and thermally expandable hollow particles obtained by introducing a low boiling point compound into a thermoplastic balloon material. Hollow particles are preferably used.

The content of the foaming agent in the thermoplastic resin composition containing the foaming agent is usually 0.1 parts by mass or more, preferably 0.3 parts by mass or more, more preferably 0.1 part by mass or more, based on 100 parts by weight of the thermoplastic resin. It is 5 parts by mass or more, while the upper limit is usually 4 parts by mass or less, preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and still more preferably 1.5 parts by mass or less. By setting the content of the foaming agent within the above range, it becomes easier to control the foaming ratio of the obtained foamable resin group within the range specified in the present application.

<6. Method for producing a fiber-reinforced sheet>
As a method for molding the fiber-reinforced sheet, when using a thermoplastic resin, there is a method of performing roll forming molding in a state where the resin is softened by heating, a method of performing extrusion molding, and a method of performing bending after shaping. etc. The extrusion molding method is preferably used because it enables the production of long products.

As an example of the extrusion molding method, after the skin portion 13 is formed into a rib shape in a mold, the skin portion is filled with a resin that will form the core portion. The core resin can be continuously injected using an extrusion kneader. Then, after the skin portion 13 and the core portion 11 are heated in an extrusion molding die and integrated, the substrate portion and the rib portion are brought into contact with each other to be fused.

A long molded product can be obtained by collecting the extrudate while cooling the fiber-reinforced sheet discharged from these molds.

When using the method of integrating the core part and the skin part in the extrusion molding die, the mold temperature is usually 200°C or higher, preferably 205°C or higher, while the upper limit is usually 240°C or lower, preferably 230°C. Below, more preferably 220 degrees or less.

When the mold temperature is within the above range, the bonding strength between the skin portion and the rib portion is improved, and shrinkage of the resin is reduced, which tends to reduce warpage of the fiber-reinforced sheet obtained as a result.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<raw materials>
(Skin part)
[Carbon fiber]
CF: Trade name “TC-35 12K” manufactured by Taiwan Plastics Co., Ltd. (PAN-based carbon fiber bundle, number of filaments: 24000, UD fiber)
[Fiber-reinforced thermoplastic resin composite]
CF prepreg: UD prepreg in which polypropylene resin is impregnated in CF

(core part)
[Thermoplastic resin]
PP: Prime Polymer E111G (homopolypropylene resin)
[Expanded particles]
AD: Advancel EM P501E1 manufactured by Sekisui Chemical Co., Ltd. (shell part: acrylonitrile, core part: low boiling point hydrocarbon)

(Base material)
GF base material: RC800 (glass roving cloth) manufactured by Hokuriku Fiber Glass Co., Ltd.

<Evaluation method>
(Expansion ratio)
Only the foamed resin was sampled, the bulk specific gravity was measured with a hydrometer, and the expansion ratio was calculated from the difference in specific gravity from the unfoamed resin.

(Amount of warpage)
A fiber reinforced sheet with a rib length of 3.1m is placed on a surface plate parallel to the ground so that the rib portion faces downward, and the space between the surface plate and the rib portion is maximized in the vertical direction. The distance between the points was measured with a Hyde gauge. This result was taken as the amount of warpage.

(bending stiffness)
A fiber reinforced sheet having a length of 480 mm and one rib was prepared, and a three-point bending test was performed with the top of the rib directed downward. The test conditions are as follows.
Distance between fulcrums: 400mm
Central indenter descent speed: 5.0 mm/min
Central indenter Radius: 75mmR

(rib weight)
A 1 m rib was cut out from the fiber reinforced sheet for each base material portion and measured with a weight scale.

[Example 1]
Three layers of CF prepreg to be the skin layer were laminated, and after molding into a shape in which the top of the rib was on the bottom surface using a mold, it was introduced into an extrusion molding die set at 225 degrees. Next, in the mold, a resin composition containing 100 parts by weight of PP and 1 part by weight of AD was continuously injected from above at 200 degrees so as to fill the skin layer.
Then, before the rib member ejected from the extrusion mold was cooled, the rib portion and the GF substrate were fused by keeping the opposite surface of the rib member in contact with the GF substrate.
A long fiber-reinforced sheet could be produced by continuously performing the extrusion molding process.

The resulting fiber-reinforced sheet was evaluated for bending rigidity, rib weight, and amount of warpage as described above. Table 1 shows the results. In addition, the foamed resin at the time of injection was separately sampled, and the foaming ratio was evaluated.

[Example 2]
A fiber-reinforced sheet was produced in the same manner as in Example 1, except that the temperature of the extrusion mold was changed to 210°C. The amount of warpage of the obtained fiber reinforced sheet was evaluated and shown in Table 1. In addition, the foamed resin at the time of injection was separately sampled, and the foaming ratio was evaluated.

[Comparative Example 1]
A fiber-reinforced sheet was produced in the same manner as in Example 1, except that AD was not added to the resin composition corresponding to the core portion.

[Comparative Example 2]
A fiber-reinforced sheet was produced in the same manner as in Example 1, except that the AD addition amount of the resin composition corresponding to the core portion was changed to 5 parts. The resulting fiber-reinforced sheet was evaluated for bending rigidity, rib weight, and amount of warpage as described above. Table 1 shows the results. In addition, the foamed resin at the time of injection was separately sampled, and the foaming ratio was evaluated.

From the comparison between Comparative Examples 1 and 2, it was found that if the core portion was foamed to such an extent that the effect of reducing the rib weight could be expected, the flexural rigidity would be greatly reduced. Further, from the comparison with Comparative Example 1 and Example 1, it was found that the fiber reinforced sheet using the microfoamed resin in the core portion can significantly reduce the amount of warpage while sufficiently maintaining bending rigidity.
It was also found that even with a fiber-reinforced sheet using the same microfoamed resin in the core portion, a further effect of reducing the amount of warpage can be obtained by controlling the mold temperature.

From the above results, it is thought that by using the microfoamed resin in the core portion, the foamed portion could absorb the shrinkage of the resin after molding, and the warpage of the fiber reinforced sheet could be reduced.

REFERENCE SIGNS LIST 1 fiber reinforced sheet 11 rib portion 12 skin portion 13 core portion

Claims (8)

At least one rib portion containing carbon fiber and thermoplastic resin is provided for the base portion,
a skin portion in which the rib portion is made of a carbon fiber reinforced thermoplastic resin composite;
A fiber-reinforced sheet comprising a core portion made of a thermoplastic resin,
A fiber-reinforced sheet, wherein the resin foaming ratio of the core portion is 1.05 to 2.0 times. 2. The fiber-reinforced sheet according to claim 1, wherein the base material portion includes a resin-unimpregnated fiber bundle portion or a resin partially-impregnated portion having a surface not impregnated with resin. The fiber-reinforced sheet according to claim 1 or 2, wherein the base material portion includes either a glass mat layer or a glass roving layer. The fiber-reinforced sheet according to any one of claims 1 to 3, wherein the base material is partially impregnated with an unsaturated polyester resin. The fiber-reinforced sheet according to any one of claims 1 to 4, wherein the thermoplastic resin of the core portion contains hollow acrylic particles. The fiber-reinforced sheet according to any one of claims 1 to 5, wherein the carbon fiber-reinforced thermoplastic resin composite of the skin portion is a prepreg sheet containing unidirectional continuous fibers. The fiber-reinforced sheet according to any one of claims 1 to 6, wherein the rib portion has a width of 0.3 to 2 cm, a height of 0.3 to 7 cm, and a length of 10 cm or more. The fiber-reinforced sheet according to any one of claims 1 to 7, wherein the vertexes of the rib portions are curved in the longitudinal vertical cross-sectional shape of the rib portions.

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