Welding method for carbon fiber composite material and metal

Abstract

The invention relates to a welding method of a carbon fiber composite material and metal, which comprises the following steps: (1) a hole is processed on a to-be-connected wall surface of a metal piece, the interior of the hole is large, the opening of the hole is small, burrs are formed on the periphery of the hole on the to-be-connected wall surface of the metal piece, and the free end of each burr extends towards the direction far away from the hole to form a hook part; (2) a connecting piece is prepared, specifically, thermoplastic resin is molten and impregnated on the carbon fiber structure until the carbon fiber structure is partially exposed to form a connecting part connected with the hole, the connecting part comprises an inserting part and a hooking part, the inserting part is inserted into the hole, and the hooking part is connected with the hooking part; (3) welding the connecting piece and the metal piece; and (4) welding the connecting piece and the carbon fiber composite material. The connection strength is high.

Description

Technical Field

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

[0002] Carbon fiber composite materials (CFRP) have a series of excellent properties such as light weight and high strength, and play an extremely important role in the development of national defense science and technology, weapons and equipment, civil aviation, mechanical transportation and other fields. In particular, carbon fiber composite materials are widely used in rockets, aircraft, vehicles, missiles and other weapons and equipment with lightweight requirements, and the trend is gradually increasing. In addition, metal alloys are still the main lightweight materials at present. The composite connection of metal and carbon fiber composite materials can give full play to the respective advantages of metal materials and carbon fiber composite materials. It is also an important requirement for the manufacturing 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) the surface of the thermosetting composite material is laser cleaned; (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 melt the thermoplastic resin layer and connect it to the microstructure to improve the firmness of the connection between the two. In this connection method, the connection strength needs to be further improved;

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

[0006] In addition, this patent achieves connection with thermosetting composite materials by melting and solidifying the thermoplastic resin layer, but the two materials have different physical and chemical properties, 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 problem is: a method for welding carbon fiber composite material and metal, characterized in that it includes the following steps:

[0009] (1) processing 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: impregnating a thermoplastic resin into the carbon fiber structure until a part of the carbon fiber structure is exposed to form a connecting part connected to the hole, wherein the connecting part includes an inserting part and a hooking part, inserting the inserting part into the hole, and connecting the hooking part to the hook part;

[0011] (3) Welding the connecting parts to the metal parts;

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

[0013] There is no prior art that studies the shape of holes. Existing holes are generally round holes with equal diameters or small inside and large openings. If the hole shape is not appropriate, the parts inside are easy to separate, resulting in loose connections between parts. In addition, the stress of holes of some shapes is relatively large. Therefore, preferably, the hole is in the shape of a water drop. The present application forms a water drop-shaped hole with a large inside and a small opening through a special processing technology. Compared with the existing hole shape, it helps to better lock the plug-in part of the connector, and combines with the thermoplastic resin material of the connector to form a locking tooth structure, forming a mechanical interlocking; in addition, the rounded shape of the water drop-shaped hole can reduce stress concentration and improve the fatigue life of the material.

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

[0015] Preferably, in step (3), the connecting piece and the metal piece 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 connecting piece is firmly connected to the metal piece.

[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 500-1200r / min, welding speed 10-40mm / min, and downward pressure 0.1-0.3mm, 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 silk 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 on 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. The carbon fiber structure of the present application is designed as a woven structure of such a plush tissue structure, which can better absorb and disperse impact energy and improve the impact resistance and fatigue resistance of the material; the interlayer bonding force of the woven structure is stronger, which can enhance the interlayer shear strength of the connection and has better anti-delamination performance.

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

[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] In order to further improve the connection strength, 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. Since the matrix material (thermoplastic resin) of the connector is the same as one of the materials in the carbon fiber composite material, the difference in physical and chemical properties between the materials that reduces the connection strength between the connector and the carbon fiber composite material is avoided.

[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 the metal part, and the connector has an inserting part and a hooking part, the inserting part is inserted in the hole, and the hooking part is connected to the hook part. The connection mechanism of this connection method is: the inserting part enters the hole on the surface of the metal part similar to the connection between hair and hair follicles, and the carbon fiber implantation can greatly enhance the connection force, and the hole is large inside and the opening is small, and the inserting part 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 part hooked on the connector can further enhance the bonding strength between the two, and the burrs can be embedded in the cured thermoplastic resin, playing a role similar to that of a pin (burr bridging), which can improve the connection strength. In other words, during the connection process, part of the thermoplastic resin is filled into the hole of the metal part, forming a locking tooth structure similar to that in the elytra of the iron 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 is further described in detail below with reference to the accompanying drawings.

[0029] Example 1

[0030] The welding method of the carbon fiber composite material and the metal of the present embodiment comprises 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 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;

[0032] Holes and burrs are formed by laser processing. During processing, the processing 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 large top and a small bottom (see Figure 4 The shape of the sample is then scanned 17 times at a power of 10 W to produce teardrop-shaped holes and burrs. The pulse frequency of the two processes is 100 kHz and the scanning speed is 0.5 m / s.

[0033] (2) Preparation of the connector: 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 insertion part and a hooking part. The insertion part is inserted into the hole, and the hooking part is connected to the hook part. This part of the connection can refer to Figure 3 , Figure 3 In the middle, 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 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 part, 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 a direction away from the wire bundles. A positioning portion is formed between the wire bundles for another wire bundle to hook 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. The carbon fiber woven structure can be referred to Figure 1 , Figure 1 The number 1 is the wire harness, and the number 2 is the silk thread.

[0035] The molten thermoplastic resin is infiltrated into the carbon fiber structure by melt impregnation to obtain the connector. The process parameters of melt impregnation are: traction 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 formed together through roller extrusion.

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

[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 part 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 a size of 80mm×25mm×3mm, an aluminum alloy size 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 roughened 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 welding method of the carbon fiber composite material and the metal of the present embodiment comprises 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 small at the opening and is 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 processing 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 large top and a small bottom (see Figure 4 The shape of the water droplet 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 the connector: 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 insertion part and a hooking part. The insertion part is inserted into the hole, and the hooking part is connected to the hook part. This part of the connection can refer 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 a direction away from the wire bundles. A positioning portion is formed between the wire bundles for another wire bundle to hook 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. The carbon fiber woven structure can be referred to Figure 1 , Figure 1 The number 1 is the wire harness, and the number 2 is the silk thread.

[0047] The molten thermoplastic resin is infiltrated into the carbon fiber structure by melt impregnation to obtain the connector. The process parameters of 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 formed together through roller extrusion.

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

[0049] (4) The connecting parts are welded to the carbon fiber composite material. 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 100mm×25mm×3mm, the aluminum alloy is sized 100mm×25mm×2mm, and the connection area is 25mm×9mm. The tensile shear test shows that the tensile shear force is 2875.4N and the tensile shear strength is 12.8MPa.

[0052] As a comparative test, we used a smooth 6061 plate to connect with a carbon fiber reinforced polyphenylene sulfide composite material (CF / PPS), and 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 welding method of the carbon fiber composite material and the metal of the present embodiment comprises 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 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;

[0056] Holes and burrs are formed by laser processing. During processing, the processing 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 large top and a small bottom (see Figure 4 The shape of the water droplet is then scanned 8 times at a power of 40W to produce teardrop-shaped holes and burrs. The pulse frequency of the two processes is 20kHz and the scanning speed is 1.0m / s.

[0057] (2) Preparation of the connector: 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 insertion part and a hooking part. The insertion part is inserted into the hole, and the hooking part is connected to the hook part. This part of the connection can refer 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 and the wires form a connection portion for another wire bundle to hook 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 molten thermoplastic resin is infiltrated into the carbon fiber structure by melt impregnation to obtain the connector. The process parameters of 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 formed together through roller extrusion.

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

[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 part 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 a carbon fiber reinforced polyamide composite material (CF / PA66) with a size of 100mm×25mm×3mm, an aluminum alloy with a size 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), and 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 wool-feeding long-pile tissue weaving process, which is a prior art. The reference book is: Knitting (2nd Edition) edited by Long Hairu of China Textile Publishing House Co., Ltd., ISBN: 9787518007974, published on August 1, 2014.

Claims

1. A method for welding a carbon fiber composite material to a metal, characterized in that: The steps include: (1) processing 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: impregnating a thermoplastic resin into the carbon fiber structure until a part of the carbon fiber structure is exposed to form a connecting part connected to the hole, wherein the connecting part includes an inserting part and a hooking part, inserting the inserting part into the hole, and connecting the hooking part to the hook part; (3) Welding the connecting parts to the metal parts; (4) Welding the connecting parts to the carbon fiber composite material.

2. The method for welding carbon fiber composite material and 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 and 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, 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, and the power of the two processes is between 10-100W.

4. The method for welding carbon fiber composite material and metal according to claim 1, characterized in that: In the step (3), the connecting piece and the metal piece 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.

5. The method for welding carbon fiber composite material and 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 500-1200r / min, welding speed 10-40mm / min, and downward pressure 0.1-0.3mm.

6. The method for welding carbon fiber composite material and metal according to claim 1, characterized in that: In the 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 wetted into the carbon fiber structure by melt impregnation to obtain a connector, and the process parameters of the melt impregnation are: traction 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 and 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.

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