A method for welding carbon fiber composite material and metal

Abstract

The present invention relates to a method for welding a carbon fiber composite material to a metal, comprising the following steps: (1) machining a hole on a wall surface of a metal part to be connected, wherein the hole has a large interior and a small opening, and a burr is formed on the wall surface of the metal part to be connected at the periphery of the hole, wherein the free end of the burr extends away from the hole to form a hook portion; (2) preparing a connecting piece: impregnating a carbon fiber structure with a molten thermoplastic resin until a portion of the carbon fiber structure is exposed to form a connecting portion connected to the hole, wherein the connecting portion includes an inserting portion and a hooking portion, inserting the inserting portion into the hole, and connecting the hooking portion to the hook portion; (3) welding the connecting piece to the metal part; and (4) welding the connecting piece to the carbon fiber composite material. The connection strength is high.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber composite material / metal structural component preparation, and in particular to a method for welding a carbon fiber composite material and metal. Background Art

[0002] Carbon fiber composites (CFRP) boast a range of excellent properties, including light weight and high strength, and play a vital role in the development of national defense technology, weaponry, civil aviation, and mechanical transportation. In particular, they are widely used in weaponry requiring lightweighting, such as rockets, aircraft, vehicles, and missiles, and their use is steadily increasing. Furthermore, metal alloys remain the primary lightweight material. The composite connection of metal and carbon fiber composites can fully leverage the respective advantages of both materials, and is also a key requirement for the manufacture of complex engineering components and the integration of product structure and function.

[0003] For example, the Chinese invention patent application with patent application number CN202110651478.0 (publication number CN113399826A) discloses a method for laser welding of thermosetting composite materials to metals. (1) micro-textures are prepared on the metal surface; (2) laser cleaning is performed on the surface of the thermosetting composite material; (3) a thermoplastic resin layer is added between the metal and the thermosetting composite material; and (4) laser heat conduction welding is used to achieve connection between the two.

[0004] This patent prepares a microstructure on the metal surface, the purpose of which is to connect the thermoplastic resin layer to the microstructure by melting it to improve the connection strength between the two. However, the connection strength of this connection method needs to be further improved.

[0005] In addition, this patent requires the use of a short-pulse laser to perform laser cleaning processing on the surface of the thermosetting composite material until the surface resin is removed and the carbon fiber is exposed, which may cause thermal damage to the surface of the thermosetting composite material.

[0006] In addition, this patent achieves connection with thermosetting composite materials by melting and solidifying the thermoplastic resin layer, but the physical and chemical properties of the two materials are different, and stress concentration is easily generated during the connection process, resulting in a decrease in the mechanical properties of the overall structure. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a welding method for carbon fiber composite materials and metals with high connection strength in view of the above-mentioned prior art.

[0008] The technical solution adopted by the present invention to solve the above technical problems is: a method for welding carbon fiber composite materials and metal, characterized in that it includes the following steps:

[0009] (1) machining a hole on the wall surface of the metal parts to be connected, wherein the hole has a large interior and a small opening, and a burr is formed on the wall surface of the metal parts to be connected at the periphery of the hole, and the free end of the burr extends in a direction away from the hole to form a hook;

[0010] (2) Preparing a connecting part: Melting a thermoplastic resin and impregnating it on the carbon fiber structure until a portion of the carbon fiber structure is exposed to form a connecting portion connected to the hole, wherein the connecting portion includes an inserting portion and a hooking portion, inserting the inserting portion into the hole, and connecting the hooking portion to the hook portion;

[0011] (3) Welding the connector to the metal part;

[0012] (4) Welding the connecting parts to the carbon fiber composite material.

[0013] Currently, there is no existing technology that studies the shape of holes. Existing holes are generally of equal diameter or circular pit-shaped holes with a small interior and a large opening. If the hole shape is not appropriate, the components inside are easy to separate, resulting in a loose connection between the components. In addition, some hole shapes have high stress. Therefore, preferably, the hole is in the shape of a teardrop. The present application uses a special processing technology to form a teardrop-shaped hole with a large interior and a small opening. Compared with the existing hole shape, it helps to better lock the plug-in part of the connector, combine with the thermoplastic resin material of the connector to form a locking tooth structure, and form a mechanical interlock. In addition, the rounded shape of the teardrop-shaped hole can reduce stress concentration and improve the fatigue life of the material.

[0014] In order to process the above-mentioned teardrop-shaped holes and form burrs around the holes, in the step (1), holes and burrs are formed by laser processing on the wall surface of the metal parts to be connected. During the processing, it is divided into two processes. The first process forms a tapered hole with a larger top and a smaller bottom on the metal plate, and then the second process continues laser processing in the tapered hole until a teardrop-shaped hole is formed. The number of scans in each process is 5-30 times, the pulse frequency is 20-100kHz, and the scanning speed is 0.5-1.0m / s. The power used in the first process is greater than the power used in the second process. The power of the two processes is between 10-100W. The processing technology of teardrop-shaped holes is relatively complicated. Due to the characteristics of pulsed laser processing, it is difficult to process a shape with a large interior and a small opening by simply adjusting the parameters. Because of the energy characteristics of the pulsed laser and the principle of interaction with the material, simply adjusting the energy size can only increase the depth of the hole, forming a circular hole or a conical shape. The present invention dynamically adjusts the processing power, first using high power to form a tapered hole with a larger top and a smaller bottom, and then continues low power processing. At this time, the molten metal material will accumulate in the tapered hole, and finally a teardrop-shaped hole will be processed.

[0015] Preferably, in step (3), the connector and the metal part are welded by stir friction welding, and the welding process parameters are: rotation speed 900-2000r / min, welding speed 60-100mm / min, and downward pressure 0.1-0.3mm, so that the thermoplastic resin of the connector and the metal part are firmly connected.

[0016] Preferably, in step (4), the connector and the carbon fiber composite material are welded by friction stir welding, and the welding process parameters are: rotation speed 500-1200 r / min, welding speed 10-40 mm / min, and downward pressure 0.1-0.3 mm, so that the thermoplastic resin of the connector and the carbon fiber composite material are firmly connected.

[0017] Preferably, in step (2), the carbon fiber structure is a woven structure having a plurality of U-shaped wire bundles and threads extending from the two free ends of the wire bundles in a direction away from the wire bundles, a positioning portion for another wire bundle to be hooked thereon is formed between the wire bundles and the threads, part of the threads are located outside the thermoplastic resin to form an insertion portion, and part of the wire bundle is located outside the thermoplastic resin to form a hooking portion. The carbon fiber structure of the present application is designed as a woven structure of this type of plush tissue structure, which can better absorb and disperse impact energy and improve the material's impact resistance and fatigue resistance; the woven structure has a stronger interlayer bonding force, which can enhance the interlayer shear strength of the connection and better anti-delamination performance.

[0018] Preferably, in step (2), the molten thermoplastic resin is infiltrated into and impregnated into the carbon fiber structure by melt impregnation to obtain a connector, and the process parameters of the melt impregnation are: pulling speed: 1.0-2.0m / min, impregnation temperature 200-500℃, impregnation roller radius 8mm, and impregnation pressure 2-15Mpa.

[0019] Preferably, the metal part is one of stainless steel, high-strength steel, high-temperature alloy, aluminum alloy, magnesium alloy or titanium alloy.

[0020] Preferably, the thermoplastic resin is at least one of polypropylene (PP), polyamide (PA), polycarbonate (PC), polyetherketone (PEK), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), and polyoxymethylene (POM).

[0021] To further enhance the connection strength, the carbon fiber composite material is a composite of at least two materials, one of which is the same as the thermoplastic resin. Because the connector's matrix material (thermoplastic resin) is the same as one of the carbon fiber composite materials, this avoids reducing the connection strength between the connector and the carbon fiber composite material due to differences in physical and chemical properties.

[0022] Compared with the prior art, the advantages of the present invention are: the present application provides a connecting piece, and the connecting piece has a carbon fiber structure, which can be directly welded to the carbon fiber composite material without processing the carbon fiber composite material, thereby avoiding the problem of damaging the carbon fiber composite material;

[0023] The present application processes holes and burrs on a metal part, and a plug-in portion and a hooking portion on the connector. The plug-in portion is inserted into the hole, and the hooking portion is connected to the hook portion. The connection mechanism of this connection method is as follows: the plug-in portion enters the hole on the surface of the metal part similar to the connection between hair and hair follicles. The carbon fiber implantation can greatly enhance the connection force, and the inside of the hole is large and the opening is small, so the plug-in portion is not easy to detach from the hole. At the same time, the burrs around the hole on the surface of the metal part are similar to the hooks connected to the cocklebur, and the hooking portion connected to the connector can further enhance the bonding strength between the two. The burrs can be embedded in the cured thermoplastic resin, playing a role similar to a pin (burr bridging), which can improve the connection strength. In other words, during the connection process, part of the thermoplastic resin fills the hole in the metal part, forming a locking tooth structure similar to the elytra of the ironclad beetle, which can improve the connection strength between the components and increase toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the carbon fiber structure;

[0025] Figure 2 A diagram of an apparatus for melt impregnation of a carbon fiber structure and a thermoplastic resin;

[0026] Figure 3 It is a schematic diagram of the connection between the connector and the metal part;

[0027] Figure 4 Schematic diagram of a tapered hole. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0029] Example 1

[0030] The method for welding carbon fiber composite material and metal in this embodiment includes the following steps:

[0031] (1) processing a hole on the wall surface of the metal parts to be connected, wherein the hole is large inside and small at the opening, and is shaped like a water droplet. A burr is formed on the wall surface of the metal parts to be connected around the hole, and the free end of the burr extends away from the hole to form a hook portion;

[0032] Holes and burrs are formed by laser processing. During processing, the process is divided into two steps with high power 30W and low power 10W. First, scan 25 times at 30W power to form a tapered hole with a larger top and a smaller bottom (see Figure 4 The shape of the sample was obtained by scanning 17 times at a power of 10W to produce teardrop-shaped holes and burrs. The pulse frequency of the two processes was 100kHz and the scanning speed was 0.5m / s.

[0033] (2) Preparation of connectors: Melt the thermoplastic resin and impregnate it on the carbon fiber structure until the carbon fiber structure is partially exposed to form a connection part connected to the hole. The connection part includes an inserting part and a hooking part. The inserting part is inserted into the hole and the hooking part is connected to the hook part. This part of the connection can be referred to Figure 3 , Figure 3 In the figure, number 3 is a thermoplastic resin, number 4 is a metal part, number 5 is a hole, number 6 is a hook, number 7 is an insertion part, number 8 is a connecting part, number a is a schematic diagram of the insertion part inserted in the hole, similar to the connection between hair and hair follicles; number b is a schematic diagram of the connecting part connected to the hook, and number c is a schematic diagram of the shape of the hole, similar to the elytra of a beetle.

[0034] The carbon fiber structure is a woven structure with multiple U-shaped wire bundles and wires extending from the two free ends of the wire bundles in the direction away from the wire bundles. A positioning portion is formed between the wire bundles for another wire bundle to hook on. Some wires are located outside the thermoplastic resin to form an insertion portion, and some wire bundles are located outside the thermoplastic resin to form a hooking portion. Figure 1 , Figure 1 The number 1 is the wire harness, and the number 2 is the silk thread.

[0035] The melt impregnation method is used to allow the molten thermoplastic resin to penetrate and impregnate the carbon fiber structure to obtain a connector. The process parameters of the melt impregnation are: pulling speed: 1.0m / min, impregnation temperature 420℃, impregnation roller radius 8mm, impregnation pressure 12MPa. The melt impregnation process can be referred to Figure 2 , the carbon fiber structure and thermoplastic resin are extruded together through rollers.

[0036] (3) Welding the connecting part to the metal part, specifically, welding the thermoplastic resin and the metal part by stir friction welding, and the welding process parameters are: rotation speed 1000r / min, welding speed 70mm / min, and downward pressure 0.2mm.

[0037] (4) The connecting parts are welded to the carbon fiber composite material, and the thermoplastic resin and the carbon fiber composite material are welded by stir friction welding. The welding process parameters are: rotation speed 1000r / min, welding speed 20mm / min, and downward pressure 0.1mm.

[0038] In this embodiment, the metal member is aluminum alloy 6061; the thermoplastic resin is PEEK; and the carbon fiber composite material is a carbon fiber reinforced polyetheretherketone composite material (CF / PEEK).

[0039] This embodiment uses a carbon fiber reinforced polyetheretherketone composite material CF / PEEK with dimensions of 80mm×25mm×3mm, an aluminum alloy with dimensions of 80mm×25mm×1.5mm, and a connection area of ​​25mm×10mm. The tensile shear test shows that the tensile shear force is 4211.9N and the tensile shear strength is 16.8MPa.

[0040] As a comparative test, we used a simple texturing aluminum alloy 6061 plate to connect with a carbon fiber reinforced polyetheretherketone composite material CF / PEEK. The tensile shear force of the comparative example was 3749.1N, and the tensile shear strength was 14.99MPa. The tensile shear strength of the embodiment was improved by about 12% compared with the comparative example.

[0041] Example 2

[0042] The method for welding carbon fiber composite material and metal in this embodiment includes the following steps:

[0043] (1) processing a hole on the wall surface of the metal parts to be connected, wherein the hole is large inside and has a small opening in the shape of a water drop, and a burr is formed on the wall surface of the metal parts to be connected at the periphery of the hole, and the free end of the burr extends in a direction away from the hole to form a hook;

[0044] Holes and burrs are formed by laser processing. During processing, the process is divided into two steps with high power 70W and low power 35W. First, scan 12 times at 70W power to form a tapered hole with a larger top and a smaller bottom (see Figure 4 The shape of the image is then scanned 12 times at a power of 35W to produce teardrop-shaped holes and burrs. The pulse frequency of the two processes is 80kHz and the scanning speed is 0.8m / s.

[0045] (2) Preparation of connectors: Melt the thermoplastic resin and impregnate it on the carbon fiber structure until the carbon fiber structure is partially exposed to form a connection part connected to the hole. The connection part includes an inserting part and a hooking part. The inserting part is inserted into the hole and the hooking part is connected to the hook part. This part of the connection can be referred to Figure 3 , Figure 3 In the figure, number 3 is a thermoplastic resin, number 4 is a metal part, number 5 is a hole, number 6 is a hook part, number 7 is an inserting part, and number 8 is a hooking part.

[0046] The carbon fiber structure is a woven structure with multiple U-shaped wire bundles and wires extending from the two free ends of the wire bundles in the direction away from the wire bundles. A positioning portion is formed between the wire bundles for another wire bundle to hook on. Some wires are located outside the thermoplastic resin to form an insertion portion, and some wire bundles are located outside the thermoplastic resin to form a hooking portion. Figure 1 , Figure 1 The number 1 is the wire harness, and the number 2 is the silk thread.

[0047] The melt impregnation method is used to allow the molten thermoplastic resin to penetrate and impregnate the carbon fiber structure to obtain the connector. The process parameters of the melt impregnation are: pulling speed: 1.5m / min, impregnation temperature 350℃, impregnation roller radius 8mm, impregnation pressure 8MPa. The melt impregnation process can be referred to Figure 2 , the carbon fiber structure and thermoplastic resin are extruded together through rollers.

[0048] (3) Welding the connecting part to the metal part, specifically, welding the thermoplastic resin and the metal part by stir friction welding, and the welding process parameters are: rotation speed 2000r / min, welding speed 100mm / min, and downward pressure 0.3mm.

[0049] (4) The connecting parts are welded to the carbon fiber composite material, and the thermoplastic resin and the carbon fiber composite material are welded by stir friction welding. The welding process parameters are: rotation speed 1200r / min, welding speed 40mm / min, and downward pressure 0.2mm.

[0050] In this embodiment, the metal member is aluminum alloy 6061; the thermoplastic resin is PPS; and the carbon fiber composite material is a carbon fiber reinforced polyphenylene sulfide composite material (CF / PPS).

[0051] In this embodiment, the carbon fiber reinforced polyphenylene sulfide composite material (CF / PPS) is selected with a size of 100 mm × 25 mm × 3 mm, the aluminum alloy is sized 100 mm × 25 mm × 2 mm, and the connection area is 25 mm × 9 mm. The tensile shear test shows that the tensile shear force is 2875.4 N and the tensile shear strength is 12.8 MPa.

[0052] As a comparative test, we used a smooth 6061 plate to connect with a carbon fiber reinforced polyphenylene sulfide composite material (CF / PPS). The tensile shear force of the comparative example was 2174.7N and the tensile shear strength was 9.7MPa. The tensile shear strength of the embodiment was improved by about 32% compared with the comparative example.

[0053] Example 3

[0054] The method for welding carbon fiber composite material and metal in this embodiment includes the following steps:

[0055] (1) processing a hole on the wall surface of the metal parts to be connected, wherein the hole is large inside and small at the opening, and is shaped like a water droplet. A burr is formed on the wall surface of the metal parts to be connected around the hole, and the free end of the burr extends away from the hole to form a hook portion;

[0056] Holes and burrs are formed by laser processing. During processing, the process is divided into two steps with high power 100W and low power 40W. First, scan 5 times at 100W power to form a tapered hole with a larger top and a smaller bottom (see Figure 4 The shape of the image is obtained by scanning 8 times at a power of 40W, and then a teardrop-shaped hole and burrs are generated. The pulse frequency of the two processes is 20kHz and the scanning speed is 1.0m / s.

[0057] (2) Preparation of connectors: Melt the thermoplastic resin and impregnate it on the carbon fiber structure until the carbon fiber structure is partially exposed to form a connection part connected to the hole. The connection part includes an inserting part and a hooking part. The inserting part is inserted into the hole and the hooking part is connected to the hook part. This part of the connection can be referred to Figure 3 , Figure 3 In the figure, number 3 is a thermoplastic resin, number 4 is a metal part, number 5 is a hole, number 6 is a hook part, number 7 is an inserting part, and number 8 is a hooking part.

[0058] The carbon fiber structure is a woven structure with multiple U-shaped wire bundles and wires extending from the two free ends of the wire bundles in a direction away from the wire bundles. The wire bundles form a connection portion for another wire bundle to be hooked on. Some of the wires are located outside the thermoplastic resin to form an insertion portion, and some of the wire bundles are located outside the thermoplastic resin to form a hooking portion. Figure 1 , Figure 1 The number 1 is the wire harness, and the number 2 is the silk thread.

[0059] The melt impregnation method is used to allow the molten thermoplastic resin to penetrate and impregnate the carbon fiber structure to obtain a connector. The process parameters of the melt impregnation are: pulling speed: 2.0m / min, impregnation temperature 210℃, impregnation roller radius 8mm, impregnation pressure 3MPa. The melt impregnation process can be referred to Figure 2 , the carbon fiber structure and thermoplastic resin are extruded together through rollers.

[0060] (3) Welding the connecting part to the metal part, specifically, welding the thermoplastic resin and the metal part by stir friction welding, and the welding process parameters are: rotation speed 900r / min, welding speed 100mm / min, and downward pressure 0.3mm.

[0061] (4) The connecting parts are welded to the carbon fiber composite material, and the thermoplastic resin and the carbon fiber composite material are welded by stir friction welding. The welding process parameters are: rotation speed 500r / min, welding speed 10mm / min, and downward pressure 0.3mm.

[0062] In this embodiment, the metal member is aluminum alloy 6061; the thermoplastic resin is PA66; and the carbon fiber composite material is a carbon fiber reinforced polyamide composite material (CF / PA66).

[0063] This embodiment uses carbon fiber reinforced polyamide composite material (CF / PA66) with dimensions of 100mm×25mm×3mm, aluminum alloy dimensions of 100mm×25mm×2mm, and a connection area of ​​25mm×10mm. The tensile shear test shows that the tensile shear force is 1684.4N and the tensile shear strength is 6.8MPa.

[0064] As a comparative test, we used a smooth 6061 plate to connect with a carbon fiber reinforced polyamide composite material (CF / PA66). The tensile shear force of the comparative example was 1218.3N and the tensile shear strength was 4.9MPa. The tensile shear strength of the embodiment was improved by about 38% compared with the comparative example.

[0065] The weaving method of the carbon fiber structure of the present application adopts a sliver-fed long-pile weaving process, which is a prior art. For reference, the book "Knitting (2nd Edition)" edited by Long Hairu of China Textile Press Co., Ltd., ISBN: 9787518007974, published on August 1, 2014, can be used.

Claims

1. A method for welding carbon fiber composite materials to metal, characterized in that: The steps include: (1) machining a hole on the wall surface of the metal parts to be connected, wherein the hole has a large interior and a small opening, and a burr is formed on the wall surface of the metal parts to be connected at the periphery of the hole, and the free end of the burr extends in a direction away from the hole to form a hook; (2) Preparing a connecting part: Melting a thermoplastic resin and impregnating it on the carbon fiber structure until a portion of the carbon fiber structure is exposed to form a connecting portion connected to the hole, wherein the connecting portion includes an inserting portion and a hooking portion, inserting the inserting portion into the hole, and connecting the hooking portion to the hook portion; (3) Welding the connector to the metal part; (4) Welding the connecting parts to the carbon fiber composite material.

2. The method for welding carbon fiber composite materials to metal according to claim 1, characterized in that: The hole is in the shape of a water drop.

3. The method for welding carbon fiber composite material to metal according to claim 2, characterized in that: In the step (1), holes and burrs are formed by laser processing on the wall surface to be connected of the metal parts. During the processing, it is divided into two processes. The first process forms a conical hole with a larger top and a smaller bottom on the metal plate, and then the second process continues the laser processing in the conical hole until a teardrop-shaped hole is formed. The number of scans in each process is 5-30 times, the pulse frequency is 20-100kHz, and the scanning speed is 0.5-1.0m / s. The power used in the first process is greater than the power used in the second process. The power of the two processes is between 10-100W.

4. The method for welding carbon fiber composite material to metal according to claim 1, characterized in that: In the step (3), the connecting piece and the metal piece are welded by friction stir welding, and the welding process parameters are: rotation speed 900-2000 r / min, welding speed 60-100 mm / min, and downward pressure 0.1-0.3 mm.

5. The method for welding carbon fiber composite material to metal according to claim 1, characterized in that: In the step (4), the connector and the carbon fiber composite material are welded by friction stir welding, and the welding process parameters are: rotation speed 500-1200 r / min, welding speed 10-40 mm / min, and downward pressure 0.1-0.3 mm.

6. The method for welding carbon fiber composite material to metal according to claim 1, wherein: In step (2), the carbon fiber structure is a woven structure having a plurality of U-shaped wire bundles and silk threads extending from two free ends of the wire bundles in a direction away from the wire bundles, a positioning portion for another wire bundle to be hooked thereon is formed between the wire bundles and the silk threads, part of the silk threads are located outside the thermoplastic resin to form an insertion portion, and part of the wire bundles are located outside the thermoplastic resin to form a hooking portion.

7. The method for welding carbon fiber composite material to metal according to claim 6, characterized in that: In the step (2), the molten thermoplastic resin is infiltrated into and impregnated into the carbon fiber structure by melt impregnation to obtain a connector. The process parameters of the melt impregnation are: pulling speed: 1.0-2.0m / min, impregnation temperature 200-500°C, impregnation roller radius 8mm, and impregnation pressure 2-15Mpa.

8. The method for welding carbon fiber composite material to metal according to claim 1, characterized in that: The metal part is one of stainless steel, high-strength steel, high-temperature alloy, aluminum alloy, magnesium alloy or titanium alloy.

9. The method for welding carbon fiber composite material to metal according to claim 1, characterized in that: The thermoplastic resin is at least one of PP, PA, PC, PEK, PEEK, PPS, and POM.

10. The method for welding a carbon fiber composite material to a metal according to any one of claims 1 to 9, characterized in that: The carbon fiber composite material is a composite of at least two materials, and one of the materials in the carbon fiber composite material is the same as the material of the thermoplastic resin.

Images