A multi-dimensional stealth submarine bionic heterogeneous protective shell and a preparation method thereof

Abstract

The application discloses a multi-dimensional stealth submarine bionic heterogeneous protective shell and a preparation method thereof, and relates to the technical field of ships and ocean engineering. The submarine bionic heterogeneous protective shell is composed of a sandwich structure and a modified carbon nanotube film. The sandwich structure comprises a bionic Primitive multi-stage rotating core layer, a bionic Diamond multi-stage rotating core layer, a bionic octagonal spiral core layer, a bionic rhombic dodecahedron spiral core layer, a micro-perforated plate and a sound-absorbing lower plate. The design of the application combines the Bouligand structure and the acoustic structure principle of the scales of the osteoglossum bicolor, and innovatively constructs four kinds of bionic structures by referring to the unique configuration of the interlayer rotation and spiral rising in the microstructure of the scales of the osteoglossum bicolor. The four kinds of bionic structures not only effectively inhibit deformation and improve the overall structural stability, but also provide an innovative solution for realizing the integration of mechanical bearing and acoustic stealth functions of the submarine shell through force-acoustic coupling regulation.

Description

Technical Field

[0001] This invention relates to the field of shipbuilding and marine engineering technology, specifically to a multi-dimensional stealth biomimetic heterogeneous protective hull for submarines and its preparation method. Background Technology

[0002] As a core tool in the underwater arms race among major powers, submarines are receiving increasing strategic attention. With the rapid development of modern anti-submarine technology and the complexity of the battlefield environment, the requirements for submarine "stealth" performance are becoming increasingly stringent in order to prevent submarines from being detected by the enemy.

[0003] In terms of acoustic stealth, traditional submarines often add anechoic tiles to their hulls to absorb sound waves. However, this method suffers from significant deficiencies in the synergistic mechanical and acoustic performance. The anechoic tiles have limitations in mechanical compatibility with the hull substrate, are easily detached by water flow, and result in significant sound leakage, increasing the risk of sonar detection. This reflects the inherent defects in the synergistic design of mechanical load-bearing capacity and acoustic stealth.

[0004] In terms of electromagnetic stealth, existing technologies use low-magnetic alloy materials to manufacture submarine hulls or install degaussing coils to generate a reverse magnetic field through electric current to counteract the hull's natural magnetic field. However, commonly used low-magnetic steels cannot withstand the high pressure and density of the deep sea. If active degaussing is used, continuous power supply is required, which puts pressure on the battery life of conventional submarines, resulting in a prominent contradiction between performance and range.

[0005] In terms of optical stealth, because submarines often operate in the deep sea where seawater reduces light emission, current optical stealth technology remains secondary and lacks emphasis. However, with the continuous advancement of satellite technology, the performance of onboard optical sensors is constantly improving, enabling clear detection of subtle changes on the water surface caused by submarine underwater activities. Furthermore, with the development of naval forces worldwide, the threats faced by submarines are becoming increasingly diverse and complex, inevitably leading to near-shore operations. Therefore, to better cope with various unknown threats and maintain my country's leading position in military technology, the development of optical stealth technology is unavoidable.

[0006] In terms of impact resistance, submarine hulls often use a single material or a metal frame. While this meets the impact resistance requirements, it generally has a high thickness, making it an excellent conductor of sound and electromagnetic waves. This can easily affect the submarine's speed and makes it difficult to balance lightweight design with stealth requirements.

[0007] Furthermore, existing technologies employ a split design, separating the structural load-bearing function from the "stealth" performance. This not only increases manufacturing complexity but also limits the potential for multi-physics synergistic optimization, which runs counter to the requirements of modern submarines for lightweighting, stealth, and multi-mission adaptability.

[0008] Among the existing research proposals, none have yet been able to achieve integrated "acoustic-magnetic-optical" camouflage while meeting the requirements for lightweight and impact resistance. Developing an advanced submarine hull protection structure that combines multifunctional characteristics with lightweight and impact resistance has become a key technological bottleneck in the development of the next generation of deep-sea submarines.

[0009] Therefore, a submarine hull protection structure with integrated acoustic-magnetic-optical stealth and impact resistance is needed.

[0010] Therefore, a multi-dimensional stealth biomimetic heterogeneous protective hull for submarines and its preparation method are proposed to solve the above problems. Summary of the Invention

[0011] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a multi-dimensional stealth biomimetic heterogeneous protective hull for submarines, comprising the following steps:

[0012] Step 1: Establish the sandwich structure using 3D modeling software;

[0013] Step 2: Convert the sandwich structure designed in Step 1 into an STL format file and import it into the Magics software. Based on the selective laser melting technology, a sandwich structure made of TC4 titanium alloy is prepared.

[0014] Step 3: The preparation of ZnO, the functionalization treatment of MWCNTs and the preparation of ZnO@MWCNTs particles are completed in sequence. Then, the ZnO@MWCNTs particles are added to PDMS solution to complete the modification of ZnO@MWCNTs particles and obtain modified carbon nanotube solution.

[0015] Step 4: First, pre-treat the sandwich structure obtained in Step 2. After treatment, place the sandwich structure into a modified carbon nanotube solution and perform stepwise impregnation on the sandwich structure using the dip-coating method. After repeated drying and impregnation, the sandwich structure is covered with a gradient modified carbon nanotube film, thereby obtaining a biomimetic heterogeneous protective shell for submarines.

[0016] Preferably, the sandwich structure in step 1 includes a biomimetic multi-level rotating core layer, a biomimetic diamond multi-level rotating core layer, a biomimetic octagonal spiral core layer, a biomimetic rhombic dodecahedral spiral core layer, a micro-perforated plate, and a sound-absorbing lower plate. Multiple biomimetic multi-level rotating core layers, biomimetic diamond multi-level rotating core layers, biomimetic octagonal spiral core layers, and biomimetic rhombic dodecahedral spiral core layers are arranged between the micro-perforated plate and the sound-absorbing lower plate.

[0017] As a preferred design approach, the steps for the biomimetic Primitive multi-level rotating core layer are as follows:

[0018] First, in Matlab software, using implicit function formulas... Modeling is performed, in which , , These are the three-dimensional coordinates of the point, A. p B p and C p For biomimetic structures in , and The period in the three directions of the coordinate system;

[0019] After completing the modeling, import the STL file generated by the software into SolidWorks to construct a P-type cell structure with a size of a×a×a. Then, arrange the P-type cell structure along... Arrayed once along the axis, along Axial direction and The array is repeated four times along each axis to construct a P-shaped lattice structure;

[0020] Next, create rectangular sketches of size (4a+s) × (4a+s) at the coordinate centers of the front and right reference planes respectively. Then, extrude the sketches into a cross-shaped plate structure with a thickness of s. At this point, the space is divided into four regions by the cross-shaped plate structure. On one face of one of the regions, completely cut a circular hole with a diameter of r at a distance of d from the top edge and b from the side edge. Then, cut the circular hole along... Arrayed once along the axis with a spacing of l, and along... The axis is arrayed twice at a spacing of d. Then, a reference axis 1 is created at the intersection of the front reference plane and the right reference plane. The linear array command of the above-mentioned circular holes is rotated around the reference axis 1 with a total rotation angle of 360°. The array is then arrayed three times at equal intervals to complete the construction of the connecting plate.

[0021] Subsequently, a rectangular outline of size 2a×(4a+s) is drawn at the center of the right reference plane of the P-type lattice structure. The P-type -0° structure is obtained by cutting, and then three rotation commands are executed sequentially on the P-type lattice structure around... The shaft is subjected to axial rotation operations of 15°, 30° and 45° respectively, and cut in the same way to generate P-type -15° structure, P-type -30° structure and P-type -45° structure in sequence;

[0022] Then, import the P-type -0° structure, P-type -15° structure, P-type -30° structure, P-type -45° structure and connecting plate into the same part environment. By aligning the faces, make the structural surfaces of the P-type -0° structure, P-type -15° structure, P-type -30° structure and P-type -45° structure coincide with the corresponding faces of the four areas of the connecting plate, forming a structure with the top surface aligned with the top surface, the side surface aligned with the side surface, and the overall size of (4a+s)×(4a+s). Then merge them into a single entity to complete the establishment of the biomimetic Primitive multi-level cell.

[0023] Finally, the biomimetic Primitive multilevel cell units are respectively along... Axial direction, Axial direction and The array is repeated twice along each axis to create a biomimetic multi-level rotating core layer.

[0024] As a preferred design, the steps for the biomimetic Diamond multi-level rotating core layer are as follows:

[0025] First, model the model using implicit function formulas in Matlab software, as shown in the following formula:

[0026] ;

[0027] in, , , These are the three-dimensional coordinates of the point. , and For biomimetic structures in , and The period in the three directions of the coordinate system;

[0028] After completing the modeling, import the STL file generated by the software into SolidWorks to construct a D-type cell structure with dimensions of a×a×a. Then, arrange the D-type cell structure along... Arrayed once along the axis, along Axial direction and The array is repeated four times along each axis to construct a D-shaped lattice structure;

[0029] Then, construct the connecting plate on the front and right view reference planes;

[0030] Subsequently, a rectangular outline of size 2a×(4a+s) is drawn at the center of the right reference plane of the D-type lattice structure. The D-type -0° structure is obtained by cutting, and then three rotation commands are executed sequentially on the D-type lattice structure around... The shaft is subjected to axial rotation operations of 15°, 30° and 45° respectively, and cut in the same way to generate D-type -15° structure, D-type -30° structure and D-type -45° structure in sequence;

[0031] Then, import the D-type -0° structure, D-type -15° structure, D-type -30° structure, D-type -45° structure and connecting plate into the same part environment. By aligning the surfaces, make the structural surfaces of the D-type -0° structure, D-type -15° structure, D-type -30° structure, D-type -45° structure and connecting plate coincide with the corresponding surfaces of the four areas of the connecting plate, forming a structure with the top surface aligned with the top surface, the side surface aligned with the side surface, and the overall size of (4a+s)×(4a+s). Then merge them into a single entity to complete the establishment of the biomimetic Diamond multi-level cell.

[0032] Finally, the biomimetic Diamond multilevel cell units were arranged along... Axial direction, Axial direction and The array is repeated twice along each axis to create a biomimetic diamond multi-level rotating core layer.

[0033] As a preferred design, the steps for the biomimetic octagonal spiral core layer are as follows:

[0034] First, draw a c×c×c cube using a 3D sketch. The center of the sketch should be at the intersection of the right view reference plane and the top view reference plane.

[0035] Create vertex spheres with diameter R at the vertex positions of the cube sketch, and face-centered spheres with diameter R at the center positions of the cube faces. Then, establish lines between the centers of each face-centered sphere, and use these lines as paths to scan with a circular outline of diameter h to generate the corresponding cylinders, thereby constructing an octagonal sphere structure.

[0036] Select a face-centered sphere in the octagonal sphere structure. Using the horizontal line 1 passing through the center of the face-centered sphere as a reference, the horizontal line 1 is parallel to the top reference plane and perpendicular to the right reference plane. Create a reference plane 1 at a position 45° away from it and at a distance of e. The reference plane 1 is perpendicular to the line connecting the centers of the vertex sphere and the face-centered sphere.

[0037] Then, draw a circular sketch with a diameter of g at the center of the reference plane 1. Based on this, generate two different helices. The height of both helices is set to f, the number of turns is set to 1, and the starting angles are set to 0° and 180° respectively.

[0038] Then, using a circle with diameter i as the scanning outline, the scanning operation is performed along the two spiral lines mentioned above to form a solid. Next, reference axis 2 and reference axis 3 are created in the right view reference plane and the top view reference plane respectively. Both of them pass through the center of the octagonal sphere structure. Reference axis 2 is perpendicular to the top view reference plane, and reference axis 3 is perpendicular to the right view reference plane. Then, the scanning command is mirrored once each with the right view reference plane and the top view reference plane as mirror planes. Finally, two rotation array operations are performed. First, the mirror command is rotated three times around reference axis 2 at equal intervals, and then rotated three times around reference axis 3 at equal intervals, with a total angle of 360°, to complete the creation of the octagonal sphere of revolution.

[0039] Subsequently, the solid is cut along the spiral path and the line path connecting the face-centered spheres using a scanning cut method. The cutting contour used for both types of paths is circular. The diameter of the circular contour corresponding to the line connecting the face-centered spheres is r1, and the diameter of the scanning circular contour corresponding to the spiral is r1 / 2. This completes the solid cut. Referring to the steps of creating a rotation array of octagonal revolves, a rotation array is executed on the scanning cut structure at the spiral to cut all the spirals. Then, a sphere with a diameter of r2 is cut off at the center position of each sphere.

[0040] Subsequently, the octagonal rotor that had undergone the excision operation was processed by stretch excision to cut it into biomimetic octagonal spiral cell units with a size of (4a+s)×(4a+s), and the parameters satisfy the following: ;

[0041] Finally, along... Axial direction, Axial direction and The array is repeated twice along each axis to create a biomimetic octagonal spiral core layer.

[0042] As a preferred design, the steps for the biomimetic rhombic dodecahedral spiral core layer are as follows:

[0043] First, using the intersection of the right view reference plane and the top view reference plane as the sketch center, draw a cube of size c×c×c using 3D sketching;

[0044] Then, rotate the cube sketch to generate a central sphere with a diameter of R at the center of the cube sketch, and rotate the cube sketch to generate edge spheres with a diameter of R at the center of each edge. Then connect the centers of the central sphere and the edge spheres, use the sweep command with a circular outline diameter of h to generate the corresponding cylinder, and then execute the combine command to merge all the entities into a rhombus sphere.

[0045] Select a sphere with a sideline in the rhombus sphere. Using the horizontal line 2 passing through the center of the sphere as a reference, the horizontal line 2 is parallel to the upper reference plane and perpendicular to the right reference plane. Create a reference plane 2 at a distance e, which is 45° away from the reference plane. The reference plane 2 is perpendicular to the line connecting the center of the adjacent sphere and the center of the selected sphere.

[0046] Then, draw a circular sketch with a diameter of g at the center of the reference plane 2, and use this as a basis to generate two different helices. The height of the two helices is f, the number of turns is 1, and the starting angles are 0° and 180° respectively.

[0047] Using a circle with diameter i as the scanning contour, perform scanning operations along the two spiral lines to form a solid. Then, create reference axis 4 and reference axis 5 in the right view reference plane and the top view reference plane, respectively. Both of them pass through the center of the rhombus sphere. Reference axis 4 is perpendicular to the top view reference plane, and reference axis 5 is perpendicular to the right view reference plane. Next, mirror the above scanning command once each with the right view reference plane and the top view reference plane as mirror planes. Finally, perform two rotation array operations. First, rotate the mirror command around reference axis 4 three times at equal intervals, and then rotate the command around reference axis 5 three times at equal intervals. The total angle is 360°, completing the creation of the rhombus sphere of revolution.

[0048] Subsequently, the solid is removed by scanning and cutting, using the previously drawn spiral and the line connecting the centers of the spheres as paths. The cutting contours of both types of paths are circular, with the diameter of the circular contour corresponding to the line connecting the centers of the spheres being r1 and the diameter of the circular contour corresponding to the spiral being r1 / 2. This completes the solid removal. Referring to the steps of creating a rotating array of rhomboids of revolution, a rotating array is executed on the scanning and cutting structure at the spiral to remove all spirals. Then, a sphere with a diameter of r2 is cut off at the center of each sphere.

[0049] Then, the rhombic rotational body after the above excision operation is subjected to stretch excision processing to cut it into biomimetic rhombic dodecahedral spiral cell units with a size of (4a+s)×(4a+s). At this time, the parameters satisfy the following conditions: ;

[0050] Finally, along... Axial direction, Axial direction and The array is repeated twice along each axis to create a biomimetic rhombic dodecahedral spiral core layer.

[0051] As a preferred design, the steps for the micro-perforated plate and the sound-absorbing lower plate are as follows:

[0052] First, select a reference plane and draw a square sketch of size (12a+3s)×(12a+3s), then extrude it into a plate-like structure with a thickness of B to complete the construction of the sound-absorbing lower plate;

[0053] Based on the sound-absorbing lower plate, at distances A and C from the edge of the sound-absorbing lower plate, a solid structure with a diameter of r1 / 2 is completely cut through it. The cutting command is then executed along... Axial direction and The microperforated plate is constructed by arraying 11 times along each axis and spacing h between instances.

[0054] Preferably, a laser powder bed fusion printing device is used in step 2, and the printing parameters are: laser power 180w, scanning rate 800mm / s, layer thickness 20μm, and scanning spacing 60μm.

[0055] And step 4 specifically includes:

[0056] The printed sandwich structure was immersed in an etching solution prepared by nitric acid and hydrofluoric acid in a volume ratio of 3:1 for 36 seconds to remove the surface oxide scale. After acid washing, the sample was immediately rinsed with running water, and then cleaned with deionized water and anhydrous alcohol in sequence. After cleaning, it was dried with cold air to complete the pretreatment.

[0057] First, one-third of the thickness of the dried sandwich structure is vertically immersed in the modified carbon nanotube solution and left to soak for 45 seconds. Then, it is pulled out of the liquid surface at a speed of 100 mm / min and placed in an oven to cure at 120°C for 2 hours. Next, two-thirds of the thickness of the structure is immersed in the modified carbon nanotube solution, and the above immersion-pulling and curing operations are repeated. Finally, the biomimetic sandwich structure 1 is completely immersed in the modified carbon nanotube solution, and the above immersion-pulling and curing operations are repeated to obtain a sandwich structure covered with a gradient modified carbon nanotube film, thus completing the preparation of the biomimetic heterogeneous protective shell of the submarine.

[0058] As a preferred embodiment, step 3 specifically includes the following steps:

[0059] Step 3.1: Select Zn(NO3)2·6H2O with a purity ≥99%, weigh Zn(NO3)2·6H2O and deionized water in a mass ratio of 446:2991, and prepare a solution with a concentration of 0.5 mol / L. Place the prepared solution in a stirrer and stir continuously at a speed of 250 rpm. During the stirring process, slowly and continuously add 6 mol / L KOH solution. Stop stirring when the pH is adjusted to 12. Pour the resulting solution into a polytetrafluoroethylene box, fix it in an autoclave, and heat it evenly in an oven at 180℃ for 3 hours. After the reaction is completed, remove the autoclave from the oven and cool it to room temperature. Then place the reactants in a centrifuge tube and centrifuge at a speed of 4000 rpm for 5 minutes. After centrifugation, filter to obtain the precipitate.

[0060] Anhydrous ethanol and deionized water were added to the precipitate in sequence, and then the precipitate was centrifuged three times at 4000 rpm to remove impurities. The final precipitate was placed in an oven and heated at 70°C until completely dry. Finally, the dried sample was ground into a fine powder to obtain ZnO.

[0061] Step 3.2: First, mix 15.8 mol / L HNO3 and 18.4 mol / L H2SO4 solutions at a volume ratio of 1:3. Then, select MWCNTs with an outer diameter range of 3–15 nm and disperse them in the mixed solution. Weigh the MWCNTs according to a mass ratio of 30:130.3 of MWCNTs to the mixed solution. Then, sonicate the mixture at 40 °C for 2.5 h. After sonication, add deionized water to the mixture for dilution. The volume ratio of the mixture to deionized water is 1:4. Stir at 500 rpm for 1 h in a stirrer. After stirring, filter the mixture using a PTFE membrane and wash it with distilled water until the sample pH reaches 7. Finally, dry the sample in an oven at 80 °C for 6 h to obtain multi-walled carbon nanotubes with carboxylated surfaces, i.e., COOH-MWCNTs.

[0062] Step 3.3: Weigh COOH-MWCNTs and ZnO at a mass ratio of 6:94, add them to anhydrous ethanol to prepare a 4 mg / mL solution, and sonicate the mixture for 1 hour. After sonication, stir at 250 rpm for 1 hour to obtain a ZnO@MWCNTs solution. Transfer the ZnO@MWCNTs solution to a polytetrafluoroethylene box, fix it in an autoclave, and heat it uniformly at 180°C for 3 hours in an oven. Then remove the autoclave from the oven and cool it to room temperature. Pour the reaction mixture into a centrifuge tube, centrifuge at 4000 rpm for 5 minutes, filter to obtain the precipitate, and place the final precipitate in an oven and heat it at 70°C until completely dry to obtain ZnO@MWCNTs particles.

[0063] Step 3.4: Mix PDMS and curing agent at a mass ratio of 10:1 and add them to n-hexane solution to prepare a 22 g / L solution. Stir at room temperature for 15 min to obtain PDMS solution. Then add ZnO@MWCNTs particles to PDMS solution at a mass ratio of 2:11. Stir the mixed solution at 400 rpm for 1 h to obtain modified carbon nanotube solution.

[0064] The present invention also provides a multi-dimensional stealth biomimetic heterogeneous protective shell for submarines, which is prepared by the method described above.

[0065] The present invention has the following beneficial effects:

[0066] This invention integrates the Bouligand structure of arapaima scales with acoustic structural principles, drawing inspiration from the unique interlayer rotation and spiral ascent configuration of the arapaima scale's microstructure to innovatively construct four biomimetic structures. Based on this, the TPMS structure, proven to have sound absorption potential, was biomimeticly modified by dividing its unit cell structure into four segments and assigning each segment a different rotation angle to simulate the interlayer rotation characteristics in biological tissues. This configuration effectively increases the total crack propagation path length and improves the structure's fracture toughness and damage tolerance while fully preserving its original acoustic properties. Furthermore, a similar spiral ascent concept was introduced to optimize common octagonal and rhombic dodecahedral structures, extending the sound wave propagation path within the structure and promoting multiple reflections to provide sound absorption. This spiral configuration also possesses an efficient energy dissipation mechanism, enabling the material to simultaneously exhibit excellent impact resistance, high stiffness, energy absorption characteristics, and good toughness while maintaining lightweight properties. This biomimetic design not only effectively suppresses deformation and improves overall structural stability, but also provides an innovative solution for achieving integrated mechanical load-bearing and acoustic stealth functions for submarine hulls through force-sound coupling control.

[0067] This invention proposes a carbon nanotube modification method that achieves synergistic optimization of electromagnetic and optical stealth. Utilizing the extremely high electrical conductivity of multi-walled carbon nanotubes (MWCNTs), a three-dimensional interpenetrating conductive network is formed within the matrix. Incident electromagnetic waves undergo multiple reflections and scatterings within this network, effectively attenuating and absorbing them. Simultaneously, ZnO particles with high dielectric loss characteristics are added. Their high dielectric constant and dielectric loss tangent cause repeated polarization and rearrangement of molecules or electrons in a magnetic field, thus dissipating the energy of the electromagnetic waves.

[0068] By functionalizing MWCNTs, introducing carboxyl groups (-COOH) can interact with Zn. 2+ Strong electrostatic attraction and coordination occur, causing Zn 2+ It effectively anchors to the surface of MWCNTs to achieve high interfacial bonding strength and is not easy to fall off.

[0069] Due to their unique arrangement structure, large specific surface area, and numerous interfaces created by their tubular structure, multi-walled carbon nanotubes undergo multiple reflection-absorption cycles when incident light, resulting in extremely low light reflectivity. They are also among the blackest known man-made materials, capable of absorbing most visible light and exhibiting excellent optical stealth properties.

[0070] PDMS is a good binder that can fix ZnO@MWCNTs particles to the substrate surface and prevent the coating from peeling off.

[0071] The biomimetic heterogeneous submarine hull structure proposed in this invention achieves an organic fusion of impact resistance and integrated acoustic-magnetic-optical stealth effects through a spatial coupling design of biomimetic mechanical configuration and multifunctional materials. The surface of the biomimetic sandwich structure is coated with a gradient concentration of modified carbon nanotube films, causing different regions to exhibit different impedance values. When electromagnetic waves or light waves are incident, they are reflected at the impedance-changing interface and reabsorbed by the upper modified carbon nanotube film, thus forming a "multiple reflection-reabsorption" energy dissipation mechanism. This submarine hull strategy, relying on the dual characteristics of high load-bearing capacity and multi-dimensional stealth, provides an innovative solution for submarines to meet multifunctional requirements in complex working environments. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of the present invention;

[0073] Figure 2 This is a flowchart of the biomimetic Primitive multi-level rotating core layer design in this invention;

[0074] Figure 3 This is an enlarged schematic diagram of the connecting plate in this invention;

[0075] Figure 4 This is a flowchart of the biomimetic Diamond multi-level rotating core layer design in this invention;

[0076] Figure 5 This is a flowchart illustrating the design process of the biomimetic octagonal spiral core layer in this invention.

[0077] Figure 6 This is a schematic diagram showing the position of reference plane 1 in this invention;

[0078] Figure 7 This is a flowchart illustrating the design process of the biomimetic rhombic dodecahedral helical core layer in this invention.

[0079] Figure 8 This is a schematic diagram showing the position of reference plane 2 in this invention;

[0080] Figure 9 This is a design flowchart of the micro-perforated plate and the sound-absorbing lower plate in this invention;

[0081] Figure 10 This is an enlarged schematic diagram of the micro-perforated plate in this invention;

[0082] Figure 11 This is a flowchart illustrating the modification process of carbon nanotubes in this invention.

[0083] Figure 12 This is a flowchart illustrating the fabrication process of the biomimetic heterogeneous submarine hull in this invention.

[0084] In the diagram: 1. Sandwich structure; 11. Bionic Primitive multi-level rotating core layer; 12. Bionic Diamond multi-level rotating core layer; 13. Bionic octagonal spiral core layer; 14. Bionic rhombic dodecahedral spiral core layer; 15. Micro-perforated plate; 16. Sound-absorbing lower plate; 111. P-type cell structure; 112. P-type lattice structure; 113. Cross-shaped plate structure; 114. Connecting plate; 115. P-type -0° structure; 116. P-type -15° structure; 117. P-type -30° structure; 118. P-type -45° structure; 119. Bionic Primitive multi-level cell; 121. D-type cell structure; 122. D-type lattice structure; 123. D-type -0° Structures; 124, D-type -15° structure; 125, D-type -30° structure; 126, D-type -45° structure; 127, biomimetic diamond multilevel cell; 131, octagonal sphere structure; 132, octagonal rotation body; 134, biomimetic octagonal spiral cell; 141, rhombic sphere; 142, rhombic rotation body; 144, biomimetic rhombic dodecahedral spiral cell; 2, modified carbon nanotube film; 3, biomimetic heterogeneous protective shell for submarines; 21, ZnO@MWCNTs particles; 22, PDMS solution; 23, modified carbon nanotube solution; 4, electron microscope image of Arapaima scales; 5, laser powder bed fusion printing equipment; 6, electron microscope image of TC4 alloy powder; 7, etching solution. Detailed Implementation

[0085] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0086] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0087] Embodiments of the present invention:

[0088] like Figures 1 to 12 As shown ( Figure 1 In the middle, image 4 shows an electron microscope image of scales on the Arapaima gigantea; Figure 12 In the image (5 is a laser powder bed fusion printing device, 6 is an electron microscope image of TC4 alloy powder), a method for preparing a multi-dimensional stealth submarine biomimetic heterogeneous protective hull includes the following steps:

[0089] Step 1: Establish the mezzanine structure 1 using 3D modeling software;

[0090] Step 2: Convert the sandwich structure 1 designed in Step 1 into an STL format file and import it into the Magics software. Based on the selective laser melting technology, the sandwich structure 1 made of TC4 titanium alloy is prepared.

[0091] Step 3: The preparation of ZnO, the functionalization treatment of MWCNTs and the preparation of ZnO@MWCNTs particles 21 are completed in sequence. Then, ZnO@MWCNTs particles 21 are added to PDMS solution 22 to complete the modification of ZnO@MWCNTs particles 21 and obtain modified carbon nanotube solution 23.

[0092] Step 4: First, pre-treat the sandwich structure 1 obtained in step 2. After treatment, place the sandwich structure 1 into the modified carbon nanotube solution 23. Then, perform stepwise impregnation on the sandwich structure 1 by the impregnation-pulling method. After repeated drying and impregnation, the sandwich structure 1 is covered with a gradient modified carbon nanotube film 2, thereby obtaining the submarine biomimetic heterogeneous protective shell 3.

[0093] The sandwich structure 1 in step 1 includes a biomimetic multi-level rotating core layer 11, a biomimetic diamond multi-level rotating core layer 12, a biomimetic octagonal spiral core layer 13, a biomimetic rhombic dodecahedral spiral core layer 14, a micro-perforated plate 15, and a sound-absorbing lower plate 16. Multiple biomimetic multi-level rotating core layers 11, biomimetic diamond multi-level rotating core layers 12, biomimetic octagonal spiral core layers 13, and biomimetic rhombic dodecahedral spiral core layers 14 are arranged between the micro-perforated plate 15 and the sound-absorbing lower plate 16.

[0094] Among them, such as Figure 2 and Figure 3 As shown, the design steps of the biomimetic Primitive multi-level rotating core layer 11 are as follows:

[0095] First, in Matlab software, using implicit function formulas... Modeling is performed, in which , , These are the three-dimensional coordinates of the point, A. p B p and C p For biomimetic structures in , and The period in the three directions of the coordinate system;

[0096] After completing the modeling, import the STL file generated by the software into SolidWorks to construct a P-type cell structure 111 with a size of a×a×a. Then, arrange the P-type cell structure 111 along... Arrayed once along the axis, along Axial direction and The array is arrayed four times along each axis to construct a P-type lattice structure 112;

[0097] Next, create rectangular sketches of size 4a+s×4a+s at the coordinate centers of the front and right reference planes respectively. Then, extrude the sketches into a cross-shaped plate structure 113 with a thickness of s. At this point, the space is divided into four regions by the cross-shaped plate structure 113. On one face of one of the regions, completely cut a circular hole with a diameter of r at a distance of d from the top edge and b from the side edge. Then, cut the circular hole along... Arrayed once along the axis with a spacing of l, and along... The axis is arrayed twice at a spacing of d. Then, a reference axis 1 is created at the intersection of the front reference plane and the right reference plane. The linear array command of the above-mentioned circular holes is rotated around the reference axis 1 with a total rotation angle of 360° and arrayed three times at equal intervals to complete the construction of the connecting plate 114.

[0098] Subsequently, a rectangular outline of size 2a×4a+s is drawn at the center of the right-side reference plane of the P-type lattice structure 112. This outline is then cut to obtain the P-type -0° structure 115. Finally, three rotation commands are executed sequentially on the P-type lattice structure 112, around... The shaft is subjected to axial rotation operations of 15°, 30° and 45° respectively, and cut in the same way to generate P-type -15° structure 116, P-type -30° structure 117 and P-type -45° structure 118 in sequence;

[0099] Then, import the P-type -0° structure 115, P-type -15° structure 116, P-type -30° structure 117, P-type -45° structure 118 and the connecting plate 114 into the same part environment. By aligning the surfaces, make the structural surfaces of the P-type -0° structure 115, P-type -15° structure 116, P-type -30° structure 117, and P-type -45° structure 118 coincide with the corresponding surfaces of the four areas of the connecting plate 114, forming a structure with the top surface aligned with the top surface, the side surface aligned with the side surface, and the overall size of 4a+s×4a+s. Then merge them into a single entity to complete the establishment of the biomimetic Primitive multilevel cell 119.

[0100] Finally, the biomimetic Primitive multilevel cell 119 was arranged along... Axial direction, Axial direction and The array is arrayed twice along each axis to create a biomimetic multi-level rotating core layer 11.

[0101] like Figure 4 As shown, the design steps of the biomimetic Diamond multi-level rotating core layer 12 are as follows:

[0102] First, model the model using implicit function formulas in Matlab software, as shown in the following formula:

[0103] ;

[0104] in, , , These are the three-dimensional coordinates of the point. , and For biomimetic structures in , and The period in the three directions of the coordinate system;

[0105] After completing the modeling, import the STL file generated by the software into SolidWorks to construct a D-type cell structure 121 with dimensions of a×a×a. Then, place the D-type cell structure 121 along... Arrayed once along the axis, along Axial direction and The array is arrayed four times along each axis to construct a D-type lattice structure 122.

[0106] Then, complete the construction of the connecting plate 114 on the front view reference plane and the right view reference plane;

[0107] Subsequently, a rectangular outline of size 2a×4a+s is drawn at the center of the right-side reference plane of the D-type lattice structure 122. This outline is then cut to obtain the D-type -0° structure 123. Finally, three rotation commands are executed sequentially on the D-type lattice structure 122, around... The shaft is subjected to axial rotation operations of 15°, 30° and 45° respectively, and cut in the same way to generate D-type -15° structure 124, D-type -30° structure 125 and D-type -45° structure 126 in sequence;

[0108] Then, import the D-type -0° structure 123, D-type -15° structure 124, D-type -30° structure 125, D-type -45° structure 126 and connecting plate 114 into the same part environment. By aligning the surfaces, make the structural surfaces of the D-type -0° structure 123, D-type -15° structure 124, D-type -30° structure 125, D-type -45° structure 126 and connecting plate 114 coincide with the corresponding surfaces of the four areas of connecting plate 114, forming a structure with the top surface aligned with the top surface, the side surface aligned with the side surface, and the overall size of 4a+s×4a+s. Then merge them into a single entity to complete the establishment of the biomimetic Diamond multilevel cell 127.

[0109] Finally, the biomimetic Diamond multilevel cell 127 was arranged along... Axial direction, Axial direction and The array was repeated three times along each axis to create a biomimetic Diamond multi-level rotating core layer 12.

[0110] like Figure 5 and Figure 6 As shown, the design steps of the biomimetic octagonal spiral core layer 13 are as follows:

[0111] First, draw a c×c×c cube using a 3D sketch. The center of the sketch should be at the intersection of the right view reference plane and the top view reference plane.

[0112] Create vertex spheres with diameter R at the vertex positions of the cube sketch, create face-centered spheres with diameter R at the center positions of the cube faces, establish lines between the centers of each face-centered sphere, and use these lines as paths to scan with a circular outline of diameter h to generate the corresponding cylinders, thereby constructing an octagonal sphere structure 131.

[0113] Select one of the face-centered spheres in the octagonal sphere structure 131. Using the horizontal line 1 passing through the center of the face-centered sphere (the horizontal line 1 is parallel to the top reference plane and perpendicular to the right reference plane) as a reference, create a reference plane 1 at a position 45° away from it and at a distance e. The reference plane 1 is perpendicular to the line connecting the centers of the vertex sphere and the face-centered sphere.

[0114] Then, draw a circular sketch with a diameter of g at the center of the reference plane 1. Based on this, generate two different helices. The height of both helices is set to f, the number of turns is set to 1, and the starting angles are set to 0° and 180° respectively.

[0115] Then, using a circle with diameter i as the scanning contour, scanning operations are performed along the two spiral lines to form a solid. Next, reference axis 2 and reference axis 3 are created in the right view reference plane and the top view reference plane, respectively. Both of them pass through the body center of the octagonal sphere structure 131. Reference axis 2 is perpendicular to the top view reference plane, and reference axis 3 is perpendicular to the right view reference plane. Then, the above scanning command is mirrored once each with the right view reference plane and the top view reference plane as mirror planes. Finally, two rotation array operations are performed. First, the mirror command is rotated three times around reference axis 2 at equal intervals, with a total angle of 360°. Then, the same array operation is performed around reference axis 3 (rotating the array three times at equal intervals, with a total angle of 360°), completing the creation of the octagonal sphere 132.

[0116] Subsequently, the solid is cut along the spiral path and the line path connecting the face-centered spheres using a scanning cut method. The cut contours used for both types of paths are circular. The diameter of the circular contour corresponding to the line connecting the face-centered spheres is r1, and the diameter of the circular contour corresponding to the spiral is r1 / 2. This completes the solid cut. Referring to the above steps for creating the octagonal rotator 132, a rotation array is executed on the scanning cut structure at the spiral to cut all the spirals. Then, a sphere with a diameter of r2 is cut off at the center of each sphere.

[0117] Subsequently, the octagonal rotor 132, after the above-mentioned excision operation, is processed by stretch excision to cut it into biomimetic octagonal spiral cells 134 with a size of 4a+s×4a+s. At this time, the parameters satisfy the following conditions: ;

[0118] Finally, along... Axial direction, Axial direction and The array is repeated 3 times along each axis to create a biomimetic octagonal spiral core layer 13.

[0119] like Figure 7 and Figure 8 As shown, the design steps of the biomimetic rhombic dodecahedral spiral core layer 14 are as follows:

[0120] First, using the intersection of the right view reference plane and the top view reference plane as the sketch center, draw a cube of size c×c×c using 3D sketching;

[0121] Then, rotate the cube sketch to generate a central sphere with a diameter of R at the center of the cube sketch, and rotate the cube sketch to generate edge spheres with a diameter of R at the center of each edge. Then connect the centers of the central sphere and the edge spheres, use the sweep command with a circular outline diameter of h to generate the corresponding cylinder, and then execute the combine command to merge all entities into a rhombus sphere 141.

[0122] Select a side sphere in the rhomboid sphere 141. Using the horizontal line 2 passing through the center of the sphere (the horizontal line 2 is parallel to the top reference plane and perpendicular to the right reference plane) as a reference, create a reference plane 2 at a distance e that is 45° away from it. The reference plane 2 is perpendicular to the line connecting the center of the adjacent sphere and the center of the selected sphere.

[0123] Then, draw a circular sketch with a diameter of g at the center of the reference plane 2, and use this as a basis to generate two different helices. The height of the two helices is f, the number of turns is 1, and the starting angles are 0° and 180° respectively.

[0124] Using a circle with diameter i as the scanning contour, perform scanning operations along the two spiral lines to form a solid. Then, create reference axes 4 and 5 in the right and top reference planes, both of which pass through the center of the rhombic sphere 141. Reference axis 4 is perpendicular to the top reference plane, and reference axis 5 is perpendicular to the right reference plane. Then, mirror the above scanning command once each with the right and top reference planes as mirror planes. Finally, perform two rotation array operations. First, rotate the mirror command around reference axis 4 three times at equal intervals, with a total angle of 360°. Then, perform the same array operation around reference axis 5 (rotate the array three times at equal intervals, with a total angle of 360°) to complete the creation of the rhombic spherical sphere 142.

[0125] Subsequently, the solid is cut using a scanning cut method, with the previously drawn spiral and the line connecting the centers of the spheres as the path. The cut contours of both types of paths are circular, with the diameter of the circular contour corresponding to the line connecting the centers of the spheres being r1 and the diameter of the circular contour corresponding to the spiral being r1 / 2. This completes the solid cut. Referring to the above steps for creating the rhomboid rotatable body 142, the scanning cut structure at the spiral is subjected to a rotation array to cut all the spirals. Then, a sphere with a diameter of r2 is cut off at the center of each sphere.

[0126] Then, the rhombic rotating body 142, after the above-mentioned excision operation, is excised by stretching excision to cut it into a biomimetic rhombic dodecahedral spiral cell 144 with a size of 4a+s×4a+s. At this time, the parameters satisfy the following conditions: ;

[0127] Finally, along... Axial direction, Axial direction and The array is repeated twice along each axis to create a biomimetic rhombic dodecahedral spiral core layer 14.

[0128] like Figure 9 and Figure 10 As shown, the design steps for the micro-perforated plate 15 and the sound-absorbing lower plate 16 are as follows:

[0129] First, select a reference plane and draw a square sketch of size 12a+3s×12a+3s, then extrude it into a plate-like structure with a thickness of B to complete the construction of the sound-absorbing lower plate 16;

[0130] Based on the sound-absorbing lower plate 16, at positions A and C away from the edge of the sound-absorbing lower plate 16, a solid structure with a diameter of r1 / 2 is completely cut through. Then, this cut is performed along... Axial direction and The micro-perforated plate 15 is constructed by arraying 11 times along each axis and spacing h between instances.

[0131] It should be noted that in step 2, the laser powder bed fusion printing equipment 5 uses TC4 alloy powder to prepare the sandwich structure 1. The printing parameters used are: laser power 180W, scanning rate 800mm / s, layer thickness 20μm, and scanning spacing 60μm. This strategy has been proven to print lattice structures with an accuracy of 0.1mm.

[0132] like Figure 11 As shown, step 3 specifically includes the following steps:

[0133] Step 3.1: Select zinc nitrate hexahydrate (Zn(NO3)2·6H2O) with a purity ≥99%. Weigh Zn(NO3)2·6H2O and deionized water in a mass ratio of 446:2991 to prepare a 0.5 mol / L solution. Place the prepared solution in a stirrer and stir continuously at 250 rpm. During the stirring process, slowly and continuously add 6 mol / L KOH solution. Stop stirring when the pH is adjusted to 12. Pour the resulting solution into a polytetrafluoroethylene box, fix it in an autoclave, and heat it uniformly in an oven at 180°C for 3 hours. After the reaction is complete, remove the autoclave from the oven and cool it to room temperature. Then place the reactants in a centrifuge tube and centrifuge at 4000 rpm for 5 minutes. After centrifugation, filter to obtain the precipitate.

[0134] Anhydrous ethanol and deionized water were added to the precipitate in sequence, and then the precipitate was centrifuged three times at 4000 rpm to remove impurities. The final precipitate was placed in an oven and heated at 70°C until completely dry. Finally, the dried sample was ground into a fine powder to obtain high-purity ZnO.

[0135] Step 3.2: Mix 15.8 mol / L concentrated nitric acid (HNO3) and 18.4 mol / L concentrated sulfuric acid (H2SO4) solutions at a volume ratio of 1:3. Select multi-walled carbon nanotubes (MWCNTs) with an outer diameter range of 3–15 nm and disperse them in the mixed solution. Weigh MWCNTs according to a mass ratio of 30:130.3 of MWCNTs to the mixed solution. Then, sonicate the mixture at 40 °C for 2.5 h. After sonication, dilute the mixture with deionized water (volume ratio of mixture to deionized water is 1:4). Then, stir at 500 rpm for 1 h in a stirrer. After stirring, filter the mixture using a PTFE membrane and wash it with distilled water until the sample pH reaches 7. Finally, dry the sample in an oven at 80 °C for 6 h to obtain multi-walled carbon nanotubes with carboxylated surfaces, i.e., COOH-MWCNTs.

[0136] Step 3.3: Weigh COOH-MWCNTs and ZnO at a mass ratio of 6:94, add them to anhydrous ethanol to prepare a 4 mg / mL solution, and sonicate the mixture for 1 hour to ensure uniform dispersion of the solids. After sonication, stir at 250 rpm for 1 hour to ensure complete and uniform dispersion of the substances, obtaining a ZnO@MWCNTs solution. Transfer the ZnO@MWCNTs solution to a polytetrafluoroethylene box, fix it in an autoclave, and heat it uniformly at 180°C for 3 hours in an oven. Then remove the autoclave from the oven and cool it to room temperature. Pour the reaction mixture into a centrifuge tube, centrifuge at 4000 rpm for 5 minutes, filter to obtain the precipitate, and place the final precipitate in an oven and heat it at 70°C until completely dry to obtain ZnO@MWCNTs particles 21.

[0137] Step 3.4: PDMS (Dow Corning DC184A) and curing agent (Dow Corning DC184B) are mixed in a mass ratio of 10:1 and added to a hexane solution to prepare a 22 g / L solution. The solution is stirred at room temperature for 15 min to obtain PDMS solution 22. Then, ZnO@MWCNTs particles 21 are added to PDMS solution 22 in a mass ratio of 2:11. The mixed solution is stirred at 400 rpm for 1 h to obtain modified carbon nanotube solution 23.

[0138] like Figure 12 As shown, step 4 specifically involves:

[0139] The printed sandwich structure 1 was immersed in the etching solution 7 prepared by nitric acid (HNO3) and hydrofluoric acid (HF) in a volume ratio of 3:1 for 36 seconds to remove the surface oxide scale. After acid washing, the sample was immediately rinsed with running water, and then cleaned with deionized water and anhydrous alcohol in sequence. After cleaning, it was dried with cold air to complete the pretreatment.

[0140] First, one-third of the thickness of the dried sandwich structure 1 is vertically immersed in the modified carbon nanotube solution 23 and left to soak for 45 seconds. Then, it is pulled out of the liquid surface at a speed of 100 mm / min and placed in an oven to cure at 120°C for 2 hours. Next, two-thirds of the thickness of the structure is immersed in the modified carbon nanotube solution 23, and the above immersion-pulling and curing operations are repeated. Finally, the biomimetic sandwich structure 1 is completely immersed in the modified carbon nanotube solution 23, and the above immersion-pulling and curing operations are repeated to obtain the sandwich structure 1 covered with a gradient modified carbon nanotube film 2, thus completing the preparation of the submarine biomimetic heterogeneous protective shell 3.

[0141] In summary, this invention integrates the Bouligand structure of Arapaima scales and acoustic structural principles, drawing inspiration from the unique interlayer rotation and spiral ascent configuration of the Arapaima scales' microstructure. It innovatively constructs four biomimetic structures (biomimetic Primitive multi-level rotating core layer 11, biomimetic Diamond multi-level rotating core layer 12, biomimetic octagonal spiral core layer 13, and biomimetic rhombic dodecahedral spiral core layer 14). Based on this, the TPMS structure, which has been proven to have sound absorption potential, is biomimeticly modified by dividing its unit cell structure into four segments and assigning each segment a different rotation angle to simulate the interlayer rotation characteristics in biological tissues. This configuration effectively increases the total path length of crack propagation and improves the fracture toughness and damage tolerance of the structure while fully preserving its original acoustic properties. Furthermore, a similar spiral ascent concept is introduced to optimize the common octagonal and rhombic dodecahedral structures, extending the propagation path of sound waves within the structure and promoting multiple reflections, thereby providing a sound absorption effect. This helical configuration also possesses an efficient energy dissipation mechanism, enabling the material to simultaneously exhibit excellent impact resistance, high stiffness, energy absorption characteristics, and good toughness while maintaining lightweight properties. This biomimetic design not only effectively suppresses deformation and enhances overall structural stability, but also provides an innovative solution for achieving integrated mechanical load-bearing and acoustic stealth functions for submarine hulls through force-acoustic coupling control.

[0142] This invention proposes a carbon nanotube modification method that achieves synergistic optimization of electromagnetic and optical stealth. Utilizing the extremely high electrical conductivity of multi-walled carbon nanotubes (MWCNTs), a three-dimensional interpenetrating conductive network is formed within the matrix. Incident electromagnetic waves undergo multiple reflections and scatterings within this network, effectively attenuating and absorbing them. Simultaneously, ZnO particles with high dielectric loss characteristics are added. Their high dielectric constant and dielectric loss tangent cause repeated polarization and rearrangement of molecules or electrons in a magnetic field, thus dissipating the energy of the electromagnetic waves.

[0143] By functionalizing MWCNTs, introducing carboxyl groups (-COOH) can interact with Zn. 2+ Strong electrostatic attraction and coordination occur, causing Zn 2+ It effectively anchors to the surface of MWCNTs to achieve high interfacial bonding strength and is not easy to fall off.

[0144] Due to their unique arrangement structure, large specific surface area, and numerous interfaces created by their tubular structure, multi-walled carbon nanotubes undergo multiple reflection-absorption cycles when incident light, resulting in extremely low light reflectivity. They are also among the blackest known man-made materials, capable of absorbing most visible light and exhibiting excellent optical stealth properties.

[0145] PDMS is a good binder that can fix ZnO@MWCNTs particles 21 to the substrate surface and prevent the coating from peeling off.

[0146] The biomimetic heterogeneous submarine hull structure proposed in this invention, relying on the spatial coupling design of biomimetic mechanical configuration and multifunctional materials, achieves an organic integration of impact resistance and "acoustic-magnetic-optical" stealth effect. The surface of the biomimetic sandwich structure 1 is covered with a gradient concentration modified carbon nanotube film 2, causing different regions to exhibit different impedance values. When electromagnetic waves or light waves are incident, they are reflected at the impedance change interface and reabsorbed by the upper modified carbon nanotube film 2, thus forming a "multiple reflection-reabsorption" energy dissipation mechanism. The submarine hull strategy proposed in this invention, relying on the dual characteristics of high load-bearing capacity and multi-dimensional "stealth," provides an innovative solution for submarines to meet multifunctional requirements in complex working environments.

[0147] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a multi-dimensional stealth biomimetic heterogeneous protective hull for submarines, characterized in that, Includes the following steps: Step 1: Establish the mezzanine structure (1) using 3D modeling software; Step 2: Convert the sandwich structure (1) designed in Step 1 into an STL format file and import it into the Magics software. Based on the selective laser melting technology, a sandwich structure (1) made of TC4 titanium alloy is prepared. Step 3: The preparation of ZnO, the functionalization of MWCNTs and the preparation of ZnO@MWCNTs particles (21) are completed in sequence. Then, the ZnO@MWCNTs particles (21) are added to PDMS solution (22) to complete the modification of ZnO@MWCNTs particles (21) and obtain modified carbon nanotube solution (23). Step 4: First, pre-treat the sandwich structure (1) obtained in step 2. After treatment, place the sandwich structure (1) into the modified carbon nanotube solution (23). Use the dip-pull method to dip the sandwich structure (1) step by step. After repeated drying and dipping, the sandwich structure (1) is covered with a gradient modified carbon nanotube film (2), thereby obtaining the submarine biomimetic heterogeneous protective shell (3).

2. The method for preparing a multi-dimensional stealth submarine biomimetic heterogeneous protective hull according to claim 1, characterized in that, The sandwich structure (1) in step 1 includes a biomimetic Primitive multi-level rotating core layer (11), a biomimetic Diamond multi-level rotating core layer (12), a biomimetic octagonal spiral core layer (13), a biomimetic rhombic dodecahedral spiral core layer (14), a micro-perforated plate (15), and a sound-absorbing lower plate (16). Multiple biomimetic Primitive multi-level rotating core layers (11), biomimetic Diamond multi-level rotating core layers (12), biomimetic octagonal spiral core layers (13), and biomimetic rhombic dodecahedral spiral core layers (14) are arranged between the micro-perforated plate (15) and the sound-absorbing lower plate (16).

3. The method for preparing a multi-dimensional stealth submarine biomimetic heterogeneous protective hull according to claim 2, characterized in that, The design steps of the biomimetic Primitive multi-level rotating core layer (11) are as follows: First, in Matlab software, using implicit function formulas... Modeling is performed, in which , , These are the three-dimensional coordinates of the point, A. p B p and C p For biomimetic structures in , and The period in three directions of the coordinate system; After completing the modeling, the STL file generated by the software is imported into SolidWorks to construct a P-type cell structure (111) with a size of a×a×a. Then, the P-type cell structure (111) is arranged along... Arrayed once along the axis, along Axial direction and The array is arranged four times along each axis to construct a P-type lattice structure (112). Next, create rectangular sketches of size (4a+s)×(4a+s) at the coordinate centers of the front and right reference planes respectively. Then, extrude the sketches into a cross-shaped plate structure (113) with a thickness of s. At this time, the space is divided into four regions by the cross-shaped plate structure (113). On one face of one of the regions, completely cut out a circular hole with a diameter of r at a distance of d from the top edge and b from the side edge. Then, cut the circular hole along... Arrayed once along the axis with a spacing of l, and along... The axis is arrayed twice at a spacing of d. Then, a reference axis 1 is created at the intersection of the front reference plane and the right reference plane. The linear array command of the above-mentioned circular holes is rotated around the reference axis 1 with a total rotation angle of 360°. The array is then arrayed three times at equal intervals to complete the construction of the connecting plate (114). Subsequently, a rectangular outline of size 2a×(4a+s) is drawn at the center of the right reference plane of the P-type lattice structure (112). The P-type -0° structure (115) is obtained by cutting. Then, three rotation commands are executed on the P-type lattice structure (112) in sequence, around The shaft is subjected to axial rotation operations of 15°, 30° and 45° respectively, and cut in the same way to generate P-type -15° structure (116), P-type -30° structure (117) and P-type -45° structure (118) in sequence. Then, import the P-type -0° structure (115), P-type -15° structure (116), P-type -30° structure (117), P-type -45° structure (118) and connecting plate (114) into the same part environment. By aligning the faces, make the structural surfaces of the P-type -0° structure (115), P-type -15° structure (116), P-type -30° structure (117), and P-type -45° structure (118) coincide with the corresponding surfaces of the four areas of the connecting plate (114), forming a structure with the top surface aligned with the top surface, the side surface aligned with the side surface, and the overall size of (4a+s)×(4a+s). Then merge them into a solid to complete the establishment of the biomimetic Primitive multilevel cell (119). Finally, the biomimetic Primitive multilevel cell (119) was arranged along... Axial direction, Axial direction and The array is arrayed twice along each axis to create a biomimetic multi-level rotating core layer (11).

4. The method for preparing a multi-dimensional stealth submarine biomimetic heterogeneous protective hull according to claim 3, characterized in that, The design steps of the biomimetic Diamond multi-level rotating core layer (12) are as follows: First, model the model using implicit function formulas in Matlab software, as shown in the following formula: ； in, , , These are the three-dimensional coordinates of the point. , and For biomimetic structures in , and The period in three directions of the coordinate system; After completing the modeling, the STL file generated by the software is imported into SolidWorks to construct a D-type cell structure (121) with a size of a×a×a. Then, the D-type cell structure (121) is arranged along... Arrayed once along the axis, along Axial direction and The array is performed four times along each axis to construct a D-shaped lattice structure (122); Then, the connecting plate (114) is constructed on the front and right reference planes; Subsequently, a rectangular outline of size 2a×(4a+s) is drawn at the center of the right reference plane of the D-type lattice structure (122). The D-type -0° structure (123) is obtained by cutting. Then, three rotation commands are executed on the D-type lattice structure (122) in sequence, around The shaft is subjected to axial rotation operations of 15°, 30° and 45° respectively, and cut in the same way to generate D-type -15° structure (124), D-type -30° structure (125) and D-type -45° structure (126) in sequence. Then, import the D-type -0° structure (123), D-type -15° structure (124), D-type -30° structure (125), D-type -45° structure (126) and connecting plate (114) into the same part environment. By face alignment, make the structural surfaces of the D-type -0° structure (123), D-type -15° structure (124), D-type -30° structure (125), D-type -45° structure (126) and connecting plate (114) coincide with the corresponding surfaces of the four areas of the connecting plate (114), forming a structure with top surface aligned with top surface, side surface aligned with side surface, and overall size of (4a+s)×(4a+s). Then merge them into a solid to complete the establishment of the biomimetic Diamond multi-level cell (127). Finally, the biomimetic Diamond multilevel cell (127) was arranged along... Axial direction, Axial direction and The array was repeated three times along each axis to create a biomimetic Diamond multi-level rotating core layer (12).

5. The method for preparing a multi-dimensional stealth submarine biomimetic heterogeneous protective hull according to claim 4, characterized in that, The design steps of the biomimetic octagonal spiral core layer (13) are as follows: First, draw a cube of size c×c×c using a 3D sketch. The center of the sketch should be at the intersection of the right view reference plane and the top view reference plane. Create vertex spheres with diameter R at the vertex positions of the cube sketch, create face-centered spheres with diameter R at the center positions of the cube faces, establish lines between the centers of each face-centered sphere, and use these lines as paths to scan with a circular outline of diameter h to generate corresponding cylinders, thereby constructing an octagonal sphere structure (131). Select a face-centered sphere in the octagonal sphere structure (131), and take the horizontal line 1 passing through the center of the face-centered sphere as a reference. The horizontal line 1 is parallel to the upper reference plane and perpendicular to the right reference plane. Create a reference plane 1 at a position 45° away from it and a distance of e. The reference plane 1 is perpendicular to the line connecting the centers of the spheres between the vertex sphere and the face-centered sphere. Then, draw a circular sketch with a diameter of g at the center of the reference plane 1. Based on this, generate two different helices. The height of both helices is set to f, the number of turns is set to 1, and the starting angles are set to 0° and 180° respectively. Then, using a circle with diameter i as the scanning outline, the scanning operation is performed along the two spiral lines to form a solid. Next, reference axis 2 and reference axis 3 are created in the right view reference plane and the top view reference plane respectively. Both of them pass through the center of the octagonal sphere structure (131). Reference axis 2 is perpendicular to the top view reference plane, and reference axis 3 is perpendicular to the right view reference plane. Then, the scanning command is mirrored once each with the right view reference plane and the top view reference plane as mirror planes. Finally, two rotation array operations are performed. First, the mirror command is rotated 3 times around reference axis 2 at equal intervals, with a total angle of 360°. Then, it is rotated 3 times around reference axis 3 at equal intervals, with a total angle of 360°, to complete the creation of the octagonal sphere (132). Subsequently, the solid is cut along the spiral path and the line path between the face-centered spheres by scanning cut method. The cutting contour used for both types of paths is circular. The diameter of the circular contour corresponding to the line between the face-centered spheres is r1, and the diameter of the circular contour corresponding to the spiral is r1 / 2. The solid is cut in this way. Referring to the step of creating the octagonal rotator (132) rotation array, the scanning cut structure at the spiral is rotated to cut all the spirals. Then, a sphere with a diameter of r2 is cut off at the center position of each sphere. Subsequently, the octagonal rotator (132) after the excision operation was performed by stretch excision processing, cutting it into biomimetic octagonal spiral cells (134) with a size of (4a+s)×(4a+s), and the parameters satisfying the following conditions. ; Finally, along... Axial direction, Axial direction and The array is repeated twice along each axis to create a biomimetic octagonal spiral core layer (13).

6. The method for preparing a multi-dimensional stealth submarine biomimetic heterogeneous protective hull according to claim 5, characterized in that, The design steps of the biomimetic rhombic dodecahedral helical core layer (14) are as follows: First, using the intersection of the right view reference plane and the top view reference plane as the sketch center, draw a cube of size c×c×c using 3D sketching; Then, rotate the cube sketch to generate a central sphere with a diameter of R at the center of the cube sketch, and rotate the cube sketch to generate edge spheres with a diameter of R at the center of each edge. Then connect the centers of the central sphere and the edge spheres, use the sweep command with a circular outline diameter of h to generate the corresponding cylinder, and then execute the combine command to merge all entities into a rhombus sphere (141). Select a side sphere in the rhomboid sphere (141), and take the horizontal line 2 passing through the center of the sphere as a reference. The horizontal line 2 is parallel to the upper reference plane and perpendicular to the right reference plane. Create a reference plane 2 at a distance e that is 45° away from it. The reference plane 2 is perpendicular to the line connecting the center of the adjacent sphere and the center of the selected sphere. Then, draw a circular sketch with a diameter of g at the center of the reference plane 2, and use this as a basis to generate two different helices. The height of the two helices is f, the number of turns is 1, and the starting angles are 0° and 180° respectively. Using a circle with diameter i as the scanning outline, perform scanning operations along the two spiral lines to form a solid. Then, create reference axis 4 and reference axis 5 in the right reference plane and the top reference plane respectively. Both of them pass through the center of the rhombic sphere (141). Reference axis 4 is perpendicular to the top reference plane, and reference axis 5 is perpendicular to the right reference plane. Then, mirror the above scanning command once each with the right reference plane and the top reference plane as mirror planes. Finally, perform two rotation array operations. First, rotate the mirror command around reference axis 4 three times at equal intervals, with a total angle of 360°. Then rotate the array around reference axis 5 three times at equal intervals, with a total angle of 360°. This completes the creation of the rhombic rotator (142). Subsequently, the solid is cut by scanning and cutting, using the previously drawn spiral and the line connecting the centers of the spheres as the path. The cutting contours of both types of paths are circular, with the diameter of the circular contour corresponding to the line connecting the centers of the spheres being r1 and the diameter of the circular contour corresponding to the spiral being r1 / 2. This completes the solid cutting. Referring to the steps of creating the rhomboid rotatable body (142), the rotating array is executed on the scanning and cutting structure at the spiral to cut all the spirals. Then, the sphere with a diameter of r2 is cut off at the center of each sphere. Then, the rhombic rotator (142) after the above-mentioned excision operation is subjected to stretch excision processing to cut it into a biomimetic rhombic dodecahedral spiral cell (144) with a size of (4a+s)×(4a+s), wherein the parameters satisfy the following conditions. ; Finally, along... Axial direction, Axial direction and The array is repeated twice along each axis to create a biomimetic rhombic dodecahedral spiral core layer (14).

7. The method for preparing a multi-dimensional stealth submarine biomimetic heterogeneous protective hull according to claim 6, characterized in that, The design steps for the micro-perforated plate (15) and the sound-absorbing lower plate (16) are as follows: First, select a reference plane to draw a square sketch of size (12a+3s)×(12a+3s), and then extrude it into a plate structure with a thickness of B to complete the construction of the sound-absorbing lower plate (16); Based on the sound-absorbing lower plate (16), at positions A and C away from the edge of the sound-absorbing lower plate (16), a solid structure with a diameter of r1 / 2 is completely cut through, and then the cutting command is followed along... Axial direction and The micro-perforated plate (15) is constructed by arraying 11 times in each axial direction and spacing h between instances.

8. The method for preparing a multi-dimensional stealth submarine biomimetic heterogeneous protective hull according to claim 7, characterized in that, In step 2, a laser powder bed fusion printing device is used, and the printing parameters are: laser power 180w, scanning rate 800mm / s, layer thickness 20μm, and scanning spacing 60μm. And step 4 specifically includes: The printed sandwich structure (1) was immersed in an etching solution (7) prepared by nitric acid and hydrofluoric acid in a volume ratio of 3:1 for 36 seconds to remove the surface oxide scale. After acid washing, the sample was immediately rinsed with running water and then cleaned with deionized water and anhydrous alcohol in sequence. After cleaning, it was dried with cold air to complete the pretreatment. First, one-third of the thickness of the dried sandwich structure (1) was vertically placed into the modified carbon nanotube solution (23), left to stand for 45 seconds, and then pulled out of the liquid surface at a speed of 100 mm / min. Then, it was placed in an oven and cured at 120°C for 2 hours. Next, two-thirds of the thickness of the structure was immersed in the modified carbon nanotube solution (23), and the above immersion-pulling and curing operations were repeated. Finally, the biomimetic sandwich structure 1 was completely immersed in the modified carbon nanotube solution (23), and the above immersion-pulling and curing operations were repeated to obtain the sandwich structure (1) covered with a gradient modified carbon nanotube film (2), thus completing the preparation of the submarine biomimetic heterogeneous protective shell (3).

9. The method for preparing a multi-dimensional stealth submarine biomimetic heterogeneous protective hull according to claim 8, characterized in that, Step 3 specifically includes the following steps: Step 3.1: Select Zn(NO3)2·6H2O with a purity ≥99%, weigh Zn(NO3)2·6H2O and deionized water in a mass ratio of 446:2991, and prepare a solution with a concentration of 0.5 mol / L. Place the prepared solution in a stirrer and stir continuously at a speed of 250 rpm. During the stirring process, slowly and continuously add 6 mol / L KOH solution. Stop stirring when the pH is adjusted to 12. Pour the resulting solution into a polytetrafluoroethylene box, fix it in an autoclave, and heat it evenly in an oven at 180℃ for 3 hours. After the reaction is completed, remove the autoclave from the oven and cool it to room temperature. Then place the reactants in a centrifuge tube and centrifuge at a speed of 4000 rpm for 5 minutes. After centrifugation, filter to obtain the precipitate. Anhydrous ethanol and deionized water were added to the precipitate in sequence, and then the precipitate was centrifuged three times at 4000 rpm to remove impurities. The final precipitate was placed in an oven and heated at 70°C until completely dry. Finally, the dried sample was ground into a fine powder to obtain ZnO. Step 3.2: First, mix 15.8 mol / L HNO3 and 18.4 mol / L H2SO4 solutions at a volume ratio of 1:

3. Then, select MWCNTs with an outer diameter range of 3-15 nm and disperse them in the mixed solution. Weigh the MWCNTs according to a mass ratio of 30:130.3 of MWCNTs to the mixed solution. Then, sonicate the mixture at 40℃ for 2.5 h. After sonication, add deionized water to the mixture for dilution. The volume ratio of the mixture to deionized water is 1:

4. Stir at 500 rpm for 1 h in a stirrer. After stirring, filter the mixture using a PTFE membrane and wash it with distilled water until the pH of the sample reaches 7. Finally, dry the sample in an oven at 80℃ for 6 h to obtain multi-walled carbon nanotubes with carboxylated surfaces, i.e., COOH-MWCNTs. Step 3.3: Weigh COOH-MWCNTs and ZnO at a mass ratio of 6:94, add them to anhydrous ethanol to prepare a 4 mg / mL solution, sonicate the mixed solution for 1 h, and then stir it in a stirrer at 250 rpm for 1 h to obtain a ZnO@MWCNTs solution; transfer the ZnO@MWCNTs solution to a polytetrafluoroethylene box, fix it in an autoclave, and heat it uniformly in an oven at 180 °C for 3 hours. Then remove the autoclave from the oven and cool it to room temperature. Pour the reaction mixture into a centrifuge tube, centrifuge at 4000 rpm for 5 minutes, filter to obtain the precipitate, put the final precipitate into an oven, and heat it at 70 °C until completely dry to obtain ZnO@MWCNTs particles (21). Step 3.4: PDMS and curing agent are mixed in a mass ratio of 10:1 and added to n-hexane solution to prepare a solution of 22 g / L. The solution is stirred at room temperature for 15 min to obtain PDMS solution (22). Then, ZnO@MWCNTs particles (21) are added to PDMS solution (22) in a mass ratio of 2:

11. The mixed solution is stirred at 400 rpm for 1 h to obtain modified carbon nanotube solution (23).

10. A multi-dimensional stealth biomimetic heterogeneous protective hull for submarines, characterized in that, It is prepared by the method as described in claim 9.

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