Underwater sound-absorbing composite superstructure based on double-resonance hybrid enhancement mechanism and preparation method thereof

Abstract

This invention discloses an underwater sound-absorbing composite superstructure based on a dual-resonance hybrid enhancement mechanism and its fabrication method, belonging to the field of underwater sound-absorbing structure design. This invention mixes local resonance and cavity resonance acoustic units as sound-absorbing matrices placed in a sandwich structure. The sandwich structure consists of orthogonal carbon fiber grids and buoyancy material panels, and specific viscoelastic matrix materials are configured for the two acoustic units. This invention significantly enhances sound dissipation performance by utilizing the coupling effect of the two resonance mechanisms, achieving broadband sound absorption. Furthermore, the sandwich structure effectively resists the influence of deep-water hydrostatic pressure, combining excellent sound absorption performance, load-bearing capacity, and lightweight advantages.

Description

Technical Field

[0001] This invention belongs to the field of underwater sound-absorbing structure design, specifically relating to an underwater sound-absorbing composite superstructure based on a dual-resonance hybrid enhancement mechanism and its preparation method. Background Technology

[0002] With the rapid development of underwater acoustic technology, the demand for acoustic stealth performance in submarines, ships, and other underwater and surface vehicles is becoming increasingly urgent, making acoustic structural layers that can effectively absorb underwater sound waves a research hotspot. As underwater operating depths continue to increase, the demand for acoustic stealth performance in underwater platforms and vehicles is rising, thus placing more stringent load-bearing requirements on underwater sound-absorbing materials.

[0003] However, existing sound-absorbing materials often deform or fail under the extreme water pressure of deep-sea environments, resulting in a destructive decline in absorption performance. This makes it difficult to achieve broadband sound absorption while maintaining structural integrity, especially with poor low-frequency absorption. Therefore, there is an urgent need for an underwater sound-absorbing composite superstructure that can adapt to the high-pressure environment of the deep sea, possesses broadband sound absorption performance, and is lightweight. Summary of the Invention

[0004] This invention proposes an underwater sound-absorbing composite superstructure based on a dual-resonance hybrid enhancement mechanism and its preparation method. By utilizing the coupling effect of local resonance and cavity resonance and the load-bearing characteristics of the sandwich structure, broadband sound absorption and structural stability in the deep-sea environment are achieved.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A sound-absorbing superstructure based on a dual-resonance hybrid enhancement mechanism includes a hybrid sound-absorbing matrix and a sandwich structure; the hybrid sound-absorbing matrix is ​​placed in the sandwich structure. The hybrid sound-absorbing matrix is ​​a grid lattice formed by a mixture of local resonant acoustic units and cavity resonant acoustic units, wherein similar acoustic units are placed diagonally in the grid lattice; The sandwich structure is composed of orthogonal carbon fiber grids and buoyancy material panels. The hybrid sound-absorbing matrix is ​​placed inside the orthogonal carbon fiber grids, and the buoyancy material panels are located on the upper and lower sides of the orthogonal carbon fiber grids.

[0006] Both acoustic units and the grille have square cross-sections, with the side length of the acoustic unit's cross-section being half the side length of the grille's cross-section, and the height of the acoustic unit being the same as the height of the grille. By limiting the geometric dimensional relationship between the acoustic unit and the carbon fiber grille, it is ensured that the acoustic unit can be tightly filled inside the grille, avoiding acoustic short circuits or structural strength reduction caused by size mismatch, and ensuring the stability of sound absorption performance.

[0007] The local resonant acoustic unit is formed by embedding a cylindrical metal scatterer into a viscoelastic matrix (the density of the metal scatterer is greater than the density of the surrounding matrix); the cavity resonant acoustic unit is a cone-shaped air cavity reserved in the viscoelastic matrix; the axes of symmetry of the cylindrical metal scatterer and the air cavity in both acoustic units coincide with the axis of symmetry of the viscoelastic matrix.

[0008] The viscoelastic matrix of the local resonant acoustic unit is made of a viscoelastic material with a low Young's modulus and a soft texture; the viscoelastic matrix of the cavity resonant acoustic unit is made of a viscoelastic material with a high Young's modulus and a hard texture. The difference in Young's modulus is the result of comparing the two matrix materials used in this invention. The matrix material with a lower modulus is configured for the local resonant unit in order to obtain a lower local resonant frequency without increasing the weight. It should be noted that the change in modulus will affect the characteristic impedance of the matrix material. Therefore, a comprehensive consideration is needed to select a suitable matrix material for the two types of units.

[0009] The above-mentioned method for fabricating underwater sound-absorbing superstructures based on a dual-resonance hybrid enhancement mechanism includes the following steps: Step 1: According to the design requirements, prepare rectangular carbon fiber strips of the selected size. Use precision machining technology to cut grooves at predetermined positions. The length of the grooves is half the width of the carbon fiber strips, and the width is the same as the thickness of the carbon fiber strips. Use an interlocking process to assemble the grooved carbon fiber strips into an orthogonal grid. Step 2: Establish the corresponding acoustic-structure interaction simulation model in COMSOL multiphysics simulation software. Use the frequency domain study module to obtain the acoustic absorption characteristics of the model at different frequencies. Based on the sound absorption performance requirements, conduct parametric discussions on the geometric parameters of the metal scatterer and the air cavity. Determine the geometric dimensions of the cylindrical metal scatterer inside the local resonance unit and the air cavity inside the cavity resonance unit based on the parametric calculation results. Select the appropriate viscoelastic matrix material for the two acoustic units. Step 3: Based on the determined geometric dimensions, complete the fabrication of the two acoustic units, and then place the two acoustic units in the selected positions inside the grid lattice. Repeat the operation to fill the entire carbon fiber orthogonal grid and complete the fabrication of the sound-absorbing core layer. Step 4: Adhere a buoyancy material panel of a certain thickness to the top and bottom surfaces of the sound-absorbing core layer. After the glue has completely solidified, the underwater sound-absorbing superstructure is completed.

[0010] Beneficial effects: This invention provides a method for fabricating underwater sound-absorbing superstructures based on a dual-resonance hybrid enhancement mechanism, which has the following advantages compared with existing technologies: 1. This invention uses a combination of local resonance and cavity resonance acoustic units as the sound-absorbing matrix. By utilizing the coupling interaction of the two resonance mechanisms, the presence of cavity acoustics significantly enhances the sound dissipation performance of the local resonance unit, enabling the sound-absorbing superstructure to have wide-band sound absorption performance. Furthermore, due to the low-frequency resonance frequency of the metal scatterer, the operating frequency of the sound-absorbing superstructure is effectively extended to the low-frequency range, significantly enhancing the sound dissipation performance and achieving wide-band sound absorption. 2. The sandwich structure composed of orthogonal carbon fiber grid and buoyancy material panel in this invention provides strong support and protection for the sound-absorbing matrix, effectively resisting the adverse effects of deep water hydrostatic pressure on the sound-absorbing matrix, thereby maintaining good absorption effect under high hydrostatic pressure. In addition, the grid is made of carbon fiber material, which can significantly reduce the overall weight of the sound-absorbing structure, and has obvious advantages in lightweight structural design, realizing the integrated design of sound absorption and load-bearing. 3. The present invention has a simple structure and simple preparation steps, which facilitates large-scale production. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the overall sound-absorbing superstructure in an embodiment of the present invention; Figure 2 This is a schematic diagram of a carbon fiber strip with a slot in an embodiment of the present invention; Figure 3 This is a schematic diagram of two local resonant acoustic units in an embodiment of the present invention; Figure 4 This is a schematic diagram of the cavity resonant acoustic unit in an embodiment of the present invention; Figure 5 This document presents the simulation calculations and sound absorption curves under experimental testing conditions for the sound-absorbing superstructure in the embodiments of the present invention. Figure 6 The sound absorption curves of the sound-absorbing superstructure under different hydrostatic pressures are shown in the embodiments of the present invention. In the figure: 1-buoyancy material panel; 2-carbon fiber orthogonal grid; 3-hybrid sound-absorbing matrix; 4-carbon fiber strip with slot; 5-nitrile rubber viscoelastic matrix; 6-metal scatterer in local resonant acoustic unit a; 7-metal scatterer in local resonant acoustic unit b; 8-conical air cavity in cavity resonant acoustic unit; 9-polyurethane viscoelastic matrix. Detailed Implementation

[0012] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings: Example 1

[0013] like Figure 1-4As shown, an underwater sound-absorbing composite superstructure based on a dual-resonance hybrid enhancement mechanism includes: a buoyancy material panel 1 and a carbon fiber orthogonal grid 2; the carbon fiber orthogonal grid 2 is composed of carbon fiber strips 4 with slots; the hybrid sound-absorbing matrix 3 is composed of local resonant acoustic units and cavity resonant acoustic units, and is placed in a sandwich structure composed of orthogonal carbon fiber grid and buoyancy material panel. Local resonant acoustic unit a consists of a nitrile rubber viscoelastic matrix 5 and a metal scatterer 6 within local resonant acoustic unit a; local resonant acoustic unit b consists of a nitrile rubber viscoelastic matrix 5 and a metal scatterer 7 within local resonant acoustic unit b. The cylindrical metal inside local resonant acoustic unit a and local resonant acoustic unit b has different dimensions, which determine different resonant frequencies. The two units can obtain a wider sound absorption bandwidth; the local resonant unit in the hybrid sound-absorbing matrix 3 can be one or both of local resonant acoustic unit a and local resonant acoustic unit b; the cavity resonant acoustic unit consists of a conical air cavity 8 and a polyurethane viscoelastic matrix 9 within the cavity resonant acoustic unit.

[0014] In both acoustic units, the axes of symmetry of the cylindrical metal scatterer and the air cavity coincide with the axis of symmetry of the matrix. The height and width of the matrix are determined by the geometry of the orthogonal grid, while the dimensions of the metal scatterer and the air cavity are closely related to the overall sound absorption performance of the structure; the specific dimensions are determined by simulation calculations. The selection of the two viscoelastic matrices, besides the difference in modulus, also requires that their characteristic impedance be close to that of water, so that sound waves can penetrate more into the matrix. When these two acoustic units are spatially mixed and arranged, complex coupling interactions occur. The presence of cavity resonance significantly enhances the sound energy dissipation efficiency of the surrounding local resonant units, thus breaking the bottleneck of bandwidth limitation of a single resonant unit and achieving effective expansion of the sound absorption frequency band, giving this composite superstructure excellent broadband sound absorption performance.

[0015] Buoyancy material panels 1 are respectively placed on the top and bottom surfaces of the orthogonal carbon fiber grid, forming a closed sandwich space. The orthogonal carbon fiber grid, as the skeleton of the sandwich structure, not only supports and fixes the internal hybrid sound-absorbing matrix, but also significantly reduces the overall weight of the sound-absorbing structure by utilizing the high specific strength of carbon fiber, which is beneficial for lightweight design of underwater equipment. The hybrid sound-absorbing matrix fills the various lattice spaces divided by the orthogonal carbon fiber grid, forming the core layer of the sound-absorbing function. It should be understood that, although... Figure 1 The example shown is an orthogonal grid, but in other embodiments, the specific arrangement of the grid can be adjusted according to the actual load-bearing requirements, as long as it can provide sufficient physical protection for the internal sound-absorbing matrix to prevent structural failure in deep water and high-pressure environments.

[0016] Example 2

[0017] Based on Example 1, this embodiment optimizes the spatial layout and geometric dimensions of the acoustic units within the sandwich structure. Each grid lattice contains two local resonant units and two cavity resonant units, with similar acoustic units placed diagonally.

[0018] Combination Figure 1 , Figure 3 and Figure 4 As shown, the orthogonal carbon fiber grid divides the entire sound-absorbing core layer into several rectangular lattice spaces. Within each lattice space, acoustic units are not randomly filled, but rather follow a specific topological arrangement. In this embodiment, two local resonant acoustic units are located on opposite diagonals of the lattice, while two cavity resonant acoustic units are located on the other diagonal. This "diagonal placement" layout strategy has significant acoustic implications because, in this invention, the hybrid strategy of the two acoustic units does not achieve broadband sound absorption performance through simple linear superposition. Instead, the presence of cavity units significantly enhances the local resonance effect of the metal scatterer, thereby dissipating most of the sound wave energy entering the sound-absorbing matrix to achieve a low-bandwidth sound absorption effect. Therefore, this diagonal placement allows more cavity acoustic units to surround the local resonant acoustic units.

[0019] Furthermore, to ensure that the acoustic unit can perfectly fit the grille space and achieve optimal acoustic performance, this embodiment strictly limits the geometric dimensions. Both the acoustic unit and the grille have square cross-sections, and the side length of the acoustic unit's cross-section is half the side length of the grille's cross-section. The height of the acoustic unit is the same as the height of the grille.

[0020] Example 3

[0021] This embodiment provides a method for fabricating an underwater sound-absorbing composite superstructure based on a dual-resonance hybrid enhancement mechanism. The specific fabrication steps are as follows: 1. According to design requirements, rectangular carbon fiber strips of selected dimensions are prepared. Precision machining techniques are used to cut grooves at predetermined positions, the length of which is half the width of the carbon fiber strip, and the width matching the thickness of the carbon fiber strip. The grooved carbon fiber strips are then assembled into an orthogonal grid using an interlocking process. In this embodiment, carbon fiber strips with dimensions of 200 mm in length, 45 mm in width, and 2 mm in thickness are prepared. These carbon fiber strips are arranged in unidirectional fiber layers, with fiber orientations alternating between 0° and 90°. Subsequently, precision machining techniques are used to machine grooves 22.5 mm in length and 2 mm in width at predetermined positions, thereby obtaining the desired grid. Figure 2 The grooved carbon fiber strips shown are then assembled into a series using an interlocking process. Figure 1 The orthogonal grid structure in the middle; 2. Establish a corresponding acoustic-structure interaction simulation model in COMSOL multiphysics simulation software, and use the frequency domain study module to obtain the sound absorption characteristics of the model at different frequencies. Based on the sound absorption performance requirements, the geometric parameters of the metal scatterer and the air cavity are parametrically discussed. The geometric dimensions of the cylindrical metal scatterer inside the local resonance unit and the air cavity inside the cavity resonance unit are determined based on the parametric calculation results, and the corresponding viscoelastic matrix materials are selected for the two acoustic units. 3. Based on the obtained dimensions, a nitrile rubber strip with grooves is prepared by hot pressing. The size of the groove matches the size of the cylindrical metal scatterer. The scatterer is then embedded into the groove. Two nitrile rubber strips are bonded together with an adhesive to complete the local resonance unit. The unit is then fixed diagonally to the inner wall of the grid. 4. Mix polyurethane component A and component B (curing agent) thoroughly at a mass ratio of 5:2, and inject the mixture into a specially made polytetrafluoroethylene mold. After curing, demold the mixture to obtain a polyurethane sample containing a conical cavity.

[0022] 5. Subsequently, the acoustic core layer is completed through a two-step casting process. First, the mixed, still-uncured polyurethane is cast into the grid surrounding the localized resonant unit, at an angle equal to the distance from the bottom of the conical air cavity to the bottom of the grid. After initial curing, a pre-prepared polyurethane sample containing the cavity is placed inside the grid. Then, the second casting step fills the remaining space within the grid structure, forming the acoustic core layer. Buoyancy material panels are then bonded to the top and bottom surfaces. After the adhesive has completely cured, the fabrication of this example is complete.

[0023] To test the sound absorption characteristics of the sound-absorbing superstructure provided in this invention, a composite superstructure was prepared with the following dimensions: the grid lattice has a side length of 40 mm, a height of 45 mm, and a thickness of 2 mm; the cylindrical scatterer in local resonant acoustic unit a has a diameter of 12 mm, a height of 30 mm, and a distance of 25 mm from its geometric center to the bottom of the substrate; the corresponding dimensions of the scatterer in local resonant acoustic unit b are a diameter of 9 mm, a height of 15 mm, and a distance of 32.5 mm; the upper and lower diameters of the conical air cavity are 3 mm and 13 mm, respectively, with a height of 25 mm and a distance of 22.5 mm from its geometric center to the bottom. Furthermore, regarding material parameters, the substrate material for the local resonant acoustic unit is nitrile rubber with a density of 1400 kg / m³. 3 The Young's modulus is 14 MPa, Poisson's ratio is 0.48, and loss factor is 0.6; the matrix material of the cavity unit is polyurethane elastomer material with a density of 1170 kg / m³. 3 The Young's modulus is 143 MPa, Poisson's ratio is 0.485, and loss factor is 0.6; the metallic scatterer is made of stainless steel with a density of 7850 kg / m³.3 Young's modulus is 205 GPa and Poisson's ratio is 0.28.

[0024] After the component was fabricated as described above, a 118 mm test sample was cut based on the 120 mm internal diameter of the impedance tube. The test sample was placed inside a water-filled impedance tube, and the sound absorption experiment was conducted using the transfer function method, with a test frequency range of 0.8 to 8 kHz. Simulation calculations were performed by constructing a corresponding acoustic-structural coupling model in COMSOL finite element software, and the acoustic characteristics at corresponding frequency points were obtained using the frequency domain study module. For example... Figure 5 As shown, the sound absorption curves obtained from experimental testing under normal pressure and simulation calculations are compared. The comparison results show that the trends of the two are basically consistent, verifying the correctness of the simulation model and related parameter settings. Furthermore, the experimental results show that an absorption coefficient of over 0.8 is achieved in the 1.75-8 kHz range, confirming the low-bandwidth sound absorption performance of the structure of this invention. Subsequently, acoustic tests were conducted on the test specimens under hydrostatic pressures of 0.5, 1.5, 3.0, 4.5, and 6.0 MPa, and the results are as follows. Figure 6 As shown, the absorption shifts to higher frequencies with increasing pressure, resulting in a decrease in low-frequency absorption performance while the absorption performance in the mid-to-high frequency range improves. Although the low-frequency performance of the test sample is somewhat affected, the overall impact of hydrostatic pressure on the sound absorption performance remains limited, indicating that the present invention maintains good acoustic performance even under high hydrostatic pressure. Furthermore, the average density of the entire test sample is only 1264.1 kg / m³. 3 This demonstrates the lightweight advantages brought about by the introduction of carbon fiber grating structure.

[0025] The above are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any equivalent modifications or substitutions made based on the technical concept proposed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A sound-absorbing superstructure based on a dual-resonance hybrid enhancement mechanism, characterized in that, It includes a hybrid sound-absorbing matrix and a sandwich structure; the hybrid sound-absorbing matrix is ​​placed in the sandwich structure; the hybrid sound-absorbing matrix is ​​a grid lattice formed by a mixture of local resonant acoustic units and cavity resonant acoustic units, and the same type of acoustic units in the grid lattice are placed diagonally.

2. The sound-absorbing superstructure based on a dual-resonance hybrid enhancement mechanism as described in claim 1, characterized in that, The sandwich structure consists of an orthogonal carbon fiber grid and a buoyancy material panel, with the buoyancy material panel located on the upper and lower sides of the orthogonal carbon fiber grid; the hybrid sound-absorbing matrix is ​​placed inside the orthogonal carbon fiber grid.

3. The sound-absorbing superstructure based on the dual-resonance hybrid enhancement mechanism as described in claim 2, characterized in that, Both acoustic units and grilles have square cross-sections, with the side length of the acoustic unit's cross-section being half the side length of the grille's cross-section, and the height of the acoustic unit being the same as the height of the grille.

4. The sound-absorbing superstructure based on a dual-resonance hybrid enhancement mechanism according to claim 1 or 3, characterized in that, The local resonant acoustic unit is formed by embedding a cylindrical metal scatterer into a viscoelastic matrix, and the axis of symmetry of the metal scatterer coincides with the axis of symmetry of the viscoelastic matrix.

5. The sound-absorbing superstructure based on the dual-resonance hybrid enhancement mechanism according to claim 4, characterized in that, The cylindrical metals inside the local resonant acoustic units in the hybrid sound-absorbing matrix are selected to be of the same size or two different sizes.

6. The sound-absorbing superstructure based on the dual-resonance hybrid enhancement mechanism according to claim 4, characterized in that, The viscoelastic matrix of the local resonant acoustic unit is made of a viscoelastic material with a low Young's modulus and a soft texture.

7. The sound-absorbing superstructure based on a dual-resonance hybrid enhancement mechanism according to claim 1 or 3, characterized in that, The cavity resonant acoustic unit is a cone-shaped air cavity reserved in a viscoelastic matrix, and the axis of symmetry of the air cavity coincides with the axis of symmetry of the viscoelastic matrix.

8. The sound-absorbing superstructure based on the dual-resonance hybrid enhancement mechanism according to claim 7, characterized in that, The viscoelastic matrix of the cavity resonant acoustic unit is made of a viscoelastic material with high Young's modulus and a relatively hard texture.

9. The method for preparing the sound-absorbing superstructure based on the dual-resonance hybrid enhancement mechanism according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: According to the design requirements, prepare rectangular carbon fiber strips of the selected size. Use precision machining technology to cut grooves at predetermined positions. The length of the grooves is half the width of the carbon fiber strips, and the width is the same as the thickness of the carbon fiber strips. Use an interlocking process to assemble the grooved carbon fiber strips into an orthogonal grid. Step 2: Based on the sound absorption performance requirements, determine the geometric dimensions of the cylindrical metal scatterer inside the local resonance unit and the air cavity inside the cavity resonance unit through finite element simulation calculations, and select the corresponding viscoelastic matrix material for the two acoustic units. Step 3: Based on the determined geometric dimensions, complete the fabrication of the two acoustic units, and then place the two acoustic units in the selected positions inside the grid lattice. Repeat the operation to fill the entire carbon fiber orthogonal grid and complete the fabrication of the sound-absorbing core layer. Step 4: Adhere a buoyancy material panel of a certain thickness to the top and bottom surfaces of the sound-absorbing core layer. After the glue has completely solidified, the underwater sound-absorbing superstructure is completed.

10. The method for preparing the sound-absorbing superstructure based on the dual-resonance hybrid enhancement mechanism according to claim 9, characterized in that, Step two involves the following steps: establishing a corresponding acoustic-structure interaction simulation model in a multiphysics simulation software; using a frequency domain study module to obtain the acoustic absorption characteristics of the model at different frequencies; and, based on the sound absorption performance requirements, parametrically discussing the geometric parameters of the metal scatterer and the air cavity. The geometric dimensions of the cylindrical metal scatterer inside the local resonance unit and the air cavity inside the cavity resonance unit are then determined based on the parametric calculation results. Finally, appropriate viscoelastic matrix materials are selected for the two acoustic units.

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