Impact-resistant and heat-insulating aircraft nacelle bionic heterogeneous structure and preparation method thereof

Abstract

The application discloses an anti-impact and heat-insulating aircraft nacelle bionic heterogeneous structure and a preparation method thereof, and relates to the technical field of aerospace, which comprises the following steps: constructing a three-dimensional bionic skeleton structure, importing a Magics software, and preparing a nickel-titanium alloy bionic skeleton by adopting a selective laser melting technology; preparing a modified epoxy resin solution; and infiltrating the nickel-titanium alloy bionic skeleton to obtain a bionic heterogeneous structure. The skeleton prepared by the method can effectively guide the graded transmission of impact load, and can gradually absorb and disperse dynamic impact energy through a gradient pore, a ring support and a multi-path force flow redistribution mechanism, so that the anti-deformation capacity and overall structural stability of the aircraft nacelle under the impact of birds, hail or foreign matters are significantly enhanced. The bionic heterogeneous structure breaks through the limitation of the separated design of a traditional nacelle heat-insulating layer, a bearing layer and an outer covering layer, and realizes the high integration of multiple key performances such as anti-impact, fire resistance and heat insulation.

Description

Technical Field

[0001] This invention relates to the field of aerospace technology, specifically to a biomimetic heterostructure for an aircraft nacelle that is impact-resistant and heat-insulating, and its preparation method. Background Technology

[0002] As a crucial component of the engine, the aircraft nacelle must simultaneously withstand the high-temperature airflow from the engine exhaust, intense aerodynamic heating, and a complex atmospheric environment during flight. Especially under transonic and high-altitude flight conditions, the nacelle's outer wall temperature rises dramatically, and the internal structure may also encounter high-energy impact loads such as bird strikes, hail, and runway debris. In extreme environments, traditional metal structures or single composite materials often struggle to simultaneously achieve excellent impact resistance and reliable thermal insulation, making them prone to impact damage, thermal fatigue, structural deformation, and even failure.

[0003] Current research on impact-resistant structural materials for aircraft nacelles mainly focuses on metal alloy structures, fiber-reinforced resin matrix composites, and metal-composite sandwich and infill structures. Traditional metal structures often use materials such as aluminum alloys and titanium alloys, improving load-bearing capacity through local reinforcement, reinforcing rings, stiffeners, and multiple load-bearing frames. Composite material structures rely on the high specific strength and designable anisotropy of reinforcements such as carbon fiber and glass fiber, using layup angles, interlayer sequence, and local thickening designs to disperse and dissipate impact energy. Meanwhile, metal-composite sandwich structures and foam or honeycomb core filling structures are also used to improve the structure's buffering and energy absorption capacity, mitigating the transmission of impact loads to critical internal components.

[0004] However, overall, existing nacelle impact-resistant structural material systems still have several shortcomings. First, most designs rely on a single matrix or simple sandwich structure, making it difficult to balance stable mechanical response and residual load-bearing capacity under the coupled conditions of high-temperature jets, aerodynamic heating, and complex atmospheric environments. This makes them prone to fatigue damage, microcrack accumulation, and stiffness degradation under repeated impacts and thermal cycling. Second, metal structures are susceptible to localized plastic yielding and permanent deformation under high strain rate impacts, while composite material structures are extremely sensitive to defects at interlayer interfaces and near the impact point, significantly reducing their reliability and load-bearing redundancy during subsequent service. Third, multi-material composite structures such as metal-composite materials and multi-layer sandwich structures have complex interfaces and significant differences in thermal expansion and elastic modulus. Under thermo-mechanical coupled impact conditions, stress concentration is easily generated at the interfaces, inducing failure modes such as debonding and peeling. Existing structural material designs often treat impact resistance and thermal protection separately, lacking an integrated material and structural co-design method for "high-temperature + high-energy impact" conditions, making it difficult to fully address the safety and reliability requirements of next-generation high thrust-to-weight ratio engine nacelles in extreme environments.

[0005] Therefore, there is an urgent need to develop a multifunctional biomimetic heterogeneous nacelle structure that combines strong impact resistance with efficient flame retardancy and heat insulation, in order to overcome the key technical challenges of high thrust-to-weight ratio, high reliability and extreme environmental adaptability of next-generation aircraft. Summary of the Invention

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing an impact-resistant and heat-insulating biomimetic heterostructure for an aircraft nacelle, comprising the following steps:

[0007] Step 1: Construct a three-dimensional biomimetic skeleton structure using 3D modeling software;

[0008] Step 2: Convert the three-dimensional bionic skeleton structure into an STL file and import it into Magics software. Use selective laser melting technology to prepare a nickel-titanium alloy bionic skeleton that corresponds to the shape and size of the nacelle structure.

[0009] Step 3: Prepare a modified epoxy resin solution using MXene hybrid flame retardants CHS@M and CoP@M and intumescent flame retardant reed PRM;

[0010] Step 4: Place the nickel-titanium alloy biomimetic skeleton obtained in Step 2 into a sealed mold customized according to the nacelle structure dimensions, ensuring that the skeleton is centered and fixed to the mold wall. Slowly pour in the modified epoxy resin solution prepared in Step 3 until the nickel-titanium alloy biomimetic skeleton is completely wetted. Then place the sealed mold in a vacuum drying oven for 10-20 minutes of vacuum degassing treatment to remove air bubbles from the solution. After degassing, a staged curing process is used to obtain the biomimetic heterostructure.

[0011] The three-dimensional biomimetic skeleton structure in step 1 is a biomimetic bird bone structure based on B-splines, a biomimetic osseointegrated structure, or a biomimetic hybrid TPMS structure; among them, the design steps of the biomimetic bird bone structure based on B-splines are as follows:

[0012] First, draw a square with side length 'a' on the front reference plane. Take the center point 'o' of square 1 as the origin. Let the straight line passing through 'o' and perpendicular to the front reference plane be the X-axis, the horizontal line passing through 'o' be the Y-axis, and the vertical line passing through 'o' be the Z-axis. Generate square 2 equidistant entities within square 1 with a spacing of 'h'. Then, use a B-spline to draw a central curve that is symmetrical about 'o'. The curve starts from point A, located to the left of the upper edge of square 2 and at a distance 'p' from the Z-axis, curves inward, passes through 'o', and reaches point D, located to the right of the lower edge of square 2 and at a distance 'p' from the Z-axis. Subsequently, use an offset entity to offset both sides of this central curve equidistantly by 'h / 2' to obtain a strip profile with a bandwidth of 'h'. Then, mirror the strip profile with the Z-axis as the axis of symmetry. Finally, stretch the graphic composed of square 1, square 2, and the two strip profiles along the X-axis to form a B-spline main structure with a thickness of 'm'.

[0013] Create a reference axis 1 parallel to the Z-axis at a distance a / 2 offset in the positive direction of the X-axis. Rotate the B-spline main structure around the reference axis 1 with an array angle of 90° to generate a total of 4 solids, resulting in a cube-shaped line frame structure.

[0014] Reinforcing ribs are created on the upper and lower faces of the cubic linear frame structure. The shape of the reinforcing ribs is the same as the strip outline. The width of the reinforcing ribs is h and the thickness is m, thus obtaining the biomimetic bird bone cell structure.

[0015] Finally, the biomimetic bird bone cell structure was arrayed in three dimensions along the X-axis, Y-axis, and Z-axis respectively. Multiple biomimetic bird bone cell structures distributed in a three-dimensional grid array together formed a biomimetic bird bone structure based on B-splines.

[0016] As a preferred design approach, the steps for a biomimetic osseointegrated structure are as follows:

[0017] First, create a cube line frame structure two that is identical to the cube line frame structure. Then, draw four sets of concentric circles with the vertices of the four edges parallel to the Z-axis as the centers. Each set of concentric circles includes two circles with radii r1 and r2 respectively. Extrude to create four concentric circle support columns. The thickness of the concentric circle support columns is m = r2 - r1, thus obtaining the interwoven spiral unit structure.

[0018] On the upper and lower faces of the interwoven spiral unit structure, create two reinforcing ribs with a width of h and a thickness of m along their respective diagonals. Both ends of the two reinforcing ribs extend to the outer side of the interwoven spiral unit structure. Using the intersection of the diagonals as the center, draw a circle with a diameter of r2 and extrude it into a circular plate with a thickness of m. Then, using the intersection of the diagonals as the center, draw a circle with a diameter of r1 and extrude it to cut it off, thus creating a concentric ring structure at the intersection of the two reinforcing ribs. Then, connect the endpoints of the two reinforcing ribs on the lower end face of the interwoven spiral unit structure to form a square path with a side length of k, and a rectangle with a width of b and a thickness of t. The cross-section is stretched along a square path to form a closed lower square frame. The upper surface of the interwoven spiral unit structure is stretched in the same way to form an upper square frame that is coaxially aligned with the lower square frame, and k=1.5a. Then, with the four vertices of the square path on the lower surface of the interwoven spiral unit structure as the center, four sets of concentric circles are drawn. Each set of concentric circles includes two circles with radii R1 and R2 respectively. This creates four concentric circular support columns to connect the upper and lower square frames. The wall thickness of the concentric circular support columns is m2=R1-R2, thus completing the creation of the biomimetic bone-spider web support unit structure.

[0019] A local coordinate system is established within the unit plane of the biomimetic fibrous bone-spider web support unit structure. The unit plane is the yz plane passing through the geometric center of the biomimetic fibrous bone-spider web support unit structure and whose normal direction is consistent with the global X-axis. The local coordinate system includes a y-axis and a z-axis, where the y-axis is parallel to the global Y-axis and the z-axis is parallel to the global Z-axis. The origin of the local coordinate system is the geometric center of the biomimetic fibrous bone-spider web support unit structure. The center curve 2 is defined according to the following formula:

[0020] ;

[0021] Where n>2, Z=a / 2-b, [0.28a, 0.36a], b > 0; and by offsetting ±h / 2 in the normal direction on both sides of the central curve, a boundary curve with bandwidth h is obtained:

[0022] ;

[0023] in, Let be the unit normal vector of the center curve 2. These represent the two boundary curves obtained by offsetting h / 2 along the positive and negative normal directions, respectively;

[0024] A strip-shaped entity with a thickness of m is generated along the thickness direction. Then, the strip-shaped entity is arranged in a circular array with a rotation axis of 90° around the geometric center of the biomimetic bone-spider web support unit structure, thus generating a total of 4 entities and completing the construction of the biomimetic bone-spider web fusion cell structure.

[0025] Finally, the biomimetic bone fusion cell structure was arrayed in three dimensions along the X-axis, Y-axis, and Z-axis respectively. Multiple biomimetic bone fusion cell structures distributed in a three-dimensional grid array together constitute the biomimetic bone fusion structure.

[0026] As a preferred design approach, the steps for a biomimetic hybrid TPMS structure are as follows:

[0027] In the cube [0, A 3D mesh is created within the [mesh], with the cell size set to 'a'. Physical coordinates are mapped to dimensionless coordinates using a uniform periodic scaling method.

[0028] , , ;

[0029] Ensure that the cell sizes of the two types of units are consistent;

[0030] Based on this, implicit functions of Schwarz surface and implicit functions of Diamond surface are used:

[0031] ,

[0032] ,

[0033] ,

[0034] ,

[0035] ,

[0036] ;

[0037] in For the implicit functions of the Schwarz surface, (These are the equivalent constants) For the implicit functions of the Diamond surface, are the equivalent constants;

[0038] Schwarz cell structure and Diamond cell structure were obtained, and then the Schwarz cell structure and Diamond cell structure were arrayed in three dimensions. Both cell structures were arrayed twice along the X-axis, Y-axis and Z-axis respectively, so as to obtain Schwarz cell structure and Diamond cell structure with size of 3a×3a×3a.

[0039] The Schwarz and Diamond cell structures were imported into the Boolean operation module and the intersection operation was performed to obtain the Diamond-Schwarz hybrid Boolean cell, thus constructing a 3a×3a×3a biomimetic hybrid TPMS cell structure.

[0040] Finally, the biomimetic hybrid TPMS cell structure was arrayed in three dimensions along the X-axis, Y-axis, and Z-axis respectively. Multiple biomimetic hybrid TPMS cell structures distributed in a three-dimensional grid array together constitute the biomimetic hybrid TPMS structure.

[0041] As a preferred option, step 3 specifically involves:

[0042] Step 3.1: Prepare CHS@M powder. Disperse 0.20 g of monolayer MXene solid ultrasonically in 200 mL of anhydrous ethanol to obtain an MXene dispersion. Dissolve 1 mmol of CaCl2 in 100 mL of ethanol, add 130 mL of triethylamine, stir at room temperature for 30 min, then pour into the MXene dispersion and continue stirring for 1 h to obtain a mixed system. Prepare 100 mL of 0.01 mol / L NaSnO3 aqueous solution and add it dropwise to the mixed system at a rate of 1 mL / min. React at room temperature and allow to stand overnight. The resulting product is centrifuged, washed with deionized water and ethanol, and finally vacuum dried at 60 °C to obtain CHS@M powder.

[0043] Step 3.2: Prepare CoP@M nanosheets. Weigh 3 mmol of CoSO4·7H2O, 2 mmol of Na2HPO4·12H2O, 1 mmol of SDBS, and 0.1 mol of urea and dissolve them in 100 mL of deionized water. React the solution in a microwave reactor at 95 °C and 900 W. CoP precipitate is generated in the reaction solution. Then, MXene is added to the reaction solution and in-situ loading reaction is carried out under microwave conditions. The product is centrifuged, washed with deionized water, and finally dried under vacuum at 60 °C to obtain CoP@M nanosheets.

[0044] Step 3.3: Prepare expanded reed flame retardant PRM powder. Soak reed powder in 20% NaOH solution for 24 hours, centrifuge and filter, wash repeatedly with deionized water to remove alkali, dry at 180℃, then pulverize and pass through a 200-mesh sieve to obtain modified reed powder. Weigh 1g of modified reed powder into a three-necked flask, add 100mL of deionized water, and reflux and stir for 15min under 80℃ oil bath conditions to disperse it evenly, obtaining AR dispersion. Separately, dissolve 3g of dicyandiamide in 50mL of deionized water and slowly pour it into AR dispersion, reflux at 80℃ for 15min, then add 70wt% phytic acid solution containing 6g of phytic acid, reflux again at 80℃ for 15min, cool to room temperature, centrifuge and filter, wash with deionized water, and finally dry in an 80℃ forced-air drying oven to constant weight to obtain expanded reed flame retardant PRM powder.

[0045] Step 3.4: CHS@M powder, CoP@M nanosheets, and expanded reed flame retardant PRM powder are added to epoxy resin, wherein the epoxy resin is 100 parts by weight, CHS@M powder is 0.5-2 parts by weight, CoP@M nanosheets are 0.5-2 parts by weight, and expanded reed flame retardant PRM powder is 6-12 parts by weight. The modified epoxy resin solution is prepared by stirring-ultrasound-vacuum defoaming-molding curing process.

[0046] The present invention also provides a biomimetic heterostructure for an aircraft nacelle that is impact-resistant and heat-insulating, which is prepared by the method described above.

[0047] The present invention has the following beneficial effects:

[0048] This invention designs three types of biomimetic structures. By extracting key features of biological micromorphology such as the three-dimensional porous network of coral, the lightweight hollow gradient pore characteristics of bird bone, and the radial radiation and spiral winding configuration of spider web, a three-dimensional biomimetic skeleton structure with multi-scale energy dissipation capability is constructed. This structure can effectively guide the graded transmission of impact loads and absorb and disperse dynamic impact energy step by step through gradient pores, circumferential support, and multi-path force flow redistribution mechanisms. This significantly enhances the deformation resistance and overall structural stability of aircraft nacelles under bird strike, hail, or foreign object impact scenarios.

[0049] This invention introduces MXene hybrid flame retardants (CHS@M, CoP@M) and intumescent flame-retardant reed (PRM) into a modified epoxy resin composite system, constructing a highly efficient and synergistic flame-retardant system. This system endows the material with excellent flame retardancy and thermal stability through multiple mechanisms such as carbon layer protection and catalytic carbonization, maintaining structural integrity under high-temperature airflow, aerodynamic heating, and repeated thermal cycling conditions. The modified epoxy matrix, combined with the air chambers within the three-dimensional biomimetic skeleton structure, forms a highly efficient thermal barrier path, effectively inhibiting the transfer of external high temperatures into the nacelle and significantly reducing the thermal load on the engine nacelle in extreme service environments.

[0050] This invention employs selective laser melting technology to fabricate a high-performance nickel-titanium alloy biomimetic skeleton. A vacuum-assisted impregnation and staged temperature-curing process are used to achieve a dense bond between the nickel-titanium alloy biomimetic skeleton and a modified epoxy resin solution, ensuring uniform interface quality and stable stress distribution within complex curved structures. This biomimetic heterogeneous structure overcomes the limitations of traditional separate designs for the nacelle insulation layer, load-bearing layer, and outer cladding layer, achieving a high degree of integration of key performance characteristics such as impact resistance and flame retardancy. The resulting high-strength, heat-resistant, and impact-resistant three-dimensional biomimetic nacelle protection system can provide more reliable structural safety for next-generation high thrust-to-weight ratio aircraft in extreme service environments, demonstrating significant engineering application value and promising prospects for widespread adoption. Attached Figure Description

[0051] Figure 1 This is a schematic diagram illustrating the overall principle of the present invention;

[0052] Figure 2 This is a schematic diagram of the design process of the biomimetic bird bone structure based on B-splines in this invention.

[0053] Figure 3 This is a schematic diagram illustrating the design process of the biomimetic bone fusion structure in this invention;

[0054] Figure 4 This is a schematic diagram illustrating the design process of the biomimetic hybrid TPMS structure in this invention;

[0055] Figure 5 This is a schematic diagram of the process for preparing the modified epoxy resin solution in this invention;

[0056] Figure 6 This is a schematic diagram illustrating the preparation process of the biomimetic skeleton structure-modified epoxy resin multifunctional heterostructure in this invention.

[0057] In the figure: 1, 3D biomimetic skeleton structure; 11, B-spline-based biomimetic bird bone structure; 12, biomimetic osseointegrated structure; 13, biomimetic hybrid TPMS cell structure; 111, B-spline main structure; 112, cubic line frame structure; 113, biomimetic bird bone cell structure; 122, cubic line frame structure II; 123, interwoven spiral unit structure; 124, biomimetic osseointegrated-spider web support unit structure; 125, biomimetic osseointegrated cell structure; 31, Schwarz cell structure; 132, Diamond cell structure; 133, Schwarz unit cell structure; 134, Diamond unit cell structure; 21, CHS@M powder; 22, CoP@M nanosheets; 23, expanded reed flame retardant PRM powder; 24, modified epoxy resin solution; 3, biomimetic skeleton structure - modified epoxy resin multifunctional heterostructure; 4, 3D printing equipment; 5, nickel-titanium powder; 6, sealing mold. Detailed Implementation

[0058] 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.

[0059] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0060] Embodiments of the present invention:

[0061] like Figures 1 to 6 As shown, a method for fabricating a biomimetic heterostructure for an aircraft nacelle that is impact-resistant and heat-insulating is described. This method extracts key features of biological micromorphology, such as the three-dimensional porous network structure of coral skeleton microstructure, the lightweight hollow gradient porosity of bird bone, and the radial radiation and helical winding synergistic configuration of spider web. Through biomimetic fusion and structural optimization design, a composite biomimetic skeleton with high specific stiffness and excellent energy dissipation capacity is constructed, including the following steps:

[0062] Step 1: Based on 3D modeling software, complete the accurate modeling of the biomimetic unit structure (biomimetic bird bone cell structure 113, biomimetic bone fusion cell structure 125, biomimetic hybrid TPMS cell structure 13), arrange the biomimetic unit structure in a three-dimensional array along the X-axis, Y-axis and Z-axis, and construct a three-dimensional biomimetic skeleton structure 1 (biomimetic bird bone structure 11, biomimetic bone fusion structure 12 or biomimetic hybrid TPMS structure based on B-spline) with multi-scale synergistic effect and multi-functional integration characteristics.

[0063] Step 2: Convert the three-dimensional bionic skeleton structure 1 into an STL file and import it into Magics software. Use selective laser melting technology to prepare a nickel-titanium alloy bionic skeleton that corresponds to the shape and size of the nacelle structure.

[0064] Step 3: Prepare modified epoxy resin solution 24 using MXene hybrid flame retardants (CHS@M, CoP@M) and intumescent flame retardant reed (PRM);

[0065] Step 4: Place the nickel-titanium alloy biomimetic skeleton obtained in Step 2 into a sealed mold 6 customized according to the nacelle structure dimensions, ensuring that the skeleton is centered and fixed to the mold wall. Slowly pour in the modified epoxy resin solution 24 prepared in Step 3 until the nickel-titanium alloy biomimetic skeleton is completely wetted. Then place the sealed mold 6 in a vacuum drying oven for 10-20 minutes of vacuum degassing treatment to remove air bubbles in the solution and avoid interface defects. After degassing, a staged curing process is adopted to fully cross-link and cure the resin, resulting in a densely bonded biomimetic skeleton structure with excellent mechanical and flame-retardant properties—the modified epoxy resin multifunctional heterostructure 3, i.e., the biomimetic heterostructure.

[0066] The biomimetic unit structure in step 1 includes a biomimetic bird bone structure 11 based on B-splines, a biomimetic bone fusion structure 12, and a biomimetic hybrid TPMS structure 13.

[0067] Among them, such as Figure 2 As shown, the design steps of the biomimetic bird bone structure 11 based on B-splines are as follows:

[0068] First, draw a square with side length a on the front reference plane. Take the center point o of square one as the origin, and denote the straight line passing through o and perpendicular to the front reference plane as the X-axis, the horizontal line passing through o as the Y-axis, and the vertical line passing through o as the Z-axis. Generate square two equidistant entities within square one with a spacing of h. Then, use B-splines to draw a central curve that is symmetrical about o. The curve starts from point A, which is located to the left of the upper edge of square two and is a distance p from the Z-axis, bends inward, passes through o, and reaches point D, which is located to the right of the lower edge of square two and is a distance p from the Z-axis. Subsequently, use offset entities to offset both sides of this central curve equidistantly by h / 2 to obtain a strip contour with a bandwidth of h. Then, mirror the strip contour with the Z-axis as the axis of symmetry. Finally, stretch the graphic composed of square one, square two, and the two strip contours along the X-axis to form a B-spline main structure 111 with a thickness of m.

[0069] Create a reference axis parallel to the Z axis at a distance a / 2 offset in the positive direction of the X axis. Rotate the B-spline main structure 111 around the reference axis with an array angle of 90° to generate a total of 4 entities, resulting in a cube line frame structure 112.

[0070] Reinforcing ribs are created on the upper and lower faces of the cubic linear frame structure 112. The design method of the reinforcing ribs is the same as that of the strip profile, forming a strip area with a width of h and a stretching thickness of m along a preset path. The reinforcing ribs are smoothly connected and fitted to the adjacent cubic frame members to obtain the biomimetic bird bone cell structure 113.

[0071] Finally, the biomimetic bird bone cell structure 113 is arrayed in three dimensions along the X-axis, Y-axis and Z-axis respectively. Multiple biomimetic bird bone cell structures 113 together form a biomimetic bird bone structure 11 based on B-splines.

[0072] like Figure 3 As shown, the design steps of the biomimetic bone fusion structure 12 are as follows:

[0073] First, create a cube line frame structure 122 that is identical to the cube line frame structure 112. Then, draw four sets of concentric circles with the vertices of the four edges parallel to the Z-axis as the centers. Each set of concentric circles includes two circles with radii r1 and r2 respectively. Extrude to create four concentric circle support columns with a thickness of m = r2 - r1, thus obtaining the interwoven spiral unit structure 123.

[0074] On the upper and lower surfaces of the interwoven spiral unit structure 123, two reinforcing ribs with a width of h and a thickness of m are created along their respective diagonals (two intersecting reinforcing ribs are created on both the upper and lower surfaces of the interwoven spiral unit structure 123). Both ends of each reinforcing rib extend to the outer side of the interwoven spiral unit structure 123. Using the intersection of the diagonals as the center, a circle with a diameter of r2 is drawn and extruded into a circular plate with a thickness of m. Then, using the intersection of the diagonals as the center, a circle with a diameter of r1 is drawn and extruded to cut off, thus creating a concentric ring structure at the intersection of the reinforcing ribs. Then, the endpoints of the two reinforcing ribs are connected within the lower end face of the interwoven spiral unit structure 123 to form a square with a side length of k. A rectangular cross-section with width b and thickness t is stretched along the path to form a closed lower square frame. The upper surface of the interwoven spiral unit structure 123 is stretched in the same way to form an upper square frame that is coaxially aligned with the lower square frame, and k=1.5a. Then, with the four vertices of the square path on the lower surface of the interwoven spiral unit structure 123 as the center, four sets of concentric circles are drawn. Each set of concentric circles includes two circles with radii R1 and R2, thereby stretching to create four concentric circular support columns II to connect the upper square frame and the lower square frame. The wall thickness of the concentric circular support columns II is m2=R1-R2, thus completing the creation of the biomimetic bone-spider web support unit structure 124.

[0075] A local coordinate system is established within the unit plane of the biomimetic fibrous bone-spider web support unit structure 124. The unit plane is the yz plane passing through the geometric center of the biomimetic fibrous bone-spider web support unit structure 124 and whose normal is consistent with the global X-axis. The local coordinate system includes a y-axis and a z-axis, where the y-axis is parallel to the global Y-axis and the z-axis is parallel to the global Z-axis. The origin of the local coordinate system is the geometric center of the biomimetic fibrous bone-spider web support unit structure 124. The center curve 2 is defined according to the following formula:

[0076] ;

[0077] Where n>2, Z=a / 2-b, [0.28a, 0.36a], b > 0; and by offsetting ±h / 2 in the normal direction on both sides of the central curve, a boundary curve with bandwidth h is obtained:

[0078] ;

[0079] in, Let be the unit normal vector of the center curve 2. These represent the two boundary curves obtained by offsetting h / 2 along the positive and negative normal directions, respectively;

[0080] Next, a strip-shaped entity with a thickness of m is generated along the thickness direction. Then, the strip-shaped entity is arranged in a circular array with a rotation axis of 90° around the straight line passing through the geometric center of the biomimetic bone-spider web support unit structure 124 and parallel to the Z-axis. A total of 4 entities are generated. The strip-shaped entities are connected to the base frame in a tangential continuous manner at the endpoints, thus completing the construction of the biomimetic bone-spider web fusion cell structure 125.

[0081] Finally, the biomimetic bone fusion cell structure 125 is arrayed in three dimensions along the X-axis, Y-axis and Z-axis respectively. Multiple biomimetic bone fusion cell structures 125 together form the biomimetic bone fusion structure 12.

[0082] like Figure 4 As shown, the design steps of the biomimetic hybrid TPMS structure are as follows:

[0083] In the cube [0, A 3D mesh is created within the mesh, with a cell size of 'a'. Physical coordinates are mapped to dimensionless coordinates using a uniform periodic scaling method.

[0084] , , ;

[0085] Ensure that the cell sizes of the two types of units are consistent;

[0086] Based on this, implicit functions of Schwarz surface and implicit functions of Diamond surface are used:

[0087] ,

[0088] ,

[0089] ,

[0090] ,

[0091] ,

[0092] ;

[0093] in For the implicit functions of the Schwarz surface, (These are the equivalent constants) For the implicit functions of the Diamond surface, are the equivalent constants;

[0094] Schwarz cell structure 131 and Diamond cell structure 132 were obtained. Then, a three-dimensional array was created between Schwarz cell structure 131 and Diamond cell structure 132, with each cell structure arrayed twice along the X-axis, Y-axis, and Z-axis respectively, resulting in Schwarz cell structure 133 and Diamond cell structure 134 with a size of 3a×3a×3a. These two structures were then imported into a Boolean operation module and subjected to an intersection operation (cell fusion) to obtain a Diamond-Schwarz hybrid Boolean cell, constructing a 3a×3a×3a biomimetic hybrid TPMS cell structure 13. The specific steps are as follows:

[0095] Let the integration center be Take a fusion band width Construct a piecewise weight function that varies along the x-direction:

[0096] ;

[0097] Then, the Schwarz cell structure 133 and the Diamond cell structure 134 are passed through the function:

[0098] ;

[0099] This is combined into a single implicit function, and then called on the function F on the grid in MATLAB. Extracting the isosurface yields a three-dimensional array cube structure with a total size of 3a in the x-direction, a smooth transition at 1.5a, and the remaining regions retaining the original Schwarz and Diamond shapes, respectively, forming a fused biomimetic hybrid TPMS cell structure 13.

[0100] Finally, the biomimetic hybrid TPMS cell structure 13 is arrayed in three dimensions along the X-axis, Y-axis and Z-axis respectively. Multiple biomimetic hybrid TPMS cell structures 13 distributed in a three-dimensional grid array together form a biomimetic hybrid TPMS structure.

[0101] like Figure 5 As shown, step 3 specifically involves:

[0102] Step 3.1: Prepare CHS@M powder 21. Disperse 0.20 g of monolayer MXene solid ultrasonically in 200 mL of anhydrous ethanol to obtain an MXene dispersion. Dissolve 1 mmol of CaCl2 in 100 mL of ethanol, add 130 mL of triethylamine (TEA), stir at room temperature for 30 min, then pour into the MXene dispersion and continue stirring for 1 h to obtain a mixed system. Prepare 100 mL of 0.01 mol / L NaSnO3 aqueous solution and add it dropwise to the mixed system at a rate of 1 mL / min. After the addition is complete, react at room temperature for 2 h and allow to stand overnight. The resulting black precipitate is separated by centrifugation, washed three times each with deionized water and ethanol, and finally dried in a vacuum oven at 60 °C for 12 h to obtain CHS@M powder 21.

[0103] Step 3.2: Prepare CoP@M nanosheets 22. Weigh 3 mmol of CoSO4·7H2O, 2 mmol of Na2HPO4·12H2O, 1 mmol of SDBS (sodium dodecylbenzenesulfonate), and 0.1 mol of urea and dissolve them in 100 mL of deionized water. React in a microwave reactor at 95 °C and 900 W for 10 min. After naturally cooling to room temperature, wash with deionized water at least three times to remove the surfactant, and vacuum dry at 60 °C to constant weight to obtain solid CoP. Subsequently, use 100 mL of 1 mmol / L Ti3C2 dispersion as the source of MXene (MXene is actually in T...). (i3C2MXene dispersion participated in the in-situ loading reaction), 3 mmol of CoSO4·7H2O and 6 g of urea were added to it, and the mixture was sonicated for 10 min to obtain liquid A; 2 mmol of NaH2PO4·2H2O and 1 mmol of SDBS were dissolved in 50 mL of deionized water and magnetically stirred for 15 min to obtain liquid B; then liquid B was slowly poured into liquid A and the whole mixture was transferred to a microwave reactor and reacted at 95 °C, 900 W and 200 rpm for 30 min. After naturally cooling to room temperature, the mixture was centrifuged and washed three times with deionized water, and finally vacuum dried at 60 °C to constant weight to obtain blackish purple CoP@M nanosheets 22;

[0104] Step 3.3: Prepare expanded reed flame retardant PRM powder 23. Soak the reed powder in 20% NaOH solution for 24 hours to remove impurities such as hemicellulose, lignin, and sugars. After centrifugation and filtration, wash repeatedly with deionized water to remove alkali, and dry in a 180℃ forced-air drying oven for 4 hours. Then, pulverize and pass through a 200-mesh sieve to obtain modified reed powder (AR) for later use. Subsequently, perform surface compounding of expansion-gas source-acid source. Weigh 1g of modified reed powder into a three-necked flask and add 100mL of deionized water. The mixture was refluxed and stirred in an oil bath at 80°C for 15 minutes to ensure uniform dispersion, thus obtaining an AR dispersion. Separately, 3g of dicyandiamide was dissolved in 50mL of deionized water and slowly poured into the AR dispersion. The mixture was refluxed at 80°C for 15 minutes, and then a 70wt% phytic acid solution containing 6g of phytic acid (PA) was added dropwise. The mixture was refluxed at 80°C for another 15 minutes. After cooling to room temperature, the mixture was centrifuged and filtered, washed with deionized water, and finally dried in an 80°C forced-air drying oven to constant weight, yielding expanded reed flame retardant PRM powder 23.

[0105] Step 3.4: Preheat epoxy resin EP to approximately 60°C to reduce viscosity, and stir at approximately 0.03 MPa to degas for about 20 minutes. Then, release the vacuum and, under the same temperature conditions, add CHS@M powder 21, CoP@M nanosheets 22, and expanded reed flame retardant PRM powder 23 in a single batch according to the mass ratio of epoxy resin EP: expanded reed flame retardant PRM powder 23: CHS@M powder 21: CoP@M nanosheets 22 = 100:8:1:1. Stir at approximately 200 rpm to initially disperse the mixture, then perform short-term intermittent ultrasonication. After the system is homogeneous, re-vacuum at approximately 0.03 MPa for several minutes to complete the secondary degassing, resulting in a stable EP / PRM-MXene flame retardant premix. Simultaneously, the bio-based curing agent VDTS2 was preheated at 50–55°C to reduce viscosity. Then, VDTS2 was slowly added to the premix at 55–60°C, with a VDTS2 to premix mass ratio of 100:11. Continuous stirring and brief ultrasonication were used to ensure complete diffusion of VDTS2 in the filler-containing system. After mixing, a short-term vacuum degassing process was performed to achieve the required flow dynamics for molding. Finally, the preheated mold was placed under vacuum and the slurry was slowly poured in, with a brief pause to allow residual air bubbles to rise and burst. Curing was then performed using a two-stage temperature program: first, maintaining the temperature at 80°C for approximately 2 hours, then lowering it to 50°C and holding for approximately 3 hours and 40 minutes. Finally, the mold was cooled to room temperature in the oven before demolding to obtain modified epoxy resin solution 24.

[0106] like Figure 6As shown, the preparation method of the biomimetic skeleton structure-modified epoxy resin multifunctional heterostructure 3 is as follows: The three-dimensional biomimetic skeleton structure 1, prepared by 3D printing equipment 4 using nickel-titanium powder 5, is placed into a customized silicone sealing mold 6, and the sealing mold 6 is preheated to 50-60℃. Then, the mixed modified epoxy resin solution 24 is poured into the sealing mold 6, so that the modified epoxy resin solution 24 covers the three-dimensional biomimetic skeleton structure 1 but is lower than the height of the mold. First, it is allowed to stand at 60℃ and 0.02MPa for about 20 minutes to completely remove bubbles. Then, the temperature is increased to 80℃ at 1-2℃ / min and held for 2 hours. After that, the temperature is reduced to 50℃ at the same rate and held for 3 hours and 40 minutes to allow the resin to fully crosslink and release internal stress. After curing, it is cooled to room temperature in the oven and demolded (modified epoxy resin fills the three-dimensional biomimetic skeleton structure 1) to obtain the biomimetic skeleton structure-modified epoxy resin multifunctional heterostructure 3, that is, the biomimetic heterostructure.

[0107] In summary, the three-dimensional biomimetic skeleton structure 1 with multi-scale energy dissipation capability constructed by this invention can effectively guide the graded transmission of impact loads. Through gradient porosity, circumferential support and multi-path force flow redistribution mechanism, it absorbs and disperses dynamic impact energy step by step, significantly enhancing the deformation resistance and overall structural stability of the aircraft nacelle under bird strike, hail or foreign object impact scenarios.

[0108] This invention introduces MXene hybrid flame retardants (CHS@M, CoP@M) and intumescent flame-retardant reed (PRM) into a modified epoxy resin composite system to construct a highly efficient and synergistic flame-retardant system. This system endows the material with excellent flame retardancy and thermal stability through multiple mechanisms such as carbon layer protection and catalytic carbonization, maintaining structural integrity under high-temperature airflow, aerodynamic heating, and repeated thermal cycling conditions. The modified epoxy matrix, combined with the air chambers within the three-dimensional biomimetic skeleton structure 1, forms a highly efficient thermal barrier path, effectively inhibiting the transfer of external high temperatures to the nacelle interior and significantly reducing the thermal load on the engine nacelle in extreme service environments.

[0109] This invention employs selective laser melting technology to fabricate a high-performance nickel-titanium alloy biomimetic skeleton. A vacuum-assisted impregnation and staged temperature-curing process are used to achieve a dense bond between the nickel-titanium alloy biomimetic skeleton and a modified epoxy resin solution 24, ensuring uniform interface quality and stable stress distribution within complex curved structures. This biomimetic heterogeneous structure overcomes the limitations of traditional separate designs for the nacelle insulation layer, load-bearing layer, and outer cladding layer, achieving a high degree of integration of key performance characteristics such as impact resistance and flame retardancy. The resulting high-strength, heat-resistant, and impact-resistant three-dimensional biomimetic nacelle protection system can provide more reliable structural safety for next-generation high thrust-to-weight ratio aircraft in extreme service environments, demonstrating significant engineering application value and promising prospects for widespread adoption.

[0110] 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 an impact-resistant and heat-insulating biomimetic heterostructure for an aircraft nacelle, characterized in that, The steps include the following: Step 1: Construct a three-dimensional bionic skeleton structure based on 3D modeling software (1); Step 2: Convert the three-dimensional bionic skeleton structure (1) into an STL file and import it into Magics software. Use selective laser melting technology to prepare a nickel-titanium alloy bionic skeleton that corresponds to the shape and size of the nacelle structure. Step 3: Prepare a modified epoxy resin solution (24) using MXene hybrid flame retardants CHS@M, CoP@M and intumescent flame retardant reed PRM. Step 4: Place the nickel-titanium alloy biomimetic skeleton obtained in Step 2 into a sealed mold (6) customized according to the nacelle structure size, ensuring that the skeleton is centered and fixed to the mold wall, and slowly pour in the modified epoxy resin solution (24) prepared in Step 3 until the nickel-titanium alloy biomimetic skeleton is completely wetted; then place the sealed mold (6) in a vacuum drying oven for 10-20 minutes of vacuum degassing treatment to remove air bubbles in the solution. After degassing, a staged curing process is used to obtain a biomimetic heterostructure. The three-dimensional biomimetic skeleton structure (1) in step 1 is a biomimetic bird bone structure (11) based on B-splines, a biomimetic osseointegrated structure (12), or a biomimetic hybrid TPMS structure; among them, the design steps of the biomimetic bird bone structure (11) based on B-splines are as follows: First, draw a square with side length a on the front reference plane. Take the center point o of square one as the origin, and denote the straight line passing through o and perpendicular to the front reference plane as the X-axis, the horizontal line passing through o as the Y-axis, and the vertical line passing through o as the Z-axis. Generate square two equidistant entities within square one with a spacing of h. Then, draw a central curve symmetrical about o using B-splines. The curve starts from point A, which is located to the left of the upper edge of square two and is a distance p from the Z-axis, bends inward, passes through o, and reaches point D, which is located to the right of the lower edge of square two and is a distance p from the Z-axis. Subsequently, offset the central curve equidistantly by h / 2 on both sides using offset entities to obtain a strip contour with a bandwidth of h. Then, mirror the strip contour with the Z-axis as the axis of symmetry. Finally, stretch the graphic composed of square one, square two, and the two strip contours along the X-axis to form a B-spline main structure with a thickness of m (111). Create a reference axis parallel to the Z axis at a distance a / 2 offset in the positive direction of the X axis. Rotate the B spline main structure (111) with the reference axis as the rotation axis. The array angle is 90°, and a total of 4 entities are generated to obtain the cube line frame structure (112). Reinforcing ribs are created on the upper and lower surfaces of the cubic linear frame structure (112). The shape of the reinforcing ribs is the same as that of the strip outline. The width of the reinforcing ribs is h and the thickness is m, thus obtaining the biomimetic bird bone cell structure (113). Finally, the biomimetic bird bone cell structure (113) is arrayed in three dimensions along the X-axis, Y-axis and Z-axis respectively. Multiple biomimetic bird bone cell structures (113) distributed in a three-dimensional grid array together form a biomimetic bird bone structure (11) based on B-spline.

2. The method for preparing an impact-resistant and heat-insulating biomimetic heterostructure for an aircraft nacelle according to claim 1, characterized in that, The design steps of the biomimetic bone fusion structure (12) are as follows: First, create a second cube line frame structure (122) that is identical to the cube line frame structure (112). Then, draw four sets of concentric circles with the vertices of the four edges parallel to the Z-axis as the center. Each set of concentric circles includes two circles with radii of r1 and r2 respectively. Then, extrude to create four concentric circle support columns. The thickness of the concentric circle support columns is m = r2 - r1, thus obtaining the interwoven spiral unit structure (123). On the upper and lower surfaces of the interwoven spiral unit structure (123), two reinforcing ribs with a width of h and a thickness of m are created along their respective diagonals. Both ends of the two reinforcing ribs extend to the outer side of the interwoven spiral unit structure (123). Taking the intersection of the diagonals as the center, a circle with a diameter of r2 is drawn and stretched into a circular plate with a thickness of m. Then, taking the intersection of the diagonals as the center, a circle with a diameter of r1 is drawn and stretched and cut off, thereby creating a concentric ring structure at the intersection of the two reinforcing ribs. Then, the endpoints of the two reinforcing ribs are connected in the lower end face of the interwoven spiral unit structure (123) to form a square path with a side length of k, and a rectangle with a width of b and a thickness of t. The cross section is stretched along the square path to form a closed lower square frame. The upper surface of the interwoven spiral unit structure (123) is stretched in the same way to form an upper square frame that is coaxially aligned with the lower square frame, and k=1.5a. Then, with the four vertices of the square path of the lower surface of the interwoven spiral unit structure (123) as the center, four sets of concentric circles are drawn. Each set of concentric circles includes two circles with radii R1 and R2 respectively. Four concentric circle support columns are created by stretching to connect the upper square frame and the lower square frame. The wall thickness of the concentric circle support column is m2=R1-R2. The creation of the bionic bone-spider web support unit structure (124) is completed. A local coordinate system is established within the unit plane of the biomimetic fibrous bone-spider web support unit structure (124). The unit plane is the yz plane passing through the geometric center of the biomimetic fibrous bone-spider web support unit structure (124) and whose normal is consistent with the global X-axis. The local coordinate system includes the y-axis and the z-axis, where the y-axis is parallel to the global Y-axis and the z-axis is parallel to the global Z-axis. The origin of the local coordinate system is the geometric center of the biomimetic fibrous bone-spider web support unit structure (124). The center curve is defined as follows: ； Where n>2, Z=a / 2-b, [0.28a, 0.36a], b > 0; and by offsetting ±h / 2 in the normal direction on both sides of the central curve, a boundary curve with bandwidth h is obtained: ； in, Let be the unit normal vector of the center curve 2. These represent the two boundary curves obtained by offsetting h / 2 along the positive and negative normal directions, respectively; A strip-shaped entity with a thickness of m is generated along the thickness direction. Then, the strip-shaped entity is arranged in a circular array with the straight line passing through the geometric center of the bionic bone-spider web support unit structure (124) and parallel to the Z-axis as the rotation axis. The array angle is 90°, and a total of 4 entities are generated to complete the construction of the bionic bone fusion cell structure (125). Finally, the biomimetic bone fusion cell structure (125) is arrayed in three dimensions along the X-axis, Y-axis and Z-axis respectively. Multiple biomimetic bone fusion cell structures (125) distributed in a three-dimensional grid array together form the biomimetic bone fusion structure (12).

3. The method for preparing an impact-resistant and heat-insulating biomimetic heterostructure for an aircraft nacelle according to claim 2, characterized in that, The design steps for the biomimetic hybrid TPMS structure are as follows: In the cube [0, A 3D mesh is created within the mesh, with a cell size of 'a'. Physical coordinates are mapped to dimensionless coordinates using a uniform periodic scaling method. ， ， ； Ensure that the cell sizes of the two types of units are consistent; Based on this, implicit functions of Schwarz surface and implicit functions of Diamond surface are used: ， ， ， ， ， ； in For the implicit functions of the Schwarz surface, (These are the equivalent constants) For the implicit functions of the Diamond surface, are the equivalent constants; Schwarz cell structure (131) and Diamond cell structure (132) were obtained. Then, the Schwarz cell structure (131) and Diamond cell structure (132) were arranged in a three-dimensional array. The two cell structures were arranged twice along the X-axis, Y-axis and Z-axis respectively, so as to obtain the Schwarz cell structure (133) and Diamond cell structure (134) with a size of 3a×3a×3a. The Schwarz cell structure (133) and the Diamond cell structure (134) were imported into the Boolean operation module and the intersection operation was performed to obtain the Diamond-Schwarz hybrid Boolean cell and construct a 3a×3a×3a biomimetic hybrid TPMS cell structure (13). Finally, the biomimetic hybrid TPMS cell structure (13) is arrayed in three dimensions along the X-axis, Y-axis and Z-axis respectively. Multiple biomimetic hybrid TPMS cell structures (13) distributed in a three-dimensional grid array together form a biomimetic hybrid TPMS structure.

4. The method for preparing an impact-resistant and heat-insulating biomimetic heterostructure for an aircraft nacelle according to claim 3, characterized in that, Step 3 specifically involves: Step 3.1, prepare CHS@M powder (21). 0.20 g of monolayer MXene solid was ultrasonically dispersed in 200 mL of anhydrous ethanol to obtain an MXene dispersion. 1 mmol of CaCl2 was dissolved in 100 mL of ethanol, and 130 mL of triethylamine was added. After stirring at room temperature for 30 min, the mixture was poured into the MXene dispersion and stirred for another 1 h to obtain a mixed system. 100 mL of 0.01 mol / L NaSnO3 aqueous solution was prepared and added dropwise to the mixed system at a rate of 1 mL / min. The mixture was reacted at room temperature and allowed to stand overnight. The resulting product was centrifuged, washed with deionized water and ethanol, and finally dried under vacuum at 60 °C to obtain CHS@M powder (21). Step 3.2, prepare CoP@M nanosheets (22). Weigh 3 mmol of CoSO4·7H2O, 2 mmol of Na2HPO4·12H2O, 1 mmol of SDBS, and 0.1 mol of urea and dissolve them in 100 mL of deionized water. React in a microwave reactor at 95 °C and 900 W. CoP precipitate is generated in the reaction solution. Then, MXene is added to the reaction solution and in-situ loading reaction is carried out under microwave conditions. The obtained product is centrifuged, washed with deionized water, and finally dried under vacuum at 60 °C to obtain CoP@M nanosheets (22). Step 3.3: Prepare expanded reed flame retardant PRM powder (23). Soak the reed powder in 20% NaOH solution for 24 hours, centrifuge and filter, wash repeatedly with deionized water to remove alkali, dry at 180℃, pulverize and pass through a 200-mesh sieve to obtain modified reed powder. Weigh 1g of modified reed powder into a three-necked flask, add 100mL of deionized water, and reflux and stir for 15min under 80℃ oil bath conditions to make it uniformly dispersed to obtain AR dispersion. Dissolve 3g of dicyandiamide in 50mL of deionized water and slowly pour it into AR dispersion, reflux at 80℃ for 15min, then add 70wt% phytic acid solution containing 6g of phytic acid, reflux at 80℃ for 15min again, cool to room temperature, centrifuge and filter, wash with deionized water, and finally dry in an 80℃ forced-air drying oven to constant weight to obtain expanded reed flame retardant PRM powder (23). Step 3.4: CHS@M powder (21), CoP@M nanosheets (22), and expanded reed flame retardant PRM powder (23) are added to epoxy resin, wherein the epoxy resin is 100 parts by mass, CHS@M powder (21) is 0.5 to 2 parts by mass, CoP@M nanosheets (22) is 0.5 to 2 parts by mass, and expanded reed flame retardant PRM powder (23) is 6 to 12 parts by mass. The modified epoxy resin solution (24) is prepared by stirring-ultrasound-vacuum defoaming-molding curing process.

5. A biomimetic heterogeneous structure for an aircraft nacelle that is impact-resistant and heat-insulating, characterized in that, It is prepared by the method described in claim 4.

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