Electrode for welding fiber reinforced plastic and welding method using the same

Abstract

The present invention addresses the problem of providing a welding electrode for fiber-reinforced plastics (FRP) capable of welding fiber-reinforced plastic components together, capable of welding joints of any shape, capable of being melted by heating means such as hot air using inexpensive equipment, and capable of achieving weld strength as a plastic product, as well as a welding method using the welding electrode for FRP. This problem is solved by the welding electrode for thermoplastic FRP and the welding method using the welding electrode for thermoplastic FRP. The welding electrode for thermoplastic FRP is a fiber-reinforced plastic welding electrode that fills the weld joint between FRP components and can be melted by heating means such as hot air or a hot plate. The mixture of fiber and thermoplastic resin is formed into a strip, and the fiber content is set to 1% to 35% by weight when the mixture is 100% by weight.

Description

Technical Field

[0001] This invention relates to fiber-reinforced plastic welding electrodes and welding methods using fiber-reinforced plastic welding electrodes in welding fiber-reinforced plastic components containing the same fibers, such as carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, modified polyphenylene ether fiber, and cellulose nanofiber. Background Technology

[0002] In the bonding methods of plastics containing fibers, there are generally mechanical methods such as fastening for plastics made of natural or synthetic resins after injection molding or machining, bonding methods using adhesives such as rubber-based adhesives, and welding methods using ultrasonic waves or friction. In the welding methods, the heat source can be a wave generated by ultrasonic waves, high frequency waves or lasers, a friction caused by frictional heat, or external heating using hot air or a hot plate.

[0003] Furthermore, welding of natural or synthetic resin plastics to each other generally involves using welding rods with the same composition as the plastics. While applying appropriate pressure to press the lower end of the welding rod against the joint surface, hot air is used as a heat source to melt the welding rod and fill it into the joint surface, thus advancing the welding process.

[0004] On the other hand, fiber-reinforced plastic components made of carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, modified polyphenylene ether fiber or cellulose nanofiber are generally fixed to each other by mechanical fixation using adhesives or fasteners, and welding is not implemented in practice.

[0005] As a method for welding carbon fiber reinforced plastics, Patent Document 1 discloses a laser welding method for fiber-reinforced composite materials. This method uses a solid-state laser with a wavelength of 532 nm to 1080 nm. Laser welding is performed simultaneously by filling the joint between carbon fiber reinforced plastics (CFRP) and each other or between CFRP and metal with welding filler and irradiating the welding filler with a laser beam to melt it. The welding filler contains less than 80% by weight of reinforcing material, based on 100% by weight of the welding material, in any one of thermoplastic resin, thermosetting resin, or a mixture of thermoplastic and thermosetting resins. The reinforcing material comprises one or more selected from the group consisting of reinforcing carbon fibers, reinforcing glass, and whiskers.

[0006] Patent document 2 discloses a seam welding method for welding two polyamide plastics using a primer, wherein the primer contains at least one polymer synthesized from at least one maleic anhydride or a maleic anhydride derivative.

[0007] Patent document 3 discloses a welding method for fiber-reinforced plastics, in which the resin in the welding part of the fiber-reinforced plastic is melted away to expose the reinforcing fibers, and other reinforcing fibers are filled into the exposed space of the fibers. Then, or after the fibers are welded together, molten resin is injected into the space and solidified to fix the fiber-reinforced plastic.

[0008] Patent document 4 discloses a welding method for resin, glass fiber reinforced plastic (GFRP), carbon fiber reinforced plastic (CFRP), or carbon materials. A first welding material is supplied from a welding material supply pipe located at the nozzle. Gas is supplied from a gas supply section to a hot air supply pipe containing a built-in ceramic heater to heat the gas into hot air. The hot air is then sent to a hot air outlet pipe connected to the hot air supply pipe and introduced into a hot air inlet pipe located at the nozzle and connected to the hot air outlet pipe. The first welding material is heated and softened by spraying the hot air from the front end to the rear end along the length direction using a roller located at the nozzle. Next, after the roller is returned to the front end of the first welding material, a second welding material is supplied on the first welding material in a manner that partially overlaps each other in the width direction. While the overlapping portion of the first welding material and the second welding material is melted by spraying hot air, pressure is applied in the length direction from the front end to the rear end of the overlapping portion of the first welding material and the second welding material by the roller provided in the nozzle to press the overlapping portion of the first welding material and the second welding material together. Cooling air is supplied from the cooling pipe provided in the nozzle to cool the overlapping portion of the first welding material and the second welding material.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent No. 5523260

[0012] Patent Document 2: Japanese Patent Publication No. 2018-535850

[0013] Patent Document 3: Japanese Patent Publication No. 51-1266

[0014] Patent Document 4: Japanese Patent No. 5883235 Summary of the Invention

[0015] The problem the invention aims to solve

[0016] The invention in Patent Document 1 involves melting the welding filler by irradiating it with a laser beam. The laser beam typically irradiates a spot smaller than 1 mm. Therefore, as described in Patent Document 1, there are problems such as the need to process the bevel shape with high dimensional accuracy by laser processing, the need to make the bevel shape into a zipper-like inlay joint rather than a straight joint, the problem of expensive laser welding equipment, and the problem of impracticality.

[0017] As described in the specification of Patent Document 2, the invention is based on seam welding. Therefore, it cannot be applied to joints with undulations that are not suitable for seam welding equipment, or joints with continuous small curves in the left-right direction. Its application range is limited, and thus it is impractical.

[0018] The invention in Patent Document 3 involves an extremely cumbersome welding method that involves melting the resin of the base material, filling it with other reinforcing fibers, and injecting molten resin, which is therefore impractical.

[0019] Patent Document 4 describes in paragraph 0034 that the welding electrode uses the same material as the material being welded, and in paragraph 0035, it describes that in the case of carbon fiber, the temperature must be raised to about 800-2000°C to weld these fibers. Since it is difficult for operators to perform welding operations at temperatures as high as 2000°C, there is a problem that only automated welding equipment suitable for mass production can perform this work, and it is not suitable for the numerous manual welding operations in individual production.

[0020] The present invention was made in view of the following problems, and aims to provide a welding electrode for fiber-reinforced plastics that can be used to weld fiber-reinforced plastic components together even when the welding operation is performed by an operator, and can weld joints with any bevel shape, can be melted by heating means such as hot air in inexpensive equipment, and can obtain the weld strength of plastic products, as well as a welding method using the welding electrode for fiber-reinforced plastics.

[0021] Solution for solving the problem

[0022] The welding rod for thermoplastic fiber-reinforced plastics described in Scheme 1 is a welding rod for fiber-reinforced plastics that can be melted by heating with hot air or a hot plate component. It is filled into the welding joint between thermoplastic fiber-reinforced plastic components, and the welding rod melts simultaneously with the thermoplastic fiber-reinforced plastic components. The characteristic feature is that the mixture of fiber and thermoplastic resin is formed into a strip, and the content of the fiber is set to 1% to 35% by weight when the mixture is 100% by weight.

[0023] The thermoplastic fiber-reinforced plastic welding electrode described in Scheme 2 is characterized in that, in Scheme 1, the fiber is any one of carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, modified polyphenylene ether fiber, and cellulose nanofiber.

[0024] The welding method using fiber-reinforced plastic welding rods described in Scheme 3 is a welding method for thermoplastic fiber-reinforced plastic components, characterized by comprising: a welding rod selection step, selecting a thermoplastic fiber-reinforced plastic welding rod containing a thermoplastic resin that produces an anchoring effect with the thermoplastic resin of the thermoplastic fiber-reinforced plastic component as the base material, and setting the fiber content to 1% to 35% by weight or less; and a welding step, pressing the tip of the thermoplastic fiber-reinforced plastic welding rod against the joint surface of the joint between the thermoplastic fiber-reinforced plastic components as the base material with appropriate pressure, melting only the thermoplastic resin contained in the welding rod and the thermoplastic fiber-reinforced plastic component by heating with hot air or a hot plate component, filling the joint surface with the molten thermoplastic resin and unmelted fiber, and moving the welding rod while pressing the tip of the welding rod against the joint surface along the joint.

[0025] Invention Effects

[0026] The welding electrode for thermoplastic fiber-reinforced plastics described in Scheme 1 or 2 enables the welding of thermoplastic fiber-reinforced plastic components to each other using inexpensive heating methods such as hot air or hot plate components. Furthermore, it achieves the following effects: regardless of whether the bevel shape is undulating, straight, curved, or concave-convex when viewed from above, joints with any bevel shape can be welded; the dimensional accuracy of the bevel shape does not require laser cutting; even bevel shapes with dimensional accuracy machined using CNC routers or general-purpose lathes can be welded. It eliminates the need for expensive laser welding equipment, allowing welding to be performed using inexpensive equipment such as hot air or hot plate heating to melt the material, thus achieving the tensile strength required for welding fiber-reinforced plastic products. Therefore, the welding electrode for thermoplastic fiber-reinforced plastics of the present invention offers practical benefits.

[0027] By using inexpensive heating methods such as hot air or hot plate components, the thermoplastic region of the tip of the fiber-reinforced plastic welding rod at the joint and the thermoplastic region of the fiber-reinforced plastic component as the base material are melted together, thus forming a mixture of the base material and the welding rod. The specified tensile strength can be obtained through the anchoring effect between the thermoplastic resin and the fiber in the mixture.

[0028] The welding method using thermoplastic fiber reinforced plastic welding rods described in Scheme 3 has the same effect as that of the thermoplastic fiber reinforced plastic welding rods described in Scheme 1 or 2. Therefore, it is a practical method for welding thermoplastic fiber reinforced plastics together.

[0029] The welding using the thermoplastic fiber reinforced plastic welding electrode of the present invention can be applied to both manual welding and welding automation devices. Attached Figure Description

[0030] Figure 1 This is a flowchart of the welding method of the present invention using welding electrodes for thermoplastic fiber reinforced plastics.

[0031] Figure 2 This is an explanatory diagram illustrating an example of an implementation of the welding method. Detailed Implementation

[0032] In the JIS standard concerning the weld strength of plastics, JIS Z 3831:2002 specifies the test methods and judgment criteria for the verification of plastic weldability. As for the types of test specimens, only three are specified: polyvinyl chloride, polypropylene, and high-density polyethylene with a tensile yield stress of 50 MPa or higher. Since there are no provisions regarding the welding of fiber-reinforced plastics, this indicates that welding of fiber-reinforced plastics is generally not performed.

[0033] In addition, products made of carbon fiber reinforced plastic were first used in Japan in 1972 for fishing rods for sweetfish, in 1973 for golf clubs, and in 1975 for aircraft components. Their adoption and use have continued to expand, and less than 50 years have passed since then, but there are no provisions in the JIS standard regarding the welding of fiber reinforced plastics.

[0034] Even today, about 50 years after carbon fiber reinforced plastic products began circulating in the market, there are still no JIS standards for welding carbon fiber reinforced plastics. As a method for fixing carbon fiber reinforced plastic components to each other, the general methods are adhesive bonding and mechanical methods such as bolts. However, since welding has not been practiced, the welding electrode for thermoplastic fiber reinforced plastics of the present invention is a groundbreaking invention that makes welding thermoplastic fiber reinforced plastic components to each other practically possible.

[0035] The welding electrode 4 for thermoplastic fiber-reinforced plastics of the present invention is a welding joint for thermoplastic fiber-reinforced plastic components 5a and 5b that is filled into each other and can be melted by a heating means (not shown) of hot air or hot plate components. The mixture of fiber and thermoplastic resin is formed into a strip and the content of the fiber is set to 1% to 35% by weight when the mixture is 100% by weight.

[0036] When the thermoplastic fiber-reinforced plastic welding electrode 4 of the present invention is used to fix the thermoplastic fiber-reinforced plastic components 5a and 5b, which are the parent materials 5a and 5b, together with the parent materials 5a and 5b, to each other through welding such as butt welding, T-shaped fillet welding or L-shaped fillet welding, it is melted together and filled into the joint surface of the joint and then cooled. The thermoplastic fiber-reinforced plastic components 5a and 5b are fixed to each other through the anchoring effect.

[0037] The anchoring effect described in this invention refers to the fact that when the thermoplastic resin containing the fibers of the thermoplastic fiber-reinforced plastic component as the parent materials 5a and 5b and the thermoplastic resin containing the fibers of the thermoplastic fiber-reinforced plastic welding rod 4 are melted and cooled and solidified approximately simultaneously by the same heating means (device or method), the fibers of the parent materials 5a, 5b and the thermoplastic fiber-reinforced plastic welding rod 4 are mixed with the thermoplastic resins of the parent materials 5a, 5b and the thermoplastic fiber-reinforced plastic welding rod 4, forming a state in which the parent materials 5a and 5b are strongly connected.

[0038] The anchoring effect can be generated in the following ways: First, the thermoplastic resin enters the small unevenness on the joint surface of the joint of the parent materials 5a and 5b, thereby being firmly connected; Second, the fiber itself has small unevenness, and the thermoplastic resin enters the unevenness, thereby being firmly connected; or, Third, the fibers of the thermoplastic fiber reinforced plastic welding rod 4 are inserted into the joint surface of the parent materials 5a and 5b and are firmly connected.

[0039] First, the thermoplastic fiber-reinforced plastic components, which serve as base materials 5a and 5b, will be described. These thermoplastic fiber-reinforced plastic components are mixtures of fibers and thermoplastic resins, and are parts made of thermoplastic fiber-reinforced plastic. In the case of thermoplastic carbon fiber-reinforced plastics, these components combine lightweight, high strength, and high reusability, and are widely used in products such as golf club handles, aircraft tail fins, monocoque chassis of automobiles, wind turbine blades, and assistant suits.

[0040] Furthermore, the fibers contained in the thermoplastic fiber-reinforced plastic component are any one or more of the following: carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, modified polyphenylene ether fiber, and cellulose nanofiber.

[0041] In addition, the carbon fiber used to make the thermoplastic fiber reinforced plastic component contain carbon as a fiber, besides the most commonly used PAN-based carbon fiber, can also be pitch-based carbon fiber or rayon-based carbon fiber, and can be any carbon fiber.

[0042] In addition, the thermoplastic resin contained in the thermoplastic fiber reinforced plastic component may be polyamide, polyester, polyphenylene sulfide, polyether ether ketone, polycarbonate, polyolefin, etc., as long as it is a thermoplastic resin, it can be any thermoplastic resin.

[0043] As joints for fixing thermoplastic fiber-reinforced plastic components, which are the parent materials 5a and 5b, to each other, there are butt joints, T-shaped corner joints, or L-shaped corner joints.

[0044] Next, the welding electrode for thermoplastic fiber-reinforced plastics will be described. The welding electrode for thermoplastic fiber-reinforced plastics is formed into a strip from a mixture of fiber and thermoplastic resin, wherein the fiber content is set to 1% to 35% by weight when the mixture is 100% by weight.

[0045] The fibers contained in the thermoplastic fiber reinforced plastic welding rod are any one or more of the following: carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, modified polyphenylene ether fiber, and cellulose nanofiber.

[0046] In addition, regarding carbon fiber, it can be one of the following: PAN-based carbon fiber, pitch-based carbon fiber, or rayon-based carbon fiber, or more than one type of carbon fiber.

[0047] Furthermore, regarding the relationship with the types of fibers in the parent materials 5a and 5b, it is preferable that the type of fiber in the thermoplastic fiber reinforced plastic welding electrode 4 is the same as that contained in the parent materials 5a and 5b. However, even if the type of fiber is different from that contained in the parent materials 5a and 5b, an anchoring effect will still occur. Therefore, as long as the fiber meets the condition of having an anchoring effect and having no quality problems as a product, it is acceptable. It is also acceptable that the fiber is a different type of fiber from the parent materials 5a and 5b.

[0048] Welding of the thermoplastic fiber-reinforced plastic component containing carbon fiber was performed as an experiment. However, in the case of welding the thermoplastic fiber-reinforced plastic component containing fibers other than carbon fiber, such as any one of glass fiber, boron fiber, aramid fiber, polyethylene fiber, modified polyphenylene ether fiber and cellulose nanofiber, the welding electrode 4 for thermoplastic fiber-reinforced plastic of the present invention can also be applied.

[0049] The thermoplastic resin contained in the thermoplastic fiber reinforced plastic welding rod can be polyamide, polyester, polyphenylene sulfide, polyetheretherketone, polycarbonate, polyolefin, etc., as long as it is a thermoplastic resin. It can be any thermoplastic resin. However, in terms of the relationship with the type of thermoplastic resin of the parent materials 5a and 5b, if it is a thermoplastic resin with a small difference in melting point when heated, then the thermoplastic resin of the thermoplastic fiber reinforced plastic welding rod 4 and the thermoplastic resin of the parent materials 5a and 5b will melt approximately simultaneously when heated. Therefore, the combination of the type of thermoplastic resin of the parent materials 5a and 5b and the type of thermoplastic resin of the thermoplastic fiber reinforced plastic welding rod 4 is preferably the same type, but it can also be a combination of different types, as long as the condition of obtaining the anchoring effect is met.

[0050] The type of thermoplastic resin in the thermoplastic fiber reinforced plastic component, which serves as the base material 5a and 5b, is the same as the type of thermoplastic resin contained in the thermoplastic fiber reinforced plastic welding rod 4. For example, this means that both the base material 5a and 5b contain polyamide and the thermoplastic resin contained in the thermoplastic fiber reinforced plastic welding rod 4 are polyamide. The type of thermoplastic resin is different from that in the case where the base material 5a and 5b contain polyvinyl chloride (melting point 85℃~210℃) and the thermoplastic resin contained in the thermoplastic fiber reinforced plastic welding rod 4 is acrylic resin (melting point 160℃).

[0051] Furthermore, the mixing ratio of fiber to thermoplastic resin in the thermoplastic fiber reinforced plastic welding electrode 4 is set to be a mixing ratio that can meet the tensile strength requirements for welding quality, regardless of the mixing ratio of fiber to thermoplastic resin contained in the thermoplastic fiber reinforced plastic components that serve as the base materials 5a and 5b.

[0052] Next, the heating method will be described. The heating method for melting the thermoplastic fiber-reinforced plastic welding rod 4 and the thermoplastic fiber-reinforced plastic components 5a and 5b, which are the base materials, is a heating method utilizing hot air or a hot plate component. This heating method, in order to melt the welding rod used for plastic welding, eliminates the need for laser beam irradiation requiring expensive equipment; instead, it uses hot air or a hot plate utilizing heat conduction as the heating method, thus allowing for the direct use of conventionally used heating methods.

[0053] Next, the tensile strength tested using the thermoplastic fiber-reinforced plastic welding electrode 4 of the present invention will be described. To conduct tensile tests using the thermoplastic fiber-reinforced plastic welding electrode 4 of the present invention, as a representative example, Table 1 shows the results of a tensile test conducted at a tensile speed of 50 mm / min using a thermoplastic fiber-reinforced plastic welding electrode 4 (3 mm diameter) containing carbon fibers, where two specimens with a width of 20 mm, a length of 30 mm, and a plate thickness of 2 mm were butt-welded. The average value in Table 1 represents the average value of three tests performed. In Table 1, the carbon fiber content of the thermoplastic carbon fiber reinforced plastic component used (equivalent to the base material 5) is set to 40% by weight, with the thermoplastic carbon fiber reinforced plastic component being 100% by weight. Furthermore, the carbon fiber content in Table 1 refers to the carbon fiber content in the thermoplastic carbon fiber reinforced plastic welding electrode 4.

[0054] [Table 1]

[0055] 0 The welding electrode melts before the base metal. 10 49.8 20 42.3 30 33.1 40 extremely small

[0056] Table 1 shows that in the welding of thermoplastic carbon fiber reinforced plastic components with a carbon fiber content of 40% by weight, when the carbon fiber content of the thermoplastic carbon fiber reinforced plastic welding rod 4 is set to 0% by weight, the melting of the two in a mixed state cannot proceed smoothly because the thermoplastic welding rod melts before the thermoplastic resin of the base material. When the carbon fiber content is set to 10% by weight, the tensile strength is the highest at 49.8 MPa. When the carbon fiber content is set to 20% by weight, the tensile strength decreases slightly (about 15% lower than at 10% by weight) to 42.3 MPa. When the carbon fiber content is set to 30% by weight, the tensile strength decreases further to 33.1 MPa (about 33% lower than at 10% by weight). When the carbon fiber content is set to the same 40% by weight as the base material, the tensile strength decreases further and becomes extremely low.

[0057] Furthermore, in the conventional welding of fiber-free plastic components, the tip of the welding rod is pressed against the joint surface while the welding rod and the base material melt and fill the joint surface. However, in the welding of thermoplastic fiber-reinforced plastic components, when the carbon fiber content of the thermoplastic carbon fiber reinforced plastic welding rod is set to 0% by weight and the thermoplastic resin content is set to 100% by weight, the melting temperature varies greatly simply due to the presence or absence of carbon fiber. Therefore, it is extremely difficult to weld the thermoplastic welding rod before the base material melts.

[0058] On the other hand, in general plastic welding, welding rods containing the same composition as the base material are used. When using welding rods with the same composition as the base material, for example, in the case of welding thermoplastic fiber-reinforced plastic components whose base material contains 40% carbon fiber, welding rod 4 containing 40% thermoplastic carbon fiber-reinforced plastic is used. When welding is performed under these conditions and tensile strength is measured, due to the excessive carbon fiber content, the amount of thermoplastic resin melted is reduced, the anchoring effect remains within a very narrow range, and the welded part separates from the base material due to extremely small tensile force.

[0059] Therefore, regarding the lower limit of the carbon fiber content in the thermoplastic carbon fiber reinforced plastic welding electrode 4, since the tensile strength is the highest when the carbon fiber content is 10% by weight, among the carbon fiber contents of 0%, 10%, 20%, and 30% by weight during the experiment, and since the melting point becomes higher and the difference between the melting temperature of the electrode and the base material 5 becomes smaller even if the thermoplastic carbon fiber reinforced plastic welding electrode 4 contains 1% by weight, the lower limit of the fiber content in the thermoplastic carbon fiber reinforced plastic welding electrode 4 is set to 1% by weight or more.

[0060] Furthermore, since the tensile strength decreases with increasing carbon fiber content among 10 wt%, 20 wt%, 30 wt%, and 40 wt%, with the tensile strength at 30 wt% decreasing by approximately 33% compared to 10 wt%, and the tensile strength at 40 wt% carbon fiber content being extremely low, the upper limit of the carbon fiber content in the welding rod for thermoplastic carbon fiber reinforced plastics is set at 35 wt%.

[0061] In existing plastic welding practices, it is common practice, albeit unwritten, in the plastic welding industry to use the same type of thermoplastic resin for the base material of the thermoplastic plastic as for the welding electrode. However, in this invention, the type of thermoplastic resin for the welding electrode used with thermoplastic carbon fiber reinforced plastic can also be different from the type of thermoplastic resin for the thermoplastic fiber reinforced plastic component, as long as it is a combination that produces an anchoring effect.

[0062] Furthermore, in existing plastic welding, if the common practice in the plastic welding industry of setting the type of thermoplastic resin in the thermoplastic base material to be the same as the type of thermoplastic resin in the welding electrode is applied to the welding of fiber-reinforced plastics, then the fiber content of the welding electrode should be the same as that of the base material. However, according to experiments, as shown in Table 1, welding cannot be performed at 40% by weight. Therefore, in this invention, the fiber content of the welding electrode for thermoplastic fiber-reinforced plastics is set independently of the fiber content of the thermoplastic fiber-reinforced plastic component in the base material.

[0063] Based on the above, the present invention, by partially melting the thermoplastic resin without melting the fiber to create an anchoring effect and fix it, can be applied to any type of fiber. Furthermore, regarding the fiber content of the thermoplastic fiber reinforced plastic welding electrode 4, when the thermoplastic fiber reinforced plastic welding electrode 4 is set to 100% by weight, the fiber content is set to 1% by weight or more to 35% by weight or less, preferably 3% by weight or more to 30% by weight or less.

[0064] Furthermore, as for welding strength, Table 1 shows tensile strengths ranging from 33.1 to 49.8 MPa. This is stronger than the tensile strengths specified in JIS Z 3831:2002, the criteria for determining the pass / fail of tensile tests on welded parts of plastic welds. Specifically, for butt welds with a welding rod diameter of 3 mm, a specimen width of 20 mm, a length of 60 mm, and a plate thickness of 5 mm, the tensile strength at a tensile speed of 50 mm / min is ≥30 MPa for PVC plates, ≥15 MPa for polypropylene plates, and ≥12 MPa for polyethylene plates.

[0065] In addition, as a comparison of tensile strength, Table 2 shows the results of tests conducted on tensile shear forces in the case of bonding fiber-reinforced plastic components using adhesives, a common method for fixing these components together. The test material was thermoplastic carbon fiber reinforced plastic components with a joint area of ​​400 mm². 2 The specimens were 20 mm wide, 60 mm long, and 1 mm thick, and were tested using a benchtop universal testing machine at a tensile speed of 0.5 mm / min.

[0066] [Table 2]

[0067] Epoxy resin 3.48 acrylic resin 3.95

[0068] As shown in Table 2, tensile force and tensile shear force are forces of different natures and therefore cannot be compared simply. However, judging from the comparison of the size of the bonding area and the welding area, the welding using the thermoplastic carbon fiber reinforced plastic welding rod of the present invention has sufficient tensile strength.

[0069] When thermoplastic fiber reinforced plastic components are fixed together, the welding rod 4 of the present invention is used for welding. Since the thermoplastic resins are heated to the melting point of the thermoplastic resin used, the thermoplastic resins of both parties melt. The anchoring effect between the non-melting fiber and the molten thermoplastic resin fixes them together. Therefore, it shows that welding can be performed regardless of the type of fiber.

[0070] The welding electrode for thermoplastic fiber-reinforced plastics of the present invention is applicable to the welding of components of thermoplastic carbon fiber-reinforced plastics, thermoplastic glass fiber-reinforced plastics, thermoplastic boron fiber-reinforced plastics, thermoplastic aramid fiber-reinforced plastics, thermoplastic polyethylene fiber-reinforced plastics, thermoplastic modified polyphenylene ether fiber-reinforced plastics, or thermoplastic cellulose nanofiber-reinforced plastics. Welding can also be performed by selecting at least one type of fiber from carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, modified polyphenylene ether fiber, or cellulose nanofiber.

[0071] like Figure 1 or Figure 2 As shown, the welding method 1 using the thermoplastic fiber reinforced plastic welding rod of the present invention is a welding method 1 for thermoplastic fiber reinforced plastic components to each other, comprising: a welding rod selection step 2, selecting a thermoplastic fiber reinforced plastic welding rod 4 containing a thermoplastic resin that produces an anchoring effect with the thermoplastic resin of the thermoplastic fiber reinforced plastic components 5a and 5b, and setting the fiber content to 1% by weight or more to 35% by weight or less; and a welding step 3, pressing the front end of the thermoplastic fiber reinforced plastic welding rod 4 against the joint surface of the joint portion of the thermoplastic fiber reinforced plastic components 5a and 5b with appropriate pressing pressure, and using a heating means (not shown) of hot air or a hot plate component to melt only the thermoplastic resin contained in the thermoplastic fiber reinforced plastic welding rod 4 and the thermoplastic resin contained in the thermoplastic fiber reinforced plastic components 5a and 5b respectively, filling the joint surface of the joint portion with the molten thermoplastic resin and unmelted fibers, and moving the front end of the thermoplastic fiber reinforced plastic welding rod 4 along the joint portion while pressing it against the joint surface of the joint portion.

[0072] In the electrode selection step 2, a thermoplastic resin containing a type of thermoplastic resin that produces an anchoring effect with the thermoplastic fiber-reinforced plastic component used as the base material 5a, 5b is selected, and the content of any type of fiber is set to 1% to 35% by weight or less for thermoplastic fiber-reinforced plastic welding electrode 4.

[0073] The thermoplastic fiber-reinforced plastic welding electrode 4 of the present invention is a fiber-reinforced plastic welding electrode 4 that fills the welding joint between thermoplastic fiber-reinforced plastic components that serve as base materials 5a and 5b, and can be melted by heating means of hot air or hot plate components. Furthermore, the welding electrode 4 is formed into a strip shape from a mixture of fiber and thermoplastic resin. The fiber content is 1% by weight or more to 35% by weight or less.

[0074] Furthermore, the fiber is any one or more of the following: carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, modified polyphenylene ether fiber, and cellulose nanofiber. The type of fiber contained in the thermoplastic fiber-reinforced plastic welding electrode 4 is preferably the same as that in the base materials 5a and 5b, but it can also be a different type of fiber, as long as its strength and other qualities meet the quality standards for the product.

[0075] The heating method of the hot air or hot plate component can be any heating method that can heat the thermoplastic resin to a molten state.

[0076] Regarding the types of thermoplastic resins contained in the aforementioned thermoplastic fiber reinforced plastic welding electrode 4, any combination of thermoplastic resins that have the anchoring effect is acceptable, including combinations of the same type and combinations of different types.

[0077] like Figure 2 As shown, in welding step 3, the tip of the thermoplastic fiber reinforced plastic welding rod 4 is pressed against the joint surface of the thermoplastic fiber reinforced plastic components 5a and 5b, which are the base materials, with moderate pressure. A molten portion 8 is created by heating the welding rod 4 with hot air or a hot plate to a temperature that melts only the thermoplastic resin of the welding rod 4 and the thermoplastic fiber reinforced plastic components 5a and 5b. The molten thermoplastic resin and unmelted fibers are then filled into the joint surface, and the welding rod moves along the joint in the direction of arrow H. A clear weld bead 9 is formed on the movement trace.

[0078] The tip of the thermoplastic fiber-reinforced plastic welding electrode 4 is pressed against the joint surface of the thermoplastic fiber-reinforced plastic components 5a and 5b, which are the base materials, with appropriate pressure. If the electrode does not melt upon contact with the joint surface, the joint surface will not be filled, and defects such as pinholes are likely to occur. The appropriate pressing pressure is simply the pressure applied while the tip of the thermoplastic fiber-reinforced plastic welding electrode 4 is continuously pressed against the joint surface of the joint as it travels along the joint.

[0079] Furthermore, the thermoplastic resin at the tip of the thermoplastic fiber-reinforced plastic welding electrode 4, and the thermoplastic resin at the joint surface of the thermoplastic fiber-reinforced plastic components serving as base materials 5a and 5b, are melted, for example, by hot air sprayed from the tip 6a of the welding torch 6 at a temperature that melts only the thermoplastic resin. The molten thermoplastic resin and unmelted fibers are then filled into the joint surface. By melting the thermoplastic fiber-reinforced plastic welding electrode and the thermoplastic resin of the thermoplastic fiber-reinforced plastic components serving as base materials 5a and 5b, an anchoring effect is generated, thus ensuring tensile strength as a weld strength.

[0080] In the welding method 1 using the welding electrode for thermoplastic fiber-reinforced plastics of the present invention, since the welding of the thermoplastic fiber-reinforced plastic components to each other can be performed at the same temperature as the welding of conventional plastic components that do not contain fibers, it has the advantage that welding can be performed by humans or by welding equipment. It also has the advantage that the joints between the thermoplastic fiber-reinforced plastic components do not need to be made into interlocking zipper-like insert joints, such as... Figure 2 As shown, it can also be a simple, roughly straight-line-shaped connector.

[0081] Explanation of reference numerals in the attached figures

[0082] 1 Welding Method

[0083] 2. Electrode Selection Steps

[0084] 3 Welding steps

[0085] 4 Welding electrodes

[0086] 5. Base Material

[0087] 6 Welding torches

[0088] 6a Front end

[0089] 8. Melting section

[0090] 9 Welds

[0091] H direction.

Claims

1. A welding electrode for thermoplastic fiber-reinforced plastics, which is a welding electrode for fiber-reinforced plastics that can be melted by heating with hot air or a hot plate component, is applied to the welding joint between thermoplastic fiber-reinforced plastic components, and the welding electrode also melts simultaneously with the thermoplastic fiber-reinforced plastic components, characterized in that... The mixture of fiber and thermoplastic resin is formed into strips. The fiber content is set to 1% to 35% by weight when the mixture is 100% by weight.

2. The welding electrode for thermoplastic fiber-reinforced plastics according to claim 1, characterized in that, The fiber is any one of carbon fiber, glass fiber, boron fiber, aramid fiber, polyethylene fiber, modified polyphenylene ether fiber, and cellulose nanofiber.

3. A welding method using welding electrodes for thermoplastic fiber reinforced plastics, characterized in that, have: The electrode selection procedure involves selecting a thermoplastic resin containing a thermoplastic resin that produces an anchoring effect with the thermoplastic fiber-reinforced plastic component used as the base material, and setting the fiber content to be 1% by weight or more to 35% by weight or less for thermoplastic fiber-reinforced plastic welding electrodes. as well as In the welding step, the tip of the thermoplastic fiber reinforced plastic welding rod is pressed against the joint surface of the joint between the thermoplastic fiber reinforced plastic components, which serve as the base material, with appropriate pressure. The thermoplastic resin contained in the thermoplastic fiber reinforced plastic welding rod and the thermoplastic fiber reinforced plastic components is melted by heating with hot air or a hot plate component. While filling the joint surface with the molten thermoplastic resin and unmelted fibers, the tip of the thermoplastic fiber reinforced plastic welding rod is pressed against the joint surface along the joint and moved.

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