Connecting method of metal and thermoplastic fiber reinforced composite material

Abstract

The invention belongs to the technical field of dissimilar material connection, and particularly relates to a method for connecting metal and a thermoplastic fiber reinforced composite material. Processing a to-be-connected area of the metal substrate to form a microstructure with a mechanical interlocking effect; the microstructure is subjected to laser remelting treatment, so that a remelting layer with refined grains is formed on the surface; and after the microstructure and the to-be-connected area of the thermoplastic fiber reinforced composite material are attached, a to-be-connected joint structure is formed, the thermoplastic fiber reinforced composite material in the to-be-connected area is melted and filled into the microstructure in a hot-pressing connection mode, cooling and curing are conducted, and the thermoplastic fiber reinforced composite material is obtained. And a composite interface with a mortise and tenon interlocking structure and a grain refining layer is formed on the interface of the metal and the composite material. The method solves the problems of insufficient interface bonding strength, easy corrosion and high failure risk in the existing connection of the metal and the thermoplastic composite material, is suitable for the connection of various metals and the thermoplastic composite material, and has the advantages of high structural strength, strong environmental adaptability and process universality.

Description

Technical Field

[0001] This invention belongs to the field of dissimilar material joining technology, specifically relating to a method for joining metal and thermoplastic fiber-reinforced composite materials. Background Technology

[0002] Dissimilar joining of metals and thermoplastic composites has wide applications in aerospace, rail transportation, and other fields. Thermal joining has become the mainstream method due to its high efficiency and strong structural continuity. However, existing joining structures generally suffer from two core problems: insufficient interfacial bonding strength and high risk of corrosion failure, which severely limit their reliability and durability in complex service environments.

[0003] The insufficient connection strength mainly stems from the lack of an effective interlocking structure at the interface. Due to the surface structure and microstructure of the metal, the molten resin cannot fully fill or lock the metal surface. The connection interface is mainly based on van der Waals forces or limited physical adsorption, which easily leads to delamination and peeling under load, resulting in low mechanical strength of the connection interface. In addition, most existing metal surface treatments are limited to roughening or enhancing wettability, making it difficult to achieve a true "mechanical interlocking" structure and lacking long-term connection stability. The large metal grains and poor surface activity, coupled with insufficient interfacial bonding, easily lead to corrosion failure, providing a channel for the penetration and accumulation of corrosive media such as water vapor and salt spray. Under the action of corrosive media, electrochemical corrosion with the metal as the anode is very likely to occur, further accelerating joint degradation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for joining metals and thermoplastic fiber-reinforced composite materials, addressing the problems of insufficient interfacial bonding strength, susceptibility to corrosion, and high failure risk in the joining of metals and thermoplastic composite materials. Based on the principle of laser surface modification, a remelted layer is formed by constructing a microstructure on the metal surface and performing laser remelting treatment. This achieves synergistic control of interface morphology enhancement and grain refinement. The remelted layer, through grain refinement, increases surface reactivity, promotes the rapid formation of a passivation film, and forms an interfacial structure with mechanical interlocking and corrosion resistance, thereby significantly enhancing the bonding strength and corrosion resistance of the joining interface. This method is characterized by non-contact operation, high precision, and adjustable parameters, and is suitable for high-reliability joining of various easily corroded metals and thermoplastic composite materials.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0006] The purpose of this invention is to provide a method for joining metal and thermoplastic fiber-reinforced composite materials, comprising the following steps: S1. The areas to be joined on the metal substrate are processed to form microstructures with mechanical interlocking effects.

[0007] S2. Laser remelting is performed on the microstructure to form a remelted layer with refined grains on the surface.

[0008] S3. After bonding the microstructure and the thermoplastic fiber-reinforced composite material to be connected, a joint structure is formed. The thermoplastic fiber-reinforced composite material to be connected is melted and filled into the microstructure by hot pressing. After cooling and solidification, a composite interface with a "mortise and tenon" interlocking structure and a grain refinement layer is formed at the interface between the metal and the composite material.

[0009] Furthermore, during laser remelting, the pulse width is 100ns continuous, the wavelength is 1064nm~10.6μm, the power is 50W~1KW, ​​the repetition frequency is 1Hz~100KHz, and the scanning speed is 50mm / s~1000mm / s.

[0010] Furthermore, the thickness of the remelted layer is 5% to 50% of the microstructure depth.

[0011] Furthermore, the thickness of the microstructure is 5% to 70% of the substrate thickness.

[0012] Furthermore, laser remelting reduces the average size of the microstructure surface grains by at least 50% compared to the original grains.

[0013] Furthermore, the microstructures are pits, grooves, grids, or serrated.

[0014] Furthermore, the depth of the microstructure is 2μm to 100μm, the spacing is 10μm to 1000μm, and the width or diameter is 10μm to 1000μm.

[0015] Furthermore, a laser processing method is used to process and form microstructures in the area to be joined on the metal substrate. The laser width is 10fs to 100ns, the wavelength is 243nm to 10.6μm, the power is 1W to 1KW, the repetition frequency is 1Hz to 10MHz, and the scanning speed is 1000mm / s to 10000mm / s.

[0016] Furthermore, the metal is an aluminum alloy or a magnesium alloy; the thermoplastic fiber reinforced composite material is CF / PEEK, GF / PA, or AF / PA.

[0017] Furthermore, during the hot-press connection process, the temperature is 300℃~450℃, the pressure is 0.5MPa~2.0MPa, and the time is 5min~20min.

[0018] Compared with the prior art, the present invention has the following advantages: The connection method provided by this invention employs laser processing to form a microstructure with a mechanical interlocking effect in the region to be joined on a metal substrate, thereby enhancing the filling and interlocking effect of the molten resin in the composite material. By laser remelting the microstructure, the original coarse grains can be transformed into uniform, fine equiaxed grains, forming a grain refinement layer. This improves the density of the metal surface structure, reduces porosity and defects, and inhibits the formation of corrosion-sensitive galvanic regions at the joint. It also promotes the more uniform and stable formation of a passivation film on the fine-grained surface, achieving synergistic regulation of interface morphology enhancement and grain refinement. The remelted layer, through grain refinement, enhances the reactivity and passivation capability of the metal surface, promoting rapid passivation film formation and thus enhancing the corrosion resistance of the heterogeneous connection region of the metal composite. Subsequently, the composite and the treated metal are pre-assembled, and a hot-pressing process is used to fill the microstructure with molten resin and then cool and solidify, forming a robust interlocking interface structure. This method significantly improves the mechanical strength and corrosion resistance of the joint, and is suitable for high-performance connection scenarios of easily corroded metals such as aluminum alloys and magnesium alloys and various thermoplastic composite materials. It has the advantages of strong process versatility, precise interface design and excellent service stability. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the joining method of metal and thermoplastic fiber reinforced composite material in Embodiment 1 of the present invention.

[0020] Figure 2 This is a cross-sectional schematic diagram of the sawtooth-shaped microstructure in Embodiment 1 of the present invention.

[0021] Figure 3 This is a microstructure diagram of the microstructure before and after laser remelting in Example 1 of the present invention.

[0022] Figure 4 This is a comparison diagram of the electrochemical corrosion of the metal-composite material joints in Example 1 and Comparative Example 1 of the present invention.

[0023] Figure 5 This is a comparison diagram of the strength of metal-composite material joints in Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0026] In traditional joining methods, the metal surface structure and microstructure are unfavorable for the penetration and bonding of molten resin, resulting in low mechanical strength and poor durability of the joining interface. Simultaneously, the large metal grains and poor surface activity make it difficult to quickly form a passivation film, leading to easy corrosion failure. Therefore, there is an urgent need for a novel joining method that simultaneously enhances interface bonding and provides surface corrosion resistance to address the problems of insufficient interfacial bonding strength and high risk of corrosion and failure in metal-composite thermal bonding.

[0027] Based on this, the present invention provides a method for joining metal and thermoplastic fiber reinforced composite materials, comprising the following steps: S1. The areas to be joined on the metal substrate are processed to form microstructures with mechanical interlocking effects.

[0028] In this invention, laser processing is used to form microstructures with a mechanical interlocking effect in the areas to be joined on the metal substrate, thereby enhancing the filling and interlocking effect of the molten resin in the composite material. The microstructures are pits, grooves, grids, or serrated, with a depth of 2μm to 100μm, a spacing of 10μm to 1000μm, and a width or diameter of 10μm to 1000μm. It should be noted that, to ensure the tensile strength of the original metal substrate, the thickness of the microstructure should be between 5% and 70% of the substrate thickness.

[0029] In this invention, the metal includes metals such as aluminum alloys or magnesium alloys that are easily corroded by corrosive media such as water vapor and salt spray; the composite material includes composite materials with thermoplastic resin matrix reinforcement fibers such as CF / PEEK, GF / PA, or AF / PA. It should be noted that the thickness of the metal and thermoplastic fiber reinforced composite materials is not specifically limited, as long as the depth of the processed microstructure is between 5% and 70% of the substrate thickness.

[0030] S2. Laser remelting is performed on the microstructure to form a remelted layer with refined grains on the surface.

[0031] In this invention, laser remelting of the microstructure transforms the original coarse grains into uniform, fine equiaxed grains, forming a grain refinement layer. This improves the density of the metal surface, reduces porosity and defects, and suppresses the formation of corrosion-sensitive galvanic regions at the joint. It also promotes the more uniform and stable formation of a passivation film on the fine-grained surface, achieving synergistic regulation of interface morphology enhancement and grain refinement. The remelted layer, through grain refinement, enhances the reactivity and passivation capability of the metal surface, promoting rapid passivation film formation and thus strengthening the corrosion resistance of the heterogeneous connection area of ​​the metal composite. During laser remelting, the pulse width is 100 ns continuous, the wavelength is 1064 nm to 10.6 μm, the power is 50 W to 1 KW, the repetition frequency is 1 Hz to 100 KHz, and the scanning speed is 50 mm / s to 1000 mm / s. The thickness of the remelted layer is 5% to 50% of the microstructure depth.

[0032] In this invention, a remelted layer is obtained through laser remelting, and the thickness of the remelted layer is 5% to 50% of the microstructure depth. This ensures that the remelted layer can play a role in corrosion resistance while maintaining the integrity of the microstructure. Because of the laser thermal effect during the remelting process, if the remelted layer is too thick, it will cause the microstructure to deform or even completely melt and disappear.

[0033] S3. After bonding the microstructure and the thermoplastic fiber-reinforced composite material to be connected, a joint structure is formed. The thermoplastic fiber-reinforced composite material to be connected is melted and filled into the microstructure by hot pressing. After cooling and solidification, a composite interface with a "mortise and tenon" interlocking structure and a grain refinement layer is formed at the interface between the metal and the composite material.

[0034] In this invention, a conventional hot-pressing connection method is adopted. The joint structure to be connected is hot-pressed, so that the thermoplastic fiber-reinforced composite material is melted and filled into the microstructure. The hot-pressing temperature is 300℃~450℃, the pressure is 0.5MPa~2.0MPa, and the time is 5min~20min. After cooling, an interface structure with mechanical interlocking and corrosion resistance is formed, which significantly improves the mechanical strength and corrosion resistance of the joint. It is used for high-performance connection scenarios of easily corroded metals such as aluminum alloys and magnesium alloys with various thermoplastic composite materials. It has the advantages of strong process versatility, precise interface design, and excellent service stability.

[0035] The following specific examples will provide further explanation.

[0036] Example 1 A method for joining a metal and a thermoplastic fiber-reinforced composite material, wherein the metal is a 7075-T6 aluminum alloy with a thickness of 2 mm, and the thermoplastic fiber-reinforced composite material is carbon fiber reinforced polyetheretherketone (CF / PEEK) with a thickness of 2 mm, as shown below. Figure 1 As shown, it includes the following steps: S1. A laser processing method is adopted, using a pulsed fiber laser with a wavelength of 1064nm and a pulse width of 50ns, a laser power of 100W, a scanning speed of 4000mm / s, and a repetition frequency of 50kHz to scan and process a sawtooth microstructure on the surface of an aluminum alloy plate. The sawtooth microstructure has a depth of about 200μm, a spacing of 400μm, and a width of about 200μm.

[0037] S2. A continuous fiber laser is used to remelt the microstructure region. During laser remelting, the pulse width is 100 ns continuous, the wavelength is 1064 nm, the power is 200 W, the repetition frequency is 200 kHz, and the scanning speed is 150 mm / s. This forms a grain-refined remelted layer with a thickness of approximately 50 μm. The original average grain size was approximately 6.8 μm, which was reduced to 2.9 μm after remelting, achieving a refinement rate exceeding 57%. Figure 2 As shown, a serrated microstructure 22 is formed on the surface of the metal substrate 23, and a grain-refined remelted layer 21 is formed on the serrated microstructure.

[0038] S3. The serrated microstructures on one end surface of the CF / PEEK composite plate and the aluminum alloy surface are overlapped and assembled with an overlap length of 10mm to form a joint structure to be connected.

[0039] S4. Using a hot-press connection method, the assembly is placed in a hot-press device and pressure-connected for 10 minutes at 390℃ and 1.5MPa. Then it is cooled and shaped to form a composite interface with a "mortise and tenon" interlocking structure and a grain refinement layer at the interface between the metal and the composite material.

[0040] Example 2 A method for joining a metal and a thermoplastic fiber-reinforced composite material, wherein the metal is AZ91 magnesium alloy with a thickness of 5 mm, and the thermoplastic fiber-reinforced composite material is a glass fiber reinforced polyamide (GF / PA) composite plate with a thickness of 1.5 mm, comprising the following steps: S1. A green nanosecond laser with a wavelength of 532nm and a pulse width of 30ns is used for laser processing. The laser power is 20W, the scanning speed is 6000mm / s, and the repetition frequency is 100KHz. A pit array microstructure is formed on the surface of AZ91 magnesium alloy. The depth of the pit array microstructure is about 150μm, the spacing is 200μm, and the diameter is about 150μm.

[0041] S2. A CO2 laser with a wavelength of 10.6 μm is used to remelt the microstructure region. During the laser remelting process, the power is 100W, the repetition frequency is 100Hz, and the scanning speed is 100mm / s to form a grain-refining remelted layer. The thickness of the remelted layer is about 8 μm, and the original average grain size is about 9.5 μm, which is reduced to 4.2 μm after remelting, with a refinement rate of more than 55%.

[0042] S3. The pit array microstructure on one end surface of the GF / PA composite plate and the surface of the AZ91 magnesium alloy are overlapped and assembled with an overlap length of 8mm to form a joint structure to be connected.

[0043] S4. Using a hot-press connection method, the assembly is placed in a hot-press platform and pressure-connected for 8 minutes at 310℃ and 1.0MPa. Then it is cooled and shaped to form a composite interface with a "mortise and tenon" interlocking structure and a grain refinement layer at the interface between the metal and the composite material.

[0044] Comparative Example 1 A method for joining a metal and a thermoplastic fiber-reinforced composite material, wherein the metal is a 7075-T6 aluminum alloy with a thickness of 2 mm, and the thermoplastic fiber-reinforced composite material is carbon fiber reinforced polyetheretherketone (CF / PEEK) with a thickness of 2 mm, as shown below. Figure 1 As shown, it includes the following steps: S1. A laser processing method is adopted, using a pulsed fiber laser with a wavelength of 1064nm and a pulse width of 50ns, a laser power of 100W, a scanning speed of 4000mm / s, and a repetition frequency of 50kHz to scan and process a sawtooth microstructure on the surface of an aluminum alloy plate. The sawtooth microstructure has a depth of about 200μm, a spacing of 400μm, and a width of about 200μm.

[0045] S2. The serrated microstructures on one end surface of the CF / PEEK composite plate and the aluminum alloy surface are overlapped and assembled with an overlap length of 10mm to form a joint structure to be connected.

[0046] S3. Using a hot-press connection method, the assembly is placed in a hot-press device and pressure-connected for 10 minutes at 390℃ and 1.5MPa. Then it is cooled and shaped to form an interface with a "mortise and tenon" interlocking structure at the interface between the metal and the composite material.

[0047] Figure 3 The diagram shows the microstructure of the microstructure before and after laser remelting in Example 1 of this invention. Figure 3 In the diagram, 31 represents the remelted layer grains, and 32 represents the metal matrix grains. For example... Figure 3 As shown, the grain size before remelting is about 20μm to 30μm, and the grain size is refined to about 1μm to 3μm after laser remelting.

[0048] Figure 4 This is a comparison diagram of the electrochemical corrosion of the metal-composite material joints in Example 1 and Comparative Example 1 of the present invention. Figure 4 As shown, the self-corrosion potential E on the material surface after laser remelting corr A positive shift indicates a decrease in its thermodynamic corrosion tendency and an increase in its corrosion resistance.

[0049] Figure 5 This is a comparison diagram of the strength of the metal-composite material joints in Embodiment 1 and Comparative Example 1 of the present invention. Figure 5 As shown, the joint of the metal-composite material in Comparative Example 1 broke when the tensile force reached about 5000N, while the joint of the metal-composite material in Example 1 of this application only broke when the tensile force reached 6500N, indicating that the joint strength was greatly increased, by more than 30%.

[0050] In summary, this technical solution discloses a method for joining easily corroded metals with thermoplastic fiber-reinforced composite materials. By laser-constructing microstructures on the metal surface and performing grain refinement and remelting, the resin-filling capacity and surface reactivity of the interface morphology are improved. Subsequently, the composite material and the treated metal are pre-assembled, and a hot-pressing process is used to fill the microstructure with molten resin, followed by cooling and solidification to form a robust interlocking interface structure. This method significantly improves the mechanical strength and corrosion resistance of the joint, and is suitable for high-performance joining scenarios involving easily corroded metals such as aluminum alloys and magnesium alloys with various thermoplastic composite materials. It possesses advantages such as strong process versatility, precise interface design, and excellent service stability.

[0051] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0052] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for joining a metal and a thermoplastic fiber-reinforced composite material, characterized in that, Includes the following steps: The areas to be joined on the metal substrate are processed to form microstructures with mechanical interlocking effects; Laser remelting is performed on the microstructure to form a remelted layer with refined grains on the surface; After bonding the microstructure and the thermoplastic fiber-reinforced composite material to be connected, a joint structure is formed. The thermoplastic fiber-reinforced composite material to be connected is melted and filled into the microstructure by hot pressing. After cooling and solidification, a composite interface with a "mortise and tenon" interlocking structure and a grain refinement layer is formed at the interface between the metal and the composite material.

2. The method for joining metal and thermoplastic fiber reinforced composite materials according to claim 1, characterized in that, During laser remelting, the pulse width is 100ns continuous, the wavelength is 1064nm~10.6μm, the power is 50W~1KW, ​​the repetition frequency is 1Hz~100KHz, and the scanning speed is 50mm / s~1000mm / s.

3. The method for joining metal and thermoplastic fiber reinforced composite materials according to claim 1, characterized in that, The thickness of the remelted layer is 5% to 50% of the microstructure depth.

4. The method for joining metal and thermoplastic fiber reinforced composite materials according to claim 1, characterized in that, The thickness of the microstructure is 5% to 70% of the substrate thickness.

5. The method for joining metal and thermoplastic fiber reinforced composite materials according to claim 1, characterized in that, Laser remelting reduces the average size of microstructure surface grains by at least 50% compared to the original grains.

6. The method for joining metal and thermoplastic fiber reinforced composite materials according to claim 1, characterized in that, The microstructures are pits, grooves, grids, or serrated.

7. The method for joining metal and thermoplastic fiber reinforced composite materials according to claim 6, characterized in that, The depth of the microstructure is 2μm to 100μm, the spacing is 10μm to 1000μm, and the width or diameter is 10μm to 1000μm.

8. The method for joining metal and thermoplastic fiber-reinforced composite materials according to claim 1, characterized in that, Microstructures are formed in the areas to be joined on a metal substrate using laser processing. The laser has a width of 10 fs to 100 ns, a wavelength of 243 nm to 10.6 μm, a power of 1 W to 1 KW, a repetition frequency of 1 Hz to 10 MHz, and a scanning speed of 1000 mm / s to 10000 mm / s.

9. The method for joining metal and thermoplastic fiber-reinforced composite materials according to claim 1, characterized in that, The metal is an aluminum alloy or magnesium alloy; the thermoplastic fiber reinforced composite material is CF / PEEK, GF / PA or AF / PA.

10. The method for joining metal and thermoplastic fiber reinforced composite materials according to claim 1, characterized in that, During the hot-press connection process, the temperature is 300℃~450℃, the pressure is 0.5MPa~2.0MPa, and the time is 5min~20min.

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