A design method of a bionic dot array structure based on a sea gull feather shaft

Abstract

This invention relates to the field of lattice structure technology and provides a method for studying the energy absorption characteristics of a biomimetic structure based on a seagull feather shaft. Key geometric parameters such as moment of inertia, aspect ratio, and wall thickness distribution are extracted from the transitional cross-section of the seagull feather shaft, which gradually changes from circular to square. These parameters are then fused with face-to-face splicing of honeycomb cells and back-to-back splicing of sinusoidal curved edges with negative Poisson's ratio to establish four types of biomimetic unit cells. A regression model is established using the Box-Behnken method, with multi-objective optimization targeting maximum total energy absorption, maximum specific energy absorption, and minimum peak stress to obtain the optimal parameters. After arraying, the sidewall arc surfaces of adjacent unit cells form a predetermined gap, generating surface contact coupling during compression to achieve progressive load redistribution. Experiments and simulations verify the deformation and energy absorption characteristics. The invention can improve the lightweighting and energy absorption performance of biomimetic energy-absorbing structures.

Description

Technical Field

[0001] This invention belongs to the field of lattice structure technology, and particularly relates to a biomimetic lattice structure design method based on seagull feather shafts. Background Technology

[0002] Lattice structures not only have advantages such as lightweight and high mechanical strength, but also have good manufacturability to a certain extent. Therefore, they have been widely used in transportation, aerospace and armor protection. As a special structural form, lattice structures provide new ideas and methods for lightweight and high energy absorption.

[0003] The seagull feather rachis, formed through long-term natural selection, exhibits a gradual transitional cross-section from circular to square, achieving high moment of inertia and buckling resistance with limited material usage. Macroscopically, the seagull feather rachis is a slender tubular shape, with its diameter gradually decreasing from the root to the tip, and its cross-section transitioning from circular to square. Microscopically, the seagull feather rachis consists of a dense outer cortex and a porous inner medulla, with a natural transition between the two through continuous variation. Irregularly shaped protrusions on the inner wall of the cortex interlock with the internal medullary units, and the medullary region is composed of numerous closed microscale air-cavity units. Therefore, from both macroscopic and microscopic perspectives, the seagull feather rachis structure is an excellent lightweight and high-strength biological structure, providing researchers with numerous inspirations for biomimetic applications.

[0004] When subjected to axial compressive load, the curved edges of the unit cell of the sinusoidal curved edge negative Poisson ratio back-to-back structure cause the sidewalls to contract and shift laterally inward due to bending, resulting in a tensile expansion effect with negative Poisson ratio characteristics. Moreover, the overall energy absorption of the structure is greatly enhanced after being three-dimensionalized. However, there is currently no research on combining the geometric features of the transition section of the seagull feather shaft with the sinusoidal curved edge negative Poisson ratio back-to-back splicing method to form a biomimetic lattice structure. Summary of the Invention

[0005] The purpose of this invention is to provide a design method for a biomimetic lattice structure based on a seagull feather shaft, aiming to solve the problems existing in the prior art as identified in the background art.

[0006] The present invention is implemented as follows: a design method based on a seagull feather shaft biomimetic lattice structure, the method comprising:

[0007] Starting from the structural characteristics of the transition section of the seagull feather shaft, the key geometric parameters and structural mechanisms are extracted through similarity analysis and extraction of the transition section of the seagull feather shaft from a circle to a square. Based on the principles of bionics, the selected parameters are confirmed through mechanical analysis, and the parameters are analyzed from the perspectives of the moment of inertia, aspect ratio and wall thickness distribution.

[0008] Based on the structural characteristics of the transition section of the seagull feather shaft, structural features were extracted and integrated with the honeycomb face-to-face splicing method and the sinusoidal curved edge negative Poisson ratio back-to-back splicing method to establish a preliminary three-dimensional macroscopic biomimetic unit cell structure. The range of each parameter and its size was determined for structural construction and size parameter optimization.

[0009] Parametric variable analysis was conducted through quasi-static compression finite element simulation to identify three key parameters that significantly affect the energy absorption performance of each configuration. Then, a quadratic regression model was established using the Box-Behnken response surface method, and multi-objective optimization was implemented with the objectives of maximizing total energy absorption, maximizing specific energy absorption, and minimizing peak stress to obtain the structural parameters of the biomimetic unit cell structure with optimal energy absorption performance.

[0010] The biomimetic unit cell structure was constructed using the structural parameters of the biomimetic unit cell structure with optimal energy absorption performance.

[0011] Bionic unit cell structures are arrayed along a specified direction and number to form a bionic lattice structure.

[0012] Preferably, after arraying the biomimetic unit cell structure to form a biomimetic lattice structure, the method further includes:

[0013] Explicit dynamic analysis was performed using the LS-DYNA module of the ANSYS Workbench platform. The solution type was set to explicit dynamics, which is suitable for solving material nonlinearity, large deformation, and complex contact problems.

[0014] The energy absorption performance of the biomimetic lattice structure was verified by quasi-static compression finite element simulation.

[0015] In the quasi-static compression simulation, the indenter applies displacement loading along the negative Z-axis at a loading rate of 0.2 mm / min, with a loading stroke of 50% of the initial height of the structure. Automatic mesh generation is used, with hexahedral elements as the primary element type and tetrahedral elements as secondary elements. The mesh size for the tested structure is set to 0.8 mm, while the mesh size for the upper and lower pressure plates and the drop hammer head is set to 2 mm. The contact type is defined as surface-to-surface contact, and the static friction coefficient is set to 0.2. The lower base is subjected to complete fixed constraints, while the upper indenter retains only the vertical degree of freedom.

[0016] A biomimetic seagull feather shaft lattice structure was fabricated using additive manufacturing technology, and a quasi-static compression test was conducted to verify the accuracy of the simulation test.

[0017] During compression, the biomimetic unit cell of this invention features a gradually changing arc profile on its sidewalls, derived from the transition section of a seagull's feather shaft. During compression deformation, the convex arc surfaces of adjacent unit cells form a geometrically interlocking contact with the concave regions of adjacent unit cells. This self-contact coupling effect prevents the compressive load from being concentrated on the bending yielding of a single cell wall. Instead, it achieves a gradual redistribution of load through the gradual increase in the intercellular contact area. This mechanism is not present in traditional honeycomb structures or conventional negative Poisson's ratio structures—the cell walls of traditional honeycomb structures deform independently without interference, and while conventional negative Poisson's ratio structures exhibit inward contraction, surface contact coupling between cell walls does not occur. The presence of this coupling mechanism in this invention makes the plateau phase of the stress-strain curve smoother, effectively avoiding sudden load drops and improving energy absorption stability.

[0018] Reference Figure 19 and Figure 20 The compression deformation process illustrated uses a back-to-back 6-6 type lattice structure as an example to explain the generation process of the self-contact coupling effect: In the initial compression stage (compressive strain approximately 0-20%), each unit cell deforms independently, with gaps remaining between the sidewall arc surfaces, and the stress-strain curve exhibits an elastic rising segment. Entering the middle compression stage (compressive strain approximately 20%-25%), the cell walls undergo significant bending and buckling, and the stress-strain curve enters a plateau stage. When the compressive strain reaches approximately 25%, the convex sidewall arc surfaces of adjacent unit cells begin to contact the concave regions of adjacent unit cells. Subsequently, the intercellular contact area continuously increases with the amount of compression, and the contact force gradually participates in load-bearing, significantly reducing the fluctuation amplitude of the plateau segment of the stress-strain curve. Finally, in the compaction stage (compressive strain greater than 40%), the intercellular gaps completely disappear, and the stress rises sharply. Compared with traditional honeycomb structures, the biomimetic lattice structure of this invention, due to the gradual generation of intercellular surface contact, significantly reduces the stress fluctuation amplitude of the plateau segment and significantly improves energy absorption stability.

[0019] Preferably, the biomimetic unit cell structure includes four configurations: face-to-face 6-6, face-to-face 8-8, back-to-back 6-6, and back-to-back 8-8. The key geometric features of the seagull feather shaft transition section are integrated with a honeycomb face-to-face splicing method to form a face-to-face configuration, and with a sinusoidal curved edge negative Poisson's ratio back-to-back splicing method to form a back-to-back configuration. The overall geometry of each configuration is mirror-image distributed about the center xy plane and maintains symmetry in the xz and yz symmetry directions. The endpoints of the biomimetic unit cell structure are connected and arrayed to form a biomimetic lattice structure.

[0020] Preferably, the length of the upper hypotenuse of the preliminary biomimetic unit cell structure is L1 = 1.2 mm, ranging from 1.1 mm to 1.3 mm; the width of the upper arc is L2 = 5 mm, ranging from 4 mm to 6 mm; the half-height is H1 = 10.5 mm, ranging from 9.5 mm to 11.5 mm; the height of the lower arc is H2 = 5.5 mm, ranging from 4 mm to 6 mm; the height of the upper arc is H3 = 2.5 mm, ranging from 2.3 mm to 2.7 mm; and the radius of the side curve is R1 = 10 mm, ranging from 9 mm to 12 mm.

[0021] Preferably, the optimized biomimetic unit cell structure parameters are as follows: for the face-to-face 6-6 type structure, the upper arc width = 5.12mm, half height = 10.97mm, and side curve radius = 9.9mm; for the back-to-back 6-6 type structure, the upper sloping side length = 1.25mm, half height = 11.03mm, and lower arc height = 6mm; for the face-to-face 8-8 type structure, the upper sloping side length = 1.1mm, half height = 10.5mm, and side curve radius = 10.22mm; and for the back-to-back 8-8 type structure, the upper sloping side length = 1.12mm, half height = 10.34mm, and upper arc height = 2.5mm.

[0022] Table 1 Comparison of mechanical properties before and after optimization of four biomimetic unit cell configurations.

[0023]

[0024] A biomimetic lattice structure designed using the biomimetic lattice structure design method based on the seagull feather shaft as described above, wherein the biomimetic lattice structure is formed by connecting the endpoints of a biomimetic unit cell structure in an array.

[0025] This invention provides a biomimetic lattice structure design method based on seagull feather shafts. This method offers controllability and repeatability, allowing for the analysis and extraction of structural characteristics from natural organisms. It can be combined with existing structures to customize different forms of lattice lattices, exploring more lattice structures with special properties and application potential, thus promoting development and innovation in structural engineering. By combining the geometric features of the seagull feather shaft transition section with both honeycomb face-to-face splicing and sinusoidal curved-edge negative Poisson's ratio back-to-back splicing methods, the advantages of all three are integrated. The biomimetic lattice structure exhibits higher total energy absorption, specific energy absorption, and a more stable deformation mode under quasi-static compression and impact loads. It is also lightweight, ingeniously constructed, applicable, and material-saving. Due to the coupling mechanism formed by intercellular geometric interlocking and self-contact, it can effectively disperse external forces, resulting in stronger resistance. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the biomimetic lattice structure feature extraction and design process of the seagull feather shaft provided in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the size parameters of the single cell structure in the biomimetic lattice structure of the seagull feather shaft provided in the embodiment of the present invention;

[0028] Figure 3 This is a front view and a schematic diagram of the dimensions of the biomimetic dot matrix structure of the seagull feather shaft provided in an embodiment of the present invention;

[0029] Figure 4 This is a top view of the biomimetic dot matrix structure of the seagull feather shaft provided in an embodiment of the present invention;

[0030] Figure 5 This is an isometric view of the biomimetic lattice structure of the seagull feather shaft provided in an embodiment of the present invention;

[0031] Figure 6 This is a front view of a biomimetic dot matrix structure of a seagull feather shaft provided in an embodiment of the present invention;

[0032] Figure 7 This is a top view of a biomimetic dot matrix structure of a seagull feather shaft provided in an embodiment of the present invention;

[0033] Figure 8 This is an isometric view of a biomimetic lattice structure for a seagull feather shaft provided in an embodiment of the present invention;

[0034] Figure 9 This invention provides a biomimetic lattice structure photopolymerization 3D fabrication method for seagull feather shafts.

[0035] Figure 10 This is a contact force-displacement diagram of a quasi-static compression test of a biomimetic lattice structure for a seagull feather shaft provided in an embodiment of the present invention;

[0036] Figure 11 This is a total energy absorption-displacement diagram of a quasi-static compression test of a biomimetic lattice structure for a seagull feather shaft provided in an embodiment of the present invention.

[0037] Figure 12 This is a comparison diagram of contact force and impact displacement of a novel energy-absorbing box core sample with a biomimetic lattice structure of a seagull feather shaft provided in an embodiment of the present invention, based on impact simulation and testing.

[0038] Figure 13 This is a comparison diagram of kinetic energy and impact displacement of a novel energy-absorbing box core sample with a biomimetic lattice structure of a seagull feather shaft provided in an embodiment of the present invention, based on impact simulation and testing.

[0039] Figures 14 to 17To determine the optimal parameter combination for four biomimetic unit cell structures, response surface optimization calculations were performed using Design-Expert software. The goal was to maximize energy absorption and specific energy absorption while minimizing equivalent stress. Other non-essential factors were controlled by taking the median value of the interval to obtain the corresponding optimal parameter combination.

[0040] Figure 18 This is a diagram of a quasi-static compression test platform for a biomimetic lattice structure of a seagull feather shaft provided in an embodiment of the present invention;

[0041] Figures 19 to 20 This is a comparison between a quasi-static compression test process diagram and a simulation deformation cloud diagram of a biomimetic lattice structure for a seagull feather shaft provided in an embodiment of the present invention.

[0042] Figure 21 This is a diagram of a drop hammer impact test platform with a biomimetic lattice structure for a seagull feather shaft provided in an embodiment of the present invention;

[0043] Figures 22 to 23 This invention conducts impact simulation and experimental comparative analysis on four novel energy-absorbing box core samples based on the biomimetic lattice structure of seagull feather shafts. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0046] like Figure 1 As shown, starting from the structural characteristics of the transition section of the seagull feather shaft from a circle to a square, the main structural elements and structural mechanisms are extracted through similarity analysis and feature extraction of its transition configuration. Based on the principles of bionics, the structural mechanisms are confirmed through mechanical analysis methods, and the key geometric parameters are analyzed from the perspectives of cross-sectional moment of inertia, aspect ratio, and wall thickness distribution.

[0047] like Figure 1 As shown, structural features were extracted based on the characteristics of the transition section of the seagull feather shaft, and then fused with the honeycomb face-to-face splicing structure and the sinusoidal curved edge negative Poisson ratio back-to-back structure to construct four types of three-dimensional macroscopic preliminary biomimetic unit cell structures: face-to-face 6-6 type, face-to-face 8-8 type, back-to-back 6-6 type, and back-to-back 8-8 type. At the same time, the structural parameters and their size ranges were established for subsequent structure construction and parameter optimization.

[0048] like Figures 2-5As shown, parameter variable analysis was carried out through quasi-static compression finite element simulation to screen out key parameters that significantly affect the energy absorption performance of the structure. A quadratic regression model was established, and multi-objective optimization design was carried out on the preliminary biomimetic unit cell structure with the optimization objectives of maximizing total energy absorption, maximizing specific energy absorption, and minimizing peak stress, so as to obtain the optimal combination of structural parameters for energy absorption performance.

[0049] like Figures 6-8 As shown, a biomimetic unit cell structure was constructed using optimal structural parameters and arranged in an array through endpoint connections to form a biomimetic seagull feather lattice structure. Subsequently, its mechanical properties were verified through quasi-static compression simulation tests, and its deformation mode and energy absorption characteristics were analyzed.

[0050] The required 3D model is created using computer-aided design software (SOLIDWORKS). After the design is completed, the model is converted into STL format for subsequent printing preparation.

[0051] Slicing Processing: The 3D model in STL format is input into the slicing software for slicing processing. The slicing software decomposes the model into multiple thin slices, each with a thickness of 0.1mm, and generates printing path information for each layer to determine the trajectory of the light beam during printing.

[0052] Printing preparation: Select photosensitive resin material and transmit the printing path information generated by the slicing software to the printer control system.

[0053] 3D printing: Start the printer, set the light intensity to 500mW / cm², and the printing speed to 10mm / h. The light source shines on the first layer of resin, which cures and forms the first layer. Then, the work platform lowers a certain distance to expose the next layer of resin to the light source. The light beam shines on the next layer again, and this process is repeated until the entire model is printed.

[0054] Post-processing: After printing is completed, the printed object is removed from the printing platform and post-processing work such as removing the support structure, cleaning, and curing is carried out.

[0055] Combination Figures 10 to 17 This invention provides a biomimetic lattice structure design method based on a seagull feather shaft, which has good controllability and repeatability. It can be used to extract biological structural features from nature and combine them with engineering structures to construct various forms of lattice structures. This structure integrates the advantages of seagull feather shaft transition cross section, honeycomb structure and negative Poisson's ratio structure. Under quasi-static compression and impact load, it exhibits better energy absorption performance and stable deformation mode. The impact test simulation is highly consistent with the real experiment. At the same time, it has the advantages of lightweight, ingenious structure and high material utilization. It can effectively disperse external forces and improve the overall load-bearing capacity, and has good engineering application value.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0057] like Figure 18 As shown, a quasi-static compression test was conducted to verify the accuracy of the simulation test. This test used an INSTRON 3382 universal testing machine at a temperature of 25°C and a relative humidity of 50%. The loading rate was set to 0.2 mm / min. Quasi-static compression tests were performed on four selected biomimetic lattice structure specimens based on seagull feather shafts. The contact force-displacement change curves were recorded synchronously after the test started, with a data acquisition interval of 0.2 s. All data were exported after the test was completed.

[0058] like Figures 19 to 20 As shown, LS-DYNA was used for simulation experiments. The mesh generation was still performed using the automatic mesh generation method in the Workbench module, with hexahedral elements as the main element type and tetrahedral elements as the auxiliary element type. The mesh size of the upper and lower pressure plates and the drop hammer head was set to 2 mm, and the mesh size of the structure under test was set to 0.8 mm. Both the fixed plate and the moving plate were set as rigid bodies. The fixed plate was subjected to a completely fixed constraint, while the moving plate was restricted to all degrees of freedom except the vertical direction. Displacement was applied downward along the core layer direction. The simulation used surface-to-surface contact, and the contact type was set to frictional contact. The static friction coefficient was set to 0.2 to avoid penetration between structures. The material was set to photosensitive resin, and the fixed plate and the moving plate were made of structural steel. The material properties are shown in Table 2.

[0059] Table 2 Material Property Parameters

[0060]

[0061] like Figure 21 As shown, an impact experiment was conducted to verify the accuracy of the simulation. This experiment used an INSTRON 9450 drop hammer impact testing machine; the test temperature was 25°C and the relative humidity was 50%. The machine was equipped with a 12.5mm diameter hemispherical steel impact hammer, and the hammer's geometry and material parameters were consistent with the impact component in the simulation model. The test conditions were completely aligned with the simulation parameter settings. By adjusting the drop hammer's counterweight and drop height, the impact kinetic energy was precisely controlled to 6J, ensuring that the test and simulation loading conditions were consistent.

[0062] like Figures 22 to 23As shown, LS-DYNA was used for simulation experiments. The mesh generation still adopted the automatic mesh generation method in the Workbench module, with hexahedral elements as the main element type and tetrahedral elements as the auxiliary element type. The mesh size of the upper and lower pressure plates and the drop hammer head was set to 2mm, and the mesh size of the structure under test was set to 0.8mm. The hammer head was set as a rigid body, the lower plate was set as a fixed plate, and the hammer head was placed directly above the geometric center of the structure under test, and a vertically downward impact load was applied to it. The simulation adopted frictional contact, the contact type was set to frictional contact, the static friction coefficient was set to 0.2, and the material was set to photosensitive resin.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A design method based on a biomimetic seagull feather shaft lattice structure, characterized in that, The method includes: S1. Bionic feature extraction and parameterization: The two-dimensional contour of the single bionic cell is extracted from the transition cross-section configuration of the seagull feather axis, which gradually changes from a circle to a square. The two-dimensional contour includes six geometric parameters: upper sloping side length L1, upper arc width L2, half height H1, lower arc height H2, upper arc height H3, and side curve radius R1. The side curve adopts a circular arc transition to achieve the gradient feature from a narrow waist at the top to a wide bottom at the bottom. S2. Three-dimensional single-cell construction and splicing: After stretching the two-dimensional contour longitudinally to form a three-dimensional single-cell shell, it is fused according to the honeycomb face-to-face splicing method and the sinusoidal curved edge negative Poisson ratio back-to-back splicing method respectively. The face-to-face splicing method is that the concave surfaces of two single-cells are interlocked to form a closed cavity, and the back-to-back splicing method is that the convex surfaces of two single-cells are interlocked to form an open configuration that expands outward from the center. S3. Generation of biomimetic unit cell configurations: After the spliced ​​unit cells are rotated around the central axis and arrayed at equal angles 6 or 8 times, they are mirrored about the central xy plane to form four types of biomimetic unit cell structures: face-to-face 6-6 type, face-to-face 8-8 type, back-to-back 6-6 type, and back-to-back 8-8 type. Each configuration is symmetrical in the xz and yz symmetry planes. S4. Parameter Sensitivity Analysis and Multi-Objective Optimization: The wall thickness t was kept constant during the sensitivity analysis and optimization process, with a value of 2mm. Then, parameter variable analysis was carried out through quasi-static compression finite element simulation. Sensitivity analysis of six geometric parameters was performed using the single-factor analysis method. The Box-Behnken response surface method was used to establish a quadratic regression model for the three key parameters of each configuration. Multi-objective optimization was carried out with the objectives of maximizing total energy absorption, maximizing specific energy absorption, and minimizing peak stress to obtain the optimal structural parameters. For each configuration, three key parameters with significant influence were selected. The key parameters for the face-to-face 6-6 type are the upper arc width L2, half height H1, and side curve radius R1. The key parameters for the back-to-back 6-6 type are the upper inclined side length L1, half height H1, and lower arc height H2. The key parameters for the face-to-face 8-8 type are the upper inclined side length L1, half height H1, and side curve radius R1. The key parameters for the back-to-back 8-8 type are the upper inclined side length L1, half height H1, and upper arc height H3. S5. Construction of biomimetic lattice structure: Biomimetic unit cell structures are arrayed along a specified direction and number to form a biomimetic lattice structure. During the arraying process, a preset gap is formed between the side wall arc surfaces of adjacent biomimetic unit cells. The preset gap allows the convex side wall arc surfaces of adjacent biomimetic unit cells to gradually approach the concave region of adjacent unit cells and make surface contact during axial compression deformation. The gradual increase of the intercellular contact area realizes the progressive redistribution of compressive load and forms a self-contact coupling energy absorption mechanism.

2. The method according to claim 1, characterized in that, The process after step S5 also includes: The mechanical properties and self-contact coupling effect of the biomimetic lattice structure were verified by quasi-static compression finite element simulation. The biomimetic lattice structure specimen was prepared by additive manufacturing technology, and a quasi-static compression test was conducted. The contact force-displacement curve and deformation mode obtained from the experiment were compared with the finite element simulation results to verify the accuracy of the simulation model.

3. The design method according to claim 1, characterized in that: In the face-to-face splicing method, after the concave surfaces of the two individual cells are interlocked, a double-wall structure is formed between the adjacent cell walls at the splicing point. The double-wall structure improves the load-bearing capacity through the synergistic buckling deformation of the two cell walls during axial compression. In the back-to-back splicing method, after the convex surfaces of the two individual cells are spliced ​​together, an initial contact surface is formed between the two back arc surfaces at the splicing point. During the axial compression process, the cell walls that expand outward on both sides undergo lateral inward shrinkage due to the bending of the curved edges, causing the biomimetic single cell to exhibit negative Poisson's ratio shrinkage deformation characteristics.

4. The biomimetic structural design method based on seagull feather shafts according to claim 1, characterized in that, The values ​​of the six geometric parameters mentioned in step S1 are as follows: the length of the upper hypotenuse L1 is 1.1mm-1.3mm, the width of the upper arc L2 is 4mm-6mm, the half height H1 is 9.5mm-11.5mm, the height of the lower arc H2 is 4mm-6mm, the height of the upper arc H3 is 2.3mm-2.7mm, and the radius of the side curve R1 is 9mm-12mm. The wall thickness t is set as a constant control variable throughout the study to ensure that the influence of the research focus, the contour change, is not interfered with by other variables.

5. The biomimetic structural design method based on seagull feather shafts according to claim 1, characterized in that, The biomimetic unit cell structure parameters after optimization design of the key parameters screened by sensitivity analysis for each configuration in step S4 are as follows: the wall thickness t remains constant at 2 mm; for the face-to-face 6-6 type structure, the upper arc width L2 is 5.12 mm, half height H1 is 10.97 mm, and the side curve radius R1 is 9.9 mm; for the back-to-back 6-6 type structure, the upper oblique side length L1 is 1.25 mm, half height H1 is 11.03 mm, and lower arc height H2 is 6 mm; for the face-to-face 8-8 type structure, the upper oblique side length L1 is 1.1 mm, half height H1 is 10.5 mm, and the side curve radius R1 is 10.22 mm; for the back-to-back 8-8 type structure, the upper oblique side length L1 is 1.12 mm, half height H1 is 10.34 mm, and upper arc height H3 is 2.5 mm.

6. A biomimetic lattice structure, characterized in that, It includes multiple biomimetic unit cells arranged in an array along the x, y, and z directions, each of the biomimetic unit cells comprising: Multiple single-cell units, each of which is a three-dimensional shell with a wall thickness t formed by longitudinal stretching, and its cross-sectional profile has a gradually changing shape that is narrower at the top and wider at the bottom. It includes six geometric parameters: upper inclined side length L1, upper arc width L2, half height H1, lower arc height H2, upper arc height H3, and side curve radius R1. The side is connected to the upper narrow waist region and the lower wide bottom region by a circular arc with a radius of R1. The individual cell units are spliced ​​together face-to-face or back-to-back, and then arrayed at equal angles 6 or 8 times around the central axis and mirrored about the central horizontal plane to form the biomimetic cell. Multiple biomimetic unit cells are connected at their endpoints and arranged in an array along the x, y, and z directions to form the biomimetic lattice structure. In the biomimetic lattice structure, an initial gap is formed between the sidewall arc surfaces of adjacent biomimetic unit cells. The size and shape of the initial gap are configured such that when an axial compressive load is applied along the z-direction, the convex sidewall arc surfaces of adjacent biomimetic unit cells gradually approach the concave region of adjacent unit cells. When the compressive strain reaches a set threshold, surface contact occurs to form geometric interlocking. The gradual redistribution of compressive load is achieved by gradually increasing the intercellular contact area.

7. The biomimetic lattice structure according to claim 6, characterized in that: The wall thickness t of the three-dimensional shell is set to 2mm to balance simulation accuracy and printability. The structural parameters of the face-to-face 6-6 type bionic unit cell are: upper arc width L2 of 5.12mm, half height H1 of 10.97mm, and side curve radius R1 of 9.9mm; or, the structural parameters of the back-to-back 6-6 type bionic unit cell are: upper oblique side length L1 of 1.25mm, half height H1 of 11.03mm, and lower arc height H2 of 6mm; or, the structural parameters of the face-to-face 8-8 type bionic unit cell are: upper oblique side length L1 of 1.1mm, half height H1 of 10.5mm, and side curve radius R1 of 10.22mm; or, the structural parameters of the back-to-back 8-8 type bionic unit cell are: upper oblique side length L1 of 1.12mm, half height H1 of 10.34mm, and upper arc height H3 of 2.5mm.

8. The biomimetic lattice structure according to claim 6, characterized in that: During the quasi-static compression process, when the compressive strain exceeds 25%, the convex sidewalls and concave regions of adjacent biomimetic unit cells begin to make surface contact. This self-contact coupling effect makes the plateau phase of the stress-strain curve smoother and avoids sudden load drops.

9. The application of the biomimetic lattice structure according to any one of claims 6 to 8 in cushioning packaging components, personal protective equipment, or low-velocity impact energy-absorbing components.

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