Multifunctional aircraft skin bionic heterostructure and preparation method thereof

Abstract

The invention discloses a multifunctional aircraft skin bionic heterostructure and a preparation method thereof, belongs to the technical field of aerospace, and aims to solve the problem that a traditional aircraft skin structure is difficult to synergistically realize impact resistance, sound absorption, noise reduction and electromagnetic shielding, and a multifunctional composite skin protection structure is designed in a breakthrough manner. Through collaborative innovation of a bionic framework and a functional material, triple optimization of mechanical-acoustic-electromagnetic characteristics is realized. A bionic skeleton structure with outstanding mechanical properties is obtained through a layered annular structure of a glass sponge skeleton and a hierarchical structure design of a thighbone, and the bionic skeleton structure is combined with modified polyurethane foam with excellent sound absorption performance and electromagnetic shielding performance to obtain a multifunctional heterostructure with impact resistance, noise reduction and electromagnetic shielding.

Description

Technical Field

[0001] The invention belongs to the field of aerospace technology, and in particular relates to a multifunctional aircraft skin bionic heterogeneous structure and a preparation method thereof. Background Art

[0002] Due to the working environment of the space shuttle itself, high-intensity aerodynamic noise and airflow impact will be generated at the wings during operation. At the same time, external electromagnetic signals will affect the flight control systems at the wings (such as ailerons, elevators, etc.), which will cause major safety accidents and serious physical harm.

[0003] In terms of impact resistance, traditional wing structures mostly rely on metal frames or single composite materials. Although they have certain mechanical strength, they are prone to stress concentration or fatigue damage under complex loads, and it is difficult to meet the requirements of lightweighting.

[0004] Sound absorption and noise reduction technology mainly uses porous materials or resonant cavity structures. Although it has a good effect on suppressing high-frequency noise, its low-frequency sound absorption efficiency is low, and the structure thickness needs to be increased to improve performance, resulting in a prominent contradiction between weight and space utilization.

[0005] In terms of electromagnetic shielding, existing solutions mostly rely on metal foil, conductive coating or surface coating materials. Although they can achieve a certain shielding effectiveness, they have problems such as poor oxidation resistance and insufficient mechanical stability. In particular, performance degradation is prone to occur under vibration and corrosion environments, and it is difficult to efficiently integrate with the sound absorption layer, resulting in dispersed functional modules and poor adaptability.

[0006] In addition, existing technologies generally adopt a split design, in which sound absorption, electromagnetic shielding and structural load-bearing functions are separated from each other, which not only increases the complexity of assembly, but also limits the potential for collaborative optimization of multiple physical fields. It is difficult to meet the comprehensive needs of modern aviation for lightweight, multi-functional integration and long life.

[0007] There is no integrated skin solution in existing engineering practice or research that can simultaneously achieve efficient electromagnetic shielding, wide-band sound absorption coefficient and lightweight impact resistance. The development of advanced skin structural materials with both multifunctional properties and lightweight impact resistance has become a key technical bottleneck restricting the development of the new generation of spacecraft.

[0008] Therefore, there is a need for a multifunctional aircraft skin protection structure with the characteristics of impact resistance, sound absorption and noise reduction, and electromagnetic shielding. Summary of the invention

[0009] In view of the above problems existing in the prior art, the present invention provides a multifunctional aircraft skin bionic heterostructure and a method for preparing the multifunctional aircraft skin bionic heterostructure.

[0010] A method for preparing a multifunctional aircraft skin bionic heterostructure, characterized by comprising the following steps: Step 1: Extract the key features of the biological microscopic morphology of the glass sponge skeleton and femur and design the bionic structure, and complete the establishment of the bionic skeleton structure based on 3D modeling software; Step 2: Convert the bionic skeleton structure established in step 1 into an STL format file and import it into the magics software, and prepare it into a bionic skeleton made of metal material based on the selective laser melting technology; Step 3: preparing polyvinyl alcohol magnetic sphere powder and carbon nanotube suspension, and then blending the two materials into the solution for preparing polyurethane to complete polyurethane modification and obtain a modified polyurethane solution; Step 4: Place the bionic skeleton prepared in step 2 into a customized mold, then quickly and evenly stir the modified polyurethane solution prepared in step 3, pour the mixed solution into the mold so that the solution covers the bionic skeleton but is lower than the mold height, and cure in a constant temperature water bath at 70°C for 24 hours, then dry at room temperature for 2 hours, demold, and complete the preparation of the aircraft skin bionic heterogeneous structure.

[0011] Preferably, the bionic skeleton structure established in step 1 is any one of a bionic vertical layered annular structure, a bionic diagonal layered annular structure, a bionic BCC-FCC type hierarchical structure and a bionic BCC-TPMS type hierarchical structure.

[0012] Preferably, the design method of the bionic vertical layered annular structure includes: First, two rectangular bases are created that are parallel to each other and aligned at both ends. Then, a line segment is drawn between the two rectangular bases through the midpoints of the two rectangular bases. The midpoint of the line segment is determined as the center point x. Then, two parallelograms are created. Both parallelograms take the center point x as the center point and the two parallelograms form a symmetrical X shape. There is a certain distance between the outermost vertices of the parallelograms and the rectangular base. Then, the figure composed of the rectangular base and the two parallelograms is stretched into an X-shaped main structure. The direction of the line segment passing through the midpoints of the two rectangular bases is the z-axis, the direction in which the rectangular bases are stretched is the x-axis, the z-axis line passing through the center of the outer surface of the X-shaped main structure is offset along the x-axis direction by a certain distance, and the offset z-axis line is used as the reference axis, and the axis circle array is rotated four times with the reference axis as the center to form a cubic structure; Then, reinforcing ribs and supporting columns are gradually added to obtain a bionic vertical layered annular structure cellular structure; Finally, the bionic vertical layered ring structure cell structure is arrayed three times along the x-axis, and then the structure obtained after the array is arrayed three times along the y-axis, and finally the structure obtained after the array again is arrayed three times along the z-axis direction to complete the creation of the bionic vertical layered ring structure.

[0013] Preferably, the design method of the bionic diagonal hierarchical annular structure includes: Construct a central cross structure, which consists of a cross structure and four 1 / 4 circular beams connecting the ends of the cross structure. The four circular beams are connected to the cross structure, and then circular beams of the same size are arrayed four times along the angular bisector direction of the cross structure, and the periphery of the outermost circular beam is supplemented into a vertex structure. Then, a cubic structure is formed by circular array; Subsequently, the irregular circles generated during the construction of the cube are trimmed by means of stretching and cutting to obtain the cellular structure of the bionic diagonal hierarchical annular structure; Finally, the cellular structure of the bionic diagonal hierarchical annular structure is first arrayed three times along the x-axis, then the structure obtained after the array is arrayed three times along the y-axis, and finally the structure obtained after the second array is arrayed three times along the z-axis to complete the creation of the bionic diagonal hierarchical annular structure.

[0014] Preferably, the design method of the bionic BCC-FCC type hierarchical structure includes: Create an FCC cellular structure with a total size of 0.5a×0.5a×0.5a and linearly array it into a 6×6×6 lattice structure. Subsequently, the total size of the lattice structure is scaled to a×a×a; Subsequently, a BCC cellular structure with a total size of a×a×a is established; Then, the lattice structure and the BCC cellular structure are combined by the intersection operation in Boolean operation to obtain the cellular structure of the bionic BCC-FCC type hierarchical structure; Finally, the cellular structure of the bionic BCC-FCC type hierarchical structure is first arrayed three times along the x-axis, then the structure obtained after the array is arrayed three times along the y-axis, and finally the structure obtained after the second array is arrayed three times along the z-axis to complete the creation of the bionic BCC-FCC type hierarchical structure.

[0015] Preferably, the design method of the bionic BCC-TPMS type hierarchical structure is: Create a TPMS structure with a size of 0.5a×0.5a×0.5a and linearly array it into an 8×8×8 lattice structure. Subsequently, the total size of the lattice structure is scaled to a×a×a; Subsequently, a BCC cellular structure with a total size of a×a×a is established; Then, the lattice structure and the BCC cellular structure are combined by the intersection operation in Boolean operation to obtain the cellular structure of the bionic BCC-TPMS type hierarchical structure; Finally, the bionic BCC-TPMS type hierarchical structure cell structure is arrayed three times along the x-axis, and then the structure obtained after the array is arrayed three times along the y-axis, and finally the structure obtained after the array is arrayed three times along the z-axis direction to complete the creation of the bionic BCC-TPMS type hierarchical structure.

[0016] Preferably, the polyurethane modification method in step 3 comprises the following steps: Step 3.1, select 10nm Fe3O4 particles and add them to water to prepare a 16.6mg / ml solution, and ultrasonicate for 30 minutes to ensure that the particles are evenly dispersed, then weigh a certain weight of polyvinyl alcohol and dissolve it in water to form a 20mg / ml solution, and add the prepared polyvinyl alcohol solution to the Fe3O4 dispersion, the mass ratio of the two is 10:3; Stir in a constant temperature water bath at 85° for two hours. During this process, add an appropriate amount of 25% ammonia water to make the pH value of the solution around 12. After stirring, the mixture was vortexed for 30 minutes to ensure that the polyvinyl alcohol was evenly coated on the surface of the Fe3O4 particles, and then the mixture was centrifuged. The speed of the desktop centrifuge was set to 6000 rpm. The black precipitate was obtained by centrifugation for 8 minutes. The precipitate was then repeatedly washed with 85° hot water to remove unreacted polyvinyl alcohol and other impurities. Finally, the washed precipitate was freeze-dried to obtain polyvinyl alcohol magnetic sphere powder. Step 3.2, weigh an appropriate amount of carbon nanotubes, and ultrasonically clean them with deionized water and ethanol for 30 minutes each to remove surface impurities; The cleaned carbon nanotubes were added to deionized water, and the PVP dispersion was added, and ultrasonic dispersion was performed for 30 minutes to form a uniform 10 mg / mL carbon nanotube suspension; Step 3.3, weigh appropriate amounts of polyether polyol, dibutyltin dilaurate, silicone stabilizer and deionized water in a mass ratio of 77:1:2:20, and mix them evenly to form a solution; Then, the polyvinyl alcohol magnetic sphere powder particles prepared in step 3.1 and the carbon nanotube suspension prepared in step 3.2 are added to the solution to form a mass ratio of 10:5:70, and then stirred to form component A; Then weigh an appropriate amount of toluene diisocyanate to form component B, with the mass ratio between component B and component A being 7:3, to obtain a modified polyurethane solution.

[0017] Preferably, the specific method for preparing the aircraft skin bionic heterostructure in step 4 is: The bionic skeleton was prepared using nickel-titanium alloy powder using laser powder bed fusion printing equipment; Then put the printed bionic skeleton structure into the customized silicone mold; Then, the prepared modified polyurethane solution is quickly stirred evenly, and the stirring time is controlled within 30-60 seconds. The mixed modified polyurethane solution is poured into the silicone mold so that the solution is above the bionic skeleton but lower than the mold height. It is cured in a constant temperature water bath at 70°C for 24 hours, and the modified polyurethane solution is waited for foaming, and then dried at room temperature for 2 hours, and the silicone mold is taken out; The bionic skeleton wrapped by the polyurethane foam filler is demoulded and taken out to obtain the aircraft skin bionic heterogeneous structure.

[0018] A multifunctional aircraft skin bionic heterostructure is prepared by adopting the preparation method of the multifunctional aircraft skin bionic heterostructure.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The four bionic structures designed in the present invention are relatively novel. Based on the energy dissipation principle of the glass sponge skeleton structure and the femoral structure, the characteristic structures are extracted to obtain the bionic structures. The gradient transmission and efficient absorption of impact loads can be achieved while ensuring the lightweight structure, which can significantly improve the deformation resistance and structural stability of the skin under dynamic impact.

[0020] The polyurethane modification method proposed in the present invention realizes the coordinated optimization of acoustic performance and electromagnetic performance. The unique porous resonance structure significantly enhances the broadband sound wave dissipation capability. The polyvinyl alcohol magnetic sphere (Fe3O4@PVA) magnetic particles generate local mechanical resonance under the excitation of sound waves, thereby enhancing the sound absorption capability.

[0021] A high-density conductive pathway is constructed based on the three-dimensional interpenetrating network of carbon nanotubes, and multiple reflection interfaces are formed through microscopic topological optimization, so that electromagnetic waves experience tortuous propagation and continuous attenuation inside the material.

[0022] At the same time, Fe3O4@PVA magnetic particles are embedded in the conductive network as nanoscale magnetic loss units, and their surface charge redistribution and ferromagnetic resonance effect significantly enhance the broadband electromagnetic energy absorption. The polyvinyl alcohol (PVA) coating layer not only improves the interface compatibility, but also induces the heterogeneous interface polarization effect, realizing the dynamic matching of conductive loss and magnetic loss, and has excellent electromagnetic shielding performance.

[0023] The aircraft skin bionic heterostructure proposed in the present invention realizes the organic integration of impact resistance, sound absorption and noise reduction, and electromagnetic protection through the spatial matching design of the bionic mechanical bearing system and the multifunctional absorbing material. The bionic metal skeleton embedded in the modified polyurethane foam can enhance the energy dissipation of low-frequency sound waves and improve the low-frequency sound absorption efficiency. The formation of a three-dimensional conductive network in the modified polyurethane establishes multiple reflection-absorption paths for electromagnetic waves. The present invention constructs a new generation of skin protection system that is lightweight, strong, and has multi-field adaptability, providing an innovative solution to the multifunctional protection needs of aircraft under complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the principle diagram of the present invention; Figure 2 Design a flow chart for the biomimetic vertical layered ring structure; Figure 3 Design a flow chart for the biomimetic diagonal layered ring structure; Figure 4 Design a flow chart for the biomimetic BCC-FCC type hierarchical structure; Figure 5 Design a flow chart for the bionic BCC-TPMS type hierarchical structure; Figure 6 This is a flow chart of polyurethane modification; Figure 7 Prepare a flow chart for aircraft skin biomimetic heterostructures; In the figure: 1. Bionic skeleton; 11. Bionic vertical layered ring structure; 12. Bionic diagonal layered ring structure; 13. Bionic BCC-FCC type hierarchical structure; 14. Bionic BCC-TPMS type hierarchical structure; 2. Polyurethane foam filler; 21. Polyvinyl alcohol magnetic sphere powder; 22. Carbon nanotube suspension; 23. Modified polyurethane solution; 3. Aircraft skin bionic heterogeneous structure; 4. Laser powder bed fusion printing equipment; 5. Nitinol powder; 6. Silicone mold; 111. X-shaped main structure; 112. Cube frame structure; 113. Bionic vertical layered ring structure cell structure; 121. Central field structure; 122. X-shaped structure; 123. Cube shape structure; 124: Bionic diagonal layered ring structure cell structure; 131. FCC cell structure; 132. FCC lattice structure; 133. BCC cell structure; 134: Bionic BCC-FCC type hierarchical structure cell structure; 141. TPMS cell structure; 142. TPMS lattice structure; 144. Bionic BCC-TPMS type hierarchical structure cell structure. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments.

[0026] like Figure 1 As shown in the figure, inspired by the biological microstructure of glass sponge skeleton and femur, the following Figure 2-Figure 5 The four bionic skeleton 1 structures shown in the figure, the preparation method of combining the bionic skeleton 1 structure with the polyurethane foam filler 2 to produce the aircraft skin bionic heterogeneous structure 3 includes the following steps: Step 1: Extract key features of the biological microscopic morphology of the glass sponge skeleton and femur and design the bionic structure, and complete the establishment of the bionic skeleton 1 structure based on 3D modeling software; Step 2: Convert the bionic skeleton 1 structure established in step 1 into an STL format file and import it into the magics software, and prepare the bionic skeleton 1 structure of metal material based on the selective laser melting technology; Step 3: preparing polyvinyl alcohol magnetic sphere powder 21 and carbon nanotube suspension 22, and then blending the two materials into a solution for preparing polyurethane to complete polyurethane modification and obtain a modified polyurethane solution 23; Step 4: Place the bionic skeleton 1 prepared in step 2 into a customized mold, then quickly and evenly stir the modified polyurethane solution 23 prepared in step 3, and pour the mixed solution into the mold so that the solution covers the bionic skeleton 1 but is lower than the mold height. After curing in a constant temperature water bath at 70°C for 24 hours, then drying at room temperature for 2 hours, demolding, and completing the preparation of the aircraft skin bionic heterogeneous structure 3.

[0027] In the above step 2, a laser powder bed fusion printing device 4 is used, and the printing parameters are: laser power 100W, scanning speed 600mm / s, scanning spacing 80um, layer thickness 30um, and the metal material used is nickel-titanium alloy.

[0028] The bionic skeleton structure established in step 1 is any one of a bionic vertical layered annular structure 11 , a bionic diagonal layered annular structure 12 , a bionic BCC-FCC type hierarchical structure 13 and a bionic BCC-TPMS type hierarchical structure 14 .

[0029] Various structures of the bionic skeleton 1 are established through 3D modeling software. In this embodiment, the design and establishment of various bionic skeleton 1 structures are demonstrated based on SolidWorks software.

[0030] like Figure 2 As shown, the design method of the bionic vertical layered ring structure 11 includes the following contents: First, use SolidWorks software to create two rectangular bases of a×h size in the front view reference plane. The two rectangular bases are parallel to each other, and the two ends are aligned. The distance between the two rectangular bases is a-2h. Then, a line segment passing through the midpoints of the two rectangular bases is made between the two rectangular bases, and the midpoint of the line segment is determined as the center point x. Then, two parallelograms are established. Both parallelograms take the center point x as the center point and the two parallelograms form a symmetrical X shape. The width of the parallelogram is h, and its two pairs of sides coincide with the two sides close to the two rectangular bases. The angle between the other two pairs of sides and the rectangular base is α, and the distance between the outermost vertex of the parallelogram and the rectangular base is b. Then, the figure composed of the rectangular base and the two parallelograms is stretched into an X-shaped main structure 111 with a thickness of m.

[0031] like Figure 2 Taking the direction of the line passing through the midpoint of the rectangular substrate as the z-axis, the stretching direction of the thickness m of the X-shaped main structure 111 as the x-axis, with the center point x as the base point, the z-axis offset by a distance c1 along the x-axis direction as the first reference axis, and using the first reference axis as the central axis to form a cubic frame structure 112 by circular array 4 times along the circumferential direction.

[0032] Subsequently, stiffeners with a width of h and a thickness of m are provided on the diagonals of the upper and lower surfaces of the cubic frame structure 112.

[0033] Subsequently, four support columns are provided on the four edges of the cubic frame structure 112 in the z-axis direction. Each support column is composed of a plurality of concentric rings with diameters d and c (d > c) respectively arranged. The contact surfaces of the upper and lower ends of the support column with the rectangular substrate are transition structures composed of half concentric rings. There are 9 concentric rings in the middle of the two transition structures, and the center distance between adjacent concentric rings is (d + c) / 2. And the thickness of the column formed by the ring structure is m. Thus, the construction of the bionic vertically stratified annular structure cell structure 113 is completed.

[0034] Finally, the bionic vertically stratified annular structure cell structure 113 is first arrayed three times along the x-axis, then the structure obtained after the array is arrayed three times along the y-axis, and finally the structure obtained after the second array is arrayed three times along the z-axis direction to complete the creation of the bionic vertically stratified annular structure 11.

[0035] As Figure 3 shown, the design method of the bionic diagonal stratified annular structure 12 includes the following content: The design idea of the bionic diagonal stratified annular structure 12 is based on the face-centered lattice, and a stratified structure composed of concentric circular beams is used to replace the struts in the traditional face-centered lattice.

[0036] First, a central cross structure 121 is constructed on the front view reference plane. The central cross structure 121 is composed of a cross structure with a width of f and a length of g and four 1 / 4 circular beams connecting the ends of the cross structure. The four circular beams are in communication with the cross structure. Among them, the circular beams are concentric circular beams, the radius of the large circle is R, and the radius of the small circle is r.

[0037] Then, taking the central cross-shaped structure 121 as the center point, use a circular beam array of the same size four times along the angular bisector direction of the cross-shaped structure of the central cross-shaped structure 121. Then, construct a frame with a size of a×a with the central cross-shaped structure 121 as the center point, where the direction of the circular beam array is the diagonal of the frame. Subsequently, introduce two lines tangent to the outer circle of the circular beam at the circular beams at the four vertices respectively. The direction of the lines is parallel to the angular bisector direction of the cross-shaped structure. Then, combine the two tangent lines, the frame, and the outer circle area of the circular beam to form a closed area between the circular beam at the vertex and the frame, constituting the pointed part at the end of the circular beam. Finally, stretch the obtained figure by a certain thickness to obtain a structure similar to the X-shaped structure 122 as shown in Figure 3 of the X-like structure 122.

[0038] Subsequently, taking the center point of the central cross-shaped structure 121 as the base point, determine the vertical direction of the cross-shaped structure of the central cross-shaped structure 121 as the z-axis, and the thickness stretching direction of the X-like structure 122 as the x-axis. Take the z-axis offset by a distance of c2 along the x-axis direction as the reference axis two. Taking the projection point of the base point projected on the reference axis two as the base point, establish the reference axis three along the y-axis direction. Subsequently, rotate and array the X-like structure 122 twice with the reference axis three as the center axis to construct the top and bottom surfaces of the cubic-shaped structure 123, and finally form the cubic-shaped structure 123.

[0039] Subsequently, process the irregular circles at the eight vertices of the cubic-shaped structure 123, construct a circle with a radius of r, and trim the circular beams of the additional structures generated due to the interference of the rotational array at the eight vertices. Stretch and cut the inside of the circular beam with a circle with a radius of r to obtain the bionic diagonal hierarchical annular structure cell structure 124.

[0040] Finally, first array the bionic diagonal hierarchical annular structure cell structure 124 three times along the x-axis, then array the structure obtained after the array three times along the y-axis, and finally array the structure obtained after the second array three times along the z-axis direction to complete the creation of the bionic diagonal hierarchical annular structure 12.

[0041] As shown in Figure 4 The design method of the bionic BCC-FCC type hierarchical structure 13 includes the following content: The BCC-FCC type structure uses the common BCC structure as the framework. First, create an FCC cell structure 131 with a total size of 0.5a×0.5a×0.5a using circular struts with a diameter of 1.5h. Then, linearly array the FCC cell structure 131 into a 6×6×6 lattice structure. Subsequently, scale the total size of the lattice structure to a×a×a to finally form the FCC lattice structure 132.

[0042] Then, a BCC cell structure 133 with a total size of a×a×a is established, in which the diameter of the cylindrical pillar is 3h. The Boolean operation in SolidWorks is used to combine the two using the "common" features to obtain a bionic BCC-FCC type hierarchical cell structure 134.

[0043] Finally, the bionic BCC-FCC type hierarchical structure cell structure 134 is arrayed three times along the x-axis, and then the structure obtained after the array is arrayed three times along the y-axis, and finally the structure obtained after the array is arrayed three times along the z-axis direction to complete the creation of the bionic BCC-FCC type hierarchical structure 13.

[0044] like Figure 5 As shown, the design method of the bionic BCC-TPMS type hierarchical structure 14 includes the following contents: Using the formula , CFD modeling is performed in Matlab software to form the surface and the stl file is exported. c is a threshold constant used to control the relative density of the TPMS surface. The range of c is [-2,2], and x, y and z are the three-dimensional coordinates of the point.

[0045] The stl file finally generated by the Matlab software is imported into the SolidWorks software, and the "Convert to Mesh Entity" in the "Mesh Modeling" command is used to construct a TPMS cell structure 141 with a total size of 0.5a×0.5a×0.5a. The TPMS cell structure 141 is then linearly arrayed into a 8×8×8 lattice structure, and the total size of the lattice structure is subsequently scaled to a×a×a, finally obtaining a TPMS lattice structure 142.

[0046] Then, a BCC cell structure 133 with a total size of a×a×a is established, in which the diameter of the cylindrical pillar is 3h, and Boolean operations are performed in SolidWorks to form a bionic BCC-TPMS type hierarchical cell structure 144.

[0047] Finally, the bionic BCC-TPMS type hierarchical structure cell structure 144 is arrayed three times along the x-axis, and then the structure obtained after the array is arrayed three times along the y-axis, and finally the structure obtained after the array is arrayed three times along the z-axis direction to complete the creation of the bionic BCC-TPMS type hierarchical structure 14.

[0048] like Figure 6 As shown, the specific steps of polyurethane modification in step 3 of the preparation method are as follows: Step 3.1, select 10nm Fe3O4 particles and add them to water to prepare a 16.6mg / ml solution, and ultrasonicate for 30 minutes to ensure that the particles are evenly dispersed, then weigh a certain weight of PVA and dissolve it in water to form a 20mg / ml solution, add the prepared PVA solution to the Fe3O4 dispersion, the mass ratio of the two is 10:3, and stir in a constant temperature water bath at 85° for two hours. During this process, add an appropriate amount of 25% ammonia water to make the pH value of the solution about 12. After stirring, vortex the mixture for 30 minutes to ensure that PVA is evenly coated on the surface of the Fe3O4 particles, and then centrifuge the mixture. The speed of the desktop centrifuge is set to 6000rpm. Centrifuge for 8 minutes to obtain a black precipitate, and then repeatedly wash the precipitate with 85° hot water to remove unreacted PVA and other impurities. Finally, freeze-dry the washed precipitate to obtain polyvinyl alcohol magnetic sphere powder 21.

[0049] Step 3.2, weigh an appropriate amount of carbon nanotubes (CNTs), and ultrasonically clean them with deionized water and ethanol for 30 minutes each to remove surface impurities. Add the cleaned CNTs into deionized water, add PVP dispersion, and ultrasonically disperse for 30 minutes to form a uniform 10 mg / mL carbon nanotube suspension22.

[0050] Step 3.3, weigh appropriate amounts of polyether polyol, dibutyltin dilaurate, silicone stabilizer and deionized water in a mass ratio of 77:1:2:20, mix well to form a solution, then add the Fe3O4@PVA particles prepared in step 3.1 and the carbon nanotube suspension 22 prepared in step 3.2 respectively to form a mass ratio of 10:5:70 with the solution, and then stir well to form component A; then weigh an appropriate amount of toluene diisocyanate (TDI) to form component B, and the mass ratio between component B and component A is 7:3 to obtain a modified polyurethane solution 23.

[0051] like Figure 7 As shown, the specific contents of step 4 are as follows: The bionic skeleton 1 is prepared using nickel-titanium alloy powder 5 using laser powder bed fusion printing equipment 4 .

[0052] The printed bionic skeleton 1 structure is then placed into the customized silicone mold 6.

[0053] Then, the prepared modified polyurethane solution 23 is quickly stirred evenly, and the stirring time is controlled within 30-60 seconds. The mixed modified polyurethane solution 23 is poured into the silicone mold 6 so that the solution covers the bionic skeleton 1 but is lower than the mold height. It is cured in a constant temperature water bath at 70°C for 24 hours, and the modified polyurethane solution 23 is waited for foaming, and then dried at room temperature for 2 hours, and the silicone mold 6 is taken out.

[0054] The bionic skeleton 1 wrapped by the polyurethane foam filler 2 is demoulded and taken out to obtain the aircraft skin bionic heterogeneous structure 3.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a multifunctional aircraft skin bionic heterostructure, characterized in that: It includes the following steps: Step 1: Extract the key features of the biological microtopography of the glass sponge skeleton and femur and conduct bionic structure design, and complete the establishment of the bionic skeleton structure based on 3D modeling software; Step 2: Convert the bionic skeleton structure established in Step 1 into an stl format file and import it into magics software, and prepare a bionic skeleton made of metal material based on selective laser melting technology; Step 3: Prepare polyvinyl alcohol magnetic sphere powder and carbon nanotube suspension, and then incorporate the two materials into the solution for preparing polyurethane to complete the modification of polyurethane and obtain a modified polyurethane solution; Step 4: Place the bionic skeleton prepared in Step 2 into a customized mold, then quickly and evenly stir the modified polyurethane solution prepared in Step 3, pour the mixed solution into the mold, so that the solution submerges the bionic skeleton but is lower than the height of the mold, cure it in a constant temperature water bath at 70°C for 24 hours, then dry it at room temperature for 2 hours, and demold to complete the preparation of the bionic heterogeneous structure of the aircraft skin.

2. The method for preparing a multifunctional aircraft skin bionic heterostructure according to claim 1, characterized in that: The bionic skeleton structure established in Step 1 is any one of a bionic vertical layered ring structure, a bionic diagonal layered ring structure, a bionic BCC-FCC type hierarchical structure, and a bionic BCC-TPMS type hierarchical structure.

3. The method for preparing a multifunctional aircraft skin bionic heterostructure according to claim 2, characterized in that: The design method of the bionic vertical layered ring structure includes: First, create two parallel rectangular substrates with aligned ends. Then, draw a line segment passing through the midpoints of the two rectangular substrates between them, and determine the midpoint of this line segment as the center point x. Subsequently, establish two parallelograms. Both parallelograms take the center point x as the center point, and the two parallelograms form a symmetric X shape, and there is a certain distance between the outermost vertices of the parallelograms and the rectangular substrates. Then, stretch the figure composed of the rectangular substrates and the two parallelograms into an X-shaped main structure; Take the direction of the line segment passing through the midpoints of the two rectangular substrates as the z-axis, the direction of stretching the rectangular substrates as the x-axis, offset the z-axis line passing through the center of the outer surface of the X-shaped main structure along the x-axis direction by a certain distance, and use the offset z-axis line as the reference axis, and rotate it four times in a circular array with the reference axis as the center rotation axis to form a cubic structure; Then gradually add reinforcing ribs and support columns to obtain the cell structure of the bionic vertical layered ring structure; Finally, first array the cell structure of the bionic vertical layered ring structure three times along the x-axis, then array the structure obtained after the array three times along the y-axis, and finally array the structure obtained after the second array three times along the z-axis direction to complete the creation of the bionic vertical layered ring structure.

4. The method for preparing a multifunctional aircraft skin bionic heterostructure according to claim 2, characterized in that: The design method of the bionic diagonal layered ring structure includes: Construct a central cross structure. The central cross structure consists of a cross structure and four 1 / 4 circular beams connecting the ends of the cross structure. The four circular beams are connected to the cross structure, and then circular beams of the same size are arrayed four times along the angle bisector direction of the cross structure, and the periphery of the outermost circular beam is supplemented into a vertex angle structure. Then, form a cubic shape structure through a circular array method; Then, the irregular circles generated in the process of constructing the cube are trimmed by stretching and cutting to obtain a bionic diagonal layered ring structure cell structure; Finally, the bionic diagonal layered ring structure cell structure is arrayed three times along the x-axis, and then the structure obtained after the array is arrayed three times along the y-axis, and finally the structure obtained after the array is arrayed three times along the z-axis direction to complete the creation of the bionic diagonal layered ring structure.

5. The method for preparing a multifunctional aircraft skin bionic heterostructure according to claim 2, characterized in that: The design method of the bionic BCC-FCC type hierarchical structure comprises: Create an FCC cell structure with a total size of 0.5a×0.5a×0.5a, and linearly array it into a 6×6×6 lattice structure, and then scale the total size of the lattice structure to a×a×a; Then a BCC cell structure with a total size of a×a×a is established; Then the lattice structure and the BCC cell structure are combined by the intersection operation in Boolean operation to obtain the bionic BCC-FCC type hierarchical cell structure; Finally, the bionic BCC-FCC type hierarchical structure cell structure is arrayed three times along the x-axis, and then the structure obtained after the array is arrayed three times along the y-axis, and finally the structure obtained after the array again is arrayed three times along the z-axis direction to complete the creation of the bionic BCC-FCC type hierarchical structure.

6. The method for preparing a multifunctional aircraft skin bionic heterostructure according to claim 2, characterized in that: The design method of the bionic BCC-TPMS type hierarchical structure is: Create a TPMS structure with a size of 0.5a×0.5a×0.5a, and linearly array it into a lattice structure of 8×8×8, and then scale the total size of the lattice structure to a×a×a; Then a BCC cell structure with a total size of a×a×a is established; Then, the lattice structure and the BCC cell structure are combined by the intersection operation in Boolean operation to obtain the bionic BCC-TPMS type hierarchical cell structure; Finally, the bionic BCC-TPMS type hierarchical structure cell structure is arrayed three times along the x-axis, and then the structure obtained after the array is arrayed three times along the y-axis, and finally the structure obtained after the array is arrayed three times along the z-axis direction to complete the creation of the bionic BCC-TPMS type hierarchical structure.

7. The method for preparing a multifunctional aircraft skin bionic heterostructure according to claim 1, characterized in that: The method for polyurethane modification in step 3 comprises the following steps: Step 3.1, select 10nm Fe3O4 particles and add them to water to prepare a 16.6mg / ml solution, and ultrasonicate for 30 minutes to ensure that the particles are evenly dispersed, then weigh a certain weight of polyvinyl alcohol and dissolve it in water to form a 20mg / ml solution, and add the prepared polyvinyl alcohol solution to the Fe3O4 dispersion, the mass ratio of the two is 10:3; Stir in a constant temperature water bath at 85° for two hours. During this process, add an appropriate amount of 25% ammonia water to make the pH value of the solution around 12. After stirring, the mixture was vortexed for 30 minutes to ensure that the polyvinyl alcohol was evenly coated on the surface of the Fe3O4 particles, and then the mixture was centrifuged. The speed of the desktop centrifuge was set to 6000 rpm. The black precipitate was obtained by centrifugation for 8 minutes. The precipitate was then repeatedly washed with 85° hot water to remove unreacted polyvinyl alcohol and other impurities. Finally, the washed precipitate was freeze-dried to obtain polyvinyl alcohol magnetic sphere powder. Step 3.2, weigh an appropriate amount of carbon nanotubes, and ultrasonically clean them with deionized water and ethanol for 30 minutes each to remove surface impurities; The cleaned carbon nanotubes were added to deionized water, and the PVP dispersion was added, and ultrasonic dispersion was performed for 30 minutes to form a uniform 10 mg / mL carbon nanotube suspension; Step 3.3, weigh appropriate amounts of polyether polyol, dibutyltin dilaurate, silicone stabilizer and deionized water in a mass ratio of 77:1:2:20, and mix them evenly to form a solution; Then, the polyvinyl alcohol magnetic sphere powder particles prepared in step 3.1 and the carbon nanotube suspension prepared in step 3.2 are added to the solution to form a mass ratio of 10:5:70, and then stirred to form component A; Then weigh an appropriate amount of toluene diisocyanate to form component B, with the mass ratio between component B and component A being 7:3, to obtain a modified polyurethane solution.

8. The method for preparing a multifunctional aircraft skin bionic heterostructure according to claim 1, characterized in that: The specific method for preparing the aircraft skin bionic heterostructure in step 4 is: The bionic skeleton was prepared using nickel-titanium alloy powder using laser powder bed fusion printing equipment; Then put the printed bionic skeleton structure into the customized silicone mold; Then, the prepared modified polyurethane solution is quickly stirred evenly, and the stirring time is controlled within 30-60 seconds. The mixed modified polyurethane solution is poured into the silicone mold so that the solution is above the bionic skeleton but lower than the mold height. It is cured in a constant temperature water bath at 70°C for 24 hours, and the modified polyurethane solution is waited for foaming, and then dried at room temperature for 2 hours, and the silicone mold is taken out; The bionic skeleton wrapped by the polyurethane foam filler is demoulded and taken out to obtain the aircraft skin bionic heterogeneous structure.

9. A multifunctional aircraft skin bionic heterostructure, characterized in that: The multifunctional aircraft skin bionic heterostructure is prepared by the preparation method of the multifunctional aircraft skin bionic heterostructure according to any one of claims 1 to 8.

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