Interface enhancement method for improving electromagnetic shielding effectiveness of titanium alloy-carbon fiber reinforced resin-based laminated structure based on MWCNTs

Abstract

The invention discloses an interface enhancement method for improving the electromagnetic shielding effectiveness of a titanium alloy-carbon fiber reinforced resin-based laminated structure based on MWCNTs, and belongs to the technical field of metal / composite material interface modification and electromagnetic shielding. The problems that an existing titanium alloy-carbon fiber reinforced resin-based laminated structure is weak in interface conductivity, insufficient in electromagnetic wave absorption and low in shielding effectiveness are solved. According to the method, firstly, a rough structure is constructed on the surface of a titanium plate, then, an MWCNTs conductive interface layer is constructed on the surface of the titanium plate through electrophoretic deposition, finally, the modified titanium plate and carbon fiber reinforced resin matrix composite prepreg are alternately stacked, and the laminated plate is prepared through hot press molding. The uniform and continuous MWCNTs three-dimensional conductive network with high adhesive force is formed on the titanium alloy / composite material interface. The network not only can enhance interface mechanical interlocking, but also can provide an efficient interface conductive path, and promotes multiple reflection and absorption loss of electromagnetic waves; and the shielding mechanism is converted into a more excellent reflection-absorption cooperative mode from a reflection dominant mode.

Description

Technical Field

[0001] This invention belongs to the field of metal / composite material interface modification and electromagnetic shielding technology. Specifically, it relates to an interface enhancement method that improves the electromagnetic shielding effectiveness of titanium alloy-carbon fiber reinforced resin matrix structures by constructing a conductive interface layer through electrophoretic deposition of multi-walled carbon nanotubes (MWCNTs). Background Technology

[0002] With the rapid development of electronic and wireless communication technologies, electromagnetic radiation pollution in the environment is becoming increasingly serious, posing a threat to the stability and reliability of precision electronic equipment. Therefore, effective electromagnetic interference shielding materials have become crucial, especially in advanced engineering fields such as aerospace and defense, where there is an urgent need for lightweight structural materials that combine excellent mechanical properties with high electromagnetic shielding efficiency.

[0003] Metallic materials, with their high conductivity and excellent reflection capabilities of incident electromagnetic waves, effectively shield electromagnetic waves, making them the most widely used shielding materials. However, their high density, susceptibility to corrosion, and high cost make it difficult to meet the comprehensive requirements of modern equipment for lightweighting, durability, and structural integration. While fiber-reinforced resin-based materials offer advantages such as lightweight, high specific strength, and fatigue resistance, meeting the requirements for lightweighting and structural strength, their insufficient conductivity and discontinuous conductive mesh limit their electromagnetic shielding effectiveness. To overcome these challenges, fiber-reinforced metal laminates combine the characteristics of traditional metals and fiber-reinforced resin-based composites, exhibiting high specific strength, excellent impact resistance, and fatigue performance, providing a new solution for developing structurally and functionally integrated electromagnetic shielding materials.

[0004] The interface quality between the metal layer and the composite material layer is one of the key factors affecting the electromagnetic shielding effectiveness of fiber-reinforced metal laminates. Laminated structures using titanium alloys as the metal layer exhibit excellent corrosion resistance and mechanical stability; however, the dense oxide film on the titanium surface results in strong chemical inertness, making it difficult to form a strong interfacial bond with the resin matrix. This weak interface not only affects interlayer load transfer and structural integrity but also limits the multiple reflections, scattering, and loss of electromagnetic waves at the interface due to the inability to establish an effective conductive path, leading to poor overall shielding effectiveness. Traditional surface modification methods such as sandblasting and etching mainly improve the mechanical interlocking ability of the interface, but are difficult to construct a continuous conductive network. Therefore, introducing highly conductive nanomaterials to construct functional interface layers has become an effective strategy. MWCNTs conductive nanomaterials, due to their excellent conductivity and high specific surface area, can serve as ideal materials for constructing functional interfaces. Summary of the Invention

[0005] This invention addresses the problems of weak interfacial conductivity, insufficient electromagnetic wave absorption, and low shielding effectiveness in existing titanium alloy-carbon fiber reinforced resin matrix composite structures. It provides an interface enhancement method based on MWCNTs to improve the electromagnetic shielding effectiveness of these structures. This invention constructs a continuous, uniform, and well-adhesive conductive nanonetwork layer by electrophoretically depositing on a roughened titanium alloy surface. This not only improves the interfacial bonding strength between the titanium alloy and the resin but also forms a stable interfacial conductive path, enhancing the multiple reflections, scattering, and absorption losses of electromagnetic waves in the interfacial region, thereby significantly improving the electromagnetic shielding effectiveness of the titanium alloy-carbon fiber reinforced resin matrix composite structure.

[0006] To address the aforementioned technical problems, the present invention adopts the following technical solution: The purpose of this invention is to provide an interface enhancement method based on MWCNTs to improve the electromagnetic shielding effectiveness of titanium alloy-carbon fiber reinforced resin composite structures, characterized by comprising the following steps: Step 1: Remove the oxide layer from the surface of the titanium plate to form a rough structure, then clean with solvent; Step 2: Using the titanium plate treated in Step 1 as the cathode and the conductive material as the anode, place the two electrodes in a MWCNTs suspension and perform electrophoretic deposition under a set voltage to form a MWCNTs conductive network structure layer on the surface of the titanium plate, and then dry it. Step 3: Alternately stack the titanium plate treated in Step 2 and the carbon fiber reinforced resin matrix composite prepreg, and hot press to form the finished product; The MWCNTs suspension is prepared by adding surface-functionalized MWCNTs and a metal salt electrolyte that can provide positive ions to an ethanol-acetone mixed solvent and then dispersing them ultrasonically. Further specifying, in step 1, one or more of the following methods are used to form a rough structure: sandblasting, mechanical polishing, laser texturing, chemical etching, or anodizing.

[0007] Further specifying, the surface-functionalized MWCNTs are carboxylated multi-walled carbon nanotubes.

[0008] Furthermore, the carboxylated multi-walled carbon nanotubes have an inner diameter of 2nm-5nm, an outer diameter of 5nm-15nm, a length of 10μm-30μm, and a carboxyl content of 2wt%-6wt%.

[0009] Further specifying, the metal salt electrolyte is selected from aluminum nitrate nonahydrate, aluminum chloride hexahydrate, or magnesium nitrate.

[0010] Further specified, in the MWCNTs suspension, the mass ratio of metal salt to carboxylated multi-walled carbon nanotubes is (0.5-2):1; the volume ratio of anhydrous ethanol to acetone is (0.8-1):1, preferably 1:1; and the concentration of carboxylated multi-walled carbon nanotubes is 0.25 mg / mL-1.0 mg / mL.

[0011] Further specifying, in step 2, the electrophoretic deposition voltage is 20V-60V, the distance between the anode and cathode is 30mm-100mm, and the deposition time is 30s-120s.

[0012] Further specifying, the resin matrix of the composite prepreg is selected from thermoplastic resin or thermosetting resin.

[0013] Furthermore, the thermoplastic resin is selected from polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyetherimide (PEI), polyimide (PI), or polyaryletherketone (PAEK).

[0014] Furthermore, the thermosetting resin is selected from epoxy resin, bismaleimide resin (BMI) or phenolic resin (PF).

[0015] Further specifying, in step 3, the layup sequence of the laminated structure is a 2 / 1, 3 / 2, or 4 / 3 structure in which titanium plates and composite prepregs are alternately stacked.

[0016] Further specifying, in step 3, the hot pressing molding process is as follows: under pre-pressure, the temperature is raised to the melting temperature or curing temperature of the resin, then pressure is applied and the temperature is maintained, and finally pressure is maintained and the temperature is cooled.

[0017] Another objective of this invention is to provide a titanium alloy-carbon fiber reinforced resin matrix material structure prepared by any of the above methods, wherein a MWCNT network structure transition layer is formed between the titanium plate layer and the composite material layer.

[0018] This invention employs electrophoretic deposition technology to uniformly deposit multi-walled carbon nanotubes (MWCNTs) on the surface of a pretreated titanium plate, constructing a continuous, uniform, and strongly adherent conductive nano-network interface layer, thereby significantly improving the electromagnetic shielding effectiveness and interfacial bonding performance of the titanium alloy-carbon fiber reinforced resin base composite structure.

[0019] The core of this invention is to form a uniform, continuous, and firmly bonded three-dimensional conductive network of MWCNTs at the titanium alloy / composite material interface by optimizing electrophoretic deposition process parameters. This network not only enhances the mechanical interlocking effect of the interface but also provides an efficient conductive path, promoting multiple reflections and absorption losses of electromagnetic waves. Simultaneously, its shielding mechanism shifts from the original reflection-dominated model to a more superior reflection-absorption synergistic mode. The process of this invention is stable and reliable, providing a practical technical solution for developing lightweight, high-strength, and efficient electromagnetic shielding structure-functional integrated metal / composite materials.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The conductive interface layer constructed under the deposition conditions of MWCNTs suspension concentration of 0.75 mg / mL and deposition time of 90 s, the constructed conductive interface layer improved the total shielding effectiveness of the titanium alloy-carbon fiber reinforced resin base composite structure in the X band (8.2–12.4 GHz) from 44.63 dB of sandblasting treatment alone to 64.62 dB, an increase of 44.8%, which can meet the stringent requirements of high-end equipment for ultra-high shielding effectiveness.

[0021] (2) The introduction of the MWCNTs interface layer changes the shielding mechanism from the traditional "reflection-dominated" mode to a "reflection-absorption synergy" mode. While maintaining stable reflection loss, it significantly improves absorption loss, effectively reduces electromagnetic secondary pollution, and is of great significance for the protection of surrounding precision electronic equipment.

[0022] For a deeper understanding of the features and technical content of this invention, please refer to the accompanying detailed description and drawings. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0023] Figure 1 This is a SEM image of the titanium plate surface after electrophoretic deposition under optimal parameters (90s, 0.75mg / mL), showing a uniform MWCNT network coverage.

[0024] Figure 2 This is a diagram of the hot pressing process used in this invention, showing the temperature-pressure-time parameters for forming the CF / PEEK-Ti laminate structure.

[0025] Figure 3 The electromagnetic shielding performance of CF / PEEK-Ti treated with the present invention and that treated with sandblasting alone was compared in the X-band. The results show that the MWCNTs interface layer improves the overall shielding effectiveness (SE). T It increased by 44.8%. Detailed Implementation

[0026] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0027] Example 1 This embodiment provides an interface enhancement method based on MWCNTs to improve the electromagnetic shielding effectiveness of a titanium alloy-carbon fiber reinforced polyether ether ketone (CF / PEEK-Ti) laminate structure. This method involves constructing a uniform MWCNT conductive network on the surface of the titanium alloy using an electrophoretic deposition process. Figure 1 As shown, under the parameters of 90 s electrophoretic deposition time and 0.75 mg / mL carboxylated multi-walled carbon nanotube concentration, a complete and tightly connected MWCNT network structure was formed on the surface of the titanium plate. This structure is the basis for achieving efficient interfacial conductivity and electromagnetic loss, and specifically includes the following steps: (1) Pretreatment of titanium plate surface by sandblasting. A 0.3 mm thick industrial pure titanium TA2 sheet was selected as the metal layer material. The surface of the TA2 sheet was sandblasted using 180 mesh (corresponding to a particle size of approximately 80 µm) brown fused alumina sand as the blasting medium. The sandblasting process parameters were set as follows: nozzle distance from the titanium plate surface was 100 mm, blasting angle was 90°, blasting pressure was controlled at 0.2 MPa, and single-sided blasting time was 20 s. After sandblasting, the titanium plate was ultrasonically cleaned in anhydrous ethanol and acetone for 5 min in sequence to remove surface oil and residual brown fused alumina sand particles. After cleaning, it was dried at room temperature for later use. This step can effectively remove the natural oxide layer on the surface of the titanium plate and form a uniform micro-rough structure, thereby improving the mechanical interlocking ability between the titanium plate and the resin layer.

[0028] (2) Preparation of MWCNTs electrophoresis suspension. Carboxylated multi-walled carbon nanotubes (size specifications: outer diameter 5-15nm, inner diameter 2-5nm, length 10-30μm, carboxyl content 3.86wt%) and aluminum nitrate nonahydrate (purity 99.99%) were accurately weighed at a mass ratio of 1:1 and placed in a mixed solvent of anhydrous ethanol and acetone at a volume ratio of 1:1 to prepare a MWCNTs suspension with a carboxylated multi-walled carbon nanotube concentration of 0.75mg / mL. The suspension was then dispersed using an ultrasonic disperser with an ultrasonic power of 480W. To ensure that the temperature of the dispersion remained below 40℃ (below the boiling point of acetone 56.53℃), a pulse mode of 1 second operation followed by 1 second interval was used, and the dispersion was ultrasonically dispersed for 2 hours under ice-water bath conditions. Meanwhile, the mouth of the beaker was sealed with plastic wrap to prevent changes in the concentration of the suspension due to solvent evaporation, and finally a MWCNTs suspension with uniform dispersion and good stability was obtained with a concentration of 0.75 mg / mL.

[0029] (3) Electrophoretic deposition of a conductive interface layer of MWCNTs. Using the titanium plate treated in step (1) as the cathode and the stainless steel sheet as the anode, the distance between the two plates was fixed at 50 mm, and the assembled electrode was immersed in the suspension prepared in step (2). At room temperature, a constant voltage was provided by a DC regulated power supply, the deposition voltage was set to 30V, and the deposition time was set to 90s. During the deposition process, the suspension was kept still to avoid disturbance affecting the uniformity of the deposition. After deposition, the titanium plate was vertically and uniformly lifted out of the liquid surface and placed in an oven at 100℃ for 10 min to allow the MWCNTs network to form a stable bond with the titanium plate substrate. It was then stored at room temperature. At this point, a uniform, dense MWCNTs network structure layer with continuous conductive pathways had been formed on the surface of the titanium plate, such as... Figure 1 As shown.

[0030] (4) Hot pressing of CF / PEEK-Ti laminate. AS-4 carbon fiber reinforced polyether ether ketone (CF / PEEK) prepreg (APC-2, carbon fiber volume content 59%) was selected as the composite material layer, and a 0.1 mm thick PEEK film was selected as the adhesive layer. A 3 / 2 layup structure was used for the stacking, and the specific layup sequence from bottom to top was: Ti-PEEK film-[0° / 0° / 90° / 90°]CF / PEEK-PEEK film-Ti-PEEK film-[90° / 90° / 0° / 0°]CF / PEEK-PEEK film-Ti. When each layer was laid, it was ensured that the layers were aligned and flat, without wrinkles or foreign matter inclusions. Among them, Ti is the modified titanium plate with MWCNTs deposited layer prepared in step (3). The stacked laminate blank was placed in the mold and placed in the middle of the heating plate of the flat vulcanizing machine. The specific hot pressing process is as follows. Figure 2 As shown, under a pre-pressure of 0.2 MPa, the temperature is increased to 390°C at a heating rate of 3°C / min. During this process, the PEEK resin gradually melts and flows, fully wetting the surface of the titanium plate and the carbon fiber reinforcement. The temperature is held at 390°C for 30 minutes, while the pressure is increased to 1.6 MPa to ensure that the PEEK resin flows fully and removes internal air bubbles, achieving complete interfacial bonding. Finally, the material is naturally cooled to room temperature under a pressure of 1.6 MPa and then demolded to obtain the CF / PEEK-Ti laminated structure.

[0031] Testing showed that the CF / PEEK-Ti laminate prepared in this embodiment achieved a total electromagnetic shielding effectiveness (SET) of 64.62 dB in the X-band (8.2-12.4 GHz). The optimized electrophoretic parameters (0.75 mg / mL, 90 s) enabled MWCNTs to form a continuous and dense conductive network on the surface of the titanium plate microgrooves, effectively avoiding agglomeration and realizing the transformation of the electromagnetic shielding mechanism from a reflection-based to a "reflection-absorption" synergistic mode.

[0032] Comparative Example 1: Sandblasted titanium plate (without electrophoretic deposition of MWCNTs) This comparative example is used to evaluate the influence of the MWCNTs conductive interface layer on the performance of the laminate in this invention. A 0.3 mm thick TA2 titanium plate was selected and subjected to sandblasting and solvent cleaning according to step (1) of Example 1 to obtain a slightly rough surface, but the MWCNTs electrophoretic deposition treatment in steps (2) and (3) was not performed. Subsequently, a CF / PEEK-Ti laminate structure was prepared according to the layup method and hot-pressing process in step (4) of Example 1. The resulting laminate was used as the reference material. Its electromagnetic shielding effectiveness is as follows: Figure 3 As shown, the conductivity is only 44.63 dB, significantly lower than that of Example 1. This comparative example illustrates that simply creating a rough interface through sandblasting cannot form an effective conductive path.

[0033] Comparative Example 2: Electrophoretic deposition of MWCNTs for 30 s at a concentration of 0.25 mg / mL The only difference between this comparative example and Example 1 is the electrophoretic deposition parameters: the MWCNTs suspension concentration is 0.25 mg / mL, and the deposition time is 30 s. All other steps are exactly the same as in Example 1. After treatment with these parameters, the MWCNTs deposition layer on the titanium plate surface exhibits uneven coverage and poor network continuity. Its electromagnetic shielding effectiveness is significantly lower than that of Example 1, at only 45.64 dB.

[0034] Comparative Example 3: Electrophoretic deposition of MWCNTs for 120 s at a concentration of 1 mg / mL The only difference between this comparative example and Example 1 is the electrophoretic deposition parameters: the MWCNTs suspension concentration was 1.0 mg / mL, and the deposition time was 120 s. All other steps were consistent with Example 1. Due to the excessively high MWCNTs concentration and long deposition time, the nanotubes excessively accumulated and agglomerated on the titanium plate surface, forming a locally thick and uneven deposition layer. This structure not only reduced the uniformity of the interface layer, but also resulted in high contact resistance between the agglomerates, thus weakening the overall efficiency of the conductive network. Its electromagnetic shielding effectiveness was significantly lower than that of Example 1, at only 50.03 dB.

[0035] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. An interface enhancement method for improving the electromagnetic shielding effectiveness of a titanium alloy-carbon fiber reinforced resin matrix laminate structure based on MWCNTs, characterized in that, The method comprises the following steps: Step 1, removing the surface oxide layer of the titanium plate and forming a rough structure, and then solvent cleaning; Step 2, taking the titanium plate treated in step 1 as a cathode, taking a conductive material as an anode, placing the two electrodes in a MWCNTs suspension, and performing electrophoretic deposition under a set voltage to form a MWCNTs conductive network structure layer on the surface of the titanium plate, and then drying; Step 3, alternately stacking the titanium plate treated in step 2 and a carbon fiber reinforced resin matrix composite prepreg, and hot pressing to form a product. The MWCNTs suspension is prepared by adding surface functionalized MWCNTs and a metal salt electrolyte capable of providing positive ions into an ethanol-ketone mixed solvent and performing ultrasonic dispersion.

2. The method of claim 1, wherein, In step 1, one or more of sand blasting, mechanical polishing, laser texturing, chemical etching or anodic oxidation is used to form a rough structure.

3. The method of claim 1, wherein, The surface functionalized MWCNTs are carboxylated multi-walled carbon nanotubes with an inner diameter of 2-5 nm, an outer diameter of 5-15 nm, a length of 10-30 μm, and a carboxyl content of 2-6 wt%.

4. The method of claim 1, wherein, The metal salt electrolyte is selected from aluminum nitrate nonahydrate, aluminum chloride hexahydrate or magnesium nitrate.

5. The method of claim 1, wherein, In the MWCNTs suspension, the mass ratio of the metal salt to the carboxylated multi-walled carbon nanotubes is 0.5:1-2:1, the volume ratio of anhydrous ethanol to acetone is 0.8:1-1.2:1, and the concentration of the carboxylated multi-walled carbon nanotubes is 0.25-1.0 mg / mL.

6. The method of claim 1, wherein, The electrophoretic deposition voltage is 20-60 V, the distance between the cathode and the anode is 30-100 mm, and the deposition time is 30-120 s.

7. The method of claim 1, wherein, The resin matrix of the composite prepreg is selected from a thermoplastic resin or a thermosetting resin; the thermoplastic resin is selected from polyether ether ketone, polyphenylene sulfide, polyether imide, polyimide or polyaryletherketone; and the thermosetting resin is selected from epoxy resin, bismaleimide resin or phenolic resin.

8. The method of claim 1, wherein, The layering sequence is a 2 / 1, 3 / 2 or 4 / 3 structure in which the titanium plate and the composite prepreg are alternately stacked.

9. The method of claim 1 wherein, The hot pressing process is: heating to the melting temperature or curing temperature of the resin under a pre-pressure, then pressurizing and holding, and finally pressure holding and cooling.

10. A titanium alloy-carbon fiber reinforced resin matrix laminate structure produced by any of the methods of claims 1 to 9, characterized by, A MWCNTs network structure transition layer is formed between the titanium plate layer and the composite material layer.

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