Core material sheet, composite material, method for manufacturing core material sheet, and method for manufacturing composite material

Abstract

In order to provide a composite material having excellent moldability into a three-dimensional shape and excellent productivity, a core material sheet 10 used in the manufacturing of a composite material 30 comprises a core material layer sheet material 11 which is a sheet material used in a core material layer 33 of the composite material 30, the core material layer sheet material 11 having multiple divided parts 13 two-dimensionally arrayed in a plan view, the divided parts 13 being separated from each other on one surface side by incisions 16 resulting from half-cuts in a thickness direction thereof. The core material layer sheet material 11 has traces 13c where the half-cuts are formed by press cutting or laser cutting.

Description

Core sheet, composite material, method for manufacturing core sheet, and method for manufacturing composite material

[0001] The present invention relates to a core sheet or the like used in the production of a composite material.

[0002] A sandwich structure in which a core layer is sandwiched between skin layers is known as a composite material structure. Sandwich-structured composite materials are characterized by their light weight and high rigidity, and are expected to be used in a variety of applications. A low-density, relatively high-rigidity material (e.g., hard foam) is used for the core layer. However, when a sheet of such a material is used as is for the core layer, it is difficult to mold the sheet material to conform to a curved surface with a relatively large curvature, and it may be impossible to mold the composite into a desired three-dimensional shape.

[0003] Patent Document 1 describes a composite material having a core layer composed of many plate-like pieces, which is excellent in formability into a three-dimensional shape. Patent Document 1 also describes a method for producing the composite material by performing a step of transferring many plate-like pieces from a transfer sheet to which the many plate-like pieces are attached, onto a skin sheet (such as a prepreg).

[0004] Patent Document 2 describes a reinforcement structure made from a sheet-like base material. This reinforcement structure has material damping sections that divide the base material into multiple material islands. The material islands are separated by the material damping sections but are connected to each other by bridge sections. In the reinforcement structure described in Patent Document 2, the material damping sections are formed by performing a separation process that includes a cutting process and a sawing process that widens the cut portions of the cutting process. Furthermore, after the separation process, a bridge embossing machine is used to compression mold the bridge sections that connect the material islands.

[0005] Patent No. 7118481 U.S. Patent Application Publication No. 2019 / 0099964A1

[0006] However, in the above-described composite manufacturing method described in Patent Document 1, it may not be possible to smoothly transfer the numerous plate-like pieces on the transfer sheet to the skin sheet (such as prepreg) depending on the degree of curvature of the curved surface in the three-dimensional shape to be formed, the adhesive properties of the material used in the composite, etc. For example, when transferring to a skin sheet placed in a mold with a large curvature, if the transfer operation is not performed carefully, there is a risk that some of the plate-like pieces will remain on the transfer sheet, which makes the transfer operation more time-consuming and reduces productivity.

[0007] Furthermore, in the reinforcement structure described in Patent Document 2, at least three processes, namely, a cutting process, a sawing process, and an embossing process, are required to form the material damping portion and the bridge portion, so it is not easy to increase the productivity of the reinforcement structure.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a composite material that has good formability into three-dimensional shapes and good productivity.

[0009] To solve the above-mentioned problems, the present inventors came up with the idea of ​​applying half-cutting to the processing of sheet material used in the core layer of a composite material to obtain a sheet material that can be formed into a three-dimensional shape. Furthermore, while press-cutting or laser-cutting sheet material used in the core layer has not been conventionally performed, the inventors came up with press-cutting or laser-cutting as a half-cutting method to improve productivity. A first invention based on these ideas is a core sheet used in the manufacture of a composite material, which is a sheet material used in the core layer of a composite material, and which includes a sheet material for a core layer having a plurality of divided sections arranged two-dimensionally in a plan view, the divided sections being separated from one another by cuts made by half-cutting in the thickness direction of the sheet material, and the core layer sheet material has traces of the half-cutting made by press-cutting or laser-cutting.

[0010] A second aspect of the present invention is the device according to the first aspect of the present invention, further comprising a supporting sheet material attached to one surface or the other surface of the core layer sheet material so as to cover the surface.

[0011] The third invention is the first invention, in which adjacent divided portions of the core layer sheet material are connected to each other by a portion of the thickness range from the bottom of the notch to the other surface of the core layer sheet material.

[0012] The fourth invention is any one of the first to third inventions, wherein in the sheet material for the core layer, a portion of the dividing portion that divides the multiple dividing portions from each other is formed by a half-cut notch, and the remainder of the dividing portion is formed by a full-cut through portion.

[0013] In a fifth aspect of the present invention, in any one of the first to third aspects, the notch has a V-shaped valley shape in cross section.

[0014] A sixth aspect of the present invention is the sheet material according to any one of the first to third aspects, wherein the depth of the slit is 60% or more of the thickness of the sheet material for the core layer.

[0015] A seventh aspect of the present invention is a composite material comprising the core sheet of any one of the first to third aspects of the present invention and a skin material laminated on the core layer sheet material.

[0016] The eighth invention is the seventh invention, wherein the composite material has a curved portion in cross-sectional view, and in the curved portion, the opening side of the slit in the core layer sheet material faces the bulging side of the curved portion in cross-sectional view.

[0017] The ninth invention addresses the problem of providing a composite material that has good formability into three-dimensional shapes and good productivity by maintaining the connected state of the dividing portions 13 even if the connecting portion 14 described below in the core layer sheet material 11 is damaged, and includes a core layer sheet material used in the core layer of the composite material, in which a plurality of dividing portions are arranged two-dimensionally in a planar view, with one side of the sheet material being divided from each other by half-cuts in the thickness direction, and a retaining sheet material attached so as to cover one or the other side of the core layer sheet material.

[0018] The tenth invention is a method for manufacturing a core sheet comprising a core layer sheet material used in the core layer of a composite material, in which a cutting step is performed to form half-cut slits in the thickness direction in the sheet material, thereby producing a core layer sheet material in which multiple divided sections, each divided from one side of the sheet material, are arranged two-dimensionally in a planar view, and the half-cuts are made by press cutting or laser cutting.

[0019] An eleventh invention is a method for producing a composite material in which the core layer sheet material of the tenth invention is laminated on a skin material, and the method includes a lamination step of laminating a core layer sheet on a skin material sheet, which is the material for the skin material, and a curing step of curing the skin material sheet.

[0020] The twelfth invention addresses the problem of providing a composite material that has good formability into three-dimensional shapes and good productivity. The method for manufacturing a composite material includes a core layer sheet material used in the core layer of the composite material, the core layer sheet material having a plurality of divided sections that are arranged two-dimensionally in a plan view, the divided sections being separated from one another on one side of the sheet material by half-cuts in the thickness direction, and a retaining sheet material attached so as to cover one or the other side of the core layer sheet material. The core layer sheet is attached to a skin sheet that is a material for the skin material of the composite material, and after the attaching step, the retaining sheet material is peeled off from the core layer sheet material to transfer the core layer sheet material to the skin sheet.

[0021] In the present invention, a core layer sheet material used in a composite material for a core layer has a plurality of divided sections, each divided from the other on one side by half-cut slits (slits extending partway through the thickness direction), arranged two-dimensionally in a plan view. When the core layer sheet material is bent, the slits widen or narrow. Therefore, the core layer sheet material is easier to bend than an unprocessed sheet material (a core layer sheet material with flat surfaces on both sides) and can conform to a curved surface with a large curvature. Furthermore, because the divided sections formed by the half-cuts are connected to each other, some of the divided sections are less likely to separate when the core layer sheet material is attached to the skin sheet. Furthermore, because the half-cuts are performed by press cutting or laser cutting, productivity is good. According to the present invention, a composite material can be provided that is easily molded into three-dimensional shapes and has high productivity.

[0022] FIG. 1 is a cross-sectional view of a core sheet according to an embodiment. FIG. 2 is a surface view of the core sheet shown in FIG. 1. FIG. 3 is a cross-sectional view of a composite material produced using the core sheet shown in FIG. 1. FIG. 4 is a perspective view of the composite material shown in FIG. 3(a). FIG. 5 is a schematic diagram of a production line used in the production of the core sheet according to the embodiment. FIG. 6 is a cross-sectional view for explaining a method for producing the core sheet according to the embodiment. FIG. 7 is a cross-sectional view for explaining a method for producing the composite material shown in FIG. 3(a). FIG. 8(a) is a cross-sectional view of a composite material having a curved portion, FIG. 8(b) is a cross-sectional view after a lamination step in a method for producing a composite material on a mold having a concave surface, FIG. 8(c) is a cross-sectional view after a lamination step in a method for producing a composite material on a mold having a convex surface, and FIG. 8(d) is a cross-sectional view of an intermediate transfer sheet. FIG. 9 is a cross-sectional view for explaining a method for producing the composite material shown in FIG. 3(c). FIG. 10 is a view for explaining a method for producing a core sheet according to a first modified example of the embodiment. FIG. 11 is a diagram showing traces of half cuts on a core sheet according to a first modified example of the embodiment. FIG. 12 is a diagram for explaining a manufacturing method in which notches are formed by two laser cuts in the first modified example of the embodiment. FIG. 13 is a cross-sectional view of a core sheet according to a second modified example of the embodiment. FIG. 14 is a cross-sectional view for explaining a manufacturing method of a core sheet according to the second modified example of the embodiment. FIG. 15 is a cross-sectional view for explaining a manufacturing method of a composite material according to the second modified example of the embodiment. FIG. 16 is a cross-sectional view of another form of core sheet according to the second modified example of the embodiment. FIG. 17 is a surface view of the core sheet shown in FIG. 16. FIG. 18 is a cross-sectional view of a core sheet according to a third modified example of the embodiment. FIG. 19 is a surface view of a core sheet according to a fourth modified example of the embodiment. FIG. 20 is a cross-sectional view of a core sheet according to a fifth modified example of the embodiment.

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments are merely examples of the present invention and are not intended to limit the scope of the present invention, its applications, or its uses.

[0024] In this embodiment, a composite material 30 is manufactured using a core sheet 10 having the cross-sectional structure shown in Fig. 1. The core sheet 10 is an intermediate sheet manufactured in the manufacturing process of the composite material 30. Below, the core sheet 10 will be described first, followed by a description of the composite material 30.

[0025] [Configuration of Core Sheet] The core sheet 10 includes a core layer sheet material 11 used as the core layer 33 of the composite material 30, and a retaining sheet material 12 attached so as to cover the back surface 11b of the core layer sheet material 11. A release sheet (separate sheet) may be further provided on the back surface of the retaining sheet material 12.

[0026] The core layer sheet material 11 is a sheet material in which a plurality of divided sections 13 (numerous divided sections 13) separated from each other on the surface 11f side (one surface 11f side) by half-cut slits 16 are arranged two-dimensionally in a plan view, as shown in Figure 2. Adjacent divided sections 13 are separated by a common slit 16. The slits 16 are dividing points that divide adjacent divided sections 13, and are provided around the entire periphery of each divided section 13. In this specification, the term "numerous divided sections" means 10 or more. The number of divided sections 13 in the core layer sheet material 11 is, for example, 50 or more.

[0027] In the core layer sheet material 11, adjacent divided portions 13 are connected by connecting portions 14 that extend over the thickness range from the bottom of the slits 16 to the back surface 11b (the other surface 11b) of the core layer sheet material 11. No slits are formed on the back surface 11b of the core layer sheet material 11, and the multiple divided portions 13 are connected on the back surface 11b side. The core layer sheet material 11 consists of a sheet-like portion 11s that extends over the thickness range from the height position of the bottom of the slits 16 in the thickness direction (the position of the dashed line shown in Figure 1) to the back surface 11b of the core layer sheet material 11, and multiple divided portions 13 (plate-like portions 13) that are integrated with the sheet-like portion 11s.

[0028] In a cross-sectional view, the notches 16 have a V-shaped valley shape that widens from the valley bottom toward the surface 11f. The side surfaces of adjacent divisions 13 intersect at the valley bottom of the notches 16. Note that the cross-sectional shape of the notches 16 may be other than a V-shaped valley shape.

[0029] In the core layer sheet material 11, the planar shape (peripheral shape) of the dividing portions 13 is a regular polygon (a regular hexagon in this embodiment). When a large number of dividing portions 13 are uniformly arranged in the core layer sheet material 11, the planar shape of the dividing portions 13 can be selected to be a triangle, a rectangle, a hexagon, or an equilateral pentagon. When the planar shape of the dividing portions 13 is a polygon, chamfers may be provided at each corner of the dividing portions 13 in a planar view. Note that the dividing portions 13 may be any shape as long as the periphery is a shape consisting of straight lines, curves, or a combination of straight lines and curves, and the planar shape of the dividing portions 13 can also be selected to be a circle, an ellipse, or the like.

[0030] In the core layer sheet material 11, a large number of divisions 13 are arranged regularly and uniformly. In this embodiment, the divisions 13 are arranged in a staggered pattern, with the positions of the divisions 13 shifted by half a pitch between adjacent division rows 13L (see FIG. 2). In this embodiment, the planar shape of each division 13 is a regular hexagon, so the large number of divisions 13 have a honeycomb shape in plan view. The planar shape of the notches 16 also has a honeycomb shape.

[0031] Regarding the planar dimensions of the dividing portion 13, in this embodiment where the dividing portion 13 is a regular hexagon, the length of one side can be set to a value of 3 mm to 10 mm (for example, 5 mm). When the dividing portion 13 is a shape other than a regular hexagon, the planar dimensions can be set to a value of 3 mm to 10 mm, which is the average value of the distance from the center of gravity of the dividing portion 13 to the outer periphery (average value over 360 degrees; radius in the case of a circle). However, the dimensions of the dividing portion 13 may be set to a value outside the range described in this paragraph.

[0032] When viewed from above, adjacent dividing sections 13 face each other with one side thereof separated by a notch 16. The width of the notch 16 (the width at the surface 11f in the thickness direction) is constant across the core layer sheet material 11. This width can be adjusted depending on the width dimension of the blade 24 used for half-cutting, and is designed appropriately depending on the size of the dividing sections 13, etc.

[0033] The thickness D of the core layer sheet material 11 can be, for example, less than 4 mm (e.g., 3 mm or less or 2 mm or less). However, the thickness D of the core layer sheet material 11 may be 4 mm or more. The depth d of the slits 16 in the core layer sheet material 11 can be 60% or more (preferably 70% or more, more preferably 80% or more) of the thickness D of the core layer sheet material 11. If the depth d of the slits 16 is shallower than 60% of the thickness D of the core layer sheet material 11, it is difficult to obtain sufficient formability into a three-dimensional shape when a hard material is used for the core layer sheet material 11. In this embodiment, the depth d of the slits 16 is approximately constant throughout the core layer sheet material 11.

[0034] On the surface 11f of the core layer sheet material 11, a chamfered portion 13c is formed around the entire periphery of each dividing portion 13. The chamfered portion 13c is a trace (cut mark) indicating that the half cut was made by press cutting, and in cross section, it has an arc-shaped curved surface or a curved surface that bulges outward like an arc (see Figure 1). The cross-sectional shape of the chamfered portion 13c varies depending on the cross-sectional shape of the tip of the blade 24 used in the press cutting. The angle θ of the side of the dividing portion 13 (see Figure 1) also varies depending on the cross-sectional shape of the tip of the blade 24. When the core layer sheet material 11 is placed on a flat surface, the angle θ of the side of the dividing portion 13 can be 85° or less (e.g., 80° or less). By making the angle θ less than 90°, the volume of the notch 16 in the core layer 33 increases, thereby reducing the weight of the composite material 30.

[0035] The core layer sheet material 11 can be made of a material that is lower in density and harder than the skin materials 31 and 32 described below. Examples of such materials include resin (such as a hard resin foam), wood materials (such as balsa or plywood), and metal foams (such as aluminum alloys). In this embodiment, the core layer sheet material 11 is made of a hard resin foam or a wood material.

[0036] Examples of hard resin foams used for the core layer sheet material 11 include polystyrene foam, polyvinyl chloride foam, cellulose acetate foam, polyurethane foam, phenol foam, epoxy foam, acrylic foam, polymethacrylimide foam, polypropylene foam, polyethylene terephthalate foam, polycarbonate foam, polyamideimide foam, and polyphenylene sulfide foam.

[0037] The retaining sheet material 12 is provided so that all of the divided portions 13 remain connected even if the above-mentioned connecting portion 14 in the core layer sheet material 11 is damaged. A flexible sheet material can be used for the retaining sheet material 12. The retaining sheet material 12 is, for example, thinner than the core layer sheet material 11. The retaining sheet material 12 is adhered to the back surface 11b of the core layer sheet material 11 so as to cover the arrangement area of ​​the multiple divided portions 13 from the back surface 11b. An adhesive or pressure-sensitive adhesive can be used for this adhesion. A peel-off type pressure-sensitive adhesive can be used as this pressure-sensitive adhesive. This point is the same for all pressure-sensitive adhesives in this specification.

[0038] The holding sheet material 12 may be, for example, a resin sheet or film (such as a thermoplastic resin sheet). Resins that can be used for the holding sheet material 12 include polyethylene, polypropylene, urethane, polyester, polyethylene terephthalate (PET), and polycarbonate. The thickness of the holding sheet material 12 may be 0.01 mm or more and 0.5 mm or less. The holding sheet material 12 may also be a mesh sheet using an adhesive as a material, or a nonwoven fabric with adhesive fibers entangled. The holding sheet material 12 may also be a rubber or paper sheet (or film).

[0039] The core sheet 10 may be wound into a roll to be used as a product. In this case, a long core layer sheet material 11 is overlaid with a long supporting sheet material 12 of the same width.

[0040] [Configuration of Composite Material] Next, a sandwich-structured composite material 30 manufactured using the core sheet 10 will be described.

[0041] As shown in FIG. 3( a), one embodiment of the composite material 30 includes a core layer sheet material 11 of the core sheet 10, a first skin material 31 laminated on the core layer sheet material 11, and a second skin material 32 laminated on the side of the core layer sheet material 11 opposite the first skin material 31 and sandwiching the core layer sheet material 11 together with the first skin material 31. FIG. 4 is a perspective view of the composite material 30 shown in FIG. 3( a). The core layer sheet material 11 constitutes a core layer 33 of the composite material 30. The composite material 30 is obtained when the core sheet 10 is used as a transfer sheet. In this case, the core layer sheet material 11 of the core sheet 10 is releasably attached to the holding sheet material 12 using an adhesive.

[0042] In the composite material 30 shown in Figure 3(a), the matrix melted from the skin sheet 31A of the skin material 31 has solidified in the slit 16 of the core layer sheet material 11. Note that, as shown in Figure 3(b), a through hole 16P may be provided from the bottom of the slit 16 to the back surface 11b of the core layer sheet material 11 so that the matrix melted from the skin sheet 32A of the skin material 32 can easily flow into the slit 16. The through hole 16P can also be used in the composite material 30 shown in Figures 3(c) and 3(d) and in each of the modified examples described below.

[0043] 3(c), another embodiment of the composite material 30 includes a core sheet 10, a first skin material 31 laminated on the supporting sheet material 12 side of the core sheet 10, and a second skin material 32 laminated on the core layer sheet material 11 side of the core sheet 10 to sandwich the core sheet 10 together with the first skin material 31. The core layer sheet material 11 forms a core layer 33. The composite material 30 is obtained when the entire core sheet 10 is used as the material for the composite material 30. In the slits 16 of the core layer sheet material 11 in the composite material 30, the matrix that has melted from the skin sheet 32A of the material for the skin material 32 has solidified.

[0044] While the composite material 30 shown in Figure 3(c) uses a retaining sheet material 12 that does not melt when heated during the manufacturing process of the composite material 30, the composite material 30 may also be manufactured using a retaining sheet material 12 that melts when heated during the manufacturing process of the composite material 30. In this case, as shown in Figure 3(d), an adhesive layer 34 remains between the core layer sheet material 11 and the second skin material 32, where the retaining sheet material 12 has melted and solidified. In Figures 3(c) and 3(d), the increase in thickness due to the retaining sheet material 12 can be suppressed by using a mesh sheet using an adhesive as a material or a nonwoven fabric with adhesive fibers entangled as the retaining sheet material 12.

[0045] The skin materials 31, 32 used in the composite material 30 are skin materials or panel materials made of a different material from the core layer sheet material 11. The material of each of the skin materials 31, 32 may be metal-based, plastic-based, or inorganic. In this embodiment, fiber-reinforced plastic is used as the material of each of the skin materials 31, 32. As the fiber-reinforced plastic, a prepreg in which fibers are impregnated with a resin (matrix) can be used.

[0046] The fibers of the fiber-reinforced plastic may be any of inorganic fibers, organic fibers, metal fibers, and natural fibers, such as glass fibers, carbon fibers, aramid fibers, polyethylene fibers, polyester fibers, tungsten fibers, steel fibers, boron fibers, and flax fibers. The matrix of the fiber-reinforced plastic may be any of thermosetting resins and thermoplastic resins, such as polyester resin, epoxy resin, phenolic resin, vinyl ester resin, polyimide resin, polypropylene resin, nylon resin, polyether ether ketone resin, polybutylene terephthalate resin, and bismaleimide resin. The matrix of the fiber-reinforced plastic may be a biodegradable resin.

[0047] The composite material 30 can be used, for example, as a panel material where lightweight and rigidity are more important than strength. Specifically, the composite material 30 can be used as a structural material for mobile objects such as aircraft, automobiles, and bicycles (such as sports bicycles), electrical equipment, electronic devices, office equipment, home appliances, medical equipment, or building panel materials. In the case of mobile objects, the composite material 30 can be used as an aerodynamic component that constitutes the exterior.

[0048] [Method for manufacturing core sheet] A description will be given of a method for manufacturing the core sheet 10. The method for manufacturing the core sheet 10 includes, in this order, a bonding step of bonding the retaining sheet material 12 to a material sheet 111 that will be the material for the core layer sheet material 11, and a cutting step of cutting the material sheet 111 by half-cutting.

[0049] In the bonding step, a laminated sheet 19 (see FIG. 6( a)) is produced by bonding the holding sheet material 12 to the material sheet 111 with a pressure-sensitive adhesive or adhesive. The laminated sheet 19 is wound into a roll. The material sheet 111 and the holding sheet material 12 can be bonded together using a press, roller, ultrasonic horn, or the like that can apply pressure or heat and pressure. The holding sheet material 12 may be a sheet material on which an adhesive layer or adhesive layer is previously formed, or an adhesive layer or adhesive layer may be formed on a non-adhesive sheet material.

[0050] In the cutting step, the blade 24 of the upper die 23 is lowered on the lower die 22 of the press device 15 to vertically cut into the material sheet 111 of the laminate sheet 19. Specifically, the rolled laminate sheet 19 is placed on the reel 51 of the production line 50 shown in FIG. 5. The laminate sheet 19 is then unwound in the longitudinal direction and passed through the press device 15 with the material sheet 111 facing upward. In the press device 15, the press cut described above involves a half cut, in which the blade 24 cuts from the top surface of the material sheet 111 halfway through the thickness direction. FIG. 6(b) shows the state after the blade 24 has finished descending. The planar shape of the blade 24 is honeycomb-shaped, corresponding to the planar shape of the notches 16 in the core layer sheet material 11. In the cutting step, as shown in Figure 6 (c), a core sheet 10 is produced which includes a core layer sheet material 11 in which a number of dividing portions 13 are arranged two-dimensionally in a planar view, and a retaining sheet material 12.

[0051] In the press-cutting process, as shown in Fig. 6(a), a portion 29 of the surface of the material sheet 111 that is first contacted by the tip of the blade 24 is pressed in. The area around this portion 29 is then plastically deformed. As a result, after the press-cutting process, a chamfered portion 13c is formed on the outer periphery of the dividing portion 13 as a trace of the plastic deformation, as shown in Fig. 6(c).

[0052] In addition, in the present embodiment, as shown in FIG. 5, the long core material sheet 10 is cut into a plurality of core material sheets 10 with a predetermined length by the cutter 28, but a product in which the core material sheet 10 is wound in a roll shape may also be used. Further, in the present embodiment, the press device 15 in which the upper die 23 moves up and down with respect to the lower die 22 is used, but a press device that performs a press cut by the rotation pressure of a rotary die (die cut roll) may also be used. Further, in the present embodiment, the attachment step is performed before the cutting step, but the attachment step may be performed after the cutting step. In this case, the holding sheet material 12 may be attached to the surface 11f side (the opening side of the notch 16) of the core material sheet 10, or the holding sheet material 12 may be attached to the back surface 11b side of the core material sheet 10.

[0053] [Method for manufacturing composite material] A method for manufacturing the composite material 30 will be described.

[0054] <Method for manufacturing composite material shown in FIG. 3(a)> The method for manufacturing the composite material 30 shown in FIG. 3(a) includes a transfer step of transferring the core material layer sheet material 11 of the core material sheet 10 to the first skin material sheet 31A, and a lamination step of laminating the second skin material sheet 32A on the core material layer sheet material 11, which are performed in this order. Each skin material sheet 31A, 32A is made of the above-described skin materials 31, 32, and for example, a semi-cured prepreg (prepreg sheet) can be used.

[0055] In the transfer step, as shown in Fig. 7(a), the core layer sheet 10 is placed on the first skin sheet 31A on the mold 25 with the core layer sheet 11 facing away from it. Next, as shown in Fig. 7(b), the core layer sheet 11 of the core layer sheet 10 is laminated and attached to the first skin sheet 31A (attachment step). The first skin sheet 31A has an adhesive surface. Then, as shown in Fig. 7(c), the holding sheet 12 is peeled off from the core layer sheet 11 (sheet peeling step). Since the adhesive strength of the first skin sheet 31A to the core layer sheet 11 is greater than the adhesive strength of the holding sheet 12 to the core layer sheet 11, the core layer sheet 11 is transferred from the holding sheet 12 to the first skin sheet 31A.

[0056] Next, in the lamination step, a second skin sheet 32A is laminated and attached to the core layer sheet 11 of the laminate 30A obtained in the transfer step, as shown in Fig. 7(d). The second skin sheet 32A has an adhesive surface. This results in a laminate 30B in which the core layer sheet 11 is sandwiched between the pair of skin sheets 31A, 32A.

[0057] Next, if the matrix of the prepreg used for each skin sheet 31A, 32A is a thermosetting resin (e.g., epoxy resin), a molding step (curing step) is performed. In the molding step, the laminate 30B obtained in the lamination step is sealed using a bagging film. The laminate 30B sealed in the bagging film is then heated in an autoclave at a predetermined temperature and pressure (e.g., 130°C, 0.2 MPa) for a predetermined time (e.g., 2 hours). During this heating process, the semi-cured skin sheets 31A, 32A become fully cured skins 31, 32. As a result, a composite material 30 is completed that has been cured into a predetermined shape.

[0058] When the matrix of the prepreg used for each of the skin sheets 31A, 32A is a thermoplastic resin (for example, polyamide resin, polypropylene resin, or polyether ether ketone resin), after a molding step such as pressurized and heated press molding, a curing step is carried out by cooling the laminate 30B in an atmosphere at a temperature lower than the curing temperature of the matrix (for example, room temperature), and the composite 30 is completed.

[0059] It is possible to manufacture a composite material 30 having a curved portion 35 in a cross-sectional view (see FIG. 8( a)). When manufacturing such a composite material 30, the opening side (the side opposite to the valley) of the slit 16 in the core layer sheet material 11 can be made to face the bulging side of the curved portion 35 in a cross-sectional view. When manufacturing a composite material 30 having multiple curved portions 35 in a cross-sectional view, the opening side of the slit 16 in the core layer sheet material 11 can be made to face the bulging side of the curved portion 35 with the largest curvature in a cross-sectional view.

[0060] The manufacturing method of the composite material 30 in this case will be described using an example in which the entire composite material 30 has a curved portion 35. First, when manufacturing the composite material 30 on a mold 25 (see FIG. 8(b)) having a curved (concave) surface on the front side, in the transfer step, the core layer sheet material 11 side of the core sheet 10 is attached to the first skin sheet 31A on the mold 25, as in FIG. 7, and then the retaining sheet material 12 is peeled off. Then, in the lamination step, a second skin sheet 32A is laminated to obtain the laminate material 30B shown in FIG. 8(b).

[0061] On the other hand, when the composite material 30 is manufactured on a mold 25 (see FIG. 8( c)) having a curved surface (convex surface) on the front side, a preparatory step of preparing an intermediate transfer sheet 110 shown in FIG. 8( d) is first performed during the transfer step. In the preparatory step, the front surface 11f of the core layer sheet material 11 of the core sheet 10 is attached to the sheet material 17, and the holding sheet material 12 is peeled off, thereby transferring the core layer sheet material 11, and the intermediate transfer sheet 110 is produced. In the intermediate transfer sheet 110, the core layer sheet material 11 is releasably attached to the sheet material 17 using an adhesive. Then, the back surface 11b of the core layer sheet material 11 of the intermediate transfer sheet 110 is attached to the first skin sheet 31A on the mold 25, and the sheet material 17 is peeled off, thereby transferring the core layer sheet material 11. Then, in the laminating step, a second skin sheet 32A is laminated to obtain the laminate 30B shown in FIG. 8(c).

[0062] <Method for manufacturing the composite material shown in FIG. 3(c) or FIG. 3(d)> The method for manufacturing the composite material 30 shown in FIG. 3(c) or FIG. 3(d) involves carrying out a first lamination step of laminating the core sheet 10 onto the first skin sheet 31A, and a second lamination step of laminating the second skin sheet 32A onto the core sheet 10, in this order.

[0063] In the first lamination step, as shown in Fig. 9(a), the core sheet 10 is placed apart from the first skin sheet 31A on the mold 25. Next, as shown in Fig. 9(b), the core sheet 10 is laminated and attached to the first skin sheet 31A. Note that, although the retaining sheet material 12 is attached to the first skin sheet 31A in Fig. 9(b), the core layer sheet material 11 may also be attached to the first skin sheet 31A.

[0064] Next, in the second lamination step, a second skin sheet 32A is laminated and attached to the core sheet 10 of the laminate 30A obtained in the first lamination step, as shown in Fig. 9(c) , to obtain a laminate 30B in which the core sheet 10 is sandwiched between the pair of skin sheets 31A, 32A.

[0065] Following the second lamination step, if the matrix of the prepreg used for each skin sheet 31A, 32A is a thermosetting resin, the molding step described above is performed. If a retaining sheet material 12 that does not melt during the heating process of this molding step is used, the composite material 30 shown in Figure 3(c) is produced. On the other hand, if a retaining sheet material 12 that melts during the heating process of this molding step is used, the composite material 30 shown in Figure 3(d) is produced.

[0066] In the case of a thermoplastic resin, the molding and curing steps are performed as described above. When a retaining sheet material 12 that does not melt during the heating process of the molding step is used, the composite material 30 shown in Fig. 3(c) is produced. On the other hand, when a retaining sheet material 12 that melts during the heating process of the molding step is used, the composite material 30 shown in Fig. 3(d) is produced.

[0067] 3(c) or 3(d), the above-described preparation step is not necessary when a concave or convex mold 25 is used. In the case of a concave mold 25, the core layer sheet material 11 side of the core sheet 10 is attached to the first skin sheet 31A on the mold 25 during the first lamination step. On the other hand, in the case of a convex mold 25, the retaining sheet material 12 side of the core sheet 10 is attached to the first skin sheet 31A on the mold 25 during the first lamination step.

[0068] [Effects of the Present Embodiment] In the present embodiment, the core layer sheet material 11 used as the core layer 33 of the composite material 30 has a plurality of divided portions 13, each divided by a slit 16 formed by half-cutting on one side 11f, arranged two-dimensionally in a plan view. When the core layer sheet material 11 is bent, the slits 16 expand and contract (see FIG. 8( a)). Therefore, although the core layer sheet material 11 is made of a material with poor toughness (hard foam), it is easier to bend than unprocessed sheet material and can conform to a curved surface with a large curvature. Furthermore, because the divided portions 13 formed by half-cutting are connected to each other, some of the divided portions 13 are less likely to separate when the core layer sheet material 11 is attached to the skin sheet 31A. Furthermore, because the half-cutting is performed by press cutting or laser cutting, productivity is high. According to the present embodiment, a composite material 30 can be provided that is easily molded into a three-dimensional shape and highly productive.

[0069] In this embodiment, the retaining sheet material 12 is attached so as to cover the other surface 11b (or one surface 11f) of the core layer sheet material 11, and adjacent divided portions 13 are connected to each other by the above-mentioned connecting portions 14. This makes it easy to handle the core sheet 10 including the core layer sheet material 11, and the core layer sheet material 11 can be easily placed on the skin sheet 31A without some of the divided portions 13 coming off. According to this embodiment, it is possible to provide a composite material 30 that is even easier to manufacture.

[0070] Furthermore, in this embodiment, the slits 16 have a V-shaped valley shape in cross section. Unlike this embodiment, if the bottom surface of the slits 16 has a certain width (the width of the slits 16 in a planar view) at the bottom of the valley (as in Patent Document 2, where the slits 16 do not have a V-shaped valley shape), for example, when the core layer sheet material 11 is bent so that the surface 11f side bulges, the bending moment at the position where the bottom surface of the slits 16 intersects with the side of the dividing section 13 tends to be large. In contrast, in this embodiment, the bending moment at this position is suppressed from being large. Therefore, the core layer sheet material 11 is less likely to break when bent, and there are fewer restrictions on the bending range when forming it into a three-dimensional shape. According to this embodiment, a composite material 30 with even better formability into a three-dimensional shape can be provided.

[0071] In this embodiment, prepreg is used as the material for each of the skin materials 31, 32. Therefore, during the heat treatment, the resin of the prepreg flows into the slits 16, filling the slits (gaps) 16 in the core material layer 33. The resin that flows in hardens in the gaps 16. The hardened resin in the gaps 16 contains short fibers that flowed in from the prepreg together with the resin. Therefore, localized reduction in the strength of the composite material 30 can be suppressed.

[0072] [First Modification of the Present Embodiment] In this modification, half-cut notches 16 are formed in the material sheet 111 by laser cutting, rather than by press cutting. As in the above-described embodiment, the laser-cut notches 16 have a V-shaped valley shape in cross section that widens from the valley bottom toward the surface side.

[0073] In manufacturing the core sheet 10, for example, a laser cutting machine 60 (see FIG. 10( a)) is used that can move a laser irradiation head 61 in a plane along the intended shape of the incision 16 in a plan view. When performing laser cutting with the laser cutting machine 60, the intensity of the laser light L emitted from the laser irradiation head 61 is adjusted so that the material sheet 111 is half-cut. Specifically, the intensity of the laser light L is adjusted based on the thickness and material (hardness, etc.) of the material sheet 111, the movement speed of the laser irradiation head 61, etc.

[0074] In the cutting step, as shown in FIGS. 10( b) and 10(c), the laser irradiation head 61 irradiates the material sheet 111 on the base 122 with laser light L while moving along the intended shape of the incisions 16. This produces a core layer sheet material 11 in which a plurality of division sections 13, each divided from the other on one side 11f by the incisions 16 formed by half-cuts in the thickness direction, are arranged two-dimensionally in a planar view. During the planar movement of the laser irradiation head 61, there are locations where the laser irradiation head 61 passes above twice (corners of the polygonal incisions 16 surrounding the division sections 13). Because the corners are irradiated with laser light L twice, through-holes 16P (see FIG. 11(c)) may be formed. Although a holding sheet material 12 is attached to the underside of the material sheet 111 shown in FIG. 10, the holding sheet material 12 may be omitted.

[0075] In this modified example, the core layer sheet material 11 has discolored areas B where the laser light L was irradiated, as a trace of the half-cutting made by laser cutting. When a resin material such as a hard resin foam is used for the core layer sheet material 11, the color of the discolored areas B is, for example, reddish. Figures 11(a)-(c) are photographs of the core layer sheet material 11 in which the half-cutting was made by laser cutting. Figure 11(b) is a photograph of the front surface 11f side of the core layer sheet material 11, and Figure 11(c) is a photograph of the back surface 11b side of the core layer sheet material 11. In Figures 11(a)-(c), the discolored areas B are formed mainly on the side of the slit 16, as well as on the edge on the opening side of the slit 16 and in the valley bottom. Furthermore, on the back surface 11b of the core layer sheet material 11, through holes 16P are formed at the corners of the hexagonal notches 16, and the through holes 16P, together with the discolored portion B, are traces of the laser half-cut. Although not shown, when a wood material is used for the core layer sheet material 11, the discolored portion B will have a color similar to that of the burnt surface of the wood material (for example, a color slightly darker than the original color of the wood material).

[0076] Although FIG. 10 shows the notch 16 formed by a single laser cut, as shown in FIG. 12 , the notch 16 may be formed by multiple laser cuts (two cuts in FIG. 12 ). In this case, the intensity of the laser light L, etc., is adjusted so that the cut depth of the material sheet 111 by each laser cut is small. FIG. 12( a ) shows the first laser cut. In the first laser cut, a shallow notch 16A is formed in the material sheet 111 (the material of the core layer sheet material 11) so that the cut depth is less than half the depth of the notch 16 to be formed. FIG. 12( b ) shows the second laser cut. In the second laser cut, the laser irradiation head 61 passes through the same position (position of the notch 16A) as in the first laser cut in a plan view, and the laser light L is irradiated at the same position as in the first laser cut. Then, the material sheet 111 is cut to the intended depth to form the notch 16.

[0077] Here, because the material of the material sheet 111 is not uniform and the output of the laser light may fluctuate, if a deep notch 16 is to be formed by a single laser cut, a portion of the material sheet 111 may be unintentionally fully cut from the front to the back, and some of the dividing sections 13 may fall off during handling of the core layer sheet material 11. In contrast, when the notch 16 is formed by multiple laser cuts, the variation in the cut depth per cut is small, and the above-mentioned full cut is unlikely to occur unintentionally. Therefore, it is possible to easily manufacture a core layer sheet material 11 having a large depth d of the notch 16, excellent formability into a three-dimensional shape, and in which some of the dividing sections 13 are unlikely to fall off during handling.

[0078] [Second Modification of the Present Embodiment] In this modification, the core sheet 10 does not have a retaining sheet material 12, as shown in Figure 13. The core sheet 10 is composed only of the core layer sheet material 11 of the above-mentioned embodiment. In addition, in the core layer sheet material 11, adjacent divided portions 13 are connected to each other by connecting portions 14 in the thickness range from the bottom of the valley of the slits 16 in the core layer sheet material 11 to the back surface 11b (other surface 11b) of the core layer sheet material 11. The core layer sheet material 11 consists of the above-mentioned sheet-like portion 11s and a number of divided portions 13 (plate-like portions 13) integrated with the sheet-like portion 11s.

[0079] The thickness D of the core layer sheet material 11 can be, for example, less than 4 mm (for example, 3 mm or less or 2 mm or less) as in the above-described embodiment. Also, the depth d of the slits 16 in the core layer sheet material 11 can be 60% or more (preferably 70% or more, more preferably 80% or more) of the thickness D of the core layer sheet material 11 as in the above-described embodiment.

[0080] The composite material 30 manufactured using the core sheet 10 has the same configuration as the composite material 30 in Figures 3(a) and 4, and includes a core layer sheet material 11 (core layer 33), a first skin material 31 laminated on the core layer sheet material 11, and a second skin material 32 laminated on the core layer sheet material 11 on the side opposite to the first skin material 31.

[0081] <Method for manufacturing core sheet of second modified example> The method for manufacturing core sheet 10 of this modified example involves a cutting step in which notches 16 are formed by half-cutting (half-cutting by press cutting or laser cutting) on ​​the surface side (one side) of material sheet 111, thereby producing core layer sheet material 11 in which a number of divided sections 13, which are separated from each other on the surface 11f, are arranged two-dimensionally in a planar view.

[0082] In the cutting step, a press cut is performed by lowering the blade 24 of the upper mold 23 to vertically cut into the material sheet 111 on the lower mold 22 of the press device 15. Specifically, in the production line 50 shown in FIG. 5, a roll-shaped material sheet 111 is placed on a reel 51 instead of the laminated sheet 19. The material sheet 111 is then unwound in the longitudinal direction and passed through the press device 15. In the press device 15, half cuts are performed as the above-mentioned press cut. FIG. 14(b) shows the state after the blade 24 has finished descending. The planar shape of the blade 24 is honeycomb-shaped and corresponds to the planar shape of the slits 16 in the core layer sheet material 11. In the cutting step, as shown in FIG. 14(c), a core sheet 10 is produced from the core layer sheet material 11 in which multiple division portions 13 are two-dimensionally arranged. The core layer sheet material 11 of this modified example also has traces (chamfered portions 13c) of the half cuts made by press cutting. In this modified example, the half cut can also be performed by laser cutting. In this case, the core layer sheet material 11 has discolored portions B as the above-mentioned marks.

[0083] <Method for manufacturing composite material according to second modified example> The method for manufacturing the composite material 30 includes a first lamination step of laminating the core sheet 10 onto the first skin sheet 31A, and a second lamination step of laminating the second skin sheet 32A onto the core sheet 10, in this order.

[0084] In the first lamination step, as shown in Fig. 15(a), the core sheet 10 is placed on the mold 25 at a distance from the first skin sheet 31A. Next, as shown in Fig. 15(b), the core sheet 10 is laminated and attached to the first skin sheet 31A. Note that, although the front surface 11f of the core layer sheet material 11 is attached to the first skin sheet 31A in Fig. 15(b), the back surface 11b of the core layer sheet material 11 may also be attached to the first skin sheet 31A.

[0085] 15(c), a second skin sheet 32A is laminated and attached to the core sheet 10 of the laminate 30A obtained in the first lamination step, thereby obtaining a laminate 30B in which the core sheet 10 is sandwiched between the pair of skin sheets 31A, 32A.

[0086] Following the second lamination step, if the matrix of the prepreg used for each of the skin sheets 31A, 32A is a thermosetting resin, the above-mentioned molding step is carried out. If the matrix is ​​a thermoplastic resin, the above-mentioned molding step and curing step are carried out.

[0087] In the first lamination step, when the composite material 30 is manufactured on a concave mold 25 (see FIG. 8(b)), the front surface 11f of the core layer sheet material 11 may be attached to the first skin sheet 31A on the mold 25. On the other hand, when the composite material 30 is manufactured on a convex mold 25 (see FIG. 8(c)), the back surface 11b of the core layer sheet material 11 may be attached to the first skin sheet 31A on the mold 25.

[0088] <Advantages of this Modification> In this modification, the retaining sheet material 12 is not used for the core sheet 10. Therefore, it is possible to provide a composite material 30 that has good formability into a three-dimensional shape, has a simpler structure than the above-described embodiment, and is easy to manufacture.

[0089] In this modification, as shown in Fig. 16, notches 26 may be formed on the back surface 11b of the core layer sheet material 11. In this case, as shown in Fig. 17, the notches 26 can be formed in a honeycomb shape in plan view so as not to completely overlap with the notches 16 on the front surface 11f. In the case of Fig. 17, the positions where the notches 16 and the notches 26 overlap are the positions of the corners of the dividing sections 13 in plan view, so that a decrease in strength of the connecting portions 14 described above is suppressed.

[0090] [Third Modification of the Present Embodiment] In this modification, as shown in Figure 18, half-cut slits 26 are also formed on the back surface 11b of the core layer sheet material 11 in the core sheet 10. On the front surface 11f of the core layer sheet material 11, multiple divisions 13a separated from each other by slits 16 are two-dimensionally arranged, and on the back surface 11b of the core layer sheet material 11, multiple divisions 13b separated from each other by slits 26 are two-dimensionally arranged. The slits 16 are provided around the entire periphery of each division 13a. The slits 26 are provided around the entire periphery of each division 13b. The slits 16 and 26 are formed to overlap each other in a plan view, and the outer peripheries of the divisions 13a and 13b overlap each other in a plan view. In a cross-sectional view, the slits 16 and 26 have a V-shaped valley shape that widens from the valley bottom toward the opening side. The core sheet 10 shown in FIG. 18 includes a core layer sheet material 11 and a supporting sheet material 12, but the supporting sheet material 12 may be omitted.

[0091] The manufacturing method of the core sheet 10 of this modified example includes a front-side cutting step in which the front surface of the material sheet 111 is cut by half-cutting (press cutting or laser cutting) to form multiple divisions 13a with incisions 16; a back-side cutting step in which the back surface of the material sheet 111 is cut by half-cutting (press cutting or laser cutting) to form multiple divisions 13b with incisions 26; and an attachment step in which the holding sheet material 12 is attached to the material sheet 111. The front-side cutting step and the back-side cutting step may be performed in either order, or simultaneously. The attachment step is performed after the cutting process on the side of the material sheet 111 to which the holding sheet material 12 is attached. In the core layer sheet material 11 shown in FIG. 18 , traces (chamfered portions 13c) of the half-cuts made by press cutting remain on both the front and back surfaces. If the half-cuts are made by laser cutting, discolored portions B remain as traces.

[0092] [Fourth Modification of the Present Embodiment] In this modification, in the core layer sheet material 11, some of the divisions separating the multiple divisions 13 are formed by half-cut slits 16, and the remaining divisions are formed by full-cut through-holes 16P. Each division 13 is formed by a division having a half-cut portion. Examples of this configuration are the core layer sheet material 11 shown in FIG. 3(b) and the core layer sheet material 11 shown in FIG. 12, in which the through holes 16P correspond to the through-holes. Note that the through-holes 16P may be linear in a plan view of the core layer sheet material 11, as shown in FIGS. 19(a) and 19(b). In FIGS. 19(a) and 19(b), the black portions represent the through-holes 16P. Note that the through-holes 16P are formed so that some of the divisions 13 are not completely separated from the core layer sheet material 11. In other words, the through-holes 16P are formed so that all of the divisions 13 are integrated.

[0093] In FIG. 19( a), by providing multiple through-holes 16P so that they extend in the same direction, the formability into a three-dimensional shape is improved in the direction in which the through-holes 16P are arranged (from the upper left to the lower right in FIG. 19( a)). In FIG. 19( b), the through-holes 16P are provided except at the corners of the polygonal (hexagonal) divisions surrounding each division 13. The reason for this is that, for example, when a wood material is used for the core layer sheet material 11, if the linear portions of the polygonal divisions are connected, there is a risk of long burrs occurring along the linear portions when the linear portions break during three-dimensional forming. In contrast, in FIG. 19( b), the formability into a three-dimensional shape can be ensured while suppressing the occurrence of burrs when a wood material is used for the core layer sheet material 11.

[0094] Regarding the method of forming the through-holes 16P, when the notches 16 are formed by press cutting, the height of the blade 24 can be partially increased to form the through-holes 16P during press cutting.

[0095] Regarding the method of forming the through-holes 16P, when the incisions 16 are formed by laser cutting, the through-holes 16P can be formed by extending the irradiation time of the laser light L (e.g., by having the laser irradiation head 61 pass twice) or increasing the intensity of the laser light L relative to the area where the incisions 16 are to be formed during the planar movement of the laser irradiation head 61. Furthermore, in the case of a thick core layer sheet material 11, the laser irradiation head 61 is moved planarly so that the laser irradiation head 61 passes over the same area multiple times (so that multiple laser cuts are performed). In this case, for example, the half-cut incisions 16 can be formed by turning on the laser light irradiation during the first pass of the laser irradiation head 61 and turning off the laser light irradiation during the second pass of the laser irradiation head 61, and the through-holes 16P can be formed by turning on the laser light irradiation during both the first and second passes of the laser irradiation head 61.

[0096] [Fifth Modification of the Present Embodiment] In this modification, a plurality of adhesive layers 40 (a large number of adhesive layers 40) are laminated on the surfaces 11f, 11b of the core layer sheet material 11 that come into contact with the first skin sheet 31A in the transfer step (or the lamination step when the composite 30 is manufactured using the procedure of FIG. 9 (two lamination steps)). The adhesive layers 40 are arranged on one surface 11f, 11b of the core layer sheet material 11 in a dispersed state at a distance from each other.

[0097] 20, each adhesive layer 40 is made of a thin film of adhesive and is formed, for example, in a dot shape in plan view. When laminated on the front surface 11f of the core layer sheet material 11, each adhesive layer 40 covers a part of the front surface of the dividing section 13, and when laminated on the back surface 11b of the core layer sheet material 11, each adhesive layer 40 covers a part of the back surface corresponding to the dividing section 13. Note that the adhesive layer 40 is not limited to a dot shape and may be formed in a line shape in plan view.

[0098] In order to laminate the plurality of adhesive layers 40 on the core layer sheet material 11, an adhesive layer-attached sheet can be used, in which the plurality of adhesive layers 40 are laminated, for example, by printing, on one side of an easily peelable sheet (for example, a resin sheet in which a PET film has been silicone-treated). The adhesive layer 40 side of the adhesive layer-attached sheet is attached to the material sheet 111 before the cutting step or the material sheet 111 (core layer sheet material 11) after the cutting step, and the easily peelable sheet is peeled off, thereby transferring the plurality of adhesive layers 40 to the material sheet 111.

[0099] A protective sheet material 18 is laminated on surfaces 11f and 11b of the core layer sheet material 11 on which the multiple adhesive layers 40 are laminated, covering the multiple adhesive layers 40. The protective sheet material 18 may be, for example, a resin sheet (or film) or a paper sheet (or film). The thickness of each adhesive layer 40 is smaller than that of the holding sheet material 12 and the protective sheet material 18.

[0100] In the core layer sheet material 11 shown in Figure 20(a), multiple adhesive layers 40 are laminated on the surface 11f of the core layer sheet material 11. As with Figure 7, the core layer sheet material 11 shown in Figure 20(a) is laminated and attached to the first skin sheet 31A at the surface 11f during the transfer step. When prepreg is used as the first skin sheet 31A, the surface may have low adhesiveness, while when a woven fabric of reinforcing fibers (carbon fiber, glass fiber, etc.) is used as the first skin sheet 31A, the surface may not have adhesiveness. In these cases, the multiple adhesive layers 40 maintain the planar position of the core layer sheet material 11 on the first skin sheet 31A.

[0101] In Fig. 20(a), there is a gap between the surface 11f of the core layer sheet material 11 and the protective sheet material 18, but this gap is drawn for convenience, and in reality the protective sheet material 18 substantially contacts the core layer sheet material 11. This also applies to Figs. 20(b) to 20(d).

[0102] In the core layer sheet material 11 shown in Figure 20(b), a plurality of adhesive layers 40 are laminated on the back surface 11b of the core layer sheet material 11. In Figure 20(b), the retaining sheet material 12 also serves as the protective sheet material 18 that covers the plurality of adhesive layers 40, but it is also possible to laminate the retaining sheet material 12 on the front surface 11f of the core layer sheet material 11 and laminate the protective sheet material 18 on the back surface 11b of the core layer sheet material 11.

[0103] 20(b), the back surface 11b of the core layer sheet material 11 is laminated and attached to the first skin sheet 31A during the transfer step, as in the case of Fig. 8(c). In this case, the planar position of the core layer sheet material 11 on the first skin sheet 31A is also maintained by the adhesive layers 40.

[0104] In addition, a plurality of adhesive layers 40 (a large number of adhesive layers 40) may be laminated on the surfaces 11f and 11b of the core layer sheet material 11 that will come into contact with the second skin sheet 32A in the lamination step in order to maintain the planar position of the second skin sheet 32A relative to the core layer sheet material 11. In this case, as shown in Fig. 20(c) , a plurality of adhesive layers 40 (a large number of adhesive layers 40) are laminated on each of the front surface 11f and the back surface 11b of the core layer sheet material 11.

[0105] Furthermore, as shown in FIG. 20( d ), a plurality of adhesive layers 40 (a large number of adhesive layers 40 ) may be laminated on the surface 11 f of the core layer sheet material 11 that does not have the holding sheet material 12 .

[0106] In addition, when multiple adhesive layers 40 are not provided, in order to impart or strengthen the initial adhesive strength, it is conceivable to form an adhesive layer using double-sided adhesive tape or spray glue over a wide area on one side of the skin sheets 31A, 32A or the core layer sheet material 11. Compared to such adhesive layers, when multiple adhesive layers 40 are provided partially, the adhesive strength of the interface (the interface between the skin sheets 31A, 32A and the core layer sheet material 11) formed by the matrix resin of the prepreg or the resin of the RTM molding is less likely to be interfered with by the adhesive layer.

[0107] [Other Modifications] In the above-described embodiment and each modification (hereinafter referred to as "embodiments, etc."), the composite material 30 has one core layer 33, but the composite material 30 may have multiple core layers 33. In this case, when manufacturing the composite material 30, a sheet material such as a prepreg or a sheet-like adhesive may be provided between the core layers 33. Furthermore, the composite material 30 may be manufactured by stacking multiple canapé-structured laminates each having a core layer sheet material 11 and a skin material 31 to which the core layer sheet material 11 is attached.

[0108] In embodiments, all dividing sections 13 in the core layer sheet material 11 (core layer 33) do not have to have the same planar shape and size, and the planar shape and size of a dividing section 13 may be different from other dividing sections 13 depending on the curvature of the portion in the composite material 30.

[0109] In the embodiments, a woven fabric of reinforcing fibers may be used for the skin sheets 31A, 32A that form the skins 31, 32. In this case, multiple adhesive layers 40 as shown in FIG. 20 may be provided on one or both sides of the core layer sheet material 11. This allows the laminate 30B to be easily obtained using the same procedure as that shown in FIG. 7, 9, or 15. Then, by RTM molding or the like, a fluid resin is supplied from the outside to the laminate 30B and the resin is cured, thereby obtaining the composite 30.

[0110] In the embodiment, the composite material 30 may have a canapé structure by omitting one of the skin materials 31, 32.

[0111] The present invention is applicable to core sheets and the like used in the production of composite materials.

[0112] REFERENCE SIGNS LIST 10 Core sheet 11 Core layer sheet material 12 Retaining sheet material 13 Divided portion 13c Chamfered portion (trace) 16 Slit 30 Composite material 31, 32 Skin material 33 Core layer

Claims

1. A core sheet used in the manufacture of a composite material, The sheet material for the core layer is a single layer of sheet material made only of a material used for a core layer of the composite material, and a plurality of divided sections, which are formed by half-cutting the sheet material in the thickness direction to a point halfway through the thickness direction and dividing one surface side of the sheet material into a plurality of divided sections, are arranged two-dimensionally in a plan view; The sheet material for the core layer has a trace that the half cut is made by press cutting or laser cutting.

2. 2. The core sheet according to claim 1, further comprising a retaining sheet material attached so as to cover one surface or the other surface of the core layer sheet material.

3. The core layer sheet according to claim 1, wherein adjacent divided portions of the core layer sheet material are connected to each other by a portion in the thickness range from the bottom of the valley of the slit to the other surface of the core layer sheet material.

4. A core material sheet as described in any one of claims 1 to 3, wherein in the sheet material for the core layer, a portion of the dividing points that divide the multiple dividing sections from each other is formed by a notch made by the half cut, and the remainder of the dividing points is formed by a through hole made by a full cut.

5. The core sheet according to claim 1 , wherein the slits have a V-shaped valley shape in a cross-sectional view.

6. 4. The core sheet according to claim 1, wherein the depth of the cut is 60% or more of the thickness of the core layer sheet material.

7. A sheet material for a core layer according to any one of claims 1 to 3; A composite material comprising a skin material laminated on the core layer sheet material.

8. The composite material has a curved portion in a cross-sectional view, The composite material according to claim 7 , wherein in the curved portion, an opening side of the slit in the core layer sheet material faces a bulging side of the curved portion in a cross-sectional view.

9. A core sheet used in the manufacture of a composite material, a sheet material for a core layer, the sheet material being one layer made of only a material used for a core layer of the composite material, the sheet material being two-dimensionally arranged in a plan view in which a plurality of division sections are formed by dividing one surface side of the sheet material into parts by half-cutting the sheet material in the thickness direction to a midpoint in the thickness direction; The core sheet comprises a retaining sheet material attached so as to cover one surface or the other surface of the core layer sheet material.

10. A method for producing a core sheet including a core layer sheet material used in a core layer of a composite material, comprising: a cutting step is performed to produce a sheet material for a core layer, in which a half cut is made in the thickness direction to a midpoint in the thickness direction in one layer of sheet material made only of the material used for the core layer, so that one surface side of the sheet material is divided into a plurality of divided portions, which are arranged two-dimensionally in a plan view; The method for producing a core sheet, wherein the half-cutting is performed by press cutting or laser cutting.

11. A method for producing a composite material, comprising: producing a composite material in which the sheet material for a core layer according to claim 10 is laminated on a skin material, a lamination step of laminating the core sheet onto a skin sheet, which is a material for the skin; and a curing step of curing the skin sheet.

12. A method for producing a composite material, comprising the steps of: a step of attaching the core sheet to a skin sheet, which is a material for a skin of the composite material; the core sheet includes a core layer sheet material, the core layer sheet material being used for a core layer of the composite material, the core layer sheet material having a plurality of divided sections, each divided into two parts by half-cutting in the thickness direction of the core layer sheet material in a two-dimensional arrangement in a plan view, and a retaining sheet material attached to cover one or the other surface of the core layer sheet material; The method for manufacturing a composite material includes, after the attaching step, performing a sheet peeling step of transferring the core layer sheet material to the skin sheet by peeling the retaining sheet material from the core layer sheet material.