Heterogeneous connection method for titanium alloy and carbon fiber reinforced resin matrix composite

Abstract

The invention provides a titanium alloy and carbon fiber reinforced resin matrix composite heterogeneous connection method which comprises the following steps: cleaning a titanium alloy sample to remove surface oil stain, distributing graphene on the surface of titanium alloy ball powder, and carrying out selective laser melting treatment to obtain a GNPs-TiC-titanium alloy connection mode and the titanium alloy; hydroxylating the surface of the titanium alloy sample; coating the hydroxylated surface with a silane coupling agent hydrolysis solution, and drying; and the titanium alloy and a carbon fiber reinforced resin matrix composite material are subjected to vacuum bag pressing and integrated curing forming, and the titanium alloy / CFRP heterogeneous connection material is obtained. According to the preparation method, a micron-sized porous structure is constructed on the surface of the titanium alloy through a selective laser melting method, a silane coupling agent hydrolysis solution is coated, and vacuum bag pressing integrated forming and vacuumizing are combined, so that resin can better permeate into the porous structure on the surface of the titanium alloy, better compatibility of the titanium alloy and a resin matrix is promoted, and the titanium alloy surface is more uniform. Therefore, the interface bonding strength between the titanium alloy and the carbon fiber reinforced resin-based composite material is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material connection, in particular to a high-strength heterogeneous connection method of titanium alloy material and carbon fiber reinforced resin matrix composite (CFRP), and particularly to a method of surface modification and integrated co-solidification forming by using selective laser melting (SLM) technology. BACKGROUND

[0002] Titanium alloy and carbon fiber reinforced resin matrix composite (CFRP) are widely used in aerospace, new energy vehicles and other fields due to their excellent performance (toughness, electrical conductivity of titanium alloy, and high specific strength, specific modulus of CFRP). Realizing reliable and efficient connection between the two is a key technical difficulty for structural lightweight.

[0003] The main connection methods at present include mechanical connection and adhesive bonding. Mechanical connection needs to punch holes, which can easily cause stress concentration, damage the continuity of fibers, and increase the weight of the structure. Adhesive bonding relies on adhesives, and the interfacial bonding strength is often insufficient, and the adhesive layer is prone to aging and has poor durability. In the prior art, in order to improve the interfacial bonding strength of titanium alloy and CFRP, the surface of titanium alloy is often pretreated, such as anodic oxidation, laser etching, laser texturing, etc., to increase the surface roughness and mechanical interlocking effect. However, these methods can only construct microscale structures, and may introduce pollution or cause substrate damage during the processing, and the improvement of chemical compatibility with resin is limited, and the interfacial strength still needs to be improved.

[0004] Therefore, it is of great significance to develop a heterogeneous connection method that can simultaneously realize strong mechanical interlocking and excellent chemical bonding, and can be efficiently integrated with the CFRP forming process. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a heterogeneous connection method based on graphene modified titanium alloy and carbon fiber reinforced resin matrix composite. The method realizes high-strength and high-durability connection between titanium alloy and CFRP by in-situ constructing micro-nano porous structure and graphene modification layer on the surface of titanium alloy, combining with silane coupling agent bridging technology, and through vacuum bag pressing integrated curing process.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] A heterogeneous connection method based on graphene modified titanium alloy and carbon fiber reinforced resin matrix composite, comprising the following steps:

[0008] Step S1: Clean the titanium alloy sample to completely remove surface oil stains and impurities.

[0009] Step S2: distribute graphene on the surface of titanium alloy spherical powder, prepare a mixed powder, process the titanium alloy surface by selective laser melting (SLM), control the laser process parameters to obtain a titanium alloy surface containing porous structures, and graphene and titanium alloy partially react to obtain a titanium alloy surface connected by GNPs-TiC-titanium alloy.

[0010] Step S3: hydroxylate the titanium alloy sample after SLM processing to make the surface rich in hydroxyl (-OH) functional groups.

[0011] Step S4: prepare a silane coupling agent into a hydrolysis solution, then coat it on the hydroxylated titanium alloy surface, and then perform drying treatment to make the silane coupling agent form a chemically bonded bridging layer on the titanium alloy surface.

[0012] Step S5: place the processed titanium alloy sample and unsolidified carbon fiber reinforced resin prepreg according to the design layer, and use vacuum bag pressing process for integrated solidification molding. Under vacuum and heating conditions, the resin matrix melts and fully penetrates into the porous structure on the surface of the titanium alloy under external pressure, and chemically reacts with the silane coupling agent layer, finally forming a titanium alloy / CFRP heterogeneous connection material, and obtaining a carbon fiber-resin-graphene-TiC-titanium alloy "flexible riveting" interface strengthening mode.

[0013] In the present application, the micro-nano porous structure and graphene modification layer are constructed on the titanium alloy surface in situ by selective laser melting method, and combined with the silane coupling agent bridging technology, the resin can better penetrate into the porous structure on the surface of the titanium alloy under the co-solidification process. The graphene and silane coupling agent on the surface can promote the better compatibility of the titanium alloy and the carbon fiber composite material of the resin matrix, and the bonding force is stronger, so as to prepare a hybrid part of titanium alloy and carbon fiber reinforced resin matrix composite material.

[0014] Preferably, in step 1, the method for removing surface dirt includes any one or a combination of inorganic alkali washing, organic solvent washing, water-based cleaner cleaning, and water vapor cleaning.

[0015] Preferably, in step 2, the laser process parameters range from 40-100W of laser power, 200-1000mm / s of scanning speed, and 0.05-0.2mm of scanning interval.

[0016] Preferably, in step 3, the hydroxylization treatment uses one of oxygen plasma treatment, ultraviolet ozone treatment, or strong oxidizing acid solution (such as concentrated sulfuric acid / hydrogen peroxide mixed solution) treatment.

[0017] Preferably, in step 4, the silane coupling agent is one of amino silane, epoxy silane, or vinyl silane, and the hydrolysis solution concentration is 0.5%-5%.

[0018] Preferably, in step 5, the vacuum degree of the vacuum bag molding process is not less than-0.095 MPa.

[0019] The technical details not described in detail in the scheme can be implemented according to the conventional understanding and operation of those skilled in the art, and the embodiments are not described in detail here.

[0020] Compared with the prior art, the present application has the following remarkable advantages:

[0021] (1) Synergistic reinforcement mechanism: The present application innovatively applies SLM technology to surface modification, and simultaneously realizes the three interface reinforcement mechanisms of "physical anchoring" (microporous structure), "chemical bonding" (silane coupling agent bridging), and "nano-enhancement" (surface graphene modification) at one time, greatly improving the interface bonding strength.

[0022] (2) Strong mechanical interlocking: The three-dimensional interconnected porous structure created by SLM technology provides a large anchoring space for the resin, and the resin can deeply penetrate into the pores under the action of vacuum and external pressure during co-curing, forming a strong mechanical interlocking effect after solidification.

[0023] (3) Excellent interface compatibility and chemical bonding: Hydroxylation treatment and silane coupling agent coating, on the one hand, form a firm bond with the hydroxyl groups on the titanium alloy surface, and on the other hand, the organic functional groups (such as amino, epoxy) react with the resin matrix to form a strong covalent bond bridge, effectively relieving interface stress and improving durability.

[0024] (4) Reinforcement effect of graphene: The in-situ generated graphene layer can effectively improve the hardness, wear resistance and chemical stability of the titanium alloy surface, and the ultra-high specific surface area and excellent performance of graphene can further strengthen the interface, possibly inducing the resin to produce more ordered interface structure, thereby improving the mechanical properties and fatigue resistance of the interface.

[0025] (5) High process integration: The method is perfectly compatible with the vacuum bag molding process of CFRP, realizing the integrated forming of heterogeneous structures, reducing assembly steps, improving production efficiency, and avoiding the additional weight and aging problems caused by gluing. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a process flow diagram of the heterogeneous connection method in the present application.

[0027] Figure 2 is a schematic diagram of the microstructure of the titanium alloy surface after SLM treatment in the present application.

[0028] Figure 3 is a SEM image of the interface bonding between titanium alloy and CFRP in the present application.

[0029] Figure 4 Titanium alloy and CFRP lap joint sample schematic diagram in the application.

[0030] Wherein, the reference signs are: 1, titanium alloy plate; 2, cleaning agent; 3, titanium alloy and graphene mixed powder; 4, laser beam; 5, printed titanium alloy plate; 6, hydroxyl solution; 7, coupling agent solution; 8, CFRP prepreg lay-up before curing; 9, vacuum bag compression molding co-curing; 10, graphene existing on the printed surface; 11, resin in the pores; 12, graphene pinned in the resin; 13, cured CFRP. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application. Those skilled in the art can modify or replace equivalently without departing from the spirit and scope of the present application, which should be covered within the protection scope of the present application.

[0032] The raw materials used in the following specific embodiments are all purchased from the market. The titanium alloy plate used in the examples and comparative examples of the present application is TA15 type titanium alloy, and the CFRP used is carbon fiber reinforced epoxy resin matrix composite, with the trade name 2103. The curing process of the epoxy resin resin is room temperature→85℃, 85℃ for 30min, followed by 85℃→100℃, 100℃ for 90min, with a heating rate of 1℃ / min;

[0033] Titanium alloy and resin or composite material interface bonding strength test method (non-standard test method): on the universal testing machine, the tensile speed is 1.5mm / min, the test temperature is room temperature 25℃±0.5℃, the load F (N) measured at the time of tensile fracture, the area of the composite material wrapped around the titanium alloy is S (mm 2 ), and the interface bonding strength (τ, MPa) of the titanium alloy and the composite material is calculated by the formula τ=F / S.

[0034] Referring to Figures 1-4 A method for hetero-joining titanium alloy and carbon fiber reinforced resin matrix composite, specifically comprising the following steps:

[0035] Step S1: Place the titanium alloy plate 1 in the cleaning agent 2 for cleaning, thoroughly remove the surface oil and impurities.

[0036] Step S2: Distribute graphene on the surface of titanium alloy spherical powder to prepare titanium alloy and graphene mixed powder 3, use a selective laser printer 4 to process the surface of titanium alloy by selective laser melting (SLM), and obtain printed titanium alloy plate 5, as shown in Figure 1 By controlling the laser process parameters, a titanium alloy with a porous structure on the surface is obtained, and graphene and titanium alloy undergo partial chemical reaction to obtain a titanium alloy surface with a GNP-TiC-titanium alloy connection mode.

[0037] Step S3: Place the titanium alloy sample after SLM treatment in a hydroxylation solution 6 for hydroxylation treatment to make the surface rich in hydroxyl (-OH) functional groups.

[0038] Step S4: Prepare a silane coupling agent into a hydrolysis solution to form a coupling agent solution 7, then coat it on the hydroxylated titanium alloy surface, and then perform drying treatment to make the silane coupling agent form a chemically bonded bridge layer on the titanium alloy surface.

[0039] Step S5: Place the treated titanium alloy sample and the unsolidified carbon fiber reinforced resin prepreg according to the design to obtain the CFRP prepreg layer 8 before curing, and use the vacuum bag molding co-curing 9 process for integrated curing molding. Under vacuum and heating conditions, the resin matrix melts and fully penetrates into the porous structure on the surface of the titanium alloy under external pressure, and at the same time, chemically reacts with the silane coupling agent layer, and finally forms a titanium alloy / CFRP heterogeneous connection material, obtaining a carbon fiber-resin-graphene-TiC-titanium alloy "flexible riveting" interface strengthening mode. That is, it includes titanium alloy plate 1, graphene 10 existing on the printed surface, resin 11 infiltrated into the graphene and titanium alloy spherical powder pores, graphene 12 pinned in the resin, and the outermost is the cured CFRP 13.

[0040] Referring to Figure 3 This figure shows the microstructure of titanium alloy and CFRP. In the figure, 1 is the titanium alloy plate as the substrate; 5 is the printed titanium alloy plate, which presents a three-dimensional porous structure. In the pores of the titanium alloy structure, there is resin 11, and 12 is graphene pinned in the resin, which plays a role in reinforcement, etc. The uppermost 13 is the cured carbon fiber, and the overall structure shows the combination and distribution of resin-graphene-titanium alloy. From the interface connection, it can be seen that between the titanium alloy plate and the cured CFRP, the resin 11 in the pores and the graphene 12 pinned in the resin 11 are fully infiltrated, so that the resin 11 produces a more ordered interface structure, thereby improving the mechanical properties and fatigue resistance of the interface.

[0041] In step S1, the titanium alloy plate 1 is immersed in anhydrous ethanol solution (cleaning agent 2) for 5 min to remove surface oil stains, then washed with deionized water to neutral, and dried for standby.

[0042] In step S2, graphene and titanium alloy spherical powder are mixed by stirring, filtration and drying process to prepare a mixed powder, and the titanium alloy surface is treated by selective laser melting (SLM), as shown in the schematic Figure 1 structure. By controlling the laser process parameters, a titanium alloy surface with a porous structure is obtained, and graphene and titanium alloy partially react to obtain a titanium alloy surface with a GNPs-TiC-titanium alloy connection mode.

[0043] In step S3, the titanium alloy insert obtained in S2 is immersed in a concentrated sulfuric acid / hydrogen peroxide mixed solution for 30 min to perform hydroxylation treatment on the titanium alloy surface.

[0044] In step S4, a 1wt% KH-550 (aminosilane) aqueous solution is prepared, and after hydrolysis for 30 min, the hydrolysis solution is dropped on the hydroxylated titanium alloy surface, and after standing for 10 min, it is dried, then dried in an 80℃ oven for 1 hour.

[0045] In step S5, the epoxy carbon fiber prepreg (T700 / EP) is sequentially laid on the treated titanium alloy plate surface and placed in a mold, and a vacuum bag is sealed. Vacuum to-0.098MPa, then according to the curing process of epoxy resin, heat and pressure curing.

[0046] In step S3, the concentration of the concentrated sulfuric acid / hydrogen peroxide mixed solution is not limited, and the commonly used concentration value in the laboratory can be used. The concentration value will affect the processing speed, but has little effect on the final result. The same applies to the following comparative examples.

[0047] After curing, the sample is taken out to obtain a standard shear test sample, as shown in Figure 4 The interface shear strength reaches more than 20MPa through tensile shear test, which is much higher than the strength of traditional sand blasting treatment (usually <20MPa), and the failure mode is mostly composite material cohesion failure, indicating that the interface bonding strength is higher than part of the strength of the composite material itself.

[0048] In order to more clearly illustrate the beneficial effects of the present application, the present application examples and several typical processing methods representing the prior art are compared. All comparative examples use the same TA15 titanium alloy plate and T700 / EP epoxy carbon fiber prepreg as the application examples (see above), and the interface bonding strength is measured according to the same non-standard test method.

[0049] Comparative Example 1

[0050] Step 1: Similar to S1 of the present application, the TA15 titanium alloy plate was ultrasonically cleaned in anhydrous ethanol for 10 minutes to remove surface oil, then rinsed with deionized water and dried.

[0051] Step 2: The titanium alloy surface was sandblasted using white corundum (alumina) abrasive (particle size 80 mesh) at a compressed air pressure of 0.5 MPa, about 150 mm away from the workpiece, until the surface appeared uniformly matte gray.

[0052] Step 3: After sandblasting, the surface was blown off with compressed air and ultrasonically cleaned in anhydrous ethanol for 5 minutes to remove residual abrasive dust, then dried.

[0053] Step 4: A layer of epoxy structural adhesive film identical to the resin system of the present application was applied to the treated titanium alloy surface. Then, according to the same lay-up method and vacuum bag pressing process (vacuum degree -0.098 MPa) and curing curve as S5 of the present application, it was co-cured and connected with the CFRP prepreg.

[0054] According to the metal and composite interfacial bonding strength test method, it was tested for interfacial bonding strength, and the test showed that the average interfacial shear strength of the sample prepared in this comparative example was 15.2 MPa. The failure mode was mainly interfacial adhesion failure, indicating that the bonding strength was limited and the interface was the weak link. Sandblasting mainly provides mechanical anchoring at the microscale. Its rough structure is irregular, and lacks the ability to chemically bond with the resin, so the interfacial bonding strength is limited and is prone to failure at the interface.

[0055] Comparative Example 2

[0056] Step 1: Similar to S1 of the present application, the TA15 titanium alloy plate was ultrasonically cleaned in anhydrous ethanol for 10 minutes to remove surface oil, then rinsed with deionized water and dried.

[0057] Step 2: The treated titanium alloy plate was used as the anode and platinum sheet as the cathode, and was placed in a 0.3 mol / L phosphoric acid solution for anodic oxidation. A direct current voltage of 20 V was applied for 20 minutes.

[0058] Step 3: After oxidation, the titanium alloy plate was removed, rinsed with a large amount of deionized water, and dried at low temperature. Similar to Comparative Example 1, an epoxy adhesive film was applied and co-cured with CFRP.

[0059] The average interface shear strength of the sample prepared in the comparative example was 17.8 MPa. The failure mode was still mainly interfacial adhesive failure, indicating that the porous oxide layer formed by anodization improved the mechanical interlocking, but the chemical bonding ability of the porous oxide layer with the resin was still insufficient, and the interface strength was limitedly improved.

[0060] Comparative Example 3

[0061] Step 1: Similar to S1 of the present application, the TA15 titanium alloy plate was ultrasonically cleaned in anhydrous ethanol for 10 minutes to remove surface oil stains, then rinsed with deionized water and dried.

[0062] Step 2: A pulsed fiber laser was used to etch a grid pattern on the surface of the titanium alloy. The laser process parameters were: power 30 W, scanning speed 800 mm / s, pulse frequency 50 kHz, scanning pitch 0.07 mm, and engraving 2 times.

[0063] Step 3: After laser etching, the sample was ultrasonically cleaned in anhydrous ethanol for 5 minutes to remove the surface of the molten residue, and then dried. Similar to Comparative Example 1, the epoxy film was coated and co-cured with the CFRP.

[0064] The average interface shear strength of the sample prepared in the comparative example was 17.8 MPa. The failure mode was still mainly interfacial adhesive failure, indicating that the porous oxide layer formed by anodization improved the mechanical interlocking, but the chemical bonding ability of the porous oxide layer with the resin was still insufficient, and the interface strength was limitedly improved. Laser etching / laser texturing is a method of using a laser beam (such as a pulsed laser) to scan the surface of the titanium alloy, directly manufacturing a designed microgroove, pit or grid pattern through ablation. It has high precision, strong controllability and is clean and pollution-free. It can build an optimized mechanical interlocking structure. However, compared with selective laser melting, laser etching / laser texturing is usually subtractive manufacturing (removing material), and the structure formed is mainly two-dimensional or shallow three-dimensional. The SLM of the present application is additive manufacturing, which can build a three-dimensional interconnected porous structure to provide a more superior “anchoring” space for the resin. Table 1 is a summary table of the test results of the examples of the present application and the three comparative examples.

[0065] Table 1 Summary table of test results of examples of the present application and three comparative examples

[0066] Treatment Interfacial shear strength (MPa) Main failure mode Core reinforcement mechanism Comparative Example 1 : Sandblasting + Gluing 15.2 Interfacial adhesive failure Macroscopic mechanical interlocking Comparative Example 2: Anodization + Gluing 17.8 Interfacial adhesive failure Microporous mechanical interlocking Comparative Example 3: Laser etching + Gluing 16.5 Interfacial adhesive failure Designed mechanical interlocking Embodiment of the invention >20.0 Composite cohesive failure Triple synergistic reinforcement (3D physical anchoring + chemical bonding + nano-reinforcement)

[0067] From the above comparison, it can be clearly seen that the interfacial bonding strength obtained by the method of the present application is significantly higher than that of all the comparative examples representing the prior art. Most importantly, the failure mode of the method of the present application has undergone a fundamental change. The failure of the comparative examples all occurs at the interface between the titanium alloy and the resin, which is the weak point of the connection. While the failure of the embodiments of the present application occurs in the composite material itself, proving that the interfacial bonding strength has exceeded the partial strength of the composite material itself, achieving a truly "strong interface" connection.

[0068] This excellent performance is attributed to the unique triple synergistic reinforcement mechanism of the present application: the porous structure constructed by SLM provides resin infiltration channels, forms physical anchoring, and realizes mechanical interlocking reinforcement. Hydroxylation and silane coupling agent promote chemical bonding between the titanium alloy and the resin, and promote chemical bonding reinforcement. Graphene improves the hardness and wear resistance of the titanium alloy surface, enhances the interfacial compatibility, induces the resin to form a more ordered interface structure, realizes the nano-reinforcement of the interface, and through the synergistic effect of the triple reinforcement mechanism, finally realizes the interfacial reinforcement of the titanium alloy and the composite material.

[0069] It should be noted that the interfacial shear strength data in Table 1 is an average value obtained under the existing technical conditions using conventional technical means, and the specific data is determined according to the corresponding parameter adjustment, so the above data has important reference significance, proving that the technical solution of the present application is superior to the prior art.

[0070] The above is only an embodiment of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the invention or exceed the scope defined by the present claims, which should belong to the protection scope of the present application.

Claims

1. A method of heterogeneously joining a titanium alloy and a carbon fiber reinforced resin matrix composite material, characterized by, The method comprises the following steps: Step S1: cleaning the titanium alloy sample to completely remove surface oil and impurities; Step S2: distributing graphene on the surface of titanium alloy powder to prepare a mixed powder, processing the surface of the titanium alloy by selective laser melting, and controlling laser process parameters to obtain a titanium alloy with a porous structure on the surface; Step S3: hydroxylating the titanium alloy sample after SLM processing to enrich the surface with hydroxyl functional groups; Step S4: preparing a hydrolysis solution of silane coupling agent, coating it on the hydroxylated titanium alloy surface, and then performing drying treatment to form a chemically bonded bridge layer of the silane coupling agent on the titanium alloy surface; Step S5: placing the treated titanium alloy sample and uncured carbon fiber reinforced resin prepreg according to the design layup, and integrally curing and forming by vacuum bag pressing process.

2. The method of claim 1, wherein the titanium alloy and the carbon fiber reinforced resin matrix composite are different materials. In the step S1, the method for removing surface oil includes any one or a combination of multiple of inorganic alkali washing, organic solvent washing, water-based cleaner cleaning, and water vapor cleaning.

3. The method of claim 1, wherein the titanium alloy and the carbon fiber reinforced resin matrix composite are different materials. In the step S2, the graphene and titanium powder are fully mixed by stirring, filtration, and drying processes before the selective laser melting process of the titanium alloy surface.

4. The method of claim 3, wherein the titanium alloy and the carbon fiber reinforced resin matrix composite are different materials. In the step S2, the laser process parameters range from 40-100 W of laser power, 200-1000 mm / s of scanning speed, and 0.05-0.2 mm of scanning pitch.

5. The method of claim 1, wherein the titanium alloy and the carbon fiber reinforced resin matrix composite are different materials. In the step S3, the hydroxylization treatment uses any one of oxygen plasma treatment, ultraviolet ozone treatment, or strong oxidizing acid solution treatment.

6. The method of claim 1, wherein the titanium alloy and carbon fiber reinforced resin matrix composite heterogeneous joining method is characterized by, In the step S4, the silane coupling agent is any one of amino silane, epoxy silane, or vinyl silane, and the concentration of the hydrolysis solution is 0.5%-5%.

7. The method of claim 1, wherein the titanium alloy and the carbon fiber reinforced resin matrix composite are different materials. In the step S5, the vacuum degree of the vacuum bag pressing forming process is not less than -0.095 MPa.

8. The method of claim 1-7, wherein a titanium alloy and carbon fiber reinforced resin-based composite material heterogeneous connection material with strong interfacial bonding strength is prepared.

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