Laminated structure

Abstract

To provide a laminated structure that can maintain high bending rigidity. [Solution] A laminated structure 10 having a hollow structure 20 having a core layer 40 in which a plurality of cells S are arranged in parallel inside, and an aluminum sheet 30 joined to the hollow structure 20, wherein the core layer 40 is formed by molding a core sheet of thermoplastic resin, the elastic modulus of the core sheet is 1000 MPa or more, and the ratio of the elastic modulus of the aluminum sheet 30 to the elastic modulus of the core sheet is 20 or more and 80 or less.

Description

[Technical Field]

[0001] The present invention relates to a laminated structure comprising a hollow structure and an aluminum sheet. [Background technology]

[0002] Hollow structures with multiple cells arranged side by side inside are lightweight yet possess moderate strength, and are sometimes used as components for various vehicles and building materials. The hollow structure described in Patent Document 1 has a structure in which skin layers are joined to both sides of a core layer that forms a honeycomb structure, and multiple hexagonal cells are arranged side by side inside the core layer. Here, the core layer is formed by forming a textured sheet material with convex bulges by vacuum forming a flat core sheet, and then folding the textured sheet material. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2008-520456 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, to improve the bending rigidity of a hollow structure, it is conceivable to create a laminated structure by bonding an aluminum sheet to the hollow structure. After diligent research by the inventor, it was found that the bending rigidity of the laminated structure is influenced by the elastic modulus of the core sheet, which is the molding material for the core layer.

[0005] Therefore, the present invention aims to provide a laminated structure that can maintain high bending rigidity. [Means for solving the problem]

[0006] One of the above solutions is a laminated structure having a hollow structure with a core layer having a plurality of cells arranged in parallel inside, and an aluminum sheet joined to the hollow structure, wherein the core layer is formed by molding a core sheet of thermoplastic resin, the elastic modulus of the core sheet is 1000 MPa or more, and the ratio of the elastic modulus of the aluminum sheet to the elastic modulus of the core sheet is 20 or more and 80 or less.

[0007] The second solution described above is one in which the thickness of the core sheet is 0.16 mm or more, the thickness of the aluminum sheet is 0.11 mm or more, and the ratio of the thickness of the aluminum sheet to the thickness of the core sheet is 0.4 or more and 3.0 or less.

[0008] The third solution described above is that the diagonal angle of the cells is between 45 degrees and 75 degrees. The fourth solution described above is that the cavity volume of the cell is 400 mm 3 More than 3000mm 3 The following applies: [Effects of the Invention]

[0009] According to the present invention, high bending rigidity can be maintained in the laminated structure. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1(a) is a partial perspective view of the laminated structure, Figure 1(b) is a cross-sectional view along the α-α line in Figure 1(a), and Figure 1(c) is a cross-sectional view along the β-β line in Figure 1(a). [Figure 2] Figure 2(a) is a partial perspective view of the sheet material constituting the core layer, Figure 2(b) is a partial perspective view showing the sheet material in the process of being folded, and Figure 2(c) is a partial perspective view showing the sheet material in the folded state. [Figure 3] A graph showing the relationship between the elastic modulus of the core sheet and the bending stiffness of the laminated structure. [Figure 4] A schematic diagram illustrating the formula for calculating the bending stiffness (EIx) of a laminated structure, excluding shear, and its various parameters. [Figure 5]Calculation formula for bending rigidity (EIy) including shear of the laminated structure, and schematic diagram showing each parameter. [Figure 6] Calculation formula for bending deformation amount (δ) of the laminated structure, and schematic diagram showing each parameter. [Figure 7] Graph showing the relationship between the ratio of the elastic modulus of the core sheet to the elastic modulus of the aluminum sheet and the bending rigidity of the laminated structure. [Figure 8] Graph showing the relationship between the thickness of the core sheet and the bending rigidity of the laminated structure. [Figure 9] Graph showing the relationship between the thickness of the aluminum sheet and the bending rigidity of the laminated structure. [Figure 10] Graph showing the relationship between the ratio of the thickness of the aluminum sheet to the thickness of the core sheet and the deflection amount of the laminated structure. [Figure 11] Calculation formula for shear deformation amount (ε) of the laminated structure, and schematic diagram showing each parameter. [Figure 12] Calculation formula for core shear elastic modulus (G) of the laminated structure, and schematic diagram showing each parameter. [Figure 13] Graph showing the relationship between the diagonal angle of the cell and the bending rigidity of the laminated structure. [Figure 14] Graph showing the relationship between the cavity volume of the cell and the bending rigidity of the laminated structure.

Mode for Carrying Out the Invention

[0011] Hereinafter, an embodiment of the laminated structure 10 embodying the present invention will be described according to FIGS. 1 to 14. (Regarding the laminated structure 10) As shown in FIG. 1(a), the laminated structure 10 of the present embodiment includes a hollow structure 20 in which a plurality of column-shaped cells S are arranged side by side inside and has a hollow plate shape as a whole, and aluminum sheets 30 arranged on the upper and lower surfaces of the hollow structure 20. This laminated structure 10 is used, for example, in a place where a predetermined bending rigidity is required, such as a luggage board of an automobile.

[0012] (Regarding the hollow structure 20) As shown in Figures 1(b) and (c), the hollow structure 20 is composed of a core layer 40 in which a plurality of columnar cells S are arranged side by side inside, and a sheet-like skin layer 50 joined to both the upper and lower surfaces of the core layer 40. The core layer 40 is formed by vacuum forming a single thermoplastic resin core sheet into a predetermined shape, and then folding it. The core layer 40 is composed of an upper wall portion 41, a lower wall portion 42, and a side wall portion 43 erected between the upper wall portion 41 and the lower wall portion 42 to divide the cells S into hexagonal prism shapes.

[0013] Here, the core sheet, which is the molding material for the core layer 40, has an elastic modulus of 1000 MPa or higher. If the elastic modulus of the core sheet is less than 1000 MPa, the bending stiffness of the laminated structure 10 using this core sheet will decrease significantly due to the effect of shear. The elastic modulus of the core sheet can be calculated based on "JIS K7161 Method for Determining the Tensile Properties of Plastics".

[0014] Furthermore, the thickness of the core sheet is preferably 0.16 mm or more. If the thickness of the core sheet is less than 0.16 mm, the bending stiffness of the laminated structure 10 using this core sheet will decrease significantly due to the effect of shear. In addition, the resistance to planar compression will decrease, making it more susceptible to collapse.

[0015] As shown in Figures 1(b) and (c), the cells S partitioned within the core layer 40 include a first cell S1 and a second cell S2 with different configurations. As shown in Figure 1(b), in the first cell S1, a two-layer upper wall 41 is provided above the side wall 43. Each layer of this two-layer upper wall 41 is joined to the others. Also in the first cell S1, a single-layer lower wall 42 is provided below the side wall 43. On the other hand, as shown in Figure 1(c), in the second cell S2, a single-layer upper wall 41 is provided above the side wall 43. Also in the second cell S2, a two-layer lower wall 42 is provided below the side wall 43. Each layer of this two-layer lower wall 42 is joined to the others. Furthermore, as shown in Figures 1(b) and (c), adjacent first cells S1 and adjacent second cells S2 are partitioned between each other by two-layer side wall 43. The two-layered sidewalls 43 have portions in the center of the core layer 40 in the thickness direction that are not heat-welded to each other. Therefore, the internal space of each cell S in the core layer 40 is in communication with the internal space of other cells S through the space between the two-layered sidewalls 43.

[0016] As shown in Figure 1(a), the first cells S1 are arranged in a row along the X direction. Similarly, the second cells S2 are arranged in a row along the X direction. The rows of first cells S1 and second cells S2 are arranged alternately in the Y direction, which is perpendicular to the X direction. Both the first cells S1 and the second cells S2 are in the shape of regular hexagonal prisms, and together with the first cells S1 and the second cells S2, the core layer 40 as a whole has a honeycomb structure.

[0017] Here, the cavity volumes of the first cell S1 and the second cell S2, that is, the cavity volumes of the individual cells S that make up the first cell S1 and the second cell S2 respectively, are 400 mm 3 More than 3000mm 3 The following range is preferred: Cavity volume of cell S is 400 mm 3 If the value is less than 3000 mm³, the change in the bending stiffness of the laminated structure 10 is small, but the individual cells S become smaller, and the weight of the hollow structure 20 that makes up the laminated structure 10 increases. Also, if the cavity volume of the cell S is 3000 mm³3 Beyond a certain point, the decrease in bending stiffness due to shear stress on the laminated structure 10 becomes significant.

[0018] Since both the first cell S1 and the second cell S2 in this embodiment are in the shape of a regular hexagonal prism, the volume of the cavity of cell S is (mm 3 ) is "3 × (Length between opposing surfaces of cell S in plan view (mm) CS) 2 It can be calculated using the formula: ×(height of cell S (mm) CH) ÷ 2√3. The length CS between opposing faces of cell S and the height CH of cell S are both the length (internal dimension) of the cavity of cell S (see Figures 4 and 12).

[0019] The relative angle θ in each cell S of the first cell S1 and the second cell S2 is preferably in the range of 45 to 75 degrees. If the relative angle θ of the cell S is less than 45 degrees, the laminated structure 10 will experience a large decrease in bending stiffness due to shear. If the relative angle θ of the cell S exceeds 75 degrees, the change in bending stiffness of the laminated structure 10 will be small, while the weight of the hollow structure 20 constituting the laminated structure 10 will increase with increasing relative angle θ of the cell S. The relative angle θ of the cell S refers to the angle between the line connecting the midpoint of the upper edge (center in the length direction of the edge) of one of the opposing faces and the midpoint of the lower edge of the opposing face, and the upper wall portion 41 or lower wall portion 42 of the cell S, in the case of a regular hexagonal prism cell S of this embodiment (see Figure 12).

[0020] The hollow structure 20 is formed by thermoforming a core sheet of thermoplastic resin. Polypropylene (PP) is preferred as the thermoplastic resin that can be used for the core sheet, but other thermoplastic resins can also be used.

[0021] As shown in Figures 1(a) to 1(c), the hollow structure 20 has sheet-like skin layers 50 heat-sealed to both the upper and lower surfaces of the core layer 40. The skin layers 50 can be made of thermoplastic resin such as polypropylene (PP), and each skin layer 50 can have a thickness of 0.1 to 1.5 mm and be made of a sheet with an elastic modulus of 500 MPa or higher.

[0022] (Regarding aluminum sheet 30) As shown in Figures 1(a) to 1(c), aluminum sheets 30 are bonded to the upper and lower surfaces of the hollow structure 20 configured as described above. These aluminum sheets 30 are bonded to the skin layer 50 of the hollow structure 20 with an adhesive. Here, the term "sheet" in "aluminum sheet 30" includes sheet-like, plate-like, film-like, and foil-like forms. Furthermore, the term "aluminum" includes not only pure aluminum but also aluminum alloys to which manganese, copper, silicon, zinc, magnesium, nickel, etc., have been added.

[0023] The thickness of the aluminum sheet 30 is preferably 0.11 mm or more. If the thickness of the aluminum sheet 30 is less than 0.11 mm, the bending rigidity of the laminated structure 10 will be reduced, making it difficult to use in applications where bending rigidity is required. In addition, the aluminum sheet 30 is more prone to tearing when a localized load is applied.

[0024] The ratio of the thickness of one aluminum sheet 30 to the thickness of the core sheet (thickness of one aluminum sheet 30 / thickness of the core sheet) is preferably between 0.4 and 3.0. If the thickness ratio is less than 0.4, the aluminum sheet 30 becomes relatively thin, resulting in reduced bending rigidity. Furthermore, if the core sheet is too thick, the mass and cost of the laminated structure 10 increase, leading to poor performance efficiency. Also, if the thickness ratio exceeds 3.0, the core sheet becomes relatively thin, resulting in a greater decrease in bending rigidity due to shear. Furthermore, if the aluminum sheet 30 is too thick, the cost and mass of the laminated structure 10 increase, leading to poor performance efficiency.

[0025] The ratio of the elastic modulus (Pa) of the aluminum sheet 30 to the elastic modulus (Pa) of the core sheet (elastic modulus of aluminum sheet 30 / elastic modulus of core sheet) is between 20 and 80. If this ratio of elastic moduli falls below 20, the decrease in bending stiffness due to shear is reduced, but the mass and cost of the laminated structure 10 increase because the elastic modulus of the core sheet is excessively high. If the ratio of elastic moduli exceeds 80, the decrease in bending stiffness due to shear of the laminated structure 10 becomes large. The elastic modulus (Pa) of the aluminum sheet 30 can be calculated based on "JIS Z2241 Tensile Test Method for Metallic Materials".

[0026] Next, the method for manufacturing the laminated structure 10 will be explained with reference to Figure 2. First, the method for manufacturing the hollow structure 20 will be explained. As shown in Figure 2(a), the first sheet material 100 is formed by molding a single thermoplastic resin core sheet (not shown) into a predetermined shape. The first sheet material 100 has strip-shaped planar regions 110 and bulging regions 120 arranged alternately in the longitudinal direction (X direction) of the first sheet material 100. In the bulging region 120, a first bulge portion 121, which has a downward groove-like cross-section consisting of an upper surface and a pair of side surfaces, is formed over the entire length of the bulging region 120 in the direction in which it extends (Y direction). Preferably, the angle between the upper surface and the side surface of the first bulge portion 121 is 90 degrees, and as a result, the cross-sectional shape of the first bulge portion 121 is a downward U-shape. Furthermore, the width of the first bulge portion 121 (length in the short direction of the upper surface) is set to be equal to the width of the planar region 110 and twice the bulge height of the first bulge portion 121 (length in the short direction of the side surface).

[0027] Furthermore, the bulging region 120 has multiple second bulges 122, each having a trapezoidal cross-section obtained by bisecting a regular hexagon with its longest diagonal, formed perpendicular to the first bulge 121. The bulge height of the second bulges 122 is set to be equal to the bulge height of the first bulge 121. The spacing between adjacent second bulges 122 is equal to the width of the upper surface of the second bulge 122.

[0028] The first bulge 121 and the second bulge 122 are formed by utilizing the plasticity of the sheet to partially bulge the sheet upward. Furthermore, the first sheet material 100 can be formed from a single core sheet by well-known molding methods such as vacuum forming or compression molding.

[0029] As shown in Figures 2(a) and 2(b), the core layer 40 is formed by folding the first sheet material 100, configured as described above, along boundary lines P and Q. Specifically, the first sheet material 100 is valley-folded at boundary line P between the planar region 110 and the bulging region 120, and mountain-folded at boundary line Q between the upper surface and side surface of the first bulging portion 121, thereby compressing it in the X direction. Then, as shown in Figures 2(b) and 2(c), the upper surface and side surface of the first bulging portion 121 overlap, and the end surface of the second bulging portion 122 overlaps with the planar region 110. This forms a prismatic compartment 130 extending in the Y direction for each bulging region 120. As these compartments 130 are continuously formed in the X direction, a hollow plate-like core layer 40 is formed.

[0030] As described above, when the first sheet material 100 is compressed, the upper wall portion 41 of the core layer 40 is formed by the upper surface and side surface of the first bulge portion 121, and the lower wall portion 42 of the core layer 40 is formed by the end surface and planar region 110 of the second bulge portion 122. As shown in Figure 2(c), the portion of the upper wall portion 41 where the upper surface and side surface of the first bulge portion 121 overlap to form a two-layer structure, and the portion of the lower wall portion 42 where the end surface and planar region 110 overlap to form a two-layer structure, each become an overlapping portion 131.

[0031] Furthermore, the hexagonal prism-shaped region formed by the folding of the second bulge 122 becomes the second cell S2, and the hexagonal prism-shaped region formed between a pair of adjacent partitions 130 becomes the first cell S1. In this embodiment, the upper surface and side surface of the second bulge 122 constitute the side wall portion 43 of the second cell S2, and the side surface of the second bulge 122 and the planar portion located between the second bulges 122 in the bulging region 120 constitute the side wall portion 43 of the first cell S1. The contact portions of the upper surfaces of the second bulges 122 and the contact portions of the planar portions in the bulging region 120 form a two-layer side wall portion 43. It is preferable to heat-treat the first sheet material 100 to soften it before carrying out this folding process.

[0032] Thermoplastic resin sheets are then joined to both sides of the core layer 40 obtained in this manner by heat welding. The thermoplastic resin sheets joined to both sides of the core layer 40 each become a skin layer 50.

[0033] When the skin layer 50 is heat-welded to the core layer 40, the upper wall portion 41 (overlapping portion 131) of the two-layer structure in the first cell S1 is heat-welded to each other. Similarly, the lower wall portion 42 (overlapping portion 131) of the two-layer structure in the second cell S2 is heat-welded to each other. On the other hand, the side wall portions 43 of the two-layer structure in the first cell S1 and the second cell S2 conduct heat less easily than the upper wall portion 41 and the lower wall portion 42. Therefore, the side wall portions 43 of the two-layer structure have portions in the center of the thickness direction of the hollow structure 20 that are not joined to each other by heat welding. As a result, the internal space of each cell S is not a completely closed space, but rather the internal spaces of each cell S communicate with each other through the gaps between the side wall portions 43 of the two-layer structure that are not joined to each other by heat welding.

[0034] Then, by bonding aluminum sheets 30 to the surface of each skin layer 50 with an adhesive, a laminated structure 10 is formed. This laminated structure 10 can be used, for example, as a floor panel for an automobile after being cut into a predetermined shape.

[0035] According to this embodiment, the following effects can be obtained. (1) The laminated structure 10 includes a hollow structure 20 having a core layer 40 and an aluminum sheet 30 joined to the hollow structure 20. The core layer 40 is formed by molding a core sheet of a thermoplastic resin. The elastic modulus of the core sheet is 1000 MPa or more, and the ratio of the elastic modulus of the aluminum sheet 30 to the elastic modulus of the core sheet is 20 or more and 80 or less. Therefore, for the laminated structure 10, the decrease in bending rigidity due to the influence of shear can be reduced, and high bending rigidity can be maintained.

[0036] (2) The thickness of the core sheet is 0.16 mm or more, and the thickness of the aluminum sheet 30 is 0.11 mm or more. Therefore, for the laminated structure 10, the decrease in bending rigidity due to the influence of shear can be further reduced, and high bending rigidity can be maintained.

[0037] (3) The ratio of the thickness of the aluminum sheet 30 to the thickness of the core sheet is 0.4 or more and 3.0 or less. Therefore, for the laminated structure 10, the decrease in bending rigidity due to the influence of shear can be reduced, and the amount of deflection can be suppressed to be small.

[0038] (4) The diagonal angle θ of the cell S is 45 degrees or more and 75 degrees or less. Therefore, for the laminated structure 10, the decrease in bending rigidity due to the influence of shear can be further reduced, and high bending rigidity can be maintained.

[0039] (5) The cavity volume of the cell S is 400 mm 3 or more and 3000 mm 3 or less. Therefore, for the laminated structure 10, the decrease in bending rigidity due to the influence of shear can be further reduced, and high bending rigidity can be maintained.

[0040] Note that the above embodiment may be modified as follows. · In the hollow structure 20 of the above embodiment, the skin layers 50 are joined to both sides of the core layer 40, but the skin layer 50 on one side or both sides may be omitted.

[0041] In the laminated structure 10 of the above embodiment, aluminum sheets 30 were bonded to both sides of the hollow structure 20, but the aluminum sheet 30 on one side may be omitted. The surface of the aluminum sheet 30 may be covered with a thermoplastic resin. This allows the thermoplastic resin to function as a protective sheet for the aluminum sheet 30, preventing damage to the aluminum sheet 30.

[0042] The applications of the laminated structure 10 are not particularly limited. Next, a specific example of the laminated structure 10 is shown below. Example 1 (Test of the relationship between the elastic modulus of the core sheet and the bending stiffness of the laminated structure 10) Core layers 40 were manufactured using core sheets with different moduli. The moduli (MPa) of the core sheets were 500, 750, 1000, 1200, 1800, 2300, 2800, 3300, and 3800 (9 types). A hollow structure 20 was formed by heat-welding a PP sheet with a sheet thickness of 0.3 mm and an moduli of 1200 MPa to both sides of the core layer 40 as a skin layer 50. An aluminum sheet 30 with an moduli of 68600 MPa was bonded to both sides of the hollow structure 20 with adhesive to form a laminated structure 10. The moduli of the core sheet and the bending stiffness (Nm) of the laminated structure 10 were determined. 2 The relationship between the two was simulated. Bending stiffness was calculated as bending stiffness excluding shear (○) and bending stiffness including shear (◇). This is the same for the following examples. The results are shown in Figure 3. As shown in Figure 3, the bending stiffness including shear (◇) of the laminated structure 10 decreases significantly when the elastic modulus of the core sheet is less than 1000 MPa, compared to the bending stiffness excluding shear (○).

[0043] The bending stiffness (EIx) of the laminated structure 10, excluding shear, can be calculated using the formula shown in Figure 4. In Figure 4, "cell thickness t1" is the thickness of one layer of the side wall portion 43 of the cell S, as shown in the schematic diagram of the same figure. The calculation formula shown in Figure 12 is similar. Furthermore, the bending stiffness (EIy) including shear can be calculated using the formula shown in Figure 5. In this formula for calculating "bending stiffness (EIy) including shear" shown in Figure 5, "bending deformation amount (δ)" can be calculated using the formula shown in Figure 6, and "shear deformation amount (ε)" can be calculated using the formula shown in Figure 11.

[0044] Example 2 (Test of the relationship between the ratio of the elastic modulus of the core sheet and the elastic modulus of the aluminum sheet 30 and the bending stiffness of the laminated structure 10) Core layers 40 were manufactured using core sheets with different moduli (the same nine types as in Example 1). A hollow structure 20 was created by heat-welding a PP sheet with a sheet thickness of 0.3 mm and an elastic modulus of 1200 MPa as a skin layer 50 to both sides of the core layer 40. An aluminum sheet 30 with an elastic modulus of 68600 MPa was laminated to both sides of the hollow structure 20 using adhesive to create a laminated structure 10. The relationship between the ratio of the elastic modulus of the aluminum sheet 30 to the elastic modulus of the core sheet (elastic modulus of one aluminum sheet 30 / elastic modulus of the core sheet) and the bending stiffness of the laminated structure 10 was simulated. The results are shown in Figure 7. As shown in Figure 7, the bending stiffness of the laminated structure 10, both excluding shear (○) and including shear (◇), remains high even when the ratio of elastic moduli falls below 20. Furthermore, when the ratio of elastic moduli exceeds 80, the bending stiffness of the laminated structure 10, excluding shear (○), does not decrease significantly, while the bending stiffness including shear (◇) decreases sharply.

[0045] Example 3 (Test of the relationship between core sheet thickness and bending stiffness of laminated structure 10) Core layers 40 were manufactured using core sheets of different thicknesses. The core sheet thicknesses (mm) were 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, and 0.50 (9 types). A hollow structure 20 was created by heat-welding a PP sheet with a sheet thickness of 0.3 mm and an elastic modulus of 1200 MPa as a skin layer 50 to both sides of the core layer 40. A laminated structure 10 was created by adhesively bonding an aluminum sheet 30 with a thickness of 0.25 mm to both sides of the hollow structure 20. The relationship between the core sheet thickness and the bending stiffness of the laminated structure 10 was simulated. The results are shown in Figure 8. As shown in Figure 8, the bending stiffness including shear (◇) decreases significantly when the core sheet thickness is less than 0.16 mm, compared to the bending stiffness excluding shear (○).

[0046] Example 4 (Test of the relationship between the thickness of the aluminum sheet 30 and the bending stiffness of the laminated structure 10) A core layer 40 was manufactured using a core sheet with a thickness of 0.30 mm. A hollow structure 20 was created by heat-welding a PP sheet with a thickness of 0.3 mm and an elastic modulus of 1200 MPa to both sides of the core layer 40 as a skin layer 50. Aluminum sheets 30 of different thicknesses were bonded to both sides of the hollow structure 20 with adhesive to form laminated structures 10. The thicknesses (mm) of the aluminum sheets 30 were 0.10, 0.14, 0.25, 0.50, 0.75, 1.00, and 1.10 (seven types). Aluminum sheets 30 of the same thickness were bonded to both sides of the hollow structure 20. The relationship between the thickness (mm) of the aluminum sheets 30 and the bending stiffness of the laminated structure 10 was simulated. The results are shown in Figure 9. As shown in Figure 9, both the bending stiffness excluding shear (○) and the bending stiffness including shear (◇) show that when the thickness of the aluminum sheet 30 is 0.11 mm or less, the bending stiffness of the laminated structure 10 decreases, and it becomes more susceptible to tearing under localized loads, etc. Furthermore, when the aluminum sheet 30 is thicker than 0.9 mm, the discrepancy between the values ​​of the bending stiffness excluding shear (○) and the bending stiffness including shear (◇) becomes large.

[0047] Example 5 (Test of the relationship between the ratio of the thickness of the aluminum sheet 30 to the thickness of the core sheet and the amount of deflection of the laminated structure 10) Core layers 40 were manufactured using core sheets of different thicknesses (three types with thicknesses (mm) of 0.20, 0.30, and 0.40). Hollow structures 20 were formed by heat-welding PP sheets with a sheet thickness of 0.3 mm and an elastic modulus of 1200 MPa to both sides of the core layers 40 as skin layers 50. Aluminum sheets 30 of different thicknesses (same as in Example 4) were bonded to both sides of the hollow structures 20 with adhesive to form a laminated structure 10. In this case, aluminum sheets 30 of the same thickness were bonded to both sides of the hollow structures 20. For this laminated structure 10, the relationship between the ratio of the thickness of the aluminum sheets 30 to the thickness of the core sheets (thickness of one aluminum sheet 30 / thickness of the core sheet) and the amount of deflection (mm) of the laminated structure 10 was simulated. The results are shown in Figure 10. As shown in Figure 10, for core sheet thicknesses (mm) of 0.20 (○), 0.30 (◇), and 0.40 (△), the amount of deflection increases when the thickness ratio is less than 0.4. Also, when the thickness ratio exceeds 3.0, the change in the amount of deflection decreases.

[0048] The "deflection (mm)" of the laminated structure 10 can be calculated as the sum of the "bending deformation (δ)" shown in Figure 6 and the "shear deformation (ε)" shown in Figure 11. Furthermore, the "core shear modulus (G)" in the equation shown in Figure 11 can be calculated using the equation shown in Figure 12. In the equation in Figure 12, the unit of the angle θ between cells S is radians.

[0049] Example 6 (Test of the relationship between the angle θ of cell S and the bending stiffness of the laminated structure 10) Core layers 40 with different cell angles θ (degrees) were manufactured, and a hollow structure 20 was formed by heat-welding a PP sheet with a sheet thickness of 0.3 mm and an elastic modulus of 1200 MPa as a skin layer 50 to both sides of the core layer 40. The cell angles θ (degrees) were 40.28, 48.78, 60.24, 65.77, 71.82, 75.02, 78.32, and 81.69 (eight types). A laminated structure 10 was formed by bonding a 0.25 mm thick aluminum sheet 30 to both sides of the hollow structure 20 with adhesive. The relationship between the cell angle θ and the bending stiffness of the laminated structure 10 was simulated for this laminated structure 10. The results are shown in Figure 13. As shown in Figure 13, the bending stiffness including shear (◇) decreases when the cell angle θ is less than 45 degrees compared to the bending stiffness excluding shear (○), but does not change significantly above 75 degrees.

[0050] Example 7 (Test of the relationship between the cavity volume of cell S and the bending stiffness of the laminated structure 10) The void volume of cell S (mm 3 Core layers 40 with different properties were manufactured, and PP sheets with a sheet thickness of 0.3 mm and an elastic modulus of 1200 MPa were heat-sealed to both sides of the core layer 40 as skin layers 50 to form a hollow structure 20. The cavity volume of cell S (mm 3 The eight types are 133, 236, 369, 531, 944, 1476, 3320, and 5903. A laminated structure 10 was formed by bonding 0.25 mm thick aluminum sheets 30 to both sides of a hollow structure 20 with adhesive. The relationship between the void volume of cell S and the bending stiffness of the laminated structure 10 was simulated for this laminated structure 10. The results are shown in Figure 14. As shown in Figure 14, the bending stiffness including shear (◇) is compared to the bending stiffness excluding shear (○) when the void volume of cell S is 400 mm 3 Below this value, there is no significant change. On the other hand, when the void volume of cell S is 3000 mm 3 Beyond a certain point, the bending stiffness including shear (◇) decreases compared to the bending stiffness excluding shear (○).

[0051] Next, the technical concepts that can be understood from the above embodiments and alternative examples, along with their effects, will be added below. (a) A laminated structure in which the surface of an aluminum sheet is coated with a thermoplastic resin. This provides protection for the aluminum sheet. [Explanation of symbols]

[0052] 10…Laminated structure 20...Hollow structure 30…Aluminum sheet 40... Core Layer 50...Skin layer S...Cell θ...the opposite angle between cells.

Claims

1. A laminated structure comprising a hollow structure having a core layer in which multiple cells are arranged in parallel inside, and an aluminum sheet joined to the hollow structure, The aforementioned core layer is formed by molding a core sheet of thermoplastic resin. The elastic modulus of the core sheet is 1000 MPa or more. A laminated structure characterized in that the ratio of the elastic modulus of the aluminum sheet to the elastic modulus of the core sheet is 20 or more and 80 or less.

2. The thickness of the core sheet is 0.16 mm or more, and the thickness of the aluminum sheet is 0.11 mm or more. The laminated structure according to claim 1, characterized in that the ratio of the thickness of the aluminum sheet to the thickness of the core sheet is 0.4 or more and 3.0 or less.

3. The laminated structure according to claim 1, characterized in that the diagonal angle between the cells is 45 degrees or more and 75 degrees or less.

4. The cavity volume of the aforementioned cell is 400 mm ３ 3000mm or more ３ The laminated structure according to any one of claims 1 to 3, characterized in that it is as follows:

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