A multifunctional aircraft skin bionic heterogeneous structure and its preparation method

Abstract

The present invention discloses a multifunctional aircraft skin bionic heterogeneous structure and a preparation method thereof, belonging to the field of aerospace technology. Aiming at the problem that the traditional aircraft skin structure is difficult to synergistically achieve anti-impact, sound absorption and noise reduction, and electromagnetic shielding, the present invention breakthroughly designs a multifunctional composite skin protection structure, and realizes triple optimization of mechanical-acoustic-electromagnetic properties through the collaborative innovation of bionic architecture and functional materials. The present invention designs a bionic skeleton structure with outstanding mechanical properties based on the hierarchical annular structure of glass sponge skeleton and the hierarchical structure of femur, and combines it with modified polyurethane foam with excellent sound absorption performance and electromagnetic shielding performance to obtain a multifunctional heterogeneous structure with anti-impact, noise reduction and electromagnetic shielding.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace technology, and specifically 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 wing during operation. At the same time, external electromagnetic signals will affect the flight control systems (such as ailerons, elevators, etc.) at the wing, which will cause major safety accidents and serious physical hazards.

[0003] In terms of impact resistance, traditional wing structures mostly rely on metal skeletons 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 balance the lightweight requirements.

[0004] Sound absorption and noise reduction technologies mainly use porous materials or resonance cavity structures. Although they have good suppression effects on high-frequency noise, their low-frequency sound absorption efficiency is low, and the structure thickness needs to be increased to improve performance, resulting in prominent contradictions between weight and space utilization.

[0005] In terms of electromagnetic shielding, existing solutions mostly rely on metal foils, conductive coatings or surface coating materials. Although they can achieve a certain shielding effect, there are problems such as poor oxidation resistance and insufficient mechanical stability. Especially in vibration and corrosion environments, performance degradation is likely to occur, and it is difficult to be efficiently integrated with the sound absorption layer, resulting in scattered functional modules and poor adaptability.

[0006] In addition, existing technologies generally adopt a split design, and the functions of sound absorption, electromagnetic shielding and structural load-bearing are mutually separated. This not only increases the assembly complexity, but also limits the potential for multi-physical field collaborative optimization, and it is difficult to meet the comprehensive requirements of modern aviation for lightweight, multifunctional integration and long life.

[0007] In existing engineering practices or research, there has not yet been a skin integration solution that can simultaneously achieve high-efficiency electromagnetic shielding, broadband sound absorption coefficient and lightweight impact resistance. Developing advanced skin structure materials with multifunctional characteristics and lightweight impact resistance has become a key technical bottleneck restricting the development of a new generation of spacecraft.

[0008] Therefore, a multifunctional aircraft skin protection structure with impact resistance, sound absorption and noise reduction, and electromagnetic shielding is needed. 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 heterogeneous structure and a preparation method of the multifunctional aircraft skin bionic heterogeneous structure.

[0010] A preparation method of a multifunctional aircraft skin bionic heterogeneous structure is characterized by including the following steps:

[0011] Step 1: Extract the key features of the biological microtopography of the glass sponge skeleton and the femur and conduct bionic structure design, and complete the establishment of the bionic skeleton structure based on 3D modeling software;

[0012] 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;

[0013] 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;

[0014] 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.

[0015] Preferably, 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.

[0016] Preferably, the design method of the bionic vertical layered ring structure includes:

[0017] First, create two parallel rectangular bases with aligned ends, then draw a line segment passing through the midpoints of the two rectangular bases between the two rectangular bases, determine the midpoint of this line segment as the center point x, then 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 bases. Then stretch the figure composed of the rectangular bases and the two parallelograms into an X-shaped main structure;

[0018] Take the direction of the line segment passing through the midpoints of the two rectangular bases as the z-axis, the direction of stretching the rectangular bases as the x-axis, offset the z-axis 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 as the reference axis, and rotate it around the reference axis as the center axis in a circular array four times to form a cubic structure;

[0019] Then gradually add ribs and support columns to obtain the cell structure of the bionic vertical layered ring structure;

[0020] Finally, the bionic vertically layered annular structure unit 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 vertically layered annular structure.

[0021] Preferably, the design method of the bionic diagonal layered annular structure includes:

[0022] 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 in communication with the cross structure. 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;

[0023] Subsequently, the irregular circles generated during the construction of the cube are trimmed by means of stretch cutting to obtain the bionic diagonal layered annular structure unit structure;

[0024] Finally, the bionic diagonal layered annular structure unit 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 layered annular structure.

[0025] Preferably, the design method of the bionic BCC-FCC type hierarchical structure includes:

[0026] Create an FCC unit 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;

[0027] Subsequently, a BCC unit structure with a total size of a×a×a is established;

[0028] Then, the lattice structure and the BCC unit structure are combined by means of the intersection operation in Boolean operation to obtain the bionic BCC-FCC type hierarchical structure unit structure;

[0029] Finally, the bionic BCC-FCC type hierarchical structure unit 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.

[0030] Preferably, the design method of the bionic BCC-TPMS type hierarchical structure is:

[0031] Create a TPMS structure with dimensions of 0.5a×0.5a×0.5a, and a dot matrix structure with a linear array of 8×8×8. Subsequently, scale the total size of the dot matrix structure to a×a×a;

[0032] Subsequently, establish a BCC cell structure with a total size of a×a×a;

[0033] Then, combine the dot matrix structure and the BCC cell structure through the intersection operation in Boolean operations to obtain a bionic BCC-TPMS type hierarchical structure cell structure;

[0034] Finally, first array the bionic BCC-TPMS type hierarchical structure cell 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 BCC-TPMS type hierarchical structure.

[0035] Preferably, the method for polyurethane modification in step 3 includes the following steps:

[0036] Step 3.1, select Fe 3 O 4 particles with a size of 10 nm, add them to water to prepare a solution with a concentration of 16.6 mg / ml, and ultrasonically treat for 30 minutes to ensure uniform dispersion of the particles. Then, weigh a certain amount of polyvinyl alcohol and dissolve it in water to form a solution with a concentration of 20 mg / ml. Add the prepared polyvinyl alcohol solution to the Fe 3 O 4 dispersion, and the mass ratio of the two is 10:3;

[0037] Stir in a constant temperature water bath at 85° for two hours. During this process, add an appropriate amount of ammonia water with a concentration of 25% to make the pH value of the solution around 12;

[0038] After stirring, vortex the mixture for 30 minutes to ensure that the polyvinyl alcohol is uniformly coated on the surface of the Fe 3 O 4 particles. Then, centrifuge the mixture. The rotation speed of the tabletop centrifuge is set to 6000 rpm, and centrifuge for 8 minutes to obtain a black precipitate. Then, repeatedly wash the precipitate with 85° hot water to remove unreacted polyvinyl alcohol and other impurities. Finally, freeze-dry the washed precipitate to obtain polyvinyl alcohol magnetic sphere powder;

[0039] 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;

[0040] Add the washed carbon nanotubes to deionized water, add PVP dispersion, and ultrasonically disperse for 30 minutes to form a uniform carbon nanotube suspension with a concentration of 10 mg / mL;

[0041] 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.

[0042] Then, add the polyvinyl alcohol magnetic sphere powder particles prepared in Step 3.1 and the carbon nanotube suspension prepared in Step 3.2 respectively, so that their mass ratio to the solution is 10:5:70, and then stir evenly to form Component A.

[0043] Weigh an appropriate amount of toluene diisocyanate to form Component B, and the mass ratio between Component B and Component A is 7:3, obtaining a modified polyurethane solution.

[0044] Preferably, the specific method for preparing the aircraft skin bionic heterogeneous structure in Step 4 is as follows:

[0045] Use a nickel-titanium alloy powder to prepare a bionic skeleton by means of laser powder bed fusion printing equipment.

[0046] Then, put the printed bionic skeleton structure into a customized silicone mold.

[0047] Next, quickly stir the prepared modified polyurethane solution evenly, control the stirring time within 30 - 60 seconds, pour the mixed modified polyurethane solution into the silicone mold, so that the solution covers 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, wait for the modified polyurethane solution to foam, then dry it at room temperature for 2 hours, and take out the silicone mold.

[0048] Demold and take out the bionic skeleton wrapped with polyurethane foam filler to obtain the aircraft skin bionic heterogeneous structure.

[0049] A multifunctional aircraft skin bionic heterogeneous structure is prepared by using the preparation method of the above-mentioned multifunctional aircraft skin bionic heterogeneous structure.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] The four bionic structures designed in the present invention are relatively novel. Based on the energy dissipation principles of the glass sponge skeleton structure and the femur structure, characteristic structures are extracted to obtain bionic structures, which can achieve gradient transmission and efficient absorption of impact loads on the premise of ensuring structural lightweight, and significantly improve the anti-deformation ability and structural stability of the skin under dynamic impact.

[0052] The polyurethane modification method proposed in the present invention realizes the synergistic optimization of acoustic performance and electromagnetic performance. The unique porous resonance structure significantly enhances the broadband sound wave dissipation ability. Polyvinyl alcohol magnetic spheres (Fe 3 O4 (@PVA) Magnetic particles generate local mechanical resonance under acoustic wave excitation, enhancing the sound absorption ability.

[0053] A three-dimensional interpenetrating network based on carbon nanotubes constructs a high-density conductive path. Through microscopic topology optimization, multiple reflection interfaces are formed, enabling electromagnetic waves to experience tortuous propagation and continuous attenuation within the material.

[0054] Meanwhile, Fe 3 O 4 (@PVA) magnetic particles are embedded in the conductive network as nanoscale magnetic loss units. The redistribution of surface charges and the ferromagnetic resonance effect on their surfaces significantly enhance broadband electromagnetic energy absorption. The polyvinyl alcohol (PVA) coating layer not only improves the interfacial compatibility but also induces the heterogeneous interface polarization effect, achieving the dynamic matching of conductive loss and magnetic loss, and having excellent electromagnetic shielding performance.

[0055] The biomimetic heterogeneous structure of the aircraft skin proposed in this invention realizes the organic integration of impact resistance, sound absorption and noise reduction, and electromagnetic protection through the spatial matching design of the biomimetic mechanical load-bearing system and the multifunctional wave-absorbing material. The biomimetic 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 the three-dimensional conductive network in the modified polyurethane establishes multiple reflection-absorption paths for electromagnetic waves. This invention constructs a new generation of skin protection system that is lightweight, strong, and has multi-field adaptability, providing an innovative solution for the multifunctional protection requirements of aircraft under complex working conditions. Description of the Drawings

[0056] Figure 1 is the schematic diagram of this invention;

[0057] Figure 2 is the design flow chart of the biomimetic vertical layered annular structure;

[0058] Figure 3 is the design flow chart of the biomimetic diagonal layered annular structure;

[0059] Figure 4 is the design flow chart of the biomimetic BCC-FCC type hierarchical structure;

[0060] Figure 5 is the design flow chart of the biomimetic BCC-TPMS type hierarchical structure;

[0061] Figure 6 is the polyurethane modification flow chart;

[0062] Figure 7 is the preparation flow chart of the aircraft skin biomimetic heterogeneous structure;

[0063] In the figure: 1. Bionic skeleton; 11. Bionic vertically layered annular structure; 12. Bionic diagonally layered annular 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. Bionic heterogeneous structure of aircraft skin; 4. Laser powder bed fusion printing equipment; 5. Nickel-titanium alloy powder; 6. Silicone mold;

[0064] 111. X-shaped main structure; 112. Cubic frame structure; 113. Cellular structure of bionic vertically layered annular structure; 121. Central cross structure; 122. X-shaped structure; 123. Cubic shape structure; 124: Cellular structure of bionic diagonally layered annular structure; 131. FCC cellular structure; 132. FCC lattice structure; 133. BCC cellular structure; 134: Cellular structure of bionic BCC-FCC type hierarchical structure; 141. TPMS cellular structure; 142. TPMS lattice structure; 144. Cellular structure of bionic BCC-TPMS type hierarchical structure. Detailed implementation manners

[0065] The present invention will be further described below in conjunction with specific embodiments.

[0066] As Figure 1 shown, inspired by the biological microtopography of the glass sponge skeleton and femur, four types of bionic skeleton 1 structures as shown in Figures 2 - 5 are designed. The preparation method for combining the bionic skeleton 1 structure with the polyurethane foam filler 2 to produce the bionic heterogeneous structure 3 of the aircraft skin includes the following steps:

[0067] 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 1 structure based on 3D modeling software;

[0068] 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 made of metal material based on the selective laser melting technology;

[0069] Step 3: Prepare the polyvinyl alcohol magnetic sphere powder 21 and the carbon nanotube suspension 22, and then incorporate the two materials into the solution for preparing polyurethane to complete the modification of polyurethane, and obtain the modified polyurethane solution 23;

[0070] 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 height of the mold. After curing in a constant temperature water bath at 70 °C for 24 hours, then dry at room temperature for 2 hours, and demold to complete the preparation of the bionic heterogeneous structure 3 of the aircraft skin.

[0071] In Step 2 above, 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.

[0072] The bionic skeleton structure established in Step 1 is any one of the bionic vertical layered ring structure 11, the bionic diagonal layered ring structure 12, the bionic BCC-FCC type hierarchical structure 13, and the bionic BCC-TPMS type hierarchical structure 14.

[0073] All kinds of 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.

[0074] As Figure 2 shown, the design method of the bionic vertical layered ring structure 11 includes the following contents:

[0075] First, use SolidWorks software to create two rectangular bases with dimensions of a×h in the front view reference plane. The two rectangular bases are parallel to each other and aligned at both ends, and the distance between the two rectangular bases is a - 2h. Then, draw a line passing through the midpoints of the two rectangular bases between the two rectangular bases, determine the midpoint of this line as the center point x, and then establish two parallelograms. Both parallelograms are centered on the center point x and the two parallelograms form a symmetric X shape. The width of the parallelogram is h, and its two pairs of opposite sides coincide with the two adjacent sides of the two rectangular bases. The other two pairs of opposite sides form an angle α with the rectangular bases, and the distance between the outermost vertices of the parallelogram and the rectangular base is b. Then, stretch the figure composed of the rectangular base and the two parallelograms into an X-shaped main structure 111 with a thickness of m.

[0076] As Figure 2 shown, with the direction of the line passing through the midpoint of the rectangular base as the z-axis, the stretching direction of the thickness m of the X-shaped main structure 111 as the x-axis, and with the center point x as the base point, offset the z-axis by a distance of c1 along the x-axis direction as the first reference axis. Use the first reference axis as the central axis and array it 4 times along the circumferential direction to form a cubic frame structure 112.

[0077] Subsequently, reinforcing ribs 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.

[0078] 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) arranged. The contact surfaces of the upper and lower ends of the support column with the rectangular matrix are transition structures composed of half concentric rings. In the middle of the two transition structures, there are 9 concentric rings, and the center distance between adjacent concentric rings is (d + c) / 2. 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.

[0079] 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.

[0080] As Figure 3 shown, the design method of the bionic diagonal stratified annular structure 12 includes the following contents:

[0081] The design idea of the bionic diagonal stratified annular structure 12 is based on the face-centered lattice, and the pillar in the traditional face-centered lattice is replaced by a stratified structure composed of concentric circular beams.

[0082] 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 connected to the cross structure. Among them, the circular beams are concentric circular beams, with a large circle radius of R and a small circle radius of r.

[0083] Then, taking the central cross structure 121 as the center point, the circular beams of the same size are arrayed four times along the angular bisector direction of the cross structure of the central cross structure 121. Then, a frame with a size of a×a is constructed with the central cross structure 121 as the center point. The direction of the circular beam array is the diagonal of the frame. Subsequently, two lines tangent to the outer circle of the circular beam are introduced on the circular beams at the four vertices respectively. The direction of the lines is parallel to the angular bisector direction of the cross structure. Then, the two tangent lines, the frame, and the outer circle area of the circular beam are combined to form a closed area between the circular beam at the vertex and the frame, constituting the pointed corner part at the end of the circular beam. Finally, the obtained figure is stretched by a certain thickness to obtain a structure similar to Figure 3 the X-shaped structure 122.

[0084] Subsequently, taking the center point of the central cross structure 121 as the base point, the vertical direction of the cross structure of the central cross structure 121 is determined as the z-axis, the thickness stretching direction of the X-shaped structure 122 is determined as the x-axis. Taking the z-axis offset by a distance of c2 in the x-axis direction as the reference axis two, and taking the reference axis two as the central axis, it is arrayed 4 times in the circumferential direction. Taking the projection point of the base point projected on the reference axis two as the base point, the reference axis three is established in the y-axis direction. Subsequently, the X-shaped structure 122 is rotationally arrayed twice with the reference axis three as the center to construct the top and bottom surfaces of the cubic structure 123, and finally the cubic structure 123 is formed.

[0085] Subsequently, the irregular circles at the eight vertices of the cubic structure 123 are processed to construct circles with a radius of r. The circular beams of the additional structures generated by the interference of the rotational array at the eight vertices are trimmed, and the interior of the circular beams is stretch-cut with a circle with a radius of r to obtain the bionic diagonal hierarchical annular structure cell structure 124.

[0086] Finally, the bionic diagonal hierarchical annular structure cell structure 124 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 diagonal hierarchical annular structure 12.

[0087] As Figure 4 shown, the design method of the bionic BCC-FCC type hierarchical structure 13 includes the following contents:

[0088] The BCC-FCC type structure uses the common BCC structure as the framework. First, an FCC cell structure 131 with a total size of 0.5a×0.5a×0.5a is created with circular pillars with a diameter of 1.5h. Then, the FCC cell structure 131 is linearly arrayed into a 6×6×6 lattice structure. Subsequently, the total size of the lattice structure is scaled to a×a×a, and finally the FCC lattice structure 132 is formed.

[0089] Subsequently, a BCC cell structure 133 with a total size of a×a×a is established, and the diameter of the cylindrical pillars therein is 3h. Using the Boolean operation in SolidWorks and using the "common" feature therein, the two are combined to obtain the bionic BCC-FCC type hierarchical structure cell structure 134.

[0090] Finally, the bionic BCC-FCC type hierarchical structure cell structure 134 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 BCC-FCC type hierarchical structure 13.

[0091] As Figure 5As shown, the design method of the bionic BCC-TPMS hierarchical structure 14 includes the following:

[0092] Using the formula , perform CFD modeling in Matlab software to form a surface and export the stl file. Where c is the threshold constant used to control the relative density of the TPMS surface, and the range of c is [-2, 2], and x, y, and z are the three-dimensional coordinates of the point respectively.

[0093] Import the stl file finally generated by Matlab software into SolidWorks software. Use the "Convert to Mesh Solid" in the "Mesh Modeling" command to construct a TPMS unit cell structure 141 with a total size of 0.5a×0.5a×0.5a. Then linearly array the TPMS unit cell structure 141 into an 8×8×8 lattice structure, and then scale the total size of the lattice structure to a×a×a to finally obtain the TPMS lattice structure 142.

[0094] Subsequently, establish a BCC unit cell structure 133 with a total size of a×a×a, where the diameter of the cylindrical pillar is 3h, and perform a Boolean operation in SolidWorks to form a bionic BCC-TPMS hierarchical structure unit cell structure 144.

[0095] Finally, first array the bionic BCC-TPMS hierarchical structure unit cell structure 144 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 BCC-TPMS hierarchical structure 14.

[0096] As Figure 6 shown, the specific steps of the polyurethane modification in step 3 of the preparation method are as follows:

[0097] Step 3.1, select Fe 3 O 4 particles with a size of 10 nm and add them to water to prepare a solution with a concentration of 16.6 mg / ml, and ultrasonically process for 30 minutes to ensure uniform dispersion of the particles. Then weigh a certain amount of PVA and dissolve it in water to form a solution with a concentration of 20 mg / ml. Add the prepared PVA solution to the Fe 3 O 4 dispersion liquid, and 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 ammonia water with a concentration of 25% to make the pH value of the solution around 12. After stirring, vortex the mixture for 30 minutes to ensure that PVA is uniformly coated on Fe 3 O 4On the surface of the particles, the mixture was then centrifuged. The rotational speed of the bench centrifuge was set at 6000 rpm, and black precipitate was obtained after centrifugation for 8 minutes. Then the precipitate was repeatedly washed with hot water at 85 °C to remove unreacted PVA and other impurities. Finally, the washed precipitate was freeze-dried to obtain polyvinyl alcohol magnetic sphere powder 21.

[0098] 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 washed CNTs to deionized water, add PVP dispersion solution, and ultrasonically disperse for 30 minutes to form a uniform 10 mg / mL carbon nanotube suspension 22.

[0099] Step 3.3: Weigh an appropriate amount of polyether polyol, dibutyltin dilaurate, organosilicon stabilizer, and deionized water according to the mass ratio of 77:1:2:20, mix them evenly to form a solution, and then add the Fe 3 O 4 @PVA particles prepared in Step 3.1 and the carbon nanotube suspension 22 prepared in Step 3.2 to form a mass ratio of 10:5:70 with the solution, and then stir evenly 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.

[0100] As Figure 7 shown, the specific content of Step 4 is as follows:

[0101] Use a nickel-titanium alloy powder 5 with a laser powder bed fusion printing device 4 to prepare a bionic framework 1.

[0102] Then put the printed bionic framework 1 structure into a customized silicone mold 6.

[0103] Next, quickly stir the prepared modified polyurethane solution 23 evenly, with the stirring time controlled within 30 - 60 seconds. Pour the mixed modified polyurethane solution 23 into the silicone mold 6 so that the solution covers the bionic framework 1 but is lower than the height of the mold. Cure it in a constant temperature water bath at 70 °C for 24 hours, wait for the modified polyurethane solution 23 to foam, and then dry it at room temperature for 2 hours, and take out the silicone mold 6.

[0104] Demold and take out the bionic framework 1 wrapped with polyurethane foam filler 2 to obtain an aircraft skin bionic heterogeneous structure 3.

[0105] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. 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: The following steps are involved: 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.

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 annular structure, a bionic diagonal layered annular 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 annular structure comprises: 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 set as the z-axis, the direction in which the rectangular base is stretched is set as 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.

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 annular structure comprises: 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. The outermost circular beam is supplemented with a vertex structure, and the obtained figure is stretched to a certain thickness to obtain an X-shaped structure. Subsequently, with the center point of the central cross structure as the base point, the vertical direction of the cross structure of the central cross structure is set as the z-axis, the thickness stretching direction of the X-shaped structure is set as the x-axis, and an axis perpendicular to both the z-axis and the x-axis is set as the y-axis. Then, a cubic structure is formed by circular array; Subsequently, the irregular circles generated during the construction of the cube are trimmed by stretch cutting to obtain a bionic diagonal layered annular structure cell structure; Finally, the bionic diagonal layered annular structure cell structure is first arrayed three times along the x-axis, then the arrayed structure 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 layered annular 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 includes: 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. Subsequently, the total size of the lattice structure is scaled to a×a×a; Subsequently, 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 through the intersection operation in Boolean operation to obtain a bionic BCC-FCC type hierarchical structure cell structure; The three array directions in which the FCC cell structure is linearly arrayed into the lattice structure are set as the x-axis, y-axis, and z-axis of the bionic BCC-FCC type hierarchical structure cell structure; Finally, the bionic BCC-FCC type hierarchical structure cell structure is first arrayed three times along the x-axis, then the arrayed structure 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.

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 an 8×8×8 lattice structure. Subsequently, the total size of the lattice structure is scaled to a×a×a; Subsequently, 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 through the intersection operation in Boolean operation to obtain a bionic BCC-TPMS type hierarchical structure cell structure; The three array directions in which the TPMS structure is linearly arrayed into the lattice structure are set as the x-axis, y-axis, and z-axis of the bionic BCC-TPMS type hierarchical structure 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 into the customized silicone mold; Then, the prepared modified polyurethane solution was quickly stirred for 30-60 seconds, and the mixed modified polyurethane solution was poured into the silicone mold so that the solution was above the bionic skeleton but below the mold height, and cured in a constant temperature water bath at 70°C for 24 hours, and the modified polyurethane solution was allowed to foam, and then dried at room temperature for 2 hours, and the silicone mold was 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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