Foam filling sine negative Poisson's ratio structure, design method and preparation method

Abstract

The invention discloses a foam filling sine negative Poisson's ratio structure, a design method and a preparation method. The foam-filled sine negative Poisson's ratio structure comprises a plurality of cell element structures which are transversely and longitudinally arranged and connected, and structural gaps are filled with polyurethane foam. According to the cell element structure, on the basis of a traditional inner hexagon structure, inward-concave straight plates on the two sides are replaced with sine function curved plates, and the problem of stress concentration caused by geometric mutation in the straight plate deformation process is solved. According to the design method and the preparation method of the foam-filled sine negative Poisson's ratio structure, the bearing capacity of the structure can be rapidly evaluated, a mathematical relationship between sine curve parameters and structural platform stress is established, and the sine negative Poisson's ratio structure can be accurately designed according to platform stress requirements; a liquid foaming method is adopted for filling in a foam filling mode, the structure can be perfectly attached to a complex structure, and the structure is particularly suitable for a sine negative Poisson's ratio structure with curved plates on the two sides.

Description

Technical Field

[0001] This invention relates to the field of metamaterials technology, specifically to a foam-filled sinusoidal negative Poisson's ratio structure, its design method, and its preparation method. Background Technology

[0002] In recent years, with the diversification of engineering application needs, the development of lightweight, high-strength new materials and structures has become a research hotspot in academic and engineering fields. Metamaterials are composite materials or structural arrays composed of artificially designed microstructures, possessing extraordinary physical properties and designability. As a type of metamaterial, negative Poisson's ratio structures, with their unique deformation mechanism of compressive contraction and tensile expansion and excellent energy absorption characteristics, have been widely used in fields such as vehicles, aerospace, and military industries.

[0003] Common negative Poisson's ratio structures include internal hexagonal structures, rigid bodies of revolution, and chiral structures, with internal hexagonal structures receiving the most research and application. Traditional internal hexagonal structures have large voids, resulting in poor stability during deformation. To improve their load-bearing capacity and energy absorption, current reinforcement designs for internal hexagonal structures mostly involve introducing additional support members or combining them with other negative Poisson's ratio structures, remaining at the single-material stage. Research on improving the overall structural performance through multi-material coupling is limited. Existing research shows that filling honeycomb structures with low-density foams such as aluminum foam and rubber can improve the structure's energy absorption. Rigid polyurethane, with its high energy absorption efficiency, excellent flowability, and foaming properties, shows great promise for combining with negative Poisson's ratio structures. Traditional negative Poisson's ratio structure design requires iterative trial and error to match structural parameters with desired performance, leading to low design efficiency and preventing precise and controllable design of structural parameters. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a foam-filled sinusoidal negative Poisson's ratio structure, its design method, and its fabrication method. Compared to traditional inner hexagonal structures, this structure is more stable during deformation and possesses stronger load-bearing capacity and energy absorption effect. Furthermore, based on the analytical formula for the plateau stress of the foam-filled sinusoidal negative Poisson's ratio structure, the load-bearing capacity of the structure can be quickly assessed, and customized plateau stress design can be achieved through the mathematical relationship between the sinusoidal curve parameters and the structural plateau stress.

[0005] The present invention solves the above-mentioned technical problems by adopting the following technical solution:

[0006] A foam-filled sinusoidal negative Poisson's ratio structure is constructed using a framework of multiple cellular structures arranged horizontally and vertically, with foam filling within the framework. Each cellular structure consists of an upper plate, a lower plate, two sinusoidal curved plates on either side, and two horizontally connecting plates on the outer sides of the curved plates. Each cellular structure is horizontally connected via the two horizontally connecting plates, and vertically, the upper and lower plates are connected to the upper and lower plates of adjacent cellular structures.

[0007] The upper and lower plates have a length of L, the sinusoidal curved plate has an amplitude of A and a period of T, the horizontal connecting plate has a length of L / 2, the upper and lower plates have a thickness of t / 2, and the remaining plates have a thickness of t. An array structure is obtained by arranging individual cell structures horizontally and vertically. The total length of this array structure is X, the out-of-plane width is Y, and the total height is Z.

[0008] For each cell structure, with the cell center as the origin O, an x-axis is established along the length of the transverse connecting plate, and a y-axis is established along the height of each cell. The expression for the sine function curve panel function on the right side of the cell structure is as follows:

[0009]

[0010] Where A is the amplitude of the sine function, L is the length of the upper and lower plates, and T is the period of the sine function.

[0011] To avoid contact between the two sinusoidal curved panels, the cell structure must satisfy the following relationship:

[0012] L > 4A;

[0013] Where L is the length of the upper and lower plates, and A is the amplitude of the sine function.

[0014] Analyzing the deformation process of a single foam-filled sinusoidal negative Poisson's ratio cell structure, according to the law of conservation of energy, during the compression process, the energy generated by the work done by the external force is dissipated through three parts: the plasticity E of the sinusoidal negative Poisson's ratio structure... str The foam itself consumes energy E foam The energy consumed by the interaction between the foam and the structure is E. inter This can be represented as follows:

[0015] FΔy=E str +E foam +E inter

[0016] Where F is the external force, Δy is the compressive displacement of the structure, and E str For the sine-negative Poisson's ratio structural plasticity, E foam E is the energy consumed by the compression of the foam itself. inter Energy is consumed by the interaction between the foam and the structure.

[0017] Unfilled structural plasticity E str The plastic hinge formed between the curved and flat panels can be calculated using a sinusoidal function:

[0018]

[0019] Where Y is the out-of-plane width of the array structure, t is the plate thickness excluding the upper and lower plates, Δy is the compressive displacement of the structure, and σ is the displacement of the structure under pressure. s T is the yield strength of the matrix material of the sinusoidal negative Poisson's ratio structure, T is the period of the sinusoidal function, and A is the amplitude of the sinusoidal function.

[0020] Energy consumption E during foam compression foam It can be represented as:

[0021] E foam =σ f Y(2L-4A)

[0022] Where, σ f Let Y be the yield strength of the foam, Y be the width of the array structure outside the plane, L be the length of the upper and lower plates, and A be the amplitude of the sine function.

[0023] The strengthening effect of the foam on the structure is transformed into applying a uniformly distributed load, the magnitude of which is the yield strength σ of the foam, to the sinusoidal curved panel. f The work done by a uniformly distributed load on the sinusoidal curved panel during deformation is the energy dissipated by the interaction between the foam and the structure, E. inter :

[0024]

[0025] Where, σ f Let Y be the yield strength of the foam, Y be the out-of-plane width of the array structure, A be the amplitude of the sinusoidal function, and T be the period of the sinusoidal function. It represents the angle of plastic rotation.

[0026] The external force F can be calculated using the above formula. When the energy is obtained by integrating the force with respect to the displacement, the integral displacement is selected from 0 to 0.1T. Then the plateau stress σ of the foam-filled sinusoidal negative Poisson's ratio structure is... P It can be represented as:

[0027]

[0028] Where t is the plate thickness excluding the upper and lower plates, L is the length of the upper and lower plates, and σ is the thickness of the plate. f σ represents the yield strength of the foam. s T is the yield strength of the matrix material of the sinusoidal negative Poisson's ratio structure, T is the period of the sinusoidal function, and A is the amplitude of the sinusoidal function.

[0029] The lengths L of the upper and lower plates, the thickness t of the plates excluding the upper and lower plates, and the yield strength σ of the foam. f and the yield strength σ of the matrix material s The values ​​of the four parameters mainly depend on the manufacturing process or material selection. Their variations do not alter the dominant control of amplitude A and period T over the platform stress; therefore, they are non-core parameters and can be prioritized for determination. After fixing the non-core parameters, the platform stress σ can be obtained. P Regarding the implicit equations for amplitude A and period T, the stress contour curves of the AT platform are further obtained through parameter scanning and interpolation fitting. These curves represent all conditions that satisfy the target platform stress σ. P The set of amplitude A and period T; then select the amplitude A and period T according to the platform stress value required by the application scenario.

[0030] The sinusoidal negative Poisson's ratio structure is prepared using 3D printing technology. The 3D printing material is selected from metals or highly polar polymers to avoid the material reacting with isocyanates.

[0031] This invention provides a design method for a foam-filled sinusoidal negative Poisson's ratio structure, the specific steps of which are as follows:

[0032] (1) Determine the stress σ of the foam-filled sinusoidal negative Poisson's ratio structural platform according to the requirements of different usage scenarios. P .

[0033] (2) Prioritize determining non-core parameters: plate thickness t (excluding the upper and lower plates), length L of the upper and lower plates, yield strength of the foam, and yield strength of the matrix material of the sinusoidal negative Poisson's ratio structure.

[0034] (3) Based on the following sine curve parameters A and T and the plateau stress σ of the foam-filled sinusoidal negative Poisson's ratio structure, P The explicit mathematical relationships are used to construct the AT platform stress contour curve Γ. The AT platform stress contour curve Γ represents all curves that satisfy the target platform stress σ. P The set of amplitude A and period T;

[0035]

[0036] Where t is the plate thickness excluding the upper and lower plates, L is the length of the upper and lower plates, and σ is the thickness of the plate. f σ represents the yield strength of the foam. s T is the yield strength of the matrix material of the sinusoidal negative Poisson's ratio structure, T is the period of the sinusoidal function, and A is the amplitude of the sinusoidal function.

[0037] (4) Under the premise of ensuring that the sinusoidal function curved panels on both sides do not interfere, determine the range of values ​​for the period T of the sinusoidal function according to the installation space constraints, and then select the amplitude A and period T on the stress isopleth curve Γ of the AT platform.

[0038] (5) Prepare a foam-filled sinusoidal negative Poisson's ratio structure based on the parameters determined above.

[0039] This invention discloses the following steps for preparing a foam-filled sinusoidal negative Poisson's ratio structure:

[0040] Step 1: Fabricate a sinusoidal negative Poisson's ratio structure using 3D printing technology;

[0041] Step 2: Mix the prepared isocyanate and polyether in a 1:1 mass ratio foam solution and stir thoroughly for 20-30 seconds.

[0042] Step 3: After the foam solution turns white, quickly pour it into a rectangular mold, place the sinusoidal negative Poisson's ratio structure into the mold and press gently to allow the foam to fully expand and completely fill the structure.

[0043] Step 4: Let the sample stand at room temperature for half an hour, remove the cured sample, cut off the excess polyurethane foam, and sand both ends of the sample with sandpaper to obtain a foam-filled sinusoidal negative Poisson's ratio structure.

[0044] Compared with the prior art, the beneficial effects of this invention are as follows:

[0045] (1) The foam-filled sinusoidal negative Poisson's ratio structure designed in this invention, based on the inner hexagonal structure, replaces the concave straight plates on both sides with sinusoidal curved panels with continuously varying curvature, thus improving the stress concentration problem caused by geometric abrupt changes during the deformation of the straight plates. When subjected to vertical loads, the structure mainly absorbs energy through bending deformation towards the center of the structure via the sinusoidal curved panels on both sides, exhibiting a significant negative Poisson's ratio effect overall. Due to the negative Poisson's ratio effect of the structure, the filled polyurethane foam is compressed in the horizontal direction while being compressed in the vertical direction, thus entering densification earlier and greatly increasing the plateau stress of the filled structure. At the same time, after filling with polyurethane foam, the negative Poisson's ratio structure achieves integration, reducing brittle fracture of the cell walls on both sides and improving the stability of energy absorption.

[0046] (2) The foam filling method disclosed in this invention uses liquid foaming for filling, which can perfectly fit complex structures, and is especially suitable for sinusoidal negative Poisson's ratio structures with curved panels on both sides. During the foam expansion process, pressure is applied to the cell wall, causing some liquid polyurethane to penetrate into the rough surface of the cell wall to achieve mechanical interlocking, so that the connection between the foam and the cell wall can be achieved without adhesives.

[0047] (3) This invention provides an analytical formula for the plateau stress of a foam-filled sinusoidal negative Poisson's ratio structure, which facilitates rapid assessment of the structure's load-bearing capacity or targeted optimization of its energy absorption characteristics. The foam-filled sinusoidal negative Poisson's ratio structure design method provided by this invention enables precise and controllable design of the structural plateau stress. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of a single cell structure of the sinusoidal negative Poisson's ratio structure of the present invention;

[0049] Figure 2 This is a schematic diagram of the planar parameters of a single cell structure of the sinusoidal negative Poisson's ratio structure of the present invention;

[0050] Figure 3 This is a schematic diagram of the sinusoidal negative Poisson's ratio structure of the present invention;

[0051] Figure 4 This is a schematic diagram of the foam-filled sinusoidal negative Poisson's ratio structure of the present invention;

[0052] Figure 5 The image shows the platform stress contour line Γ of the foam-filled sinusoidal negative Poisson's ratio structure in Embodiment 1 of the present invention when the platform stress value of the sinusoidal negative Poisson's ratio structure is 2.28 MPa in the AT coordinate system.

[0053] Figure 6 This is a schematic diagram of the deformation process of the foam-filled sinusoidal negative Poisson's ratio structure under quasi-static compression in Embodiment 1 of the present invention;

[0054] Figure 7 This is a comparison of the stress-strain curves of the foam-filled sinusoidal negative Poisson's ratio structure, the sinusoidal negative Poisson's ratio structure, and the traditional inner hexagonal structure under quasi-static compression when the relative density of the structures is the same.

[0055] Figure 8 This is a comparison of the specific energy absorption-strain curves of the foam-filled sinusoidal negative Poisson's ratio structure of Example 1 of the present invention, the sinusoidal negative Poisson's ratio structure, and the traditional inner hexagonal structure under quasi-static compression, when the relative density of the structures is the same.

[0056] Figure 9 These are the contour lines of stress at different platforms in the AT coordinate system for the foam-filled sinusoidal negative Poisson's ratio structure of Embodiment 2 of the present invention.

[0057] The figures in the attached diagram are labeled as follows: 1-Upper plate; 2-Lower plate; 3-Left sine function curved plate; 4-Right sine function curved plate; 5-Left connecting plate; 6-Right connecting plate; 7-Foam. Detailed Implementation

[0058] The present invention will be further described below with reference to the accompanying drawings and embodiments. These descriptions are for illustrative purposes only and are not intended to limit the scope of the invention.

[0059] It should be noted that, Figure 3 and Figure 4 The 4x4 structure given is the structure used for simulation and experimental research in this invention, and is not the number of cells limited by this invention.

[0060] Example 1

[0061] Combination Figures 1-4 This embodiment provides a foam-filled sinusoidal negative Poisson's ratio structure, comprising an array structure of multiple interconnected cell structures arranged horizontally and vertically, and foam filling the structural voids. Each cell structure consists of an upper plate 1, a lower plate 2, a left sinusoidal curved plate 3, a right sinusoidal curved plate 4, a left connecting plate 5, and a right connecting plate 6. Each cell structure is horizontally connected via the two transverse connecting plates 5 and 6, and vertically connected to the upper plate 1 and lower plate 2 of adjacent cell structures. The upper and lower plates have a length of L, the sinusoidal curved plate has an amplitude of A and a period of T, the horizontal connecting plate has a length of L / 2, the upper and lower plates have a thickness of t / 2, and the remaining plates have a thickness of t. The array structure obtained by the horizontal and vertical arrangement has a length of X, an out-of-plane width of Y, and a height of Z.

[0062] The expression for the sine function curve panel function on the right side of the cell structure is as follows:

[0063]

[0064] Where A is the amplitude of the sine function, L is the length of the upper and lower plates, and T is the period of the sine function.

[0065] The amplitude A and the period T satisfy the following relationship:

[0066]

[0067] Where t is the plate thickness excluding the upper and lower plates, L is the length of the upper and lower plates, and σ is the thickness of the plate. f σ represents the yield strength of the foam. s T is the yield strength of the matrix material of the sinusoidal negative Poisson's ratio structure, T is the period of the sinusoidal function, and A is the amplitude of the sinusoidal function.

[0068] The foam-filled sinusoidal negative Poisson's ratio structure in this embodiment is used as a collision buffer device for an intelligent home robot. The target platform stress of the structure is 2.28 MPa. The non-core parameters are selected as follows: L is 10 mm, t is 1 mm, and the matrix material of the foam-filled sinusoidal negative Poisson's ratio structure is high-toughness nylon PA11. s The strength is 43 MPa, and the foam material is rigid polyurethane with a density of 80 kg / m³. 3 , σ f It is 0.48 MPa.

[0069] Based on the explicit mathematical relationship between the amplitude A and period T of the sinusoidal curve and the plateau stress of the sinusoidal negative Poisson's ratio structure, a plateau stress contour line Γ is constructed. This curve represents the set of all amplitudes A and periods T that satisfy the target plateau stress, such as... Figure 5As shown. Considering the installation space limitations, a period T of 12 mm is selected, and the amplitude A can be determined to be 1.3 mm on the contour line. At this time, X = 60 mm, Y = 40 mm, and Z = 52 mm.

[0070] Specifically, quasi-static compression simulation of a foam-filled sinusoidal negative Poisson's ratio structure was performed using the finite element simulation software LSDYNA.

[0071] according to Figure 6 As shown in the figure, this embodiment provides a schematic diagram of the deformation process of the above-mentioned foam-filled sinusoidal negative Poisson's ratio structure under quasi-static compression. When the strain is 0.1, the sinusoidal curved panel undergoes bending deformation, and the structure exhibits lateral shrinkage. As the compression displacement increases, the shrinkage from the obliquely symmetrical positions on the left and right sides towards the middle is more significant, demonstrating obvious negative Poisson's ratio performance.

[0072] To investigate the mechanical properties of the foam-filled sinusoidal negative Poisson's ratio structure proposed in this invention, a quasi-static compression test was conducted on the structure. The specific experimental steps are as follows:

[0073] Step 1: Printing using selective laser sintering technology, such as... Figure 3 The sinusoidal negative Poisson's ratio structure shown is printed using high-toughness nylon PA11. The prepared isocyanate and polyether mixture is mixed at a 1:1 mass ratio and stirred thoroughly for 20-30 seconds. After the solution turns white, the mixture is quickly poured into a rectangular mold. The sinusoidal negative Poisson's ratio structure is then placed into the mold and gently pressed to allow the foam to fully expand and completely fill the structure. After standing at room temperature for half an hour, the cured sample is removed, excess polyurethane foam is trimmed, and both ends of the sample are sanded to obtain the foam-filled sinusoidal negative Poisson's ratio structure.

[0074] Step 2: Place the sample onto the fixed pressure plate of the electronic universal testing machine. The loading rate of the loading head is 5 mm / min, and the total downward displacement is 36 mm.

[0075] Step 3: The compressive load and compressive displacement of the structure are collected by force sensors and displacement sensors, respectively, to obtain the stress-strain curve of the foam-filled sinusoidal negative Poisson's ratio structure. Numerical integration of the stress-strain curve and division by the relative density of the structure yields the specific energy absorption-strain curve. The experimentally obtained curves are shown in [Figure number missing]. Figure 7 and Figure 8 .

[0076] The experimentally measured stress value of the structural platform was 2.208 MPa, and the target stress value was 2.28 MPa, with a deviation of 3.2%. The experimental results and the target results are in good agreement, indicating that the foam-filled sinusoidal negative Poisson's ratio structural design method provided by this invention can achieve precise and controllable design of the structural platform stress.

[0077] To illustrate the improvement of the load-bearing capacity and energy absorption effect of the existing inner hexagonal structure by the present invention, this embodiment provides stress-strain curves and specific energy absorption curves for three negative Poisson's ratio structures with the same relative density, such as... Figure 7 and Figure 8 As shown. The thickness of the inner hexagonal structure is 1.18 mm, the thickness of the sinusoidal negative Poisson's ratio structure is 1.23 mm, the thickness of the foam-filled sinusoidal negative Poisson's ratio structure is 1 mm, and the density of the filling foam is 80 kg / m³. 3 All three structures weigh 40.7g. As can be seen from the figure, the sinusoidal negative Poisson's ratio structure obtained by replacing the concave straight plates on both sides of the inner hexagonal structure with sinusoidal curved plates has improved plateau stress and specific energy absorption. The foam-filled sinusoidal negative Poisson's ratio structure of the present invention has a significantly improved plateau stress and specific energy absorption due to the deformation synergy and mechanical coupling between the foam and the structure.

[0078] Example 2

[0079] This embodiment provides a design method for a foam-filled sinusoidal negative Poisson's ratio structure under different stress requirements. The application scenarios are divided into the following four types: medical equipment cushioning structure (target platform stress 10MPa); drone anti-fall structure (target platform stress 20MPa); industrial cushioning pad (target platform stress 30MPa); and automotive energy-absorbing box (target platform stress 40MPa). Non-core parameters are selected as follows: L is 12mm, t is 1mm, the matrix material of the foam-filled sinusoidal negative Poisson's ratio structure is ABS plastic, and σ... s The strength is 62 MPa, and the foam material is rigid polyurethane with a density of 200 kg / m³. 3 , σ f It is 5 MPa.

[0080] After fixing the non-core parameters, by solving the implicit equations of the target platform stress with respect to amplitude A and period T, contour maps from 10 MPa to 40 MPa were generated in the AT coordinate system, as shown below. Figure 9 As shown, by selecting amplitude A and period T on the corresponding contour lines, the structure can be adapted to multiple scenarios from low stress to high stress. When the application scenario is a medical equipment cushioning structure, the period T is 5.1 mm and the amplitude A is 0.478 mm; when the application scenario is a drone anti-fall structure, the period T is 19.7 mm and the amplitude A is 1.68 mm; when the application scenario is an industrial cushioning pad, the period T is 28.5 mm and the amplitude A is 1 mm; when the application scenario is an automotive energy-absorbing box, the period T is 37.16 mm and the amplitude A is 2 mm.

[0081] The above description describes specific embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and extensions without departing from the actual situation and conforming to the design principles. These improvements and extensions should also be considered as references to the content of the present invention and should be considered within the scope of protection of the present invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included in the present invention.

Claims

1. A foam-filled sinusoidal negative Poisson's ratio structure, characterized in that, A sinusoidal negative Poisson's ratio structure obtained by arranging multiple cell structures horizontally and vertically is used as a framework, and foam is filled inside the framework; the cell structure includes an upper plate, a lower plate, two sinusoidal function curved plates on both sides, and two horizontally connected plates on the outer side of the curved plates; each cell structure is connected horizontally through the two horizontally connected plates on both sides, and vertically the upper plate and lower plate are connected to the upper plate and lower plate of the adjacent cell structure.

2. The foam-filled sinusoidal negative Poisson's ratio structure according to claim 1, characterized in that, For each cell structure, with the cell center as the origin O, and the x-axis along the length of the transverse connecting plate and the y-axis along the height of each cell, the expression for the sine function of the cell structure on the curved panel is as follows: Where A is the amplitude of the sine function, L is the length of the upper and lower plates, and T is the period of the sine function.

3. The foam-filled sinusoidal negative Poisson's ratio structure according to claim 2, characterized in that, The length of the horizontal connecting plate is L / 2, the thickness of the upper and lower plates is t / 2, and the thickness of the plates other than the upper and lower plates is t. Furthermore, to avoid contact between the two sinusoidal curved panels, the relationship between the lengths of the upper and lower plates and the amplitude of the sinusoidal function should satisfy: L > 4A.

4. The foam-filled sinusoidal negative Poisson's ratio structure according to claim 1, characterized in that, By analyzing a single foam-filled sinusoidal negative Poisson's ratio cell structure, the sinusoidal function amplitude A, the sinusoidal function period T, and the plateau stress σ of the foam-filled sinusoidal negative Poisson's ratio structure were obtained. P The relationship between them is: In the formula, σ P The plateau stress of the foam-filled sinusoidal negative Poisson's ratio structure is given by: t, plate thickness excluding the upper and lower plates; x, structural compressive displacement; L, and the lengths of the upper and lower plates; σ. f σ represents the yield strength of the foam. s Let T be the yield strength of the sinusoidal negative Poisson's ratio structure, T be the vertical length of the sinusoidal function curved panel, and A be the amplitude of the sinusoidal function. The lengths L of the upper and lower plates, the thickness t of the plates excluding the upper and lower plates, and the yield strength σ of the foam. f The yield strength σ of the sinusoidal negative Poisson's ratio structure s The values ​​of the four parameters depend on the manufacturing process or material selection, thus yielding the plateau stress σ of the foam-filled sinusoidal negative Poisson's ratio structure. P Regarding the implicit equations for amplitude A and period T, the AT platform stress contour curve Γ is further obtained through parameter scanning and interpolation fitting; then, amplitude A and period T are selected according to the platform stress value required for the application scenario.

5. The foam-filled sinusoidal negative Poisson's ratio structure according to claim 1, characterized in that, The sinusoidal negative Poisson ratio structure is made of metal or highly polar polymer.

6. The foam-filled sinusoidal negative Poisson's ratio structure according to claim 1, characterized in that, The filling foam is low-density rigid polyurethane.

7. A design method for a foam-filled sinusoidal negative Poisson's ratio structure, the specific steps of which are as follows: (1) Determine the plateau stress σ of the foam-filled sinusoidal negative Poisson's ratio structure according to the requirements of different application scenarios. P ; (2) Prioritize the determination of non-core parameters: plate thickness t (excluding the upper and lower plates), length L of the upper and lower plates, yield strength of the foam, and yield strength of the sinusoidal negative Poisson's ratio structure. (3) Based on the following sine curve parameters A and T and the plateau stress σ of the foam-filled sinusoidal negative Poisson's ratio structure, P The explicit mathematical relationships are used to construct the AT platform stress contour curve Γ. The AT platform stress contour curve Γ represents all curves that satisfy the target platform stress σ. P The set of amplitude A and period T; Plateau stress σ of foam-filled sinusoidal negative Poisson's ratio structure P The analytical expression is: in, t is the plate thickness excluding the top and bottom plates, L is the length of the top and bottom plates, and σ is the thickness of the plate. f σ represents the yield strength of the foam. s Let T be the yield strength of the sinusoidal negative Poisson's ratio structure, T be the period of the sinusoidal function, and A be the amplitude of the sinusoidal function. (4) Under the premise of ensuring that the sinusoidal function curved panels on both sides do not interfere, determine the range of values ​​for the period T of the sinusoidal function according to the installation space constraints, and then select the amplitude A and period T on the stress isopleth curve Γ of the AT platform. (5) Prepare a foam-filled sinusoidal negative Poisson's ratio structure based on the parameters determined above.

8. A method for preparing a foam-filled sinusoidal negative Poisson's ratio structure, characterized in that, The specific steps are as follows: Step 1: Fabricate a sinusoidal negative Poisson's ratio structure using 3D printing technology; Step 2: Mix the prepared isocyanate and polyether in a 1:1 mass ratio foam solution and stir thoroughly for 20-30 seconds. Step 3: After the foam solution turns white, quickly pour it into a rectangular mold, place the sinusoidal negative Poisson's ratio structure into the mold and press gently to allow the foam to fully expand and completely fill the structure. Step 4: Let the sample stand at room temperature for half an hour, remove the cured sample, cut off the excess polyurethane foam, and sand both ends of the sample with sandpaper to obtain a foam-filled sinusoidal negative Poisson's ratio structure.

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