Joining body and method for manufacturing joining body

Abstract

The present invention has: a first thermoplastic fiber composite section in which a first fiber member is mixed with a first thermoplastic matrix resin; a second thermoplastic fiber composite section in which a second fiber member is mixed with a second thermoplastic matrix resin; a joining section that joins the first thermoplastic fiber composite section and the second thermoplastic fiber composite section; and a stretched section which, with the first thermoplastic fiber composite section and the second thermoplastic fiber composite section in an unjoined state, stretches around the joining section, centered on the joining section, extending between the first thermoplastic fiber composite section and the second thermoplastic fiber composite section, wherein the joining section is made of a resin identical to the first matrix resin. (Selected drawing: fig. 1)

Description

Joint body and method for manufacturing the same

[0001] The present disclosure relates to a bonded structure formed by welding thermoplastic fiber composite materials and a method for manufacturing the same.

[0002] Although metal members have been used as components of transportation equipment such as aircraft, trains, and automobiles, resin members are being used to reduce weight. In particular, fiber composite materials, in which fiber members are mixed with thermosetting or thermoplastic resins, are being used, and each component is formed by bonding multiple fiber composite materials.

[0003] Fiber reinforced plastics (FRP) are known as an example of a fiber composite material (thermosetting fiber composite material) using a thermosetting resin as a matrix. In particular, glass fiber reinforced plastics (GFRP), in which continuous glass fibers, woven fabric, or short glass fibers are solidified with a thermosetting resin such as an unsaturated polyester resin or an epoxy resin, and carbon fiber reinforced plastics (CFRP), in which carbon fibers are used, are used in various industries. Because these components have a high specific modulus of elasticity or specific strength, they are also used as aerospace materials, which require light weight, high strength, and high rigidity.

[0004] Another example of a fiber composite material (thermoplastic fiber composite material) using a thermoplastic resin such as polypropylene as a matrix is ​​fiber reinforced thermoplastics (FRTP) injection-molded using short glass fibers or carbon fibers. Similar to FRP, there are glass fiber reinforced thermoplastics (GFRTP) using glass fibers and carbon fiber reinforced thermoplastics (CFRTP) using carbon fibers. These components are also being developed for use in aerospace and other fields where lightweight, high strength, and high rigidity are required.

[0005] Methods for joining fiber composite materials include using fasteners such as bolts to connect the fiber composite materials, melting the resin in the matrix to bond the fiber composite materials, and using an adhesive different from the fiber composite materials. For example, Patent Document 1 discloses joining thermoplastic fiber composite materials using an adhesive. In particular, Patent Document 1 describes a method of joining two thermoplastic fiber composite materials using an adhesive, in which a conductive insert material made of a resin film and a conductive film is placed between the two thermoplastic fiber composite materials, and the materials are bonded by heating.

[0006] JP 2023-116129 A

[0007] However, applying an adhesive to the entire surface of a fiber composite material as disclosed in Patent Document 1 increases the manufacturing cost of the bonded body. On the other hand, limiting the area where the adhesive is applied reduces the manufacturing cost of the bonded body, but reduces the bonding strength of the bonded body. Furthermore, the presence of gaps in the resulting bonded body may lead to a decrease in the reliability of the bonded body.

[0008] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a bonded body and a method for manufacturing the same that can reduce manufacturing costs while improving the reliability and bonding strength of the bonded body.

[0009] According to one aspect of the present disclosure, there is provided a bonded body comprising: a first thermoplastic fiber composite portion in which a first fiber member is mixed with a first thermoplastic matrix resin; a second thermoplastic fiber composite portion in which a second fiber member is mixed with a second thermoplastic matrix resin; a joint portion joining the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion; and an extension portion extending around the joint portion and between the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion when the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion are not joined, the joint portion being made of the same resin as the first matrix resin.

[0010] According to one aspect of the present disclosure, there is provided a method for manufacturing a bonded body, comprising: a preparation step of preparing a first thermoplastic fiber composite member having first fiber components mixed in a first thermoplastic matrix resin, and a second thermoplastic fiber composite member having second fiber components mixed in a second thermoplastic matrix resin; a convex portion forming step of forming convex portions made of the same resin as the first matrix resin on a surface of the first thermoplastic fiber composite member; and a joint forming step of melting the convex portions in a state in which the second thermoplastic fiber composite members are laminated on the convex portion forming surface of the first thermoplastic fiber composite member to form joints joining the first thermoplastic fiber composite member and the second thermoplastic fiber composite member, wherein in the joint forming step, the convex portions are extended in a direction perpendicular to the lamination direction of the second thermoplastic fiber composite member, to form extensions that are not joined to the first thermoplastic fiber composite member and the second thermoplastic fiber composite member and extend between the first thermoplastic fiber composite member and the second thermoplastic fiber composite member.

[0011] According to the present disclosure, it is possible to provide a bonded body and a method for manufacturing the same that can reduce manufacturing costs while improving the reliability and bonding strength of the bonded body.

[0012] It should be noted that the above effects are merely examples for the sake of convenience of explanation, and the effects of the present disclosure are not limited to these. In addition to the above effects, the present disclosure can achieve any of the effects described herein.

[0013] FIG. 1 is a cross-sectional view of a bonded body according to the first embodiment; FIG. 2 is a plan view of a bonded body according to the first embodiment in a separated state; FIG. 3 is a cross-sectional view in a manufacturing process of a bonded body according to the first embodiment, showing a preparation process for a thermoplastic fiber composite member; FIG. 4 is a cross-sectional view in a manufacturing process of a bonded body according to the first embodiment, showing a convex portion forming process of convex portions that will become bonded portions; FIG. 5 is a cross-sectional view in a manufacturing process of a bonded body according to the first embodiment, showing a convex portion melting process of melting convex portions that will become bonded portions; FIG. 6 is a cross-sectional view in a manufacturing process of a bonded body according to the first embodiment, showing a bonded portion forming process of a bonded portion; FIG. 7 is a cross-sectional photograph of a sample of a bonded body according to the first embodiment; FIG. 8 is a cross-sectional view in a modified manufacturing process of a bonded body according to the first embodiment, showing a bonded portion forming process of a bonded portion; FIG. 9 is a cross-sectional view of a bonded body according to the second embodiment; FIG. 10 is a plan view of a bonded body according to the second embodiment in a separated state; FIG. 11 is a cross-sectional view in a manufacturing process of a bonded body according to the second embodiment, showing a convex portion forming process of convex portions that will become bonded portions; FIG. 12 is a cross-sectional view in a manufacturing process of a bonded body according to the second embodiment, showing a convex portion melting process of melting convex portions that will become bonded portions; FIG. 13 is a cross-sectional view in a manufacturing process of a bonded body according to the second embodiment, showing a bonded portion forming process of a bonded portion; 1. A cross-sectional view of a manufacturing process for a joined body according to a third embodiment. A cross-sectional view of a manufacturing process for a joined body according to a fourth embodiment. A cross-sectional view of a joined body according to a fifth embodiment. A plan view of a joined body according to a fifth embodiment in a separated state. A cross-sectional view of a manufacturing process for a joined body according to a fifth embodiment, showing a preparation process for a thermoplastic fiber composite member. A cross-sectional view of a manufacturing process for a joined body according to a fifth embodiment, showing a convex portion forming process for convex portions that will become joints. A cross-sectional view of a manufacturing process for a joined body according to a fifth embodiment, showing a lamination process for laminating thermoplastic fiber composite members. A cross-sectional view of a manufacturing process for a joined body according to a fifth embodiment, showing a joint forming process for joints. A cross-sectional photograph of a sample of a joined body according to a fifth embodiment. A cross-sectional view of a joined body according to a sixth embodiment. A plan view of a joined body according to a sixth embodiment in a separated state. A cross-sectional view of a manufacturing process for a joined body according to a sixth embodiment, showing a convex portion forming process for convex portions that will become joints. A cross-sectional view of a manufacturing process for a joined body according to a sixth embodiment, showing a lamination process for laminating thermoplastic fiber composite members.FIG. 10 is a cross-sectional view of a manufacturing process of a bonded body according to a sixth embodiment, showing a bond forming process of a bonded portion. FIG. 11 is a partial cross-sectional view of a manufacturing process of a bonded body according to the sixth embodiment, showing the formation of a portion of a bonded portion by a first ultrasonic welding. FIG. 12 is a partial cross-sectional view of a manufacturing process of a bonded body according to the sixth embodiment, showing the formation of a portion of a bonded portion by a second ultrasonic welding. FIG. 13 is a plan view of a bonded body according to a modified example of the sixth embodiment in a separated state. FIG. 14 is a cross-sectional view of a manufacturing process of a bonded body according to a seventh embodiment. FIG. 15 is a cross-sectional view of a manufacturing process of a bonded body according to an eighth embodiment. FIG. 16 is a graph showing test results of samples that are bonded bodies according to examples of the present disclosure.

[0014] The bonded structure and manufacturing method thereof according to the present disclosure will be described in detail below with reference to the drawings. The present disclosure is not limited to the content described below and can be modified as desired without departing from the spirit of the present disclosure. The drawings used in each embodiment are schematic illustrations of the bonded structure and its components according to the present disclosure. To facilitate understanding, some parts may be emphasized, enlarged, reduced, or omitted, and the scale and shape of each component may not be accurately represented. Furthermore, some numerical values ​​used in each embodiment are merely examples and can be modified as necessary. The same reference symbols are used to designate common components in the drawings.

[0015] First Embodiment (Configuration of Joined Body) First, the structure of the joined body of the present disclosure will be described with reference to Figs. 1 and 2. Fig. 1 is a cross-sectional view of the joined body according to this embodiment. In particular, Fig. 1 is a cross-sectional view along the thickness direction (stacking direction) of the joined body. Fig. 2 is a plan view of the joined body according to this embodiment in a separated state. In particular, Fig. 2 is a plan view of the first thermoplastic fiber member side in a state in which the joined body is separated at the joint.

[0016] 1 , the joined body 1 is a member formed by joining two laminated flat plate members of thermoplastic fiber composite material by melt processing. Specifically, the joined body 1 has a first thermoplastic fiber composite section 2, a second thermoplastic fiber composite section 3, a joint section 4, and an extension section 5. That is, in the joined body 1, the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3, which are made of thermoplastic fiber composite material, are joined via the joint section 4, and three intermittent joint sections 4 and three extension sections 5 extending around each of the joint sections 4 are interposed between the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3.

[0017] Here, the direction in which the first thermoplastic fiber composite portion 2 and the second thermoplastic fiber composite portion 3 are stacked (Z-axis direction) is referred to as the stacking direction, joining direction, or vertical direction. Furthermore, one direction perpendicular to the Z-axis direction (X-axis direction) is referred to as the horizontal direction or long side direction, and the other perpendicular direction (Y-axis direction) is referred to as the short side direction. These directions are also common to Figures 2 to 16 .

[0018] The first thermoplastic fiber composite section 2 includes a first matrix resin 21, which is a thermoplastic resin, and a plurality of first fiber members 22 mixed into the first matrix resin 21. The first matrix resin 21 may be, for example, polypropylene, polyethylene, acrylonitrile-butadiene-styrene copolymer, polyacrylic acid, or polyamide, or may be a thermoplastic engineering plastic. Examples of thermoplastic engineering plastics include aromatic polyetherketone (PAEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyphenylene sulfide (PPS), polyetherimide (PEI), or polyethersulfone (PES). The first fiber members 22 may be, for example, glass fiber, aramid fiber, or carbon fiber. That is, the first thermoplastic fiber composite section 2 may be a fiber-reinforced thermoplastic (FRTP) injection-molded using short glass fiber or carbon fiber. When glass fiber is used for the first fiber member 22, the first thermoplastic fiber composite part 2 is made of glass fiber reinforced thermoplastics (GFRTP), and when carbon fiber is used for the first fiber member 22, the first thermoplastic fiber composite part 2 is made of carbon fiber reinforced thermoplastics (CFRTP).

[0019] In FIG. 1 , three first fibrous members 22 are mixed into the first matrix resin 21, but the number is not limited to this. Of the three first fibrous members 22, the first fibrous member 22 located closest to the second thermoplastic fiber composite section 3 (i.e., located downward in the stacking direction, which is the Z-axis direction) is partially curved. Specifically, the first fibrous member 22 is curved near each of the three joints 4 and protrudes from the first matrix resin 21 (i.e., the first thermoplastic fiber composite section 2) toward the inside of the joints 4. In other words, the curved portion of the first fibrous member 22 is located inside the joints 4. This curvature of the first fibrous member 22 creates a common core material within the first matrix resin 21 and the joints 4, enabling the first matrix resin 21 and the joints 4 to be firmly bonded to each other.

[0020] Of the three first fiber members 22, the other two located away from the second thermoplastic fiber composite portion 3 are not curved in Figure 1, but may be curved like the curved first fiber members 22 described above.

[0021] The second thermoplastic fiber composite section 3 includes a second matrix resin 31, which is a thermoplastic resin, and a plurality of second fiber members 32 mixed into the second matrix resin 31. Like the first matrix resin 21, the second matrix resin 31 may be polypropylene, polyethylene, acrylonitrile-butadiene-styrene copolymer, polyacrylic acid, or polyamide, or may be a thermoplastic engineering plastic. Examples of thermoplastic engineering plastics include aromatic polyetherketone (PAEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyphenylene sulfide (PPS), polyetherimide (PEI), or polyethersulfone (PES). Similarly to the first fiber members 22, the second fiber members 32 may be glass fiber, aramid fiber, or carbon fiber. That is, the second thermoplastic fiber composite section may also be made of a fiber-reinforced thermoplastic plastic (FRTP) injection-molded using short glass fiber or carbon fiber. When glass fiber is used for the second fiber member 32, the second thermoplastic fiber composite part 3 is made of glass fiber reinforced thermoplastic plastic (GFRTP), and when carbon fiber is used for the second fiber member 32, the second thermoplastic fiber composite part 3 is made of carbon fiber reinforced thermoplastic plastic (CFRTP).

[0022] The second matrix resin 31 may be the same or different resin material as the first matrix resin 21. Similarly, the second fibrous members 32 may be the same or different fibers as the first fibrous members 22.

[0023] Each of the joints 4 is made of a thermoplastic resin. In this embodiment, the joints 4 are made of the same resin as the first matrix resin 21. The joints 4 are formed integrally with the first matrix resin 21 and the second matrix resin 31 by a melting process described below. Therefore, the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3 are joined via the joints 4.

[0024] In this embodiment, each of the bonding portions 4 protrudes toward the inside of the second thermoplastic fiber composite portion 3, and a portion of the bonding portion 4 penetrates into the second thermoplastic fiber composite portion 3. While the overall shape of the bonding portions 4 is shown as a cylinder in Figures 1 and 2, the bonding portions 4 may have various three-dimensional shapes, such as a hemisphere, a cone, a truncated cone, a prism, a pyramid, or a truncated pyramid. With this structure and shape, each of the bonding portions 4 interlocks with the second thermoplastic fiber composite portion 3. In other words, each of the bonding portions 4 functions as a wedge. This allows the second base resin 31 and the bonding portions 4 to be more firmly bonded to each other.

[0025] Here, the dimension (height) of the joint 4 in the stacking direction may be, for example, 0.1 mm to 5.0 mm, preferably 0.2 mm to 2.0 mm, and more preferably 0.6 mm to 1.0 mm. The dimension (height) of the portion interlocking with the second thermoplastic fiber composite portion 3 may be, for example, 0.02 mm to 0.5 mm, and preferably 0.1 mm to 0.3 mm. Note that, according to the test results described below, the joined body 1 has sufficient joining strength even without a portion interlocking with the second thermoplastic fiber composite portion 3. Therefore, it is assumed that the dimension of the portion interlocking with the second thermoplastic fiber composite portion 3 needs only to be 0 mm or greater. Additionally, the dimension (diameter) of the joint 4 in the horizontal direction can be adjusted as appropriate depending on the materials to be joined and the dimensions of the joined body, and may be, for example, 0.5 mm to 10.0 mm, or 1.0 mm to 5.0 mm. Here, if the dimensions of the joints 4 are too large, the degree of curvature of the first fibrous substance 22 may become too great, which may actually reduce the bonding strength. Therefore, the upper limit of the dimension of the joints 4 is preferably approximately 4.5 mm or less. This is because, as the dimensions of the joints 4 become larger, the curvature of the first fibrous substance 22 becomes greater, and the amount of fiber that penetrates into the joints 4 increases, which may actually reduce the bonding strength. On the other hand, since the presence of the joints 4 is thought to improve the bonding strength, the lower limit of the dimension of the joints 4 may be approximately 0.5 mm or less. In other words, if the dimensions of the joints 4 are made too small, the anchoring effect of the joints 4 is thought to be reduced. However, even if the dimensions of the joints 4 are made smaller to a certain extent (e.g., smaller than 1.5 mm), the bonding strength is thought to remain approximately constant without decreasing. By adopting such dimensions, it is possible to ensure a sufficient penetration amount of the joints 4 into the second thermoplastic fiber composite portion 3, thereby further increasing the bonding strength of the joints 4 to the second thermoplastic fiber composite portion 3. Furthermore, by adopting such dimensions, the degree of curvature of the first fibrous member 22 and the amount of insertion into the joint 4 can be sufficiently ensured.

[0026] In addition to the dimensions of the joints 4 described above, when a portion of the joints 4 interlocks with the second thermoplastic fiber composite portion 3, the horizontal (X-axis and Y-axis) proportion of the interlocking portion may be 20% to 80% of the total area of ​​the joints 4, and preferably 40% to 60%. When the entire joints 4 interlock with the second thermoplastic fiber composite portion 3, the horizontal (X-axis and Y-axis) proportion of the interlocking portion of the joints 4 may be 20% to 80% of the horizontal area occupied by the joints 4 and the stretched portions 5, and preferably 40% to 60%. Adjusting the amount of interlocking in this way ensures sufficient bonding strength of the joints 4 to the second thermoplastic fiber composite portion 3. In particular, in either case, setting the horizontal proportion to about 50% optimizes the balance between the amount of interlocking and the amount of stretching, thereby further increasing the bonding strength of the joints 4.

[0027] As described above, the first resin matrix 21 and the joints 4 are firmly joined by the curvature of the first fiber member 22, and the second resin matrix 31 and the joints 4 are firmly joined by the interlocking of the joints 4, thereby improving the joining strength of the joined body 1. In other words, the arrangement of the joints 4 and the penetration of the first fiber member 22 into the joints 4 as it curves can more firmly join the first thermoplastic fiber composite portion 2 and the second thermoplastic fiber composite portion 3 compared to general joining by only melting.

[0028] The extension portions 5 are made of a thermoplastic resin. In this embodiment, the joints 4 are made of the same resin as the first base resin 21 and the joints 4. As shown in Fig. 2, the extension portions 5 are formed by extending around the joints 4, with the joints 4 as the center. In other words, the extension portions 5 extend in a substantially annular shape around the joints 4, and extend between the first thermoplastic fiber composite portion 2 and the second thermoplastic fiber composite portion 3.

[0029] Unlike the joining section 4, the extension section 5 remains unjoined to the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3. That is, the extension section 5 does not contribute to the joining of the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3, but merely fills the gap between the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3. Providing such extension section 5 prevents exposure of the joining section 4 and further reduces the amount of exposure at the joining section between the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3. This reduces deterioration of the exposed section and improves the reliability of the joined body 1. While the first fiber members 22 may penetrate into the joining section 4, the extension section 5 does not contribute to the joining as described above, and therefore does not penetrate into the first fiber members 22 in this embodiment. However, depending on the condition of the first fiber members 22 and the amount of resin flow, the first fiber members 22 may penetrate into the extension section 5.

[0030] (Method for manufacturing a bonded body) Next, a method for manufacturing a bonded body 1 according to this embodiment will be described with reference to Figs. 1 to 7. Fig. 3 is a cross-sectional view of a manufacturing process for a bonded body 1 according to this embodiment, showing a step for preparing a thermoplastic fiber composite member. Fig. 4 is a cross-sectional view of a manufacturing process for a bonded body 1 according to this embodiment, showing a step for forming a convex portion that will become a bonded portion. Fig. 5 is a cross-sectional view of a manufacturing process for a bonded body 1 according to this embodiment, showing a step for melting a convex portion that will become a bonded portion. Fig. 6 is a cross-sectional view of a manufacturing process for a bonded body 1 according to this embodiment, showing a step for forming a bonded portion. Fig. 7 is a cross-sectional photograph of a sample of a bonded body 1 according to this embodiment.

[0031] First, a flat plate-shaped first thermoplastic fiber composite member 20 is prepared by mixing first fiber components 22 into a first thermoplastic matrix resin 21, and then a flat plate-shaped second thermoplastic fiber composite member 30 is prepared by mixing second fiber components 32 into a second thermoplastic matrix resin 31 (FIG. 3: preparation step). At the completion of the manufacturing process, the first thermoplastic fiber composite member 20 will become the first thermoplastic fiber composite part 2 described above, and the second thermoplastic fiber composite member 30 will become the second thermoplastic fiber composite part 3 described above.

[0032] Next, convex portions 40 made of the same resin as the first matrix resin 21 are intermittently formed on one surface 20a of the first thermoplastic fiber composite member 20 (see FIG. 4 : convex portion forming step). At the completion of the manufacturing process, the convex portions 40 will become the joints 4 described above. Therefore, in a plan view, the convex portions 40 are formed at the positions of the joints 4 as shown in FIG. 2 . The convex portions 40 may be formed by spot-applying a desired amount of thermoplastic resin to the area where the joints 4 are to be formed, as long as the convex portions 40 are formed at the positions of the joints 4 as shown in FIG. 2 . Alternatively, recesses may be formed in advance on the surface 20a where the resin for the convex portions 40 is to be applied, facilitating the application of the resin. In such a case, the recesses may remain in the first thermoplastic fiber composite portion 2 of the final joined body 1.

[0033] Here, the overall shape of the protrusion 40 can be any of various three-dimensional shapes such as a cylinder, a hemisphere, a cone, a truncated cone, a prism, a pyramid, a truncated pyramid, etc. In particular, shapes such as a hemisphere, a cone, and a pyramid make it easier to achieve the wedge function of the joint 4. The dimension (height) of the protrusion 40 may be, for example, 0.1 mm or more and 5.0 mm or less, preferably 0.2 mm or more and 1.5 mm or less, and more preferably 0.5 mm or more and 1.2 mm or less. Furthermore, the dimension (area) of the protrusion 40 in the horizontal direction is 0.2 mm or more and 0.5 mm or more and 1.2 mm or less. ２ 30mm or more ２ It may be less than 0.8 mm, preferably 0.8 mm ２ More than 20 mm ２ These dimensions are preferably set taking into consideration the melting of the protrusions 40, which will be described later. Therefore, the dimensions of the protrusions are determined based on the final dimensions of the joint 4 and the method and conditions of the melting process.

[0034] Next, the surface 20a of the first thermoplastic fiber composite member 20 and the surface 30a of the second thermoplastic fiber composite member 30 are placed opposite each other, and an infrared welding heater 60 is inserted between them ( FIG. 5 ). The heater 60 irradiates the protrusions 40 with infrared rays, heating and melting them. Then, as shown in FIG. 6 , pressure is applied from the surface 20b of the first thermoplastic fiber composite member 20 to bring the protrusions 40 into contact with and weld them to the second thermoplastic fiber composite member 30. As a result, the protrusions 40 are integrated and blended with the first thermoplastic fiber composite member 20 and the second thermoplastic fiber composite member 30. The protrusions 40 then function as the joint 4, joining the first thermoplastic fiber composite member 20 and the second thermoplastic fiber composite member 30 (joint forming process). In this embodiment, pressure is applied from the surface 20b of the first thermoplastic fiber composite member 20, but this is not limiting. Pressure may also be applied from the surface 30b of the second thermoplastic fiber composite member 30, or from both sides.

[0035] Here, because the protrusions 40 are pressed from the first thermoplastic fiber composite member 20 toward the second thermoplastic fiber composite member 30, the protrusions 40 are likely to be displaced into the second thermoplastic fiber composite member 30 in the melted portion. As a result, the protrusions 40 protrude toward the inside of the second thermoplastic fiber composite member 30 and engage with it.

[0036] Furthermore, such protrusion of the convex portions 40 causes the first base resin 21 to flow toward the convex portions 40 near the convex portions 40, bending the first fibrous members 22 near the convex portions 40. As the convex portions 40 melt, the first fibrous members 22 are displaced by the flow, causing the first fibrous members 22 to protrude and enter the inside of the convex portions 40 (i.e., the joints 4). In particular, in this embodiment, the convex portions 40 are scattered, so the first fibrous members 22 do not bend overall and protrude toward the second thermoplastic fiber composite member 30.

[0037] Furthermore, when the protrusions 40 melt, they spread to their surroundings due to pressure from the first thermoplastic fiber composite member 20. That is, the protrusions 40 stretch in the horizontal direction of the second thermoplastic fiber composite member 30. In this case, the portions of the protrusions 40 that stretch do not generate enough heat to cause the stretched resin to mix with the first thermoplastic fiber composite member 20 and the second thermoplastic fiber composite member 30, so the stretched portions are not bonded to the first thermoplastic fiber composite member 20 and the second thermoplastic fiber composite member 30, and form stretched portions 5.

[0038] Then, by performing a welding process using an infrared welder equipped with the heater 60 as described above, the protrusions 40 melt and penetrate, the first fiber component 22 bends, and the protrusions 40 extend, completing the joining of the first thermoplastic fiber composite member 20 and the second thermoplastic fiber composite member 30, thereby producing the joined body 1 as shown in Fig. 1. That is, the first thermoplastic fiber composite member 2 and the second thermoplastic fiber composite member 3 are joined by the joining portion 4, and an extension portion 5 is formed around the joining portion 4.

[0039] Here, a joined structure 1 according to this embodiment was actually manufactured, and the completed joined structure 1 was cut along the lamination direction (Z-axis direction), and a photograph of the cross section was taken of this photograph, which is shown in Figure 7. In Figure 7, it can be seen that a joint 4 and an extension section 5 are formed between the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3. It can also be seen that the overall shape of the joint 4 is conical, and that it protrudes toward and engages with the second thermoplastic fiber composite section 3. It can also be seen that the first fiber component 22, indicated by the dotted line, is partially curved, and that the curved portion enters the joint 4.

[0040] (Effects of the First Embodiment) In the present embodiment, each of the joints 4 engages with the second thermoplastic fiber composite portion 3 and functions as a wedge, thereby more firmly bonding the second base resin 31 to the joints 4. Furthermore, the curvature of the first fiber member 22 and its protrusion toward the joints 4 also firmly bond the first base resin 21 to the joints 4. This improves the bonding strength of the bonded body 1.

[0041] Furthermore, in this embodiment, the bonded portions 4 are formed so as to be intermittently and locally scattered rather than covering the entire surface of the first thermoplastic fiber composite portion 2. This makes it possible to reduce the amount of resin used as the bonding member, and also to reduce the cost of manufacturing the bonded body 1.

[0042] Furthermore, by forming an unbonded extension portion 5 between the first thermoplastic fiber composite portion 2 and the second thermoplastic fiber composite portion 3, the amount of exposure at the bonded portion between the first thermoplastic fiber composite portion 2 and the second thermoplastic fiber composite portion 3 is reduced, thereby improving the reliability of the bonded body 1.

[0043] (Variation of the First Embodiment) In the above-described embodiment, a portion of the first fiber component 22 protrudes so as to penetrate into the joint 4, but the first fiber component 22 may be curved to such an extent that it does not penetrate into the joint 4. Even in such a case, the joint 4 is interlocked with the second thermoplastic fiber composite component 30, so that the joining strength of the joined body 1 can be sufficiently ensured.

[0044] Furthermore, in the above-described embodiment, each of the bonding portions 4 interlocks with the second thermoplastic fiber composite portion 3, but the bonding portions 4 may be joined to the surface of the second thermoplastic fiber composite portion 3 and may not interlock with the second thermoplastic fiber composite portion 3. Even in such a case, since the material of the bonding portions 4 and the material of the base material of the first thermoplastic fiber composite portion 2 are the same, sufficient bonding strength for the bonded body 1 can be ensured.

[0045] Furthermore, in the above-described embodiment, in the manufacturing method of the bonded body 1, a single infrared welding process is performed using a relatively large heater 60. However, multiple infrared welding processes may be performed depending on the dimensions of the bonded body 1 and the heater 60. Even in such a case, since the protrusions 40 are formed intermittently and locally, once-melted protrusions 40 are not subjected to another infrared welding process, and damage to the bonded portion 4 is suppressed. Furthermore, it is possible to reduce temperature unevenness due to factors such as irradiation distance, and it is possible to maintain uniform bond strength at the bonded surface.

[0046] Furthermore, in the above-described embodiment, two first thermoplastic fiber composite members 20 and two second thermoplastic fiber composite members 30 were stacked and the two thermoplastic fiber composite members were joined, but three or more thermoplastic fiber composite members may also be stacked and joined.

[0047] In the manufacturing method of the bonded body 1 in the above-described embodiment, infrared rays are irradiated onto the protrusions 40 by the heater 60, but as shown in Fig. 8, infrared rays may also be irradiated onto the surface 30a of the second thermoplastic fiber composite member 30. By irradiating the second thermoplastic fiber composite member 30 with such infrared rays, the second thermoplastic fiber composite member 30 is also heated and melted, making it easier to bond the protrusions 40 and the second thermoplastic fiber composite member 30 together as a single unit.

[0048] Second Embodiment In the first embodiment, the arrangement and number of the joints 4 were adjusted so that the extension sections 5 extending from each joint 4 would not come into contact with each other, but the extension sections 5 may come into contact with each other to form a single extension region. Such a case will be described below as the second embodiment. Note that the same structures or materials as those in the first embodiment will be given the same names and detailed descriptions will be omitted, and differences will be described in detail.

[0049] (Configuration of the joined body) First, the structure of the joined body of this embodiment will be described with reference to Figs. 9 and 10. Fig. 9 is a cross-sectional view of the joined body according to this embodiment. In particular, Fig. 9 is a cross-sectional view along the thickness direction (stacking direction) of the joined body, similar to Fig. 1. Fig. 10 is a plan view of the joined body according to this embodiment in a separated state. In particular, Fig. 10 is a plan view of the first thermoplastic fiber member side in a state in which the joined body is separated at the joint.

[0050] As shown in Fig. 9, the joined body 101 has a first thermoplastic fiber composite portion 102, a second thermoplastic fiber composite portion 103, a bonded portion 104, and an extension portion 105. Like the joined body 1 according to the first embodiment, the joined body 101 also bonds a first thermoplastic fiber composite portion 102 and a second thermoplastic fiber composite portion 103 made of a thermoplastic fiber composite material. The joined body 101 differs from the joined body 1 according to the first embodiment in that there are more bonded portions 104 and the distance between the bonded portions 104 is shorter. Then, as shown in Fig. 10, resins extended from adjacent bonded portions 104 come into contact with each other, forming one extension portion 105.

[0051] The first thermoplastic fiber composite section 102 includes a first matrix resin 121, which is a thermoplastic resin, and a plurality of first fibrous members 122 mixed with the first matrix resin 121. Similarly, of the three first fibrous members 122, the first fibrous member 122 located closest to the second thermoplastic fiber composite section 103 protrudes from the first matrix resin 121 toward the inside of the joint 104. That is, the first fibrous member 122 protrudes in a larger portion than the first fibrous members 22 according to the first embodiment. This curvature of the first fibrous member 122 creates a common core material within the first matrix resin 121 and the joint 104, enabling a strong bond between the first matrix resin 121 and the joint 104. In particular, in this embodiment, the protruding portions are larger than in the first embodiment, resulting in a stronger bond.

[0052] The second thermoplastic fiber composite section 103 includes a second matrix resin 131, which is a thermoplastic resin, and a plurality of second fibrous members 132 mixed in the second matrix resin 131. The second matrix resin 131 may be the same resin material as the first matrix resin 121, or a different resin material. Similarly, the second fibrous members 132 may be the same fibers as the first fibrous members 122, or may be different fibers.

[0053] As in the first embodiment, each of the joints 104 is made of the same resin as the first base resin 121. Furthermore, the joints 104 are formed integrally with the first base resin 121 and the second base resin 131 by a melting process described below. Therefore, the first thermoplastic fiber composite portion 102 and the second thermoplastic fiber composite portion 103 are joined via the joints 104.

[0054] The shape, dimensions, and engagement amount of the joint 104 are the same as those of the joint 4 according to the first embodiment. Therefore, the wedge function is also the same, and the second base resin 131 and the joint 104 are more firmly joined. Furthermore, the degree of curvature of the first fiber component 122 and the amount of penetration into the joint 104 are sufficiently ensured, and the joining strength of the joint 104 to the first thermoplastic fiber composite component 102 is also sufficiently ensured.

[0055] The extension portions 105 are made of the same resin as the first base resin 121 and the joint portions 104. As can be seen from FIG. 10 , the extension portions 105 are formed integrally by the resin extending from the joint portion 104 around the center and contacting the resin extending from other nearby joint portions 104. That is, while the extension portions 105 were separate in the first embodiment, in this embodiment, the extension portions 105 are joined together to form a single extension region. The extension portions 105 fill the gaps between nearby joint portions 104, further reducing deterioration of the exposed portions and further improving the reliability of the joined body 101.

[0056] (Method for manufacturing a bonded body) Next, a method for manufacturing a bonded body 101 according to this embodiment will be described with reference to Figs. 9 to 12. Fig. 11 is a cross-sectional view of the manufacturing process of the bonded body 101 according to this embodiment, showing a convex portion forming step of convex portions that will become bonding portions. Fig. 12 is a cross-sectional view of the manufacturing process of the bonded body 101 according to this embodiment, showing a convex portion melting step of melting the convex portions that will become bonding portions. Fig. 13 is a cross-sectional view of the manufacturing process of the bonded body 101 according to this embodiment, showing a bonding portion forming step of bonding portions.

[0057] First, as in the first embodiment, a flat plate-shaped first thermoplastic fiber composite member 120 is prepared by mixing first fiber components 122 with a thermoplastic first matrix resin 121, and a flat plate-shaped second thermoplastic fiber composite member 130 is prepared by mixing second fiber components 132 with a thermoplastic second matrix resin 131 (preparation step). Note that, as in the first embodiment, at the completion of the manufacturing step, the first thermoplastic fiber composite member 120 becomes the first thermoplastic fiber composite portion 102 described above, and the second thermoplastic fiber composite member 130 becomes the second thermoplastic fiber composite portion 103 described above.

[0058] Next, using the same method as in the first embodiment, convex portions 140 made of the same resin as the first matrix resin 121 are intermittently formed on one surface 120a of the first thermoplastic fiber composite member 120 (FIG. 11: convex portion forming process). Here, at the time when the manufacturing process is completed, the convex portions 140 become the above-mentioned joints 104. Therefore, in a plan view, the convex portions 140 are formed at the positions of the joints 104 as shown in FIG. 10. Furthermore, the shape and dimensions of the convex portions 140 are the same as those of the convex portions 40 according to the first embodiment, with only the location of their placement being different.

[0059] Next, the surface 120a of the first thermoplastic fiber composite member 120 and the surface 130a of the second thermoplastic fiber composite member 130 are placed opposite each other, and a heater 160 for infrared welding is inserted between them ( FIG. 12 ). The heater 160 irradiates the protrusions 140 with infrared rays, heating and melting them. In this embodiment, a small heater 160 is used, and the welding process using infrared radiation is performed in two separate steps. Therefore, the heater 160 first irradiates half of the six protrusions 140 (one half on one side in the horizontal direction) with infrared rays, melting three of the protrusions 140. Next, the heater 160 moves horizontally (in the X-axis direction) and irradiates the remaining half of the six protrusions 140 (the opposite half in the horizontal direction) with infrared rays. The remaining three protrusions are then also melted.

[0060] 13 , pressure is applied from the surface 120b of the first thermoplastic fiber composite member 120 to bring the protrusions 140 into contact with and weld to the second thermoplastic fiber composite member 130. As a result, the protrusions 140 are integrated and blended with the first thermoplastic fiber composite member 120 and the second thermoplastic fiber composite member 130. The protrusions 140 then serve as the joints 104, joining the first thermoplastic fiber composite member 120 and the second thermoplastic fiber composite member 130 (joint forming process). As in the first embodiment, in this embodiment, pressure is applied from the surface 120b of the first thermoplastic fiber composite member 120. However, this is not limiting and pressure may be applied from the surface 130b of the second thermoplastic fiber composite member 130, or from both sides.

[0061] 9, the six protrusions 140 protrude toward and engage with the interior of the second thermoplastic fiber composite member 130, while the first fiber component 122 protrudes into and fits into the protrusions 140. Furthermore, the six protrusions 140 extend in the horizontal direction of the second thermoplastic fiber composite member 130, forming portions that become extensions 105.

[0062] As in the first embodiment, in this embodiment, the protrusions 140 are scattered, so the first fiber component 122 does not bend overall and protrude toward the second thermoplastic fiber composite component 130. Furthermore, the resin stretched from the protrusions 140 comes into contact with each other and forms an extension region, which is a single extension portion 105.

[0063] As in the first embodiment, the welding process using this infrared welder causes the protrusions 140 to melt and penetrate, the first fiber component 122 to bend, and the protrusions 140 to extend, completing the joining of the first thermoplastic fiber composite member 120 and the second thermoplastic fiber composite member 130, resulting in the production of a joined body 101 as shown in Fig. 9. That is, the first thermoplastic fiber composite member 102 and the second thermoplastic fiber composite member 103 are joined by the joining portion 104, and an extension portion 105 is formed around the joining portion 104.

[0064] (Effects of the Second Embodiment) Although the present embodiment differs in the number and arrangement of the bonded portions 104, it has the same configuration as the bonded body 1 according to the first embodiment. Therefore, for the same reasons as the bonded body 1, the bond strength of the bonded body 101 is improved. Also in this embodiment, the bonded portions 104 are not formed over the entire surface of the first thermoplastic fiber composite portion 102, but are formed so that the bonded portions 104 are intermittently and locally scattered. This reduces the amount of resin used as the bonding material, thereby reducing the cost of manufacturing the bonded body 1. Furthermore, the scattered protrusions 140 that become the bonded portions 104 prevent the protrusions 140 from being damaged even when multiple welding processes are performed using the infrared welding heater 160, thereby improving the reliability of the bonded body 101.

[0065] In this embodiment, particularly in the bonded body 101, the extension portion 105, which is a single expanded extension region, fills the gaps between adjacent bonded portions 104, thereby further reducing deterioration of the exposed portions and further improving the reliability of the bonded body 101.

[0066] (Modification of Second Embodiment) In the second embodiment described above, the extension portion 105 forms a rectangular extension region, but this is not limiting. For example, as shown in Fig. 14, the extension portion 105 may be formed to form an annular extension region. Here, Fig. 14 is a plan view of a bonded body 101 according to a modification of the second embodiment in a separated state.

[0067] In the manufacturing method of the bonded body 101 in the above-described embodiment, infrared rays are irradiated onto the protrusions 140 by the heater 160, but as in a modification of the first embodiment (FIG. 8), the infrared rays may also be irradiated onto the surface 130a of the second thermoplastic fiber composite member 130. By irradiating the second thermoplastic fiber composite member 130 with such infrared rays, the second thermoplastic fiber composite member 130 is also heated and melted, making it easier to bond the protrusions 140 and the second thermoplastic fiber composite member 130 together.

[0068] As shown in Figure 14, a large number of bonded portions 104' are formed in a scattered manner, and extended portions 105' (regions indicated by dotted lines) are formed surrounding the periphery of the bonded portions 104'. In the center of the extended portion 105', there is a region 107 where the resin that is the material of the extended portion 105' is not extended. The region 107 is a closed space surrounded by the extended portion 105', the first thermoplastic fiber composite member 120, and the second thermoplastic fiber composite member 130. In other words, the region 107 is an enclosed space.

[0069] By forming the extension portion 105' and the sealed region 107 in this manner, it is possible to manufacture a bonded body suitable for various applications. For example, the region 107 can be used to mount a sensor or other electronic component in the center of the bonded body so that it is not filled with resin and is not exposed to the outside air. Depending on the shape of the bonded body, it may be necessary to ensure bonding strength without providing a bonding portion or an extension portion, and this method can also be applied to such cases.

[0070] Third Embodiment In the first embodiment, the flat-plate-shaped joined body 1 was formed using flat first thermoplastic fiber composite members 20 and second thermoplastic fiber composite members 30, but the thermoplastic fiber composite members and the joined body may be curved. This case will be described as the third embodiment with reference to Figure 15. Figure 15 is a cross-sectional view of a manufacturing process for the joined body according to the third embodiment. Note that the same structures or materials as those in the first embodiment will be given the same names and detailed descriptions will be omitted, and differences will be described in detail.

[0071] 15 , in this embodiment, a wavy first thermoplastic fiber composite member 220 is prepared by mixing first fiber components 222 into a thermoplastic first matrix resin 221, and a wavy second thermoplastic fiber composite member 230 is prepared by mixing second fiber components 232 into a thermoplastic second matrix resin 231. Here, convex portions 240 made of the same resin as the first matrix resin 221 are intermittently formed on one surface 220a of the first thermoplastic fiber composite member 220. In particular, cone-shaped convex portions 240 are formed at the peaks and valleys of the wave pattern. The preparation process and convex portion formation process for each thermoplastic fiber composite member are performed in the same manner as in the first embodiment.

[0072] 15, the surface 220a of the first thermoplastic fiber composite member 220 and the surface 230a of the second thermoplastic fiber composite member 230 are placed opposite each other, and a heater 260 for infrared welding is inserted between them. The heater 260 irradiates infrared rays toward the protrusions 240, heating and melting the protrusions 240. In this embodiment, a small heater 260 is used that can perform welding on a single protrusion 240. This allows the area around the protrusion 240 to be locally heated by infrared radiation, and each protrusion 240 to be melted.

[0073] Thereafter, pressure is applied from the surface 220b side of the first thermoplastic fiber composite member 220 to bring the protrusions 240 into contact with and weld to the second thermoplastic fiber composite member 230. As a result, the protrusions 240 are integrated and blended with the first thermoplastic fiber composite member 220 and the second thermoplastic fiber composite member 230. The protrusions 240 then function as joining portions 204 to join the first thermoplastic fiber composite member 220 and the second thermoplastic fiber composite member 230. In this embodiment, too, pressure may be applied from the surface 230b side of the second thermoplastic fiber composite member 230, or from both sides.

[0074] Through the above steps, the first thermoplastic fiber composite material 220 becomes the first thermoplastic fiber composite portion 202, and the second thermoplastic fiber composite material 230 becomes the second thermoplastic fiber composite portion 203. Also in this embodiment, since the protrusions 240 are scattered, the first fiber composite material 222 does not bend overall and protrude toward the second thermoplastic fiber composite material 230.

[0075] As in the first embodiment, the welding process using this infrared welder causes the convex portions 240 to melt and penetrate, the first fiber component 222 to bend, and the convex portions 240 to extend, completing the joining of the first thermoplastic fiber composite member 220 and the second thermoplastic fiber composite member 230, resulting in the production of a joined body 201 as shown in the lower part of Figure 15. That is, the first thermoplastic fiber composite portion 202 and the second thermoplastic fiber composite portion 203 are joined by the joining portion 204, and an extension portion 205 is formed around the joining portion 204.

[0076] In this manner, in this embodiment, even for curved thermoplastic composite members, by forming and melting the convex portions 240 at desired joining locations, it is possible to achieve accurate and strong joining of the portions that require joining as the joined body 201. Furthermore, since the joints 204 are formed in a scattered manner, unnecessary joining can be reduced, and the cost of manufacturing the joined body 201 can also be reduced.

[0077] In the manufacturing method of the bonded body 201 in the above-described embodiment, infrared rays are irradiated onto the protrusions 240 by the heater 260, but as in the modified example of the first embodiment (FIG. 8), the infrared rays may also be irradiated onto the surface 230a of the second thermoplastic fiber composite member 230. By irradiating the second thermoplastic fiber composite member 230 with such infrared rays, the second thermoplastic fiber composite member 230 is also heated and melted, making it easier to bond the protrusions 240 and the second thermoplastic fiber composite member 230 together.

[0078] Fourth Embodiment In the third embodiment, the joined body 201 was formed using a wavy first thermoplastic fiber composite member 220 and a wavy second thermoplastic fiber composite member 230. However, each thermoplastic fiber composite member may have a bent shape. Furthermore, in the above-described embodiments, the convex portion serving as the joining portion was formed on only one of the thermoplastic fiber composite members. However, it may be formed on both of the thermoplastic fiber composite members. This case will be described as the fourth embodiment with reference to FIG. 16. Here, FIG. 16 is a cross-sectional view of a manufacturing process for a joined body according to this embodiment. Note that the same structures or materials as those in the first embodiment are designated by the same names and detailed descriptions are omitted, and differences will be described in detail.

[0079] As shown in Figure 16, in this embodiment, an L-shaped first thermoplastic fiber composite component 320 is prepared by mixing first fiber components 322 with a thermoplastic first matrix resin 321, and an L-shaped second thermoplastic fiber composite component 330 is prepared by mixing second fiber components 332 with a thermoplastic second matrix resin 331. A convex portion 340 made of the same resin as the first matrix resin 321 is formed on one surface 320a of the first thermoplastic fiber composite component 320, and two convex portions 341 made of the same resin as the second matrix resin 331 are formed on one surface 330a of the second thermoplastic fiber composite component 330. In particular, the convex portion 340 is formed at the bent portion of the first thermoplastic fiber composite component 320, and convex portions 341 are formed at both ends of the second thermoplastic fiber composite component 330. The preparation process and convex portion formation process for each thermoplastic fiber composite component are performed in the same manner as in the first embodiment. The convex portions 341 correspond to additional convex portions.

[0080] As shown in FIG. 16 , the surface 320a of the first thermoplastic fiber composite member 320 and the surface 330a of the second thermoplastic fiber composite member 330 are positioned opposite each other, and a heater 360 for infrared welding is inserted between them. The heater 360 sequentially irradiates the protrusions 340, 341 with infrared rays, thereby heating and melting the protrusions 340, 341. In this embodiment, a small heater 360 is used that can perform welding on a single protrusion 340, 341. This allows localized heating of the areas around the protrusions 340, 341 by infrared irradiation, thereby melting each of the protrusions 340, 341. While the heater 360 sequentially irradiates the protrusions 340, 341 with infrared rays in this embodiment, this is not a limitation. For example, the heater 360 may be enlarged within a range that allows insertion, or infrared rays may be irradiated from both sides of the heater 360, thereby simultaneously melting multiple protrusions.

[0081] Then, pressure is applied to bring the protrusions 340 into contact with and weld the second thermoplastic fiber composite member 330, and the protrusions 341 into contact with and weld the first thermoplastic fiber composite member 320. Since the welding process itself is the same in this embodiment, as in the first embodiment, the protrusions 340 (joining portions 304a) protrude toward and engage with the interior of the second thermoplastic fiber composite member 330, while the first fibrous component 322 protrudes into and fits within the protrusions 340. Furthermore, the protrusions 341 (joining portions 304b) protrude toward and engage with the interior of the first thermoplastic fiber composite member 320, while the second fibrous component 332 protrudes into and fits within the protrusions 341. Furthermore, the protrusions 340, 341 extend along the joining surfaces between the first thermoplastic fiber composite member 320 and the second thermoplastic fiber composite member 330, forming three extensions 305 centered on the protrusions 340, 341.

[0082] Through the above steps, the first thermoplastic fiber composite member 320 and the second thermoplastic fiber composite member 330 are joined together, with the protrusions 340 serving as joining portions 304a and 341 serving as joining portions 304b, so that the first thermoplastic fiber composite member 320 becomes the first thermoplastic fiber composite member 302, and the second thermoplastic fiber composite member 330 becomes the second thermoplastic fiber composite member 303. Also in this embodiment, because the protrusions 340, 341 are scattered, the first fiber composite member 322 does not curve overall and protrude toward the second thermoplastic fiber composite member 330, and the second fiber composite member 332 does not curve overall and protrude toward the first thermoplastic fiber composite member 320.

[0083] As in the first embodiment, the welding process using this infrared welder melts and penetrates the protrusions 340, 341, bends the first fibrous member 322 and the second fibrous member 332, and stretches the protrusions 340, 341, completing the joining of the first thermoplastic fiber composite member 320 and the second thermoplastic fiber composite member 330, resulting in the production of a joined body 301 as shown in the lower part of Figure 16. That is, the first thermoplastic fiber composite member 302 and the second thermoplastic fiber composite member 303 are joined by joints 304a, 304b, and extensions 305 are formed around each of the joints 304a, 304b. Here, joint 304b corresponds to the additional joint, and the extensions 305 formed around joint 304b correspond to the additional extensions.

[0084] In particular, in this embodiment, the joining portions 304a, 304b protrude toward and engage with the first thermoplastic fiber composite portion 302 and the second thermoplastic fiber composite portion 303 that constitute the joined body 301, thereby further increasing the joining strength of the joined body 301. Furthermore, in this embodiment, the fiber components of the first thermoplastic fiber composite member 320 and the second thermoplastic fiber composite member 330 that constitute the joined body 301 penetrate into the joining portions 304a, 304b, thereby further increasing the joining strength of the joined body 301.

[0085] Furthermore, in this embodiment, even for bent thermoplastic composite members, by forming and melting the protrusions 340, 341 at desired joining locations, it is possible to achieve accurate and strong joining of the portions that require joining as the joined body 301. In addition, since the joints 304a, 304b are formed in a scattered manner, unnecessary joining can be reduced, and the cost of manufacturing the joined body 301 can also be reduced.

[0086] In the above embodiment, the three extension sections 305 may be connected to each other to form one extension region, thereby reducing the amount of exposure of the first thermoplastic fiber composite section 302 and the second thermoplastic fiber composite section 303 and improving the reliability of the joined body 301.

[0087] In the manufacturing method of the bonded body 301 in the above-described embodiment, infrared rays are irradiated onto the protrusions 340, 341 by the heater 360, but as in a modification of the first embodiment (FIG. 8), the surface 330a of the second thermoplastic fiber composite member 330 and the surface 320a of the first thermoplastic fiber composite member 320 may also be irradiated. This infrared irradiation heats and melts the second thermoplastic fiber composite member 330 and the first thermoplastic fiber composite member 320, making it easier to integrate the protrusions 340 and the second thermoplastic fiber composite member 330 and to integrate and bond the protrusions 341 and the first thermoplastic fiber composite member 320.

[0088] Fifth Embodiment (Configuration of Joined Body) In the first to fourth embodiments, the thermoplastic composite members are joined by infrared welding, but they may also be joined by ultrasonic welding. Such cases will be described below as fifth to eighth embodiments. First, the structure of the joined body of the present disclosure will be described with reference to FIGS. 17 and 18. FIG. 17 is a cross-sectional view of the joined body according to this embodiment. In particular, FIG. 17 is a cross-sectional view taken along the thickness direction (stacking direction) of the joined body. Also, FIG. 18 is a plan view of the joined body according to this embodiment in a separated state. In particular, FIG. 18 is a plan view of the first thermoplastic fiber member side in a state in which the joined body is separated at the joint.

[0089] 17 , the joined body 1 is a member formed by joining two laminated flat plate members of thermoplastic fiber composite material by melt processing. Specifically, the joined body 1 has a first thermoplastic fiber composite section 2, a second thermoplastic fiber composite section 3, a joint section 4, and an extension section 5. That is, in the joined body 1, the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3, which are made of thermoplastic fiber composite material, are joined via the joint section 4, and three intermittent joint sections 4 and three extension sections 5 extending around each of the joint sections 4 are interposed between the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3.

[0090] Here, the direction in which the first thermoplastic fiber composite portion 2 and the second thermoplastic fiber composite portion 3 are stacked (Z-axis direction) is referred to as the stacking direction, joining direction, or vertical direction. Furthermore, one direction perpendicular to the Z-axis direction (X-axis direction) is referred to as the horizontal direction or long side direction, and the other perpendicular direction (Y-axis direction) is referred to as the short side direction. These directions are also common to Figures 17 to 33 .

[0091] The first thermoplastic fiber composite section 2 includes a first matrix resin 21, which is a thermoplastic resin, and a plurality of first fiber members 22 mixed into the first matrix resin 21. The first matrix resin 21 may be, for example, polypropylene, polyethylene, acrylonitrile-butadiene-styrene copolymer, polyacrylic acid, or polyamide, or may be a thermoplastic engineering plastic. Examples of thermoplastic engineering plastics include aromatic polyetherketone (PAEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyphenylene sulfide (PPS), polyetherimide (PEI), or polyethersulfone (PES). The first fiber members 22 may be, for example, glass fiber, aramid fiber, or carbon fiber. That is, the first thermoplastic fiber composite section 2 may be a fiber-reinforced thermoplastic (FRTP) injection-molded using short glass fiber or carbon fiber. When glass fiber is used for the first fiber member 22, the first thermoplastic fiber composite part 2 is made of glass fiber reinforced thermoplastics (GFRTP), and when carbon fiber is used for the first fiber member 22, the first thermoplastic fiber composite part 2 is made of carbon fiber reinforced thermoplastics (CFRTP).

[0092] 17 , three first fibrous members 22 are mixed into the first matrix resin 21, but the number is not limited to this. Of the three first fibrous members 22, the first fibrous member 22 located closest to the second thermoplastic fiber composite section 3 (i.e., located downward in the stacking direction, which is the Z-axis direction) is partially curved. Specifically, the first fibrous member 22 is curved near each of the three joints 4 and protrudes from the first matrix resin 21 (i.e., the first thermoplastic fiber composite section 2) toward the inside of the joints 4. In other words, the curved portion of the first fibrous member 22 is located inside the joints 4. This curvature of the first fibrous member 22 creates a common core material within the first matrix resin 21 and the joints 4, enabling the first matrix resin 21 and the joints 4 to be firmly bonded to each other.

[0093] Of the three first fiber members 22, the other two located away from the second thermoplastic fiber composite portion 3 are not curved in Figure 17, but may be curved like the curved first fiber members 22 described above.

[0094] The second thermoplastic fiber composite section 3 includes a second matrix resin 31, which is a thermoplastic resin, and a plurality of second fiber members 32 mixed into the second matrix resin 31. Like the first matrix resin 21, the second matrix resin 31 may be polypropylene, polyethylene, acrylonitrile-butadiene-styrene copolymer, polyacrylic acid, or polyamide, or may be a thermoplastic engineering plastic. Examples of thermoplastic engineering plastics include aromatic polyetherketone (PAEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyphenylene sulfide (PPS), polyetherimide (PEI), or polyethersulfone (PES). Similarly to the first fiber members 22, the second fiber members 32 may be glass fiber, aramid fiber, or carbon fiber. That is, the second thermoplastic fiber composite section may also be made of a fiber-reinforced thermoplastic plastic (FRTP) injection-molded using short glass fiber or carbon fiber. When glass fiber is used for the second fiber member 32, the second thermoplastic fiber composite part 3 is made of glass fiber reinforced thermoplastic plastic (GFRTP), and when carbon fiber is used for the second fiber member 32, the second thermoplastic fiber composite part 3 is made of carbon fiber reinforced thermoplastic plastic (CFRTP).

[0095] The second matrix resin 31 may be the same or different resin material as the first matrix resin 21. Similarly, the second fibrous members 32 may be the same or different fibers as the first fibrous members 22.

[0096] Each of the joints 4 is made of a thermoplastic resin. In this embodiment, the joints 4 are made of the same resin as the first matrix resin 21. The joints 4 are formed integrally with the first matrix resin 21 and the second matrix resin 31 by a melting process described below. Therefore, the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3 are joined via the joints 4.

[0097] In this embodiment, each of the bonding portions 4 protrudes toward the inside of the second thermoplastic fiber composite portion 3, and a portion of the bonding portion 4 penetrates into the second thermoplastic fiber composite portion 3. While the overall shape of the bonding portions 4 is shown as a cylinder in Figures 1 and 2, the bonding portions 4 may have various three-dimensional shapes, such as a hemisphere, a cone, a truncated cone, a prism, a pyramid, or a truncated pyramid. With this structure and shape, each of the bonding portions 4 interlocks with the second thermoplastic fiber composite portion 3. In other words, each of the bonding portions 4 functions as a wedge. This allows the second base resin 31 and the bonding portions 4 to be more firmly bonded to each other.

[0098] Here, the dimension (height) of the joint 4 in the stacking direction may be, for example, 0.1 mm to 5.0 mm, or 0.14 mm to 2.0 mm, or preferably 0.2 mm to 1.2 mm. The dimension (height) of the portion interlocking with the second thermoplastic fiber composite portion 3 may be, for example, 0.02 mm to 0.5 mm, or preferably 0.1 mm to 0.3 mm. In addition, the dimension (diameter) of the joint 4 in the horizontal direction can be appropriately adjusted depending on the materials to be joined and the dimensions of the joined body, but may be, for example, 0.5 mm to 10.0 mm, or preferably 1.0 mm to 5.0 mm. By adopting such dimensions, it is possible to ensure a sufficient penetration of the joint 4 into the second thermoplastic fiber composite portion 3, thereby further increasing the bonding strength of the joint 4 to the second thermoplastic fiber composite portion 3. Furthermore, by adopting such dimensions, it is possible to ensure a sufficient degree of curvature of the first fiber component 22 and a sufficient penetration amount of the first fiber component 22 into the joint 4.

[0099] In addition to the dimensions of the joints 4 described above, when the joints 4 interdigitate with the second thermoplastic fiber composite section 3, the horizontal (X-axis and Y-axis) proportion of the interdigitated portion may be 20% to 80% of the total area of ​​the joints 4, and preferably 40% to 60%. Furthermore, when the entire joints 4 interdigitate with the second thermoplastic fiber composite section 3, the horizontal (X-axis and Y-axis) proportion of the interdigitated portion of the joints 4 may be 20% to 80% of the horizontal area occupied by the joints 4 and the stretched sections 5, and preferably 40% to 60%. Adjusting the amount of interdigitation in this manner ensures sufficient bonding strength of the joints 4 to the second thermoplastic fiber composite section 3. In particular, in either case, setting the horizontal proportion to about 50% optimizes the balance between the amount of interdigitation and the amount of stretch, thereby further increasing the bonding strength of the joints 4.

[0100] As described above, the first resin matrix 21 and the joints 4 are firmly joined by the curvature of the first fiber member 22, and the second resin matrix 31 and the joints 4 are firmly joined by the interlocking of the joints 4, thereby improving the joining strength of the joined body 1. In other words, the arrangement of the joints 4 and the penetration of the first fiber member 22 into the joints 4 as it curves can more firmly join the first thermoplastic fiber composite portion 2 and the second thermoplastic fiber composite portion 3 compared to general joining by only melting.

[0101] The extension portions 5 are made of a thermoplastic resin. In this embodiment, the joints 4 are made of the same resin as the first base resin 21 and the joints 4. As shown in Fig. 2, the extension portions 5 are formed by extending around the joints 4, with the joints 4 as the center. In other words, the extension portions 5 extend in a substantially annular shape around the joints 4, and extend between the first thermoplastic fiber composite portion 2 and the second thermoplastic fiber composite portion 3.

[0102] Unlike the joining section 4, the extension section 5 remains unjoined to the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3. That is, the extension section 5 does not contribute to the joining of the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3, but merely fills the gap between the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3. Providing such extension section 5 prevents exposure of the joining section 4 and further reduces the amount of exposure at the joining section between the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3. This reduces deterioration of the exposed section and improves the reliability of the joined body 1. While the first fiber members 22 may penetrate into the joining section 4, the extension section 5 does not contribute to the joining as described above, and therefore does not penetrate into the first fiber members 22 in this embodiment. However, depending on the condition of the first fiber members 22 and the amount of resin flow, the first fiber members 22 may penetrate into the extension section 5.

[0103] (Method for manufacturing a bonded body) Next, a method for manufacturing a bonded body 1 according to this embodiment will be described with reference to Figures 17 to 22. Figure 19 is a cross-sectional view of a manufacturing process for a bonded body 1 according to this embodiment, showing a step for preparing a thermoplastic fiber composite material. Figure 20 is a cross-sectional view of a manufacturing process for a bonded body 1 according to this embodiment, showing a step for forming a convex portion that will become a bonded portion. Figure 21 is a cross-sectional view of a manufacturing process for a bonded body 1 according to this embodiment, showing a lamination step for laminating thermoplastic fiber composite materials. Figure 22 is a cross-sectional view of a manufacturing process for a bonded body 1 according to this embodiment, showing a step for forming a bonded portion. Furthermore, Figure 23 is a cross-sectional photograph of a sample of a bonded body 1 according to this embodiment.

[0104] First, a flat plate-shaped first thermoplastic fiber composite member 20 is prepared by mixing first fiber components 22 into a first thermoplastic matrix resin 21, and then a flat plate-shaped second thermoplastic fiber composite member 30 is prepared by mixing second fiber components 32 into a second thermoplastic matrix resin 31 (FIG. 19: preparation process). At the end of the manufacturing process, the first thermoplastic fiber composite member 20 will become the first thermoplastic fiber composite part 2 described above, and the second thermoplastic fiber composite member 30 will become the second thermoplastic fiber composite part 3 described above.

[0105] Next, convex portions 40 made of the same resin as the first matrix resin 21 are intermittently formed on one surface 20a of the first thermoplastic fiber composite member 20 (FIG. 20: convex portion forming step). At the completion of the manufacturing process, the convex portions 40 will become the joints 4 described above. Therefore, in a plan view, the convex portions 40 are formed at the positions of the joints 4 as shown in FIG. 18 . The convex portions 40 may be formed by spot-applying a desired amount of thermoplastic resin to the area where the joints 4 are to be formed, as long as the convex portions 40 are formed at the positions of the joints 4 as shown in FIG. 18 . Alternatively, recesses may be formed in advance on the surface 20a where the resin for the convex portions 40 is to be applied, facilitating the application of the resin. In such a case, the recesses may remain in the first thermoplastic fiber composite portion 2 of the final joined body 1.

[0106] Here, the overall shape of the protrusion 40 can be any of various three-dimensional shapes such as a cylinder, a hemisphere, a cone, a truncated cone, a prism, a pyramid, a truncated pyramid, etc. In particular, shapes such as a hemisphere, a cone, and a pyramid make it easier to achieve the wedge function of the joint 4. The dimension (height) of the protrusion 40 may be, for example, 0.1 mm or more and 5.0 mm or less, preferably 0.2 mm or more and 1.5 mm or less, and more preferably 0.5 mm or more and 1.2 mm or less. Furthermore, the dimension (area) of the protrusion 40 in the horizontal direction is 0.2 mm or more and 0.5 mm or more and 1.2 mm or less. ２ 30mm or more ２ It may be less than 0.8 mm, preferably 0.8 mm ２ More than 20 mm ２ These dimensions are preferably set taking into consideration the melting of the protrusions 40, which will be described later. Therefore, the dimensions of the protrusions are determined based on the final dimensions of the joint 4 and the method and conditions of the melting process.

[0107] Next, the surface 20a of the first thermoplastic fiber composite component 20 is placed opposite the surface 30a of the second thermoplastic fiber composite component 30 (FIG. 21), and the first thermoplastic fiber composite component 20 is layered on the second thermoplastic fiber composite component 30 so that the protrusions 40 are sandwiched between the first thermoplastic fiber composite component 20 and the second thermoplastic fiber composite component 30. Hereinafter, this layered state will also be referred to as a layered intermediate.

[0108] 22 , an ultrasonic welding horn 70 is pressed against the surface 20b of the first thermoplastic fiber composite member 20, and ultrasonic vibrations are applied to the laminated intermediate member. Because the first thermoplastic fiber composite member 20 and the protruding portions 40 are already integrated, the ultrasonic vibrations are transmitted to the protruding portions 40 via the first thermoplastic fiber composite member 20, generating frictional heat between the second thermoplastic fiber composite member 30 and the protruding portions 40. This causes the protruding portions 40 to melt and become integrated with the first thermoplastic fiber composite member 20 and the second thermoplastic fiber composite member 30, mixing them together. The protruding portions 40 then function as joints 4, joining the first thermoplastic fiber composite member 20 and the second thermoplastic fiber composite member 30 (joint formation process).

[0109] Here, because the protrusions 40 are pressed from the first thermoplastic fiber composite member 20 toward the second thermoplastic fiber composite member 30, the protrusions 40 are likely to be displaced into the second thermoplastic fiber composite member 30 in the areas where the frictional heat described above is generated. As a result, the protrusions 40 protrude toward the inside of the second thermoplastic fiber composite member 30 and engage with it.

[0110] Furthermore, such protrusion of the convex portions 40 causes the first base resin 21 to flow toward the convex portions 40 near the convex portions 40, bending the first fibrous members 22 near the convex portions 40. As the convex portions 40 melt, the first fibrous members 22 are displaced by the flow, causing the first fibrous members 22 to protrude and enter the inside of the convex portions 40 (i.e., the joints 4). In particular, in this embodiment, the convex portions 40 are scattered, so the first fibrous members 22 do not bend overall and protrude toward the second thermoplastic fiber composite member 30.

[0111] Furthermore, once the protrusions 40 melt, they spread to their surroundings due to the pressure of the horn 70. That is, the protrusions 40 stretch in the horizontal direction of the second thermoplastic fiber composite member 30. At this time, in the stretched portions of the protrusions 40, frictional heat sufficient to cause the stretched resin to mix with the first thermoplastic fiber composite member 20 and the second thermoplastic fiber composite member 30 is not generated, so the stretched portions are not bonded to the first thermoplastic fiber composite member 20 and the second thermoplastic fiber composite member 30, and form stretched portions 5.

[0112] Then, by performing a welding process using an ultrasonic welder equipped with the horn 70 as described above, the protrusions 40 melt and penetrate, the first fiber component 22 bends, and the protrusions 40 extend, completing the joining of the first thermoplastic fiber composite member 20 and the second thermoplastic fiber composite member 30, thereby producing the joined body 1 as shown in Fig. 1. That is, the first thermoplastic fiber composite member 2 and the second thermoplastic fiber composite member 3 are joined by the joint 4, and an extension 5 is formed around the periphery of the joint 4.

[0113] Here, a joined structure 1 according to this embodiment was actually manufactured, and the completed joined structure 1 was cut along the lamination direction, and a photograph of the cross section was taken, as shown in Figure 23. In Figure 23, it can be seen that a joint 4 and an extension section 5 are formed between the first thermoplastic fiber composite section 2 and the second thermoplastic fiber composite section 3. It can also be seen that the overall shape of the joint 4 is conical, and that it protrudes toward and engages with the second thermoplastic fiber composite section 3. It can also be seen that the first fiber component 22, indicated by the dotted line, is partially curved, and that the curved portion enters the joint 4.

[0114] (Effects of Fifth Embodiment) In this embodiment, each of the joints 4 engages with the second thermoplastic fiber composite portion 3 and functions as a wedge, thereby more firmly bonding the second base resin 31 to the joints 4. Furthermore, the curvature of the first fiber member 22 and its protrusion toward the joints 4 also firmly bond the first base resin 21 to the joints 4. This improves the bonding strength of the bonded body 1.

[0115] Furthermore, in this embodiment, the bonded portions 4 are formed so as to be intermittently and locally scattered rather than covering the entire surface of the first thermoplastic fiber composite portion 2. This makes it possible to reduce the amount of resin used as the bonding member, and also to reduce the cost of manufacturing the bonded body 1.

[0116] Furthermore, by forming an unbonded extension portion 5 between the first thermoplastic fiber composite portion 2 and the second thermoplastic fiber composite portion 3, the amount of exposure at the bonded portion between the first thermoplastic fiber composite portion 2 and the second thermoplastic fiber composite portion 3 is reduced, thereby improving the reliability of the bonded body 1.

[0117] (Variation of the Fifth Embodiment) In the above-described embodiment, a portion of the first fiber material 22 protrudes so as to penetrate into the joint 4, but it may be curved to such an extent that it does not penetrate into the joint 4. Even in such a case, the joint 4 is interlocked with the second thermoplastic fiber composite material 30, so that the joining strength of the joined body 1 can be sufficiently ensured.

[0118] Furthermore, in the above-described embodiment, each of the bonding portions 4 interlocks with the second thermoplastic fiber composite portion 3, but the bonding portions 4 may be joined to the surface of the second thermoplastic fiber composite portion 3 and may not interlock with the second thermoplastic fiber composite portion 3. Even in such a case, since the material of the bonding portions 4 and the material of the base material of the first thermoplastic fiber composite portion 2 are the same, sufficient bonding strength for the bonded body 1 can be ensured.

[0119] Furthermore, in the above-described embodiment, in the manufacturing method of the joined body 1, a single ultrasonic welding process is performed using a relatively large horn 70, but multiple ultrasonic welding processes may be performed depending on the dimensions of the joined body 1 and the horn 70. Even in such a case, since the protrusions 40 are formed intermittently and locally, once melted, the protrusions 40 are not subjected to a second ultrasonic welding process, and damage to the joint 4 is suppressed.

[0120] Furthermore, although ultrasonic welding is used for the welding process in the above-described embodiment, this is not limiting. For example, gas welding may be used for the welding process. Even in such a case, since the protrusions 40 are formed intermittently and locally, temperature variations due to factors such as irradiation distance can be reduced compared to when the resin forming the joining portion is formed in a strip or flat plate shape, and the joining strength at the joining surface can be maintained uniform.

[0121] In the above-described embodiment, two first thermoplastic fiber composite members 20 and two second thermoplastic fiber composite members 30 were stacked and the two thermoplastic fiber composite members were joined together, but three or more thermoplastic fiber composite members may also be stacked and joined together.

[0122] Sixth Embodiment In the fifth embodiment, the arrangement and number of the joints 4 were adjusted so that the extension sections 5 extending from each joint 4 would not come into contact with each other, but the extension sections 5 may come into contact with each other to form a single extension region. Such a case will be described below as the sixth embodiment. Note that the same structures or materials as those in the first embodiment will be given the same names and detailed descriptions will be omitted, and differences will be described in detail.

[0123] (Configuration of the joined body) First, the structure of the joined body of this embodiment will be described with reference to Figs. 24 and 25. Fig. 24 is a cross-sectional view of the joined body according to this embodiment. In particular, Fig. 24 is a cross-sectional view along the thickness direction (stacking direction) of the joined body, similar to Fig. 17. Fig. 25 is a plan view of the joined body according to this embodiment in a separated state. In particular, Fig. 25 is a plan view of the first thermoplastic fiber member side in a state in which the joined body is separated at the joint.

[0124] As shown in Figure 24, the joined body 101 has a first thermoplastic fiber composite portion 102, a second thermoplastic fiber composite portion 103, a bonded portion 104, and an extension portion 105. Like the joined body 1 according to the first embodiment, the joined body 101 also bonds a first thermoplastic fiber composite portion 102 and a second thermoplastic fiber composite portion 103 made of a thermoplastic fiber composite material. The joined body 101 differs from the joined body 1 according to the first embodiment in that there are more bonded portions 104 and the distance between the bonded portions 104 is shorter. Then, as shown in Figure 25, resins extended from adjacent bonded portions 104 come into contact with each other, forming one extension portion 105.

[0125] The first thermoplastic fiber composite section 102 includes a first matrix resin 121, which is a thermoplastic resin, and a plurality of first fibrous members 122 mixed with the first matrix resin 121. Similarly, of the three first fibrous members 122, the first fibrous member 122 located closest to the second thermoplastic fiber composite section 103 protrudes from the first matrix resin 121 toward the inside of the joint 104. That is, the first fibrous member 122 protrudes in a larger portion than the first fibrous members 22 according to the first embodiment. This curvature of the first fibrous member 122 creates a common core material within the first matrix resin 121 and the joint 104, enabling a strong bond between the first matrix resin 121 and the joint 104. In particular, in this embodiment, the protruding portions are larger than in the first embodiment, resulting in a stronger bond.

[0126] The second thermoplastic fiber composite section 103 includes a second matrix resin 131, which is a thermoplastic resin, and a plurality of second fibrous members 132 mixed in the second matrix resin 131. The second matrix resin 131 may be the same resin material as the first matrix resin 121, or a different resin material. Similarly, the second fibrous members 132 may be the same fibers as the first fibrous members 122, or may be different fibers.

[0127] As in the first embodiment, each of the joints 104 is made of the same resin as the first base resin 121. Furthermore, the joints 104 are formed integrally with the first base resin 121 and the second base resin 131 by a melting process described below. Therefore, the first thermoplastic fiber composite portion 102 and the second thermoplastic fiber composite portion 103 are joined via the joints 104.

[0128] The shape, dimensions, and engagement amount of the joint 104 are the same as those of the joint 4 according to the first embodiment. Therefore, the wedge function is also the same, and the second base resin 131 and the joint 104 are more firmly joined. Furthermore, the degree of curvature of the first fiber component 122 and the amount of penetration into the joint 104 are sufficiently ensured, and the joining strength of the joint 104 to the first thermoplastic fiber composite component 102 is also sufficiently ensured.

[0129] The extension portions 105 are made of the same resin as the first base resin 121 and the joint portions 104. As can be seen from FIG. 25 , the extension portions 105 are formed integrally by the resin extending from the joint portion 104 around the center and contacting the resin extending from other nearby joint portions 104. That is, while the extension portions 105 were separate in the fifth embodiment, in this embodiment, the extension portions 105 are joined together to form a single extension region. The extension portions 105 fill the gaps between nearby joint portions 104, further reducing deterioration of the exposed portions and further improving the reliability of the joined body 101.

[0130] (Method for manufacturing a joined body) Next, a method for manufacturing a joined body 101 according to this embodiment will be described with reference to Figures 24 to 29. Figure 26 is a cross-sectional view of a manufacturing process for the joined body 101 according to this embodiment, showing a convex portion forming step for forming convex portions that become joints. Figure 27 is a cross-sectional view of a manufacturing process for the joined body 101 according to this embodiment, showing a lamination step for laminating thermoplastic fiber composite members. Figure 28 is a cross-sectional view of a manufacturing process for the joined body 101 according to this embodiment, showing a joint portion forming step for forming joints. Figure 29 is a partial cross-sectional view of a manufacturing process for the joined body 101 according to this embodiment, showing the formation of some joints by a first ultrasonic welding. Figure 30 is a partial cross-sectional view of a manufacturing process for the joined body 101 according to this embodiment, showing the formation of the remaining joints by a second ultrasonic welding.

[0131] First, as in the fifth embodiment, a flat plate-shaped first thermoplastic fiber composite member 120 is prepared by mixing first fiber components 122 with a thermoplastic first matrix resin 121, and a flat plate-shaped second thermoplastic fiber composite member 130 is prepared by mixing second fiber components 132 with a thermoplastic second matrix resin 131 (preparation step). As in the first embodiment, at the completion of the manufacturing step, the first thermoplastic fiber composite member 120 becomes the first thermoplastic fiber composite portion 102 described above, and the second thermoplastic fiber composite member 130 becomes the second thermoplastic fiber composite portion 103 described above.

[0132] Next, using a method similar to that of the fifth embodiment, convex portions 140 made of the same resin as the first matrix resin 121 are intermittently formed on one surface 120a of the first thermoplastic fiber composite member 120 (Fig. 26: convex portion forming process). Here, at the time when the manufacturing process is completed, the convex portions 140 become the above-mentioned joints 104. Therefore, in a plan view, the convex portions 140 are formed at the positions of the joints 104 as shown in Fig. 25. Furthermore, the shape and dimensions of the convex portions 140 are the same as those of the convex portions 40 according to the first embodiment, with only the location of their arrangement being different.

[0133] Next, the surface 120a of the first thermoplastic fiber composite material 120 is placed opposite the surface 130a of the second thermoplastic fiber composite material 130 (Figure 27), and the first thermoplastic fiber composite material 120 is stacked on the second thermoplastic fiber composite material 130 so that the convex portion 140 is sandwiched between the first thermoplastic fiber composite material 120 and the second thermoplastic fiber composite material 130.

[0134] Next, as shown in Figure 28, an ultrasonic welding horn 170 is pressed against the surface 120b of the first thermoplastic fiber composite member 120, and ultrasonic vibrations are applied to the laminated intermediate member. In this embodiment, a small horn 170 is used, and the ultrasonic vibration welding process is performed in two stages. To achieve this, the horn 170 is first pressed against half (one half on one horizontal side) of the six protrusions 140. Then, ultrasonic vibrations are transmitted to three of the protrusions 140, melting them. Because the welding process itself is the same, as in the fifth embodiment, the three protrusions 140 protrude into the second thermoplastic fiber composite member 130 and engage with each other, while the first fiber component 122 protrudes into and penetrates the protrusions 140 (Figure 29). Furthermore, the protrusions 140 extend horizontally in the second thermoplastic fiber composite member 130, forming a portion that will become part of the extension 105 upon completion of manufacturing.

[0135] Next, as shown in Figure 30, a horn 170 is pressed against the remaining half (the half opposite the horizontal direction) of the six protrusions 140. Ultrasonic vibrations are then transmitted to the remaining three protrusions 140, causing these three protrusions 140 to melt. As with the above protrusions 140, these three protrusions 140 protrude toward the interior of the second thermoplastic fiber composite member 130 and engage with each other, while the first fiber component 122 protrudes into and penetrates these protrusions 140. Furthermore, the remaining three protrusions 140 extend in the horizontal direction of the second thermoplastic fiber composite member 130, forming portions that will become part of the extensions 105.

[0136] Through the above steps, the protrusions 140 serve as the joints 104, joining the first thermoplastic fiber composite material 120 and the second thermoplastic fiber composite material 130 (joint forming step). Also in this embodiment, the protrusions 140 are scattered, so the first fiber material 122 does not bend overall and protrude toward the second thermoplastic fiber composite material 130. Furthermore, the resin stretched from the protrusions 140 comes into contact with each other and forms an extension region, which is a single extension portion 105.

[0137] As in the fifth embodiment, the welding process using this ultrasonic welder causes the protrusions 140 to melt and penetrate, the first fiber component 122 to bend, and the protrusions 140 to extend, completing the joining of the first thermoplastic fiber composite member 120 and the second thermoplastic fiber composite member 130, and producing a joined body 101 as shown in Fig. 24. That is, the first thermoplastic fiber composite member 102 and the second thermoplastic fiber composite member 103 are joined by the joining portion 104, and an extension portion 105 is formed around the joining portion 104.

[0138] (Effects of the Sixth Embodiment) Although the sixth embodiment differs in the number and location of the bonded portions 104, it has the same configuration as the bonded body 1 according to the first embodiment. Therefore, for the same reasons as the bonded body 1, the bond strength of the bonded body 101 is improved. Furthermore, in the present embodiment, the bonded portions 104 are formed so as to be intermittently and locally scattered rather than over the entire surface of the first thermoplastic fiber composite portion 102. This reduces the amount of resin used as the bonding material, thereby reducing the cost of manufacturing the bonded body 1. Furthermore, the scattered presence of the protruding portions 140 that become the bonded portions 104 prevents the protruding portions 140 from being damaged even when multiple welding processes are performed using the ultrasonic welding horn 170, thereby improving the reliability of the bonded body 101.

[0139] In this embodiment, particularly in the bonded body 101, the extension portion 105, which is a single expanded extension region, fills the gaps between adjacent bonded portions 104, thereby further reducing deterioration of the exposed portions and further improving the reliability of the bonded body 101.

[0140] (Modification of Sixth Embodiment) In the sixth embodiment described above, the extending portion 105 forms a rectangular extending region, but this is not limiting. For example, as shown in Fig. 31 , the extending portion 105 may be formed to form an annular extending region. Here, Fig. 31 is a plan view of a bonded body 101 according to a modification of the sixth embodiment in a separated state.

[0141] As shown in Figure 31, a large number of bonded portions 104' are formed in a scattered manner, and extension portions 105' (areas indicated by dotted lines) are formed surrounding the periphery of the bonded portions 104'. In the center of the extension portions 105', there is an area 107 where the resin that is the material of the extension portions 105' is not extended. The area 107 is a closed space surrounded by the extension portions 105', the first thermoplastic fiber composite member 120, and the second thermoplastic fiber composite member 130. In other words, the area 107 is an enclosed space.

[0142] By forming the extension portion 105' and the sealed region 107 in this manner, it is possible to manufacture a bonded body suitable for various applications. For example, the region 107 can be used to mount a sensor or other electronic component in the center of the bonded body so that it is not filled with resin and is not exposed to the outside air. Depending on the shape of the bonded body, it may be necessary to ensure bonding strength without providing a bonding portion or an extension portion, and this method can also be applied to such cases.

[0143] Seventh Embodiment In the fifth embodiment, the flat-plate-shaped joined body 1 was formed using flat first thermoplastic fiber composite members 20 and second thermoplastic fiber composite members 30, but the thermoplastic fiber composite members and the joined body may be curved. This case will be described as the third embodiment with reference to Figure 32. Figure 32 is a cross-sectional view of a manufacturing process for a joined body according to the seventh embodiment. Note that the same structures or materials as those in the fifth embodiment will be given the same names and detailed descriptions will be omitted, and differences will be described in detail.

[0144] 32 , in this embodiment, a wavy first thermoplastic fiber composite member 220 is prepared by mixing first fiber components 222 into a thermoplastic first matrix resin 221, and a wavy second thermoplastic fiber composite member 230 is prepared by mixing second fiber components 232 into a thermoplastic second matrix resin 231. Here, convex portions 240 made of the same resin as the first matrix resin 221 are intermittently formed on one surface 220a of the first thermoplastic fiber composite member 220. In particular, cone-shaped convex portions 240 are formed at the peaks and valleys of the wave pattern. The preparation process and convex portion formation process for each thermoplastic fiber composite member are performed in the same manner as in the first embodiment.

[0145] Furthermore, as shown in Figure 32, the first thermoplastic fiber composite member 220 is stacked on the second thermoplastic fiber composite member 230 so that the surface 220a of the first thermoplastic fiber composite member 220 faces the surface 230a of the second thermoplastic fiber composite member 230, and the convex portion 240 is sandwiched between the first thermoplastic fiber composite member 220 and the second thermoplastic fiber composite member 230.

[0146] Then, an ultrasonic welding horn 270 is pressed against the surface 220b of the first thermoplastic fiber composite member 220, and ultrasonic vibrations are applied to the laminated intermediate body. In this embodiment, a small horn 270 is used that can perform welding on a single protrusion 240. This allows the area around the protrusion 240 to be locally heated by ultrasonic vibrations, melting each protrusion 240. Furthermore, because the welding process itself is the same as in the first embodiment, the protrusions 240 (joint portions 204) protrude toward and engage with the interior of the second thermoplastic fiber composite member 230, while the first fiber component 222 protrudes and penetrates into the protrusions 240, as in the first embodiment. Furthermore, the protrusions 240 extend along the wavy shape of the second thermoplastic fiber composite member 230, and extension portions 205 are formed around each protrusion 240.

[0147] Through the above steps, the first thermoplastic fiber composite member 220 and the second thermoplastic fiber composite member 230 are joined together using the protruding portions 240 as joining portions 204, with the first thermoplastic fiber composite member 220 becoming the first thermoplastic fiber composite portion 202 and the second thermoplastic fiber composite member 230 becoming the second thermoplastic fiber composite portion 203. Also in this embodiment, since the protruding portions 240 are scattered throughout, the first fiber composite member 222 does not curve overall and protrude toward the second thermoplastic fiber composite member 230.

[0148] As in the fifth embodiment, the welding process using this ultrasonic welder causes the convex portions 240 to melt and penetrate, the first fiber component 222 to bend, and the convex portions 240 to extend, completing the joining of the first thermoplastic fiber composite member 220 and the second thermoplastic fiber composite member 230, and producing a joined body 201 as shown in the lower part of Figure 32. That is, the first thermoplastic fiber composite portion 202 and the second thermoplastic fiber composite portion 203 are joined by the joining portion 204, and an extension portion 205 is formed around the joining portion 204.

[0149] In this manner, in this embodiment, even for curved thermoplastic composite members, by forming and melting the convex portions 240 at desired joining locations, it is possible to achieve accurate and strong joining of the portions that require joining as the joined body 201. Furthermore, since the joints 204 are formed in a scattered manner, unnecessary joining can be reduced, and the cost of manufacturing the joined body 201 can also be reduced.

[0150] Eighth Embodiment In the seventh embodiment, the joined body 201 was formed using a wavy first thermoplastic fiber composite member 220 and a wavy second thermoplastic fiber composite member 230. However, each thermoplastic fiber composite member may have a bent shape. Furthermore, in the above-described embodiments, the convex portion serving as the joining portion was formed on only one of the thermoplastic fiber composite members. However, it may be formed on both of the thermoplastic fiber composite members. This case will be described as the fourth embodiment with reference to FIG. 33. Here, FIG. 33 is a cross-sectional view of a manufacturing process for a joined body according to the eighth embodiment. Note that the same structures or materials as those in the fifth embodiment are designated by the same names and detailed descriptions are omitted, and differences will be described in detail.

[0151] As shown in Figure 33, in this embodiment, an L-shaped first thermoplastic fiber composite component 320 is prepared by mixing first fiber components 322 with a thermoplastic first matrix resin 321, and an L-shaped second thermoplastic fiber composite component 330 is prepared by mixing second fiber components 332 with a thermoplastic second matrix resin 331. A convex portion 340 made of the same resin as the first matrix resin 321 is formed on one surface 320a of the first thermoplastic fiber composite component 320, and two convex portions 341 made of the same resin as the second matrix resin 331 are formed on one surface 330a of the second thermoplastic fiber composite component 330. In particular, the convex portion 340 is formed at the bent portion of the first thermoplastic fiber composite component 320, and convex portions 341 are formed at both ends of the second thermoplastic fiber composite component 330. The preparation process and convex portion formation process for each thermoplastic fiber composite component are performed in the same manner as in the first embodiment. The convex portions 341 correspond to additional convex portions.

[0152] Furthermore, as shown in Figure 33, the first thermoplastic fiber composite member 320 is stacked on the second thermoplastic fiber composite member 330 so that the surface 320a of the first thermoplastic fiber composite member 320 faces the surface 330a of the second thermoplastic fiber composite member 330, and the convex portions 340, 341 are sandwiched between the first thermoplastic fiber composite member 320 and the second thermoplastic fiber composite member 330.

[0153] Then, an ultrasonic welding horn 370 is pressed against the surface 320b of the first thermoplastic fiber composite member 320 and the surface 330b of the second thermoplastic fiber composite member 330, sequentially applying ultrasonic vibrations to predetermined locations of the laminated intermediate body. In this embodiment, a small horn 370 is used that can perform welding on a single protrusion 340, 341. This allows localized heating of the area around the protrusion 340, 341 by ultrasonic vibrations, thereby melting each of the protrusions 340, 341. Furthermore, because the welding process itself is the same, as in the first embodiment, the protrusion 340 (joint portion 304a) protrudes toward and engages with the interior of the second thermoplastic fiber composite member 330, while the first fiber component 322 protrudes into and penetrates the interior of the protrusion 340. Furthermore, the convex portion 341 (joining portion 304b) protrudes toward the inside of the first thermoplastic fiber composite member 320 and engages with it, while the second fiber component 332 protrudes into and fits into the convex portion 341. Furthermore, the convex portions 340, 341 extend along the joining surface between the first thermoplastic fiber composite member 320 and the second thermoplastic fiber composite member 330, and three extension portions 305 are formed with the convex portions 340, 341 at the center.

[0154] Through the above steps, the first thermoplastic fiber composite member 320 and the second thermoplastic fiber composite member 330 are joined together, with the protrusions 340 serving as joining portions 304a and 341 serving as joining portions 304b, so that the first thermoplastic fiber composite member 320 becomes the first thermoplastic fiber composite member 302, and the second thermoplastic fiber composite member 330 becomes the second thermoplastic fiber composite member 303. Also in this embodiment, because the protrusions 340, 341 are scattered, the first fiber composite member 322 does not curve overall and protrude toward the second thermoplastic fiber composite member 330, and the second fiber composite member 332 does not curve overall and protrude toward the first thermoplastic fiber composite member 320.

[0155] As in the fifth embodiment, the welding process using this ultrasonic welder melts and penetrates the protrusions 340, 341, bends the first fibrous member 322 and the second fibrous member 332, and stretches the protrusions 340, 341, completing the joining of the first thermoplastic fiber composite member 320 and the second thermoplastic fiber composite member 330, resulting in the production of a joined body 301 as shown in the lower part of Figure 33. That is, the first thermoplastic fiber composite member 302 and the second thermoplastic fiber composite member 303 are joined by joints 304a, 304b, and extensions 305 are formed around each of the joints 304a, 304b. Here, joint 304b corresponds to the additional joint, and the extensions 305 formed around joint 304b correspond to the additional extensions.

[0156] In particular, in this embodiment, the joining portions 304a, 304b protrude toward and engage with the first thermoplastic fiber composite portion 302 and the second thermoplastic fiber composite portion 303 that constitute the joined body 301, thereby further increasing the joining strength of the joined body 301. Furthermore, in this embodiment, the fiber components of the first thermoplastic fiber composite member 320 and the second thermoplastic fiber composite member 330 that constitute the joined body 301 penetrate into the joining portions 304a, 304b, thereby further increasing the joining strength of the joined body 301.

[0157] Furthermore, in this embodiment, even for bent thermoplastic composite members, by forming and melting the protrusions 340, 341 at desired joining locations, it is possible to achieve accurate and strong joining of the portions that require joining as the joined body 301. In addition, since the joints 304a, 304b are formed in a scattered manner, unnecessary joining can be reduced, and the cost of manufacturing the joined body 301 can also be reduced.

[0158] In the above embodiment, the three extension sections 305 may be connected to each other to form one extension region, thereby reducing the amount of exposure of the first thermoplastic fiber composite section 302 and the second thermoplastic fiber composite section 303 and improving the reliability of the joined body 301.

[0159] <Test Results of Samples> Next, test results of samples of joined bodies that are examples of the present disclosure will be described with reference to FIG. 34 . Here, FIG. 34 is a graph showing test results of samples of joined bodies that are examples of the present disclosure. FIG. 34 shows the bond strength (welding strength) of joined bodies with different bond depths, with the horizontal axis representing the bond depth (mm) of the joined body and the vertical axis representing the bond strength (arbitrary units). Note that the bond strength of each sample in FIG. 34 was calculated based on a sample with sufficient bond strength as a sample and the sample with the lowest bond strength.

[0160] The sample bonded structure was formed by bonding two test pieces (thermoplastic fiber composite members) using an ultrasonic welding machine. One of the test pieces had a conical protrusion, which served as the bonding site, and the two test pieces were bonded via the protrusion. In other words, this sample corresponds to the bonded structure 1 in the fifth embodiment described above. The ultrasonic welding machine used was manufactured by Dukane Japan, and the output was set to 2600 W and the frequency to 20 kHz. The bond strength of each sample was measured by a tensile shear test using a Shimadzu universal testing machine. The test conditions were a sampling rate of 50 ms and a test speed of 1 mm / min.

[0161] Next, as can be seen from Figure 34, when the occlusal depth of the joint was increased from 0 mm to 0.17 mm, the bond strength improved as the occlusal depth increased, as shown by the dotted line in the graph. In other words, it is thought that the anchor effect of the joint was exerted.

[0162] On the other hand, it was also found that the bond strength when the bond depth was 0 mm was not significantly reduced compared to the bond strength of the sample with a bond depth of 0.17 mm. In other words, although the bond strength was greater when there was occlusion at the bond, it was considered that the strength of the bonded body was sufficient even without occlusion. In other words, it was found that the two test pieces were sufficiently bonded due to the presence of the bond.

[0163] <Embodiments of the present disclosure> A first embodiment of the present disclosure includes a first thermoplastic fiber composite portion in which a first fiber member is mixed with a first thermoplastic matrix resin, a second thermoplastic fiber composite portion in which a second fiber member is mixed with a second thermoplastic matrix resin, a joint portion joining the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion, and an extension portion extending around the joint portion and between the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion when the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion are not joined, and the joint portion is a joined body made of the same resin as the first matrix resin.

[0164] In this way, by forming the bonded portion intermittently rather than over the entire surface of the first thermoplastic fiber composite portion, the amount of thermoplastic resin used for the bonded portion can be reduced, thereby reducing the cost of manufacturing the bonded body. Furthermore, by forming a non-bonded extension portion between the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion, the amount of exposed material at the bonded portion between the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion is reduced, thereby improving the reliability of the bonded body.

[0165] In a second embodiment of the present disclosure, in the first embodiment, the joint portion protrudes toward the inside of the second thermoplastic fiber composite portion and engages with the second thermoplastic fiber composite portion, thereby interlocking with the second thermoplastic fiber composite portion and functioning as a wedge, thereby more firmly joining the second base resin and the joint portion.

[0166] In a third embodiment of the present disclosure, in the first or second embodiment, the first fiber component is curved near the joint and protrudes from the first thermoplastic fiber composite toward the inside of the joint, thereby providing a common core material for the joint and the first matrix resin, thereby firmly joining the first matrix resin and the joint.

[0167] In a fourth embodiment of the present disclosure, in any of the first to third embodiments, a plurality of the bonded portions are provided, and the extension portions extending from the bonded portions are in contact with each other to fill gaps between the bonded portions, thereby reducing the exposed surface area at the bonded portion between the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion and improving the reliability of the bonded structure.

[0168] A fifth embodiment of the present disclosure is any of the first to fourth embodiments, in which the plurality of extensions are in contact with each other to form an annular extension region, whereby in the joined body, the extensions, which are a single extended extension region, fill gaps between adjacent joined bodies, thereby further reducing deterioration of exposed portions and further improving the reliability of the joined body.

[0169] A sixth embodiment of the present disclosure is any of the first to fifth embodiments, further comprising: an additional bonding portion made of the same resin as the second matrix resin, protruding toward the interior of the first thermoplastic fiber composite portion to engage with it; and an additional extension portion extending around the additional bonding portion and between the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion when the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion are not bonded to each other. This allows the bonding portion to penetrate into each of the bonded thermoplastic fiber composite portions and each fiber component of the thermoplastic fiber composite portion to penetrate into the bonding portion, thereby further increasing the bonding strength of the bonded body.

[0170] In a seventh embodiment of the present disclosure, in any of the first to sixth embodiments, the first thermoplastic fiber-composite portion and the second thermoplastic fiber-composite portion are made of flat or curved members, which allows the shape of the joined body to be appropriately changed depending on the application and requirements.

[0171] In an eighth embodiment of the present disclosure, in any of the first to seventh embodiments, the bonded portion has a dimension of 0.1 mm to 5.0 mm in the stacking direction of the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion, and a dimension of 0.5 mm to 10.0 mm in the direction perpendicular to the stacking direction. This ensures a sufficient penetration of the bonded portion into the second thermoplastic fiber composite portion, thereby further increasing the bonding strength of the bonded portion to the second thermoplastic fiber composite portion. Furthermore, the degree of curvature of the first fiber component and the penetration of the first fiber component into the bonded portion can be sufficiently ensured.

[0172] A ninth embodiment of the present disclosure is any of the first to eighth embodiments, wherein the horizontal proportion of the portion of the joint that interlocks with the second thermoplastic fiber composite portion is 20% to 80% of the total, thereby making it possible to adjust the amount of interlocking of the joint with the second thermoplastic fiber composite portion and to ensure sufficient bonding strength of the joint with the second thermoplastic fiber composite portion.

[0173] A tenth embodiment of the present disclosure is a method for manufacturing a bonded body, comprising: a preparation step of preparing a first thermoplastic fiber composite member having a first fiber component mixed in a first thermoplastic matrix resin, and a second thermoplastic fiber composite member having a second fiber component mixed in a second thermoplastic matrix resin; a convex portion forming step of forming a convex portion made of the same resin as the first matrix resin on the surface of the first thermoplastic fiber composite member; and a joint forming step of melting the convex portion while the second thermoplastic fiber composite member is stacked on the convex portion forming surface of the first thermoplastic fiber composite member to form a joint joining the first thermoplastic fiber composite member and the second thermoplastic fiber composite member, wherein in the joint forming step, the convex portion is extended in a direction perpendicular to the stacking direction of the second thermoplastic fiber composite member, forming an extension portion that is not joined to the first thermoplastic fiber composite member and extends between the first thermoplastic fiber composite member and the second thermoplastic fiber composite member.

[0174] In this way, since the bonded portion is formed intermittently rather than over the entire surface of the first thermoplastic fiber composite portion, the amount of thermoplastic resin used for the bonded portion can be reduced, thereby reducing the cost of manufacturing the bonded body. Furthermore, since a non-bonded extension portion is formed between the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion, the exposed surface area at the bonded portion between the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion is reduced, thereby improving the reliability of the bonded body.

[0175] An eleventh embodiment of the present disclosure is the tenth embodiment, wherein in the joint forming step, the convex portion protrudes toward the inside of the second thermoplastic fiber composite material and engages with it, thereby interlocking the joint with the second thermoplastic fiber composite material and functioning as a wedge, thereby more firmly joining the second base resin and the joint.

[0176] A twelfth embodiment of the present disclosure is the tenth or eleventh embodiment, wherein in the joint forming step, the first fiber component is curved near the protrusion and protrudes from the first thermoplastic fiber composite component toward the inside of the protrusion, thereby providing a common core material for the joint and the first matrix resin, thereby firmly joining the first matrix resin and the joint.

[0177] A thirteenth embodiment of the present disclosure is any of the tenth to twelfth embodiments, in which the convex portion forming step forms a plurality of convex portions, and the joint forming step causes a plurality of extension portions extending from the plurality of convex portions to contact each other and fill gaps between the joints, thereby reducing the amount of exposure at the joints between the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion and improving the reliability of the joint.

[0178] A fourteenth embodiment of the present disclosure is any of the tenth to thirteenth embodiments, wherein in the bond forming step, the plurality of extensions contact each other to form an annular extension region, whereby in the bonded body, the extension, which is a single extended extension region, fills gaps between adjacent bonded bodies, thereby further reducing deterioration of exposed portions and further improving the reliability of the bonded body.

[0179] A fifteenth embodiment of the present disclosure is any of the tenth to fourteenth embodiments, in which, in the convex portion forming step, additional convex portions made of the same resin as the second matrix resin are formed on the surface of the second thermoplastic fiber composite member, and, in the joint portion forming step, the additional convex portions are protruded toward the interior of the first thermoplastic fiber composite member and interlocked to form additional joint portions, and the additional convex portions are extended in a direction perpendicular to the lamination direction of the first thermoplastic fiber composite member to form additional extension portions that are not joined to the first thermoplastic fiber composite member and extend between the first thermoplastic fiber composite member and the second thermoplastic fiber composite member. This allows the joint portions to penetrate into each of the joined thermoplastic fiber composite members and each fiber component of the thermoplastic fiber composite members to penetrate into the joint portions, thereby further increasing the joint strength of the joined body.

[0180] REFERENCE SIGNS LIST 1 Bonded body 2 First thermoplastic fiber composite section 3 Second thermoplastic fiber composite section 4 Bonded section 5 Extension section 20 First thermoplastic fiber composite member 21 First matrix resin 22 First fiber member 30 Second thermoplastic fiber composite member 31 Second matrix resin 32 Second fiber member 40 Convex section 60 Horn 304b Additional bonded section 305 Additional extension section 341 Additional convex section

Claims

1. A bonded body comprising: a first thermoplastic fiber composite part in which a first fiber component is mixed with a first thermoplastic matrix resin; a second thermoplastic fiber composite part in which a second fiber component is mixed with a second thermoplastic matrix resin; a joint part joining the first thermoplastic fiber composite part and the second thermoplastic fiber composite part; and an extension part extending between the first thermoplastic fiber composite part and the second thermoplastic fiber composite part, the extension part being centered on the joint part and extending around the joint part when the first thermoplastic fiber composite part and the second thermoplastic fiber composite part are not joined; wherein the joint part is made of the same resin as the first matrix resin.

2. The joined body according to claim 1, wherein the joining portion projects toward the inside of the second thermoplastic fiber composite portion and engages with the second thermoplastic fiber composite portion.

3. The joined body according to claim 1, wherein the first fiber member is curved in the vicinity of the joint and protrudes from the first thermoplastic fiber composite portion toward the inside of the joint.

4. The joined body according to claim 1, which has a plurality of said joints, and wherein the plurality of said extension portions extending from each of said joints are in contact with each other to fill gaps between said joints.

5. The assembly of claim 4, wherein a plurality of said extensions contact each other to form an annular extension region.

6. A joined body as described in claim 1, comprising an additional joint portion made of the same resin as the second base resin, protruding toward the inside of the first thermoplastic fiber composite portion and engaging therewith, and an additional extension portion that, when the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion are not joined, extends around the additional joint portion with the additional joint portion as its center and extends between the first thermoplastic fiber composite portion and the second thermoplastic fiber composite portion.

7. The joined body according to claim 1, wherein the first thermoplastic fiber composite part and the second thermoplastic fiber composite part are made of flat or curved members.

8. A joined body as described in claim 1, wherein the dimension of the joint in the stacking direction of the first thermoplastic fiber composite part and the second thermoplastic fiber composite part is 0.1 mm or more and 5.0 mm or less, and the dimension in the direction perpendicular to the stacking direction is 0.5 mm or more and 10.0 mm or less.

9. A joined body as described in claim 1, wherein the horizontal proportion of the portion of the joined portion that interlocks with the second thermoplastic fiber composite portion is 20% or more and 80% or less of the entire portion.

10. A method for manufacturing a joined body, comprising: a preparation step of preparing a first thermoplastic fiber composite member having a first fiber member mixed with a first thermoplastic matrix resin, and a second thermoplastic fiber composite member having a second fiber member mixed with a second thermoplastic matrix resin; a convex portion forming step of forming a convex portion made of the same resin as the first matrix resin on the surface of the first thermoplastic fiber composite member; and a joint forming step of melting the convex portion while the second thermoplastic fiber composite member is laminated on the convex portion forming surface of the first thermoplastic fiber composite member, to form a joint joining the first thermoplastic fiber composite member and the second thermoplastic fiber composite member, wherein in the joint forming step, the convex portion is extended in a direction perpendicular to the lamination direction of the second thermoplastic fiber composite member, to form an extension portion that is not bonded to the first thermoplastic fiber composite member and the second thermoplastic fiber composite member and extends between the first thermoplastic fiber composite member and the second thermoplastic fiber composite member.

11. A method for manufacturing a joined body as described in claim 10, wherein in the joint forming step, the convex portion is protruded toward the inside of the second thermoplastic fiber composite member and engaged therewith.

12. A method for manufacturing a joined body as described in claim 10, wherein in the joint forming process, the first fiber member is curved in the vicinity of the convex portion and protrudes from the first thermoplastic fiber composite member toward the inside of the convex portion.

13. A method for manufacturing a bonded body as described in claim 10, wherein in the convex portion forming step, a plurality of convex portions are formed, and in the joint portion forming step, a plurality of extension portions extending from each of the plurality of convex portions come into contact with each other to fill gaps between the joint portions.

14. The method for manufacturing a joint body according to claim 13, wherein in the joint forming step, the plurality of extensions come into contact with each other to form an annular extension region.

15. A method for manufacturing a joined body as described in claim 11, wherein in the convex portion forming step, an additional convex portion made of the same resin as the second matrix resin is formed on the surface of the second thermoplastic fiber composite member, and in the joint portion forming step, the additional convex portion is protruded toward the inside of the first thermoplastic fiber composite member and engaged to form an additional joint portion, and the additional convex portion is extended in a direction perpendicular to the lamination direction of the first thermoplastic fiber composite member to form an additional extension portion that is not joined to the first thermoplastic fiber composite member and the second thermoplastic fiber composite member and extends between the first thermoplastic fiber composite member and the second thermoplastic fiber composite member.

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