Multifunctional hierarchical dot lattice structures and design methods

Abstract

This invention relates to the field of metamaterials technology, and more specifically to a multifunctional hierarchical lattice structure and its design method. Using a single cell as the basic unit, multiple single cells are periodically spliced ​​together to form a whole. The single cell is a hierarchical composite structure, including an upper cover plate, a lower cover plate, a honeycomb wall panel, and an internal micro-lattice. The honeycomb wall panel is a closed regular hexagonal honeycomb structure, retaining a continuous outer wall of a predetermined thickness, with its internal solid core area replaced by an internal micro-lattice of the same mass as the solid core. An upper cover plate and a lower cover plate are respectively provided on the upper and lower sides of the honeycomb wall panel. An embedded tube is provided on the upper cover plate. This multifunctional hierarchical lattice structure can simultaneously achieve low-bandwidth sound absorption, lightweight and high-strength properties, and broadband wave absorption.

Description

Technical Field

[0001] This invention relates to the field of metamaterials technology, and more specifically to a multifunctional hierarchical lattice structure and its design method. Background Technology

[0002] In high-end fields such as aerospace, rail transportation, and defense equipment, the coupling effects of strong noise and complex electromagnetic fields are prevalent in service environments, posing severe challenges to system safety and performance. Strong noise within the cabin not only reduces personnel comfort and work efficiency but can also affect the stable operation of structures and equipment through reverberation and coupling effects, even inducing malfunctions. Meanwhile, electromagnetic interference is becoming increasingly prominent in information-based equipment, interfering with the normal operation of critical electronic systems and potentially causing signal leakage and functional failures, thereby affecting the equipment's stealth and operational reliability. Against this backdrop, as equipment develops towards lightweight and high-performance designs, single-function structures are no longer sufficient to meet the application requirements of multi-field coupling environments. Structural design is gradually shifting towards multi-functional integration and synergistic optimization. Therefore, developing lightweight integrated structures that balance load-bearing capacity, acoustic control, and electromagnetic protection has become an important development direction for improving the overall service performance of equipment. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the present invention provides a multifunctional hierarchical lattice structure and design method, the beneficial effect of which is that the multifunctional hierarchical lattice structure can take into account low bandwidth sound absorption, lightweight and high strength and bandwidth wave absorption functions.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] The multifunctional hierarchical lattice structure uses a single cell as the basic unit, with multiple single cells periodically spliced ​​together to form a whole. The single cell is a hierarchical composite structure, including an upper cover plate, a lower cover plate, a honeycomb wall panel, and an internal micro-lattice. The honeycomb wall panel is a closed regular hexagonal honeycomb structure, retaining a continuous outer wall of a set thickness, and its internal solid core area is replaced with an internal micro-lattice of the same mass as the solid core. The upper and lower sides of the honeycomb wall panel are respectively provided with an upper cover plate and a lower cover plate. An embedded tube is provided on the upper cover plate.

[0006] The built-in micro-lattice can improve the stress concentration state and mechanical transmission path of the structure, and enhance the specific modulus, specific strength and specific energy absorption performance of the structure under the same mass fraction.

[0007] The embedded tubes on the top cover plate form a resonant system with the internal cavity of the unit cell, thus having sound absorption characteristics; the built-in micro array adopts Gyroid array, and the air domain enclosed by the honeycomb wall panel and the porous region of the Gyroid array are interconnected to form a dual-pore resonant system. The dual-pore systems are interconnected, thus providing dissipation gain for the resonant system.

[0008] The built-in micro-lattice is an extremely small curved surface lattice or truss lattice with highly interconnected pores.

[0009] Multiple units are arranged and combined to form a modular multi-unit sound-absorbing array, which achieves broadband sound absorption through coupled resonance.

[0010] The upper and lower cover plates are made of materials with dielectric constants close to that of air, which facilitates impedance matching and allows more electromagnetic waves to enter the structure. By adjusting the sheet resistance of the coating, the matching characteristics between the lattice and the absorbing coating can be optimized, thereby improving the impedance matching between the absorbing structure and free space.

[0011] The built-in micro-array is loaded with a wave-absorbing coating, which enables efficient reconstruction and distribution optimization of the wave-absorbing material in space through its three-dimensional spatial configuration. The porous structure and high specific surface area of ​​the built-in micro-array are conducive to enhancing the multiple reflection effect of electromagnetic waves inside the structure and promoting surface eddy current loss, thereby significantly improving the overall electromagnetic wave absorption performance.

[0012] The microwave absorbing coating is prepared by mixing carbon nanotubes, carbon black, alcohol, polyurethane and defoamer in a certain proportion and stirring evenly with a mixer. Different proportions of carbon nanotubes, carbon black, alcohol and polyurethane can produce different sheet resistances, so that the sheet resistance of the microwave absorbing coating is continuously controllable and adjustable, and the structural impedance matching is optimized.

[0013] The cell wall thickness, cell side length, and microlattice volume fraction geometric parameters can be flexibly adjusted.

[0014] A design method for a multifunctional hierarchical lattice structure includes the following steps:

[0015] Step 1: Determine the geometric parameters of the unit cell, replace the solid core inside the honeycomb wall panel with an equal mass of built-in micro-lattice, and complete the structural design;

[0016] Step 2: Use 3D printing technology to prepare a structural matrix consisting of an upper cover plate, a lower cover plate, a honeycomb wall panel, and an internal micro-lattice.

[0017] Step 3: Prepare a microwave absorbing coating solution with a specific sheet resistance according to the ratio, immerse the printed structure substrate in the coating solution to achieve uniform coating load on the built-in micro-array surface;

[0018] Step 4: An acoustically optimized embedded tube is installed on the upper cover plate to form a dual-pore resonant sound absorption structure with the internal air domain and the micro-array porous area.

[0019] Step 5: Based on the modular array requirements, the multi-cell unit cells are designed in a parallel integrated configuration. The multi-cell unit structure is prepared by 3D printing. Each unit cell is directly and continuously connected through a honeycomb wall panel to obtain an integrated modular parallel sound-absorbing array.

[0020] The beneficial effects of the multifunctional hierarchical lattice structure and design method of this invention are:

[0021] A multifunctional hierarchical lattice acoustic metamaterial structure is provided, which achieves synergistic enhancement of mechanical, electromagnetic, and acoustic properties through structural design.

[0022] The overall structure is based on a single cell as the basic unit, with multiple single cells being extended and spliced ​​in a two-dimensional periodic manner; the single cell is a hierarchical composite structure, including upper and lower cover plates, honeycomb wall panels and filling lattice.

[0023] The outer honeycomb wall panel is a closed regular hexagonal structure with uniform wall thickness. The continuous outer wall is retained to ensure rigidity, while the internal solid core is replaced with an equal mass lattice, and the two are seamlessly bonded together.

[0024] The cover plate matches the cross-section of the unit cell, and its edges are sealed to the honeycomb wall panel. The cover plate has perforations based on acoustic optimization, which communicate with the interior of the unit cell to form a dual-pore resonance system.

[0025] A microwave absorbing coating solution with a specific sheet resistance is prepared by mixing carbon nanotubes, carbon black, alcohol, polyurethane, and defoamer in a certain proportion.

[0026] It is manufactured using 3D printing technology and then immersed in a coating solution to cover the surface of the structure.

[0027] A parallel sound-absorbing array can be formed by arranging unit cells into a matrix. The array is directly modeled and manufactured in a parallel configuration. By optimizing the embedded tube radius and length of each unit cell, the multi-cell units can generate coupled resonance, thereby achieving broadband sound absorption.

[0028] Key geometric parameters of the unit cell, such as cell wall thickness, unit cell side length, and lattice volume fraction, can be flexibly adjusted to adapt to different application scenarios.

[0029] By employing a hierarchical structural design, the problem of poor functional compatibility in existing metamaterials is addressed, achieving synergistic enhancement of mechanical, electromagnetic, and acoustic properties. In terms of mechanical performance, due to its layered design and the low stress concentration advantage of its minimally shaped curved lattice, the multifunctional hierarchical lattice structure overcomes the limitations of traditional honeycomb structures in in-plane mechanical behavior. Compared to other lattice structures known for their mechanical properties, the multifunctional hierarchical lattice structure exhibits superior energy absorption capabilities at low densities. Regarding electromagnetic performance, the structure-material hybrid design of the multifunctional hierarchical lattice structure provides more flexible impedance adjustment capabilities. Compared to other absorption structures known for their electromagnetic properties, the multifunctional hierarchical lattice structure exhibits broadband absorption through multiple internal reflection mechanisms. In terms of acoustic performance, the dual-hole resonant system of the multifunctional hierarchical lattice structure contributes to a more efficient acoustic energy dissipation mechanism, enhancing its sound absorption capabilities. Especially after array-level optimization, it achieves a wider effective absorption bandwidth while maintaining a relatively thin structural thickness. Attached Figure Description

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific implementation methods.

[0031] Figure 1 An exploded view of a unit cell in a multifunctional hierarchical lattice structure;

[0032] Figure 2 This is a schematic diagram of the structure of a single cell in a multifunctional hierarchical lattice structure.

[0033] Figure 3 This is a schematic diagram of the cross-sectional structure of a single cell in a multifunctional hierarchical lattice structure.

[0034] Figure 4 This is a schematic diagram of the built-in micro-array structure;

[0035] Figure 5 This is a curve comparing the mechanical properties of the multifunctional hierarchical lattice structure of this invention with those of a traditional honeycomb structure.

[0036] Figure 6 The reflection loss spectrum of the multifunctional hierarchical lattice structure of this invention in the 2-40GHz frequency band is shown.

[0037] Figure 7 This is a comparison chart of the sound absorption coefficients of the single cell of this invention and conventional acoustic structures in the 550-950Hz frequency band;

[0038] Figure 8 A schematic diagram of a custom sound-absorbing array structure formed by modular splicing of multiple unit cells;

[0039] In the diagram: 1. Upper cover plate; 2. Embedded insertion tube; 3. Built-in micro-matrix; 4. Honeycomb wall panel; 5. Lower cover plate. Detailed Implementation

[0040] To make the technical solution and advantages of this application clearer, the technical solution of this application will be described in a clearer and more complete manner below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of this application, and are only used to explain this application, not to limit this application. This embodiment clarifies the hierarchical structure characteristics protected by this invention through specific structural parameters. Its performance advantages are determined by the core structure and parameter design. The specific parameters and descriptions are as follows:

[0041] like Figure 1-4As shown in Figure 8, the multifunctional hierarchical lattice structure of the present invention uses a single cell as the basic unit, and multiple single cells are periodically spliced ​​together to form a whole; the single cell is a hierarchical composite structure, including an upper cover plate 1, a lower cover plate 5, a honeycomb wall panel 4, and an internal micro-lattice 3; the honeycomb wall panel 4 is a closed regular hexagonal honeycomb structure, retaining a continuous outer wall of a set thickness, and its internal solid core area is replaced with an internal micro-lattice 3 of the same mass as the solid core; the upper and lower sides of the honeycomb wall panel 4 are respectively provided with an upper cover plate 1 and a lower cover plate 5; an embedded tube 2 is provided on the upper cover plate 1.

[0042] The built-in micro-lattice 3 can improve the stress concentration state and mechanical transmission path of the structure, and improve the specific modulus, specific strength and specific energy absorption performance of the structure under the same mass fraction.

[0043] The embedded tube 2 on the upper cover plate 1 forms a resonance system with the internal cavity of the unit cell, thus having sound absorption characteristics; the built-in micro array 3 adopts Gyroid array, and the air domain enclosed by the honeycomb wall panel 4 and the porous region of the Gyroid array are interconnected to form a dual-pore resonance system. The dual-pore systems are interconnected, thus providing dissipation gain for the resonance system.

[0044] The built-in micro-lattice 3 is an extremely small curved surface lattice or truss lattice with highly interconnected pores.

[0045] Multiple units are arranged and combined to form a modular multi-unit sound-absorbing array, which achieves broadband sound absorption through coupled resonance.

[0046] The upper cover plate 1 and the lower cover plate 5 are made of materials with dielectric constants close to that of air, which is beneficial for impedance matching and allows more electromagnetic waves to enter the interior of the structure. By adjusting the sheet resistance of the coating, the matching characteristics between the lattice and the absorbing coating can be optimized, thereby improving the impedance matching between the absorbing structure and free space.

[0047] The built-in micro-array 3 is loaded with a wave-absorbing coating, which enables efficient reconstruction and distribution optimization of the wave-absorbing material in space through its three-dimensional spatial configuration. The porous structure and high specific surface area of ​​the built-in micro-array 3 are conducive to enhancing the multiple reflection effect of electromagnetic waves inside the structure and promoting surface eddy current loss, thereby significantly improving the overall electromagnetic wave absorption performance.

[0048] The microwave absorbing coating is prepared by mixing carbon nanotubes, carbon black, alcohol, polyurethane and defoamer in a certain proportion and stirring evenly with a mixer. Different proportions of carbon nanotubes, carbon black, alcohol and polyurethane can produce different sheet resistances, so that the sheet resistance of the microwave absorbing coating is continuously controllable and adjustable, and the structural impedance matching is optimized.

[0049] The cell type, cell size, honeycomb wall thickness, cell side length, and microlattice volume fraction of the unit cell can be flexibly adjusted.

[0050] The specific structural parameters and characteristics of the multifunctional hierarchical lattice structure are as follows:

[0051] The honeycomb wall panel 4 adopts a closed regular hexagonal structure with a single cell side length of 15mm and a honeycomb wall thickness of 1mm. The wall thickness is uniform, and a continuous outer wall is retained to ensure overall rigidity. The solid core area inside is replaced with an internal micro-lattice 3 of the same mass as the core. The two are seamlessly bonded, and the internal micro-lattice 3 has a volume fraction of 30%. This structure not only retains the rigidity advantage of the honeycomb, but also makes up for the performance shortcomings of the single honeycomb structure by filling with internal micro-lattice 3. It is the core of the mechanical performance improvement of the present invention.

[0052] The built-in micro-lattice 3 is a Gyroid lattice, belonging to the category of minimal surface lattices. At the millimeter scale, this built-in micro-lattice 3 exhibits resistive dissipation similar to porous materials, enhancing the acoustic energy dissipation capability of the resonant system. However, it is not limited to a single lattice type; theoretically, this design method is applicable to other micro-lattice structures with interconnected pore features. Furthermore, the acoustic model of the built-in micro-lattice 3 can be described using the JCA model for acoustic theoretical calculations and finite element simulations.

[0053] The upper cover plate 1 and the lower cover plate 5 are precisely matched and sealed to the hexagonal cross-section of the unit cell. The upper cover plate 1 and the lower cover plate 5 are 2mm thick and are made of a material with a dielectric constant close to that of air, with a dielectric constant ε≈1.2, which is beneficial for impedance matching. The upper cover plate 1 is provided with an embedded tube 2 based on acoustic optimization. The diameter and length of the embedded tube 2 are adjustable. Together with the air domain and the lattice porous area enclosed by the honeycomb wall panel 4, they form a dual-pore resonance system, which is the core structure of the acoustic sound absorption performance of this invention.

[0054] Multiple unit cells can be arranged to form a parallel sound-absorbing array. All perforated cover plates of unit cells face the same direction. Wideband sound absorption performance can be optimized by optimizing the diameter and length of the embedded tube 2 of the unit cell. The geometric parameters of the unit cell can be flexibly adjusted. The honeycomb wall thickness of the honeycomb panel 4 can be adjusted from 0.8 to 1.2 mm, the side length of the unit cell can be adjusted from 12 to 18 mm, and the lattice volume fraction can be adjusted from 25% to 35% to adapt to different scenarios.

[0055] like Figure 5 As shown, the continuous outer wall of the honeycomb wall panel 4 ensures the rigidity of the foundation, and the built-in micro-array 3 has the advantage of low stress concentration. The two work together to increase the specific modulus of the structure by 63.9%, the specific strength by 54.7%, and the specific energy absorption by 21.9 times compared with the single honeycomb structure.

[0056] The structural matrix of this invention is made of photosensitive resin and manufactured by 3D printing. The matrix includes an upper cover plate 1, a lower cover plate 5, a honeycomb wall 4, and an internal micro-lattice 3. The dielectric constant ε≈1.2. The microwave absorbing coating is made of carbon nanotubes and carbon black mixed in a 1:1 mass ratio, combined with alcohol and polyurethane. By precisely controlling the mass fraction of the carbon black-carbon nanotube composite filler, the sheet resistance R of the coating surface can be continuously adjusted in the range of 200–3000 Ω / sq.

[0057] like Figure 6 As shown, the multifunctional hierarchical lattice structure can work in conjunction with the absorbing coating to achieve broadband electromagnetic absorption in 93.5% of the 2-40GHz frequency band by optimizing the sheet resistance of the absorbing coating.

[0058] The cover plate perforation is a circular through hole with a diameter of 3.4 mm and a perforation rate of 8% opened in the upper cover plate 1, such as... Figure 7 As shown, the perforated cover plate, combined with the dual-pore resonance system, enables the single cell to achieve near-perfect sound absorption at 556Hz, and the array structure achieves an average sound absorption coefficient of over 0.88 in the 600-900Hz frequency band.

[0059] The design method for a multifunctional hierarchical lattice structure includes the following steps:

[0060] Step 1: Determine the unit cell geometry parameters, replace the solid core inside the honeycomb wall panel 4 with an internal micro-lattice 3 of equal mass, and complete the structural design;

[0061] Step 2: Use 3D printing technology to prepare a structural matrix consisting of an upper cover plate 1, a lower cover plate 5, a honeycomb wall panel 4, and an internal micro-lattice 3;

[0062] Step 3: Prepare a microwave absorbing coating solution with a specific sheet resistance according to the ratio, immerse the printed structure substrate in the coating solution to achieve uniform coating load on the surface of the built-in micro-array 3.

[0063] Step 4: An acoustically optimized embedded tube 2 is installed on the upper cover plate 1 to form a dual-pore resonant sound absorption structure with the internal air domain and the micro-array porous area.

[0064] Step 5: Based on the modular array requirements, the multi-cell unit cell is designed in parallel as an integrated structure. The multi-cell unit cell structure is prepared by 3D printing. Each unit cell is directly and continuously connected through the honeycomb wall panel 4 to obtain an integrated modular parallel sound-absorbing array.

Claims

1. A multifunctional hierarchical lattice structure, using a single cell as the basic unit, with multiple single cells periodically spliced ​​together to form a whole; characterized by: The unit cell is a hierarchical composite structure, including an upper cover plate (1), a lower cover plate (5), a honeycomb wall panel (4), and an internal micro-array (3); the honeycomb wall panel (4) is a closed regular hexagonal honeycomb structure, retaining a continuous outer wall of a set thickness, and its internal solid core area is replaced by an internal micro-array (3) of the same mass as the solid core; the upper cover plate (1) and the lower cover plate (5) are respectively provided on the upper and lower sides of the honeycomb wall panel (4); an embedded tube (2) is provided on the upper cover plate (1).

2. The multifunctional hierarchical lattice structure according to claim 1, characterized in that: The built-in micro-lattice (3) can improve the stress concentration state and mechanical transmission path of the structure, and improve the specific modulus, specific strength and specific energy absorption performance of the structure under the same mass fraction.

3. The multifunctional hierarchical lattice structure according to claim 1, characterized in that: The embedded tube (2) on the upper cover plate (1) forms a resonance system with the internal cavity of the unit cell, thereby having sound absorption characteristics; The built-in micro-array (3) adopts the Gyroid array. The air domain enclosed by the honeycomb wall panel (4) and the porous region of the Gyroid array are interconnected to form a dual-pore resonance system. The dual-pore system is interconnected, thereby providing dissipation gain for the resonance system.

4. The multifunctional hierarchical lattice structure according to claim 1, characterized in that: The built-in micro-lattice (3) is an extremely small curved surface lattice or truss lattice with highly connected pores.

5. The multifunctional hierarchical lattice structure according to claim 1, characterized in that: Multiple units are arranged and combined to form a modular multi-unit sound-absorbing array, which achieves broadband sound absorption through coupled resonance.

6. The multifunctional hierarchical lattice structure according to claim 1, characterized in that: The upper cover plate (1) and the lower cover plate (5) are made of materials with dielectric constants close to that of air, which is conducive to impedance matching and allows more electromagnetic waves to enter the interior of the structure. By adjusting the sheet resistance of the coating, the matching characteristics between the lattice and the absorbing coating can be optimized, thereby improving the impedance matching between the absorbing structure and free space.

7. The multifunctional hierarchical lattice structure according to claim 1, characterized in that: The built-in micro-array (3) is loaded with a wave-absorbing coating. By means of its three-dimensional spatial configuration, the wave-absorbing material can be efficiently reconstructed and its distribution optimized in space. The porous structure and high specific surface area of ​​the built-in micro-array (3) are conducive to enhancing the multiple reflection effect of electromagnetic waves inside the structure and promoting surface eddy current loss, thereby significantly improving the overall electromagnetic wave absorption performance.

8. The multifunctional hierarchical lattice structure according to claim 7, characterized in that: The microwave absorbing coating is prepared by mixing carbon nanotubes, carbon black, alcohol, polyurethane and defoamer in a certain proportion and stirring evenly with a mixer. Different proportions of carbon nanotubes, carbon black, alcohol and polyurethane can produce different sheet resistances, so that the sheet resistance of the microwave absorbing coating is continuously controllable and adjustable, and the structural impedance matching is optimized.

9. The multifunctional hierarchical lattice structure according to claim 1, characterized in that: The cell type, cell size, honeycomb wall thickness, cell side length, and microlattice volume fraction of the unit cell can be flexibly adjusted.

10. A design method for a multifunctional hierarchical lattice structure as described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Determine the geometric parameters of the unit cell, replace the solid core inside the honeycomb wall panel (4) with an internal micro-lattice (3) of equal mass, and complete the structural design; Step 2: Use 3D printing technology to prepare a structural matrix consisting of an upper cover plate (1), a lower cover plate (5), a honeycomb wall panel (4), and an internal micro-lattice (3); Step 3: Prepare a microwave absorbing coating solution with a specific sheet resistance according to the ratio, immerse the printed structure substrate in the coating solution to achieve uniform coating load on the surface of the built-in micro-array (3); Step 4: An acoustically optimized embedded tube (2) is installed on the upper cover plate (1) to form a double-pore resonant sound absorption structure with the internal air domain and the micro-array porous area; Step 5: Based on the modular array requirements, the multi-cell unit cell is designed in parallel and integrated configuration. The multi-cell unit cell structure is prepared by 3D printing. Each unit cell is directly and continuously connected through the honeycomb wall panel (4) to obtain an integrated modular parallel sound-absorbing array.

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