Shear thickening fluid and gradient negative Poisson's ratio metamaterial composite impact-resistant energy-absorbing structure

Abstract

The invention discloses a shear thickening fluid and gradient negative Poisson's ratio metamaterial composite impact-resistant energy-absorbing structure, which comprises an upper high-strength aluminum alloy plate, a lower high-strength aluminum alloy plate and a middle multi-layer gradient honeycomb core, the honeycomb core adopts a single reentrant hexagonal structure, and concave angles of each layer are gradually increased layer by layer to realize graded absorption and uniform dispersion of impact energy. The honeycomb units are filled with the shear thickening fluid, the shear thickening fluid is rapidly tackified at a high shear rate in the compression deformation process of the negative Poisson's ratio honeycomb core, and the energy dissipation performance of the composite protection structure is improved through cooperative energy absorption of the gradient negative Poisson's ratio honeycomb structure and the shear thickening dynamic thickening effect. All the layers are tightly connected through a high-strength interface bonding technology, and the overall structure is stable and durable. According to the invention, impact energy transfer is effectively blocked, light weight, simple process and cost optimization are taken into consideration, and the method is suitable for high-impact scenes such as aviation, automobiles and buildings, and has wide market prospects and application values.

Description

Technical Field

[0001] The present application relates to the technical field of composite protective structures, and in particular to a composite anti-impact energy-absorbing structure of a shear thickening fluid and a gradient negative Poisson's ratio metamaterial. Background Art

[0002] In recent years, the requirements for lightweight, high energy consumption and impact resistance in aerospace, vehicle protection and personal protective equipment have been continuously improved. However, traditional protective structures such as typical single-layer honeycomb structures or ordinary metal plates often break or fail due to local stress concentration under high-speed impact loads, making it difficult to achieve effective energy dispersion and absorption.

[0003] Negative Poisson's ratio structures have attracted widespread attention because they can achieve synchronous lateral and longitudinal deformation when subjected to stress. However, a single negative Poisson's ratio honeycomb structure may still experience local failure under high impact conditions. Summary of the invention

[0004] The present application provides a shear thickening fluid and gradient negative Poisson's ratio metamaterial composite impact-resistant energy-absorbing structure, which can be used to solve the technical problem that a single negative Poisson's ratio honeycomb structure is difficult to cope with high impact.

[0005] The present application provides a shear thickening fluid and gradient negative Poisson's ratio metamaterial composite anti-impact energy absorption structure, wherein the composite anti-impact energy absorption structure uses high-strength aluminum alloy plates as upper and lower substrates, respectively, to ensure that the overall structure has sufficient rigidity and load-bearing capacity under both static load and impact load.

[0006] A multi-layer gradient honeycomb core is set between the upper and lower aluminum alloy plates, and a high-strength aluminum alloy material is selected. The honeycomb core includes several layers of single-entry hexagonal honeycomb units. The concave angle of each layer of honeycomb units remains consistent, and the angle difference between different layers is formed by angle gradient design, that is, the concave angle of the upper honeycomb unit is smaller than the concave angle of the lower honeycomb unit, thereby forming a negative Poisson's ratio gradient that increases layer by layer from top to bottom.

[0007] In the design of honeycomb units, by reasonably determining the cell wall thickness t, the length of the oblique support column l, and the length of the horizontal support column g, the negative Poisson's ratio effect is used to make the honeycomb unit shrink in the same direction in the horizontal and vertical directions when under pressure, and the in-plane negative Poisson's ratio v of the honeycomb unit is calculated according to the following formula: 12 :

[0008]

[0009] Among them, v 12 is the in-plane Poisson’s ratio of the honeycomb unit, vs is the Poisson’s ratio of the base material, θ is the concave angle of the honeycomb unit, g is the length of the horizontal support column, and l is the length of the inclined support column.

[0010] By using high-strength interface bonding technologies such as hot pressing, adhesives or metal diffusion welding, the multi-layer gradient honeycomb core is firmly connected to the upper and lower aluminum alloy plates to ensure that the layers of the structure deform in coordination under impact loads to prevent delamination or peeling;

[0011] A shear thickening (STF) fluid is filled inside the honeycomb unit. The fluid maintains a relatively low viscosity at low shear rates, but the viscosity increases rapidly under high shear rates (such as high-speed impact or severe vibration), thereby providing an additional energy dissipation mechanism for the honeycomb structure. The constitutive relation of the shear thickening (STF) fluid is described in the following form:

[0012]

[0013] Where η is the apparent viscosity, η 0 is the yield viscosity, τ 0 is the yield stress, is the shear rate, is the critical shear rate, k is the viscosity index, and n is the power law index. In actual preparation, STF can be uniformly filled into each layer of honeycomb unit by vacuum-assisted injection or impregnation, and the connection between the honeycomb core and the upper and lower plates can be sealed or packaged to prevent STF from leaking or being affected by the environment.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] (1) The present invention fills a multi-layer gradient honeycomb core with a shear thickening fluid so that the impact load is gradually absorbed and dispersed in each layer of honeycomb units. At the same time, the STF's viscosity mutation characteristics at a high shear rate are utilized to further dissipate energy, thereby effectively reducing local stress concentration and preventing the single-layer structure from failing due to excessive impact.

[0016] (2) When subjected to pressure, the negative Poisson's ratio honeycomb unit shrinks synchronously in the lateral and longitudinal directions, significantly enhancing the buffering deformation capacity of the honeycomb core. Combined with the STF thickening effect, it can form a synergistic energy absorption mechanism under high-speed impact conditions, significantly reducing the impact peak and improving the overall protection performance.

[0017] (3) The use of high-strength interface bonding technology ensures a firm connection between the multi-layer honeycomb core and the upper and lower aluminum alloy plates, improving the peeling resistance and durability of the overall structure.

[0018] (4) The overall structural design takes into account both lightweight and simple manufacturing process, which is convenient for large-scale production and has broad application prospects in the fields of protective vehicles, aerospace vehicles, and personal protective equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a first-layer unit cell of a structure according to an embodiment of the present invention;

[0020] Figure 2 Schematic diagram of the second - layer unit cell of the structure of the embodiment of the present invention;

[0021] Figure 3 Schematic diagram of the third - layer unit cell of the structure of the embodiment of the present invention;

[0022] Figure 4 Schematic diagram of the structure of the embodiment of the present invention;

[0023] Figure 5 The figure shows the curve of the Von Mises stress at the center of the bottom plate varying with time when there is a protective structure and when there is no protective structure in this embodiment;

[0024] Figure 6 The figure shows the curve of the vertical displacement at the center of the bottom plate varying with time when there is a protective structure and when there is no protective structure;

[0025] Figure 7 Schematic diagram II of the structure of the embodiment of the present invention. Detailed implementation manners

[0026] To make the objectives, technical solutions, and advantages of the present application clearer, the following will further describe the embodiments of the present application in detail with reference to the accompanying drawings.

[0027] For this purpose, a shear - thickening fluid / gradient negative - Poisson's ratio metamaterial anti - impact composite lightweight protective structure is proposed. By gradually increasing the honeycomb unit angle layer by layer, the impact energy is absorbed in a hierarchical manner, and shear - thickening fluid is filled in the negative - Poisson's ratio structure. The impact deformation of the negative - Poisson's ratio structure will generate a shear action on the shear - thickening fluid, and the shear - thickening fluid rapidly increases its viscosity at a high shear rate, thereby dissipating the impact energy and effectively improving the anti - impact performance of the protective structure.

[0028] A shear - thickening fluid and gradient negative - Poisson's ratio metamaterial composite anti - impact and energy - absorbing structure of the present application. The composite anti - impact and energy - absorbing structure includes upper and lower layers of high - strength aluminum alloy plates and multiple layers of gradient honeycomb cores located between the two layers of high - strength aluminum alloy plates;

[0029] The gradient honeycomb core includes multiple layers of single - re - entry hexagonal honeycomb units. The concave angles of each layer of honeycomb units are the same, the concave angles between different layers are different, and the concave angles increase layer by layer from top to bottom. The material of the multiple - layer gradient honeycomb core is high - strength aluminum alloy, and it is tightly connected to the upper and lower plates through high - strength interface bonding technology;

[0030] The honeycomb unit is filled with shear - thickening (STF) fluid, so that the honeycomb core forces the shear - thickening fluid to rapidly increase its viscosity at a high shear rate during the compression deformation process, thereby realizing the synergistic energy absorption of the gradient negative - Poisson's ratio structure and the shear - thickening dynamic thickening effect, and improving the energy dissipation performance of the composite protective structure.

[0031] Furthermore, the single reentrant hexagonal honeycomb unit is a negative Poisson's ratio structure. When subjected to an impact load, the unit undergoes coupled deformation in the thickness direction and in-plane direction simultaneously to achieve efficient absorption and transmission blocking of impact energy; the honeycomb unit satisfies the following negative Poisson's ratio:

[0032]

[0033] Among them, v 12 is the in-plane Poisson’s ratio of the honeycomb unit, v s is the Poisson's ratio of the base material, t is the cell wall thickness, θ is the concave angle of the honeycomb unit, g is the length of the horizontal support column, and l is the length of the inclined support column.

[0034] Furthermore, the constitutive relation of the shear thickening (STF) fluid satisfies the following formula:

[0035]

[0036] Where η is the apparent viscosity, η 0 is the yield viscosity, τ 0 is the yield stress, is the shear rate, is the critical shear rate, k is the viscosity index, and n is the power law exponent.

[0037] Furthermore, the inner angle of the single reentrant hexagonal honeycomb unit ranges from 10° to 65°, and the angle of each layer of honeycomb units increases successively to form a continuous angle gradient, thereby achieving layered energy absorption;

[0038] The injection amount of the shear thickening fluid in each layer unit is adjusted according to different protection levels.

[0039] Furthermore, in the multi-layer gradient honeycomb core, the angle difference Δθ of two adjacent layers of honeycomb units satisfies 5°≤Δθ≤15°, so as to ensure the balance of layer-by-layer deformation and the stability of energy dissipation under impact load; the shear thickening fluid undergoes a sudden change in viscosity when subjected to high shear rate impact, and cooperates with the negative Poisson's ratio structure to significantly reduce the impact peak.

[0040] Furthermore, the high-strength interface bonding technology includes methods such as hot pressing, adhesives or metal diffusion welding, so that each layer is tightly bonded at the interface between the honeycomb core made of high-strength aluminum alloy material and the aluminum alloy plate, so as to improve the anti-peeling and impact resistance of the overall structure;

[0041] The connection between the honeycomb core and the upper and lower plates is sealed or packaged to prevent the shear thickening fluid from leaking or being affected by the environment.

[0042] Furthermore, the shear thickening fluid includes nanoparticles and a dispersion medium.

[0043] The present application also provides an application method of a composite anti - impact and energy - absorbing structure based on shear - thickening fluid and gradient negative Poisson's ratio metamaterial. The method is realized based on the composite anti - impact and energy - absorbing structure provided by the present application. The composite anti - impact and energy - absorbing structure is applied to vehicle protection, aerospace structure protection or personal protective equipment. And the angle gradient of each layer of the honeycomb core, the unit size, the filling amount of the shear - thickening fluid, and the thickness of the upper and lower aluminum alloy plates are adjusted according to the usage scenario to meet the buffer protection requirements under different impact load levels, and the shear - thickening fluid formula and encapsulation process are selected according to the usage scenario to further improve the energy dissipation and dynamic protection performance of the overall structure.

[0044] The following further describes a shear - thickening fluid / gradient negative Poisson's ratio metamaterial composite anti - impact and energy - absorbing structure according to an embodiment of the present invention with reference to the drawings.

[0045] As Figures 1 to 3 shown, this embodiment adopts a three - layer gradient negative Poisson's ratio honeycomb structure, and the specific dimensions of each unit cell are in millimeters. Each layer consists of 3 unit cells, namely honeycomb cores arranged in parallel, forming an overall 3×3 honeycomb core. High - strength aluminum alloy plates (material: AA6061) with a thickness of about 0.5 mm are arranged on the upper and lower surfaces and both side surfaces of the honeycomb core for encapsulation. The following elaborates on each layer of the structure in detail:

[0046] The first - layer structure: The horizontal width of each unit cell is 36 mm, the vertical height is 20 mm, the side - wall thickness is 0.5 mm, the length of the inclined support column is 13 mm, and the concave angle is 52°. A total of 3 identical unit cells in the first layer are arranged in parallel to form the first - layer honeycomb structure.

[0047] The second - layer structure: The horizontal width of each unit cell remains 36 mm, the vertical height increases to 25 mm, the side - wall thickness is 0.5 mm, the length of the inclined support column is 15 mm, and the concave angle is 58°. The second layer also contains 3 identical unit cells, which are closely connected to the first layer as a whole to form the second - layer honeycomb structure.

[0048] The third - layer structure: The horizontal width of each unit cell is still 36 mm, the vertical height increases to 31 mm, the side - wall thickness is 0.5 mm, the length of the inclined support column is 17 mm, and the concave angle is 64°. The third layer contains 3 identical unit cells, which are located below the second - layer honeycomb structure to form the third - layer honeycomb structure.

[0049] The concave angles of the three-layer unit cells increase layer by layer from about 52°, 58° to 64°, respectively, so that a significant negative Poisson's ratio effect can be produced in both the in-plane direction and the thickness direction, achieving graded absorption and uniform dispersion of impact energy. The honeycomb core is made of high-strength aluminum alloy material and is firmly connected to the upper and lower aluminum alloy plates through high-strength interface bonding technologies such as hot pressing, metal diffusion welding or adhesives to prevent delamination or peeling when subjected to high-speed impact. In this embodiment, vacuum-assisted injection is used to uniformly fill the shear thickening fluid (STF) inside each honeycomb unit. STF is composed of nanoparticles (such as silica, alumina, etc.) and a dispersion medium (such as polyethylene glycol PEG), which has good fluidity at low shear rates, and the viscosity increases rapidly under high shear rates, thereby providing additional energy dissipation. Its constitutive model can be described as:

[0050]

[0051] Where η is the apparent viscosity, η 0 is the yield viscosity, τ 0 =1.1121Pa is the yield stress, is the shear rate, (1 / s) is the critical shear rate, k = 0.03947 is the viscosity index, and n = 1.699 is the power law index. The connection between the honeycomb core and the upper and lower plates is encapsulated with a 0.5 mm thick AA6061 aluminum alloy plate to prevent STF from leaking or being affected by the environment.

[0052] like Figure 4 As shown in the figure, the three-layer gradient honeycomb core is assembled with the upper and lower aluminum alloy plates to form an integrated composite protective structure. When a high-speed impact load is applied from the outside, the gradient negative Poisson's ratio honeycomb unit first absorbs and disperses the energy layer by layer through its synchronous lateral and longitudinal contraction mechanism; at the same time, the STF in the honeycomb unit forces the shear thickening fluid to rapidly thicken at a high shear rate during the compression deformation process of the honeycomb core, thereby rapidly dissipating the impact energy, significantly reducing the local stress peak and enhancing the protective effect of the overall structure.

[0053] Figure 5 The figure shows the curve of the Von Mises stress at the center of the bottom plate changing with time when the bottom plate is subjected to impact load with and without a protective structure in this embodiment. It can be seen that when there is no protection, there is impact stress in the bottom plate, while when there is a protective structure, the shock wave decays rapidly in the protective structure and does not propagate to the bottom plate, and the stress of the bottom plate is almost 0.

[0054] Figure 6The figure shows the curve of vertical displacement at the center of the bottom plate changing with time when there is a protective structure and when there is no protective structure. It indicates that the protective structure can quickly absorb the impact energy and the bottom plate is not affected by the impact load, which fully verifies the excellent energy dissipation performance of the gradient negative Poisson's ratio honeycomb structure under high impact loads.

[0055] In summary, this embodiment realizes the synergistic energy absorption of the gradient negative Poisson's ratio honeycomb structure and the shear thickening dynamic thickening effect, greatly improving the impact resistance and buffering deformation capabilities, and is suitable for various high-impact scenarios such as vehicle protection, aerospace structure, and personal protective equipment.

[0056] Finally, it should be noted that the drawings are only for illustrative purposes and represent only schematic diagrams rather than physical drawings, and should not be construed as limiting the present invention; in order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted. The examples of the present invention are only descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made by engineers and technicians in this field to the technical solution of the present invention should fall within the scope of protection of the present invention.

[0057] The above-described embodiments of the present application do not constitute a limitation on the protection scope of the present application.

Claims

1. A shear thickening fluid and gradient negative Poisson's ratio metamaterial composite anti-impact energy absorption structure, characterized in that: The composite anti-impact energy-absorbing structure comprises two layers of high-strength aluminum alloy plates, an upper layer and a lower layer, and a multi-layer gradient honeycomb core located between the two layers of high-strength aluminum alloy plates; The gradient honeycomb core comprises multiple layers of single-entry hexagonal honeycomb units, each layer of honeycomb units has the same indentation angle, different layers have different indentation angles, and the indentation angles increase layer by layer from top to bottom. The material of the multiple layers of gradient honeycomb core is aluminum alloy, and is tightly connected with the upper and lower plates through high-strength interface bonding technology; The interior of the honeycomb unit is filled with a shear thickening fluid.

2. The shear thickening fluid and gradient negative Poisson's ratio metamaterial composite anti-impact energy absorption structure according to claim 1, characterized in that: The single reentrant hexagonal honeycomb unit is a negative Poisson's ratio structure. When subjected to an impact load, the unit undergoes coupled deformation in the thickness direction and the in-plane direction simultaneously to achieve efficient absorption and transmission blocking of impact energy. The honeycomb unit satisfies the following negative Poisson's ratio: Among them, v 12 is the in-plane Poisson’s ratio of the honeycomb unit, v s is the Poisson's ratio of the base material, t is the cell wall thickness, θ is the concave angle of the honeycomb unit, g is the length of the horizontal support column, and l is the length of the inclined support column.

3. The shear thickening fluid and gradient negative Poisson's ratio metamaterial composite anti-impact energy absorption structure according to claim 1, characterized in that: The constitutive relation of the shear thickening fluid satisfies the following formula: Where η is the apparent viscosity, η0 is the yield viscosity, τ0 is the yield stress, is the shear rate, is the critical shear rate, k is the viscosity index, and n is the power law exponent.

4. The shear thickening fluid and gradient negative Poisson's ratio metamaterial composite anti-impact energy absorption structure according to claim 1, characterized in that: The inner angle of the single reentrant hexagonal honeycomb unit ranges from 10° to 65°; The injection amount of the shear thickening fluid in each layer unit is adjusted according to different protection levels.

5. The shear thickening fluid and gradient negative Poisson's ratio metamaterial composite anti-impact energy absorption structure according to claim 1, characterized in that: In the multi-layer gradient honeycomb core, the angle difference Δθ between two adjacent layers of honeycomb units satisfies 5°≤Δθ≤15°.

6. The shear thickening fluid and gradient negative Poisson's ratio metamaterial composite anti-impact energy absorption structure according to claim 1, characterized in that: The high-strength interface bonding technology includes methods such as hot pressing, adhesives or metal diffusion welding; The connection between the honeycomb core and the upper and lower panels is sealed or packaged.

7. The shear thickening fluid and gradient negative Poisson's ratio metamaterial composite anti-impact energy absorption structure according to claim 1, characterized in that: The shear thickening fluid includes nanoparticles and a dispersion medium.

8. An application method of a composite anti-impact energy absorption structure based on a shear thickening fluid and a gradient negative Poisson's ratio metamaterial, the method being implemented based on any composite anti-impact energy absorption structure in claims 1 to 7, characterized in that: The composite impact-resistant energy-absorbing structure is applied to vehicle protection, aerospace structural protection or personal protective equipment; and the angle gradient of each layer of the honeycomb core, the unit size, the filling amount of the shear thickening fluid and the thickness of the upper and lower aluminum alloy plates are adjusted according to the usage scenario, and the shear thickening fluid formula and packaging process are selected according to the usage scenario.

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