Foam filling gradient bionic structure with negative Poisson's ratio effect and manufacturing method

Abstract

The invention discloses a foam-filled gradient bionic structure with a negative Poisson's ratio effect. The foam-filled gradient bionic structure comprises an external negative Poisson's ratio pipe structure and an internal filling material, the pipe structure is formed by splicing a plurality of variable cross-section short pipes in the vertical direction; the section of the variable-section short pipe is square, the pipe diameter is gradually reduced from the two ends to the middle, and cross-shaped restraining ribs are arranged at the top and the bottom of the pipe. And the width of the minimum section of the middle part of the variable-section short pipe is gradually reduced from bottom to top along with the number of layers. The base material of the pipe structure is stainless steel, and the filling material is foam concrete. Based on a brand new negative Poisson's ratio pipe design structure, the negative Poisson's ratio pipe is combined with the foam concrete, the negative Poisson's ratio effect of the negative Poisson's ratio pipe and the good energy absorption characteristic of the foam concrete are utilized, and the defect that the negative Poisson's ratio pipe is low in strength is overcome; and the energy absorption performance and the mechanical response stability of the foam filling pipe are improved.

Description

Technical Field

[0001] The present invention relates to the intersection of new materials, new structures and composite materials, and in particular to a foam-filled gradient bionic structure with a negative Poisson's ratio effect and a manufacturing method thereof. Background Art

[0002] A foam-filled tube is a composite tube that is filled with foam material to enhance its structural performance. With the continuous deepening of research on thin-walled tubes, researchers have found that filling the interior of metal tubes with lightweight foam materials can significantly change the deformation mechanism of the structure. The foam filler not only supports the tube wall and delays buckling, but also absorbs a large amount of energy through its own compression deformation. Foam-filled tubes play an important role in many industrial fields due to their unique lightweight, high energy absorption and multifunctional properties. In the field of transportation, it is widely used in automotive anti-collision structures and aerospace components. In the field of construction and infrastructure, foam-filled tubes provide innovative solutions for seismic design and pipeline engineering. In earthquake-prone areas, buildings use foam-filled steel pipes as energy-absorbing supports to effectively consume earthquake energy through plastic deformation.

[0003] Foam concrete is a lightweight foam material made by introducing stable bubbles into a cement-based paste. Compared to traditional concrete, it has advantages such as low density, good energy absorption and buffering capacity, and easy preparation. Foam concrete has many applications in the field of protection. In military protection projects, the porous structure of foam concrete can effectively attenuate explosion shock waves and can be used for explosion-proof walls of military bases and ammunition depots. In the protection of transportation infrastructure, it can be used as a foam concrete buffer layer in bridge piers to absorb the impact energy of ships or vehicles. Traditional foam-filled tubes are prone to large initial peak stresses when subjected to external loads, and the mechanical response will produce large fluctuations, causing unpredictable damage to the protected structure. In addition, the tube structure and the internal foam material do not effectively synergize.

[0004] Negative Poisson's ratio tubes are a special type of three-dimensional structure. When compressed, these structures contract inward, exhibiting excellent energy absorption, dent resistance, and shear resistance. Consequently, these structures have broad application prospects in aerospace, biomedicine, intelligent equipment, and construction engineering. Conventional negative Poisson's ratio tubes are constructed using coordinate transformations of negative Poisson's ratio cells, resulting in a porous surface and significantly weakening the overall strength of the tube. Summary of the Invention

[0005] Purpose of the Invention: The first purpose of the present invention is to provide a foam-filled gradient biomimetic structure with a negative Poisson's ratio effect. This structure is based on a new negative Poisson's ratio tube design and combines the negative Poisson's ratio tube with foamed concrete. By utilizing the negative Poisson's ratio effect of the negative Poisson's ratio tube itself and the good energy absorption characteristics of foamed concrete, the present invention overcomes the disadvantage of low strength of the negative Poisson's ratio tube and improves the energy absorption performance and mechanical response stability of the foam-filled tube. The second object is to provide a method for manufacturing the above-mentioned foam-filled gradient bionic structure with negative Poisson's ratio effect.

[0006] Technical solution: The foam-filled gradient biomimetic structure with negative Poisson's ratio effect proposed in the present invention includes an external negative Poisson's ratio tube structure and an internal filling material; The pipe structure is composed of a plurality of short pipes of variable cross-sections spliced ​​in the vertical direction; The cross section of the variable cross section short tube is square, the tube diameter gradually decreases from both ends to the middle, and cross restraining ribs are provided on the top and bottom of the tube; The minimum cross-sectional width l in the middle of the variable cross-sectional short tube n It shows a decreasing trend from bottom to top with the number of layers, and n is the number of layers where the variable-section short pipe is located.

[0007] The base material of the pipe structure is stainless steel, and the filling material is foam concrete.

[0008] Furthermore, the relationship between the height h of the variable cross-section short tube and the width l0 of the maximum cross-section satisfies: 0.7≤h / l0≤1.1.

[0009] Furthermore, the minimum cross-sectional width of the variable cross-sectional short tube is l n The relationship with the maximum cross-sectional width l0 satisfies: 0.5≤l n / l0≤0.9.

[0010] Furthermore, the difference d between the widths of the minimum cross-sections of adjacent short tubes of variable cross-section in the tube structure is d=l n -l n+1 The relationship with the width l0 satisfies: 5≤l0 / d≤20.

[0011] Furthermore, the relationship between the wall thickness t and the maximum cross-sectional width l0 of the tube structure satisfies: 13.33≤l0 / t≤26.67.

[0012] Furthermore, the width l of the cross-restraint rib in the variable cross-section short tube is r The relationship with the width l0 of the maximum section satisfies: 2≤l0 / l r ≤8; the thickness of the cross-restraint rib in the variable cross-section short tube t r The relationship with the width l0 of the maximum section satisfies: 10≤l0 / t r ≤20.

[0013] Furthermore, the relationship between the overall height H of the tube structure and the maximum cross-sectional width l0 satisfies: 2.19≤H / l0≤3.43.

[0014] Correspondingly, the present invention also provides a method for manufacturing the above-mentioned foam-filled gradient biomimetic structure with negative Poisson's ratio effect, comprising the following steps: S1. Design the relevant dimensions of the gradient bionic tube, including the maximum cross-sectional width l0 and the minimum cross-sectional width l n , height h, difference d between the widths of the minimum cross sections of adjacent short tubes, wall thickness t, width l of the cross restraining ribs r , the thickness of the cross restraining rib t r , the overall height H of the structure; S2. Using 3D printing technology and stainless steel as the base material, a gradient bionic tube with negative Poisson's ratio effect was prepared; S3, preparing foamed concrete using sulphoaluminium silicate cement, animal protein foaming agent and water as raw materials; S4, pouring the evenly stirred foam concrete into a mold, and inserting the prepared pipe structure into the mold, so that the foam concrete slurry in the mold is fully filled into the pipe; S5, after the foam concrete is initially set, the foam concrete in the mold is demoulded and excess foam concrete is removed, leaving only the foam concrete inside the tube; S6. Cure until the foam concrete reaches its maximum strength.

[0015] In S3, the animal protein foaming agent is first diluted at a ratio of 1:35 and foamed into foam using a foaming machine; sulphoaluminium silicate cement powder is then stirred into cement paste at a water-cement ratio of 0.3; a certain amount of foam is weighed and added to the cement paste and stirred continuously until the foam and cement paste are fully mixed; Among them, the mass ratio of sulfoaluminum silicate cement powder, water and foam is 0.7112:0.2133:0.0755.

[0016] The key to producing the negative Poisson's ratio effect in the present invention lies in the design of the external negative Poisson's ratio tubes, ensuring that the smaller cross-section of the variable-cross-section short tubes is significantly smaller than the larger cross-section, resulting in a negative Poisson's ratio effect for the external tube structure. Furthermore, ensuring that the smaller cross-section of each variable-cross-section short tube in the tube structure exhibits a significant downward trend from bottom to top can result in a more stable deformation mode for the overall structure. Furthermore, because foamed concrete is an energy-absorbing material with a positive Poisson's ratio, when the overall structure is subjected to pressure, the external negative Poisson's ratio tubes contract inward while the internal foamed concrete expands outward, generating a large interaction force between the two, resulting in excellent energy absorption properties.

[0017] Beneficial effect: Compared with the prior art, the present invention has the significant advantage of exhibiting good mechanical properties.

[0018] Conventional negative Poisson's ratio tubes are created by transforming the coordinates of negative Poisson's ratio cells, which makes the tube surface porous and significantly weakens the overall strength of the tube. The method of the present invention can avoid the porous structure of the tube surface and ensure the negative Poisson's ratio effect and strength of the structure. In addition, traditional foam-filled tubes are prone to generating large initial peak stresses when subjected to external loads, and the mechanical response will produce large fluctuations, causing unpredictable damage to the protected structure. Furthermore, the tube structure and the internal foam material do not effectively synergize. The foam concrete-filled gradient bionic tube designed by the present invention, which has a negative Poisson's ratio effect, will shrink inward and squeeze the internal foam concrete under pressure, resulting in higher energy absorption characteristics. Furthermore, the gradient design allows the structure to exhibit more stable deformation modes and mechanical responses when under pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the overall structural diagram of the present invention; Figure 2 Schematic diagram of the variable cross-section short tube structure; Figure 3 It is the cross-sectional view of the short tube with variable cross-section; Figure 4 This is a schematic diagram of the present invention. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] like Figure 1-3 As shown, a foam-filled gradient biomimetic structure with a negative Poisson's ratio effect includes an external negative Poisson's ratio tube structure 1 and an internal filling material 2.

[0022] The base material of the pipe structure is stainless steel and the filling material is foam concrete.

[0023] The pipe structure is composed of multiple short pipes with variable cross-sections spliced ​​in the vertical direction.

[0024] The cross section of the variable cross section short tube is square, the diameter of the tube gradually decreases from both ends to the middle, and cross restraining ribs 3 are provided on the top and bottom of the tube.

[0025] Minimum cross-sectional width l in the middle of the variable cross-sectional short tube n It shows a decreasing trend from bottom to top with the number of layers, and n is the number of layers where the variable-section short pipe is located.

[0026] The relationship between the height h of the variable cross-section short tube and the width l0 of the maximum cross-section satisfies: 0.7≤h / l0≤1.1.

[0027] Minimum cross-section width of variable cross-section short pipe l n The relationship with the maximum cross-sectional width l0 satisfies: 0.5≤l n / l0≤0.9.

[0028] The difference d between the widths of the minimum cross-sections of adjacent short tubes with variable cross-sections in the tube structure, d=l n -l n+1 The relationship with the width l0 satisfies: 5≤l0 / d≤20.

[0029] The relationship between the wall thickness t of the pipe structure and the maximum cross-sectional width l0 satisfies: 13.33≤l0 / t≤26.67.

[0030] The width l of the cross restraint rib in the variable cross-section short tube r The relationship with the width l0 of the maximum section satisfies: 2≤l0 / l r ≤8; the thickness of the cross-restraint rib in the variable cross-section short tube t r The relationship with the width l0 of the maximum section satisfies: 10≤l0 / t r ≤20.

[0031] The relationship between the overall height H of the tube structure and the maximum cross-sectional width l0 satisfies: 2.19≤H / l0≤3.43.

[0032] like Figure 4 As shown, the method for manufacturing the foam-filled gradient biomimetic structure with negative Poisson's ratio effect comprises the following steps: S1. Design the relevant dimensions of the external gradient bionic tube according to the actual size of the protected structure, including the maximum cross-sectional width l0 and the minimum cross-sectional width l n , height h, difference d between the widths of the minimum cross sections of adjacent short tubes, wall thickness t, width l of the cross restraining ribs r , the thickness of the cross restraining rib t r , the overall height H of the structure; S2. Using 3D printing technology and stainless steel as the base material, a gradient bionic tube with negative Poisson's ratio effect was prepared; S3, preparing foamed concrete using sulphoaluminium silicate cement, animal protein foaming agent and water as raw materials; First, dilute the animal protein foaming agent at a ratio of 1:35 and foam it into foam using a foaming machine; then mix the sulphoaluminium silicate cement powder into a cement paste at a water-cement ratio of 0.3; weigh a certain amount of foam and add it to the cement paste and continue stirring until the foam and cement paste are fully mixed; Among them, the mass ratio of sulphoaluminium silicate cement powder, water and foam is 0.7112:0.2133:0.0755 S4, pouring the evenly stirred foam concrete into a mold, and inserting the prepared pipe structure into the mold, so that the foam concrete slurry in the mold is fully filled into the pipe; S5, after 50 minutes, when the foam concrete is initially set, the foam concrete in the mold is demoulded and the excess foam concrete is removed, leaving only the foam concrete inside the tube; S6. After 2 days of curing, the foamed concrete reaches its maximum strength.

Claims

1. A foam-filled gradient biomimetic structure with a negative Poisson's ratio effect, characterized by: It includes an external negative Poisson's ratio tube structure (1) and an internal filling material (2); The pipe structure is composed of a plurality of short pipes of variable cross-sections spliced ​​in the vertical direction; The cross section of the variable cross section short tube is square, the tube diameter gradually decreases from both ends to the middle, and cross restraining ribs (3) are provided on the top and bottom of the tube; The minimum cross-sectional width l in the middle of the variable cross-sectional short tube n It shows a decreasing trend from bottom to top with the number of layers, and n is the number of layers where the variable-section short pipe is located.

2. The foam-filled gradient biomimetic structure with negative Poisson's ratio effect according to claim 1, characterized in that: The base material of the pipe structure is stainless steel, and the filling material is foam concrete.

3. The foam-filled gradient biomimetic structure with negative Poisson's ratio effect according to claim 1, characterized in that: The relationship between the height h of the variable cross-section short tube and the width l0 of the maximum cross-section satisfies: 0.7≤h / l0≤1.

1.

4. The foam-filled gradient biomimetic structure with negative Poisson's ratio effect according to claim 1, characterized in that: The minimum cross-sectional width l of the variable cross-sectional short tube n The relationship with the maximum cross-sectional width l0 satisfies: 0.5≤l n / l0≤0.

9.

5. The foam-filled gradient biomimetic structure with negative Poisson's ratio effect according to claim 1, characterized in that: The difference d between the widths of the minimum cross sections of adjacent short tubes of variable cross sections in the tube structure is d=l n -l n+1 The relationship with the width l0 satisfies: 5≤l0 / d≤20.

6. The foam-filled gradient biomimetic structure with negative Poisson's ratio effect according to claim 1, characterized in that: The relationship between the wall thickness t and the maximum cross-sectional width l0 of the tube structure satisfies: 13.33≤l0 / t≤26.

67.

7. The foam-filled gradient biomimetic structure with negative Poisson's ratio effect according to claim 1, characterized in that: The width l of the cross-restraint rib in the variable cross-section short tube r The relationship with the width l0 of the maximum section satisfies: 2≤l0 / l r ≤8; the thickness of the cross-restraint rib in the variable cross-section short tube t r The relationship with the width l0 of the maximum section satisfies: 10≤l0 / t r ≤20.

8. The foam-filled gradient biomimetic structure with negative Poisson's ratio effect according to claim 1, characterized in that: The relationship between the overall height H of the tube structure and the maximum cross-sectional width l0 satisfies: 2.19≤H / l0≤3.

43.

9. The method for manufacturing the foam-filled gradient biomimetic structure with negative Poisson's ratio effect according to claim 1, characterized in that: The following steps are involved: S1. Design the relevant dimensions of the gradient bionic tube, including the maximum cross-sectional width l0 and the minimum cross-sectional width l n , height h, difference d between the widths of the minimum cross sections of adjacent short tubes, wall thickness t, width l of the cross restraining ribs r , the thickness of the cross restraining rib t r , the overall height H of the structure; S2. Using 3D printing technology and stainless steel as the base material, a gradient bionic tube with negative Poisson's ratio effect was prepared; S3, preparing foamed concrete using sulphoaluminium silicate cement, animal protein foaming agent and water as raw materials; S4, pouring the evenly stirred foam concrete into a mold, and inserting the prepared pipe structure into the mold, so that the foam concrete slurry in the mold is fully filled into the pipe; S5, after the foam concrete is initially set, the foam concrete in the mold is demoulded and excess foam concrete is removed, leaving only the foam concrete inside the tube; S6. Cure until the foam concrete reaches its maximum strength.

10. The method for manufacturing a foam-filled gradient biomimetic structure with a negative Poisson's ratio effect according to claim 9, characterized in that: In S3, the animal protein foaming agent is first diluted at a ratio of 1:35 and foamed into foam using a foaming machine; sulfoaluminum silicate cement powder is then mixed into a cement paste at a water-cement ratio of 0.3; a certain amount of foam is weighed and added to the cement paste and stirred continuously until the foam and cement paste are fully mixed; Among them, the mass ratio of sulfoaluminum silicate cement powder, water and foam is 0.7112:0.2133:0.0755.

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