JP2013129159A - Manufacturing method of joined body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a joined body having favorable joining strength by using a simple method which heats and melts complex materials containing carbon fibers by applying a voltage to a resistance heating element.SOLUTION: In the manufacturing method of the joined body for heat-melting and joining two or more molded products which are molded of thermoplastic resin containing the carbon fibers and each of which has at least one surface, (i) the resistance heating element is arranged between surfaces (joining surfaces) of the mutually-opposing molded products via an insulation resin layer, and the joining surfaces are pressed, (ii) the arranged resistance heating element is applied with a voltage and made to generate heat, and (iii) the thermoplastic resin of the joining surfaces are heated and melted.

Description

  The present invention relates to a method for manufacturing a joined body composed of molded articles containing carbon fibers. More specifically, the present invention relates to a method of manufacturing a joined body by disposing a resistance heating element on a joining surface of two or more molded products containing carbon fibers and joining them by applying a voltage thereto.

  Plastics, especially thermoplastic resins, which can be molded in various ways, are indispensable materials for our daily lives. These molded bodies are often used as products in combination with other parts. In particular, a composite material containing reinforcing fibers such as carbon fibers has excellent physical properties from the viewpoint of high strength and light weight.

  In general, as a joining method of a molded product using the thermoplastic resin as a matrix (hereinafter, sometimes referred to as a thermoplastic resin reinforced fiber composite material, or simply a composite material), fastening with an adhesive, welding, bolt nut or rivet is used. Etc. are known. In particular, welding is a very advantageous joining method for a molded article made of a thermoplastic resin because the raw materials are integrated as they are, so that a high strength is obtained without an increase in weight due to joining. Various welding methods have been studied. For example, Patent Document 1 and Patent Document 2 describe a method in which a voltage is applied to a resistance heating element to heat and melt a resin for welding. Patent Document 1 describes a method of welding by sandwiching a resistance heating element between joint surfaces and applying a voltage thereto. Patent Document 2 describes a voltage application method.

  Further, Patent Literature 3 and Patent Literature 4 are methods for joining carbon fibers themselves as resistance heating elements. In Patent Document 3, a heating element mainly composed of carbon fiber is sandwiched between bonding surfaces of thermoplastic resin moldings to be welded facing each other, and a voltage is applied to the heating element while applying pressure with an appropriate force to generate heat. A method is described in which the resin on the joining surface is melted, and then the application of voltage is stopped to cool the resin, and an acrylic resin is welded together by passing an electric current through carbon fibers to be cured. Patent Document 4 describes a method of welding an acrylic resin by passing an electric current through carbon fibers.

JP 58-59050 A JP 2000-52434 A Japanese Patent Laid-Open No. 11-300836 JP 2002-46185 A

In order to join the thermoplastic resin carbon fiber composite material by welding, it is necessary to heat and heat at least a resin in the composite material by applying a voltage to the resistance heating element. Here, when carbon fiber is contained as a reinforcing fiber in the composite material as described in Patent Document 3 and Patent Document 4, since the carbon fiber is a material that easily conducts electricity, the resistance heating element There is a concern that the electricity energized to flow into the carbon fiber. Then, there is a problem that a sufficient current does not flow through the resistance heating element, and the resistance heating element is not sufficiently heated, so that it cannot be welded.
An object of the present invention is to provide a method for producing a bonded body having good bonding strength by a simple method in which a composite material containing carbon fibers is heated and melted by applying a voltage to a resistance heating element.

  As a result of intensive studies, the present inventors have provided a resin layer as an electrical insulating layer between the joining surface of the resistance heating element and at least two molded products molded of a thermoplastic resin containing carbon fiber. It has been found that a bonded body having good bonding strength is produced.

That is, the present invention is a method for manufacturing a joined body in which two or more molded products having at least one surface formed by thermoplastic resin containing carbon fibers are thermally welded and joined.
(I) disposing a resistance heating element via an insulating resin layer between the surfaces of the molded product facing each other (joint surface), and pressurizing the joint surface;
(Ii) A voltage is applied to the arranged resistance heating element to generate heat,
(Iii) A method for manufacturing a joined body in which a thermoplastic resin on the joint surface is heated and melted and thermally welded.

In the present invention, as described above, an insulating layer made of a resin that is the same as or compatible with the matrix resin contained in the composite material is provided between the resistance heating element and the composite material, and a voltage is applied to the resistance heating element. Pressure was applied to perform welding.
As a result, when the resistance heating element is energized at the bonding surface, electricity hardly flows to the carbon fibers in the composite material, and the resistance heating element can be heated uniformly. In particular, since carbon fiber is contained in the molded product, heat is transmitted over a wide range to the entire joint surface in a relatively short time. Therefore, the bonding area is large, and high bonding strength can be achieved efficiently.

Embodiments of the present invention will be described below.
[Molding]
The molded product used in the present invention is molded from a thermoplastic resin containing carbon fibers. That is, it is a thermoplastic resin composite material in which a thermoplastic resin is used as a matrix component and carbon fibers are contained therein. Such a molded article has at least one surface to be a bonding surface.

[Thermoplastic resin]
The thermoplastic resin constituting the composite material is not particularly limited. For example, polyamide, polycarbonate, polyoxymethylene, polyphenylene sulfide, polyphenylene ether, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polystyrene, poly Examples thereof include thermoplastic resins such as methyl methacrylate, AS resin, and ABS resin. Two of these may be used in combination.

[Carbon fiber]
In the present invention, since carbon fibers are used, a molded product having a light weight, high strength, and high rigidity can be obtained. The average fiber diameter is preferably 3 to 12 μm, more preferably 5 to 7 μm. Moreover, this carbon fiber may be used individually by 1 type, and may use together 2 or more types from which a diameter differs.
The form of the carbon fiber used here is not particularly limited, and may be a continuous fiber or a discontinuous fiber. In the case of continuous fibers, for example, a form such as a unidirectional substrate or a nonwoven fabric in which carbon fibers are aligned in a uniaxial direction can be mentioned, but this is not restrictive. Moreover, in the case of a discontinuous fiber, it does not specifically limit regarding fiber length.

The carbon fiber may be subjected to a surface treatment such as a treatment with a coupling agent, a treatment with a sizing agent, or an adhesion treatment of an additive. In most cases, those carbon fibers to which a sizing agent is attached are used. The adhesion amount of the sizing agent is preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the carbon fiber.
For example, when discontinuous carbon fibers are used, it is preferable that such carbon fibers are disposed so as to be isotropically randomly dispersed and overlapped. In this case, the fiber length is preferably 5 mm or more and 100 mm or less, more preferably more than 5 mm and less than 100 mm, and the upper limit of the average fiber length is preferably 50 mm. The reinforcing material used in the present invention may have an average fiber length in the above range, but the discontinuous fiber having a length of less than 5 mm or the discontinuous fiber exceeding 100 mm is a ratio of 20% by weight or less of the total carbon fiber. Although it may be included, since it may affect the bonding, it is preferable that it is not substantially included.

  The single yarn fineness of the carbon fiber is preferably 100 to 5,000 dtex, more preferably 1,000 to 2,000 dtex. Further, in the case of carbon fiber, a continuous fiber made of substantially untwisted yarn (strand) in which the number of filaments is bundled between 3,000 and 6,000, or a short fiber bundle formed by cutting the continuous fiber is used. .

[Ratio of thermoplastic resin to carbon fiber]
The blending ratio of the thermoplastic resin and the carbon fiber is preferably 50 to 1,000 parts by weight of the thermoplastic resin with respect to 100 parts by weight of the carbon fiber. More preferably, it is 50 to 400 parts by weight of the thermoplastic resin with respect to 100 parts by weight of the carbon fiber, and further preferably 50 to 100 parts by weight of the thermoplastic resin with respect to 100 parts by weight of the carbon fiber. By setting the ratio, the moldability of the molded product is good, and the finally obtained joined body has high mechanical strength.
The molded product according to the present invention may contain various additives within a range that does not impair the object of the present invention (for example, a range of 20% by weight or less). Examples of the additive include a flame retardant, a heat stabilizer, an ultraviolet absorber, a nucleating agent, and a plasticizer.
The carbon fiber volume content (Vf = 100 × carbon fiber volume / (carbon fiber volume + thermoplastic resin volume)) of the molded product is preferably 5% to 80%.

[Shape of molded product]
The shape of the molded product used in the present invention can be applied to various shapes including a six-sided structure such as a sheet and a rectangular parallelepiped. In the case of a planar body such as a plate, the thickness is, for example, in the range of 0.5 mm to 10 mm. The thickness is more preferably 1 to 8 mm. However, in order to join a plurality of molded products, the molded product needs to have a shape having at least one plane serving as a bonding surface. It is desirable that such a joining surface is basically free from irregularities and has good surface properties. Therefore, the surfaces other than the bonding surface may have various shapes. For example, a shape having a three-dimensional curved surface may be used.

[Production method of molded products]
The molded article in the present invention can be produced by a conventional method as long as it is molded from a thermoplastic resin containing carbon fibers. In particular, when trying to obtain a molded article with further improved mechanical strength according to the present invention, preferably the degree of carbon fiber opening is controlled, and a reinforcing fiber bundle consisting of a specific number or more and other opened carbon A molded article formed using a prepreg containing a specific ratio of fibers is desirable. That is, in the prepreg used in the present invention, the following formula (1)
Critical number of single yarns = 600 / D (1)
(Here, D is the average fiber diameter (μm) of the reinforcing fibers)
With respect to the carbon fiber bundle (A) composed of the number of critical single yarns or more defined in the above, it is preferable for the purpose of obtaining more excellent mechanical properties that the ratio with respect to the total amount of carbon fibers is 20 Vol% or more and 99 Vol% or less. In addition, in this prepreg, the fiber bundle comprised by the state of a single yarn or less than a critical single yarn number exists as carbon fibers other than a carbon fiber bundle (A). The ratio of the carbon fiber bundle (A) in the case of obtaining a molded body having further excellent mechanical properties is more preferably 30 Vol% or more and less than 90 Vol%, and further preferably 30 Vol% or more and less than 80 Vol%.

Further, the average number of fibers (N) in the carbon fiber bundle (A) composed of the number of critical single yarns or more is represented by the following formula (2).
0.7 × 10 ⁴ / D ² <N <1 × 10 ⁵ / D ² (2)
(Here, D is the average fiber diameter (μm) of the reinforcing fibers)
It is preferable to satisfy. The above formula (2) is expressed by the following formula (2 ′)
0.7 × 10 ⁴ / D ² <N <6.0 × 10 ⁴ / D ² (2 ′)
It is more preferable to satisfy.

When the average number of fibers (N) in the carbon fiber bundle (A) is 0.7 × 10 ⁴ / D ² or less, it is difficult to obtain a high fiber volume content (Vf). Further, in the case where the average number of fibers (N) in the carbon fiber bundle (A) is 6.0 × 10 ⁴ / D ² or more, particularly 1 × 10 ⁵ or more, a locally thick portion in a molded body which is a prepreg or a final product. This is likely to cause void formation.

  In addition, the said prepreg is a sheet | seat material for a molded object manufacture normally, and the thing within the range whose thickness is 0.1 mm-10 mm. Such a prepreg does not need to be completely impregnated with a thermoplastic resin, and an impregnation rate of 50% to 100% can be used. Preferably, the impregnation rate is 70% to 100%, and 90% An impregnation rate of ˜100% is more preferable. Here, the impregnation ratio can be obtained by setting the volume of the prepreg to 100%, obtaining the volume of air contained in the prepreg, and subtracting from the volume of the prepreg. A plurality of such prepregs can be used.

  Further, when the prepreg is disposed so as to be appropriately dispersed in the in-plane direction, the molded product has substantially no physical properties, for example, strength, elastic modulus, etc., and in-plane direction anisotropy. If the joint surface is parallel to the in-plane direction using such a molded product, the finally obtained joined body has excellent strength in one direction, which is advantageous depending on the application. Further, such a joined body may have a shape having a three-dimensional curved surface as a part or as a whole.

[Resistance heating element]
As the resistance heating element used in the present invention, as long as the temperature can be raised until the thermoplastic resin is melted by applying a voltage for a certain period of time, there is no limitation on the material, for example, metals such as iron and copper, stainless steel, Alloys such as nickel chrome, iron chrome, and iron nickel, and carbon fibers can be used. Two or more of these materials may be used in combination.

  The shape of the resistance heating element is not particularly limited as long as it is a molded body made of the above materials, and examples thereof include rod-shaped objects such as rods, wires, and wires, and plate-shaped objects such as foils and sheets. . Even in the case of a rod shape, it may be bent partially or entirely. Examples of the shape viewed from the cross section of the resistance heating element include a circle, a rectangle, and a polygon. The thickness (thickness) of the resistance heating element needs to be matched with the joint shape (shape of the joint (surface)), and is preferably 5 mm or less from the viewpoint of ease of handling. . Although there is no restriction | limiting in particular as a lower limit, 0.1 mm is preferable. About the length of a resistance heating element, what is necessary is just to match | combine with the length of a joint surface.

  Further, the resistance heating element can be appropriately selected depending on the size of the joint surface, and in the case of a rod shape, it may be one or plural. In particular, when carbon fiber is used as a resistance heating element, a number such as 24000, 12000, 3000 is used. When the resistance heating element is plate-shaped, one or more can be used depending on the size of the joint surface. The shape when viewed from above may be polygonal, circular, or elliptical.

[Shape of joint surface]
In the present invention, since it is possible to cope with a joint shape such as a complicated three-dimensional curved surface, there is no limitation on the shape of the joint surface. It is preferable to provide a groove or a recess for setting the body in advance. There are no particular restrictions on the shape of the groove or recess, but in order to obtain a joined body with good strength and appearance, the cross-sectional area of the groove or recess provided is insulated between the composite materials to be joined to the resistance heating element. It is preferably 20% to 200% of the cross-sectional area of an insulating resin layer described later provided as a layer.
In addition, as the shape of the joining surface, for example, when two molded products are joined, a quadrangular shape is preferable, but a circular shape, a parallelogram, or a rhombus may be used.

[Insulating resin layer]
In the present invention, pressure is applied in a state in which the resistance heating element is disposed between the surfaces (joint surfaces) where the plurality of molded products facing each other are joined (joint surfaces). Here, the insulating resin layer substantially prevents current from flowing through the plurality of molded articles when a voltage is applied to the resistance heating element. Thereby, the resistance heating element can be heated uniformly, and as a result, the thermoplastic resin in the vicinity of the joint surface of the molded product is uniformly heated and melted.
Here, examples of the resin forming the insulating resin layer include a thermoplastic resin and a thermosetting resin. As the thermoplastic resin, the same ones as described above can be used. Among these, it is preferable to use a thermoplastic resin that is the same as or similar to the molded product, or a compatible thermoplastic resin because a bonded body having excellent adhesion and excellent strength characteristics can be obtained.

The insulating resin layer in the present invention exists between the molded product and the resistance heating element so that the resistance heating element does not directly contact the molding product.
As such an insulating resin layer, for example, a layer made of a sheet having a thickness in the range of 0.1 mm to 5 mm, or a coating layer in which the resistance heating element is covered with the insulating resin having a thickness of 0.1 mm to 5 mm, for example. Can be mentioned. Furthermore, a sheet-like material composed of the insulating resin layer may be wound around the resistance heating element so as to be a layer disposed on the joint surface of the molded product. Two or more of these insulating resin layers may be used in combination.
The thickness of the insulating resin layer is preferably in the range of 0.1 mm to 5 mm. From the viewpoint of conforming to a complicated shape, a range of 0.1 mm to 2 mm is more preferable.

[Jointing procedure]
Although the preferable manufacturing method of the conjugate | zygote of this invention is demonstrated below, this invention is not limited to these.
Two or more molded articles that are carbon fiber composite materials to be joined are prepared. When a sheet is used as the insulating resin layer, the molded product, the sheet, the resistance heating element, the sheet, and the molded product are arranged and pressed in this order. In other words, the resistance heating element is sandwiched and held between the molded product and the sheet.
Further, when the resistance heating element is coated as the insulating resin layer, the resistance heating element can be arranged and pressed so as to be sandwiched between the joint surfaces between the two molded products.
The applied pressure at this time may be such that the sheet that forms the resistance heating element and the insulating resin layer does not move, but is, for example, 0.02 to 0.2 MPa.

Next, a voltage is applied across the resistance heating element. Although there is no restriction | limiting in the voltage to apply, The range of 10V to 400V is preferable. In order to obtain a joined body having good strength, it is preferable to uniformly heat the resistance heating element to a temperature suitable for welding. As a method for energizing, it is possible to repeat ON and OFF at a constant voltage. The voltage may be increased or decreased.
When the resistance heating element is heated to a temperature sufficient for welding, the pressure is applied again, and the pressure is maintained until the resistance heating element is sufficiently cooled. The applied pressure at this time is preferably 0.5 MPa or more per welding area. The upper limit depends on the size of the joined body, but is, for example, 100 MPa.

  Thus, according to the present invention, a metal, an alloy, or a carbon fiber is composed of two or more molded articles made of a thermoplastic resin containing reinforcing fibers, and an insulating resin layer is interposed between at least two molded articles. A joined body having a resistance heating element is obtained. Such a resistance heating element exists between two molded articles, and two or more molded articles exhibit good adhesiveness and are excellent in mechanical strength and rigidity.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these. The evaluation results are shown in Table 1.

[Evaluation method]
(Tensile test)
The obtained bonded body was subjected to a tensile shear test based on JISK6850 using an universal testing machine 5578 300 kN capacity floor type testing machine manufactured by Instron. The tensile speed was 1 mm / min.

[Reference Example 1]
(Creation of composite material 1)
Carbon fibers (Tenax STS40 manufactured by Toho Tenax, average fiber diameter 7 μm) cut to an average fiber length of 20 mm are randomly arranged so that the average basis weight is 540 g / m ² , the carbon fiber weight ratio is 52%, and the volume is 35%. A carbon fiber composite material having a matrix made of Unitika nylon 6 manufactured by Unitika Ltd. was prepared. The size of the composite material was 100 mm × 100 mm × thickness 1.6 mm.

(Creation of composite material 2)
In place of Unitika nylon 6 in the preparation of the composite material 1 described above, acid-modified polypropylene resin (Prime Polymer Prime Polypro J108M is 96% by weight, maleic anhydride-modified polypropylene (Toyobo Co., Ltd. Toyotac PMA1000P)) is 4% by weight. A composite material was prepared in the same manner as in Preparation 1 of the composite material, except that the mixture was mixed with a rotary blender.

[Reference Example 2]
(Joining method (1))
Two identical composite materials prepared based on Preparation 1 of the composite material of Reference Example 1 were prepared, and a stainless steel wire having a length of φ0.8 and a length of 120 mm was prepared as a resistance heating element. Both ends of the wire were sandwiched between the composite materials, and a sheet of nylon 6 having a thickness of 2 mm was sandwiched between the composite material and the wires as an insulating layer. At this time, the overlap margin of the composite material was 25 mm, and the size of the nylon 6 sheet sandwiched between the joints was 100 mm × 25 mm.
Then, a voltage of 100 V was applied to the wire for about 20 seconds to melt the matrix resin and the nylon 6 sheet in the composite material, and immediately after the energization was stopped, the joint was pressurized at 2 MPa. While maintaining the pressure for about 30 seconds, it was cooled to room temperature to obtain a joined body.

(Joining method (2))
Two identical composite materials prepared based on preparation 2 of the composite material of Reference Example 1 were prepared, and a stainless steel wire having a length of φ0.8 and a length of 120 mm was prepared as a resistance heating element. Both ends of the wire were sandwiched between the composite materials, and a polypropylene sheet having a thickness of 2 mm was sandwiched between the composite material and the wires as an insulating layer. At this time, the overlap margin of the composite material was 25 mm, and the size of the polypropylene sheet sandwiched between the joints was 100 mm × 25 mm.
Next, a voltage of 100 V was applied to the wire for about 18 seconds to melt the matrix resin and polypropylene sheets in the composite material, and immediately after the energization was stopped, the joint was pressurized at 2 MPa. While maintaining the pressure for about 30 seconds, it was cooled to room temperature to obtain a joined body.

[Reference Example 3: Joining Method]
(Joining method (3))
Two of the same composite materials prepared based on Preparation 1 of the composite material of Reference Example 1 were prepared, and a resistance heating element coated with the same nylon 6 (Unitika nylon 6 manufactured by Unitika Ltd.) as the matrix resin was prepared. At this time, the resistance heating element was a stainless wire of φ0.7 length 120 mm, and the coating thickness was 2 mm. The coated resin was peeled off at both ends of the coated resistance heating element over a length of 5 mm. Next, the both ends of the coated wire were sandwiched between the composite materials. At this time, the overlap margin of the composite material was set to 25 mm.
Next, a voltage of 100 V was applied to the wire for about 20 seconds to melt the nylon 6 covering the matrix resin and the resistance heating element in the composite material, and immediately after the energization was stopped, the joint was pressurized at 2 MPa. While maintaining the pressure for about 30 seconds, it was cooled to room temperature to obtain a joined body.

(Joining method (4))
Two identical composite materials prepared based on Preparation 2 of the composite material of Reference Example 1 were prepared, and a resistance heating element coated with the same polypropylene as the matrix resin (Prime Polymer Prime Polypro J108M) was prepared. At this time, the resistance heating element was a stainless wire of φ0.7 length 120 mm, and the coating thickness was 2 mm. The coated resin was peeled off at both ends of the coated resistance heating element over a length of 5 mm. Next, the both ends of the coated wire were sandwiched between the composite materials. At this time, the overlap margin of the composite material was set to 25 mm.
Next, a voltage of 100 V was applied to the wire for about 18 seconds to melt the polypropylene covering the matrix resin and the resistance heating element in the composite material, and immediately after the energization was stopped, the joint was pressurized at 2 MPa. While maintaining the pressure for about 30 seconds, it was cooled to room temperature to obtain a joined body.

[Reference Example 4: Joining Method]
Two of the same composite materials prepared based on Preparation 1 of the composite material of Reference Example 1 were prepared, and a resistance heating element coated with the same nylon 6 (Unitika nylon 6 manufactured by Unitika Ltd.) as the matrix resin was prepared. At this time, the resistance heating element was 120 mm long carbon fiber (Tenax STS40, 24K manufactured by Toho Tenax, average fiber diameter 7 μm), and the coating thickness was 2 mm. Further, the coated resin was peeled off at both ends of the coated carbon fiber over a length of 5 mm. Subsequently, the carbon fiber covered between the composite materials was sandwiched so that both ends would come out. At this time, the overlap margin of the composite material was set to 25 mm.
Next, a voltage of 100 V was applied to the carbon fibers for approximately 25 seconds to melt the matrix resin in the composite material and the nylon 6 covering the carbon fibers, and immediately after the energization was stopped, the joint was pressurized at 2 MPa. While maintaining the pressure for about 30 seconds, it was cooled to room temperature to obtain a joined body.

[Comparative Example 1]
(Joining)
Two identical composite materials prepared based on Preparation 1 of the composite material of Reference Example 1 were prepared, and a stainless steel wire having a φ0.7 length of 120 mm was prepared as a resistance heating element. The wire was sandwiched between the composite materials so that both ends would come out. At this time, the overlap margin of the composite material was set to 25 mm.
Next, a voltage of 100 V was applied to the wire for about 20 seconds, and immediately after the energization was stopped, the joint was pressurized at 2 MPa. While maintaining the pressure for about 30 seconds, it was cooled to room temperature.
(Evaluation)
In Comparative Example 1, a joined body could not be obtained. At this time, the state where the resin of the part which has arrange | positioned the wire was heated was not seen.

[Example 1]
(Joining)
Two identical composite materials prepared based on the composite material preparation 1 of Reference Example 1 were prepared, and a joined body was obtained based on the joining method 1 of Reference Example 2.
(Evaluation)
When the obtained bonded body was measured for tensile shear strength by the above evaluation method, the breaking load was 11.3 kN.

[Example 2]
(Joining)
Two identical composite materials prepared based on the composite material preparation 2 of Reference Example 1 were prepared, and a joined body was obtained based on the joining method 2 of Reference Example 2.
(Evaluation)
When the obtained bonded body was measured for tensile shear strength by the above evaluation method, the breaking load was 10.3 kN.

[Example 3]
(Joining)
Two identical composite materials prepared based on Preparation 1 of the composite material of Reference Example 1 were prepared, and a joined body was obtained based on the joining method 3 of Reference Example 3.
(Evaluation)
When the obtained bonded body was measured for tensile shear strength by the above evaluation method, the breaking load was 10.6 kN.

[Example 4]
(Joining)
Two identical composite materials prepared based on Preparation 2 of the composite material of Reference Example 1 were prepared, and a joined body was obtained based on the joining method 4 of Reference Example 3.
(Evaluation)
When the obtained bonded body was measured for tensile shear strength by the above evaluation method, the breaking load was 10.0 kN.

[Example 5]
(Joining)
Two identical composite materials prepared based on Preparation 1 of the composite material of Reference Example 1 were prepared, and a joined body was obtained based on Reference Example 4.
(Evaluation)
When the obtained bonded body was measured for tensile shear strength by the above evaluation method, the breaking load was 10.9 kN.

Claims (10)

A method for producing a joined body, which is formed of a thermoplastic resin containing carbon fiber and is formed by heat-welding and joining two or more molded articles having at least one surface,
(I) disposing a resistance heating element via an insulating resin layer between the surfaces of the molded product facing each other (joint surface), and pressurizing the joint surface;
(Ii) A voltage is applied to the arranged resistance heating element to generate heat,
(Iii) A method for manufacturing a joined body in which the thermoplastic resin on the joining surface is heated and melted and thermally welded.   The method for manufacturing a joined body according to claim 1, wherein the resistance heating element is a molded body made of a metal, an alloy, or carbon fiber.   The method for producing a joined body according to claim 1 or 2, wherein the insulating resin layer is made of an insulating resin that is the same as or compatible with the thermoplastic resin.   The method for manufacturing a joined body according to any one of claims 1 to 3, wherein the insulating resin layer is a sheet having a thickness in a range of 0.1 mm to 5 mm.   The method of manufacturing a joined body according to any one of claims 1 to 3, wherein the resistance heating element via the insulating resin layer is coated with an insulating resin having a thickness of 0.1 mm to 5 mm.   6. The carbon fiber volume content (Vf = 100 × carbon fiber volume / (carbon fiber volume + thermoplastic resin volume)) of the molded product is 5% to 80%. The manufacturing method of the conjugate | zygote in any one of.   The production of the joined body according to any one of claims 1 to 6, wherein the thermoplastic resin is present in the molded product in an amount of 50 to 1000 parts by weight with respect to 100 parts by weight of the carbon fiber. Method.   The method for producing a joined body according to any one of claims 1 to 7, wherein the carbon fibers are carbon fibers having an average fiber diameter of 3 µm to 12 µm.   The method for producing a joined body according to any one of claims 1 to 8, wherein an average fiber length of the carbon fibers is 5 mm to 100 mm.   The method for manufacturing a joined body according to claim 1, wherein at least one molded article has two parallel surfaces and is isotropic with respect to an in-plane direction of the surfaces.