Bonding method and bonded structure

Abstract

A bonded structure (200) comprises: a first member (210) containing a thermoplastic first resin; a second member (220) containing a thermoplastic second resin; and a metal member (230) having a first surface (232) on which a first metal oxide particle cluster 236 to be bonded to the first resin of the first member (210) is formed and a second surface (234) on which a second metal oxide particle cluster (238) to be bonded to the second resin of the second member (220) is formed, wherein the thickness from the first surface (232) to the second surface (234) is 5 μm to 1 mm.

Description

Joining method and joined structure

[0001] The present invention relates to a joining method and a joined structure.

[0002] In recent years, structural components made of fiber-reinforced plastics have been increasingly adopted to reduce the weight of automobiles, aircraft, and other vehicles. For example, fiber-reinforced plastics (FRP) materials are formed by hot-pressing prepregs in which reinforcing fibers are impregnated with resin. FRP materials are bonded to metal materials, for example, with epoxy adhesives (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-140091

[0004] In the above-mentioned prior art, there is a concern that bonding with an epoxy adhesive may result in a decrease in strength.

[0005] The present invention has been made in view of the above problems, and one of its exemplary objects is to provide a joined structure that is lightweight and has excellent rigidity.

[0006] A bonding method according to one embodiment of the present invention includes the steps of: placing a metal member having a first surface on which first metal oxide particle clusters are formed and a second surface on which second metal oxide particle clusters are formed, the metal member having a thickness of 1 mm or less from the first surface to the second surface, between a first member containing a first thermoplastic resin and a second member containing a second thermoplastic resin; and heating and pressurizing the metal member between the first member and the second member to bond the first surface to the first resin and the second surface to the second resin.

[0007] Another aspect of the present invention is a bonded structure comprising: a first member containing a first thermoplastic resin; a second member containing a second thermoplastic resin; and a metal member having a first surface on which first metal oxide particle clusters bonded to the first resin of the first member are formed; and a second surface on which second metal oxide particle clusters bonded to the second resin of the second member are formed, the metal member having a thickness from the first surface to the second surface being 5 μm or more and 1 mm or less.

[0008] According to one aspect of the present invention, a lightweight joined structure with excellent rigidity can be provided.

[0009] 1A and 1B are cross-sectional views schematically showing the configuration of a joined structure according to the first embodiment. FIGS. 2A to 2C are views schematically showing a joining method according to the first embodiment. FIG. 2B is a perspective view schematically showing the configuration of a joined structure according to the second embodiment. FIG. 2C is a perspective view schematically showing the configuration of a reinforcing member according to the second embodiment. FIG. 2D is a perspective view schematically showing the configuration of a reinforcing member according to the second embodiment. FIG. 2E is a top view schematically showing the configuration of a reinforcing member according to the second embodiment. FIG. 2F is a side cross-sectional view schematically showing the configuration of a reinforcing member according to the second embodiment. FIG. 2G is a top view schematically showing the lattice frame shape of the top portion. FIGS. 9A and 9B are views schematically showing a method of forming a prepreg sheet. FIGS. 9A and 9B are views schematically showing a method of molding a reinforcing member according to the second embodiment. FIGS. 11A and 11B are views schematically showing the orientation direction of a prepreg sheet. FIG. 11G is a top view of a reinforcing member according to an example. FIG. 11H is a view schematically showing a joint between a main body member and a reinforcing member. FIG. 11I is a top view of a metal member according to the second embodiment. FIG. 11I is a perspective view schematically showing the configuration of a reinforcing member according to a modified example. FIG. 11I is a perspective view schematically showing the configuration of a reinforcing member according to a modified example. 10A and 10B are diagrams illustrating a method for forming a reinforcing member according to a modified example;

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted as appropriate. To facilitate understanding of the description, the dimensional ratios of the components in each drawing do not necessarily correspond to the actual dimensional ratios.

[0011] 1 is a cross-sectional view that schematically illustrates the configuration of a joined structure 200 according to a first embodiment. The joined structure 200 includes a first member 210, a second member 220, and a metal member 230. The joined structure 200 is a structure in which the first member 210 and the second member 220 are joined by the metal member 230, and the metal member 230 functions as an adhesive or joining material.

[0012] The first member 210 includes a first thermoplastic resin. The first member 210 is a resin material entirely composed of the first resin, or a fiber-reinforced resin material including first reinforcing fibers impregnated with the first resin. The second member 220 includes a second thermoplastic resin. The second member 220 is a resin material entirely composed of the second resin, or a fiber-reinforced resin material including second reinforcing fibers impregnated with the second resin. The first resin and the second resin may be the same resin material or different resin materials. Similarly, the first reinforcing fibers and the second reinforcing fibers may be the same reinforcing fiber material or different reinforcing fiber materials. At least one of the first reinforcing fibers and the second reinforcing fibers may be arranged to extend in a direction along the first surface 232 or the second surface 234 of the metal member 230. At least one of the first reinforcing fibers and the second reinforcing fibers may be braided.

[0013] At least one of the first resin and the second resin is a thermoplastic engineering plastic, such as aromatic polyetherketone (PAEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyphenylene sulfide (PPS), polyetherimide (PEI), or polyethersulfone (PES). At least one of the first reinforcing fiber and the second reinforcing fiber is carbon fiber, glass fiber, or aramid fiber.

[0014] The metal member 230 has a first surface 232 that joins with the first member 210 and a second surface 234 that joins with the second member 220. The thickness of the metal member 230 from the first surface 232 to the second surface 234 is 5 μm or more and 2 mm or less, for example, 10 μm or more and 1 mm or less, for example, 50 μm or more and 0.5 mm or less. The metal member 230 can be made of, for example, steel, aluminum, aluminum alloy, titanium, titanium alloy, nickel-titanium alloy, copper, or copper alloy.

[0015] First metal oxide particle clusters 236 for bonding with the first resin are formed on the first surface 232. Second metal oxide particle clusters 238 for bonding with the second resin are formed on the second surface 234. At least one of the first metal oxide particle clusters 236 and the second metal oxide particle clusters 238 can be formed by heating and modifying the surface of the metal member 230 using laser irradiation or the like. The metal oxide particle clusters are, for example, composed of an oxide of the metal material that constitutes the metal member 230 before heating. The metal oxide particle clusters are, for example, formed by locally melting a metal material, with particulate metal oxide adhered to the surface. The particle diameter of the metal oxide particle clusters is, for example, 5 nm to 500 nm, for example, 50 nm to 200 nm. The maximum height of the metal oxide particle clusters is, for example, 50 nm to 3 μm, for example, 100 nm to 2 μm, for example, 200 nm to 1 μm.

[0016] The first metal oxide particle clusters 236 chemically bond to the first resin contained in the first member 210 and physically bond to the first resin by the softened first resin penetrating the unevenness of the particle clusters. By providing the first metal oxide particle clusters 236, the bonding strength between the first member 210 and the metal member 230 can be improved. Similarly, the second metal oxide particle clusters 238 chemically bond to the second resin contained in the second member 220 and physically bond to the second resin by the softened second resin penetrating the unevenness of the particle clusters. By providing the second metal oxide particle clusters 238, the bonding strength between the second member 220 and the metal member 230 can be improved. By bonding the first member 210 and the second member 220 via the metal oxide particle clusters, the bonding strength can be dramatically improved compared to bonding directly by fusing the first resin and the second resin or bonding via an epoxy adhesive.

[0017] 2(a) to 2(c) are diagrams schematically illustrating the bonding method according to the first embodiment. First, as shown in FIG. 2(a), a metal member 230 is disposed between a first member 210 and a second member 220. The metal member 230 includes a bonding portion 240, a first extending portion 242, and a second extending portion 244. The bonding portion 240 is a portion located between the first member 210 and the second member 220. A first metal oxide particle cluster 236 and a second metal oxide particle cluster 238 are formed on both sides of the bonding portion 240.

[0018] The first extending portion 242 and the second extending portion 244 are portions that extend and protrude from between the first member 210 and the second member 220. The first extending portion 242 is, for example, a portion that extends along the first member 210. The second extending portion 244 is, for example, a portion that extends along the second member 220. The first metal oxide particle clusters 236 and the second metal oxide particle clusters 238 do not have to be formed on both surfaces of the first extending portion 242 and the second extending portion 244. In the example shown in FIG. 2( a), a joint portion 240 is provided between the first extending portion 242 and the second extending portion 244. Note that the metal member 230 may include only one of the first extending portion 242 and the second extending portion 244, and not the other. The metal member 230 may include only the joint portion 240, without including the first extending portion 242 and the second extending portion 244.

[0019] Next, as shown in FIG. 2B , the joint portion 240 of the metal member 230 is pressurized between the first member 210 and the second member 220 as indicated by arrow F. The metal member 230 is heated while being pressurized. The metal member 230 can be heated by irradiating it with electromagnetic waves or passing an electric current through it. For example, at least one of the first extension portion 242 and the second extension portion 244 may be irradiated with electromagnetic waves such as laser light or infrared light. For example, a power source may be connected to the first extension portion 242 and the second extension portion 244, and an electric current may be passed through the metal member 230 to perform resistance heating. Alternatively, the metal member 230 may be heated by high-frequency induction heating, in which a high-frequency magnetic field is applied by arranging a coil around at least one of the first extension portion 242 and the second extension portion 244 to generate an eddy current in the metal member 230. By applying pressure to the metal member 230 while heating it, the first resin of the first member 210 softens and bonds to the first metal oxide particle clusters 236, and the second resin of the second member 220 softens and bonds to the second metal oxide particle clusters 238.

[0020] Next, as shown in FIG. 2( c), the first extending portion 242 and the second extending portion 244 are cut off and removed from the joint portion 240 joined between the first member 210 and the second member 220. The first extending portion 242 and the second extending portion 244 are non-joint portions that are not joined to the first member 210 or the second member 220 and do not contribute to the joining. This completes the joined structure 200 shown in FIG. 1. Note that the first extending portion 242 and the second extending portion 244 do not have to be removed, and at least one of the first extending portion 242 and the second extending portion 244 may remain connected to the joint portion 240.

[0021] The metal member 230 may be preheated before being placed between the first member 210 and the second member 220 .

[0022] According to this embodiment, the bonding strength between the first member 210 and the second member 220 can be improved. Furthermore, by setting the thickness of the metal member 230 to 2 mm or less, preferably 1 mm or less, the weight increase due to the addition of the metal member 230 can be suppressed. Furthermore, by reducing the thickness of the metal member 230, the film-like metal member 230 can be easily fitted to the surface of the first member 210 or the second member 220, even if the surface of the first member 210 or the second member 220 is curved. Furthermore, when the first member 210 or the second member 220 contains woven reinforcing fibers, the film-like metal member 230 can be easily positioned along minute irregularities caused by the weave of the reinforcing fibers. This can enhance the adhesion between the first member 210 or the second member 220, which is a fiber-reinforced resin, and the metal member 230, thereby improving the bonding strength.

[0023] Second Embodiment Fig. 3 is a perspective view that schematically shows the configuration of a joined structure 10 according to a second embodiment. The joined structure 10 is a blocker door that is attached to the outer periphery of an aircraft engine. The blocker door is a movable member that blocks the bypass airflow of the engine and causes reverse thrust. In the embodiment, a blocker door is used as an example of the joined structure 10, but the use of the joined structure 10 according to this embodiment is not particularly limited. The joined structure 10 according to this embodiment can be applied to structural members of any shape and for any purpose.

[0024] The joined structure 10 includes a main body member 12 and a reinforcing member 14. The main body member 12 is a plate-like member and has a surface 12a against which the bypass airflow collides during reverse thrust, and a back surface 12b opposite the surface 12a. The main body member 12 has a gently curved shape overall. Because the main body member 12 is a thin plate-like member, it is prone to deformation (e.g., bending) due to a load applied to the surface 12a. The reinforcing member 14 is attached to the back surface 12b of the main body member 12 and suppresses deformation (e.g., bending) of the surface 12a of the main body member 12, thereby increasing the rigidity of the main body member 12. The reinforcing member 14 is a plate-like member with irregularities formed thereon, and the irregular shape suppresses deformation (e.g., bending).

[0025] Conventionally, sandwich panels with honeycomb cores have been used as lightweight, highly rigid structural members. However, the honeycomb core material itself is expensive, and it is difficult to process it into any desired shape, resulting in high processing costs. In this embodiment, the main body member 12 and the reinforcing member 14 are made of fiber-reinforced plastics (FRP), and the reinforcing member 14 is joined to the main body member 12, thereby achieving a lightweight, highly rigid joined structure 10 without using a honeycomb core. The main body member 12 and the reinforcing member 14 are joined, for example, by a metal member (not shown in FIG. 3 ) having metal oxide particle clusters formed on its surface, as in the first embodiment.

[0026] 4 to 7 are diagrams schematically illustrating the configuration of a reinforcing member 14 according to a second embodiment. The reinforcing member 14 is made of a plate-shaped member 16 having an uneven surface formed thereon. The plate-shaped member 16 has a first surface 16a and a second surface 16b opposite the first surface 16a. FIG. 4 is a perspective view of the first surface 16a, and FIG. 5 is a perspective view of the second surface 16b. FIG. 6 is a top view of the first surface 16a. FIG. 7 is a cross-sectional side view corresponding to the cross section taken along line V-V in FIG. 6.

[0027] In the drawings, the thickness direction of the reinforcing member 14 is the z direction, the longitudinal direction of the reinforcing member 14 is the x direction, and the direction perpendicular to the x direction and the z direction is the y direction. These directions are set to facilitate understanding of the embodiment and do not in any way limit the directions during manufacture or use of the joined structure 10 or the reinforcing member 14. In addition, in the drawings, inflection portions of the concave-convex shape are also indicated by solid lines to clearly show the concave-convex shape.

[0028] The shape of the outer edge 18 of the plate-shaped member 16 is, for example, a square, such as a rectangle. The outer edge 18 of the plate-shaped member 16 has long sides 18a extending in the longitudinal direction (e.g., the x direction), short sides 18b extending in a direction intersecting the longitudinal direction (e.g., the y direction), and corners 18c provided between the long sides 18a and the short sides 18b. The shape of the outer edge 18 of the plate-shaped member 16 is not particularly limited and may be a trapezoid, rhombus, parallelogram, or any polygonal shape such as a triangle, pentagon, or hexagon. The corners 18c of the plate-shaped member 16 may be rounded. The corners 18c may be rounded in a linear manner or in an arcuate manner.

[0029] The plate-like member 16 is configured to have a uniform thickness t (see FIG. 7) as a whole. The thickness t of the plate-like member 16 is not particularly limited, but is, for example, 0.5 mm to 10 mm, and preferably 1 mm to 5 mm.

[0030] The plate-like member 16 has an outer periphery 20 , a protrusion 22 , and a plurality of recesses 24 .

[0031] The outer peripheral portion 20 is a portion that defines the outer edge 18 of the plate-like member 16. The outer peripheral portion 20 has a frame shape or a closed loop shape that follows the outer edge 18 of the plate-like member 16. The outer peripheral portion 20 is a portion that changes shape less in the thickness direction than the convex portions 22 and the multiple concave portions 24. The outer peripheral portion 20 is a portion that is joined to the back surface 12b of the main body member 12, and has a shape that follows the back surface 12b of the main body member 12. If the back surface 12b of the main body member 12 has a gently curved shape, the outer peripheral portion 20 as a whole has a gently curved shape. If the back surface 12b of the main body member 12 is flat, the outer peripheral portion 20 has a flat shape as a whole.

[0032] The protrusions 22 are formed inside the outer peripheral portion 20. The protrusions 22 are formed in a region inside the region where the outer peripheral portion 20 is formed in a plan view of the first surface 16a (see FIG. 6). The protrusions 22 are portions that protrude in the thickness direction relative to the outer peripheral portion 20. The protrusions 22 protrude toward the first surface 16a, and are formed so that the first surface 16a is convex and the second surface 16b is concave. The protrusions 22 are formed, for example, so as to occupy most of the plate-like member 16. The area S1 enclosed by the outer edge 26 of the protrusions 22 is 50% or more of the area S enclosed by the outer edge 18 of the plate-like member 16, and preferably 70% or more or 80% or more.

[0033] The outer edge 26 of the protrusion 22 has a first section 26a extending in the longitudinal direction (e.g., the x direction) along the long side 18a, a second section 26b extending in a direction intersecting the longitudinal direction (e.g., the y direction) along the short side 18b, and a third section 26c extending in an arc shape between the first section 26a and the second section 26b. The radius of curvature of the third section 26c is larger than the radius of curvature of the corners 18c of the plate-like member 16. In the illustrated example, the outer edge 26 of the protrusion 22 has a quadrilateral shape with the four corners formed in an arc shape.

[0034] The apex 28 of the convex portion 22 is configured so that its height h1 (see FIG. 7 ) in the thickness direction from the outer periphery 20 is constant. When the outer periphery 20 is flat, the apex 28 is also configured so that it is flat. When the outer periphery 20 is gently curved, the apex 28 is also configured so that it is gently curved. The height h1 in the thickness direction from the outer periphery 20 to the apex 28 is preferably 50 mm or less, and more preferably 30 mm or less. The height h1 in the thickness direction from the outer periphery 20 to the apex 28 is preferably greater than the thickness t of the plate-like member 16, and is, for example, 5 mm or more, for example, 10 mm or more.

[0035] An outer inclined portion 30 (see FIG. 7 ) is provided between the outer peripheral portion 20 and the apex 28. The outer inclined portion 30 is formed so that its height monotonically increases from the outer peripheral portion 20 to the apex 28. The outer inclined portion 30 is preferably formed so that the slope does not change abruptly from the outer peripheral portion 20 to the apex 28, and is formed only by a smoothly curved surface. The outer inclined portion 30 is configured by a smooth curve with a radius of curvature of, for example, 20 mm or more or 30 mm or more in a cross-sectional view perpendicular to the outer edge 18 of the plate-like member 16.

[0036] The plurality of recesses 24 are formed inside the protrusion 22. The plurality of recesses 24 are formed in a region more inward than the outer edge 26 of the protrusion 22 in a plan view of the first surface 16a (see FIG. 6). The plurality of recesses 24 are formed, for example, in a region more inward than the outer edge of the apex 28 in a plan view of the first surface 16a (see FIG. 6). The plurality of recesses 24 are formed to be recessed in the thickness direction relative to the apex 28. The plurality of recesses 24 protrude toward the second surface 16b, and are formed so that the first surface 16a is recessed and the second surface 16b is convex. The plurality of recesses 24 are arranged in a lattice pattern on the apex 28. The plurality of recesses 24 are arranged in the longitudinal direction (e.g., x direction) of the plate-like member 16 and in a direction intersecting the longitudinal direction (e.g., y direction). The plurality of recesses 24 may be arranged radially on the apex 28.

[0037] The outer edge 32 (see FIG. 6 ) of each of the plurality of recesses 24 includes a first section 32a extending in the longitudinal direction (e.g., the x direction) along the long side 18a, a second section 32b extending in a direction intersecting the longitudinal direction (e.g., the y direction) along the short side 18b, and a third section 32c extending in an arc shape between the first section 32a and the second section 32b. The radius of curvature of the third section 32c is larger than the radius of curvature of the corners 18c of the plate-like member 16. In the illustrated example, the outer edge 32 of each of the recesses 24 has a quadrilateral shape with four arc-shaped corners. The size of each of the outer edges 32 of the plurality of recesses 24 in the longitudinal direction (e.g., the x direction) and in a direction intersecting the longitudinal direction (e.g., the y direction) are approximately the same. That is, the length of the first section 32a is approximately the same as the length of the second section 32b, for example, approximately 0.8 to 1.2 times the length of the second section 32b.

[0038] The bottoms 34 of the recesses 24 are joined to the rear surface 12b of the main body member 12. The bottoms 34 are configured so that the depth h2 (see FIG. 7) in the thickness direction from the top 28 is constant. When the outer periphery 20 is flat, the bottoms 34 of the recesses 24 are configured to be located on an imaginary plane B (see FIG. 7) defined by the outer periphery 20. When the outer periphery 20 is gently curved, the bottoms 34 of the recesses 24 are configured to be located on a curved surface defined by the outer periphery 20. The height h2 in the thickness direction from the top 28 to the bottom 34 is preferably 50 mm or less, and more preferably 30 mm or less. The height h2 in the thickness direction from the top 28 to the bottom 34 is, for example, 5 mm or more, for example, 10 mm or more.

[0039] The bottom 34 of each of the plurality of recesses 24 has a rectangular shape or a rectangular shape with rounded corners. By making the bottom 34 a rectangular shape or a shape similar to a rectangular shape, the area occupied by the bottom 34 can be increased compared to when the bottom 34 is a circular shape. This increases the bonding area between the main body member 12 and the top 28, and increases the bonding strength between the main body member 12 and the reinforcing member 14.

[0040] An inner inclined portion 36 (see FIG. 7 ) is provided between the top portion 28 and the bottom portion 34. The inner inclined portion 36 is formed so that its height monotonically increases from the bottom portion 34 to the top portion 28. The inner inclined portion 36 is preferably formed so that the slope does not change abruptly from the bottom portion 34 to the top portion 28, and is formed only by a smoothly curved surface. The inner inclined portion 36 is configured by a smooth curve with a radius of curvature of, for example, 20 mm or more or 30 mm or more in a cross-sectional view perpendicular to the outer edge 18 of the plate-like member 16.

[0041] The top portion 28 has a lattice frame shape surrounding the outer edges 32 of the recesses 24 due to the multiple recesses 24 being arranged in a lattice pattern. FIG. 8 is a top view schematically illustrating the lattice frame shape of the top portion 28, with the lattice frame shape of the top portion 28 being schematically illustrated by thick lines. The top portion 28 includes multiple first beams 38a, 38b extending in the longitudinal direction (e.g., the x direction), multiple second beams 40a, 40b extending in a direction intersecting the longitudinal direction (e.g., the y direction), and multiple arc-shaped corners 42. The multiple first beams 38a, 38b include outer first beams 38a located outside the multiple recesses 24 and inner first beams 38b located between the multiple recesses 24. The multiple second beams 40a, 40b include outer second beams 40a located outside the multiple recesses 24 and inner second beams 40b located between the multiple recesses 24. The first outer beam 38a and the second outer beam 40a are connected by corners 42 extending in an arc shape. Both ends of the first inner beam 38b are connected to the second outer beam 40a. Both ends of the second inner beam 40b are connected to the first outer beam 38a. The top 28 has a lattice frame shape formed by the first beams 38a, 38b, the second beams 40a, 40b, and the corners 42, and is therefore able to accommodate load changes in both the longitudinal direction (e.g., the x direction) and a direction intersecting the longitudinal direction (e.g., the y direction).

[0042] The reinforcing member 14 is made of a fiber-reinforced resin, such as a thermoplastic fiber-reinforced resin. The reinforcing member 14 is formed by heating and pressurizing a prepreg sheet formed by impregnating reinforcing fibers with resin in a mold to form a shape. Carbon fiber, glass fiber, or aramid fiber can be used as the reinforcing fiber. The reinforcing fiber is preferably continuous fiber without joints or cuts, and preferably extends continuously along the uneven shape of the plate-shaped member 16. Engineering plastics such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) can be used as the thermoplastic resin impregnated into the reinforcing fiber. The main body member 12 can also be made of the same fiber-reinforced resin as the reinforcing member 14, and can also be made of the same thermoplastic fiber-reinforced resin as the reinforcing member 14. The main body member 12 or the reinforcing member 14 may be made of a thermosetting fiber-reinforced resin. In this case, an epoxy resin or the like can be used as the thermosetting resin impregnated into the reinforcing fiber.

[0043] 9(a) and 9(b) are schematic diagrams illustrating a method for forming a prepreg sheet. FIG. 9(a) shows a prepreg tape 50 used to form the prepreg sheet. The prepreg tape 50 is formed by impregnating a plurality of reinforcing fibers 52 oriented in a single direction with a thermoplastic resin 54. The reinforcing fibers 52 are oriented to extend in the longitudinal direction A of the prepreg tape 50. The thermoplastic resin 54 fills the gaps between the reinforcing fibers 52, fixing the fiber bundles formed from the reinforcing fibers 52 so that the relative positions of the reinforcing fibers 52 do not change. The width w of the prepreg tape 50 is not particularly limited, but is, for example, 1 mm or more and 20 mm or less, e.g., 2 mm or more and 10 mm or less. The length L of the prepreg tape 50 is greater than the outer size of the reinforcing member 14, e.g., 0.5 m or more or 1 m or more. The thickness of the prepreg tape 50 is, for example, 0.1 mm or more and 2 mm or less, for example, 0.2 mm or more and 1 mm or less.

[0044] FIG. 9( b ) shows a prepreg sheet 60 formed using the prepreg tape 50. The prepreg sheet 60 is formed by knitting a plurality of first prepreg tapes 56 extending in a first direction A1 and a plurality of second prepreg tapes 58 extending in a second direction A2 intersecting the first direction A1. Each of the first prepreg tapes 56 and the second prepreg tape 58 is configured in the same manner as the prepreg tape 50 shown in FIG. 9( a ). In the prepreg sheet 60 shown in FIG. 9( b ), the first direction A1 and the second direction A2 are perpendicular to each other. In other words, if the first direction A1 is the 0-degree direction, the second direction A2 is the 90-degree direction.

[0045] A first gap d1 is defined between the multiple first prepreg tapes 56. The first gap d1 is smaller than the width w1 of the first prepreg tape 56. The first gap d1 is, for example, 1% to 50% of the width w1 of the first prepreg tape 56, and preferably 5% to 25%. Similarly, a second gap d2 is defined between the multiple second prepreg tapes 58. The second gap d2 is smaller than the width w2 of the second prepreg tape 58. The second gap d2 is, for example, 1% to 50% of the width w2 of the second prepreg tape 58, and preferably 5% to 25%. The width w1 of the first prepreg tape 56 may be the same as or different from the width w2 of the second prepreg tape 58. The first gap d1 may be the same as or different from the second gap d2.

[0046] In the prepreg sheet 60, the intersecting first prepreg tapes 56 and second prepreg tapes 58 are not fixed to each other. Therefore, the first prepreg tapes 56 are displaceable relative to each other in the second direction A2, making the first gap d1 variable. Similarly, the second prepreg tapes 58 are displaceable relative to each other in the first direction A1, making the second gap d2 variable.

[0047] The resin weight content (wt %) of the prepreg sheet 60 is 50% or less, for example, 40% or less, 35% or less, 30% or less, or 25% or less. Reducing the resin weight content of the prepreg sheet 60 can increase the rigidity of the reinforcing member 14. The resin weight content (wt %) of the prepreg tape 50 forming the prepreg sheet 60 may be the same as the resin weight content of the prepreg sheet 60, and is 50% or less, for example, 40% or less, 35% or less, 30% or less, or 25% or less.

[0048] In the prepreg sheet 60 shown in FIG. 9( b), a first prepreg tape 56 and a second prepreg tape 58 are knitted to form a twill weave. The knitting method of the prepreg sheet is not limited to twill weave, and the prepreg sheet may be formed using any other knitting method, such as plain weave or satin weave. Furthermore, the prepreg sheet may be knitted using prepreg tapes extending in three or more directions. For example, the prepreg sheet may be knitted using a plurality of first prepreg tapes extending in a first direction (e.g., the 0 degree direction), a plurality of second prepreg tapes extending in a second direction (e.g., the +60 degree direction) intersecting the first direction, and a plurality of third prepreg tapes extending in a third direction (e.g., the −60 degree direction) intersecting the first and second directions.

[0049] A prepreg sheet may be knitted without using a prepreg tape in which unidirectional fibers are impregnated with a resin. A prepreg sheet may be formed, for example, by impregnating a continuous fiber sheet knitted using continuous fibers with a thermoplastic resin throughout. For example, a continuous fiber sheet may be formed by knitting a plurality of first continuous fibers extending in a first direction (e.g., the 0-degree direction) and a plurality of second continuous fibers extending in a second direction (e.g., the 90-degree direction) intersecting the first direction using a plain weave, twill weave, satin weave, or the like. A prepreg sheet may be formed by impregnating such a continuous fiber sheet with a thermoplastic resin. In this case, the first continuous fibers and second continuous fibers intersecting each other in the prepreg sheet are fixed with a resin between them.

[0050] 10 is a diagram schematically illustrating a method for molding the reinforcing member 14 according to the second embodiment. A mold 62 for molding the reinforcing member 14 is prepared, and multiple prepreg sheets 60a, 60b, and 60c are stacked and arranged between an upper mold 64 and a lower mold 66 of the mold 62. The upper mold 64 has a concave-convex shape corresponding to the first surface 16a of the plate-like member 16, and the lower mold 66 has a concave-convex shape corresponding to the second surface 16b of the plate-like member 16. The upper mold 64 and the lower mold 66 may be used upside down, regardless of their top-to-bottom relationship.

[0051] Each of the multiple prepreg sheets 60a-60c is configured similarly to the prepreg sheet 60 shown in FIG. 9(b). The multiple prepreg sheets 60a-60c include a first prepreg sheet 60a, a second prepreg sheet 60b, and an intermediate prepreg sheet 60c. The first prepreg sheet 60a is a sheet that contacts the upper mold 64 and constitutes the first surface 16a of the plate-like member 16. The second prepreg sheet 60b is a sheet that contacts the lower mold 66 and constitutes the second surface 16b of the plate-like member 16. The intermediate prepreg sheet 60c is disposed between the first prepreg sheet 60a and the second prepreg sheet 60b. In the example of FIG. 10, five prepreg sheets are stacked, including one first prepreg sheet 60a, one second prepreg sheet 60b, and three intermediate prepreg sheets 60c. The number of laminated prepreg sheets is not particularly limited and may be 4 or less, or 6 or less. The number of laminated prepreg sheets can be set appropriately depending on the thickness of the prepreg sheets and the thickness t of the reinforcing member 14 to be formed.

[0052] The multiple prepreg sheets 60a-60c may be arranged so that the orientation directions of the prepreg tapes constituting the prepreg sheets 60a-60c are different from one another. Figures 11(a) and 11(b) are schematic diagrams showing the orientation directions of the prepreg sheets 60a-60c. Figure 11(a) shows the orientation directions of the first prepreg sheet 60a and the second prepreg sheet 60b. In the first prepreg sheet 60a and the second prepreg sheet 60b, the orientation directions A1 and A2 of the first prepreg tape 56 and the second prepreg tape 58 are at 45 degrees with respect to the longitudinal direction (e.g., the x-direction) of the reinforcing member 14. Figure 11(b) shows the orientation direction of the intermediate prepreg sheet 60c. In the intermediate prepreg sheet 60c, the orientation direction A1 of the first prepreg tape 56 coincides with the longitudinal direction (e.g., the x-direction) of the reinforcing member 14. Therefore, the orientation directions A1, A2 of the intermediate prepreg sheet 60c are rotated by 45 degrees with respect to the orientation directions A1, A2 of the first prepreg sheet 60a and the second prepreg sheet 60b.

[0053] The plate-like member 16 can be formed by heating and pressurizing multiple prepreg sheets 60a to 60c between an upper mold 64 and a lower mold 66 shown in FIG. 10. The multiple prepreg sheets 60a to 60c in FIG. 10 are heated to a temperature equal to or higher than the melting point of the thermoplastic resin 54 by the upper mold 64 and the lower mold 66, which are equipped with heaters. The multiple prepreg sheets 60a to 60c are integrated by heating and pressurizing using a mold 62, and are shaped into the plate-like member 16. The plate-like member 16 is then removed from the mold 62, completing the plate-like member 16. After shaping using the mold 62, portions unnecessary for the reinforcing member 14 may be cut from the plate-like member 16, or the first surface 16a or the second surface 16b of the plate-like member 16 may be polished.

[0054] FIG. 12 is a top view of a reinforcing member 14 according to an embodiment. The reinforcing member 14 shown in FIG. 12 uses carbon fiber as the reinforcing fiber, PEEK as the thermoplastic resin, and the prepreg sheets 60a, 60b, and 60c shown in FIGS. 11(a) and 11(b). As shown in FIG. 12, a plate-shaped member 16 having a complex uneven shape including protrusions 22 and multiple recesses 24 can be formed. In particular, since there is almost no misalignment of the stitches of the prepreg tape extending in the ±45° direction throughout the entire plate-shaped member 16, the reinforcing member 14 can have high rigidity throughout the entire plate-shaped member 16. It can also be seen that the bottoms 34 of the multiple recesses 24 have a shape that is close to a rectangle.

[0055] 13 is a diagram schematically illustrating a joint 44 between the main body member 12 and the reinforcing member 14. The reinforcing member 14 is joined to the back surface 12b of the main body member 12. The reinforcing member 14 is joined to the main body member 12 by a plurality of joints 44. The plurality of joints 44 are provided between the back surface 12b of the main body member 12 and the second surface 16b of the reinforcing member 14. The plurality of joints 44 are provided on the outer periphery 20 and the bottom 34 of the reinforcing member 14. A cavity 48 is provided between the main body member 12 and the reinforcing member 14. The main body member 12, the reinforcing member 14, and the plurality of joints 44 correspond to the first member 210, the second member 220, and the metal member 230 according to the first embodiment.

[0056] Each of the multiple joints 44 can be configured in the same manner as the metal member 230 according to the first embodiment. The multiple joints 44 have a first surface that joins with the main body member 12 and a second surface that joins with the reinforcing member 14, with a metal material between the first and second surfaces, and metal oxide particle clusters formed on the first and second surfaces. The metal oxide particle clusters of the multiple joints 44 are chemically and physically bonded to the thermoplastic resin contained in the main body member 12 or the reinforcing member 14. The multiple joints 44 can be formed, for example, by disposing a metal member between the main body member 12 and the reinforcing member 14 and applying heat and pressure to the metal member between the main body member 12 and the reinforcing member 14.

[0057] 14 is a top view schematically illustrating the configuration of a metal member 250 according to the second embodiment. The metal member 250 includes an outer peripheral joint portion 252, an inner joint portion 254, an extension portion 256, a first connection portion 258, and a second connection portion 260.

[0058] The outer peripheral joining portion 252 is a portion that joins with the outer peripheral portion 20 of the reinforcing member 14. The outer peripheral joining portion 252 can have a shape similar to that of the outer peripheral portion 20 of the reinforcing member 14. The inner joining portion 254 is a portion that joins with the bottom portion 34 of the recess 24 of the reinforcing member 14.

[0059] The extending portion 256 is a portion that extends outward from the outer edge 18 of the reinforcing member 14, and is a non-bonded portion that is not bonded to the reinforcing member 14. In the example of Fig. 14, the extending portion 256 is provided so as to extend in the y direction, but the extending direction of the extending portion 256 does not matter, and it may extend in the x direction or obliquely with respect to the x direction or the y direction.

[0060] The first connection portion 258 is a portion that connects the outer peripheral bonding portion 252 and the inner bonding portion 254, and is a non-bonded portion that is not bonded to the reinforcing member 14. The second connection portion 260 is a portion that connects two adjacent inner bonding portions 254, and is a non-bonded portion that is not bonded to the reinforcing member 14. In the example of FIG. 14 , the first connection portion 258 and the second connection portion 260 extend in the y direction, but the direction in which the first connection portion 258 and the second connection portion 260 extend does not matter, and they may extend in the x direction or obliquely to the x direction or y direction. The metal member 250 may include two or more of a connection member that extends in the x direction, a connection member that extends in the y direction, and a connection member that extends obliquely to the x direction or y direction.

[0061] Metal oxide particle clusters are formed on both surfaces of the outer peripheral bonding portion 252 and the inner bonding portion 254. On the other hand, metal oxide particle clusters may not be formed on both surfaces of the extending portion 256, the first connecting portion 258, and the second connecting portion 260. The metal member 250 may not include at least one of the extending portion 256, the first connecting portion 258, and the second connecting portion 260. For example, the metal member 250 may include the first connecting portion 258 but not the second connecting portion 260. The metal member 250 may not include the extending portion 256, but may include at least one of the first connecting portion 258 and the second connecting portion 260.

[0062] The metal member 250 can be made of the same material as the metal member 230 according to the first embodiment. The thickness of the metal member 250 can be the same as the thickness of the metal member 230 according to the first embodiment, and can be, for example, 5 μm to 2 mm, for example, 10 μm to 1 mm, for example, 50 μm to 0.5 mm.

[0063] Next, a method for joining the main body member 12 and the reinforcing member 14 using the metal member 250 will be described. First, the metal member 250 is placed between the main body member 12 and the reinforcing member 14. Next, the metal member 250 is pressed between the main body member 12 and the reinforcing member 14. For example, by pressing the main body member 12 and the reinforcing member 14 using a mold corresponding to the shapes of the main body member 12 and the reinforcing member 14, it is possible to effectively pressurize the outer periphery 20 and the bottom 34, which are the joining points of the reinforcing member 14.

[0064] Next, the metal member 250 is heated while being pressurized between the main body member 12 and the reinforcing member 14. For example, the metal member 250 can be heated by utilizing the extension portion 256 that protrudes from between the main body member 12 and the reinforcing member 14. The extension portion 256 may be heated by irradiating it with electromagnetic waves such as laser light or infrared light. A power source may be connected to the extension portion 256 for resistance heating. A magnetic field may be applied to the extension portion 256 for induction heating. By heating the metal member 250 while applying pressure, the softened resin penetrates into the metal oxide particle clusters of the metal member 250 and chemically bonds to the resin. As a result, the main body member 12 and the reinforcing member 14 are firmly joined via the metal member 250.

[0065] If the metal member 250 does not include the extension portion 256, the outer peripheral bonding portion 252 and the inner bonding portion 254 may be directly heated. For example, the outer peripheral bonding portion 252 and the inner bonding portion 254 may be high-frequency induction heated by applying a magnetic field from the outside of the main body member 12 and the reinforcing member 14. In this case, the first connecting portion 258 and the second connecting portion 260 may be high-frequency induction heated, and the inner bonding portion 254 may be heated by heat transferred from the first connecting portion 258 and the second connecting portion 260.

[0066] After the main body member 12 and the reinforcing member 14 are joined, the extending portion 256 that protrudes outside the reinforcing member 14 can be cut and removed. However, the extending portion 256 does not have to be removed. Meanwhile, the first connecting portion 258 and the second connecting portion 260 remain between the main body member 12 and the reinforcing member 14. The first connecting portion 258 and the second connecting portion 260 may or may not be joined to the main body member 12 or the reinforcing member 14.

[0067] According to this embodiment, the reinforcing member 14 can be constructed using only a single plate-like member 16, thereby simplifying the structure of the reinforcing member 14 compared to when a honeycomb core is used. Furthermore, the reinforcing member 14 can be formed by extrusion molding using a mold 62, thereby simplifying the manufacturing process of the reinforcing member 14 compared to when a honeycomb core is used. The reinforcing member 14 includes a lattice-frame-shaped top portion 28 with beams extending in the longitudinal direction (e.g., the x-direction) and in a direction intersecting the longitudinal direction (e.g., the y-direction) of the reinforcing member 14, thereby enabling the reinforcing member 14 to withstand loads in both the longitudinal direction and the direction intersecting the longitudinal direction. As a result, the reinforcing member 14 can effectively suppress deformation of the main body member 12.

[0068] According to this embodiment, the reinforcing member 14 can be formed from continuous reinforcing fibers throughout the entire reinforcing member 14, thereby improving the rigidity of the reinforcing member 14 compared to when notches are provided midway through the reinforcing fibers. According to this embodiment, the outer inclined portion 30 and the inner inclined portion 36 are configured to be gently curved, which makes it possible to suppress misalignment of the stitches of the prepreg tape made of continuous fibers, thereby improving the overall rigidity of the reinforcing member 14.

[0069] According to this embodiment, by joining the main body member 12 and the reinforcing member 14 via the metal member 250, it is possible to dramatically improve the joining strength compared to when the metal member 250 is not used. Furthermore, by using the metal member 250 with a small thickness, it is possible to suppress the increase in weight due to the addition of the metal member 250. As a result, it is possible to provide a joined structure 10 that is lightweight and has excellent rigidity.

[0070] According to this embodiment, the metal member 250 includes the first connecting portion 258 and the second connecting portion 260, allowing the inner joint portion 254 to be heated via the connecting portions. For example, if the main body member 12 and the reinforcing member 14 are made of carbon fiber reinforced plastics (CFRP), the black carbon fibers make it difficult to externally irradiate the inner joint portion 254 between the main body member 12 and the reinforcing member 14 with electromagnetic waves for heating. Furthermore, because carbon fibers are conductive, induction heating performed by externally applying a magnetic field may heat the carbon fibers, resulting in insufficient heating of the inner joint portion 254. When the metal member 250 is externally heated, the outer surface of the main body member 12 or the reinforcing member 14 may be heated to a high temperature, potentially resulting in deformation of the main body member 12 or the reinforcing member 14. According to this embodiment, the inner joint portion 254 can be sufficiently heated through the connection portion, thereby improving the joint strength between the main body member 12 and the reinforcing member 14 at the inner joint portion 254 and providing a joint structure 10 with superior rigidity.

[0071] According to this embodiment, by making the first connecting portion 258 and the second connecting portion 260 non-bonded portions, it is possible to prevent the main body member 12 or the reinforcing member 14 from contacting the connecting portions. This makes it possible to prevent the surfaces of the main body member 12 and the reinforcing member 14 from softening and deforming in areas where bonding is not required. Furthermore, by providing the first connecting portion 258 and the second connecting portion 260, it is possible to appropriately position the inner bonding portion 254 at the bonding location. In particular, by providing a connecting portion that is not bonded to the main body member 12 or the reinforcing member 14, it is possible to more appropriately position the inner bonding portion 254 at the bonding location.

[0072] 15 is a perspective view schematically illustrating the configuration of a reinforcing member 70 according to a modified example, showing the reinforcing member 70 as viewed from the first surface 16a. The reinforcing member 70 differs from the above-described embodiment in that it further includes a first rib 72 provided on the first surface 16a of the plate-shaped member 16. The plate-shaped member 16 has the same configuration as in the above-described embodiment.

[0073] The reinforcing member 70 includes a plate-shaped member 16 and a first rib 72. The first rib 72 is provided on the first surface 16a of the plate-shaped member 16 and extends from the first surface 16a in the thickness direction. The first rib 72 is provided inside at least one of the multiple recesses 24. In the example of FIG. 15 , the first rib 72 is provided inside the recess 24 at the center in the longitudinal direction (e.g., the x direction). The first rib 72 may be provided inside any two or more of the multiple recesses 24, or may be provided inside all of the multiple recesses 24. The upper surface of the first rib 72 is configured to be flush with the apex 28, for example.

[0074] The first rib 72 includes a first horizontal rib 74 extending in the longitudinal direction (e.g., the x direction) and a first vertical rib 76 extending in a direction intersecting the longitudinal direction (e.g., the y direction). Both ends of the first horizontal rib 74 are connected to the outer edge 32 of the recess 24. Both ends of the first vertical rib 76 are connected to the outer edge 32 of the recess 24. The first horizontal rib 74 and the first vertical rib 76 are connected to each other and intersect at the bottom 34 of the recess 24. The first rib 72 may further include a first diagonal rib (not shown) extending in a diagonal direction (e.g., ±45 degrees) relative to the first horizontal rib 74 or the first vertical rib 76. The first rib 72 may include any one or more selected from the group consisting of the first horizontal rib 74, the first vertical rib 76, and the first diagonal rib.

[0075] 16 is a perspective view schematically illustrating the configuration of a reinforcing member 70 according to a modified example, showing the reinforcing member 70 as viewed from the second surface 16b. The reinforcing member 70 further includes a second rib 82 provided on the second surface 16b of the plate-shaped member 16. The lower surface of the second rib 82 is configured to be flush with the outer circumferential portion 20 and the bottoms 34 of the plurality of recesses 24. The lower surface of the second rib 82 is configured to be located on the imaginary plane B shown in FIG. 7, for example.

[0076] The second rib 82 is provided on the second surface 16b of the plate-like member 16 and extends from the second surface 16b in the thickness direction. The second rib 82 is provided inside the protrusion 22. The second rib 82 includes second horizontal ribs 84a, 84b extending in the longitudinal direction (e.g., the x direction), second vertical ribs 86a, 86b extending in a direction intersecting the longitudinal direction (e.g., the y direction), and second diagonal ribs 88a, 88b extending in diagonal directions (e.g., ±45 degree directions).

[0077] The second transverse ribs 84a, 84b include a second outer transverse rib 84a connecting the outer periphery 20 and the bottom portion 34, and a second inner transverse rib 84b connecting the two bottom portions 34. The second longitudinal ribs 86a, 86b include a second outer longitudinal rib 86a connecting the outer periphery 20 and the bottom portion 34, and a second inner longitudinal rib 86b connecting the two bottom portions 34. The second diagonal ribs 88a, 88b include a second outer diagonal rib 88a connecting the outer periphery 20 and the bottom portion 34, and a second inner diagonal rib 88b connecting the two bottom portions 34. The second rib 82 may include any one or more selected from the group consisting of the second outer transverse rib 84a, the second inner transverse rib 84b, the second longitudinal rib 86a, the second inner longitudinal rib 86b, the second outer diagonal rib 88a, and the second inner diagonal rib 88b.

[0078] The first rib 72 and the second rib 82 are made of fiber-reinforced resin. The first rib 72 and the second rib 82 may be made of the same thermoplastic fiber-reinforced resin or thermosetting fiber-reinforced resin as the plate-shaped member 16, or may be made of a thermoplastic fiber-reinforced resin or thermosetting fiber-reinforced resin of a material different from that of the plate-shaped member 16. Carbon fiber, glass fiber, or aramid fiber can be used as the reinforcing fiber making up the first rib 72 and the second rib 82. Engineering plastics such as thermoplastic resins such as PEEK and PEKK, and thermosetting resins such as epoxy resin can be used as the resin making up the first rib 72 and the second rib 82. For example, the first rib 72 and the second rib 82 may be made of reinforcing fibers that are not continuous with the reinforcing fibers making up the plate-shaped member 16.

[0079] 17 is a diagram schematically illustrating a method for molding a reinforcing member 70 according to a modified example. A mold 92 for molding the reinforcing member 70 according to the modified example differs from the mold 62 according to the above-described embodiment in that it includes grooves 98, 100 for molding the first rib 72 and the second rib 82. The upper mold 94 has a concave-convex shape corresponding to the first surface 16a of the plate-like member 16 and includes a first groove 98 for forming the first rib 72. The lower mold 96 has a concave-convex shape corresponding to the second surface 16b of the plate-like member 16 and includes a second groove 100 for forming the second rib 82.

[0080] The first groove 98 is filled with prepreg 90a, and the second groove 100 is filled with prepreg 90b. The prepregs 90a and 90b filled in the grooves 98 and 100 are, for example, chopped materials obtained by cutting the prepreg tape 50 or the prepreg sheet 60. The size (width and length) of the prepregs 90a and 90b is not particularly limited. The width of the prepregs 90a and 90b is 1 mm or more and 20 mm or less, for example, 2 mm or more and 10 mm or less. The length of the prepregs 90a and 90b is 5 mm or more and 50 mm or less, for example, 10 mm or more and 30 mm or less.

[0081] A plurality of prepreg sheets 60a, 60b, and 60c are stacked and arranged between an upper mold 94 in which the first groove 98 is filled with prepreg 90a and a lower mold 96 in which the second groove 100 is filled with prepreg 90b. The plurality of prepreg sheets 60a, 60b, and 60c are the same as those in the above-described embodiment.

[0082] 17 , a reinforcing member 70 having a first rib 72 and a second rib 82 formed on a plate-like member 16 can be molded by heating and pressurizing the multiple prepreg sheets 60a-60c and prepregs 90a, 90b between an upper mold 94 and a lower mold 96. The multiple prepreg sheets 60a-60c and prepregs 90a, 90b are heated to a temperature equal to or higher than the melting point of the thermoplastic resin 54 by the upper mold 94 and the lower mold 96, which are equipped with heaters. The multiple prepreg sheets 60a-60c and prepregs 90a, 90b are integrated by heating and pressurizing using a mold 92, and are shaped into the reinforcing member 70. The reinforcing member 70 is then completed by removing it from the mold 92.

[0083] According to this modified example, a first rib 72 is formed on the first surface 16a of the plate-shaped member 16, and a second rib 82 is formed on the second surface 16b of the plate-shaped member 16, thereby further improving the rigidity of the reinforcing member 70.

[0084] The reinforcing member 70 according to this modification can be used by being joined to the main body member 12. For example, in addition to the outer periphery 20 and the bottom 34 of the reinforcing member 70, the lower surface of the second rib 82 can be joined to the back surface 12b of the main body member 12. The reinforcing member 70 can be joined to the main body member 12 in the same manner as in the above-described embodiment. The metal member 250 can further include an inner joining portion that joins to the second rib 82. The joined structure 10 can include the main body member 12, the reinforcing member 70 according to this modification, and the metal member 250.

[0085] In further variations, the reinforcing member 70 may include only one of the first rib 72 and the second rib 82. The reinforcing member 70 may include only the first rib 72 and not the second rib 82. The reinforcing member 70 may include only the second rib 82 and not the first rib 72.

[0086] 18 is a side cross-sectional view schematically illustrating the configuration of a joint structure 110 according to a third embodiment. The joint structure 110 according to this embodiment has a so-called sandwich panel structure. The joint structure 110 includes a first main body member 112, a second main body member 114, a first reinforcing member 116, and a second reinforcing member 118.

[0087] The first body member 112 and the second body member 114 are members that correspond to the skins of the sandwich panel. Each of the first body member 112 and the second body member 114 can be configured similarly to the body member 12 according to the above-described embodiment. The first reinforcing member 116 and the second reinforcing member 118 are members that correspond to the core of the sandwich panel. Each of the first reinforcing member 116 and the second reinforcing member 118 can be configured similarly to the reinforcing member 14 according to the above-described embodiment or the reinforcing member 70 according to the modified example.

[0088] The first reinforcing member 116 includes a first outer periphery 120, a first top portion 122, and a plurality of first bottom portions 124. The first reinforcing member 116 is joined to the first body member 112 via a plurality of first joints 126. The first body member 112 is joined to the first outer periphery 120 and the plurality of first bottom portions 124 via the plurality of first joints 126. A first cavity 128 is provided between the first body member 112 and the first reinforcing member 116.

[0089] The second reinforcing member 118 includes a second outer periphery 130, a second top portion 132, and a plurality of second bottom portions 134. The second reinforcing member 118 is joined to the second body member 114 via a plurality of second joints 136. The second body member 114 is joined to the second outer periphery 130 and the plurality of second bottom portions 134 via a plurality of second joints 136. A second cavity 138 is provided between the second body member 114 and the second reinforcing member 118.

[0090] The first reinforcing member 116 is joined to the second reinforcing member 118 via a third joint 140. The third joint 140 is provided between the first apex 122 and the second apex 132. A third cavity 142 is provided between the first reinforcing member 116 and the second reinforcing member 118.

[0091] Each of the first bonding portion 126, the second bonding portion 136, and the third bonding portion 140 can be configured in the same manner as the bonding portion 44 according to the second embodiment described above. For example, a first metal member, a second metal member, and a third metal member having metal oxide particle clusters formed on both sides are prepared, and the first body member 112 and the first reinforcing member 116 can be bonded together with the first metal member, the second body member 114 and the second reinforcing member 118 can be bonded together with the second metal member, and the first reinforcing member 116 and the second reinforcing member 118 can be bonded together with the third metal member.

[0092] According to this embodiment, a sandwich panel structure can be realized by combining four plate-like members. According to this embodiment, the structure of the joined structure 110 can be simplified compared to when a honeycomb core is used, and the manufacturing process of the joined structure 110 can be simplified.

[0093] The present invention has been described above based on examples. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, and that various design changes and modifications are possible, and that such modifications are also within the scope of the present invention.

[0094] Several aspects of the present invention will now be described.

[0095] A first aspect of the present invention is a reinforcing member comprising a plate-shaped member made of fiber-reinforced resin using continuous fibers as reinforcing fibers and having a first surface and a second surface, the plate-shaped member comprising an outer periphery defining an outer edge of the plate-shaped member, a convex portion inside the outer periphery that is convex toward the first surface, and a plurality of concave portions inside the convex portion that is concave toward the first surface. According to the first aspect, by providing a convex-convex structure in which the convex portion is provided inside the convex portion and the concave portion is provided inside the convex portion, deformation such as deflection due to loads in both the longitudinal direction and the direction transverse to the longitudinal direction of the reinforcing member can be suitably suppressed. Furthermore, by providing a convex-concave structure in the plate-shaped member, the plate-shaped member can be constructed of fiber-reinforced resin using continuous fibers as reinforcing fibers, thereby realizing a lightweight and highly rigid reinforcing member.

[0096] In a second aspect of the present invention, the reinforcing member according to the first aspect is characterized in that the plurality of recesses are arranged in a lattice pattern or a radial pattern. According to the second aspect, by arranging the plurality of recesses in a lattice pattern or a radial pattern, deformation due to a load in the direction in which the plurality of recesses are arranged can be suitably suppressed.

[0097] A third aspect of the present invention is the reinforcing member according to the first or second aspect, wherein the outer edge of the convex portion has a shape in which the four corners of a rectangle are arcuate, and the outer edge of each of the plurality of recesses has a shape in which the four corners of a rectangle are arcuate. According to the third aspect, by approximating the outer edges of the convex portion and each of the plurality of recesses to a rectangle, deformation due to a load in a direction along the sides of the rectangle can be suitably suppressed. Furthermore, by making the four corners of the outer edges of the convex portion and each of the plurality of recesses arc-shaped, it becomes easier to uniformly arrange continuous fibers along the surfaces of the convex portion and each of the plurality of recesses, thereby improving the overall rigidity of the reinforcing member.

[0098] In a fourth aspect of the present invention, the reinforcing member according to the third aspect is characterized in that the bottom of each of the plurality of recesses has a rectangular shape or a rectangular shape with rounded corners. According to the fourth aspect, by approximating the bottom of each of the plurality of recesses to a rectangular shape, deformation due to a load in a direction along the sides of the rectangle can be suitably suppressed.

[0099] In a fifth aspect of the present invention, there is provided a reinforcing member according to any one of the first to fourth aspects, wherein the first and second surfaces have a radius of curvature of 20 mm or more in a cross section perpendicular to the outer edge of the plate-like member. According to the fifth aspect, by making the radius of curvature of the first and second surfaces 20 mm or more, it becomes easy to uniformly arrange continuous fibers along the first and second surfaces, thereby improving the overall rigidity of the reinforcing member.

[0100] In a sixth aspect of the present invention, there is provided the reinforcing member according to any one of the first to fifth aspects, wherein the fiber-reinforced resin includes a continuous fiber sheet woven with a plurality of continuous fibers extending in a first direction and a plurality of continuous fibers extending in a second direction intersecting the first direction. According to the sixth aspect, by using a continuous fiber sheet woven with a plurality of continuous fibers extending in the first and second directions intersecting each other, deformation such as deflection due to loads in both the longitudinal direction of the reinforcing member and the direction intersecting the longitudinal direction can be suitably suppressed.

[0101] A seventh aspect of the present invention is the reinforcing member according to any one of the first to sixth aspects, which is made of fiber-reinforced resin and further includes a rib extending from the first surface or the second surface. According to the seventh aspect, by providing a rib on the first surface or the second surface of the plate-like member, the rigidity of the reinforcing member can be further improved.

[0102] In an eighth aspect of the present invention, the reinforcing member according to the seventh aspect is characterized in that the rib includes a first rib extending from the first surface inside at least one of the recesses. According to the eighth aspect, by providing the first rib inside the recess, deformation of the recess can be more suitably suppressed, and the rigidity of the reinforcing member can be further improved.

[0103] In a ninth aspect of the present invention, the reinforcing member according to the seventh or eighth aspect is characterized in that the rib further includes a second rib extending from the second surface on an inner side of the protrusion. According to the ninth aspect, by providing the second rib on the inner side of the protrusion, deformation of the protrusion can be more suitably suppressed, and the rigidity of the reinforcing member can be further improved.

[0104] In a tenth aspect of the present invention, the second rib connects the bottom of at least one of the recesses to the outer periphery, and the second rib connects the bottom and the outer periphery to the outer periphery. According to the tenth aspect, by providing the second rib connecting the bottom and the outer periphery, deformation of the bottom relative to the outer periphery can be more suitably suppressed, and the rigidity of the reinforcing member can be further improved.

[0105] In an eleventh aspect of the present invention, the second rib connects two bottom portions of the plurality of recesses to each other, and the second rib connects two bottom portions of the plurality of recesses to each other. According to the eleventh aspect, by providing the second rib connecting the two bottom portions, deformation of the bottom portions can be more suitably suppressed, and the rigidity of the reinforcing member can be further improved.

[0106] In a twelfth aspect of the present invention, there is provided the reinforcing member according to any one of the first to eleventh aspects, wherein the resin weight content of the fiber reinforced resin is 50% or less. According to the twelfth aspect, by setting the resin weight content of the fiber reinforced resin to 50% or less, the rigidity of the reinforcing member can be further improved.

[0107] A thirteenth aspect of the present invention is a joined structure comprising the reinforcing member according to any one of the first to twelfth aspects and a main body member joined to the outer periphery of the reinforcing member and to the bottoms of each of the plurality of recesses, wherein a cavity is provided between the reinforcing member and the main body member. According to the thirteenth aspect, by joining the reinforcing member to the main body member, deformation of the main body member can be suppressed by the reinforcing member, thereby providing a joined structure with excellent rigidity. Furthermore, since a cavity is provided between the reinforcing member and the main body member, a joined structure that is lightweight and highly rigid can be provided.

[0108] A fourteenth aspect of the present invention is a manufacturing method comprising the steps of: arranging a prepreg sheet, in which continuous fibers are impregnated with resin, on a mold for molding a plate-shaped member having a first surface and a second surface; a convex portion inside the outer periphery that is convex toward the first surface; and a plurality of concave portions inside the convex portion that are concave toward the first surface; and heating and pressurizing the prepreg sheet using the mold to mold a reinforcing member including the plate-shaped member made of fiber-reinforced resin. According to the fourteenth aspect, the reinforcing member can be manufactured by shaping the prepreg sheet using a mold, thereby simplifying the manufacturing process of the reinforcing member. Furthermore, by using a prepreg sheet in which continuous fibers are impregnated with resin, the arrangement of the prepreg can be simplified compared to using small cut prepregs, and the rigidity of the molded reinforcing member can be improved.

[0109] A fifteenth aspect of the present invention is the manufacturing method according to the fourteenth aspect, wherein the prepreg sheet is formed by knitting a plurality of first prepreg tapes extending in a first direction and a plurality of second prepreg tapes extending in a second direction intersecting the first direction, and each of the first prepreg tapes and the second prepreg tapes is formed by impregnating a plurality of continuous fibers extending in a single direction with the resin. According to the fifteenth aspect, the gaps between the prepreg tapes are variable to match the uneven shape of the mold during molding, making it easier to more uniformly arrange the prepreg tapes along the uneven shape of the mold. As a result, a reinforcing member with uniformly arranged prepreg tapes can be molded, thereby improving the rigidity of the reinforcing member.

[0110] A sixteenth aspect of the present invention is the manufacturing method according to the fourteenth aspect, wherein the prepreg sheet is formed by impregnating a continuous fiber sheet formed by weaving a plurality of first continuous fibers extending in a first direction and a plurality of second continuous fibers extending in a second direction intersecting the first direction with the resin. According to the sixteenth aspect, by using a continuous fiber sheet formed by weaving a plurality of continuous fibers extending in the first direction and the second direction intersecting each other, the rigidity of the molded reinforcing member can be improved.

[0111] A seventeenth aspect of the present invention is the manufacturing method according to any one of the fourteenth to sixteenth aspects, wherein the mold has a groove for forming a rib extending from the first surface or the second surface, and further comprises a step of filling the groove of the mold with prepreg, and molding the reinforcing member in which the rib made of fiber-reinforced resin is joined to the first surface or the second surface of the plate-like member by heating and pressurizing the prepreg sheet and the prepreg using the mold. According to the seventeenth aspect, since the rib can be formed in the reinforcing member, the rigidity of the molded reinforcing member can be further improved. By filling the groove of the mold with prepreg, a reinforcing member in which the plate-like member and the rib are integrated can be easily manufactured.

[0112] An eighteenth aspect of the present invention is the manufacturing method according to any one of the fourteenth to seventeenth aspects, further comprising the step of joining the outer periphery of the reinforcing member and the bottoms of each of the plurality of recesses to a surface of the main body member to form a joined structure. According to the eighteenth aspect, by joining the reinforcing member to the surface of the main body member, a lightweight and highly rigid joined structure can be easily manufactured.

[0113] A nineteenth aspect of the present invention is a joining method comprising the steps of: placing a metal member having a first surface on which first metal oxide particle clusters are formed and a second surface on which second metal oxide particle clusters are formed, the metal member having a thickness of 1 mm or less from the first surface to the second surface, between a first member containing a first thermoplastic resin and a second member containing a second thermoplastic resin; and heating and pressurizing the metal member between the first member and the second member to bond the first surface to the first resin and the second surface to the second resin. According to the nineteenth aspect, by using a metal member on which metal oxide particle clusters are formed, the thermoplastic resin and the metal member can be firmly bonded, thereby improving the bonding strength between the first member and the second member. Furthermore, by making the thickness of the metal member 1 mm or less, the weight increase due to the addition of the metal member can be suppressed, and a lightweight joined structure with excellent rigidity can be provided.

[0114] A twentieth aspect of the present invention is the joining method according to the nineteenth aspect, in which the metal members are heated by at least one of irradiating the metal members with electromagnetic waves, passing a current through the metal members, and applying a magnetic field to the metal members. According to the twentieth aspect, by heating the metal members, only the surfaces of the first member and the second member in contact with the metal members are heated and softened, thereby joining the first member and the second member. This makes it possible to suppress deformation of the first member and the second member due to heating, and improve the quality of the joined structure.

[0115] A twenty-first aspect of the present invention is the joining method according to the nineteenth or twentieth aspect, wherein the metal members include a joining portion located between the first member and the second member and an extending portion extending from between the first member and the second member, and the metal members are heated by at least one of irradiating the extending portion with electromagnetic waves, passing a current through the extending portion, and applying a magnetic field to the extending portion. According to the twenty-first aspect, by providing an extending portion that extends beyond the gap between the first member and the second member, the metal members sandwiched between the first member and the second member can be effectively heated.

[0116] A twenty-second aspect of the present invention is the joining method according to the twenty-first aspect, further comprising the step of removing the extending portion after joining the joining portion to the first member and the second member. According to the twenty-second aspect, by removing the extending portion that does not contribute to the joining, a lighter joined structure can be provided.

[0117] A 23rd aspect of the present invention is the joining method according to any one of the 19th to 22nd aspects, further comprising a step of preheating the metal member before placing it between the first member and the second member. According to the 23rd aspect, by preheating the metal member, it is possible to shorten the heating step after sandwiching the metal member between the first member and the second member, and it is possible to improve productivity.

[0118] In a twenty-fourth aspect of the present invention, there is provided the joining method according to any one of the nineteenth to twenty-third aspects, wherein at least one of the first member and the second member is made of a fiber-reinforced resin containing reinforcing fibers extending in a direction along the first surface or the second surface. According to the twenty-fourth aspect, by using a fiber-reinforced resin, a lightweight and highly rigid joined structure can be provided.

[0119] In a twenty-fifth aspect of the present invention, there is provided the joining method according to the twenty-fourth aspect, wherein the reinforcing fibers include carbon fibers, glass fibers, or aramid fibers. According to the twenty-fifth aspect, by using carbon fibers, glass fibers, or aramid fibers as the reinforcing fibers, a lightweight and highly rigid joined structure can be provided.

[0120] In a twenty-sixth aspect of the present invention, there is provided the joining method according to any one of the nineteenth to twenty-fifth aspects, wherein at least one of the first resin and the second resin is aromatic polyether ketone (PAEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyphenylene sulfide (PPS), polyetherimide (PEI), or polyethersulfone (PES). According to the twenty-sixth aspect, by using an engineering plastic as the first resin or the second resin, a lightweight and highly rigid joined structure can be provided.

[0121] A 27th aspect of the present invention is the joining method according to any one of the 19th to 26th aspects, wherein the metal member comprises a steel material, an aluminum material, an aluminum alloy material, a titanium material, a titanium alloy material, a nickel-titanium alloy material, a copper material, or a copper alloy material. According to the 27th aspect, by using these metal materials, the bonding strength between the metal oxide particle clusters and the resin can be improved.

[0122] A 28th aspect of the present invention is the joining method according to any one of the 19th to 27th aspects, wherein the metal member includes an outer peripheral joining portion joined to an outer peripheral portion of the second member, an inner joining portion joined to a portion of the second member away from the outer peripheral portion, and a connecting portion connecting the outer peripheral joining portion and the inner joining portion. According to the 28th aspect, by providing the connecting portion connecting the outer peripheral joining portion and the inner joining portion of the metal member, it is possible to appropriately heat the inner joining portion and improve the joining strength of the inner joining portion.

[0123] A 29th aspect of the present invention is the joining method according to the 28th aspect, wherein the connecting portion is not joined to the first member or the second member. According to the 29th aspect, the connecting portion contacts the first member or the second member at a location where joining is not required, thereby preventing deformation of the first member or the second member due to heating. Furthermore, by providing a connecting portion that is not joined to the first member or the second member, the inner joining portion can be appropriately positioned at the joining location.

[0124] A thirtieth aspect of the present invention is a bonded structure comprising: a first member containing a first thermoplastic resin; a second member containing a second thermoplastic resin; and a metal member having a first surface on which first metal oxide particle clusters bonded to the first resin of the first member are formed; and a second surface on which second metal oxide particle clusters bonded to the second resin of the second member are formed, the thickness from the first surface to the second surface being 5 μm to 1 mm. According to the thirtieth aspect, by using the metal member on which metal oxide particle clusters are formed, a strong bond with the thermoplastic resin can be achieved, thereby improving the bond strength between the first member and the second member. Furthermore, by making the thickness of the metal member 1 mm or less, the weight increase due to the addition of the metal member can be suppressed, resulting in a lightweight bonded structure with excellent rigidity.

[0125] According to one aspect of the present invention, a lightweight joined structure with excellent rigidity can be provided.

[0126] DESCRIPTION OF SYMBOLS 10, 110, 200... Jointed structure, 12... Main body member, 14... Reinforcing member, 16... Plate-shaped member, 16a... First surface, 16b... Second surface, 18... Outer edge, 20... Outer periphery, 22... Convex portion, 24... Concave portion, 26... Outer edge, 28... Top, 30... Outer inclined portion, 32... Outer edge, 34... Bottom, 36... Inner inclined portion, 50... Prepreg tape, 52... Reinforcing fiber, 54... Thermoplastic resin, 56... First prepreg tape, 58... Second prepreg tape , 60...prepreg sheet, 210...first member, 220...second member, 230, 250...metal member, 232...first surface, 234...second surface, 236...first metal oxide particle cluster, 238...second metal oxide particle cluster, 240...joining portion, 242...first extension portion, 244...second extension portion, 252...peripheral joining portion, 254...inner joining portion, 256...extension portion, 258...first connecting portion, 260...second connecting portion.

Claims

1. A bonding method comprising the steps of: placing a metal member having a first surface on which first metal oxide particle clusters are formed and a second surface on which second metal oxide particle clusters are formed, the metal member having a thickness of 1 mm or less from the first surface to the second surface, between a first member containing a first thermoplastic resin and a second member containing a second thermoplastic resin; and heating and pressurizing the metal member between the first member and the second member, thereby bonding the first surface to the first resin and bonding the second surface to the second resin.

2. The joining method according to claim 1, wherein the metal members are heated by at least one of irradiating the metal members with electromagnetic waves, passing an electric current through the metal members, and applying a magnetic field to the metal members.

3. The joining method according to claim 1, wherein the metal member comprises a joining portion located between the first member and the second member, and an extension portion extending from between the first member and the second member, and the metal member is heated by at least one of irradiating the extension portion with electromagnetic waves, passing a current through the extension portion, and applying a magnetic field to the extension portion.

4. The joining method according to claim 3, further comprising the step of removing said extending portion after joining said joining portion to said first member and said second member.

5. A joining method according to any one of claims 1 to 4, further comprising the step of preheating the metal member before placing it between the first member and the second member.

6. A joining method according to any one of claims 1 to 5, wherein at least one of the first member and the second member is made of a fiber-reinforced resin containing reinforcing fibers extending in a direction along the first surface or the second surface.

7. The bonding method of claim 6, wherein the reinforcing fibers comprise carbon fibers, glass fibers, or aramid fibers.

8. The bonding method according to any one of claims 1 to 7, wherein at least one of the first resin and the second resin is aromatic polyetherketone (PAEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyphenylene sulfide (PPS), polyetherimide (PEI), or polyethersulfone (PES).

9. The joining method according to any one of claims 1 to 8, wherein the metal members comprise a steel material, an aluminum material, an aluminum alloy material, a titanium material, a titanium alloy material, a nickel-titanium alloy material, a copper material, or a copper alloy material.

10. A joining method according to any one of claims 1 to 9, wherein the metal member comprises an outer peripheral joining portion joined to the outer peripheral portion of the second member, an inner joining portion joined to a portion of the second member away from the outer peripheral portion, and a connecting portion connecting the outer peripheral joining portion and the inner joining portion.

11. The joining method according to claim 10, wherein the connecting portion is not joined to the first member or the second member.

12. A bonded structure comprising: a first member containing a first thermoplastic resin; a second member containing a second thermoplastic resin; and a metal member having a first surface on which first metal oxide particle clusters are formed and bonded to the first resin of the first member, and a second surface on which second metal oxide particle clusters are formed and bonded to the second resin of the second member, the thickness from the first surface to the second surface being 5 μm or more and 1 mm or less.

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