Composite pipe and method of manufacture and use thereof

Abstract

The application discloses a composite pipe and a preparation method and application thereof, relates to the technical field of deep-sea functional shells, and aims at solving the problems of poor impact resistance, compression strength and corrosion resistance of the composite pipe. The composite pipe comprises, from outside to inside, a carbon fiber winding layer, an outer aluminum alloy layer, a high-entropy alloy honeycomb core layer and an inner aluminum alloy layer. The high-entropy alloy honeycomb core layer comprises a high-entropy alloy layer forming a honeycomb structure and polyurethane filled in the honeycomb structure. The application further provides a preparation method of the composite pipe. The composite pipe can be applied in a deep-sea hydraulic actuator.

Description

Technical Field

[0001] This invention relates to the field of deep-sea functional shell technology, and in particular to a composite tube, its preparation method, and its application. Background Technology

[0002] The deep-sea working environment is characterized by high pressure, low temperature, strong corrosion, and alternating loads, which places stringent requirements on the structural performance of core components of deep-sea equipment. Among these, the deep-sea hydraulic actuator, as a key drive unit for deep-sea exploration and resource development equipment, must simultaneously meet comprehensive technical requirements regarding its shell, including lightweight design, high compressive strength, fatigue resistance, corrosion resistance, and structural sealing. Improvements in the shell's performance will drive the development of deep-sea equipment towards greater operating depths and longer service lives.

[0003] Traditional deep-sea hydraulic actuators often use single-metal materials such as titanium alloys and high-strength steel for their functional shells, which suffer from problems such as high density, susceptibility to corrosion, and insufficient vibration and noise reduction performance. While single-metal materials possess good mechanical stability and corrosion resistance, their high density increases overall weight, making underwater buoyancy adjustment difficult and increasing transportation and deployment costs. Furthermore, in the high-pressure environment of the deep sea, pure metal shells are prone to plastic deformation due to localized stress concentration, potentially leading to fatigue cracking after long-term service. Traditional metal honeycomb structures, such as aluminum alloy honeycomb cores, offer high strength but poor impact resistance, while paper-based and polymer honeycomb cores provide strong cushioning but have weak load-bearing capacity. Therefore, to meet the development requirements of deep-sea equipment for impact resistance, high compressive strength, vibration and noise reduction performance, and corrosion resistance, there is an urgent need to develop a new type of composite tubing and its supporting manufacturing method. Summary of the Invention

[0004] The purpose of this invention is to provide a composite pipe, its preparation method and application. The composite pipe is lightweight and has the properties of strong impact resistance, high compressive strength and strong corrosion resistance.

[0005] To achieve the above objectives, a first aspect of the present invention provides a composite tube, wherein the composite tube comprises, from the outside to the inside, a carbon fiber winding layer, an outer aluminum alloy layer, a high-entropy alloy honeycomb core layer, and an inner aluminum alloy layer; wherein the high-entropy alloy honeycomb core layer comprises a high-entropy alloy layer forming a honeycomb structure, and polyurethane filled in the honeycomb structure.

[0006] Compared with existing technologies, the composite tube of the present invention comprises, from the outside to the inside, a carbon fiber winding layer, an outer aluminum alloy layer, a high-entropy alloy honeycomb core layer, and an inner aluminum alloy layer. The high-entropy alloy honeycomb core layer includes a high-entropy alloy layer forming a honeycomb structure, and polyurethane filled in the honeycomb structure, with each layer forming a synergistic effect. Compared with a single metal shell, the present invention achieves lightweighting through the composite structure of the carbon fiber winding layer, the outer aluminum alloy layer, the high-entropy alloy honeycomb core layer, and the inner aluminum alloy layer. Compared with traditional composite structures, the high-entropy alloy honeycomb core layer, in synergy with the inner and outer aluminum alloy layers and the carbon fiber winding layer, can significantly improve the corrosion resistance and strength of the composite tube. Filling the honeycomb structure with polyurethane not only prevents the core from collapsing, but also enhances the compressive and impact resistance of the composite tube, while effectively eliminating the problem of interlayer stress concentration.

[0007] Furthermore, the carbon fiber winding layer comprises carbon fiber and adhesive; wherein, by mass percentage, the carbon fiber winding layer comprises 66%-76% carbon fiber and 24%-30% adhesive.

[0008] In this invention, when the content of carbon fiber and adhesive in the carbon fiber winding layer meets the above-mentioned range, the carbon fiber winding layer is more tightly bonded to the outer aluminum alloy layer, and the carbon fiber winding layer is more uniform and dense, thereby giving the composite pipe better specific strength and specific stiffness, fatigue resistance and better corrosion resistance.

[0009] Furthermore, based on the mass percentage of the outer aluminum alloy layer or the inner aluminum alloy layer, each of the outer aluminum alloy layer and the inner aluminum alloy layer independently contains 0.4%-0.8% silicon, 0.01%-0.7% iron, 0.1%-0.4% copper, 0.01%-0.5% manganese, 0.8%-1.2% magnesium, 0.05%-0.35% chromium, 0.01%-0.5% zinc, 0.01%-0.15% titanium, with the balance being aluminum.

[0010] In this invention, when the composite pipe contains the above-mentioned type of outer aluminum alloy layer and inner aluminum alloy layer, the corrosion resistance, impact resistance and compressive strength of the composite pipe can be further improved.

[0011] Furthermore, the high-entropy alloy layer comprises Co, Cr, Fe, Ni, and Mn; wherein, by mass percentage of the high-entropy alloy layer, the content of Co is 19%-23%, the content of Cr is 16%-21%, the content of Fe is 18%-22%, the content of Ni is 19%-23%, and the content of Mn is 16%-21%.

[0012] In this invention, when the high-entropy alloy layer contains Co, Cr, Fe, Ni and Mn, and the content of each metal element meets the above-mentioned range, the corrosion resistance, impact resistance and compressive strength of the composite pipe can be further improved.

[0013] A second aspect of the present invention provides a method for preparing the above-mentioned composite tube, wherein the preparation method includes:

[0014] After the inner aluminum alloy layer is made into a tubular shape, laser cladding technology is used to form a honeycomb structure of high entropy alloy powder on the outer surface of the inner aluminum alloy layer.

[0015] The high-entropy alloy layer is pretreated, wherein the pretreatment includes anodizing and coupling agent treatment;

[0016] Polyurethane is filled into the pretreated high-entropy alloy layer to obtain a semi-finished pipe containing a high-entropy alloy honeycomb core layer and an inner aluminum alloy layer.

[0017] The outer aluminum alloy layer is spot-welded to the outer surface of the high-entropy alloy honeycomb core layer to obtain a tube containing an outer aluminum alloy layer, a high-entropy alloy honeycomb core layer and an inner aluminum alloy layer.

[0018] After carbon fiber is brought into contact with adhesive liquid, resin-impregnated carbon fiber is obtained. The resin-impregnated carbon fiber is then wound around the outer surface of the outer aluminum alloy layer of the tube, and then subjected to a first curing treatment to obtain the composite tube.

[0019] Compared with existing technologies, this invention uses laser cladding technology to prepare a high-entropy alloy layer with a honeycomb structure on the outer surface of the inner aluminum alloy layer, which can ensure the compactness of the honeycomb structure in the high-entropy alloy layer; the high-entropy alloy layer with honeycomb structure is subjected to anodizing treatment, and through this electrochemical method, a hard, porous γ-type aluminum oxide layer with an extremely high specific surface area is grown on the aluminum alloy surface. The porous γ-alumina film provides ideal mechanical interlocking conditions for subsequent coupling agent treatment and polyurethane embedding, thereby improving the bonding ability between polyurethane and aluminum alloys and high-entropy alloys. The outer surfaces of the outer aluminum alloy layer and the high-entropy alloy honeycomb core layer are firmly connected by spot welding. By winding impregnated carbon fibers around the outer surface of the outer aluminum alloy layer of the tube, the first curing treatment ensures that the carbon fiber winding layer is uniform and dense. Under the combined effect of each step, the resulting composite tube is lightweight and also has strong impact resistance, high compressive strength, and strong corrosion resistance.

[0020] Furthermore, the processing conditions of the laser cladding technology include: a powder feeding rate of 16-18 g / min for the high-entropy alloy powder, a laser power of 2500-3500 W, a laser scanning speed of 40-55 m / min, a laser energy density of 1.7-1.9 J / mm², an average diameter of 20-50 μm for the high-entropy alloy powder, a laser spot diameter of 3-4 mm, and a surface linear velocity of the inner aluminum alloy layer along the axial direction of 45-55 m / min.

[0021] In this invention, when at least one of the following parameters—the powder feeding rate of the high-entropy alloy powder, the laser power, the laser scanning speed, the laser energy density, the spherical particle diameter of the high-entropy alloy powder, the laser spot diameter, and the surface linear velocity of the inner aluminum alloy layer along the axial direction—satisfies the above-mentioned range, the honeycomb structure of the high-entropy alloy layer produced has higher density, thereby further improving the impact resistance and compressive strength of the composite tube.

[0022] Furthermore, the anodizing process includes: oxidizing the high-entropy alloy layer as the anode, using a 15-20wt% sulfuric acid aqueous solution as the electrolyte, with the electrolyte temperature at 18-22℃ and the oxidation time at 30-40 min.

[0023] Further, the coupling agent treatment includes: adding a silane coupling agent to ethanol and / or propanol for pre-hydrolysis to obtain a silane coupling agent solution; immersing the anodized high-entropy alloy layer in the silane coupling agent solution; adjusting the pH of the silane coupling agent solution to 4.5-5.5 using an organic acid; removing the layer after immersion for 2-5 minutes; and performing a second curing treatment at 100-120°C.

[0024] Furthermore, the silane coupling agent is selected from γ-aminopropyltriethoxysilane and / or γ-glycidoxypropyltrimethoxysilane.

[0025] Furthermore, the concentration of the silane coupling agent solution is 1-2 wt%.

[0026] Further, filling the pretreated high-entropy alloy layer with polyurethane includes:

[0027] The first polyether polyol is prepolymerized with a polyisocyanate to obtain a prepolymer;

[0028] The second polyether polyol, N,N-dimethylformamide, chain extender, organosilicon surfactant and water are first mixed at 30-40°C to obtain a mixture.

[0029] The pretreated high-entropy alloy layer is placed in a mold, and then the prepolymer and the mixture are mixed for a second time. The material after the second mixture is injected into the mold and the mold is closed. Foaming treatment is performed, and the composite material blank is obtained after demolding.

[0030] The composite material blank is subjected to demolding post-processing.

[0031] Furthermore, the prepolymerization temperature is 70-80°C.

[0032] Furthermore, the mass ratio of the first polyether polyol to the polyisocyanate is 1:1.2-1.8.

[0033] Further, based on the mass percentage of the mixture, the content of the second polyether polyol is 45-55%, the content of N,N-dimethylformamide is 15-20%, the content of the chain extender is 2-6%, the content of the organosilicon surfactant is 18-25%, and the balance is water.

[0034] Furthermore, the mass ratio of the prepolymer to the mixture is 1:0.6-0.9.

[0035] Further, the second mixing includes stirring at 30-40°C for 10-15 seconds at a stirring rate of 1500-3000 rpm.

[0036] Furthermore, the foaming process includes foaming at 75-95°C for 60-90 minutes.

[0037] Furthermore, the method for preparing the adhesive liquid includes:

[0038] Component A is obtained by mixing 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether; wherein the mass ratio of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether is 1:0.8-0.9:1-2.

[0039] 4,4-Diaminoxylenemethane is mixed with an accelerator to obtain component B; wherein the mass ratio of 4,4-diaminoxylenemethane to the accelerator is 0.3-2.7:1;

[0040] After compounding component A and component B at a mass ratio of 1:0.3-0.4, the mixture is stirred and degassed to obtain an epoxy resin solution, which is the adhesive solution.

[0041] A third aspect of the present invention provides an application of the above-mentioned composite tube in a deep-sea hydraulic actuator.

[0042] Compared with the prior art, the beneficial effects of the composite tube provided by the present invention in the application of deep-sea hydraulic actuators are the same as the beneficial effects of the composite tube described in the above technical solutions, and will not be repeated here. Attached Figure Description

[0043] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0044] Figure 1 This is a schematic diagram of the composite pipe in the embodiment;

[0045] Figure 2 This is a cross-sectional view of the composite pipe in the embodiment;

[0046] Figure 3 This is a schematic diagram of the high-entropy alloy honeycomb core layer of the composite tube in the embodiment;

[0047] Figure label:

[0048] 1-Carbon fiber winding layer; 2-Outer aluminum alloy layer;

[0049] 3-High-entropy alloy honeycomb core layer; 4-Inner aluminum alloy layer;

[0050] 301 - High entropy alloy layer, 302 - Polyurethane. Detailed Implementation

[0051] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0052] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature.

[0053] like Figure 1 , Figure 2 and Figure 3 As shown, in a first aspect, embodiments of the present invention provide a composite tube, wherein the composite tube comprises, from the outside to the inside, a carbon fiber winding layer 1, an outer aluminum alloy layer 2, a high-entropy alloy honeycomb core layer 3 and an inner aluminum alloy layer 4; wherein the high-entropy alloy honeycomb core layer 3 comprises a high-entropy alloy layer 301 forming a honeycomb structure, and polyurethane 302 filled in the honeycomb structure.

[0054] Using the above technical solution, the composite tube, from the outside to the inside, includes a carbon fiber winding layer 1, an outer aluminum alloy layer 2, a high-entropy alloy honeycomb core layer 3, and an inner aluminum alloy layer 4. The high-entropy alloy honeycomb core layer 3 comprises a high-entropy alloy layer 301 forming a honeycomb structure, and polyurethane 302 filled in the honeycomb structure, with each layer forming a synergistic effect. Compared with a single metal shell, the present invention achieves lightweighting through the composite structure of the carbon fiber winding layer 1, the outer aluminum alloy layer 2, the high-entropy alloy honeycomb core layer 3, and the inner aluminum alloy layer 4. Compared with traditional composite structures, the high-entropy alloy honeycomb core layer 3, in synergy with the inner and outer aluminum alloy layers and the carbon fiber winding layer 1, can significantly improve the corrosion resistance and strength of the composite tube. Filling the honeycomb structure of the high-entropy alloy layer 301 with polyurethane 302 can not only prevent the core from collapsing, but also enhance the compressive and impact resistance of the composite tube, while effectively eliminating the problem of interlayer stress concentration.

[0055] In some embodiments, the inner diameter of the composite tube can be 94-98 mm.

[0056] In some embodiments, the carbon fiber winding layer 1 comprises carbon fiber and an adhesive; wherein, by weight percentage, the carbon fiber winding layer 1 comprises 66%-76% carbon fiber and 24%-34% adhesive.

[0057] When the carbon fiber and adhesive content in the carbon fiber winding layer 1 meets the above range, the carbon fiber winding layer 1 is more tightly bonded to the outer aluminum alloy layer 2, and the carbon fiber winding layer 1 is more uniform and dense, thereby giving the composite pipe better specific strength and specific stiffness, fatigue resistance and better corrosion resistance.

[0058] For example, the carbon fiber content of the carbon fiber winding layer 1 can be 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, or 76% by weight, or any range consisting of any two points; the adhesive content can be 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, or 34%, or any range consisting of any two points. Preferably, the carbon fiber winding layer 1 contains 66%-72% carbon fiber and 28%-34% adhesive by weight.

[0059] In some embodiments, the adhesive is cured epoxy resin. When the adhesive in the carbon fiber winding layer 1 is cured epoxy resin, and when the adhesive content in the carbon fiber winding layer 1 meets the requirement of 24%-30%, the adhesive in the carbon fiber winding layer 1 is less prone to aging, making the carbon fiber winding layer 1 bond more tightly with the outer aluminum alloy layer 2, and the carbon fiber winding layer 1 more uniform and dense, thereby giving the composite pipe better specific strength and specific stiffness, fatigue resistance and better corrosion resistance.

[0060] In some embodiments, the tensile strength of the carbon fiber is greater than or equal to 4.5 GPa, preferably greater than or equal to 4.8 GPa. For example, the carbon fiber may be T700 grade carbon fiber.

[0061] In some embodiments, the density of the carbon fiber winding layer 1 is 1.55-1.65 g / cm³, and the thickness of the carbon fiber winding layer 1 is 4-6 mm. When the density and / or thickness of the carbon fiber winding layer 1 meet the above ranges, it is beneficial to improve the strength and corrosion resistance of the composite pipe. Preferably, the density of the carbon fiber winding layer 1 is 1.6-1.65 g / cm³.

[0062] In some embodiments, the outer aluminum alloy layer 2 and the inner aluminum alloy layer 4, by mass percentage, each independently contain 0.4%-0.8% silicon, 0.01%-0.7% iron, 0.1%-0.4% copper, 0.01%-0.5% manganese, 0.8%-1.2% magnesium, 0.05%-0.35% chromium, 0.01%-0.5% zinc, 0.01%-0.15% titanium, with the balance being aluminum.

[0063] By adopting the above technical solution, when the composite pipe of the present invention contains the above-mentioned type of outer aluminum alloy layer 2 and inner aluminum alloy layer 4, the corrosion resistance, impact resistance and compressive strength of the composite pipe can be further improved.

[0064] Preferably, based on the mass percentage of the outer aluminum alloy layer 2 or the inner aluminum alloy layer 4, each of the outer aluminum alloy layer 2 and the inner aluminum alloy layer 4 independently comprises 0.5%-0.6% silicon, 0.01%-0.5% iron, 0.2%-0.3% copper, 0.01%-0.15% manganese, 0.95%-1.05% magnesium, 0.15%-0.25% chromium, 0.01%-0.25% zinc, and 0.01%-0.15% titanium, with the balance being aluminum. For example, the outer aluminum alloy layer 2 and the inner aluminum alloy layer 4 may be selected from 6061-T6 aluminum alloy.

[0065] In some embodiments, the thickness of the outer aluminum alloy layer 2 and the inner aluminum alloy layer 4 is independently 2-4 mm. When the thickness of the outer aluminum alloy layer 2 and the inner aluminum alloy layer 4 meets the above range, the synergistic effect with the carbon fiber winding layer 1 and the high-entropy alloy honeycomb core layer 3 is beneficial to improving the compressive strength and impact resistance of the composite tube. Preferably, the thickness of the outer aluminum alloy layer 2 and the inner aluminum alloy layer 4 is independently 2.5-3.5 mm.

[0066] In some embodiments, the high-entropy alloy layer 301 comprises Co, Cr, Fe, Ni, and Mn; wherein, by mass percentage, the content of Co is 19%-23%, the content of Cr is 16%-21%, the content of Fe is 18%-22%, the content of Ni is 19%-23%, and the content of Mn is 16%-21%.

[0067] By adopting the above technical solution, when the high-entropy alloy layer 301 contains Co, Cr, Fe, Ni and Mn, and the content of each metal element meets the above range, the corrosion resistance, impact resistance and compressive strength of the composite pipe can be further improved.

[0068] For example, based on the mass percentage of the high-entropy alloy layer 301, the content of Co can be 19%, 20%, 21%, 22%, or 23%, or any range consisting of any two points; the content of Cr can be 16%, 17%, 18%, 19%, 20%, or 21%, or any range consisting of any two points; the content of Fe can be 18%, 19%, 20%, 21%, or 22%, or any range consisting of any two points; the content of Ni can be 19%, 20%, 21%, 22%, or 23%, or any range consisting of any two points; and the content of Mn can be 16%, 17%, 18%, 19%, 20%, or 21%. Preferably, based on the mass percentage of the high-entropy alloy layer 301, the content of Co is 20.5%-21.5%, the content of Cr is 18.5%-19.5%, the content of Fe is 19.5%-20.5%, the content of Ni is 20.5%-21.5%, and the content of Mn is 18.5%-19.5%.

[0069] In some embodiments, the honeycomb structure of the high-entropy alloy layer 301 is a regular hexagonal honeycomb structure. In this invention, there are no special requirements for the side length of the honeycomb structure; those skilled in the art can adjust it according to actual conditions. Preferably, the side length of the regular hexagonal honeycomb structure is 2.25-2.75 mm, and the foil thickness of the honeycomb structure is 0.08-0.14 mm. When the side length and foil thickness of the regular hexagonal honeycomb structure meet the above limitations, it is beneficial to improve the load-bearing capacity per unit volume of the honeycomb and to improve the energy absorption performance of the honeycomb, thereby enhancing the compressive and impact resistance of the composite tube.

[0070] In some embodiments, the density of polyurethane 302 filled in the honeycomb structure is 245-255 kg / m³. For example, the density of polyurethane 302 filled in the honeycomb structure can be 245 kg / m³, 246 kg / m³, 247 kg / m³, 248 kg / m³, 249 kg / m³, 250 kg / m³, 251 kg / m³, 252 kg / m³, 253 kg / m³, 254 kg / m³, or 255 kg / m³, or a range consisting of any two values. Preferably, the density of polyurethane 302 filled in the honeycomb structure is 247-253 kg / m³.

[0071] In some embodiments, the thickness of the high-entropy alloy honeycomb core layer 3 is 2-6 mm. For example, the thickness of the high-entropy alloy honeycomb core layer 3 can be 2 mm, 3 mm, 4 mm, 5 mm or 6 mm, or any range formed by any two point values.

[0072] When the density of polyurethane 302 in the high-entropy alloy honeycomb core layer 3 and / or the thickness of the high-entropy alloy honeycomb core layer 3 meet the above range, the high-entropy alloy honeycomb core layer 3 is more robust and less prone to collapse, thereby further enhancing the compressive and impact resistance of the composite pipe.

[0073] In some embodiments, the high-entropy alloy honeycomb core layer 3 contains a very small amount of silane coupling agent and / or silanol, which can be ignored due to their small content.

[0074] In some embodiments, the carbon fiber winding layer 1 is connected to the outer aluminum alloy layer 2 by an adhesive, the outer aluminum alloy layer 2 is connected to the high-entropy alloy honeycomb core layer 3 by spot welding, and the high-entropy alloy honeycomb core layer 3 is fabricated directly on the outer surface of the inner aluminum alloy layer 4 by additive manufacturing, specifically by laser cladding technology, thereby forming a connection with the inner aluminum alloy layer 4.

[0075] In some embodiments, the burst pressure of the composite pipe is greater than or equal to 190 MPa, the axial compressive strength of the composite pipe is greater than or equal to 255 MPa, and the circumferential tensile strength of the composite pipe is 530 MPa. Preferably, the burst pressure of the composite pipe is greater than or equal to 200 MPa, the axial compressive strength of the composite pipe is greater than or equal to 270 MPa, and the circumferential tensile strength of the composite pipe is 550 MPa.

[0076] Secondly, embodiments of the present invention also provide a method for preparing the above-mentioned composite tube, wherein the preparation method includes:

[0077] After the inner aluminum alloy layer 4 is made into a tube, laser cladding technology is used to form a honeycomb structure high entropy alloy layer 301 on the outer surface of the inner aluminum alloy layer 4 using high entropy alloy powder.

[0078] The high-entropy alloy layer 301 is pretreated, wherein the pretreatment includes anodizing and coupling agent treatment;

[0079] Polyurethane 302 is filled into the pretreated high-entropy alloy layer 301 to obtain a semi-finished pipe containing a high-entropy alloy honeycomb core layer 3 and an inner aluminum alloy layer 4.

[0080] The outer aluminum alloy layer 2 is spot-welded to the outer surface of the high-entropy alloy honeycomb core layer 3 to obtain a tube containing the outer aluminum alloy layer 2, the high-entropy alloy honeycomb core layer 3 and the inner aluminum alloy layer 4.

[0081] After carbon fiber is brought into contact with adhesive liquid, impregnated carbon fiber is obtained. The impregnated carbon fiber is then wound around the outer surface of the outer aluminum alloy layer 2 of the tube and subjected to a first curing treatment to obtain the composite tube.

[0082] Using the above technical solution, a high-entropy alloy layer 301 with a honeycomb structure is prepared on the outer surface of the inner aluminum alloy layer 4 by laser cladding technology, which can ensure the compactness of the honeycomb structure in the high-entropy alloy layer 301; the high-entropy alloy layer 301 with a honeycomb structure is subjected to anodizing treatment, and through this electrochemical method, a hard, porous γ-type aluminum oxide with an extremely high specific surface area is grown on the aluminum alloy surface. The porous γ-alumina film provides ideal mechanical interlocking conditions for subsequent coupling agent treatment and polyurethane 302 embedding, thereby improving the bonding ability of polyurethane 302 with aluminum alloy and high-entropy alloy. The outer surfaces of the outer aluminum alloy layer 2 and the high-entropy alloy honeycomb core layer 3 are firmly connected by spot welding. By winding impregnated carbon fiber around the outer surface of the outer aluminum alloy layer 2 of the tube, the first curing treatment ensures that the carbon fiber winding layer 1 is uniform and dense. Under the combined effect of each step, the resulting composite tube is lightweight and also has strong impact resistance, high compressive strength, and strong corrosion resistance.

[0083] In some embodiments, the processing conditions of the laser cladding technology include: a powder feeding rate of 16-18 g / min for high-entropy alloy powder, a laser power of 2500-3500 W, a laser scanning speed of 40-55 m / min, a laser energy density of 1.7-1.9 J / mm², an average diameter of 20-50 μm for the high-entropy alloy powder, a laser spot diameter of 3-4 mm, and a surface linear velocity of the inner aluminum alloy layer 4 along the axial direction of 45-55 m / min.

[0084] Using the above technical solution, when at least one of the following parameters—powder feeding rate of high-entropy alloy powder, laser power, laser scanning speed, laser energy density, spherical particle diameter of high-entropy alloy powder, laser spot diameter, and surface linear velocity of the inner aluminum alloy layer 4 along the axial direction—satisfies the above-mentioned range, the honeycomb structure of the resulting high-entropy alloy layer 301 exhibits higher density, thereby further improving the impact resistance and compressive strength of the composite tube. This invention does not impose any special limitations on the protective gas used in laser cladding technology; conventional protective gases in the art can be used, such as argon.

[0085] In some embodiments, the processing conditions of the laser cladding technology include: a powder feeding rate of 16.5-17.5 g / min for high-entropy alloy powder, a laser power of 2900-3100 W, a laser scanning speed of 47-53 m / min, and a laser energy density of 1.75-1.85 J / mm². 2 The high-entropy alloy powder has an average diameter of 20-50 μm, the laser spot diameter is 3.3-3.5 mm, and the surface linear velocity of the inner aluminum alloy layer 4 along the axial direction is 47-53 m / min.

[0086] In some embodiments, the high-entropy alloy powder is a high-entropy alloy powder that has undergone dehydration treatment; wherein, the dehydration treatment includes drying at 115-125°C for 2-3 hours.

[0087] In some embodiments, the pretreatment of the high-entropy alloy layer 301 includes a degreasing treatment before anodizing. In this invention, the degreasing treatment includes ultrasonic treatment of the honeycomb structure using an organic solvent, with an ultrasonic power of 100-150W, an ultrasonic temperature of 20-30℃, and an ultrasonic time of 15-20 min. The high-entropy alloy layer 301 after degreasing treatment can be dried to remove the organic solvent. Preferably, the drying process includes drying at 75-85℃ for 10-25 min.

[0088] In some embodiments, the anodizing process includes: oxidizing the high-entropy alloy layer 301 as the anode, using a 15-20wt% sulfuric acid aqueous solution as the electrolyte, the temperature of the electrolyte being 18-22°C, and the oxidation time being 30-40 min.

[0089] By employing the above technical solution, when the electrolyte, electrolyte temperature, and oxidation time used in the anodizing process meet the aforementioned ranges, an aluminum oxide film layer can be formed better on the aluminum alloy surface, thereby further improving the adhesion between the polyurethane 302 and the high-entropy alloy layer 301, which is beneficial for improving the impact resistance and compressive strength of the composite pipe. In this invention, there is no specific limitation on the specific type of cathode during the anodizing process, as long as the anode undergoes oxidation. For example, the cathode can be a stainless steel plate. In this invention, after the high-entropy alloy layer 301 has finished oxidizing, it is cleaned with deionized water to prevent residual acid from contaminating the aluminum oxide film layer.

[0090] In some embodiments, the coupling agent treatment includes: adding a silane coupling agent to ethanol and / or propanol for pre-hydrolysis to obtain a silane coupling agent solution; immersing the anodized high-entropy alloy layer 301 into the silane coupling agent solution; adjusting the pH of the silane coupling agent solution to 4.5-5.5 using an organic acid; removing the layer after immersion for 2-5 minutes; and performing a second curing treatment at 100-120°C.

[0091] In some embodiments, the silane coupling agent is selected from γ-aminopropyltriethoxysilane and / or γ-glycidoxypropyltrimethoxysilane.

[0092] In some embodiments, the concentration of the silane coupling agent solution is 1-2 wt%.

[0093] When the above technical solution is adopted, and the method of coupling agent treatment, the type of silane coupling agent and the concentration of silane coupling agent solution meet the above range, it is more conducive to the formation of silanol by silane coupling agent with ethanol and / or propanol, which further improves the bonding between polyurethane 302 and high-entropy alloy layer 301, thereby making the composite pipe with higher impact resistance and compressive strength.

[0094] In some embodiments, the pre-hydrolysis time in the coupling agent treatment is 30-60 minutes. In this invention, there is no particular limitation on the curing time in the coupling agent treatment; for example, the second curing treatment time can be 20-30 minutes. In this invention, there is no particular limitation on the amount of silane coupling agent solution used, as long as the high-entropy alloy layer 301 is completely immersed in the silane coupling agent.

[0095] In this invention, the concentration of the organic acid is not specifically limited, and those skilled in the art can adjust it according to actual conditions. Preferably, the concentration of the organic acid is 5wt%-10wt%. Preferably, the organic acid used to adjust the pH of the silane coupling agent solution is acetic acid and / or citric acid.

[0096] In some embodiments, filling the pretreated high-entropy alloy layer 301 with polyurethane 302 includes:

[0097] The first polyether polyol is prepolymerized with a polyisocyanate to obtain a prepolymer;

[0098] The second polyether polyol, N,N-dimethylformamide, chain extender, organosilicon surfactant and water are first mixed at 30-40°C to obtain a mixture.

[0099] The pretreated high-entropy alloy layer 301 is placed in a mold, and then the prepolymer and the mixture are mixed for a second time. The material after the second mixture is injected into the mold and the mold is closed. Foaming treatment is performed, and the composite material blank is obtained after demolding.

[0100] The composite material blank is subjected to demolding post-processing.

[0101] By adopting the above technical solution, after the prepolymer is mixed with the mixture formed by the second polyether polyol, N,N-dimethylformamide, chain extender, organosilicon surfactant and water, it is injected into the mold and the mold is closed, so that the material after the second mixture is foamed under closed conditions, which can ensure that the polyurethane 302 fills all the pores of the honeycomb structure and there is no polyurethane 302 overflow.

[0102] In some embodiments, the first polyether polyol and the second polyether polyol are polymeric polyols. For example, the first and second polyether polyols may be polyether polyol POP / 36-28. In this invention, the polyisocyanate is an aromatic polyisocyanate. Preferably, the polyisocyanate is a polymethylene polyphenyl polyisocyanate (e.g., PM-200). In this invention, the first and second polyether polyols may be of the same or different types. Preferably, the first and second polyether polyols are of the same type.

[0103] In some embodiments, the mass ratio of the first polyether polyol to the polyisocyanate is 1:1.2-1.8.

[0104] In some embodiments, the prepolymerization temperature is 70-80°C.

[0105] In this invention, there is no special limitation on the prepolymerization time, which can be adjusted by those skilled in the art according to the actual reaction conditions. For example, the prepolymerization reaction time is 2-3 hours.

[0106] In some embodiments, the content of the second polyether polyol is 45-55% by mass percentage of the mixture, the content of N,N-dimethylformamide is 15-20%, the content of the chain extender is 2-6%, the content of the organosilicon surfactant is 18-25%, and the balance is water.

[0107] When the amounts of the second polyether polyol, N,N-dimethylformamide, chain extender, organosilicon surfactant, and water meet the above-mentioned ranges, it is beneficial to ensure that the reaction system has suitable fluidity and reactivity, ensuring that the foam fully fills the honeycomb pores and forms a uniform and fine pore structure. Furthermore, the polyurethane 302 is more firmly bonded in the honeycomb structure of the high-entropy alloy layer 301, resulting in excellent sound insulation performance, strong impact resistance, and high compressive strength of the composite material.

[0108] In some embodiments, the chain extender is an alkanolamine chain extender and / or a small molecule diol chain extender. Preferably, the chain extender is triethanolamine and / or 1,4-butanediol.

[0109] In some embodiments, the silicone surfactant is a polyether-modified polysiloxane. For example, the silicone surfactant can be AK8805 surfactant.

[0110] In some embodiments, the mass ratio of the prepolymer to the mixture is 1:0.6-0.9.

[0111] By adopting the above technical solution, when the mass ratio of the prepolymer to the mixture meets the above range, the isocyanate index of the system can be precisely controlled within the range of 1 to 1.1, which is conducive to full reaction, avoids residual toxic monomer residue, and the degree of crosslinking is moderate, so that the elasticity and rigidity of polyurethane 302 are balanced, the dimensional stability is good, and it is beneficial to obtain composite pipes with strong impact resistance and high compressive strength.

[0112] In some embodiments, the second mixing includes stirring at 30-40°C for 10-15 seconds at a stirring rate of 1500-3000 rpm.

[0113] In some embodiments, the foaming process includes foaming at 75-95°C for 60-90 minutes.

[0114] Using the above technical solution, when the conditions of the second mixing and / or the foaming treatment meet the above range, the polyurethane 302 has a uniform and dense cell structure, which generates sufficient pressure on the high-entropy alloy layer 301 of the honeycomb structure, allowing the polyurethane 302 to fully impregnate and bond with the high-entropy alloy layer 301; thereby giving the composite pipe higher impact resistance and compressive strength. Preferably, the foaming treatment includes foaming at 80-90℃ for 65-85 minutes.

[0115] In some embodiments, the post-demolding treatment includes: removing the overflow and burrs from the composite material blank, and then curing it at a temperature of 75-85°C for 3.5-4.5 hours. According to a preferred embodiment of the present invention, the post-demolding treatment includes: removing the overflow and burrs from the composite material blank, preheating the oven temperature to 50-60°C, placing the composite material blank in the oven, raising the temperature to 75-85°C at a rate of 1-2°C / min, and then holding it at that temperature for 3.5-4.5 hours.

[0116] In some embodiments, the outer aluminum alloy layer 2 is spot-welded to the outer surface of the high-entropy alloy honeycomb core layer 3, wherein the spot welding connection is a resistance spot welding connection. According to a preferred embodiment of the present invention, the conditions for the spot welding connection include: a spot welding machine load of 33-55 kN, a spot welding machine gun feed time of 0.5-1.5 s, and a spot welding machine return time of 0.4-0.5 s; during spot welding, a fixed welding time of 350 ms-450 ms, an electrode pressure of 1.85-2.15 kN, a welding current of 3.5-5.5 kA, and the electrode used is a flat-headed electrode with a diameter of 5-10 mm.

[0117] In some embodiments, when the resin-impregnated carbon fiber is wound around the outer surface of the outer aluminum alloy layer 2 of the tube, the winding conditions include: a winding tension of 50-70N, a winding speed of 0.16-0.25m / s, and a circumferential winding angle of 85°-90°.

[0118] In some embodiments, after the impregnated carbon fiber is wound around the outer surface of the outer aluminum alloy layer 2 of the tube, the conditions for the first curing treatment include: curing in a segmented temperature control manner, wherein the segmented temperature control manner is: heating to 95-105℃ and curing for 0.5-1.5h, then heating to 115-125℃ and curing for 1.5-2.5h, and then heating to 145-155℃ and curing for 3.5-4.5h, wherein the heating rate is 0.5-1℃ / min.

[0119] By adopting the above technical solution, when the winding conditions of the impregnated carbon fiber and / or the conditions of the first curing treatment meet the above range, the chemical reaction rate is moderate, avoiding the rapid escape of low-molecular-weight substances such as solvents in the adhesive solution and the formation of a large number of bubbles; at the same time, during the segmented temperature-controlled curing process, the temperature of each part of the impregnated carbon fiber can be kept consistent, avoiding inconsistent curing speed and degree of curing in different parts of the impregnated carbon fiber, avoiding uneven shrinkage, and the resulting internal stress causing deformation or cracking of the composite tube; therefore, when the first curing conditions and / or the winding conditions of the impregnated carbon fiber meet the above range, the carbon fiber winding layer 1 and the outer aluminum alloy layer 2 are more tightly bonded, and the carbon fiber winding layer 1 is more uniform and dense, thereby giving the composite tube better corrosion resistance and impact resistance. Preferably, after the impregnated carbon fiber is wound around the outer surface of the outer aluminum alloy layer 2 of the tube, the conditions for the first curing treatment include: curing in a segmented temperature control manner, wherein the segmented temperature control manner is: heating to 95-100℃ and curing for 0.5-1.5h, then heating to 120-125℃ and curing for 1.5-2.5h, and then heating to 150-155℃ and curing for 3.5-4.5h, wherein the heating rate is 0.5-0.8℃ / min.

[0120] In some embodiments, the method for preparing the adhesive liquid includes:

[0121] Component A is obtained by mixing 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether; wherein the mass ratio of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether is 1:0.8-0.9:1-2.

[0122] 4,4-Diaminoxylenemethane is mixed with an accelerator to obtain component B; wherein the mass ratio of 4,4-diaminoxylenemethane to the accelerator is 0.3-2.7:1;

[0123] After compounding component A and component B at a mass ratio of 1:0.3-0.4, the mixture is stirred and degassed to obtain an epoxy resin solution, which is the adhesive solution.

[0124] In the preparation method of the adhesive liquid, preferably, the mass ratio of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether is 1:0.85-0.9:1-2. Preferably, component A and component B are compounded at a mass ratio of 1:0.35-0.37.

[0125] In the preparation method of the adhesive liquid, the accelerator is selected from benzoyl peroxide (BPO) and / or 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30).

[0126] By adopting the above technical solution, when the above-mentioned accelerators are used, the curing speed of the epoxy resin adhesive can be increased, the bonding degree between the carbon fiber winding layer 1 and the outer aluminum alloy layer 2 can be improved, and the carbon fiber winding layer 1 can be made more uniform and dense, thereby giving the composite pipe better corrosion resistance and impact resistance.

[0127] A third aspect of the present invention provides an application of the above-mentioned composite tube in a deep-sea hydraulic actuator.

[0128] Compared with the prior art, the beneficial effects of the composite tube provided by the present invention in the application of deep-sea hydraulic actuators are the same as the beneficial effects of the composite tube described in the above technical solutions, and will not be repeated here.

[0129] To better illustrate the technical solution of the present invention, the following specific embodiments are also provided.

[0130] In the embodiments and comparative examples of this invention:

[0131] Aluminum alloy: 6061-T6 aluminum alloy, purchased from Shanghai Jingteng Metal Group Co., Ltd.; by weight percentage of aluminum alloy, it contains 0.6% silicon, 0.5% iron, 0.25% copper, 0.1% manganese, 1% magnesium, 0.2% chromium, 0.1% zinc, 0.1% titanium and 97.15% aluminum.

[0132] High-entropy alloy: CoCrFeNiMn high-entropy alloy, purchased from Beijing Yanbang New Material Technology Co., Ltd.; based on the mass percentage of the high-entropy alloy, the content of Co is 21%, the content of Cr is 19%, the content of Fe is 20%, the content of Ni is 21%, and the content of Mn is 19%.

[0133] Carbon fiber: T700 grade carbon fiber, purchased from Zhongfu Shenying Carbon Fiber Co., Ltd., grade SYT49S-12K; tensile strength is 4.9GPa.

[0134] Unless otherwise specified in the examples and comparative examples, all raw materials were obtained commercially.

[0135] Example 1

[0136] A composite tube, comprising, from the outside to the inside: a carbon fiber winding layer 1, an outer aluminum alloy layer 2, a high-entropy alloy honeycomb core layer 3, and an inner aluminum alloy layer 4. The carbon fiber winding layer 1 comprises T700 grade carbon fiber and epoxy resin, with a density of 1.6 g / cm³, a thickness of 5 mm, an adhesive content of 28 wt%, and a carbon fiber content of 72 wt%. Both the outer aluminum alloy layer 2 and the inner aluminum alloy layer 4 are made of 6061-T6 aluminum alloy and have a thickness of 3 mm. The high-entropy alloy honeycomb core layer 3 comprises a high-entropy alloy layer 301 forming a honeycomb structure and polyurethane 302 filling the honeycomb structure. The high-entropy alloy is a CoCrFeNiMn high-entropy alloy, the hexagonal honeycomb structure has a side length of 2.25 mm, a foil thickness of 0.1 mm, and is filled with polyurethane 302 foam material with a density of 250 kg / m³. The high-entropy alloy honeycomb core layer 3 has a thickness of 2 mm. The inner diameter of the composite tube is 94 mm.

[0137] The preparation method of the above-mentioned composite tube includes the following steps:

[0138] Preparation of inner aluminum alloy layer 4 and high-entropy alloy layer 301: After the inner aluminum alloy layer 4 was made into a tubular shape, a three-dimensional model of the regular hexagonal honeycomb structure of Example 1 was designed using CAD software and imported into slicing software to generate the laser cladding path. The high-entropy alloy powder was dried in a vacuum drying oven at 120℃ for 2.5 hours, and the average diameter of the spherical particles of the high-entropy alloy powder was 30μm. The laser power was set to 3000W, the scanning speed to 50m / min, the laser energy density to 1.8J / mm², the powder feeding rate to 17g / min, and the spot diameter to 3.5mm. Argon was used as the protective gas and the powder feeding gas. Laser cladding was performed on the outer surface of the rotating inner aluminum alloy layer 4, and the linear velocity was controlled at 50m / min. The high-entropy alloy layer 301 of the honeycomb structure was formed by layer-by-layer offset. After cladding, the layers were air-cooled to room temperature to obtain a composite structure of high-entropy alloy layer 301 of the honeycomb structure and inner aluminum alloy layer 4.

[0139] Pretreatment of high-entropy alloy layer 301: The above composite structure was immersed in acetone and cleaned for 18 minutes in an ultrasonic cleaner at 120W power and 25℃. After removal, it was rinsed with fresh acetone and dried at 80℃ for 15 minutes. Using 15wt% sulfuric acid solution as electrolyte and controlling the temperature at 20℃, high-entropy alloy layer 301 was used as the anode and stainless steel plate as the cathode. DC voltage was applied for oxidation for 35 minutes. After oxidation, it was thoroughly rinsed with deionized water. Silane coupling agent was added to ethanol and pre-hydrolyzed for 40 minutes. Then, high-entropy alloy layer 301 was immersed in 1.5wt% γ-aminopropyltriethoxysilane ethanol solution (the pH of the silane coupling agent solution was adjusted to 5 with acetic acid) for 3 minutes. After removal, it was cured in an oven at 110℃ for 25 minutes.

[0140] Preparation of prepolymer and mixture: A prepolymer was obtained by prepolymerizing a first polyether polyol POP / 36-28 with a polyisocyanate PM-200 (75°C, 2.5h); wherein the mass ratio of the first polyether polyol to the polyisocyanate was 1:1.3. A first mixture was then prepared by mixing a second polyether polyol POP / 36-28, N,N-dimethylformamide, a chain extender (triethanolamine), a silicone surfactant (AK8805), and water at 35°C; wherein, by mass percentage, the second polyether polyol comprised 50%, the N,N-dimethylformamide comprised 17%, the chain extender comprised 4%, the silicone surfactant comprised 21%, and the remainder was water.

[0141] Polyurethane 302 filling: The above prepolymer and mixture are stirred at 35°C and 2000 rpm for 12 seconds to mix evenly, and then quickly injected into a mold with the high-entropy alloy layer 301 placed on it. After mold closing, it is foamed in an oven at 85°C for 75 minutes. After demolding, it is trimmed by a CNC milling machine to remove overflow and burrs. After preheating the oven temperature to 55°C, the composite material blank is placed in the oven and heated to 80°C at a rate of 1.5°C / min, and then kept at that temperature for 4 hours.

[0142] Spot welding connection: The outer aluminum alloy layer 2 and the high-entropy alloy honeycomb core layer 3 are overlapped and assembled using a DM-200 spot welding machine. The load of the spot welding machine is 45kN, the gun advance time is 1s, and the return time is 0.4s. During spot welding, the fixed welding time is 400ms, the electrode pressure is 2kN, the welding current is 4.5kA, and the electrode used is a flat-head electrode with a diameter of 5mm. After welding, the weld points are ground, cleaned with acetone, and air-dried to obtain a tube containing the outer aluminum alloy layer 2, the high-entropy alloy honeycomb core layer 3, and the inner aluminum alloy layer 4.

[0143] Adhesive preparation: Component A is obtained by mixing 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether; wherein the mass ratio of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether is 1:0.85:1.5; Component B is obtained by mixing 4,4-diaminoxylmethylmethane with accelerator 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30); wherein the mass ratio of 4,4-diaminoxylmethylmethane to accelerator is 1.5:1; Component A and Component B are compounded at a mass ratio of 1:0.36, stirred, and degassed to obtain an epoxy resin solution, i.e., the adhesive solution.

[0144] Preparation of carbon fiber winding layer 1: After impregnating carbon fiber with adhesive solution in an impregnation tank, impregnated carbon fiber is obtained. The impregnated carbon fiber is wound around the outer surface of the outer aluminum alloy layer 2 of the tube using a circumferential winding machine. The main process parameters are set as follows: winding tension 60N, roller gap 0.1mm, winding speed 0.2m / s, and circumferential winding angle 88°.

[0145] Curing of carbon fiber winding layer 1: Curing was carried out using a segmented temperature control method, with the temperature increased to 100℃ at a rate of 0.8℃ / min and held for 1 hour, then increased to 120℃ and held for 2 hours, and finally increased to 150℃ and held for 4 hours. After curing, the sample was cooled to room temperature in the furnace to obtain the composite tube.

[0146] A hydraulic burst test was conducted on the composite pipe: The test was performed according to GB / T 15560-1995, "Hydraulic Instantaneous Burst Test Method for Plastic Pipes for Fluid Transportation." A sample of a specified length of composite pipe was taken, and both ends were sealed to ensure that the sealed area did not fail before the middle of the pipe. The sample was filled with water and all air was expelled, and then installed in the hydraulic burst test system. At room temperature, water pressure was applied to the pipe at a constant rate (2 MPa / s) until the sample burst, leaked, or the pressure dropped significantly. The instantaneous highest pressure value measured by the pressure sensor was recorded as the burst pressure of the composite pipe. The test showed that the burst pressure of the composite pipe in Example 1 reached 210 MPa.

[0147] Axial compressive strength testing was performed on the composite tube, referring to GB / T 7314-2017 Metallic Materials - Compression Test at Room Temperature. The composite tube from Example 1 was processed into short cylindrical specimens of a specified length (length-to-diameter ratio of 2 to avoid buckling as the dominant failure mode). Both ends of the specimens were required to be parallel and smooth. On a universal testing machine, a polytetrafluoroethylene film or lubricant was placed between the specimen and the indenter to reduce end friction constraints. Displacement control mode was used, with loading at a constant rate (1 mm / min), and the load-displacement curves were continuously recorded. The axial compressive strength of the composite tube from Example 1 was tested to be 275 MPa.

[0148] The circumferential tensile strength of the composite tube was tested using the split-plate method, referring to GB / T 5352-2005, "Test Method for External Load Performance of Fiber Reinforced Thermosetting Plastic Pipes with Parallel Plates". The composite tube from Example 1 was processed into smooth circular specimens with a width of 25 mm. The specimens were clamped using a special fixture (split plate) and mounted on a universal testing machine. A tensile load was applied at a constant beam displacement rate (e.g., 5 mm / min), subjecting the specimen to circumferential tension until failure. The circumferential tensile strength of the composite tube from Example 1 was tested to be 557 MPa.

[0149] Example 2

[0150] The composite tube of Example 2 differs from that of Example 1 in that: the thickness of the carbon fiber winding layer 1 is 4 mm, the adhesive content is 26%, the thickness of the high-entropy alloy honeycomb core layer 3 is 3 mm, the inner diameter of the composite tube is 95 mm, and the polyurethane 302 filling density is 245 kg / m³. Other parameters of the composite tube are the same as in Example 1.

[0151] The preparation method of the above-mentioned composite tube includes the following steps:

[0152] Preparation of inner aluminum alloy layer 4 and high-entropy alloy layer 301: After the inner aluminum alloy layer 4 is made into a tubular shape, a three-dimensional model of the regular hexagonal honeycomb structure of Example 2 is designed using CAD software, and imported into slicing software to generate the laser cladding path. The drying conditions of the high-entropy alloy powder and the processing conditions of the laser cladding technology are the same as those in Example 1.

[0153] The pretreatment, prepolymer and mixture preparation of the high-entropy alloy layer 301 are the same as in Example 1.

[0154] Polyurethane 302 filling: The above prepolymer and mixture are stirred at 35°C and 2000 rpm for 12 seconds to mix evenly, and then quickly injected into a mold with the high-entropy alloy layer 301 placed on it. After mold closing, it is foamed in an oven at 85°C for 75 minutes. After demolding, it is trimmed by a CNC milling machine to remove overflow and burrs. After preheating the oven temperature to 55°C, the composite material blank is placed in the oven and heated to 80°C at a rate of 1.5°C / min, and then kept at that temperature for 4 hours.

[0155] The methods for spot welding, adhesive preparation, carbon fiber winding layer 1 preparation, and carbon fiber winding layer 1 curing are the same as in Example 1.

[0156] The composite pipe was tested according to the water pressure burst test method in Example 1, as well as the test methods for axial compressive strength and circumferential tensile strength. The burst pressure of the composite pipe in Example 2 was 199 MPa, the axial compressive strength was 265 MPa, and the circumferential tensile strength was 540 MPa, showing excellent comprehensive mechanical properties and adaptability to the deep-sea environment.

[0157] Example 3

[0158] A composite tube, comprising, from the outside to the inside: a carbon fiber winding layer 1, an outer aluminum alloy layer 2, a high-entropy alloy honeycomb core layer 3, and an inner aluminum alloy layer 4. The carbon fiber winding layer 1 comprises T700 grade carbon fiber and epoxy resin, with a density of 1.65 g / cm³, a thickness of 6 mm, an adhesive content of 34 wt%, and a carbon fiber content of 66 wt%. Both the outer aluminum alloy layer 2 and the inner aluminum alloy layer 4 are made of 6061-T6 aluminum alloy and have a thickness of 3 mm. The high-entropy alloy honeycomb core layer 3 comprises a high-entropy alloy layer 301 forming a honeycomb structure and polyurethane 302 filling the honeycomb structure. The high-entropy alloy is a CoCrFeNiMn high-entropy alloy, the hexagonal honeycomb structure has a side length of 2.35 mm, a foil thickness of 0.1 mm, and is filled with polyurethane 302 foam material with a density of 250 kg / m³. The high-entropy alloy honeycomb core layer 3 has a thickness of 6 mm. The inner diameter of the composite tube is 97 mm.

[0159] The preparation method of the above-mentioned composite tube includes the following steps:

[0160] Preparation of inner aluminum alloy layer 4 and high-entropy alloy layer 301: After the inner aluminum alloy layer 4 is formed into a tubular shape, a three-dimensional model of the regular hexagonal honeycomb structure of Example 3 is designed using CAD software, and imported into slicing software to generate the laser cladding path. The drying conditions of the high-entropy alloy powder and the processing conditions of the laser cladding technology are the same as in Example 1.

[0161] The pretreatment of the high-entropy alloy layer 301, the preparation of the prepolymer and mixture, the filling of polyurethane 302, the spot welding connection, and the preparation of the adhesive are the same as in Example 1.

[0162] Preparation of carbon fiber winding layer 1: After impregnating carbon fiber with adhesive solution in an impregnation tank, impregnated carbon fiber is obtained. The impregnated carbon fiber is wound around the outer surface of the outer aluminum alloy layer 2 of the tube using a circumferential winding machine. The main process parameters are set as follows: winding tension 60N, roller gap 0.1mm, winding speed 0.2m / s, and circumferential winding angle 87°.

[0163] Curing of carbon fiber winding layer 1: Curing was carried out using a segmented temperature control method. The temperature was increased to 95℃ at a rate of 0.5℃ / min and held for 1 hour, then increased to 125℃ and held for 1.5 hours, and finally increased to 155℃ and held for 3.5 hours. After curing, the sample was cooled to room temperature in the furnace to obtain the composite tube.

[0164] The composite pipe was tested according to the water pressure burst test method in Example 1, as well as the test methods for axial compressive strength and circumferential tensile strength. The burst pressure of the composite pipe in Example 3 was 225 MPa, the axial compressive strength was 285 MPa, and the circumferential tensile strength was 570 MPa, showing excellent comprehensive mechanical properties and adaptability to the deep-sea environment.

[0165] Example 4

[0166] A composite tube, comprising, from the outside to the inside: a carbon fiber winding layer 1, an outer aluminum alloy layer 2, a high-entropy alloy honeycomb core layer 3, and an inner aluminum alloy layer 4. The carbon fiber winding layer 1 comprises T700 grade carbon fiber and epoxy resin, with a density of 1.6 g / cm³, a thickness of 4 mm, and an adhesive content of 24%. Both the outer aluminum alloy layer 2 and the inner aluminum alloy layer 4 are made of 6061-T6 aluminum alloy and have a thickness of 4 mm. The high-entropy alloy honeycomb core layer 3 comprises a high-entropy alloy layer 301 forming a honeycomb structure and polyurethane 302 filling the honeycomb structure. The high-entropy alloy is a CoCrFeNiMn high-entropy alloy, the hexagonal honeycomb structure has a side length of 2.55 mm, a foil thickness of 0.14 mm, and is filled with polyurethane 302 foam material with a density of 245 kg / m³. The high-entropy alloy honeycomb core layer 3 has a thickness of 3 mm. The inner diameter of the composite tube is 94 mm.

[0167] The preparation method of the above-mentioned composite tube includes the following steps:

[0168] Preparation of inner aluminum alloy layer 4 and high-entropy alloy layer 301: After the inner aluminum alloy layer 4 was made into a tubular shape, a three-dimensional model of the regular hexagonal honeycomb structure of Example 4 was designed using CAD software and imported into slicing software to generate the laser cladding path. The high-entropy alloy powder was dried in a vacuum drying oven at 120℃ for 2.5 hours, and the average diameter of the spherical particles of the high-entropy alloy powder was 50μm. The laser power was set to 3100W, the scanning speed to 50m / min, the laser energy density to 1.8J / mm², the powder feeding rate to 17g / min, and the spot diameter to 3mm. Argon was used as the protective gas and the powder feeding gas. Laser cladding was performed on the outer surface of the rotating inner aluminum alloy layer 4, and the linear velocity was controlled at 48m / min. The high-entropy alloy layer 301 of the honeycomb structure was formed by layer-by-layer offset. After cladding, the layers were air-cooled to room temperature to obtain a composite structure of high-entropy alloy layer 301 of the honeycomb structure and inner aluminum alloy layer 4.

[0169] Pretreatment of high-entropy alloy layer 301: The composite structure was immersed in acetone and cleaned for 15 minutes at 30°C and 150W in an ultrasonic cleaner. After removal, it was rinsed with fresh acetone and dried at 80°C for 15 minutes. Using 20wt% sulfuric acid solution as electrolyte and controlling the temperature at 20°C, high-entropy alloy layer 301 was used as the anode and stainless steel plate as the cathode. DC voltage was applied for oxidation for 30 minutes. After oxidation, it was thoroughly rinsed with deionized water. Silane coupling agent was added to ethanol and pre-hydrolyzed for 40 minutes. Then, high-entropy alloy layer 301 was immersed in 1wt% γ-aminopropyltriethoxysilane ethanol solution (the pH of the silane coupling agent solution was adjusted to 5.5 with acetic acid) for 3 minutes. After removal, it was cured in an oven at 100°C for 30 minutes.

[0170] The preparation of the prepolymer and mixture is the same as in Example 1.

[0171] Polyurethane 302 filling: The above prepolymer and mixture are stirred at 35°C and 2000 rpm for 12 seconds to mix evenly, and then quickly injected into a mold with the high-entropy alloy layer 301 placed on it. After mold closing, it is foamed in an oven at 90°C for 80 minutes. After demolding, it is trimmed by a CNC milling machine to remove overflow and burrs. After preheating the oven temperature to 55°C, the composite material blank is placed in the oven and heated to 85°C at a rate of 1°C / min, and then kept at that temperature for 3.5 hours.

[0172] The spot welding connection, adhesive preparation, carbon fiber winding layer 1 preparation, and carbon fiber winding layer 1 curing are the same as in Example 1.

[0173] The composite pipe was tested according to the water pressure burst test method in Example 1, as well as the test methods for axial compressive strength and circumferential tensile strength. The burst pressure of the composite pipe in Example 4 was 195 MPa, the axial compressive strength was 260 MPa, and the circumferential tensile strength was 535 MPa, demonstrating excellent comprehensive mechanical properties and adaptability to the deep-sea environment.

[0174] Example 5

[0175] A composite tube, comprising, from the outside to the inside: a carbon fiber winding layer 1, an outer aluminum alloy layer 2, a high-entropy alloy honeycomb core layer 3, and an inner aluminum alloy layer 4. The carbon fiber winding layer 1 comprises T700 grade carbon fiber and epoxy resin, with a density of 1.6 g / cm³, a thickness of 5 mm, and an adhesive content of 28%. Both the outer aluminum alloy layer 2 and the inner aluminum alloy layer 4 are made of 6061-T6 aluminum alloy and have a thickness of 4 mm. The high-entropy alloy honeycomb core layer 3 comprises a high-entropy alloy layer 301 forming a honeycomb structure and polyurethane 302 filling the honeycomb structure. The high-entropy alloy is a CoCrFeNiMn high-entropy alloy, the hexagonal honeycomb structure has a side length of 2.75 mm, a foil thickness of 0.1 mm, and is filled with polyurethane 302 foam material with a density of 250 kg / m³. The high-entropy alloy honeycomb core layer 3 has a thickness of 4 mm. The inner diameter of the composite tube is 95 mm.

[0176] The preparation method of the above-mentioned composite tube includes the following steps:

[0177] The preparation of the inner aluminum alloy layer 4 and the high-entropy alloy layer 301, and the pretreatment of the high-entropy alloy layer 301 are the same as in Example 1;

[0178] Preparation of prepolymer and mixture: A first polyether polyol POP / 36-28 and polyisocyanate PM-200 were prepolymerized (80°C, 2h) to obtain a prepolymer; wherein the mass ratio of the first polyether polyol to the polyisocyanate was 1:1.2. A second polyether polyol POP / 36-28, N,N-dimethylformamide, a chain extender (triethanolamine), a silicone surfactant (AK8805), and water were mixed at 35°C to obtain a mixture; wherein, by mass percentage, the second polyether polyol content was 45%, the N,N-dimethylformamide content was 20%, the chain extender content was 2%, the silicone surfactant content was 25%, and the remainder was water.

[0179] The steps for filling with polyurethane 302 and spot welding are the same as in Example 1.

[0180] Adhesive preparation: Component A is obtained by mixing 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether; wherein the mass ratio of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether is 1:0.9:2; Component B is obtained by mixing 4,4-diaminoxylmethane with the accelerator benzoyl peroxide (BPO); wherein the mass ratio of 4,4-diaminoxylmethane to the accelerator is 1:1; Component A and Component B are compounded at a mass ratio of 1:0.3, stirred, and degassed to obtain an epoxy resin solution, i.e., the adhesive solution.

[0181] The preparation and curing of carbon fiber winding layer 1 are the same as in Example 1.

[0182] The composite pipe was tested according to the water pressure burst test method in Example 1, as well as the test methods for axial compressive strength and circumferential tensile strength. The burst pressure of the composite pipe in Example 5 was 205 MPa, the axial compressive strength was 270 MPa, and the circumferential tensile strength was 550 MPa, showing excellent comprehensive mechanical properties and adaptability to the deep-sea environment.

[0183] Comparative Example 1

[0184] In Comparative Example 1, the difference from Example 1 is that the high-entropy alloy honeycomb core layer 3 of the composite tube in Comparative Example 1 is not filled with polyurethane 302.

[0185] The preparation method of the composite tube in Comparative Example 1 is as follows: Based on the adjustment of the composite tube structure, the preparation method of the composite tube in Example 1 is adapted, specifically by reducing the preparation steps of prepolymer and mixture and polyurethane 302 filling, thus forming the preparation method of the composite tube in Comparative Example 1.

[0186] The composite pipe was tested according to the water pressure burst test method in Example 1, as well as the test methods for axial compressive strength and circumferential tensile strength. The burst pressure of the composite pipe in Comparative Example 1 was 175 MPa, the axial compressive strength was 220 MPa, and the circumferential tensile strength was 510 MPa.

[0187] Comparative Example 2

[0188] In Comparative Example 2, the difference from Example 1 is that the outer aluminum alloy layer 2 of the composite tube in Example 1 is replaced with an outer chromium nickel molybdenum stainless steel layer (316L stainless steel).

[0189] The preparation method of the composite tube in Comparative Example 2 is the same as that in Example 1, except that in the spot welding connection step in Example 1, the outer chromium nickel molybdenum stainless steel layer and the high entropy alloy honeycomb core layer 3 are overlapped and assembled. The assembly method and parameters are the same as those in Example 1.

[0190] The composite pipe was tested according to the water pressure burst test method in Example 1, as well as the test methods for axial compressive strength and circumferential tensile strength. The burst pressure of the composite pipe in Comparative Example 2 was 185 MPa, the axial compressive strength was 245 MPa, and the circumferential tensile strength was 510 MPa.

[0191] Comparative Example 3

[0192] In Comparative Example 3, the difference from Example 1 is that the inner aluminum alloy layer 4 of the composite tube in Example 1 is replaced with an inner chromium-nickel-molybdenum stainless steel layer (316L stainless steel).

[0193] The preparation method of the composite tube in Comparative Example 3 is the same as that in Example 1, except that in the preparation steps of the inner aluminum alloy layer 4 and the high entropy alloy layer 301 in Example 1, the inner chromium nickel molybdenum stainless steel layer is made into a tube shape, and then the high entropy alloy layer 301 is prepared on the outer surface of the inner chromium nickel molybdenum stainless steel layer. The preparation method and parameters of the high entropy alloy layer 301 are the same as those in Example 1.

[0194] The composite pipe was tested according to the water pressure burst test method in Example 1, as well as the test methods for axial compressive strength and circumferential tensile strength. The burst pressure of the composite pipe in Comparative Example 3 was 180 MPa, the axial compressive strength was 240 MPa, and the circumferential tensile strength was 505 MPa.

[0195] Comparative Example 4

[0196] In Comparative Example 4, the difference from Example 1 is that the composite tube of Comparative Example 4 does not contain the carbon fiber winding layer 1.

[0197] The preparation method of the composite tube in Comparative Example 4 is as follows: The preparation method of the composite tube in Example 1 is adapted to the composite tube structure. Specifically, the adhesive preparation step, the carbon fiber winding layer 1 preparation step, and the carbon fiber winding layer 1 curing step are reduced during preparation.

[0198] The composite pipe was tested according to the water pressure burst test method in Example 1, as well as the test methods for axial compressive strength and circumferential tensile strength. The burst pressure of the composite pipe in Comparative Example 4 was 120 MPa, the axial compressive strength was 180 MPa, and the circumferential tensile strength was 300 MPa.

[0199] Comparative Example 5

[0200] In Comparative Example 5, the difference from Example 1 is that the composite tube of Comparative Example 5 does not contain the outer aluminum alloy layer 2.

[0201] The preparation method of the composite tube in Comparative Example 5 is as follows: The preparation method of the composite tube in Example 1 is adapted to the composite tube structure, specifically by reducing the spot welding connection steps during preparation.

[0202] The composite pipe was tested according to the water pressure burst test method in Example 1, as well as the test methods for axial compressive strength and circumferential tensile strength. The burst pressure of the composite pipe in Comparative Example 5 was 185 MPa, the axial compressive strength was 240 MPa, and the circumferential tensile strength was 520 MPa.

[0203] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method of making a composite pipe, characterized by, The composite tube comprises, from the outside to the inside, a carbon fiber winding layer, an outer aluminum alloy layer, a high-entropy alloy honeycomb core layer, and an inner aluminum alloy layer; wherein, the high-entropy alloy honeycomb core layer comprises a high-entropy alloy layer forming a honeycomb structure, and polyurethane filled in the honeycomb structure. The preparation method includes: After the inner aluminum alloy layer is made into a tubular shape, laser cladding technology is used to form a honeycomb structure of high entropy alloy powder on the outer surface of the inner aluminum alloy layer. The high-entropy alloy layer is pretreated, wherein the pretreatment includes anodizing and coupling agent treatment; Polyurethane is filled into the pretreated high-entropy alloy layer to obtain a semi-finished pipe containing a high-entropy alloy honeycomb core layer and an inner aluminum alloy layer. The outer aluminum alloy layer is spot-welded to the outer surface of the high-entropy alloy honeycomb core layer to obtain a tube containing an outer aluminum alloy layer, a high-entropy alloy honeycomb core layer and an inner aluminum alloy layer. After carbon fiber is brought into contact with adhesive liquid, impregnated carbon fiber is obtained. The impregnated carbon fiber is then wound around the outer surface of the outer aluminum alloy layer of the tube and subjected to a first curing treatment to obtain the composite tube. The anodizing process includes: oxidizing the high-entropy alloy layer as the anode, using a 15-20wt% sulfuric acid aqueous solution as the electrolyte, the temperature of the electrolyte being 18-22℃, and the oxidation time being 30-40min; The coupling agent treatment includes: adding a silane coupling agent to ethanol and / or propanol for pre-hydrolysis to obtain a silane coupling agent solution; immersing the anodized high-entropy alloy layer in the silane coupling agent solution; adjusting the pH of the silane coupling agent solution to 4.5-5.5 using an organic acid; removing the layer after immersion for 2-5 minutes; and performing a second curing treatment at 100-120°C. The process of filling the pretreated high-entropy alloy layer with polyurethane includes: The first polyether polyol is prepolymerized with a polyisocyanate to obtain a prepolymer; The second polyether polyol, N,N-dimethylformamide, chain extender, organosilicon surfactant and water are first mixed at 30-40°C to obtain a mixture. The pretreated high-entropy alloy layer is placed in a mold, and then the prepolymer and the mixture are mixed for a second time. The material after the second mixture is injected into the mold and the mold is closed. Foaming treatment is performed, and the composite material blank is obtained after demolding. The composite material blank is subjected to demolding post-processing.

2. The method of producing a composite pipe according to claim 1, characterized by, The carbon fiber winding layer comprises carbon fiber and adhesive; wherein, by weight percentage, the carbon fiber winding layer comprises 66%-76% carbon fiber and 24%-34% adhesive; and / or, Based on the mass percentage of the outer aluminum alloy layer or the inner aluminum alloy layer, each of the outer aluminum alloy layer and the inner aluminum alloy layer independently contains 0.4%-0.8% silicon, 0.01%-0.7% iron, 0.1%-0.4% copper, 0.01%-0.5% manganese, 0.8%-1.2% magnesium, 0.05%-0.35% chromium, 0.01%-0.5% zinc, 0.01%-0.15% titanium, with the balance being aluminum.

3. The method of producing a composite pipe according to claim 1 or 2, characterized by, The high-entropy alloy layer comprises Co, Cr, Fe, Ni and Mn; wherein, by mass percentage, the content of Co is 19%-23%, the content of Cr is 16%-21%, the content of Fe is 18%-22%, the content of Ni is 19%-23%, and the content of Mn is 16%-21%.

4. The preparation method according to claim 1, characterized in that, The processing conditions for the laser cladding technology include: a high-entropy alloy powder feeding rate of 16-18 g / min, a laser power of 2500-3500 W, a laser scanning speed of 40-55 m / min, and a laser energy density of 1.7-1.9 J / mm². 2 The high-entropy alloy powder has an average diameter of 20-50 μm, the laser spot diameter is 3-4 mm, and the surface linear velocity of the inner aluminum alloy layer along the axial direction is 45-55 m / min.

5. The preparation method according to claim 1, characterized in that, The silane coupling agent is selected from γ-aminopropyltriethoxysilane and / or γ-glycidoxypropyltrimethoxysilane; The concentration of the silane coupling agent solution is 1-2 wt%.

6. The method of claim 1, wherein, The prepolymerization temperature is 70-80℃; and / or, The mass ratio of the first polyether polyol to the polyisocyanate is 1:1.2-1.8; and / or, Based on the mass percentage of the mixture, the content of the second polyether polyol is 45-55%, the content of N,N-dimethylformamide is 15-20%, the content of the chain extender is 2-6%, the content of the organosilicon surfactant is 18-25%, and the balance is water; and / or, The mass ratio of the prepolymer to the mixture is 1:0.6-0.9; and / or, The second mixing includes: stirring at 30-40°C for 10-15 seconds at a stirring speed of 1500-3000 rpm; and / or, The foaming process includes foaming at 75-95℃ for 60-90 minutes.

7. The preparation method according to claim 1, characterized in that, The method for preparing the adhesive liquid includes: Component A is obtained by mixing 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether; wherein the mass ratio of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester resin, bisphenol F type epoxy resin, and n-butanol glycidyl ether is 1:0.8-0.9:1-2. 4,4-Diaminoxylenemethane is mixed with an accelerator to obtain component B; wherein the mass ratio of 4,4-diaminoxylenemethane to the accelerator is 0.3-2.7:1; After compounding component A and component B at a mass ratio of 1:0.3-0.4, the mixture is stirred and degassed to obtain an epoxy resin solution, which is the adhesive solution.

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