Construction method of 3D negative Poisson's ratio metamaterial of mixed positive and negative Poisson's ratio structure

Abstract

The invention relates to the technical field of metamaterial lattice structures, in particular to a construction method of a mixed positive and negative Poisson's ratio structure. According to the method, a lattice structure is constructed based on a plurality of FCC, then the lattice structure and a 3D RH structure are fused to form a new concave lattice structure, and the structure solves the problems that an existing negative Poisson's ratio structure is large in plastic section stress fluctuation and low in platform stress under compression loads, so that the energy absorption performance of the negative Poisson's ratio structure is improved, and the energy absorption performance of the negative Poisson's ratio structure is improved. The invention discloses a mixed positive and negative Poisson's ratio structure constructed by the method, a metamaterial comprising the structure and a preparation method of the metamaterial.

Description

Technical Field

[0001] This invention relates to the field of metamaterial lattice structure technology, and in particular to a method for constructing a hybrid positive and negative Poisson's ratio structure. Background Technology

[0002] Mechanical metamaterials exhibiting a negative Poisson's ratio are called dilatational metamaterials. They expand under tension and contract under compression, exhibiting a unique negative Poisson's ratio (NPR) effect. This NPR effect enhances the mechanical properties of such materials, including impact resistance, fracture resistance, and energy absorption, making them ideal for applications requiring energy absorption, such as automotive parts and explosion-proof devices. A common type of NPR metamaterial is the RH (re-entrant honeycomb) structure. The earliest report of 3D RH was in the paper "Mechanical properties of 3D re-entrant honeycombauxetic structures realized via additive manufacturing," *International Journal of Solids and Structures*, Vol. 69-70, September 2015, pp. 475-490. When uniaxial pressure is applied, the rod moves inward due to the contraction of the concavity angle α, while the rod rotates simultaneously, resulting in overall contraction and the NPR effect.

[0003] Currently, many energy absorption enhancement methods for RH structures are achieved by simply adding support rods. However, the deformation modes of these structures are often difficult to control, and their performance is unpredictable. Furthermore, most current research on RH is based on two-dimensional structures, with only a few based on three-dimensional structures. Due to their high porosity, 3D RH structures suffer from relatively low stiffness and stability, large stress fluctuations in the plastic segment under compressive loads, and low plateau stress. These issues limit further improvements in the energy absorption performance of 3D RH structures. Summary of the Invention

[0004] To address the issues of large stress fluctuations and low plateau stress in the plastic segment of negative Poisson's ratio structures under compressive loads, and thus improve the energy absorption performance of negative Poisson's ratio structures, this application proposes a method for constructing hybrid positive and negative Poisson's ratio structures.

[0005] The method for constructing a hybrid positive and negative Poisson's ratio structure proposed in this invention includes:

[0006] Design a 3D RH structure and an FCC with the same rod diameter, height, and inner length as the 3D RH structure;

[0007] The 3D RH structure and the FCC were modeled using 3D modeling software;

[0008] The FCC has a hollow structure with four faces that are connected end to end around the perimeter. Each face includes two perpendicularly intersecting rods. The intersection of the two rods is the center of the face. The outer contour of the whole enclosed by the four faces is a cube.

[0009] One FCC is taken as the original FCC, and four FCCs are arranged in two rows and two columns around the original FCC array as the first group of FCCs. The orientation of each FCC in the first group of FCCs is the same as that of the original FCC. The two FCCs side by side in each row are connected together, and the connected surfaces overlap to form a single surface. The two rows of FCCs are arranged vertically along the same plane with a gap in the middle. The original FCC is arranged coplanarly with the other four FCCs and is located between the two rows of FCCs. On the two rows of FCCs, the face centers of the four FCCs located on the same plane are respectively located directly above or below the four vertices of the original FCC on the same plane. The face centers of the four FCCs are all at a preset distance from their corresponding vertices.

[0010] The preset distance will be calculated using a distance formula, which includes:

[0011]

[0012] In the formula, d represents the preset distance. Indicates the rod diameter of the FCC, Indicates the height of the FCC, Indicates the inner length of the FCC, Indicates the interior angle of the 3D RH structure;

[0013] A second set of FCCs is copied at the position after the first set of FCCs is rotated 90 degrees around the central axis of the original FCCs. The original FCCs, the first set of FCCs, and the second set of FCCs constitute the final FCC combination. The four face centers of the first set of FCCs on one side and the four face centers of the opposite side of the first set of FCCs are used as the eight vertices of a cuboid. The cuboid is used as the outer frame of the crystal structure. Boolean intersection operation is performed with the FCC combination to obtain the crystal structure.

[0014] After the center point of the 3D RH structure is overlapped with the center point of the above-mentioned lattice structure, a Boolean union operation is performed to form the final concave lattice structure with mixed positive and negative Poisson ratios.

[0015] Furthermore, the rod diameter The value range is 0.1-0.5mm, inner length It is 5mm high. The value range is 0.7-1× mm, the interior angle of the 3D RH structure The value range is 55-70°.

[0016] Furthermore, the ratio of height h to inner length l is 7:10.

[0017] Furthermore, the rod diameter It is 0.5mm, inner length It is 5mm high. It is 3.5mm, and the interior angle It is 65°.

[0018] This invention also proposes a hybrid positive and negative Poisson's ratio structure constructed by the aforementioned method.

[0019] The present invention also proposes a 3D negative Poisson's ratio metamaterial with a hybrid positive and negative Poisson's ratio structure, comprising multiple arrays of lattices, wherein at least one lattice is the aforementioned hybrid positive and negative Poisson's ratio structure.

[0020] The present invention also proposes a method for preparing the aforementioned 3D negative Poisson's ratio metamaterial, including preparing the lattice using digital light processing 3D printing, laser selective melting 3D printing, fused deposition modeling, stereolithography, and selective laser sintering processes.

[0021] Furthermore, when using digital light processing 3D printing technology, the printing material is a high-temperature resistant photosensitive resin.

[0022] Furthermore, when using digital light processing 3D printing technology, a high-temperature resistant photosensitive resin suitable for the 405nm curing band is used. The preparation parameters include: light intensity of 35mW / cm2, exposure time of 1s per layer, and layer thickness of 0.02mm.

[0023] Furthermore, when using the laser selective melting 3D printing process, the printing material is maraging steel powder.

[0024] Furthermore, when using the laser selective melting 3D printing process, the maraging steel powder is Fe-14Ni-16Co-9Mo-0.9Ti powder with a particle size of 15-53um. The preparation parameters include: laser power of 250W, scanning speed of 900 mm / s, scanning spacing of 0.11mm, layer thickness of 30um, and scanning strategy of strip scanning.

[0025] This application proposes a method for constructing a 3D negative Poisson's ratio metamaterial with a hybrid positive and negative Poisson's ratio structure. By introducing a positive Poisson's ratio structure into the negative Poisson's ratio structure, the problem of large stress fluctuations and low plateau stress in the plastic segment under compressive load is solved, thereby improving the energy absorption performance of the negative Poisson's ratio structure. Attached Figure Description

[0026] To more clearly illustrate the technical solution of the present invention, the accompanying drawings required in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and therefore should not be regarded as a limitation on the scope of protection of the present invention. In the various drawings, similar components are numbered similarly.

[0027] Figure 1 A schematic diagram of the RH-FCC lattice structure construction method proposed in this application embodiment is shown;

[0028] Figure 2 This illustration shows a schematic diagram of the first set of FCCs and the original FCCs in the construction method proposed in this application embodiment;

[0029] Figure 3 A schematic diagram of the FCC rotating array in the construction method proposed in this application embodiment is shown;

[0030] Figure 4 This paper illustrates a schematic diagram of the FCC intersection point in the construction method proposed in an embodiment of this application.

[0031] Figure 5 A comparison chart of force and displacement curves between RH-FCC and conventional RH in the embodiments of this application is shown. Detailed Implementation

[0032] To more clearly demonstrate the implementation steps and advantages of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments.

[0033] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] To achieve precise combination of substructures and re-entrant honeycomb (RH) for superior coupled deformation, resulting in more stable deformation modes and plateau stages, predictable performance, and enhanced energy absorption capacity, this application proposes a method for constructing a 3D negative Poisson's ratio metamaterial based on a hybrid positive and negative Poisson's ratio structure approach. This 3D negative Poisson's ratio metamaterial can address the problems of large stress fluctuations and low plateau stress in the plastic segment of negative Poisson's ratio structures under compressive loads, thereby improving the energy absorption performance of negative Poisson's ratio structures. Exemplarily, as shown... Figure 1 As shown, the specific implementation steps for constructing this 3D negative Poisson's ratio metamaterial with a hybrid positive and negative Poisson's ratio structure are as follows:

[0035] Design one FCC (face-centered cubic) structure and one conventional 3D RH (re-entranthoneycomb auxetic) structure. The defining parameters of the 3D RH structure include the rod diameter. ,high Internal length , interior angle The rod diameter of the FCC structure ,high and Interior Minister Maintaining consistency with the RH structure, in other words, rod diameter ,high and Interior Minister .

[0036] Using 3D modeling software, a 3D RH structure model was created based on the above four determining parameters, establishing a rod diameter of... Height is The inner length is The interior angle is The 3D RH structure, exemplary, has a rod diameter The value range is 0.1-0.5mm, inner length It is 5mm high. The value range is 0.7-1× mm, and interior angle The value range is 55-70°, for example, It can be 0.5mm, It can be 3.5mm, It can be 5mm and The angle can be 65°. The 3D modeling software can be SOLIDWORKS. Conventional 3D RH structural modeling is well known to those skilled in the art and will not be elaborated upon here.

[0037] A face-centered cubic (FCC) structure was modeled using 3D modeling software, and its bar diameter was determined. ,high and Interior Minister To maintain consistency with the RH structure, in other words, establish a rod diameter ,high and Interior Minister The FCC structure is a hollow face-centered cubic structure with four faces that are connected end to end around the perimeter. Each face includes two intersecting rods that form an "X" shape, with the intersection point being the center of the face.

[0038] like Figure 1As shown, after constructing the FCC and 3D RH structures, the FCC is introduced into the 3D RH structure to generate a novel concave lattice RH-FCC. In this application, multiple FCCs are arrayed at a preset distance to form a new set of FCCs. For example, five FCCs can be arrayed at a preset distance, and four of them can be copied and rotated to obtain nine FCCs as a new FCC combination. Using the four face centers of the first group of FCCs in this FCC combination, and the four face centers of the face center of the face opposite to the first face, as the eight vertices of a cuboid, and using this cuboid as the outer frame of the lattice structure that matches the 3D RH structure, a Boolean intersection operation is performed with the FCC combination to obtain the lattice structure; then, a Boolean union operation is performed between the 3D RH structure and this lattice structure to form a new concave lattice.

[0039] Specifically, such as Figure 2 As shown, one FCC is used as the original FCC, that is... Figure 2 The original FCC is initially represented by a medium gray FCC. Four additional FCCs are added as the first group. The orientation of each FCC in this first group is identical to the original FCC, only their positions differ. The four FCCs in the first group are arranged in pairs, with the two FCCs in each row arranged side-by-side, their connecting faces overlapping. The two rows of FCCs are arranged vertically along the same plane, with a gap in between. The original FCC is arranged coplanarly with the other four FCCs, positioned between the two rows of FCCs. On each row of FCCs, the face centers of the four FCCs on the same plane are located directly above or below the four vertices of the original FCC on that plane. The face centers of the four FCCs are at preset distances from their corresponding vertices. In other words, the distances from the two vertices above the original FCC to their directly above face centers are preset distances, and the distances from the two vertices below the original FCC to their directly below face centers are also preset distances. These preset distances are calculated using the following formula:

[0040]

[0041] In the formula, d represents the preset distance. Indicates rod diameter, Indicates height, Indicates internal length, This represents the interior angle of the 3D RH structure.

[0042] like Figure 3 As shown, by rotating the four FCCs in the first group of FCCs by 90° around the central axis (the axis passing through both openings) of the original FCCs, another group of four FCCs is copied to obtain the second group of FCCs. Figure 3 The blue part.

[0043] The first group of FCCs, the second group of FCCs, and the original FCCs will form a new group of FCCs. This new group of FCCs contains eight intersection points around the aforementioned central axis, such as... Figure 4 As shown, Figure 4 The red dot around the central axis between the blue and yellow FCC groups is the intersection point. It is easy to see that these 8 intersection points are actually the face centers of the 4 coplanar FCCs in the first group of FCCs, and the face centers of the 4 coplanar FCCs on the opposite face. Using these 8 points as the 8 vertices of a cuboid, a lattice matching the 3D RH structure can be formed. The Boolean intersection operation between the first group of FCCs, the second group of FCCs, and the original FCCs within the cuboid frame formed by the 8 vertices, that is, the Boolean intersection operation between the red cuboid frame and the FCCs in the figure, will yield a lattice structure that matches the 3D RH structure.

[0044] like Figure 1 As shown, by overlapping the center point of the 3D RH structure with the center point of the above lattice structure, a Boolean "union" operation is performed on the 3D RH structure and the lattice structure to obtain a new concave crystal structure RH-FCC, thereby completing the introduction of FCC into RH.

[0045] Fabrication of RH-FCC lattice structure:

[0046] In one embodiment, a method for preparing a 3D negative Poisson's ratio metamaterial with a hybrid positive and negative Poisson's ratio structure involves repeatedly arranging at least one concave lattice to form a cuboid-shaped 3D negative Poisson's ratio metamaterial. The RH-FCC proposed in this application can be prepared using a commercial digital light processing (DLP) 3D printer (microArch S240A). High-temperature resistant photosensitive resin (HTL) suitable for a 405nm curing wavelength is placed in a resin-containing container. Under irradiation by a light source system, the photosensitive resin undergoes a curing reaction and then adheres to a build platform. The material is then lifted by a linear actuator, curing the material layer by layer to achieve the desired specifications. The exposure area of ​​each layer is controlled by a digital mirror device. With printing parameters of a light intensity of 35mW / cm², an exposure time of 1s per layer, and a layer thickness of 0.02mm, the RH-FCC exhibits good molding quality. Alternatively, the RH-FCC proposed in this application can also be prepared using a commercial selective laser melting (SLM) 3D printer (DiMetal-280). Martensitic aging steel powder (Fe-14Ni-16Co-9Mo-0.9Ti) with a particle size of 15-53 μm was placed in a powder hopper and fed to a build platform using a linear reciprocating doctor blade. Under irradiation with a high-energy laser beam, the metal powder melted and then solidified onto the build platform, descending layer by layer via a linear actuator. Under printing parameters of 250 W laser power, 900 mm / s scanning speed, 0.11 mm scanning spacing, 30 μm layer thickness, and strip scanning strategy (67° rotation angle), the RH-FCC achieved good molding quality. The RH-FCC proposed in this application can be prepared not only by the aforementioned DLP and SLM methods, but also by additive manufacturing processes such as fused deposition modeling (FDM), stereolithography (SLA), and selective laser sintering (SLS). In some other embodiments, the metamaterial is not entirely composed of RH-FCC and may also contain other lattice structures or a completely solid structure.

[0047] Finite element analysis settings:

[0048] 1: The modulus of dense HTL resin was set to 1.86 GPa, Poisson's ratio to 0.43, yield strength to 45.043 MPa, yield strengthening modulus to 129.97 MPa, and a flexible damage model was adopted with a fracture strain of 0.092.

[0049] 2: The model is meshed using four-node linear tetrahedral elements (C3D4).

[0050] 3: Two rigid plates are placed at the top and bottom of the model respectively. The boundary conditions are set such that all degrees of freedom of the bottom plate of the model are restricted, while nodes in other areas are allowed to translate in the direction of compression loading. The interaction between the rigid plates and the model is defined as contact (tangential behavior is defined as penalty contact with a friction coefficient of 0.3, and normal behavior is defined as hard contact).

[0051] 4: In order to compress the structure to a compact size, only a displacement of 0.8 relative to the structure was applied to the top surface of the model.

[0052] Structural parameter optimization:

[0053] Using the controlled variable method and the aforementioned finite element analysis, the effects of three parameters of the RH-FCC structure—rod diameter t, the ratio of inner length l to height h b, and interior angle a—on energy absorption were studied. The optimal combination of structural parameters for the RH-FCC was determined: rod diameter t, inner length l, height h, and interior angle a are 0.5 mm, 3.5 mm, 5 mm, and 65°, respectively, and the ratio of height h to inner length l b is 7:10 (3.5 mm: 5 mm).

[0054] In one embodiment, a 3D negative Poisson's ratio metamaterial with a hybrid positive and negative Poisson's ratio structure is prepared by the above-described method for preparing a 3D negative Poisson's ratio metamaterial with a hybrid positive and negative Poisson's ratio structure, and the 3D negative Poisson's ratio metamaterial includes at least one of the above-described hybrid positive and negative Poisson's ratio structures; in other words, the 3D negative Poisson's ratio metamaterial is partially or entirely composed of a concave lattice.

[0055] In this example, the finite element method (FEM) was used, and ABAQUS software was employed to simulate the stress distribution of RH-FCC with different structural parameters under compressive loads. Based on this, the optimal combination of structural parameters for RH-FCC was determined using the controlled variable method. Compared with other re-entrant honeycomb (RH) structures, RH-FCC exhibits superior energy absorption performance. Figure 5 It can be seen that the force-displacement curve of RH-FCC is larger than that of the conventional RH structure with the same structural parameters, and the area under the force-displacement curve is larger at the same displacement than that of the conventional 3D RH structure. This indicates that RH-FCC has excellent energy absorption performance. At the same compression to 6mm (densification strain point), the energy absorption of the conventional 3D RH structure is 3.724 J / g, while that of the improved RH-FCC is 4.948 J / g, representing a 32.87% improvement in energy absorption performance.

[0056] In summary, this application addresses the issues of large stress fluctuations and low plateau stress in the plastic segment of negative Poisson's ratio structures under compressive loads by introducing a positive Poisson's ratio structure into the negative Poisson's ratio structure, thereby enhancing the energy absorption performance of the negative Poisson's ratio structure. This structure can be applied to numerous scenarios, including automotive crash barrier energy-absorbing boxes, automotive crash barrier beam sandwich panels, automotive suspensions, automotive engine hoods, shoe soles, helmets, non-pneumatic tires, and explosion-proof devices.

[0057] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing a hybrid positive and negative Poisson's ratio structure, characterized in that, include: Design a 3D RH structure and an FCC with the same rod diameter, height, and inner length as the 3D RH structure; The 3D RH structure and the FCC were modeled using 3D modeling software; The FCC has a hollow structure with four faces that are connected end to end around the perimeter. Each face includes two perpendicularly intersecting rods. The intersection of the two rods is the center of the face. The outer contour of the whole enclosed by the four faces is a cube. One FCC is taken as the original FCC, and four FCCs are arranged in two rows and two columns around the original FCC array as the first group of FCCs. In the first group of FCCs, the orientation of each FCC is the same as that of the original FCC. In each row, two FCCs side by side are connected together, and the connected surfaces overlap to form a single surface. The two rows of FCCs are arranged vertically along the same plane with a gap in the middle. The original FCC is arranged coplanarly with the other four FCCs and is located between the two rows of FCCs. On the two rows of FCCs, the face centers of the four FCCs located on the same plane are respectively located directly above or directly below the four vertices of the original FCC on the same plane. The face centers of the four FCCs are all at a preset distance from their corresponding vertices. The preset distance will be calculated using a distance formula, which includes: ， In the formula, d represents the preset distance. Indicates the rod diameter of the FCC, Indicates the height of the FCC, Indicates the inner length of the FCC, Indicates the interior angle of the 3D RH structure; A second set of FCCs is copied at the position after the first set of FCCs is rotated 90 degrees around the central axis of the original FCCs. The original FCCs, the first set of FCCs, and the second set of FCCs constitute the final FCC combination. The four face centers of the first set of FCCs on one side and the four face centers of the opposite side of the first set of FCCs are used as the eight vertices of a cuboid. The cuboid is used as the outer frame of the crystal structure. Boolean intersection operation is performed with the FCC combination to obtain the crystal structure. After the center point of the 3D RH structure is overlapped with the center point of the above-mentioned lattice structure, a Boolean union operation is performed to form the final concave lattice structure with mixed positive and negative Poisson ratios.

2. The method according to claim 1, characterized in that, The rod diameter The value range is 0.1-0.5mm, inner length It is 5mm high. The value range is 0.7-1× mm, the interior angle of the 3D RH structure The value range is 55-70°.

3. The method according to claim 1, characterized in that, The ratio of height h to inner length l, b, is 7:

10.

4. A hybrid positive and negative Poisson's ratio structure constructed by the method described in any one of claims 1-3.

5. A 3D negative Poisson's ratio metamaterial with a hybrid positive and negative Poisson's ratio structure, characterized in that, A lattice comprising multiple arrays, wherein at least one lattice is a mixed positive and negative Poisson's ratio structure as described in claim 4.

6. The method for preparing the 3D negative Poisson's ratio metamaterial according to claim 5, characterized in that, The lattice was prepared using digital light processing 3D printing, laser selective melting 3D printing, fused deposition modeling, stereolithography, and selective laser sintering processes.

7. The method for preparing the 3D negative Poisson's ratio metamaterial according to claim 6, characterized in that, When using digital light processing 3D printing technology, the printing material is high-temperature resistant photosensitive resin.

8. The method according to claim 7, characterized in that, When using digital light processing 3D printing technology, a high-temperature resistant photosensitive resin suitable for the 405nm curing band is used. The preparation parameters include: light intensity of 35mW / cm2, exposure time of 1s per layer, and layer thickness of 0.02mm.

9. The method for preparing the 3D negative Poisson's ratio metamaterial according to claim 5, characterized in that, When using laser selective melting 3D printing, the printing material is maraging steel powder.

10. The method for preparing the 3D negative Poisson's ratio metamaterial according to claim 9, characterized in that, When using selective laser melting (SLM) 3D printing, the maraging steel powder is Fe-14Ni-16Co-9Mo-0.9Ti powder with a particle size of 15-53µm. The preparation parameters include: laser power of 250W, scanning speed of 900 mm / s, scanning spacing of 0.11mm, layer thickness of 30µm, and scanning strategy of strip scanning.

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