Sandwich structure of magneto-rheological fluid filled negative poisson's ratio metamaterial

Abstract

This invention relates to the field of impact-resistant energy absorption technology. It discloses a sandwich structure filled with magnetorheological fluid and a negative Poisson's ratio metamaterial. A sealing plate is fixedly and sealed on the upper and lower end faces of a negative Poisson's ratio substrate, the size of which is equal to the dimensions of the upper and lower end faces of the substrate. The negative Poisson's ratio substrate and the sealing plate are inserted into the cavity of the sandwich shell. The magnetorheological fluid fills the negative Poisson's ratio substrate. Two mounting holes are symmetrically arranged from left to right on the upper and lower surfaces of the sandwich shell. An electromagnetic coil frame is fixedly disposed in the center of the mounting holes, and the electromagnetic coil is fitted inside the frame. When energized, the electromagnetic coil generates a low-frequency electromagnetic field on the upper and lower parts of the negative Poisson's ratio substrate, controlling the state of the magnetorheological fluid. The beneficial effects of this invention are: improved energy absorption and overall stiffness of the magnetorheological fluid-filled negative Poisson's ratio metamaterial sandwich structure.

Description

Technical Field

[0001] This invention relates to the field of impact energy absorption technology, and in particular to a sandwich structure of a negative Poisson's ratio metamaterial filled with magnetorheological fluid. Background Technology

[0002] Foamed metals (such as aluminum foam) have broad application prospects in the automotive, aerospace, and building protection fields due to their lightweight, high specific strength, and excellent energy absorption capacity. Currently, to improve the energy absorption performance of foamed metals, a sandwich structure can be formed by using foamed metal as an interlayer and fixing steel or stainless steel plates around it. Simultaneously, shear-thickening fluid or electrorheological fluid can be filled into the foamed metal. Through the synergistic effect of the foamed metal and the shear-thickening fluid (which generates shear stress upon impact) or the electrorheological fluid (which instantly transforms from a liquid to a non-Newtonian fluid under energized conditions), the strength and energy absorption effect of the foamed metal under impact are improved. For example, patent application number 201811539314.3, entitled "A Shear-Thickening Fluid-Filled Foamed Aluminum Bulletproof Plate," and patent application number 201822110495.X, entitled "An Electrorheological Fluid-Filled Foamed Aluminum Bulletproof Plate," are examples. The two patents disclosed filling foam metal with shear thickening fluid or electrorheological fluid, thereby improving the strength and energy absorption effect of foam metal under load impact through the synergistic effect of foam metal and shear thickening fluid or electrorheological fluid.

[0003] In existing technologies, the main methods for preparing foamed metals include melt foaming, powder metallurgy, and deposition. These methods suffer from complex process parameters and poor repeatability, resulting in uneven pore size distribution and an uncontrollable ratio of closed to open cells. This leads to an inability to reconcile the contradiction between energy absorption efficiency and overall stiffness in foamed metals. To improve the energy absorption performance and overall stiffness of sandwich panels, negative Poisson's ratio metamaterials (steel-based negative Poisson's ratio plates) are currently used to replace foamed metals. These materials utilize the excellent topological concave hexagonal structure of the steel-based negative Poisson's ratio plate, which expands under tensile stress and contracts under compressive stress (forming localized rigidity), thus improving the sandwich panel's resistance to impact stress. However, in actual impact stress environments, relying solely on the deformation energy absorption characteristics of negative Poisson's ratio metamaterials results in insufficient overall stiffness, making it unable to withstand the penetration of large impact stresses. Based on the aforementioned technical deficiencies in the prior art, this invention develops a sandwich structure for filling a negative Poisson's ratio metamaterial with magnetorheological fluid, which can effectively solve the technical problems existing in the prior art. Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a sandwich structure for a negative Poisson's ratio metamaterial filled with magnetorheological fluid. This invention utilizes the synergistic effect of the hexagonal concave hole topology of the negative Poisson's ratio substrate (deformed under impact stress) and the magnetorheological fluid (instantaneous rigidity change) to improve the performance of the magnetorheological fluid-filled negative Poisson's ratio metamaterial sandwich structure.

[0005] This invention provides a sandwich structure for a magnetorheological fluid-filled negative Poisson's ratio metamaterial, comprising a sandwich shell, a blocking plate, and a negative Poisson's ratio substrate. The sandwich shell is a hollow rectangular shape with an opening on the front side. The blocking plate is fixedly and sealed at the front side of the sandwich shell, and its size is equal to the size of the front opening of the sandwich shell. A sealing plate is fixedly and sealed on the upper and lower end faces of the negative Poisson's ratio substrate, and its size is equal to the size of the upper and lower end faces of the negative Poisson's ratio substrate. The negative Poisson's ratio substrate and the sealing plate are inserted into the cavity of the sandwich shell. The magnetorheological fluid is filled in the negative Poisson's ratio substrate. Two mounting holes are symmetrically opened from left to right on the upper and lower surfaces of the sandwich shell. An electromagnetic coil frame is fixedly disposed in the center of the mounting holes, and a vent is fixedly disposed above the mounting holes. The electromagnetic coil is fitted inside the electromagnetic coil frame. When the electromagnetic coil is energized, it is used to generate a low-frequency electromagnetic field on the upper and lower parts of the negative Poisson's ratio substrate to control the state of the magnetorheological fluid.

[0006] The negative Poisson's ratio substrate is a steel-based plate. The negative Poisson's ratio substrate includes a substrate body, which is square in shape. The size of the substrate body is equal to the size of the cavity inside the sandwich panel shell. Hexagonal recesses are uniformly formed on the negative Poisson's ratio substrate. The hexagonal recesses are through-holes from the top to the bottom of the negative Poisson's ratio substrate. The hexagonal recesses are gradually shaped with larger size in the middle and smaller size at the top and bottom. Each hexagonal recess is filled with magnetorheological fluid.

[0007] The mounting hole includes a mounting hole body, which is a recessed circular hole, and a boss is provided on the inner wall of the mounting hole body. The height of the boss is lower than the depth of the mounting hole body.

[0008] The sealing plate is connected to the four edges of the substrate body by laser sealing welding, and the sealing plate is made of the same material as the substrate body.

[0009] The electromagnetic coil frame includes a support body, which is circular in shape. The bottom of the support body has fan-shaped grooves at equal angles around its circumference. The support ring is fixedly installed at the bottom of the inner ring of the support body, and the bottom of the support ring is flush with the bottom of the inner ring of the support body. The elastic clamping piece has an arc shape that bends inward and is fixedly installed at the upper part of the support body at equal angles with the core of the support body as the center.

[0010] The electromagnetic coil frame is a one-piece structure cast from insulating bakelite material.

[0011] The ventilation opening includes a ring body, which is circular in shape, with a convex ring fixedly disposed at the bottom of the ring body. The diameter of the convex ring is smaller than the diameter of the ring body. A support plate is fixedly disposed in a cross shape in the inner ring of the convex ring, and ventilation rings are fixedly disposed on the support plate at equal intervals in the circumferential direction.

[0012] The height difference between the boss and the upper part of the mounting hole body is equal to the thickness of the convex ring.

[0013] The electromagnetic coil includes an iron core, which is ring-shaped, with a winding evenly wound around the iron core. The positive terminal is located on the right inner side of the iron core, and the negative terminal is located on the right outer side of the iron core. The positive and negative terminals are fixedly connected to the two ends of the winding, respectively.

[0014] The winding direction of the upper part of the sandwich panel shell is clockwise, and the winding direction of the lower part of the sandwich panel shell is counterclockwise, and the current direction of the winding is the same.

[0015] The positive and negative terminals are fixedly connected to the positive and negative terminals of the multi-channel power controller, respectively, and the electromagnetic frequency formed by the positive and negative terminals is 10Hz~15Hz.

[0016] The assembly process of this sandwich structure filled with magnetorheological fluid and a negative Poisson's ratio metamaterial is as follows: First, the magnetorheological fluid is poured into the hexagonal recesses of the negative Poisson's ratio substrate. Then, silicone sealant is applied to the edges of the sealing plate in contact with the negative Poisson's ratio substrate. Next, a laser welding gun is used to laser seal the edges of the sealing plate and the negative Poisson's ratio substrate at their contact points. Then, the sealing plate and the negative Poisson's ratio substrate are inserted into the cavity of the sandwich shell through the front opening. Finally, the sealing plate is fixed to the sandwich shell by screws or welding. A multi-channel power controller is fixedly connected to the positive and negative terminals of the electromagnetic coils via multiple wires, supplying a current in the same direction to the winding of the electromagnetic coils. The upper and lower electromagnetic coils of the sandwich shell generate electromagnetic fields in opposite directions. At this time, the magnetorheological fluid in the hexagonal recesses of the negative Poisson's ratio substrate is relatively concentrated in the middle of the hexagonal recesses, effectively preventing the magnetorheological fluid from settling. When a large load impact stress penetrates the surface of the sandwich panel shell, the magnetorheological fluid particles in the hexagonal concave holes of the negative Poisson's ratio substrate chain under the action of the magnetic fields of the upper and lower electromagnetic coils of the sandwich panel shell. The yield stress of the magnetorheological fluid increases suddenly. At the same time, the energy absorption effect of the magnetorheological fluid filling the negative Poisson's ratio metamaterial sandwich structure plate is improved under the deformation of the hexagonal concave holes of the negative Poisson's ratio substrate.

[0017] The beneficial effects of this invention are as follows: Through the synergistic effect of the hexagonal concave hole topology of the negative Poisson's ratio substrate, the magnetorheological fluid, and the electromagnetic coils: 1. It improves the overall energy absorption effect and overall stiffness of the negative Poisson's ratio metamaterial sandwich structure plate filled with magnetorheological fluid, which can resist the penetration of large load impact stress; 2. It can effectively eliminate electromagnetic eddy currents between the upper and lower electromagnetic coils and suppress the heating of the electromagnetic coils; 3. It can control the directional transport of iron particles in the magnetorheological fluid, so that the iron particles are concentrated in the large space area in the middle of the hexagonal concave hole; 4. It effectively forms the superposition effect of electromagnetic induction field, so that the magnetorheological fluid forms maximum stiffness and improves the energy absorption effect of large impact loads. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention;

[0019] Figure 2 This is a cross-sectional view of the invention from the right perspective;

[0020] Figure 3 This is a partially enlarged cross-sectional view of the sandwich panel shell of the present invention;

[0021] Figure 4 This is a partial enlarged view of the mounting holes of the present invention;

[0022] Figure 5 This is a schematic diagram of the structure of the electromagnetic coil frame, ventilation opening, and electromagnetic coil of the present invention;

[0023] Figure 6 This is a top-view cross-sectional view of the negative Poisson's ratio substrate of the present invention;

[0024] Figure 7 For the present invention Figure 5 A magnified view of a portion of the hexagonal concave hole;

[0025] The markings in the diagram are: 1. Sandwich panel shell, 2. Blocking plate, 3. Negative Poisson's ratio substrate, 31. Substrate body, 32. Hexagonal concave hole, 4. Magnetorheological fluid, 5. Mounting hole, 51. Mounting hole body, 52. Boss, 6. Sealing plate, 7. Electromagnetic coil frame, 71. Support body, 72. Fan-shaped groove, 73. Support ring, 74. Elastic clamping piece, 8. Ventilation port, 81. Ring body, 82. Protruding ring, 83. Ventilation ring, 84. Support plate, 9. Electromagnetic coil, 91. Iron core, 92. Winding, 93. Positive terminal, 94. Negative terminal. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments. These embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0027] This invention provides a sandwich structure for filling a negative Poisson's ratio metamaterial with magnetorheological fluid:

[0028] like Figure 1 or Figure 2 As shown, the sandwich panel shell 1 is a hollow square shape with an opening on the front side. The blocking plate 2 is fixedly and sealed at the front side of the sandwich panel shell 1. The size of the blocking plate 2 is equal to the size of the opening on the front side of the sandwich panel shell 1.

[0029] The main purpose of the above arrangement is, on the one hand, to form a sealed cavity for mounting the negative Poisson's ratio substrate 3 and the sealing plate 6; on the other hand, to improve the overall stiffness of the negative Poisson's ratio metamaterial sandwich panel filled with magnetorheological fluid 4 under the synergistic effect of the sandwich panel shell 1, the negative Poisson's ratio substrate 3 and the sealing plate 6.

[0030] With the aforementioned installation of the blocking plate 2, the removable nature of the blocking plate 2 allows the negative Poisson's ratio substrate 3 and the sealing plate 6 to be easily inserted into the cavity of the sandwich panel shell 1 from their front opening positions.

[0031] like Figure 2 As shown, sealing plates 6 are fixedly and sealed on the upper and lower end faces of the negative Poisson's ratio substrate 3. The dimensions of the sealing plates 6 are equal to the dimensions of the upper and lower end faces of the negative Poisson's ratio substrate 3. The negative Poisson's ratio substrate 3 and the sealing plates 6 are inserted into the cavity of the sandwich panel shell 1. The main purpose of this arrangement is to improve the fixing and welding accuracy of the negative Poisson's ratio substrate 3 and the sealing plates 6, so that the negative Poisson's ratio substrate 3 and the sealing plates 6 can be precisely fitted and inserted into the cavity of the sandwich panel shell 1, thereby improving their fitting accuracy.

[0032] like Figure 6 As shown in Figure 7, magnetorheological fluid 4 is filled in negative Poisson's ratio substrate 3, and hexagonal recesses 32 are uniformly formed on negative Poisson's ratio substrate 3. The hexagonal recesses 32 extend from the upper part to the lower part of negative Poisson's ratio substrate 3. The hexagonal recesses 32 are in a gradient shape with a larger size in the middle and smaller size at the top and bottom. Each hexagonal recess 32 is filled with magnetorheological fluid 4.

[0033] The main purpose of this arrangement is to utilize the gradually tapering hexagonal recesses 32, which are larger in the middle and smaller at the top and bottom, to, on the one hand, allow the magnetorheological fluid to relatively concentrate in the middle of the hexagonal recesses 32 under the absence of an electromagnetic field, effectively preventing the sedimentation of the magnetorheological fluid 4. On the other hand, it enhances the deformation capability of the middle position of the negative Poisson's ratio substrate 3, thereby improving the energy absorption performance of the negative Poisson's ratio substrate 3.

[0034] like Figure 4 and 5 As shown, the mounting hole 5 includes a mounting hole body 51, which is a recessed circular hole. A boss 52 is provided on the inner wall of the mounting hole body 51. The height of the boss 52 is lower than the depth of the mounting hole body 51. The height difference between the boss 52 and the upper part of the mounting hole body 51 is equal to the thickness of the convex ring 82.

[0035] The main purpose of the above arrangement is to fit the convex ring 82 of the vent 8 onto the boss 52 of the mounting hole body 51, so that the upper end face of the vent 8 is flush with the surface of the sandwich panel shell 1.

[0036] like Figure 2 As shown in Figure 3, the sealing plate 6 is laser-sealed at the periphery of the substrate body 31, and the material of the sealing plate 6 is the same as that of the substrate body 31. The main purpose of this arrangement is to prevent leakage of the magnetorheological fluid 4 from the hexagonal recesses 32 of the substrate body 31.

[0037] like Figure 5 As shown, the electromagnetic coil frame 7 includes a support body 71, which is circular in shape. The bottom of the support body 71 has fan-shaped grooves 72 at equal angles around its circumference. A support ring 73 is fixedly installed at the bottom of the inner ring of the support body 71, and the bottom of the support ring 73 is flush with the bottom of the inner ring of the support body 71. An elastic clamping piece 74 has an arc shape that bends inward and is fixedly installed at the upper part of the support body 71 at equal angles with the circular core of the support body 71 as the center. The electromagnetic coil frame 7 is an integral structure cast from insulating bakelite material.

[0038] The main purpose of the above arrangement is to use the insulating bakelite material of the electromagnetic coil frame 7 to, on the one hand, fix the electromagnetic coil 9 in place; on the other hand, to provide insulation and prevent leakage of the electromagnetic coil 9 under the condition that the electromagnetic coil 9 normally generates a low-frequency magnetic field.

[0039] The above-mentioned fan-shaped grooves 72 are provided at equal angles around the bottom of the support body 71. The heat generated by the electromagnetic coil 9 can be discharged through the fan-shaped grooves 72, the mounting holes 5 and the vents 8, forming a heat dissipation channel for dissipating the heat at the bottom of the electromagnetic coil 9.

[0040] The aforementioned support ring 73 provides stable support for the bottom of the electromagnetic coil 9.

[0041] The aforementioned elastic clamping piece 74 utilizes the elasticity of the elastic clamping piece 74 itself. During installation, the rigidity of the winding 92 itself and the compression of the elastic clamping piece 74 are used to clamp the iron core 91 and the winding 92 in the center of the four elastic clamping pieces 74, thereby playing the role of wrapping and fixing the iron core 91 and the winding 92.

[0042] like Figure 5As shown, an electromagnetic coil 9 is fixedly installed on each electromagnetic coil frame 7 of the mounting hole 5. The electromagnetic coil 9 includes an iron core 91, which is ring-shaped. A winding 92 is evenly wound on the iron core 91. The positive terminal 93 is located on the right inner side of the iron core 91, and the negative terminal 94 is located on the right outer side of the iron core 91. The positive terminal 93 and the negative terminal 94 are fixedly connected to the two ends of the winding 92, respectively.

[0043] The main purpose of the above arrangement is to form a uniform electromagnetic induction field in the upper and lower parts of the negative Poisson's ratio substrate 3 to control the shape of the magnetorheological fluid 4, so that the magnetorheological fluid 4 can be instantly transformed from a Newtonian fluid to a Bingham fluid. By utilizing the deformation characteristics of the hexagonal concave hole 32 of the negative Poisson's ratio substrate 3 under impact stress, in conjunction with the stiffness of the magnetorheological fluid 4, the energy absorption effect of large load impact stress is improved.

[0044] like Figure 5 As shown, the winding direction of the upper part of the sandwich panel shell 1 is clockwise, and the winding direction of the lower part of the sandwich panel shell 1 is counterclockwise, and the current direction of the winding 92 is the same.

[0045] The main purpose of the above arrangement is to generate electromagnetic fields in opposite directions between the upper electromagnetic coil 9 and the lower electromagnetic coil 9 of the sandwich panel shell 1. On the one hand, this can effectively eliminate electromagnetic eddy currents between the two electromagnetic coils 9 and suppress the heating of the electromagnetic coils 9. On the other hand, it can control the directional transport of iron particles in the magnetorheological fluid 4, so that the iron particles gather in the large space area in the middle of the hexagonal concave hole 32. Furthermore, it effectively forms the superposition effect of electromagnetic induction fields, so that the magnetorheological fluid 4 achieves maximum stiffness and improves the energy absorption effect of large impact loads.

[0046] like Figure 1-7As shown, the assembly process of this sandwich structure filled with magnetorheological fluid and negative Poisson's ratio metamaterial is as follows: First, the magnetorheological fluid 4 is poured into the hexagonal recess 32 of the negative Poisson's ratio substrate 3. Then, the edge of the sealing plate 6 in contact with the negative Poisson's ratio substrate 3 is coated with silicone sealant. Then, the edge of the contact between the sealing plate 6 and the negative Poisson's ratio substrate 3 is laser sealed and welded using a laser welding gun. Subsequently, the sealing plate 6 and the negative Poisson's ratio substrate 3 are inserted into the cavity of the sandwich shell 1 from the front opening. Then, the blocking plate 2 is fixed to the sandwich shell 1 by screws or welding. A multi-channel power controller is fixedly connected to the positive terminal 93 and negative terminal 94 of the electromagnetic coil 9 via multiple wires, supplying a current in the same direction to the winding 92 of the electromagnetic coil 9. The upper and lower electromagnetic coils of the sandwich panel 1 generate electromagnetic fields in opposite directions. At this time, the magnetorheological fluid 4 in the hexagonal recesses 32 of the negative Poisson's ratio substrate 3 is relatively concentrated in the middle of the hexagonal recesses 32, which can effectively prevent the sedimentation of the magnetorheological fluid 4. When a large load impact stress penetrates the surface of the sandwich panel 1, under the action of the magnetic fields of the upper and lower electromagnetic coils of the sandwich panel 1, the magnetorheological fluid 4 particles in the hexagonal recesses 32 of the negative Poisson's ratio substrate 3 chain up, and the yield stress of the magnetorheological fluid 4 increases sharply. At the same time, the deformation of the hexagonal recesses 32 of the negative Poisson's ratio substrate 3 improves the energy absorption effect of the magnetorheological fluid filling the negative Poisson's ratio metamaterial sandwich structure.

[0047] Various modifications to the above embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to cover the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sandwich structure for a magnetorheological fluid-filled negative Poisson's ratio metamaterial, comprising a sandwich shell, a blocking plate, and a negative Poisson's ratio substrate, characterized in that: The sandwich panel shell is a hollow rectangular shape with an opening on the front. A sealing plate is fixedly installed on the front side of the sandwich panel shell, and the size of the sealing plate is equal to the size of the front opening of the sandwich panel shell. Sealing plates are fixedly installed on the upper and lower end faces of the negative Poisson's ratio substrate, and the size of the sealing plates is equal to the size of the upper and lower end faces of the negative Poisson's ratio substrate. The negative Poisson's ratio substrate and the sealing plates are inserted into the cavity of the sandwich panel shell. Magnetorheological fluid is filled in the negative Poisson's ratio substrate. Two mounting holes are symmetrically opened from left to right on the upper and lower surfaces of the sandwich panel shell. An electromagnetic coil frame is fixedly installed in the center of the mounting hole, and a vent is fixedly installed above the mounting hole. The electromagnetic coil is installed inside the electromagnetic coil frame. After the electromagnetic coil is energized, it is used to generate a low-frequency electromagnetic field on the upper and lower parts of the negative Poisson's ratio substrate to control the state of the magnetorheological fluid.

2. The sandwich structure of a magnetorheological fluid-filled negative Poisson's ratio metamaterial according to claim 1, characterized in that: The negative Poisson's ratio substrate is a steel-based plate. The negative Poisson's ratio substrate includes a substrate body, which is square in shape. The size of the substrate body is equal to the size of the cavity inside the sandwich panel shell. Hexagonal recesses are uniformly formed on the negative Poisson's ratio substrate. The hexagonal recesses are through-holes from the top to the bottom of the negative Poisson's ratio substrate. The hexagonal recesses are gradually shaped with larger size in the middle and smaller size at the top and bottom. Each hexagonal recess is filled with magnetorheological fluid.

3. The sandwich structure of a magnetorheological fluid-filled negative Poisson's ratio metamaterial according to claim 1, characterized in that: The mounting hole includes a mounting hole body, which is a recessed circular hole, and a boss is provided on the inner wall of the mounting hole body. The height of the boss is lower than the depth of the mounting hole body.

4. The sandwich structure of a magnetorheological fluid-filled negative Poisson's ratio metamaterial according to claim 1, characterized in that: The electromagnetic coil frame includes a support body, which is circular in shape. The bottom of the support body has fan-shaped grooves at equal angles around its circumference. The support ring is fixedly installed at the bottom of the inner ring of the support body, and the bottom of the support ring is flush with the bottom of the inner ring of the support body. The elastic clamping piece has an arc shape that bends inward and is fixedly installed at the upper part of the support body at equal angles with the core of the support body as the center.

5. The sandwich structure of a magnetorheological fluid-filled negative Poisson's ratio metamaterial according to claim 1, characterized in that: The electromagnetic coil frame is a one-piece structure cast from insulating bakelite material.

6. The sandwich structure of a magnetorheological fluid-filled negative Poisson's ratio metamaterial according to claim 1, characterized in that: The ventilation opening includes a ring body, which is circular in shape, with a convex ring fixedly disposed at the bottom of the ring body. The diameter of the convex ring is smaller than the diameter of the ring body. A support plate is fixedly disposed in a cross shape in the inner ring of the convex ring, and ventilation rings are fixedly disposed on the support plate at equal intervals in the circumferential direction.

7. The sandwich structure of a magnetorheological fluid-filled negative Poisson's ratio metamaterial according to claim 3, characterized in that: The height difference between the boss and the upper part of the mounting hole body is equal to the thickness of the convex ring.

8. The sandwich structure of a magnetorheological fluid-filled negative Poisson's ratio metamaterial according to claim 1, characterized in that: The electromagnetic coil includes an iron core, which is ring-shaped, with a winding evenly wound around the iron core. The positive terminal is located on the right inner side of the iron core, and the negative terminal is located on the right outer side of the iron core. The positive and negative terminals are fixedly connected to the two ends of the winding, respectively.

9. A sandwich structure for a magnetorheological fluid-filled negative Poisson's ratio metamaterial according to claim 1, characterized in that: The winding direction of the upper part of the sandwich panel shell is clockwise, and the winding direction of the lower part of the sandwich panel shell is counterclockwise, and the current direction of the winding is the same.

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