Thermoplastic composite induction welding method based on magnetic concentrator

Abstract

The invention provides a thermoplastic composite induction welding method based on a magnetic concentrator, which comprises the following steps of: preparing a thermoplastic laminated plate, cutting, polishing, cutting a thermoplastic resin film with the same resin matrix, and welding to obtain the magnetic concentrator. The method comprises the following steps: placing a polished thermoplastic laminated plate and a thermoplastic resin film in a to-be-welded area in a single lap joint manner, fixing in an induction welding device, mounting a magnetic concentrator above a composite material far away from one side of an induction coil, applying pressure, and controlling induction welding parameters to realize welding of a composite material plate, and after welding is completed, continuously maintaining the pressure until the material is cooled, and unloading to complete the induction welding of the thermoplastic composite material. The permanent magnet is adopted as the magnetic concentrator, so that the temperature of the center point of the welding interface is increased, the effective welding area is increased, the problem that the temperature of the center area of the induction welding interface is too low or the edge is too hot can be effectively solved, and the mechanical property of a welding joint of a thermoplastic composite material is obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material welding methods, and in particular relates to a thermoplastic composite material induction welding method based on a magnetic concentrator. Background Art

[0002] Carbon fiber reinforced thermoplastic composites have the characteristics of short molding cycle, high production efficiency, re-melting molding and weldability, and are widely used in aerospace and other fields. Induction welding has the characteristics of precise welding area, strong flexibility and non-contact welding. It can avoid the stress concentration and weight gain problems of traditional mechanical connection, the mismatch between the binder and the thermoplastic resin with weak polarity and poor environmental adaptability in bonding, the stress concentration and electrochemical corrosion caused by the resistance wire remaining at the welding interface in resistance welding, and the limitation of ultrasonic welding that is not suitable for large-area or special-shaped structural parts. Therefore, induction welding is considered to be one of the most promising thermoplastic composite connection technologies.

[0003] However, the temperature non-uniformity of the induction welding surface of carbon fiber reinforced thermoplastic composites is extremely strong, and it is very easy for the welding center temperature to be too low or the edge area to be overheated, which seriously affects the quality and strength of the welding interface and has become a key issue restricting the further application of induction welding technology.

[0004] Based on this, a method of induction welding of thermoplastic composites based on magnetic concentrator is proposed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a thermoplastic composite material induction welding method based on a magnetic concentrator in view of the deficiencies of the above-mentioned prior art, so as to solve the problems raised in the above-mentioned background technology.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a thermoplastic composite material induction welding method based on a magnetic concentrator, comprising the following steps:

[0007] S1. Laying the prepreg laminate on the mold surface according to the laying plan, and curing and forming it under the influence of curing and forming factors to complete the preparation of the thermoplastic laminate;

[0008] S2, cutting the thermoplastic laminate and performing grinding treatment;

[0009] S3, cutting the thermoplastic resin film with the same resin matrix, wherein the cutting area corresponds to the area of ​​the welding joint;

[0010] S4, placing the polished thermoplastic laminate and the thermoplastic resin film in a single overlapped form in the area to be welded, and fixing them in an induction welding device;

[0011] S5, installing the magnetic concentrator above the composite material on the side away from the induction coil, applying pressure, controlling the induction welding parameters to achieve welding of the composite material plate, and maintaining the pressure after welding until the material is cooled and then unloading to complete the induction welding of the thermoplastic composite material;

[0012] S6. Use a universal testing machine to perform a single lap tensile shear test on the completed thermoplastic composite weld to check the welding strength of the welded joint.

[0013] As a further illustration of the present invention, the resin matrix of the thermoplastic laminate 3 is polyphenylene sulfide PPS, polyether ketone PEK, polyether ether ketone PEEK, polyether ketone ketone PEKK or polyether imide PEI.

[0014] As a further explanation of the present invention, the thermoplastic laminate in S2 needs to be cleaned and dried after polishing, specifically, it is cleaned with anhydrous ethanol to remove surface impurities, and then put into an oven to dry or dry naturally. The cut thermoplastic resin film in S3 needs to be cleaned and dried, specifically, it is cleaned with anhydrous ethanol to remove surface impurities, and then put into an oven to dry or dry naturally.

[0015] As a further illustration of the present invention, the thermoplastic resin film in S4 is placed between two thermoplastic laminates to be welded and fixed by a supporting structure.

[0016] As a further illustration of the present invention, the magnetic concentrator is cylindrical, the diameter of the magnetic concentrator is smaller than the diameter of the induction coil, the induction coil is placed directly below the magnetic concentrator, and the line connecting the center of the induction coil and the center of the magnetic concentrator is perpendicular to the thermoplastic laminate.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The present invention adopts a permanent magnet as a magnetic concentrator, and then prepares a thermoplastic composite panel, and finally places the magnetic concentrator on the side of the composite material away from the induction coil for induction welding, and finally obtains a thermoplastic composite welded component. The permanent magnet is used as a magnetic concentrator to increase the temperature of the center point of the welding interface and increase the effective welding area, which can effectively alleviate the problem of low temperature in the center area of ​​the induction welding interface or overheating at the edge, and significantly improve the mechanical properties of the welded joint of the thermoplastic composite material. In addition, in the present invention, a thermoplastic resin film with the same resin matrix is ​​added in the middle of the welded joint to increase the glue content of the welding interface, thereby enhancing the welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of induction welding of the present invention;

[0020] Figure 2 is a molding process curve of the composite material in an embodiment of the present invention;

[0021] Figure 3 Schematic diagram of mechanical properties of induction welding joints with and without magnetic concentrators in an embodiment of the present invention;

[0022] Description of reference numerals:

[0023] 1-magnetic concentrator; 2-support structure; 3-thermoplastic laminate; 4-induction coil; 5-thermoplastic resin film. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Examples, such as Figure 1 As shown, the present invention provides a technical solution: a thermoplastic composite induction welding method based on a magnetic concentrator, comprising the following steps:

[0026] S1, laying the prepreg laminate on the mold surface according to the laying plan, curing and forming it under the influence of curing and forming factors, and completing the preparation of the thermoplastic laminate 3, the resin matrix of the thermoplastic laminate 3 is polyphenylene sulfide PPS, polyether ketone PEK, polyether ether ketone PEEK, polyether ketone ketone PEKK or polyether imide PEI;

[0027] S2, cutting the thermoplastic laminate 3 and grinding it, and then cleaning and drying it, specifically, using anhydrous ethanol to clean and remove surface impurities, and then putting it in an oven to dry or air dry it;

[0028] S3, cutting the thermoplastic resin film 5 of the same resin matrix, the cutting area size corresponds to the area size of the welding joint area, and the cut thermoplastic resin film 5 needs to be cleaned and dried, specifically, after cleaning with anhydrous ethanol to remove surface impurities, it is placed in an oven for drying or dried naturally;

[0029] S4, placing the polished thermoplastic laminate 3 and the thermoplastic resin film 5 in the area to be welded in a single overlap form, and fixing them in an induction welding device, specifically, the thermoplastic resin film 5 is placed between the two thermoplastic laminates 3 to be welded, and fixed by a support structure 2;

[0030] S5. Install the magnetic concentrator 1 above the composite material away from the side of the induction coil 4, apply pressure, and control the induction welding parameters to achieve welding of the composite material plate. The magnetic concentrator 1 is a cylindrical permanent magnet. The diameter of the magnetic concentrator 1 is smaller than the diameter of the induction coil 4. The induction coil 4 is placed directly below the magnetic concentrator 1. The line connecting the center of the induction coil 4 and the center of the magnetic concentrator 1 is perpendicular to the thermoplastic laminate 3. After welding is completed, the pressure is maintained until the material is cooled and then unloaded to complete the induction welding of the thermoplastic composite material.

[0031] S6. Use a universal testing machine to perform a single lap tensile shear test on the completed thermoplastic composite weld to check the welding strength of the welded joint.

[0032] Experimental example, taking carbon fiber reinforced thermoplastic composite induction welding as an example, CF / PEEK,

[0033] S1. Cut the prepreg into 300mm*300mm, then cover it with high temperature resistant release cloth coated with release agent, lay it on the mold surface, and place it in the hot press together. Refer to the specified curing process system, such as Figure 2 As shown, the thermoplastic composite laminate 3 is taken out together with the mold after curing and molding in a high temperature and high pressure environment and after cooling and releasing the pressure.

[0034] S2. Cut the thermoplastic laminate 3 into pieces of 25 mm*150 mm using a cutting machine, polish the surface with sandpaper to remove the surface release agent, clean it with anhydrous ethanol to remove surface impurities, and then put it into an oven for drying or air-dry it naturally.

[0035] S3. Cut the PEEK resin film into a size of 25 mm*25 mm, and clean it with anhydrous ethanol to remove surface impurities, and then put it in an oven to dry or dry it naturally.

[0036] S4. Use high temperature resistant tape to fix the thermoplastic composite laminate 3 prepared by S2 and the thermoplastic resin film 5 prepared by S3 in a single overlap form, place them in the area to be welded, and fix them with supporting material 2, which is mica sheet, and is beneficial to the heat dissipation of the composite surface.

[0037] S5, fix the magnetic concentrator 1 above the composite material on the side away from the induction coil 4, such as Figure 1 As shown, pressure is applied. The same welding parameters are ensured, and the welding of composite plates is achieved under the conditions of adding and not adding magnetic concentrators. After welding, the pressure is maintained until the material is cooled and then unloaded to complete the induction welding of thermoplastic composite materials.

[0038] S6. Use a universal testing machine to perform a single lap tensile shear test on the thermoplastic composite welded specimens welded in S5 to check the welding strength of the welded joints. Figure 3 shown.

[0039] The results show that the maximum strength of the welded joint after adding the magnetic concentrator can reach 37.75Mpa, which is 36.65% higher than that of the welded joint without adding the magnetic concentrator.

[0040] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0041] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for induction welding of thermoplastic composite materials based on a magnetic concentrator, characterized in that: The following steps are involved: S1, laying the prepreg stack on the mold surface according to the laying plan, and solidifying and forming it under the influence of the curing and forming factors to complete the preparation of the thermoplastic laminate (3); S2, cutting the thermoplastic laminate (3) and then grinding it; S3, cutting the thermoplastic resin film (5) of the same resin matrix, wherein the cutting area corresponds to the area of ​​the welding joint; S4, placing the polished thermoplastic laminate (3) and the thermoplastic resin film (5) in a single overlapped manner in the area to be welded, and fixing them in an induction welding device; S5, installing the magnetic concentrator (1) above the composite material on the side away from the induction coil (4), applying pressure, controlling the induction welding parameters to achieve welding of the composite material plate, and maintaining the pressure after welding until the material is cooled and then unloading to complete the induction welding of the thermoplastic composite material; S6. Use a universal testing machine to perform a single lap tensile shear test on the completed thermoplastic composite weld to check the welding strength of the welded joint.

2. A method for induction welding of thermoplastic composite materials based on a magnetic concentrator according to claim 1, characterized in that: The resin matrix of the thermoplastic laminate (3) is polyphenylene sulfide PPS, polyether ketone PEK, polyether ether ketone PEEK, polyether ketone ketone PEKK or polyether imide PEI.

3. The method for induction welding of thermoplastic composite materials based on a magnetic concentrator according to claim 1, characterized in that: The thermoplastic laminate (3) in S2 needs to be cleaned and dried after polishing, specifically, it is cleaned with anhydrous ethanol to remove surface impurities, and then placed in an oven for drying or air-dried. The cut thermoplastic resin film (5) in S3 needs to be cleaned and dried, specifically, it is cleaned with anhydrous ethanol to remove surface impurities, and then placed in an oven for drying or air-dried.

4. The method for induction welding of thermoplastic composite materials based on a magnetic concentrator according to claim 1, characterized in that: The thermoplastic resin film (5) in S4 is placed between two thermoplastic laminates (3) to be welded and fixed by a supporting structure (2).

5. The method for induction welding of thermoplastic composite materials based on a magnetic concentrator according to claim 1, characterized in that: The magnetic concentrator (1) is a cylindrical permanent magnet. The diameter of the magnetic concentrator (1) is smaller than the diameter of the induction coil (4). The induction coil (4) is placed directly below the magnetic concentrator (1). The line connecting the center of the induction coil (4) and the center of the magnetic concentrator (1) is perpendicular to the thermoplastic laminate (3).

6. The method for induction welding of thermoplastic composite materials based on a magnetic concentrator according to claim 1, characterized in that: The curing molding factors are temperature, time and pressure.

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