JP7082953B2 - Resin complex - Google Patents

Description

The present invention relates to a resin complex, and more particularly to a resin complex including a core material and a fiber reinforced resin layer covering the core material.

Conventionally, a resin composite having a core material made of a resin foam and a fiber-reinforced resin layer containing a resin and a fiber and the core material being covered with the fiber-reinforced resin layer has been used for various purposes. ing.
This type of resin complex has excellent strength while being lightweight, and for example, Patent Document 1 below describes that it is used as a part of a vehicle, a wind turbine, or the like.

Japanese Unexamined Patent Publication No. 2017-177704

The resin complex is used from a plate-like one having a relatively simple shape to a one having a complicated shape such as the above-mentioned vehicle parts.
When the shape of the resin complex becomes complicated, it is necessary to manufacture a core material having a complicated shape, and it becomes difficult to form the core material with only one resin foam.
In such a case, it is conceivable to use a plurality of resin foams to form one core material.
However, in such a case, the resin foams are bonded to each other to form one core material, and when stress is applied to the resin composite, stress concentration is likely to occur in the vicinity of the bonded surface. Have a problem.

The above-mentioned problems may occur not only when the resin composite has a complicated shape but also when the core material is composed of a plurality of resin foams.
However, no attention has been paid to such a problem so far, and no means for solving such a problem has been established.
The present invention has been made to solve such a problem, and an object of the present invention is to provide a resin composite having excellent strength.

As a result of diligent studies by the present inventor in order to solve the above problems, the resin foam is used as a bead foamed molded product, and the resin foam particles on the surface layer portion are formed as an adhesive surface when the bead foamed molded products are bonded to each other. The present invention has been completed by finding that the strength of the bead foamed molded product in the vicinity of the adhesive surface is enhanced by flattening the bubbles inside the bead.

In order to solve the above problems, the present invention
A resin complex comprising a core material and a fiber-reinforced resin layer covering the core material.
The core material is composed of a plurality of resin foams including a first resin foam and a second resin foam, and an adhesive surface to which the first resin foam and the second resin foam are adhered. Have and
The first resin foam and the second resin foam are each a bead foamed molded product composed of a plurality of resin foam particles, and the adhesion is made as compared with the bubbles inside the resin foam particles located at the center. Provided is a resin composite in which the bubbles inside the resin foamed particles constituting the surface have a flatter shape.

According to the present invention, a resin complex having excellent strength can be produced.

The schematic perspective view which showed the resin complex which concerns on one Embodiment. FIG. 1 is a cross-sectional view taken along the line II-II. A schematic cross-sectional view showing an enlarged portion of the broken line B in FIG. 2, and a partially enlarged view showing a part thereof. FIG. 2 is a schematic cross-sectional view showing an enlarged portion of the broken line C in FIG. Schematic cross-sectional view which showed the resin complex which concerns on other embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the resin complex of the present embodiment, and as shown in the figure, the resin complex 1 of the present embodiment has a rounded long plate shape.
That is, the resin complex 1 of the present embodiment has a smaller dimension in the width direction Y than a dimension in the length direction X, and further smaller in the thickness direction Z.

As shown in FIGS. 2 and 3, the resin composite 1 of the present embodiment includes a core material 2 as a core and a fiber reinforced resin layer 3 as an outer shell covering the core material 2.
In the resin composite 1 in the present embodiment, the core material 2 is composed of a plurality of resin foams.
In the present embodiment, the first resin foam 21 and the second resin foam 22 are provided as the plurality of resin foams constituting the core material 2.
That is, the core material 2 in the present embodiment is composed of a plurality of resin foams including the first resin foam 21 and the second resin foam 22.

In the core material 2 of the present embodiment, the first resin foam 21 and the second resin foam 22 are laminated in the thickness direction Z of the resin complex 1.
The resin composite 1 in the present embodiment has the first surface 1f on which the first resin foam 21 is arranged on the inside and the surface opposite to the first surface 1f, and the second resin foam on the inside. It has a second surface 1h on which the body 22 is arranged.

The core material 2 of the present embodiment has an adhesive surface 2a between the first resin foam 21 and the second resin foam 22 at a central portion in the thickness direction Z.
More specifically, the first resin foam 21 in the present embodiment has an adhesive surface 21a adhered to the second resin foam 22, and the second resin foam 22 is the first resin foam. It has an adhesive surface 22a adhered to 21, and the first resin foam 21 and the second resin foam 22 form the core material 2 by matching the adhesive surfaces.

In the present embodiment, an adhesive is used for adhering the first resin foam 21 and the second resin foam 22, and strictly speaking, the core material 2 is the first resin foam. It is composed of 21, the second resin foam 22, and an adhesive layer 23 provided between them.
The first resin foam 21 and the second resin foam 22 are sufficiently adhered to the outer peripheral edge portion, and the outer peripheral edges of the adhesive surfaces 21a and 22a (the outer peripheral edge of the adhesive layer 23) are these. The resin foams of the above form an adjacent boundary line 2x.

In the present embodiment, the first resin foam 21 and the second resin foam 22 constituting the core material 2 are bead foam molded bodies in which a plurality of resin foam particles 20a are integrated by heat fusion. be.

The first resin foam 21 has a central portion of the resin foam particles 20a on the surface layer such as the resin foam particles 20a1 constituting the adhesive surface 21a and the resin foam particles 20a2 in contact with the resin foam particles 20a1 from the inside. There is no big difference in the degree of flatness even when compared with the resin foamed particles 20a located in.
On the other hand, the bubbles inside the resin foamed particles 20a1 and 20a2 on the surface layer portion are flatter than the bubbles inside the resin foamed particles 20a located at the center.
That is, the first resin foam 21 is compared with the first layer of the resin foam particles 20a1 constituting the adhesive surface 21a and the next second layer of the resin foam particles 20a2. The resin foam particles 20a in the central portion of the resin foam 21 in the thickness direction Z have bubbles having a shape closer to a sphere inside.
It should be noted that the dimensions of the resin foamed particles 20a1 in the first layer and the resin foamed particles 20a2 in the second layer in the direction along the adhesive surface 21a are larger than the dimensions in the direction orthogonal to the adhesive surface 21a. Slightly long.

The second resin foam 22 is also configured in the same manner as the first resin foam 21.
That is, the second resin foam 22 is the resin in which the resin foam particles 20a1 constituting the adhesive surface 22a and the resin foam particles 20a2 in contact with the resin foam particles 20a1 from the inside are located at the center thereof. It has flat air bubbles inside as compared with the foamed particles 20a.
The second resin foam 22 is compared with the first layer of the resin foam particles 20a1 constituting the adhesive surface 22a and the next second layer of the resin foam particles 20a2. The resin foam particles 20a in the central portion of the resin foam 22 in the thickness direction Z have bubbles having a shape closer to a sphere inside.
Further, in the second resin foam 22, the dimensions of the first layer of the resin foam particles 20a1 and the second layer of the resin foam particles 20a2 in the direction along the respective adhesive surfaces 22a are the adhesive surfaces. It is slightly longer than the dimension in the direction orthogonal to 22a.

The shape of the bubbles inside the resin foamed particles 20a can be observed by photographing a cross section with a scanning electron microscope or the like.
The flat shape of the bubbles inside means that the resin foamed particles 20a are unlikely to be distorted by an external force.
That is, it is considered that the resin foam particles having flat bubbles inside are difficult to absorb stress and act effectively to propagate the force.

When an external force is applied to the resin composite 1 of the present embodiment or the core material 2 before forming the resin composite 1, the adhesive surface between the first resin foam 21 and the second resin foam 22 A force is likely to act on 2a, and stress concentration is likely to occur at the interface between the first resin foam 21 and the second resin foam 22.
The core material 2 of the present embodiment is composed of resin foamed particles having excellent force propagation at the portion where stress concentration is likely to occur.
That is, when the bubbles are flat inside the resin foamed particles 20a1 of the first layer constituting the adhesive surface and the resin foamed particles 20a2 of the next layer, the stress applied to the adhesive surface is applied to these resins. The foamed particles 20a1 and 20a2 are easily diffused into the core material 2, and stress concentration is suppressed.

The size of the flat bubbles inside the resin foamed particles 20a1 is preferably 50 μm or more in the longitudinal direction (FL _L ), and more preferably 100 μm or more.
The dimension in the longitudinal direction is preferably 300 μm or less, more preferably 250 μm or less.
The ratio (FL _L / FL _S , hereinafter also referred to as “bubble aspect ratio”) of the dimension (FL _L ) in the longitudinal direction to the dimension (FL _S ) in the lateral direction of the bubble may be 2.0 or more. It is preferably 2.5 or more, more preferably 3.0 or more, and particularly preferably 3.0 or more.

The resin foamed particles 20a1 in the first layer and the resin foamed particles 20a2 in the second layer containing such bubbles are preferably closer to a spherical shape than flat, and are in a direction orthogonal to the longitudinal direction (short). It is preferable that the ratio (BL _L / BL _S , hereinafter also referred to as “bead aspect ratio”) of the dimension (BL _L ) in the longitudinal direction to the dimension (BL _S ) of the bubble in the manual direction is 2 or less. It is more preferably 5 or less.

The shape of the bubbles of the resin foam particles 20a and the shape of the resin foam particles themselves are the cross sections when the first resin foam 21 and the second resin foam 22 are cut on a plane orthogonal to the adhesive surfaces 21a and 22a. The shape of the particles can be confirmed by observing them with a scanning electron microscope (SEM) or the like.

As the dimension in the longitudinal direction (FL _L ) of the bubble, as shown in FIG. 3, a point where the length of the line segment connecting two points having different contour lines ABx of the bubble AB is the longest is obtained, and this line segment is obtained. The length means the dimension in the longitudinal direction (FL _L ), and the dimension in the lateral direction (FL _S ) means the vertical bisector that passes through the midpoint of the line segment and is orthogonal to the line segment. It means the distance between two points that intersect the contour line ABx.

The degree of flatness of the resin foam particles 20a1 in the first layer and the resin foam particles 20a2 in the second layer (bead aspect ratio) is such that the length of the line segment connecting two different points on the contour line is the longest. The line segment obtained is defined as the major axis 20L (BL _L ) of the resin foamed particles 20a, and the line segment orthogonal to the major axis 20L through the intermediate point in the length direction of the major axis 20L is the contour line of the resin foamed particles 20a. The minor axis 20S (BL _S ) is defined between the two points intersecting with the minor axis, and can be confirmed by the ratio of the major axis 20L to the minor axis 20S (length of the major axis 20L / length of the minor axis 20S).

The degree of flatness of the resin foamed particles 20a1 in the first layer of the first resin foam 21 and the second resin foam 22 (bead aspect ratio) and the degree of flatness of the resin foamed particles 20a2 in the second layer (beads). The comparison with the aspect ratio) can be obtained by comparing the average values of the measurement results of a plurality of (for example, 10) resin foamed particles 20a randomly selected in the cross section of the core material 2, respectively.
The same applies to the degree of flatness (bubble aspect ratio) of the bubbles AB inside these.
Further, a comparison between the bead aspect ratio of the resin foamed particles in the central portion of the first resin foam and the central portion of the second resin foam 22 in the thickness direction Z and the bead aspect ratio of the resin foamed particles 20a1 in the first layer can be obtained. The comparison of these bubble aspect ratios can also be compared with the average value.
The above-mentioned preferable values regarding the size of the bubble AB, the bubble aspect ratio, and the bead aspect ratio are preferably such values even in such an average value.

In order to prepare the first resin foam 21 and the second resin foam 22 so that the shape of the resin foam particles in the vicinity of the adhesive surface is as described above, the bead foamed molded product once produced is described. A method of applying pressure to the surface to be the adhesive surface to compress the surface layer portion can be adopted.
Specifically, in order to prepare the first resin foam 21 and the second resin foam 22, pressure may be applied to the bead foam molded body using a hot press machine or the like.
Before or during pressurization, the surface to be pressurized may be heated as needed.
Specifically, if the surface to be the adhesive surface of the bead foamed molded product is radiantly heated to selectively heat only the portion where the resin foam particles are desired to be flattened, then pressurization is performed. good.

After that, if the flattened resin foam particles on the surface layer are expanded by the foaming force of the foaming agent to give the original roundness, the shape of the resin foam particles themselves is rounded but inside. Bubbles can be flattened.

As described above, in the resin composite 1 of the present embodiment, the core material 2 is composed of a plurality of resin foams including the first resin foam 21 and the second resin foam 22, and the first resin foam is formed. The body 21 has an adhesive surface 2a to which the second resin foam 22 is adhered, and the first resin foam 21 and the second resin foam 22 each have a plurality of resin foam particles 20a. In the bead foam molded body composed of, the bubbles inside the resin foam particles constituting the adhesive surface have a flatter shape than the bubbles inside the resin foam particles located at the center. It is a resin composite.

The first resin foam 21 and the second resin foam 22 are, for example, polyolefin resin foams such as polyethylene resin foams and polypropylene resin foams; general-purpose polystyrene resin (GPPS) foams and high-impact polystyrene resins (HIPS). ) Polystyrene resin foams such as foams; polyamide resin foams such as polyamide 12 foams, polyamide 6 foams, polyamide 66 foams; polylactic acid resin foams, polybutylene succinate resin foams, polyethylene terephthalate resin foams , Polybutylene terephthalate resin foam and the like polyester resin foam; polycarbonate resin foam; acrylic resin foam and the like.

The first resin foam 21 and the second resin foam 22 are preferably any one of a polyethylene terephthalate resin foam, a polycarbonate resin foam, and an acrylic resin foam in order to exhibit high strength. ..
The first resin foam 21 and the second resin foam 22 may be polyethylene terephthalate resin foams in that it is advantageous to keep the internal bubbles in a round state while flattening the resin foam particles. Especially preferable.

The first resin foam 21 and the second resin foam 22 can be, for example, resin foams having an apparent density of 50 kg / m ³ or more and 700 kg / m ³ or less.
The first resin foam 21 and the second resin foam 22 may have the same or different apparent densities.

The apparent densities of the first resin foam 21 and the second resin foam 22 can be measured by the method described in JIS K7222: 2005 "Foam Plastics and Rubber-How to Obtain the Apparent Density".
That is, the apparent density can be obtained in principle as follows.

(Apparent density measurement method)
A test piece of 100 cm ³ or more can be cut so as not to change the original cell structure of the material as much as possible, its mass is measured, and it can be calculated by the following formula.

Apparent density (kg / m ³ ) = test piece mass (kg) / test piece volume (m ³ )

In principle, the test piece for measurement shall be cut from a sample that has passed 72 hours or more after being molded, and left in an atmospheric condition with a temperature of 23 ± 2 ° C. and a humidity of 50 ± 5% for 16 hours or more. ..

Adhesion between the first resin foam 21 and the second resin foam 22 is preferably performed by a reaction-curable adhesive rather than a mere pressure-sensitive adhesive.
The reaction-curing adhesive may be a thermosetting type or a room temperature curing type.
However, since it is difficult to efficiently apply heat to the central portion of the core material 2 from the outside, the first resin foam 21 and the second resin foam 22 are bonded with a room temperature curable adhesive. It is preferable to do so.
Examples of the room temperature curable adhesive include a silicon-based adhesive, an acrylic-based adhesive, and an epoxy-based adhesive.
As the room temperature curable adhesive, an epoxy adhesive is suitable.
The epoxy adhesive is preferably a two-component mixed type in which the main agent and the curing agent are mixed immediately before use.

In the present embodiment, the fiber-reinforced resin layer 3 that covers the surface of the core material 2 is formed of two sheet-shaped fiber-reinforced resin materials.
One of the fiber-reinforced resin materials is laminated on the first resin foam 21, and the other is laminated on the second resin foam 22.
That is, the fiber-reinforced resin layer 3 of the present embodiment is also referred to as a first portion (hereinafter, "first fiber-reinforced resin layer 31") made of the fiber-reinforced resin material laminated on the first resin foam 21. It is provided with a second portion (hereinafter, also referred to as “second fiber reinforced resin layer 32”) made of the fiber reinforced resin material laminated on the second resin foam 22.

As shown in FIG. 4, the first fiber reinforced resin layer 31 is composed of a sheet-shaped fiber base material 31a and a resin 31b impregnated in the fiber base material 31a and supported on the fiber base material 31a. There is.
The second fiber reinforced resin layer 32 is also composed of a fiber base material 32a made of a fiber material and a resin 31b impregnated with the fiber base material 32a and supported on the fiber base material 32a.
That is, the fiber-reinforced resin layer 3 in the present embodiment has the first fiber base material 31a (hereinafter, also referred to as "first fiber base material 31a") laminated on the first resin foam 21 and the second resin foam. A plurality of fiber base materials including the second fiber base material 32a laminated on the body 22 (hereinafter, also referred to as “second fiber base material 32a”) are used for forming the fiber reinforced resin layer 3.

As described above, the fiber reinforced resin layer 3 of the present embodiment is the first fiber base material 31a used for forming one region and the second fiber group used for forming another region different from the one region. It has a plurality of fiber base materials including the material 32a.

In the present embodiment, the first fiber base material 31a and the second fiber base material 32a overlap and cover the boundary line 2x of the core material 2.
That is, in the present embodiment, the fiber-reinforced resin layer 3 contains sheet-shaped fiber base materials 31a, 32a and resins 31b, 32b impregnated in the fiber base materials 31a, 32a, and the surface of the core material 2. Then, the first fiber base material 31a covering the first resin foam 21 extends beyond the boundary line 2x to the second resin foam 22 and covers the second resin foam 22. The second fiber base material 32a extends beyond the boundary line 2x to the first resin foam 21, and at the boundary line 2x, the first fiber base material 31a covers the first resin foam 21. And the second fiber base material 32a covering the second resin foam 22 overlap each other to cover the core material 2.

The width WD (width measured along the surface of the outer fiber base material) of the portion where the first fiber base material 31a and the second fiber base material 32a overlap each other is the entire area where the overlap is formed. It is preferable that the average value (hereinafter, also referred to as “average lap width”) is 1 mm or more.
The average lap width is more preferably 2 mm or more, and particularly preferably 3 mm or more.
The width WD is usually 25 mm or less at the maximum, and the average lap width is also usually 25 mm or less.

In the present embodiment, the overlapping of the fiber base materials extends in a band shape along the outer peripheral edge of the adhesive layer 23.
Therefore, in the present embodiment, the reinforcing structure formed by the adhesive layer 23 and the overlapping of the fiber base materials is in a state like H steel, and has a high reinforcing effect on the resin composite 1. Demonstrate.

As shown in FIG. 5, the above-mentioned effect can be exhibited if at least one of the first fiber base material 31a and the second fiber base material 32a crosses the boundary line 2x and covers the core material 2.
That is, at least one of the first fiber base material 31a covering the first resin foam 21 and the second fiber base material 32a covering the second resin foam 22 crosses the boundary line 2x. When the core material 2 is covered with the other fiber base material and the region adjacent to the boundary line 2x of the core material 2 is covered with the overlapping fiber base material (31a, 32a). Since the reinforcing structure formed by the adhesive layer 23 is formed in a state like an L-shaped angle, the same effect as that shown in FIG. 4 can be exhibited.
The overlap width WD'formed in this case and its average value (average lap width) can be the same as those shown in FIG.

When producing the resin composite 1 of the present embodiment, a pressing method is adopted in which the pressurizing direction is the thickness direction of the resin composite 1, but the first fiber group is used. Since the material 31a and the second fiber base material 32a are misaligned in this pressing direction, the direction in which the first fiber base material 31a and the second fiber base material 32a increase the average lap width during pressing. It can be slid appropriately, and it shows good followability to the surface shape of the core material 2 and is less likely to cause wrinkles.
That is, the resin composite 1 of the present embodiment not only exerts a high reinforcing effect but also has a beautiful appearance because the fiber base materials overlap each other at the end portion in the width direction Y.

The fiber base material (31a, 32a) used for forming the fiber-reinforced resin layer 3 may be a woven fabric such as a plain woven fabric, a twill woven fabric, or a satin woven fabric, or a non-woven fabric.
The fiber base material (31a, 32a) may be a knitted fabric.

The fibers constituting the fiber base material (31a, 32a) are not particularly limited, and are, for example, aramid fiber, polyvinyl alcohol fiber, vinyl chloride fiber, acrylic fiber, polyester fiber, polyurethane fiber, polyethylene fiber, polypropylene fiber, and polystyrene fiber. , Organic fibers such as acetate fibers and inorganic fibers such as carbon fibers, glass fibers and metal fibers.

The resin (31b, 32b) impregnated in the fiber base material (31a, 32a) may be either a thermoplastic resin or a thermosetting resin.
Examples of the thermoplastic resin include thermoplastic resins such as polyethylene resin, polypropylene resin, polystyrene resin, polybutadiene resin, styrene butadiene resin, polyacetal resin, polyamide resin, and polycarbonate resin.
Examples of the thermosetting resin include unsaturated polyester resin, acrylic resin, vinyl ester resin, epoxy resin, urethane resin, phenol resin, and silicon resin.

The fiber-reinforced resin layer 3 may not contain fibers in a sheet-like state, or may be in a state in which short fibers are dispersed in a matrix resin.

The fiber-reinforced resin layer 3 can usually be formed so that the average thickness of the fiber-reinforced resin layer 3 is 0.05 mm or more and 20 mm or less except for the portion where the fiber base materials overlap, and the average thickness is 0.1 mm or more and 10 mm or less. It is preferably formed to have a thickness.
The average thickness can be obtained by calculating an arithmetic mean value measured at a plurality of randomly selected locations (for example, 10 locations) in the resin complex 1.

The fiber base material (31a, 32a) does not have to have the same thickness and material as the first fiber base material 31a and the second fiber base material 32a, and these may be different.
Further, the resin 31b supported on the first fiber base material 31a and used as a material for forming the first fiber reinforced resin layer 31 and the second fiber reinforced resin supported on the second fiber base material 32a. The material and the like do not have to be the same as those of the resin 32b, which is the material for forming the layer 32, and may be different.
Therefore, the average thickness of the first fiber reinforced resin layer 31 and the second fiber reinforced resin layer 32 may be different.

The first fiber reinforced resin layer 31 and the second fiber reinforced resin layer 32 do not need to have one fiber base material (31a, 32a), respectively, and a plurality of fiber base materials may be used on either one or both of them. May be provided in a state of being laminated in the thickness direction.
In that case, the fiber base material 31a provided in the first fiber reinforced resin layer 31 and the fiber base material 32a provided in the second fiber reinforced resin layer 32 are alternately laminated at the formation point of the boundary line 2x. It is preferable to cover the core material 2.
Further, when a plurality of fiber base materials are provided in the first fiber reinforced resin layer 31 and the second fiber reinforced resin layer 32, all the fiber base materials do not overlap at the formation point of the boundary line 2x. May be good.
Further, in the present embodiment, the fiber base materials are overlapped with each other in order to exert an excellent reinforcing effect, but if necessary, the fiber base materials may not be overlapped with each other.

In the present embodiment, the fiber base material is laminated on the first resin foam 21 and the second resin foam 22, respectively, but if necessary, the entire core material is covered with one fiber base material. You may do so.
Further, one or both of the first resin foam 21 and the second resin foam 22 may be divided into a plurality of regions, and the fiber base material covering one region may be separated from the fiber base material covering the other region. good.

The method for producing the resin complex of the present embodiment is not particularly limited, but the method thereof is not particularly limited.
A plurality of resin foams including a first resin foam and a second resin foam, and a sheet-shaped fiber-reinforced resin material containing a thermosetting resin and fibers before curing are prepared.
An adhesive step of adhering the first resin foam and the second resin foam with an adhesive to form a core material,
A press that heats the fiber-reinforced resin material laminated on the core material while pressing it toward the core material to cure the thermosetting resin and form the fiber-reinforced resin layer with the fiber-reinforced resin material. Carry out the process and
It is preferable that the reaction-curing type adhesive is used in the bonding step, and the curing reaction of the adhesive is completed after the curing of the thermosetting resin.

The resin composite of the present embodiment has various shapes in various applications such as automobile door panels and bumpers, automobile and motorcycle aero parts, aircraft and ship body parts, robot parts, windmill blades, and sports helmets. Can be used in.
Although the embodiment in which the core material 2 is composed of two resin foams is exemplified in the present embodiment, three or more resin foams may be used for the composition of the core material 2.
The resin complex of the present embodiment does not have to be as illustrated above for other matters.
That is, the present invention is not limited to the above examples.

1: Resin composite, 2: Core material, 2a: Adhesive surface, 2x: Boundary line, 3: Fiber reinforced resin layer, 20a: Resin foam particles, 21: First resin foam, 22: Second resin foam, 31: 1st fiber reinforced resin layer, 31a: 1st fiber base material, 32: 2nd fiber reinforced resin layer, 32a: 2nd fiber base material

Claims (1)

A resin complex comprising a core material and a fiber-reinforced resin layer covering the core material.
The core material is composed of a plurality of resin foams including a first resin foam and a second resin foam, and an adhesive surface to which the first resin foam and the second resin foam are adhered. Have and
The first resin foam and the second resin foam are each a bead foamed molded product composed of a plurality of resin foam particles, and the adhesion is made as compared with the bubbles inside the resin foam particles located at the center. A resin composite in which the bubbles inside the resin foamed particles constituting the surface have a flatter shape.

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