Manufacturing and self-heating riveting method of thermoplastic composite material and metal mixed structure rivet

Abstract

The invention discloses a manufacturing and self-heating riveting method of a thermoplastic composite material and metal mixed structure rivet. According to the method, firstly, a thermoplastic composite material and metal mixed rivet is designed, and a process and mold design for preparing the metal and thermoplastic composite material mixed structure rivet through a two-step mold pressing method are provided. The added metal in the prepared rivet has high electromagnetic induction heating capacity, and in the riveting process, the rivet is heated to the working temperature through induction current and then pressed to complete press riveting connection. By means of the technology, the weight of the metal rivet can be obviously reduced, rapid self-heating riveting can be achieved, in addition, composite material hole edge damage possibly caused by machining can be filled through heating and melting of the thermoplastic composite material, meanwhile, abrasion and electrochemical corrosion between the rivet and a plate are avoided, and the service life of the rivet is prolonged. And the sealing performance and the shock and vibration resistance of the riveted joint are improved. In addition, after riveting is completed, reliable pier heads formed at the two ends of the rivet improve the connecting strength and reliability, and the rivet is suitable for complex working conditions.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a thermoplastic composite material and metal mixed structure rivet and a self-heating riveting method, belonging to the technical field of composite materials and material processing and connection. Background Art

[0002] Thermoplastic composites have been widely used to replace metal materials in many parts of aircraft due to their light weight, excellent mechanical properties and chemical properties such as corrosion resistance. These materials are mainly used in wing panels, stabilizers and fuselage structures. With the lightweight of fuselage materials, fasteners are also increasingly lightweight. Among the fastening methods of aircraft, adhesive bonding has unstable problems in reliability and airworthiness, screw bonding is limited by its heavy weight and easy loosening, and riveting technology is widely used due to its maturity and ease of maintenance and inspection. Traditional metal rivet fastening has problems such as galvanic corrosion, moisture corrosion, lightning strike risk, weight increase and dimensional instability caused by differences in thermal expansion coefficients.

[0003] Carbon fiber thermoplastic composite rivets are rivets made of high-performance composite materials, which have many advantages of composite materials. The advantages of carbon fiber thermoplastic composite rivets are: (1) High strength and rigidity: The addition of carbon fiber significantly improves the tensile and shear strength of the rivet, enabling it to withstand greater loads and is suitable for applications that withstand high forces. (2) Lightweight: Carbon fiber reinforced PEEK rivets are lighter than metal rivets, which helps reduce the weight of the overall structure, which is particularly important in the aerospace and automotive industries. (3) Excellent chemical and heat resistance: For example, PEEK itself has excellent chemical corrosion resistance and high temperature resistance, which allows rivets to be used in harsh environments, such as exposure to grease, fuel, and strong acids and alkalis. (4) Good fatigue resistance: For example, carbon fiber reinforced PEEK rivets can withstand repeated loads without fatigue fracture, and are suitable for long-term reliability applications. (5) Low thermal expansion coefficient: This type of rivet has a low thermal expansion coefficient, which can maintain better dimensional stability and maintain structural integrity even in environments with large temperature fluctuations. At the same time, composite materials also have some disadvantages: (1) Difficult processing: Resin and carbon fiber are difficult to process and require special processing equipment and technology, which increases production costs. (2) Repair and recycling issues: Compared with metal materials, the repair and recycling of composite materials is more complicated and difficult and may require special methods or technologies.

[0004] Through the analysis of the advantages and disadvantages of carbon fiber thermoplastic composite rivets, it is proposed to use thermoplastic composite and metal hybrid structure rivets as fasteners, which can significantly reduce the overall weight and process the thermoplastic composite better and faster by induction heating the internal metal.

[0005] Induction heating technology has the advantages of high power transmission efficiency and supports fast and targeted heating. Polymers have low electrical conductivity. Induction heating can quickly heat thermoplastic composites by heating metal induction heating media. The heating temperature can be adjusted according to frequency, power, coil shape, working distance, etc., and induction heating is feasible for assisting thermoplastic composite adhesion, micro-damage recovery, component molding and resin curing. During the heating process, the melting of the thermoplastic composite material inside the rivet of the hybrid structure of thermoplastic composite and metal can effectively fill the damage caused by mechanical processing of the connecting plate, while preventing wear and electrochemical corrosion between the rivet and the plate. In addition, this technology enhances the strength and reliability of the connection by improving the sealing and impact and vibration resistance of the riveted joint. The reliable piers formed at both ends of the rivet after riveting, as well as the high strength and high ductility of the thermoplastic composite material, together provide excellent riveting performance, making this method suitable for complex working conditions.

[0006] Shandong AVIC Hehui Aviation Standard Parts Co., Ltd. has disclosed a composite material rivet hot pressing forming device and a method for riveting composite plates with the same in its invention patent with publication number CN116803665A. This method greatly reduces the overall weight of composite material components, avoids wear and electrochemical corrosion between rivets and plate hole walls, reduces the impact of connection on the surface shape of components, and improves the sealing performance of riveted joints and the ability to resist thermal mismatch and impact vibration. After riveting, both ends of the rivet have reliable upsetting heads, which greatly improves the connection strength and reliability and can adapt to complex working conditions.

[0007] The thermoplastic composite material used in this patent is a continuous carbon fiber reinforced PEEK thermoplastic composite rivet. Since PEEK has a high processing temperature and low thermal conductivity, a complex external heating system is required for long-term heating during the riveting process. Therefore, the heating time is long and the riveting efficiency is low. In view of this, we have designed a thermoplastic composite metal hybrid structure rivet that can be quickly self-inductively heated to achieve rapid riveting, improve riveting efficiency, and reduce connection costs. Summary of the invention

[0008] The technical problem to be solved by the present invention is that there are potential problems in metal rivet fastening in the aerospace industry, including the disadvantages of reducing composite material layer damage, galvanic corrosion, moisture corrosion, lightning strike threat, weight increase and dimensional stability due to different thermal expansion coefficients.

[0009] In order to solve the above problems, the present invention provides a method for manufacturing and self-heating riveting a thermoplastic composite material and metal hybrid structure rivet, comprising the following steps:

[0010] Step 1) Preparation of thermoplastic composite material and metal hybrid structure rivets:

[0011] Step 1.1): The thermoplastic carbon fiber prepreg is laminated and wound around a metal induction heating medium, and then placed in a rod pressing mold, and a rod-shaped blank is formed by a radial molding mold; or a composite material and a metal medium are laminated and molded to form a composite material and metal mixed laminate, and then a rectangular or round rod-shaped blank is formed by machining;

[0012] Step 1.2): Compression molding of rivets: placing the blank in a detachable rivet compression molding mold, placing a release agent between the mold and the bar material to facilitate demolding, and compression molding to obtain a thermoplastic composite material and metal hybrid structure rivet;

[0013] Step 1.3): Subsequent processing and heat treatment of rivets: The manufactured thermoplastic composite material and metal hybrid structure rivets are machined to grind off edge burrs and excess resin, and then annealed and tempered heat treatment is performed as needed;

[0014] Step 2), self-heating riveting of thermoplastic composite material and metal hybrid structure rivets:

[0015] Step 2.1): Preparation and positioning of the composite material or metal parts to be connected: holes are made in the composite material or metal sheet to be connected by machining, and the holes are placed on the riveting platform for overlapping positioning;

[0016] Step 2.2): Rivet clamping: clamp the thermoplastic composite material and metal hybrid structure rivet into the riveting equipment, adjust the position and direction of the rivet, ensure that the rivet is placed in the center of the induction current heating coil and the rivet is vertically downward, and prepare for riveting;

[0017] Step 2.3): Press riveting: Start the induction current heating riveting equipment. After the induction heating lasts for 1 to 60 seconds, the rivet reaches the preset temperature and automatically completes the pressing operation. The rivet is pressed into the prefabricated through hole of the two plates. The rivet contacts the lower die to complete the pressing. After the upper plate stops moving, a constant pressure value is maintained and the pressure is maintained. After cooling, the plate connection is completed.

[0018] Step 2.4): Check the riveted structure: First, visually inspect the integrity and surface defects of the riveted structure, and then detect the internal defects of the riveted structure through non-destructive testing.

[0019] Preferably, in step 1.1), the raw materials of the thermoplastic carbon fiber prepreg include resin powder material and carbon fiber raw material.

[0020] More preferably, the resin powder material is at least one of polyamide-6, polyetheretherketone (PEEK), and polyphenylene sulfide (PPS).

[0021] More preferably, the carbon fiber raw material is at least one of unidirectional carbon fiber prepreg and carbon fiber fabric.

[0022] Preferably, in step 1.1), the specifications of the metal induction heating medium are at least one of round rod, layer, mesh, and granular.

[0023] Preferably, in the step 1.1), the mixed structure of the blank is an alternating laminated structure; and the volume percentage of the carbon fiber raw material in the blank is 40%-65%.

[0024] Preferably, in step 2.3), the parameters of the induction current heating riveting equipment are adjusted according to the material and structure of the rivet, and the parameters of the riveting equipment include heating power, riveting pressure, speed, and holding time.

[0025] Preferably, in step 2.3), the holding time is 1-10s.

[0026] Preferably, in step 2.3), the prefabricated through holes on the two plates are reserved when the plates are prepared or obtained by drilling, and the method of connecting the thermoplastic composite material and metal hybrid structure rivets to the two plates is: connecting one of the composite material and the composite material structure, the composite material and the metal structure, and the metal and the metal structure. The weight of the connection structure is lighter than that of the metal rivet connection, and the connection strength thereof can exceed that of the general metal rivet through reasonable rivet design.

[0027] Thermoplastic composite and metal hybrid structure rivets greatly reduce the overall weight of the composite structure. When the thermoplastic composite material is heated and melted, the internal resin can fill the damage of the composite material caused by mechanical processing, while avoiding wear and electrochemical corrosion between the rivet and the plate, and improving the sealing performance and impact and vibration resistance of the riveted joint. After riveting, there are reliable piers at both ends, which improves the connection strength and reliability, and can be used in complex working conditions.

[0028] The present invention provides a thermoplastic composite material and metal hybrid structure rivet and a rapid self-heating riveting method thereof. The thermoplastic composite material and metal hybrid structure rivet can replace metal rivets, and while improving stability, has a high modulus of the composite material to increase strength and reduce the weight of the connection structure.

[0029] Compared with the existing metal rivets and riveting methods, the beneficial effects of the present invention are:

[0030] (1) The specific strength of the thermoplastic composite material and metal hybrid structure rivet of the present invention is greater than that of the existing metal rivet, and the mass of the thermoplastic composite material and metal hybrid structure rivet is lighter than that of the metal rivet;

[0031] (2) It overcomes the damage caused by metal rivets between the connecting plates, and the thermoplastic composite material can fill the damage caused by mechanical processing on the side of the connecting part when it is heated and plasticized;

[0032] (3) The composite material on the outside and the induction heating medium on the inside of the thermoplastic composite material and metal hybrid structure rivet described in the present invention are flexible in design;

[0033] (4) The riveting method uses induction current heating, which is more efficient and simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the process of molding rivets using thermoplastic composite materials and metal hybrid rods provided in the embodiment;

[0035] Figure 2 A schematic diagram of the working of the rivet forming die provided in the embodiment;

[0036] Figure 3 A schematic diagram of a forming die for a coiled rivet bar provided in an embodiment;

[0037] Figure 4 A schematic diagram of the induction heating riveting process of a thermoplastic composite material and metal hybrid structure rivet provided in an embodiment;

[0038] Figure 1-4 Among them, 1 is resin powder material, 2 is carbon fiber raw material, 3 is metal induction heating medium, 4 is thermoplastic composite material and metal hybrid structure rod, 5 is induction current heating riveting equipment, 6 is thermoplastic composite material and metal hybrid structure rivet, 7 is detachable rod molding die, and 8 is rivet molding die. DETAILED DESCRIPTION

[0039] In order to make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0040] Example 1

[0041] Prepare a thin layer of stainless steel and carbon fiber reinforced PEEK unidirectional prepreg (Toray T800);

[0042] The carbon fiber prepreg is wound into 1 layer of stainless steel thin layer and 7 layers of prepreg; a cylindrical thermoplastic composite material hybrid metal structure is formed by a mold; the prepared thermoplastic composite material hybrid metal hybrid structure preform is placed in a forming mold; a mold release agent is applied between the mold and the preform; the hot press parameters are 390℃ / 5MPa; and a thermoplastic composite material and metal hybrid structure rivet is formed by a hot pressing molding process;

[0043] The manufactured rivets are clamped by a riveting machine, and high-frequency alternating current (220KHz, 5 turns, 220A) is passed through the coil in the rivet gun. After 10s-30s, the rivets reach the working temperature and are pressed into the prefabricated holes at the joints of the composite plate and the metal plate, and then contact the rivet lower die coated with a release agent to form a pier head to complete the fastening.

[0044] Example 2

[0045] Prepare copper alloy thin layer, carbon fiber polyamide unidirectional prepreg (T800);

[0046] Carbon fiber polyamide unidirectional prepreg is stacked in a manner of 8 layers of prepreg and 1 layer of copper alloy to form a laminate (fiber volume fraction 60%), and then cut into a rectangular thermoplastic composite hybrid metal sandwich structure;

[0047] The prepared rectangular thermoplastic composite material mixed metal sandwich structure preform is placed in a mold; a mold release agent is applied between the mold and the preform; the hot press parameters are 270°C / 10MPa; and a thermoplastic composite material and metal mixed structure rivet is formed by a hot pressing molding process;

[0048] The manufactured rivets are clamped by a riveting machine, and high-frequency alternating current is passed through the coil in the rivet gun. After 10s-60s, the rivets reach the working temperature and are pressed into the prefabricated holes at the joints of the composite panels. After that, they come into contact with the rivet lower mold coated with a release agent to form a pier head to complete the fastening.

[0049] Example 3

[0050] Prepare titanium thin layer, carbon fiber reinforced PEEK unidirectional prepreg (Toray T300);

[0051] A rectangular thermoplastic composite hybrid metal sandwich structure was made by laying carbon fiber reinforced PEEK unidirectional prepreg and titanium alloy thin layers (fiber volume fraction 60%);

[0052] The thermoplastic composite material and metal hybrid sandwich structure preform is placed in a mold; a mold release agent is applied between the mold and the preform; the hot press parameters are 390°C / 10MPa; and a thermoplastic composite material and metal hybrid structure rivet is formed by a hot pressing molding process;

[0053] The manufactured rivets are clamped by a riveting machine, and high-frequency alternating current is passed through the coil in the rivet gun. After 10s-20s, the rivets reach the working temperature and are pressed into the prefabricated holes at the joints of the composite plate and the metal plate. After that, they come into contact with the rivet lower die coated with a release agent to form a pier head to complete the fastening.

[0054] Example 4

[0055] Prepare copper alloy mesh, carbon fiber polyamide unidirectional prepreg (T800);

[0056] The carbon fiber polyamide unidirectional prepreg is wound in a stacking manner of 8 layers of prepreg and 1 layer of aluminum alloy mesh (fiber volume fraction 60%) to form a cylindrical thermoplastic composite hybrid metal sandwich structure;

[0057] The cylindrical thermoplastic composite material mixed metal sandwich structure preform is placed in a mold; a mold release agent is applied between the mold and the preform; the hot press parameters are 270°C / 10MPa; and a thermoplastic composite material and metal mixed structure rivet is formed by a hot pressing molding process;

[0058] The manufactured rivets are clamped by a riveting machine, and high-frequency alternating current is passed through the coil in the rivet gun. After 20s-30s, the rivets reach the working temperature and are pressed into the prefabricated holes at the joints of the composite panels. After that, they come into contact with the rivet lower mold coated with a release agent to form a pier head to complete the fastening.

[0059] Example 5

[0060] A titanium alloy thin layer and a carbon fiber reinforced PPS unidirectional prepreg (T800) are prepared; the carbon fiber reinforced PPS unidirectional prepreg is laid in a stacking manner of 8 layers of prepreg and 1 layer of titanium alloy thin layer (fiber volume fraction 60%); the laid thermoplastic composite metal sandwich structure is made into a thermoplastic composite metal sandwich structure plate in a mold by a hot press (parameter 320°C / 5MPa); the prepared composite plate is processed and exploited to make a thermoplastic composite hybrid metal sandwich preform structure;

[0061] The thermoplastic composite material and metal hybrid sandwich structure preform is placed in a mold; a mold release agent is applied between the mold and the preform; the hot press parameters are 320°C / 10MPa; and a thermoplastic composite material and metal hybrid structure rivet is formed by a hot pressing molding process;

[0062] The manufactured rivets are clamped by a riveting machine, and high-frequency alternating current is passed through the coil in the rivet gun. After 20s-30s, the rivets reach the working temperature and are pressed into the prefabricated holes at the joints of the composite panels. After that, they come into contact with the rivet lower mold coated with a release agent to form a pier head to complete the fastening.

Claims

1. A method for manufacturing and self-heating riveting rivets of thermoplastic composite materials and metal hybrid structures, characterized in that: The following steps are involved: Step 1) Preparation of thermoplastic composite material and metal hybrid structure rivets: Step 1.1): The thermoplastic carbon fiber prepreg is laminated and wound around a metal induction heating medium, and then placed in a rod pressing mold, and a rod-shaped blank is formed by a radial molding mold; or a composite material and a metal medium are laminated and molded to form a composite material and metal mixed laminate, and then a rectangular or round rod-shaped blank is formed by machining; Step 1.2): Compression molding of rivets: placing the blank in a detachable rivet compression molding mold, placing a release agent between the mold and the bar material to facilitate demolding, and compression molding to obtain a thermoplastic composite material and metal hybrid structure rivet; Step 1.3): Subsequent processing and heat treatment of rivets: The manufactured thermoplastic composite material and metal hybrid structure rivets are machined to grind off edge burrs and excess resin, and then annealed and tempered heat treatment is performed as needed; Step 2), self-heating riveting of thermoplastic composite material and metal hybrid structure rivets: Step 2.1): Preparation and positioning of the composite material or metal parts to be connected: holes are made in the composite material or metal sheet to be connected by machining, and the holes are placed on the riveting platform for overlapping positioning; Step 2.2): Rivet clamping: clamp the thermoplastic composite material and metal hybrid structure rivet into the riveting equipment, adjust the position and direction of the rivet, ensure that the rivet is placed in the center of the induction current heating coil and the rivet is vertically downward, and prepare for riveting; Step 2.3): Press riveting: Start the induction current heating riveting equipment. After the induction heating lasts for 1 to 60 seconds, the rivet reaches the preset temperature and automatically completes the pressing operation. The rivet is pressed into the prefabricated through hole of the two plates. The rivet contacts the lower die to complete the pressing. After the upper plate stops moving, a constant pressure value is maintained and the pressure is maintained. After cooling, the plate connection is completed. Step 2.4): Check the riveted structure: First, visually inspect the integrity and surface defects of the riveted structure, and then detect the internal defects of the riveted structure through non-destructive testing.

2. The method for manufacturing and self-heating riveting of thermoplastic composite material and metal hybrid structure rivets according to claim 1, characterized in that: In the step 1.1), the raw materials of the thermoplastic carbon fiber prepreg include resin powder material and carbon fiber raw material.

3. The method for manufacturing and self-heating riveting of thermoplastic composite material and metal hybrid structure rivets according to claim 2, characterized in that: The resin powder material is at least one of polyamide-6, polyetheretherketone and polyphenylene sulfide.

4. The method for manufacturing and self-heating riveting of thermoplastic composite material and metal hybrid structure rivets according to claim 2, characterized in that: The carbon fiber raw material is at least one of unidirectional carbon fiber prepreg and carbon fiber fabric.

5. The method for manufacturing and self-heating riveting of thermoplastic composite material and metal hybrid structure rivets according to claim 1, characterized in that: In the step 1.1), the specification of the metal induction heating medium is at least one of round rod, layer, mesh, and particle.

6. The method for manufacturing and self-heating riveting of thermoplastic composite material and metal hybrid structure rivets according to claim 1, characterized in that: In the step 1.1), the mixed structure of the blank is an alternating laminated structure; the volume percentage of the carbon fiber raw material in the blank is 40%-65%.

7. The method for manufacturing and self-heating riveting of thermoplastic composite material and metal hybrid structure rivets according to claim 1, characterized in that: In the step 2.3), the parameters of the induction current heating riveting equipment are adjusted according to the material and structure of the rivet, and the parameters of the riveting equipment include heating power, riveting pressure, speed, and holding time.

8. The method for manufacturing and self-heating riveting of thermoplastic composite material and metal hybrid structure rivets according to claim 1, characterized in that: In the step 2.3), the holding time is 1-10s.

9. The method for manufacturing and self-heating riveting of thermoplastic composite material and metal hybrid structure rivets according to claim 1, characterized in that: In the step 2.3), the prefabricated through holes on the two plates are reserved when the plates are prepared or obtained by drilling, and the method of connecting the thermoplastic composite material and metal hybrid structure rivets to the two plates is: connecting one of the composite material and the composite material structure, the composite material and the metal structure, and the metal and the metal structure.

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