Nested gradient honeycomb structure

Abstract

The invention provides a nested honeycomb structure which comprises six layers of cell element structures arranged in sequence, every two layers of cell element structures form a gradient level, and the six layers of cell element structures are a first gradient level, a second gradient level and a third gradient level in sequence from bottom to top. The first gradient level comprises first-level cell elements, and the first-level cell elements are sequentially arranged to form a two-layer nested gradient honeycomb structure; the second gradient level comprises a first-level cell element and second-level cell elements, and two second-level cell elements are arranged in the first-level cell element; the third gradient level comprises a first-level cell element and three-level cell elements, and the first-level cell element is internally provided with three third-level cell elements. According to the structure, a nested gradient honeycomb structure is constructed by combining a nested structure with a traditional circular honeycomb and a hexagonal honeycomb, so that the traditional honeycomb structure can be damaged layer by layer during in-plane loading, the deformation capacity of the structure is fully utilized, and the in-plane rigidity and the energy absorption capacity of the traditional honeycomb structure are improved.

Description

Technical Field

[0001] The present invention belongs to the honeycomb structure, and particularly relates to a nested gradient honeycomb structure. Background Art

[0002] Due to its lightweight and high-strength characteristics, the traditional honeycomb structure has been widely used in fields such as aerospace, automotive, and sports protection. For example, the energy absorption device at the front end of a car usually adopts a honeycomb structure energy absorption box, which can effectively absorb the impact energy during a collision and reduce vehicle damage. The honeycomb structure sandwich protection layer in the aerospace engine housing plays an effective role in anti-impact and shock absorption, protecting the engine from external impacts. However, with the increasing complexity and high speed of external loads, when the traditional honeycomb structure faces a more severe use environment, its performance in aspects such as energy absorption effect and anti-impact performance can no longer fully meet the requirements of modern engineering. Especially in scenarios such as car collisions and aircraft emergency shock absorption, the energy absorption efficiency and dynamic response speed of the traditional honeycomb structure often seem inadequate. Therefore, how to improve the energy absorption capacity and anti-impact performance of the honeycomb structure under extreme loads has become a key problem to be solved urgently. Summary of the Invention

[0003] The purpose of the present invention is to solve the problems of the energy absorption capacity and anti-impact performance of the honeycomb structure under extreme loads.

[0004] To achieve the above purpose, the present invention provides a nested gradient honeycomb structure, which includes six layers of cell structures. The six layers of cell structures are arranged and connected in sequence to form a honeycomb structure. Every two layers of cell structures form a gradient level, which are the first gradient level, the second gradient level, and the third gradient level from bottom to top; among them, The first gradient level includes first-level cells; The second gradient level includes first-level cells and second-level cells, and two second-level cells are arranged inside the first-level cell; The third gradient level includes first-level cells and third-level cells, and three third-level cells are arranged inside the first-level cell.

[0005] Furthermore, the wall thicknesses of the first-level cells, the second-level cells, and the third-level cells are all equal, which is 0.4 mm.

[0006] Furthermore, the shapes of the first-level cells, the second-level cells, and the third-level cells are all hexagons or circles.

[0007] Furthermore, the honeycomb structure is prepared by 3D printing technology, and the printing substrate can be selected from AlSi10Mg aluminum alloy or Ti6Al4V titanium alloy.

[0008] Advantageous Effects: The nested gradient honeycomb structure of the present application has significant advantages in mechanical properties. By embedding small units into large units, this design effectively optimizes the stress distribution of the honeycomb structure under pressure loads, and improves the overall compressive strength and energy absorption efficiency of the structure. The multi-level characteristics of the nested structure enable it to exhibit different deformation mechanisms and layer-by-layer failure characteristics when subjected to stress, such as the coordination of local buckling and overall buckling, thereby delaying the failure process and improving the stability of the structure.

[0009] In addition, the nesting of internal and external units provides additional support, reduces the risk of overall collapse caused by local instability, and further enhances structural stability. The versatility brought by the gradient design allows the mechanical properties of different regions and directions to be precisely controlled, which is particularly important in complex environments where both stiffness and energy absorption need to be taken into account. Through this design, the utilization rate of materials is improved, and a combination of lightweight and high performance is achieved, especially under dynamic impact or collision conditions. Nested gradient honeycombs can extend the impact time through a progressive deformation mode, reduce the impact of the peak impact force on the main structure, and significantly improve the impact resistance. This design is of great value in engineering applications in the fields of aerospace, automotive safety structures, etc., and achieves excellent mechanical properties and comprehensive optimization of material utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The nested circular gradient honeycomb structure of the present invention; Figure 2 It is a schematic diagram of the nested circular gradient honeycomb plane structure; Figure 3 A schematic diagram of each level of cells of the nested circular gradient honeycomb provided by the present invention; Figure 4 The nested hexagonal gradient honeycomb structure provided by the present invention Figure 5 A schematic diagram of a nested hexagonal gradient honeycomb plane structure provided by the present invention; Figure 6 A schematic diagram of each level of cells of a nested hexagonal gradient honeycomb provided by the present invention; Figure 7 This is the stress-strain curve of the nested circular gradient honeycomb in-plane loading; Figure 8 The stress-strain curve of the nested hexagonal gradient honeycomb under in-plane loading; Figure 9 It is the deformation mode of circular honeycomb in-plane loading; Figure 9 (a) is the deformation mode of the traditional circular honeycomb in-plane loading; Figure 9 Middle (b) is the in-plane loading deformation mode of nested circular gradient honeycomb; Figure 10 It is the deformation mode of internal loading in a hexagonal honeycomb surface; Figure 10 In (a), it is the deformation mode of internal loading in a traditional hexagonal honeycomb surface; Figure 10 In (b), it is the deformation mode of internal loading in a nested hexagonal gradient honeycomb surface.

[0011] Reference numerals: 1 - the first gradient level, 2 - the second gradient level, 3 - the third gradient level, 4 - the first - level circular cell, 5 - the second - level circular cell, 6 - the third - level circular cell, 7 - the first - level hexagonal cell, 8 - the second - level hexagonal cell, 9 - the third - level hexagonal cell. Detailed implementation manners

[0012] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0013] The application principle of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0014] Embodiment 1: As Figures 1-6 shown, a nested gradient honeycomb structure includes six - layer cell structures. The six - layer cell structures are arranged in sequence to form a honeycomb structure. Every two - layer cell structures form a gradient level, which are the first gradient level 1, the second gradient level 2, and the third gradient level 3 from bottom to top in sequence.

[0015] Nested circular gradient honeycomb structure: The first gradient level 1 includes the first - level circular cells 4, and the first - level circular cells 4 are arranged and connected in sequence to form a two - layer nested gradient honeycomb structure.

[0016] The second gradient level 2 includes the first - level circular cells 4 and the second - level circular cells 5, and there are two second - level circular cells 5 arranged inside the first - level circular cells 4.

[0017] The third gradient level 3 includes the first - level circular cells 4 and the third - level circular cells 6, and there are three third - level circular cells 6 arranged inside the first - level circular cells 4.

[0018] Among them, the wall thicknesses of the first - level circular cells 4, the second - level circular cells 5, and the third - level circular cells 6 are all equal. The diameters of the first - level circular cells 4, the second - level circular cells 5, and the third - level circular cells 6 are all different.

[0019] In the first gradient level 1, there are two layers of honeycomb structures composed of first-level circular cells 4. The diameter of the first-level circular cells 4 is 4 mm, and the wall thickness of the first-level circular cells 4 is 0.4 mm. The distance from the center to the center between the first-level circular cells 4 is 4 mm. In the second gradient level 2, the second-level circular cells 5 are nested into the first-level circular cells 4 with the same size as in the first gradient level 4, and the first-level circular cells 4 and the second-level circular cells 5 are tangent to each other. The diameter of the second-level circular cells 5 is 2 mm, and the wall thickness is 0.4 mm. In the third gradient level 3, the third-level circular cells 6 are nested into the first-level circular cells 4 with the same size as in the first gradient level 1. The diameter of the third-level circular cells 6 is 1.86 mm, and the thickness is 0.4 mm. The first-level circular cells 4 and the third-level circular cells 6 are tangent to each other.

[0020] For the nested hexagonal gradient honeycomb structure: The first gradient level 1 includes first-level hexagonal cells 7, and the first-level hexagonal cells 7 are arranged and connected in sequence to form a two-layer nested gradient honeycomb structure.

[0021] The second gradient level 2 includes first-level hexagonal cells 7 and second-level hexagonal cells 8, and there are two second-level hexagonal cells 8 inside the first-level hexagonal cells 7.

[0022] The third gradient level 3 includes first-level hexagonal cells 7 and third-level hexagonal cells 9, and there are three third-level hexagonal cells 9 inside the first-level hexagonal cells 7.

[0023] Among them, the wall thicknesses of the structures of the first-level hexagonal cells 7, the second-level hexagonal cells 8, and the third-level hexagonal cells 9 are all equal. The wall side lengths of the first-level hexagonal cells 7 are different from those of the second-level hexagonal cells 8 and the third-level hexagonal cells 9, and the wall side lengths of the second-level hexagonal cells 8 and the third-level hexagonal cells 9 are equal.

[0024] In the first gradient level 1, there are two layers of hexagonal honeycomb structures. The side length of the first-level hexagonal cells 7 is 2.31 mm, and the wall thickness of the first-level hexagonal cells 7 is 0.4 mm. The first-level hexagonal cells 7 are tangent to each other. In the second gradient level, two second-level hexagonal cells 8 are nested into the first-level hexagonal cells 7 with the same size as in the first gradient level 1. In the second gradient level 2, the side length of the second-level hexagonal cells 7 is 1.15 mm, and the wall thickness is 0.4 mm. In the third gradient level 3, three third-level hexagonal cells 9 are nested into the first-level hexagonal cells 7 with the same size as in the first gradient level 1. The side length of the third-level hexagonal cells 9 is 1.15 mm, and the thickness is 0.4 mm.

[0025] Both types of nested gradient honeycombs can be prepared by 3D printing technology, and the printing substrate can be selected from AlSi10Mg aluminum alloy or Ti6Al4V titanium alloy for preparation.

[0026] Under in-plane loading, the nested gradient honeycomb structure deforms and fails successively from the bottom to the top to dissipate the energy during the loading process. The mechanical property indexes used to characterize the nested honeycomb structure under in-plane loading include specific stiffness E s , specific strength σ s , plateau stress σ p and stage plateau stress σ sp , which can be calculated respectively by the following formulas: where E is the elastic modulus in the linear elastic stage, σ and ε are the stress and strain during in-plane loading of the gradient honeycomb respectively, ρ h is the density of the honeycomb structure, ε 0 and ε d are the strain and densification strain corresponding to the initial linear stage respectively, ε 1 and ε 2 are the strains corresponding to two adjacent peaks of the energy absorption efficiency curve respectively; The energy absorption characteristics of the nested gradient honeycomb structure can be represented by energy absorption EA and specific energy absorption SEA , which can be calculated respectively by the following formulas: where V t represents the volume occupied by the honeycomb structure.

[0027] Example 2: The two gradient structures have a total of 3 gradient levels from top to bottom. The bottom is the first gradient level and the top is the third gradient level.

[0028] Please refer to Figures 7-10, the first gradient level structure of the nested circular gradient honeycomb began to deform and fail first, and its deformation mode was similar to the typical failure mode of conventional honeycombs. Then, the first gradient level was completely compacted, and the deformation area extended to the second gradient level structure. In the second gradient level structure, two nested self-similar small-sized circles squeezed each other at the intersection and sheared. The deformation and crushing area gradually expanded to the third gradient level until the structure was completely compressed and compacted. For the nested hexagonal gradient honeycomb structure, when subjected to in-plane loads, large deformation first occurred in the first gradient level structure, and the angle of the bottom honeycomb wall of the hexagonal honeycomb cell in contact with the fixed plate gradually increased from 120° to 180°, and some honeycomb walls even "reverse arched", making the inner angle of the bottom honeycomb wall exceed 180°. The structure absorbs energy through this deformation mode. At this time, no obvious deformation occurred in other gradient levels. When the first gradient level structure is completely destroyed, the second level gradient structure begins to deform, the thickness of the damaged honeycomb structure fragments at the bottom is unevenly distributed, the overall structure is tilted, and its stability is weakened; when the second gradient level has not been completely destroyed, a shear band appears, which cuts the structure apart, causing the structure to tilt more. After that, the crushed area expands to the third gradient level, and the structure is gradually compacted. During the entire process of in-plane compression to compaction of the two gradient honeycomb structures, significant deformation patterns of layered failure can be observed. Since the gradient distribution is weakest at the bottom and strongest at the top, the layered failure begins to deform from the bottom, and then deforms layer by layer to the top. The gradient levels are deformed and destroyed layer by layer, and the structure and material fully absorb energy.

[0029] As shown in Table 1, compared with the traditional hexagonal honeycomb, the platform stress of the nested hexagonal gradient honeycomb is increased by about 126%, while the energy absorption and specific energy absorption are increased by 157% and 64% respectively; compared with the traditional circular honeycomb, the platform stress of the nested circular gradient honeycomb is increased by about 222%, while the energy absorption and specific energy absorption are increased by 206% and 66% respectively; the traditional circular honeycomb is stronger than the traditional hexagonal honeycomb in terms of platform stress, energy absorption and specific energy absorption; compared with the nested hexagonal gradient honeycomb, the platform stress of the nested circular gradient honeycomb is increased by about 78%, while the energy absorption and specific energy absorption are increased by 59% and 34% respectively. In summary, the present invention can improve the energy absorption performance of the traditional honeycomb structure and greatly improve the impact resistance and buffering energy absorption effect of the structure.

[0030] Table 1 Comparison of mechanical properties of honeycomb structures with different gradients The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A nested gradient honeycomb structure, characterized in that: It includes six layers of cell structures, which are arranged and connected in sequence to form a honeycomb structure. Every two layers of cell structures form a gradient level, which are the first gradient level, the second gradient level and the third gradient level from bottom to top. The first gradient level includes a first-level cell; The second gradient level includes a primary cell and a secondary cell, and two secondary cells are arranged in the primary cell; The third gradient level includes a primary cell and a tertiary cell, and three tertiary cells are arranged in the primary cell.

2. The nested gradient honeycomb structure according to claim 1, characterized in that: The wall thickness of the primary cell, secondary cell, and tertiary cell is equal, which is 0.4 mm.

3. The nested gradient honeycomb structure according to claim 1 or 2, characterized in that: The shapes of the primary cells, secondary cells, and tertiary cells are all hexagonal or circular.

4. The nested gradient honeycomb structure according to claim 1, characterized in that: The honeycomb structure is prepared by 3D printing technology, and the printing substrate can be selected from AlSi10Mg aluminum alloy or Ti6Al4V titanium alloy.

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