Negative expansion and negative Poisson's ratio integrated heterogeneous metamaterial structure

Abstract

The invention belongs to the technical field of additive manufacturing, and particularly relates to a negative expansion and negative poisson ratio integrated heterogeneous metamaterial structure. The structure at least comprises a cell structure, the cell structure comprises two heterogeneous arch-shaped curved bars, two straight bars and two Y-shaped connecting pieces, the upper ends and the lower ends of the two heterogeneous arch-shaped curved bars are connected through the straight bars respectively to form an hourglass-shaped structure, and the two ends of the belly are each connected with one Y-shaped connecting piece. The thermal expansion coefficient of the convex side material of the heterogeneous arched curved bar is larger than that of the concave side material of the heterogeneous arched curved bar, the heterogeneous arched curved bar can be bent inwards when the temperature rises, and the negative thermal expansion characteristic can be achieved on the whole. When an external force acts on the cell structure, the material shows a unique negative Poisson's ratio behavior. The mechanical property of the structure is adjusted by changing the angle of the convex side material relative to the midpoint of the edge of a single unit cell to be combined with the inner side material, an innovative material with the negative Poisson's ratio characteristic is formed, and the negative Poisson's ratio material has important application value in high-precision equipment, buildings and mechanical structures.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and in particular relates to a heterogeneous metamaterial structure integrating negative expansion and negative Poisson's ratio. Background Art

[0002] The engineering applications of materials with both negative thermal expansion and negative Poisson's ratio are expanding across a wide range of fields. In precision instruments and optical devices, these materials effectively offset errors caused by temperature fluctuations, ensuring high stability. In aerospace, lightweight, high-strength materials combining these two properties improve the heat and impact resistance of aircraft. Furthermore, the unique properties of negative Poisson's ratio materials enable protective equipment to effectively absorb energy during impact, providing enhanced protection. Medical devices and electronic equipment also benefit from these materials, ensuring their stability and performance in diverse environments. In civil engineering, these materials help improve the durability and deformation resistance of buildings and infrastructure. For example, in bridge construction, their use can reduce stress caused by thermal expansion and contraction, lowering maintenance costs. Furthermore, the application of negative Poisson's ratio materials is particularly important in seismic regions, as they effectively absorb and dissipate energy during external impacts, thereby enhancing the seismic performance of structures. In road and tunnel construction, their use can improve overall strength and reduce cracking, thereby extending service life. With the increasing demand for intelligent and high-performance materials, materials with both negative thermal expansion and negative Poisson's ratio will open up a wider range of applications in civil engineering. Summary of the Invention

[0003] The purpose of the present invention is to provide a heterogeneous metamaterial structure integrating negative expansion and negative Poisson's ratio, so that it has negative thermal expansion coefficient and negative Poisson's ratio performance to solve the thermal stability and vibration isolation problems in space environment.

[0004] To achieve the above object, the present invention adopts the following technical solutions: A heterogeneous metamaterial structure with negative expansion and negative Poisson's ratio includes at least one cellular structure, which includes two heterogeneous bow-shaped curved rods, two straight rods and two Y-shaped connectors. The upper and lower ends of the two heterogeneous bow-shaped curved rods are connected by a straight rod to form an hourglass-shaped structure, and the two ends of the abdomen are each connected to a Y-shaped connector.

[0005] Furthermore, the angle of the convex side material of the heterogeneous bow-shaped curved rod compared to the midpoint of the edge of a single cell varies in the range of 0° to 50°.

[0006] Furthermore, the thermal expansion coefficient of the material of the convex side of the heterogeneous arched curved rod is greater than the thermal expansion coefficient of the material of the concave side.

[0007] Furthermore, the ratio of the thermal expansion coefficient of the convex side material to the thermal expansion coefficient of the concave side material of the heterogeneous bow-shaped curved rod is in the range of (2-15):1.

[0008] Furthermore, the thermal expansion coefficient of the convex side material of the heterogeneous bowed curved rod is in the range of 12×10 -6 ℃ -1 ~24×10 -6 ℃ -1 .

[0009] Furthermore, the thermal expansion coefficient of the heterogeneous bow-shaped curved rod concave material ranges from 1.2×10 -6 ℃ -1 ~10.7×10 -6 ℃ -1 .

[0010] Furthermore, the material of the convex side of the heterogeneous bow-shaped curved rod is selected from at least one of 5A02 aluminum alloy, 1Cr18Ni9 stainless steel, AlSi10Mg aluminum alloy, and 2B50 aluminum alloy.

[0011] Furthermore, the concave side material of the heterogeneous bow-shaped curved rod is selected from at least one of Invar alloy and 1Cr13 stainless steel.

[0012] Furthermore, the temperature range of the zero thermal expansion performance of the cell structure is 0°C to 100°C.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) When the spatial temperature of the structure provided by the present invention changes, the heterogeneous bow-shaped curved rod will bend further inward in the axial direction due to the difference in the linear thermal expansion coefficients of the two materials, thereby causing the cell structure to shrink downward as a whole to form a negative expansion effect. The effect of adjusting the thermal expansion coefficient of the heterogeneous cell can be achieved by adjusting the angle of the convex side material compared to the midpoint of the edge of a single cell. The linear thermal expansion coefficient of the base material can also be adjusted to make the metamaterial achieve the effect of adjustable macroscopic thermal expansion coefficient.

[0014] (2) When an external force acts on the cell structure of the structure provided by the present invention, the material on both sides of the cell will bend inward, causing the lateral width of the cell to decrease, exhibiting a unique negative Poisson's ratio behavior. That is, when the material is subjected to vertical pressure, the material shows a tendency to contract in the lateral direction, and conversely, when subjected to tension, it shows an expansion trend.

[0015] (3) The structure of the present invention can be used in some high-precision equipment to offset the expansion of other materials, thereby achieving better temperature stability and ensuring consistent performance of the equipment at different temperatures; in buildings and mechanical structures, it can be used to reduce deformation caused by temperature changes and improve the stability and durability of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1Schematic diagram of the arrangement structure of multiple cell arrays of the present invention.

[0017] Figure 2 Schematic diagram of the heterogeneous bowed curved rod of the cell structure of the present invention.

[0018] Figure 3 Schematic diagram of a single cell structure of the present invention.

[0019] Figure 4 It is an axonometric diagram of a single cell structure of the present invention.

[0020] Figure 5 Graph showing the relationship between the angle of the convex side material of a single cell and the thermal expansion coefficient compared to the midpoint of the edge of a single cell of the present invention.

[0021] Figure 6 Graph showing the relationship between the angle of the convex side material of the unit cell of the present invention compared to the midpoint of the edge of a single unit cell and the Poisson's ratio of the unit cell at a compression of 10% of the unit cell height. DETAILED DESCRIPTION

[0022] To facilitate understanding of the present invention, the present invention will be described more fully below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0023] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0024] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods. Example 1

[0025] like Figure 1 As shown, a negative expansion and negative Poisson's ratio integrated heterogeneous metamaterial structure is composed of multiple cell structure arrays. The cell structure includes two heterogeneous bow-shaped curved rods ( Figure 2 ), two straight rods and two Y-shaped connectors, the upper and lower ends of the two heterogeneous bow-shaped curved rods are connected by a straight rod to form an hourglass-shaped structure ( Figure 3 ), with a Y-shaped connector at each end of the abdomen, which is printed in one piece using additive manufacturing technology.

[0026] The height of the heterogeneous bow-shaped curved rod of this heterogeneous metamaterial structure is L1, the length of the straight rod connecting the heterogeneous bow-shaped curved rod is L2, the angle of the convex side material compared to the midpoint of the edge of a single cell is θ, the side length of the plane unit cell is A1, and the cell thickness is t1.

[0027] The thermal expansion performance of the cell structure was verified using the numerical simulation software Abaqus. Solid elements were used, and the three-dimensional solid mesh type was C3D8R, with eight-node linear hexahedral elements, reduced integration, hourglass control, and a global seed size of 2 mm (this divides each curved beam into five layers of mesh to ensure the accuracy of the calculation results). The convex side material used had a Young's modulus E1 = 70 GPa and a thermal expansion coefficient α1 = 1.5 × 10 -5 ℃ -1 AlSi10Mg aluminum alloy; the concave side material uses Young's modulus E2=144GPa, thermal expansion coefficient α2=1.5×10 -6 ℃ -1 The ratio of the thermal expansion coefficients of the two groups of materials is α1 / α2=10.

[0028] Fully constrain one vertex at the bottom of the superstructure material, fix the corresponding vertices in the x direction in the y and z directions, release the x direction, and only constrain the remaining two vertices in the y direction. The angle change range of the convex side material compared to the midpoint of the edge of a single cell is 0°-50°, the initial temperature is 0℃, and the temperature change ∆T=100.

[0029] Figure 5 This is a graph showing the relationship between the angle of the convex side material of the implemented superstructure cell compared to the midpoint of the edge of a single cell and the thermal expansion coefficient. As can be seen from the figure, the convex side material has good controllable thermal expansion coefficient when the angle range of the convex side material compared to the midpoint of the edge of a single cell is 0°~50°, and the controllable thermal expansion coefficient range reaches -4.78e -5 ~1.50e -6 When the angle of the convex side material relative to the midpoint of the edge of a single cell is 2°, it is close to absolute zero thermal expansion. Example 2

[0030] The difference from Example 1 is that four reference points rp1, rp2, rp3, and rp4 are taken at the center positions of the upper, lower, left, and right surfaces of the superstructure material and coupled to the surfaces respectively. The bottom end of the cell is fully constrained, and the cell is vertically compressed by 12 mm (10% of the cell height). The nodes rp1, rp2, and rp3 in the model are logically grouped to obtain the force and displacement curve of the cell. The angle variation range of the convex side material compared to the midpoint of the edge of a single cell is 0°-50°.

[0031] Figure 6This graph shows the relationship between the angle of the convex side material of the implemented unit cell and the Poisson's ratio of the cell at a 10% cell height compression. The graph shows that the cell exhibits unique negative Poisson's ratio behavior when the angle of the cell edge midpoint varies from 0° to 50°, with a Poisson's ratio between -1.28 and -1.24, demonstrating stable negative Poisson's ratio performance.

[0032] The above description is only for better explanation of the embodiments of the present invention and is not intended to limit the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are intended to be within the scope of the present invention.

Claims

1. A heterogeneous metamaterial structure with negative expansion and negative Poisson's ratio, characterized in that: It includes at least one cell structure, which includes two heterogeneous bow-shaped curved rods, two straight rods and two Y-shaped connectors. The upper and lower ends of the two heterogeneous bow-shaped curved rods are connected by a straight rod to form an hourglass-shaped structure, and the two ends of the abdomen are each connected to a Y-shaped connector.

2. The negative expansion and negative Poisson's ratio integrated heterogeneous metamaterial structure according to claim 1, characterized in that: The angle of the convex side material of the heterogeneous bowed curved rod compared to the midpoint of the edge of a single cell varies from 0° to 50°.

3. The negative expansion and negative Poisson's ratio integrated heterogeneous metamaterial structure according to claim 1, characterized in that: The thermal expansion coefficient of the material on the convex side of the heterogeneous arched curved rod is greater than the thermal expansion coefficient of the material on the concave side.

4. The negative expansion and negative Poisson's ratio integrated heterogeneous metamaterial structure according to claim 3, characterized in that: The ratio of the thermal expansion coefficient of the convex side material to the thermal expansion coefficient of the concave side material of the heterogeneous bow-shaped curved rod ranges from (2 to 15):

1.

5. The negative expansion and negative Poisson's ratio integrated heterogeneous metamaterial structure according to claim 4, characterized in that: The thermal expansion coefficient of the convex side material of the heterogeneous arched curved rod ranges from 12×10 -6 ℃ -1 ~24×10 -6 ℃ -1 .

6. The negative expansion and negative Poisson's ratio integrated heterogeneous metamaterial structure according to claim 4, characterized in that: The thermal expansion coefficient of the material of the heterogeneous bow-shaped curved rod is in the range of 1.2×10 -6 ℃ -1 ~10.7×10 -6 ℃ -1 .

7. The negative expansion and negative Poisson's ratio integrated heterogeneous metamaterial structure according to claim 1, characterized in that: The material of the convex side of the heterogeneous bow-shaped curved rod is selected from at least one of 5A02 aluminum alloy, 1Cr18Ni9 stainless steel, AlSi10Mg aluminum alloy, and 2B50 aluminum alloy.

8. The negative expansion and negative Poisson's ratio integrated heterogeneous metamaterial structure according to claim 1, characterized in that: The concave side material of the heterogeneous bow-shaped curved rod is selected from at least one of Invar alloy and 1Cr13 stainless steel.

9. The negative expansion and negative Poisson's ratio integrated heterogeneous metamaterial structure according to claim 1, characterized in that: The temperature range of the zero thermal expansion performance of the cell structure is 0°C to 100°C.

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