A local resonance type lattice sandwich metamaterial structure

Abstract

The application provides a kind of local resonance type lattice sandwich metamaterial structure, and belongs to the technical field of acoustic metamaterials.The material solves the technical problems of narrow band gap width of local resonance lattice sandwich structure, and difficulty in simultaneously realizing low-frequency vibration reduction and elastic wave directional transmission.The upper panel and the lower panel of the material are arranged in parallel, and a pyramid lattice core layer is arranged between the upper panel and the lower panel.The pyramid lattice core layer is rigidly connected with the upper panel and the lower panel.The pyramid lattice core layer includes a two-dimensional periodic sandwich phononic crystal arranged at each node.The sandwich phononic crystal is differentially arranged as a first structure variant and a second structure variant with complementary performance.The two structure variants can be used separately or mixedly arranged.The material realizes efficient suppression of super-wide frequency low-frequency bending waves, has good configuration stiffness matching, solves the technical difficulties of the prior art in simultaneously meeting the three requirements of "structure bearing, wide-frequency vibration reduction and directional transmission", has a simple structure, strong process compatibility, and can be directly applied to engineering.

Description

Technical Field

[0001] This invention belongs to the field of acoustic metamaterials technology, and in particular relates to a localized resonant lattice sandwich metamaterial structure. Background Technology

[0002] Lattice sandwich panels are a type of lightweight, high-strength composite structure composed of upper and lower panels and a core layer with a periodic lattice structure in the middle. Due to their excellent specific stiffness, specific strength, and energy absorption performance, they have been widely used in many industrial fields such as aerospace, civil engineering, rail transportation, and automobile manufacturing. However, lattice sandwich structures have inherent defects in low-frequency vibration control. The most harmful low-frequency vibrations in engineering can reach wavelengths of several meters to tens of meters, far exceeding the single-cycle size of the lattice sandwich structure. Vibration suppression in traditional lattice sandwich structures mainly relies on the Bragg scattering effect, and its bandgap frequency is proportional to the lattice constant. To obtain a low-frequency bandgap, the structural size needs to be significantly increased, which contradicts the core advantage of lightweight lattice structures; these shortcomings limit the application of lattice sandwich structures.

[0003] Localized resonance offers a novel approach to solving this problem. By introducing localized oscillators within periodic cells and utilizing the strong resonant coupling between the oscillators and the incident elastic wave, a low-frequency bandgap can be generated at a subwavelength scale much smaller than the wavelength, overcoming the size limitations of Bragg scattering and achieving low-frequency vibration modulation through "small structure controlling large wavelength." Simultaneously, by introducing line defects into perfectly periodic phonon crystals, defect states can be induced within the bandgap range, ensuring that elastic waves propagate only along the defect path. This enables directional transmission and precise control of the propagation path of elastic waves, laying the foundation for the design of acoustic waveguide devices.

[0004] Although existing technologies have improved the low-frequency vibration isolation performance of lattice sandwich structures by introducing localized oscillators, key issues remain, such as narrow low-frequency bandgap width and difficulty in simultaneously achieving directional transmission of elastic waves. Therefore, developing a novel locally resonant lattice sandwich phonon crystal that can simultaneously achieve lightweight, wide-bandwidth low-frequency bending wave bandgap, and low-loss directional waveguide functionality has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] To address the problems existing in the background technology, this invention provides a local resonant lattice sandwich metamaterial structure, which solves the technical problems of narrow bandgap width and difficulty in simultaneously achieving low-frequency vibration reduction and elastic wave directional transmission in existing local resonant lattice sandwich structures. While maintaining the lightweight advantage of the lattice structure, it obtains a wideband low-frequency bending wave bandgap and achieves low-loss and high-robust bending wave directional waveguide function within the bandgap range.

[0006] The technical solution adopted by the present invention to solve its technical problem is: a local resonant lattice sandwich metamaterial structure, including an upper panel and a lower panel arranged in parallel with each other, and a pyramid lattice core layer disposed between the two panels. The pyramid lattice core layer is rigidly connected to both the upper panel and the lower panel. The pyramid lattice core layer is a two-dimensional periodic double-layer pyramid lattice structure, including a sandwich phonon crystal disposed at each node. The sandwich phonon crystal is differentiated into a first structural variant and a second structural variant with complementary properties. The two structural variants can be used alone or in combination.

[0007] The local resonant lattice sandwich metamaterial structure uses a mixture of two structural variants to form a heterogeneous linear defect waveguide structure, which allows the flexural wave to propagate directionally within the bandgap range. The defect orientation of the heterogeneous linear defect waveguide structure can be linear, L-shaped, or curved.

[0008] Each sandwich phonon crystal includes a local oscillator, multiple support rods, and a middle panel parallel to the two panels. The local oscillator is rigidly connected and integrated on the middle panel. The multiple support rods are divided into two groups and rigidly mounted on the upper and lower panels of the middle panel respectively. The two groups of support rods are rigidly connected to the upper and lower panels respectively.

[0009] In the first structural variant, the local oscillator is directly and rigidly connected to the solid central panel, forming a flexural bandgap in the mid-to-low frequency range. In the second structural variant, the local oscillator is rigidly connected to the central panel through a helical elastic connecting beam, forming a flexural bandgap in the ultra-low frequency range.

[0010] Both sets of support rods are arranged in a pyramid shape. The tip of one set of support rods located between the upper panel and the middle panel is set towards the upper panel, and the tip of the other set of support rods located between the lower panel and the middle panel is set towards the lower panel.

[0011] The Z-direction stiffness difference of the local resonant lattice sandwich metamaterial structure with the two structural variants arranged in a mixed configuration is less than 10%.

[0012] The sandwich phononic crystal can form a flexural bandgap in the 50-200Hz frequency band, and the average attenuation of the flexural wave in the bandgap is greater than 40dB.

[0013] The local oscillator is made of steel, and the material parameters of the steel are: density 7720-8100 kg / m³, Young's modulus 190-210 GPa, and Poisson's ratio 0.27-0.30. The upper panel, lower panel, center panel, and support rod are all made of epoxy resin material. The material parameters of epoxy resin material are: density 1100-1200 kg / m³, Young's modulus 2.0-4.5 GPa, and Poisson's ratio 0.35-0.42.

[0014] The beneficial effects of this invention are: 1. This material achieves highly efficient suppression of ultra-wideband low-frequency bending waves. This invention utilizes two differentiated oscillator configurations—rigidly fixed and elastically connected via a helical beam—to achieve bending wave attenuation greater than 40dB within the 423Hz-1200Hz and 65Hz-126Hz bandgap ranges, respectively.

[0015] 2. This material has a simple structure and strong process compatibility, making it suitable for direct engineering applications. This invention uses only two different materials and can be mass-produced using existing processes such as 3D printing and molding. It can be made into regularly shaped flat plate structures that can directly replace existing engineering structures such as aerospace cabins, rail transit car floors, and building floors, without requiring significant modifications to the original systems.

[0016] 3. The two configurations of the modified material exhibit good stiffness matching, achieving a balance between high stiffness uniformity and low-loss directional waveguide. The two oscillator connection configurations of this invention have minimal stiffness difference in the Z direction, and when mixed and arranged, they can form a finite-periodic plate structure with uniform overall stiffness. Simultaneously, by replacing one configuration with the other to form a heterogeneous line defect structure, low-loss and highly robust directional transmission of bending waves can be achieved over a wide bandwidth without removing any structural components. This solves the technical challenge of existing technologies in simultaneously meeting the triple requirements of "structural load-bearing capacity, wideband vibration reduction, and directional transmission." Attached Figure Description

[0017] In the attached diagram: Figure 1 This is a schematic diagram of the first structural variant of the present invention (oscillator rigid connection variant); Figure 2 This is a schematic diagram of the second structural variant of the present invention (elastic connection variant of oscillator helical beam); Figure 3 Figure (a) shows the flexural wave bandgap curve of the first structural variant; Figure 3 Figure (b) shows the frequency response function curve of the first structural variant; Figure 4 Figure (a) shows the flexural wave bandgap curve of the second structural variant; Figure 4 Figure (b) shows the frequency response function curve of the second structural variant; Figure 5 This is a comparison curve of stress-strain in the Z direction between the first and second structural variants of the present invention; Figure 6 This is a schematic diagram of the linear curved waveguide structure with line defects of the present invention; Figure 7 This is a schematic diagram of the L-shaped bent waveguide structure with line defects of the present invention; Figure 8 Figure (a) shows a comparison between the simulation results and experimental results of the frequency response curves of the first structural variant; Figure 8 Figure (b) shows a comparison between the simulation and experimental results of the frequency response curves of the second structural variant; In the diagram: 1. Top panel; 2. Support rod; 3. Middle panel; 4. Local oscillator; 5. Bottom panel; 6. Elastic connecting beam. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings. The drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0019] A localized resonant lattice sandwich metamaterial structure includes an upper panel 1 and a lower panel 5 arranged parallel to each other, and a pyramid lattice core layer disposed between the two panels. The pyramid lattice core layer is rigidly connected to both the upper panel 1 and the lower panel 5. The pyramid lattice core layer is a two-dimensional periodic double-layer pyramid lattice structure, including a sandwich phonon crystal disposed at each node. The sandwich phonon crystal is differentiated into a first structural variant and a second structural variant with complementary properties. The two structural variants can generate bending wave bandgap in different frequency bands. The two structural variants can be used alone or in combination. The combination of the two structural variants can obtain a wideband low-frequency bending wave bandgap through the bandgap misalignment effect, which greatly broadens the frequency range and width of the overall bending wave bandgap.

[0020] The local resonant lattice sandwich metamaterial structure uses two structural variants mixed and arranged to form a heterogeneous line defect waveguide structure, which allows the flexural wave to propagate directionally within the bandgap range. The heterogeneous line defect waveguide structure is formed by replacing one structural variant with another on a specific path. The defect of the heterogeneous line defect waveguide structure can be straight, L-shaped, or curved, and the curved type can adopt any curve direction.

[0021] Each sandwich phonon crystal includes a local oscillator 4, multiple support rods 2, and a middle panel 3 parallel to the two panels. The local oscillator 4 is rigidly connected and integrated on the middle panel 3. The multiple support rods 2 are divided into two groups and rigidly set on the upper and lower surfaces of the middle panel 3 respectively. The two groups of support rods 2 are rigidly connected to the upper panel 1 and the lower panel 5 respectively.

[0022] In the first structural variant, the local oscillator 4 is directly and rigidly connected to the solid central panel 3. The local oscillator 4 generates bending vibration coupling with the upper panel 1, the lower panel 5 and the central panel 3, forming a bending wave bandgap in the mid-to-low frequency range. In the second structural variant, the local oscillator 4 is rigidly connected to the central panel 3 through an elastic connecting beam 6. Under the connection method of the second structural variant, the local oscillator 4 generates a torsional-translational coupled vibration mode, forming a bending wave bandgap in the ultra-low frequency range.

[0023] Both sets of support rods 2 are arranged in a pyramid shape. The tip of one set of support rods 2 located between the upper panel 1 and the middle panel 3 is set towards the upper panel 1, and the tip of the other set of support rods 2 located between the lower panel 5 and the middle panel 3 is set towards the lower panel 5.

[0024] The elastic connecting beam 6 is spiral-shaped, and a spiral groove is opened around the local oscillator 4 on the central panel 3. The spiral groove penetrates the surface of the central panel 3 to form a spiral elastic connecting beam 6.

[0025] The Z-direction stiffness difference of the local resonant lattice sandwich metamaterial structure with the two structural variants arranged in a mixed configuration is less than 10%.

[0026] The sandwich phononic crystal can form a flexural bandgap in the 50-200Hz frequency band, and the average attenuation of the flexural wave in the bandgap is greater than 40dB.

[0027] The local oscillator 4 is made of steel, and the material parameters of the steel are: density 7720-8100 kg / m³, Young's modulus 190-210 GPa, and Poisson's ratio 0.27-0.30. The upper panel 1, lower panel 5, center panel 5, and support rod 2 are all made of epoxy resin material. The material parameters of epoxy resin material are: density 1100-1200 kg / m³, Young's modulus 2.0-4.5 GPa, and Poisson's ratio 0.35-0.42.

[0028] This local resonant lattice sandwich metamaterial structure can be integrally formed by photopolymerization 3D printing process. The local oscillator 4 is bonded by high-strength adhesive. The manufacturing process is simple, low-cost, and suitable for mass production.

[0029] In this embodiment, the thickness of both the upper panel 1 and the lower panel 5 is 1 mm. Under the first structural variant, the side length of the single-core phonon crystal is 30 mm, the height is 32 mm, the thickness of the middle panel 3 is 2.5 mm, the width is 26 mm, the inclination angle of each support rod 2 is 45°, the radius is 1 mm, the density of the epoxy resin material is 1180 kg / m³, the Young's modulus is 4.35 GPa, and the Poisson's ratio is 0.38; the radius of the local oscillator 4 is 4.4 mm, the height is 9 mm, the density of the steel material is 7850 kg / m³, the Young's modulus is 200 GPa, and the Poisson's ratio is 0.30. Based on the first structural variant, a spiral groove is formed on the central panel 3 to obtain the second structural variant.

[0030] The first structural variant using the above parameters is as follows: Figure 1 As shown, the local oscillator 4 is fixed to the center of the central panel 3 with high-strength glue. Under this connection condition, the local oscillator 4 generates strong bending vibration coupling with the upper panel 1, the lower panel 5 and the central panel 3, forming a bending wave bandgap in the 423-1200Hz frequency band.

[0031] By creating a spiral groove on the center panel 3 of the first structural variant using the above parameters, it becomes the second structural variant, as shown below. Figure 2 As shown, the groove width of the spiral groove is 2 mm. The elastic connecting beam 6 of the second structural variant provides extremely low equivalent stiffness, enabling the local oscillator 4 to generate a torsional-translational coupled vibration mode, forming a lower frequency bending wave bandgap in the 65-126 Hz frequency band.

[0032] like Figure 3 , Figure 4 As shown, the bandgap range of the first structural variant is 423-1200Hz, and the bandgap range of the second structural variant is 65-126Hz, both exhibiting attenuation of more than 40dB within their respective bandgap ranges.

[0033] like Figure 5 As shown, both structural variants have high stiffness in the Z direction, and the stiffness of the second structural variant is only reduced by 10% compared to the first structural variant. When mixed and arranged, they can form a finite periodic plate structure with uniform overall stiffness, without the problem of sudden changes in local stiffness.

[0034] like Figure 6 As shown, this is a straight-line heterolinear defect waveguide structure. Replacing all the first structural variants in the middle row with the second structural variants creates a straight-line heterolinear defect path. Bending waves can only propagate along this defect path. The red areas in the figure represent regions of large displacement, while the blue areas represent regions of small displacement.

[0035] like Figure 7As shown, an L-shaped heteroline defect waveguide structure is formed by replacing the first structural variant unit on a specific path with a second structural variant unit, creating an L-shaped heteroline defect path with a 90° bend. Experimental results show that the L-shaped waveguide exhibits very low transmission loss at the bend in the 485Hz-502.5Hz range and demonstrates good robustness to structural corners.

[0036] like Figure 8 As shown, the bending wave transmission characteristics of the two structural variants were experimentally tested. To eliminate the influence of the deviation between the actual performance of the experimental materials and the theoretical parameters, the measured parameters of the materials used in this experiment were used for simulation calculations, and the results were compared and analyzed with the experimental data. The measured material parameters in this experiment were as follows: the density of the epoxy resin material was 1150 kg / m³, the Young's modulus was 2.2 GPa, and the Poisson's ratio was 0.38; the density of the steel material of the local oscillator 4 was 7930 kg / m³, the Young's modulus was 193 GPa, and the Poisson's ratio was 0.30.

[0037] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A localized resonant lattice sandwich metamaterial structure, characterized in that: It includes an upper panel (1) and a lower panel (5) arranged in parallel to each other, and a pyramid lattice core layer disposed between the two panels. The pyramid lattice core layer is rigidly connected to both the upper panel (1) and the lower panel (5). The pyramid lattice core layer is a two-dimensional periodic double-layer pyramid lattice structure, including a sandwich phononic crystal disposed at each node. The sandwich phononic crystal is differentiated into a first structural variant and a second structural variant with complementary performance. The two structural variants can be used alone or in a mixed arrangement.

2. The locally resonant lattice sandwich metamaterial structure according to claim 1, characterized in that: The local resonant lattice sandwich metamaterial structure uses a mixture of two structural variants to form a heterogeneous linear defect waveguide structure, which allows the flexural wave to propagate directionally within the bandgap range. The defect orientation of the heterogeneous linear defect waveguide structure can be linear, L-shaped, or curved.

3. The locally resonant lattice sandwich metamaterial structure according to claim 2, characterized in that: Each sandwich phonon crystal includes a local oscillator (4), multiple support rods (2) and a middle panel (3) parallel to the two panels. The local oscillator (4) is rigidly connected and integrated on the middle panel (3). The multiple support rods (2) are divided into two groups and rigidly set on the upper and lower surfaces of the middle panel (3). The two groups of support rods (2) are rigidly connected to the upper panel (1) and the lower panel (5) respectively.

4. The locally resonant lattice sandwich metamaterial structure according to claim 3, characterized in that: In the first structural variant, the local oscillator (4) is directly rigidly connected to the solid central panel (3) to form a bending wave bandgap in the mid-to-low frequency band. In the second structural variant, the local oscillator (4) is rigidly connected to the central panel (3) through an elastic connecting beam (6) to form a bending wave bandgap in the ultra-low frequency band.

5. The locally resonant lattice sandwich metamaterial structure according to claim 4, characterized in that: Both sets of support rods (2) are arranged in a pyramid shape. The tip of one set of support rods (2) located between the upper panel (1) and the middle panel (3) is set towards the upper panel (1), and the tip of the other set of support rods (2) located between the lower panel (5) and the middle panel (3) is set towards the lower panel (5).

6. The locally resonant lattice sandwich metamaterial structure according to claim 5, characterized in that: The elastic connecting beam (6) is spiral-shaped.

7. The locally resonant lattice sandwich metamaterial structure according to claim 6, characterized in that: The Z-direction stiffness difference of the local resonant lattice sandwich metamaterial structure with the two structural variants arranged in a mixed configuration is less than 10%.

8. The locally resonant lattice sandwich metamaterial structure according to claim 7, characterized in that: The sandwich phononic crystal can form a flexural bandgap in the 50-200Hz frequency band, and the average attenuation of the flexural wave in the bandgap is greater than 40dB.

9. The locally resonant lattice sandwich metamaterial structure according to claim 8, characterized in that: The local oscillator (4) is made of steel. The material parameters of the steel are: density 7720-8100 kg / m³, Young's modulus 190-210 GPa, and Poisson's ratio 0.27-0.

30. The upper panel (1), lower panel (5), center panel (5) and support rod (2) are all made of epoxy resin. The material parameters of the epoxy resin are: density 1100-1200 kg / m³, Young's modulus 2.0-4.5 GPa, and Poisson's ratio 0.35-0.42.

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