Sandwich structure with sound absorption and load bearing functions and method of manufacturing same

Abstract

This invention relates to the field of sound-absorbing load-bearing structure technology, providing a sandwich structure with sound absorption and load-bearing functions and its manufacturing method. The sandwich structure includes a micro-perforated plate, a perforated, bent, and folded core, and a base plate. The perforated, bent, and folded core is sandwiched between the micro-perforated plate and the base plate. After the perforated, bent, and folded core is connected to the micro-perforated plate and the base plate, it naturally forms multiple upright curved trapezoidal cavities and multiple inverted curved trapezoidal cavities. In a first direction, the upright and inverted curved trapezoidal cavities are arranged alternately. In a second direction, both the upright and inverted curved trapezoidal cavities are wavy. The first direction is perpendicular to the second direction. This invention has a simple overall structure, high specific strength, and is easy to manufacture, while possessing both low-frequency sound absorption and high load-bearing capacity.

Description

Technical Field

[0001] This invention relates to the field of sound-absorbing load-bearing structure technology, specifically to a sandwich structure with sound-absorbing and load-bearing functions and its manufacturing method. Background Technology

[0002] Noise refers to sounds that affect people's work and life. It is a subjective feeling, so any sound that people do not need or want to hear under certain circumstances can be called "noise." Noise poses a great threat to people's health, work, life, as well as to equipment, instruments, and buildings.

[0003] Low-to-mid frequency (100-1000Hz) noise is extremely annoying and very common in daily life. Micro-perforated sound-absorbing structures are often used in the field of noise control in air. Micro-perforated plate sound-absorbing structures have been applied in engineering practice. Micro-perforated plates are mainly made by creating multiple micro-perforations in a thin plate, forming a sound-absorbing structure with the back cavity. The sound absorption effect is achieved by utilizing the viscous loss effect of the air medium in the micro-perforations. However, the application of micro-perforated plates is limited by factors such as their single function and uncontrollable height. There is an urgent need to design a new structure to solve the above-mentioned defects. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the purpose of this invention is to provide a sandwich structure with sound absorption and load-bearing functions and its manufacturing method.

[0005] According to the present invention, a sandwich structure with sound absorption and load-bearing functions includes a micro-perforated plate, a perforated bending folded core, and a base plate;

[0006] The perforated, bent, and folded core is sandwiched between the micro-perforated plate and the base plate. After the perforated, bent, and folded core is connected to the micro-perforated plate and the base plate, it naturally forms multiple upright curved trapezoidal cavities and multiple inverted curved trapezoidal cavities.

[0007] In the first direction, upright curved trapezoidal cavities and inverted curved trapezoidal cavities are arranged alternately. In the second direction, both upright curved trapezoidal cavities and inverted curved trapezoidal cavities are wavy. The first direction is perpendicular to the second direction.

[0008] Preferably, the micro-perforated plate, the perforated bending folded core, and the base plate are all made of carbon fiber reinforced composite material.

[0009] Preferably, the upper side of the perforated bending folded core is bonded and fixed to the lower side of the perforated plate, and the lower side of the perforated bending folded core is bonded and fixed to the upper side of the base plate.

[0010] Preferably, the cell comprises multiple cells, with an upright curved trapezoidal cavity and an inverted curved trapezoidal cavity forming one cell.

[0011] Preferably, the micro-perforated plate has a variety of first micro-perforations of different diameters, and a row of second micro-perforations is provided on both sides of the perforated bending fold core. The second micro-perforations are located at the center of the top view of the side of the fold core, and their direction is consistent with the direction of the curved trapezoidal cavity. The first micro-perforations correspond one-to-one with the second micro-perforations on the inverted curved trapezoidal cavity.

[0012] Preferably, the first micro-perforations are divided into multiple rows, the diameter of the first micro-perforations in each row is equal, the spacing between the first micro-perforations in adjacent rows is consistent, and the direction of the first micro-perforations in each row is consistent with the direction of the inverted curved trapezoidal cavity.

[0013] Preferably, the cross-section of the perforated bending crease folded core is an isosceles trapezoid.

[0014] A method for manufacturing a sandwich structure with sound absorption and load-bearing functions according to the present invention includes the following steps:

[0015] S1: Determine the sound absorption frequency range and maximum load-bearing stress of the sandwich structure;

[0016] S2: Select materials according to the sound absorption frequency range and maximum load-bearing stress. Among them, the micro-perforated plate and the base plate are selected as flat and flawless thin plates, and the plate thickness is designed according to the requirements of S1.

[0017] S3: Design the curved crease folded core cell. The geometric parameters of the cell are designed according to the requirements in S1. The cells are arranged in an array to obtain a complete curved crease folded core.

[0018] S4: Manufacturing and processing the perforated, bent, creased, folded core and micro-perforated plate, specifically including the following sub-steps:

[0019] S41: Manufacturing of the perforated, bent, crease-lined folded core: Design and manufacture two molds, upper and lower, according to the geometric parameters designed in S3. Select carbon fiber prepreg, and select the thickness according to the design results of S3. Preheat the carbon fiber prepreg and the mold, and apply a release agent to the mold surface. After preheating, lay the carbon fiber prepreg on the mold surface. After laying, close the two molds and compact them. Move the compacted mold to a hot autoclave for heating, pressurizing, and storing for a certain time until it is completely cured. After curing, cool and demold to obtain a bent, crease-lined folded core with flash. Cut and drill holes in the core layer according to the geometric parameters in S3 to obtain the perforated, bent, crease-lined folded core.

[0020] S42: Manufacturing of micro-perforated panels: Based on the design results of S3, the direction and detailed parameters of the curved trapezoidal cavity are obtained. At the same time, the micro-perforation diameter is obtained from the sound absorption coefficient design process. The reinforced carbon fiber plate with the thickness designed in S3 is used to drill holes using a drilling machine to obtain the micro-perforated panels.

[0021] S43: The perforated bending folded core and micro-perforated plate are obtained from the processes of S41 and S42. Using the base plate with the thickness designed in S3, the micro-perforated plate, the perforated bending folded core and the base plate are aligned with the hole positions and glued together. After curing, a sandwich structure with sound absorption and load-bearing functions is obtained.

[0022] Preferably, the sound absorption coefficient design follows these settings:

[0023] Cellular curved trapezoidal cavity volume V ct The design meets the following requirements:

[0024] V ct =[(w+W)H c / 2]L(1)

[0025] W = w + 2H c / tanβ(2)

[0026] L=(4θ / 360°)×πl(3)

[0027] Where w and W are the lengths of the short and long bases of the trapezoidal cross section, respectively; β is the base angle of the trapezoidal cross section; l and L are the characteristic arc length and length along the bending direction, respectively; and H... c Where θ is the cavity height and θ is the bending angle;

[0028] Cell surface normalized impedance Z s The calculation is as follows:

[0029]

[0030] Z k =Z Mk +Z Ck (5)

[0031]

[0032] Among them, Z s Represents the cell-normalized surface impedance. Z represents the proportion of the incident surface area of ​​a single cavity to the total incident area of ​​the cell. k Z represents the surface acoustic impedance of a single cavity. Ck Z represents the acoustic impedance of the cavity. Mk Z0 represents the acoustic impedance of the micro-perforated plate, j represents the imaginary unit, Z0 represents the characteristic impedance of air, ω represents the angular frequency, and t represents the acoustic impedance of the micro-perforated plate. k p represents the depth of each micropore. k d represents porosity. k The diameter of each micropore is represented, c0 represents the speed of sound in air, and H represents the speed of sound in air. c This indicates the cavity height, and ρ0 represents the air density. This represents the ratio of pore size to the thickness of the viscous layer boundary, where J0 and J1 represent the 0th and 1st order Bessel functions, respectively, and μ = 1.8 × 10⁻⁶. -5 Pa·s represents the kinetic viscosity of air;

[0033] The cell absorption coefficient α is specifically:

[0034]

[0035] Where R represents the reflection coefficient, Z0 represents the air characteristic impedance, and Z s Z0 represents the cell-normalized surface impedance, and Z0 = c0ρ0, where c0 represents the speed of sound in air and ρ0 represents the air density.

[0036] The design of the maximum load-bearing stress of a structure follows the process below:

[0037] The structural buckling strength is:

[0038]

[0039] E s t represents the average tensile modulus. c H represents the thickness of the sandwich panel, l is the characteristic arc length along the bending direction, and H is the thickness of the sandwich panel. c Let μ represent the cavity height, β be the base angle of the trapezoidal section, w be the length of the shorter base of the trapezoidal section, and μ = 1.8 × 10⁻⁶. -5 Pa·s represents the kinetic viscosity of air, and θ is the bending angle;

[0040] The structural failure strength is:

[0041]

[0042] Where, σ f Indicates fracture strength, t c The thickness of the sandwich panel is represented by α, the intermediate integration parameter is represented by β, and the base angle of the trapezoidal section is represented by H. c The cavity height is represented by w, the length of the shorter base of the trapezoidal cross section is w, the bending angle is θ, and the differential sign is dα.

[0043] Preferably, it also includes S5, which is a performance simulation calculation, specifically including the following sub-steps:

[0044] S51: Sound absorption performance calculation: The sound absorption effect of the model is verified by finite element simulation. The pressure acoustics and thermoviscous acoustics modules of COMSOL Multiphsics are used for finite element simulation. The simulation frequency range is set to 0 to 2000 Hz. Periodic boundary conditions are used on both sides of the cell. The corresponding sound wave channel is established based on the shape of the model and plane wave radiation is added. The normal incidence condition of the upper surface is simulated with an amplitude of 1 Pa. No slip and isothermal boundary conditions are applied at the air and structural adjacent areas. Second-order Lagrangian elements are used.

[0045] S52: Load-bearing capacity calculation: Quasi-static compression analysis was performed in Abaqus / Explicit. Periodic boundary conditions were used to simulate the folded core with bending creases and infinite unit cells. The two-dimensional Hashin criterion based on energy damage evolution was used to simulate the failure mode of the structure. The periodic boundary conditions satisfy the following relationship:

[0046]

[0047] in, This represents the displacement components of a pair of opposite edges in the i-direction. Represents the angular component of a pair of opposite edges about the i-th direction;

[0048] The finite element model of the composite laminate is divided into quadrilateral shell elements S4R mesh. The influence of the perforations on the folded core due to bending creases on the strength of the core layer is ignored. The frictional force between the core layer and the bottom plate is defined by a penalty function to limit the rigid body movement of the core layer. The bottom rigid plate is fixed, and the rigid plate above the core layer moves downward at a speed of 1 mm / s to simulate the quasi-static compression of the structure.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] 1. This invention utilizes a perforated, bent, and folded core, a micro-perforated plate, and a base plate to form a resonant load-bearing structure, thereby obtaining a composite functional structure with good mid-to-low frequency noise absorption and high load-bearing capacity. The overall structure is simple, has high specific strength, is easy to manufacture, and simultaneously possesses low-frequency sound absorption and high load-bearing capacity.

[0051] 2. The sandwich structure obtained by combining a perforated, bent, folded core material made of carbon fiber reinforced composite material and a micro-perforated plate has high load-bearing capacity and excellent mid-to-low frequency sound absorption performance. Attached Figure Description

[0052] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0053] Figure 1This is a schematic diagram of the sandwich structure from one perspective.

[0054] Figure 2 This is a schematic diagram of the sandwich structure from another perspective.

[0055] Figure 3 This is a detailed geometric parameter diagram of the present invention;

[0056] Figure 4 This is a schematic diagram of the manufacturing process of the perforated, bent, creased, and folded core of the present invention;

[0057] Figure 5 This is a schematic diagram of the bonding process of the micro-perforated plate, the perforated bending folded core, and the base plate of the present invention;

[0058] Figure 6 The finite element mesh for simulating the sound absorption coefficient of the structure in this invention;

[0059] Figure 7 This invention provides a finite element mesh for uniaxial compression simulation of the computational structure.

[0060] Figure 8 This is the sound absorption coefficient-frequency curve of the present invention under certain parameters;

[0061] Figure 9 This is the stress-strain history curve of the present invention under uniaxial compression under certain parameters.

[0062] The diagram shows:

[0063] Microperforated plate 1

[0064] Perforated, bent, creased, folded core 2

[0065] Base plate 3

[0066] First micro-perforation 4

[0067] Inverted curved trapezoidal cavity 5

[0068] Upright curved trapezoidal cavity 6

[0069] Second microperforation 7 Detailed Implementation

[0070] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0071] This invention provides a sandwich structure with sound absorption and load-bearing functions, including a micro-perforated plate 1, a base plate 3, and a perforated, bent, and folded core 2 sandwiched between the micro-perforated plate 1 and the base plate 3. After the perforated, bent, and folded core 2 is connected to the micro-perforated plate 1 and the base plate 3, it naturally forms multiple upright curved trapezoidal cavities 6 and multiple inverted curved trapezoidal cavities 5. Preferably, the upper side of the perforated, bent, and folded core 2 is bonded and fixed to the lower side of the perforated plate, and the lower side of the perforated, bent, and folded core 2 is bonded and fixed to the upper side of the base plate 3.

[0072] In the first direction, upright curved trapezoidal cavities 6 and inverted curved trapezoidal cavities 5 are arranged alternately. In the second direction, both upright curved trapezoidal cavities 6 and inverted curved trapezoidal cavities 5 are wavy. The first direction is perpendicular to the second direction. The micro-perforated plate 1, the perforated bending folded core 2, and the base plate 3 are all made of carbon fiber reinforced composite material. This invention is simple to manufacture, highly designable, has high specific strength, and simultaneously possesses low-frequency sound absorption capability and high load-bearing capacity.

[0073] Specifically, an upright curved trapezoidal cavity 6 and an inverted curved trapezoidal cavity 5 form a cell, and the sandwich structure includes multiple cells.

[0074] The micro-perforated plate 1 has a variety of first micro-perforations 4 with different diameters. The first micro-perforations 4 correspond to the upright curved trapezoidal cavity 6 and the inverted curved trapezoidal cavity 5.

[0075] The perforated, curved, and creased folded core 2 has a row of second micro-perforations 7 on both sides. The second micro-perforations 7 are located at the center of the top view of the side of the folded core, and their orientation is consistent with the orientation of the curved trapezoidal cavity. The diameter d of the second micro-perforation 7 is... c It can be modified; the first micro-perforation 4 and the second micro-perforation 7 on the inverted curved trapezoidal cavity 5 correspond one-to-one. The first micro-perforation 4 and the second micro-perforation 7 are preferably made by laser drilling.

[0076] The first micro-perforation 4 is divided into multiple rows. The diameter of the first micro-perforation 4 in each row is equal. The spacing between the first micro-perforations 4 in adjacent rows is consistent. The direction of the first micro-perforation 4 in each row is consistent with the direction of the inverted curved trapezoidal cavity 5. The first micro-perforation 4 corresponding to each two adjacent inverted curved trapezoidal cavities 5 is a group. The diameters d1, d2, d3, and d4 of the first micro-perforation 4 in each group can be changed by themselves.

[0077] The cross-section of the perforated, bent, and folded core 2 is an isosceles trapezoid. The width w of the upper base, the size β of the base angle, and the height H of the trapezoid are also considered. c You can change it yourself, such as Figure 3 As shown, the bending path of the perforated bending fold core 2 consists of four centrally symmetrical arcs with a central angle of θ. The arc diameter D0 can be modified according to requirements. The thickness t of the micro-perforated plate 1 is... M, Perforation, bending, crease, folded core, 2 t thickness c , base plate thickness 3t B The design can be modified according to requirements;

[0078] by Figures 3 to 5 The structural parameters shown illustrate the design and fabrication method of a sandwich structure integrating sound absorption and load-bearing functions with a perforated, bent, folded core. Figures 6 to 9 The structural simulation verification process, sound absorption performance, and load-bearing performance are explained. The design, manufacturing, and verification process mainly includes the following steps:

[0079] S1: Define design requirements: For sound-absorbing load-bearing structures, the working environment and requirements of the sandwich structure should be defined first, such as the sound absorption frequency range and maximum load-bearing stress.

[0080] S2: Composite Material Selection: The high strength of T300 carbon fiber can greatly improve the structural strength, while its good machinability allows for easy drilling.

[0081] S3: Structural Design: The herringbone folded core inspired by soybean leaves is bent with creases to obtain a bent crease folded core cell. The geometric parameters of the cell are designed according to the requirements of S1. Then, the cells are arrayed to obtain a complete bent crease folded core. Furthermore, the micro-perforated plate 1 and the base plate 3 are flat, flawless thin plates, and their thickness is designed according to the requirements of S1. The sound absorption coefficient design process follows these steps:

[0082] Cellular curved trapezoidal cavity volume design:

[0083] V ct =[(w+W)H c / 2]L(1)

[0084] W = w + 2H c / tanβ(2)

[0085] L=(4θ / 360°)×πl(3)

[0086] In the formula, w and W are the lengths of the short and long bases of the trapezoidal cross section, respectively; β is the base angle of the trapezoidal cross section; l and L are the characteristic arc length and length along the bending direction, respectively; and H... c Where θ is the cavity height and θ is the bending angle;

[0087] Calculation of normalized impedance at cell surface:

[0088]

[0089] Z k =Z Mk +Z Ck (5)

[0090]

[0091] Among them, Z s Represents the cell-normalized surface impedance. Z represents the proportion of the incident surface area of ​​a single cavity to the total incident area of ​​the cell. k Z represents the surface acoustic impedance of a single cavity. Ck Z represents the acoustic impedance of the cavity. Mk Z0 represents the acoustic impedance of the micro-perforated plate, j represents the imaginary unit, Z0 represents the characteristic impedance of air, ω represents the angular frequency, and t represents the acoustic impedance of the micro-perforated plate. k p represents the depth of each micropore. k d represents porosity. k The diameter of each micropore is represented, c0 represents the speed of sound in air, and H represents the speed of sound in air. c This indicates the cavity height, and ρ0 represents the air density. This represents the ratio of pore size to the thickness of the viscous layer boundary, where J0 and J1 represent the 0th and 1st order Bessel functions, respectively, and μ = 1.8 × 10⁻⁶. -5 Pa·s represents the kinetic viscosity of air;

[0092] Cell absorption coefficient calculation:

[0093]

[0094] Where R represents the reflection coefficient, Z0 represents the air characteristic impedance, and Z s Z0 represents the cell-normalized surface impedance, and Z0 = c0ρ0, where c0 represents the speed of sound in air and ρ0 represents the air density.

[0095] The design of the maximum load-bearing stress of a structure follows the process below:

[0096] Structural buckling strength design:

[0097]

[0098] E s t represents the average tensile modulus. c H represents the thickness of the sandwich panel, l is the characteristic arc length along the bending direction, and H is the thickness of the sandwich panel. c Let μ represent the cavity height, β be the base angle of the trapezoidal section, w be the length of the shorter base of the trapezoidal section, and μ = 1.8 × 10⁻⁶. -5 Pa·s represents the kinetic viscosity of air, and θ is the bending angle;

[0099] Structural failure strength design:

[0100]

[0101] Where, σ f Indicates fracture strength, t cThe thickness of the sandwich panel is represented by α, the intermediate integration parameter is represented by β, and the base angle of the trapezoidal section is represented by H. c The height of the cavity is represented by w, the length of the shorter base of the trapezoidal cross section is w, the bending angle is θ, and da is represented by the differential symbol.

[0102] S4: Manufacturing and Processing Figures 4 to 5 The manufacturing process of the perforated, bent, creased folded core and the micro-perforated plate is demonstrated. The specific manufacturing steps are as follows:

[0103] S41: Manufacturing of Perforated Bending Crease Folded Core: First, design and manufacture two molds, upper and lower, according to the geometric parameters designed in S3. Select carbon fiber prepreg from S2, with the thickness selected based on the design results of S3. Preheat the prepreg and molds, and apply a release agent to the mold surface. After preheating, lay the prepreg on the mold surface. After laying, close the two molds and compact them. Transfer the compacted mold to an autoclave for heating, pressurizing, and storage for a certain time until complete curing. After curing, cool and demold to obtain a bending crease folded core with flash. Cut and drill the core layer according to the parameters of S3 to obtain perforated bending crease folded core 2, as shown. Figure 4 As shown.

[0104] S42: Micro-perforated panel manufacturing: Based on the design results of S3, the curved trapezoidal cavity orientation and detailed parameters are obtained. Simultaneously, the micro-perforation diameter is obtained from the sound absorption coefficient design process. Using a reinforced carbon fiber plate of the thickness designed in S3, holes are drilled to obtain the micro-perforated panel. For example... Figure 5 As shown;

[0105] S43: Gluing: The perforated, bent, folded core 2 and the micro-perforated plate 1 are obtained from processes S41 and S42. Using a base plate 3 of the designed thickness in S3, the micro-perforated plate 1, the perforated, bent, folded core 2, and the base plate 3 are aligned according to the hole positions and glued together. After curing for a certain period, a sandwich structure with sound absorption and load-bearing functions is obtained, such as... Figure 5 As shown.

[0106] S5: Performance Simulation and Calculation

[0107] S51: Sound Absorption Performance Calculation: The sound absorption effect of the model was verified through finite element simulation. Finite element simulation was performed using the pressure acoustics and thermoviscous acoustics modules of COMSOL Multiphsics. Considering that the purpose of this study is the design of a mid-to-low frequency sound-absorbing structure, the simulation frequency range was set to 0–2000 Hz. Since the air domains between cells are interconnected, periodic boundary conditions were used on both sides of the cell. Based on the model shape, corresponding sound wave channels were established and plane wave radiation was added to simulate the normal incidence condition on the upper surface, with an amplitude of 1 Pa. No-slip, isothermal boundary conditions were applied at the air and structural junctions, using second-order Lagrangian elements, such as... Figure 6 As shown;

[0108] S52: Load-bearing capacity calculation: Quasi-static compression analysis was performed in Abaqus / Explicit. Periodic boundary conditions were used to simulate the folded core with bending creases and infinite unit cells, and the two-dimensional Hashin criterion based on energy damage evolution was used to simulate the failure mode of the structure. The periodic boundary conditions satisfy the following relationship:

[0109]

[0110] in, This represents the displacement components of a pair of opposite edges in the i-direction. This represents the angular component of a pair of opposite edges about the i-th direction.

[0111] The finite element model of the composite laminate is meshed using quadrilateral shell elements (S4R). The influence of bending creases and perforations on the core layer's strength is ignored. A penalty function is used to define the frictional force between the core layer and the bottom plate to restrict the rigid body movement of the core layer. The bottom rigid plate is fixed, while the rigid plate above the core layer moves downwards at a speed of 1 mm / s to simulate quasi-static compression of the structure. Figure 7 As shown.

[0112] like Figure 8 As shown in the figure, the sound absorption design results under certain parameters are in high agreement with the simulation results. Furthermore, the figure shows that the sound absorption coefficients of the sandwich structure under these parameters reach 0.959 and 0.992 at frequencies of 620Hz and 880Hz, respectively, almost achieving near-perfect absorption. If the frequency at which the sound absorption coefficient is greater than 0.7 is defined as the effective sound absorption frequency, then the effective sound absorption bandwidths of the sandwich structure near 620Hz and 880Hz are 140Hz and 240Hz, respectively. Excellent mid-to-low frequency sound absorption performance is demonstrated.

[0113] like Figure 9 As shown, under certain parameters, the maximum compressive stress of the core layer under uniaxial compression is 19.85 MPa, and the buckling stress is 16.46 MPa. The design maximum compressive stress is 17.09 MPa, and the buckling stress is 15.95 MPa. The structural failure mode is buckling failure, and the failure stress error is 3.1%, indicating high design fidelity. Furthermore, the cell mass of the sandwich structure under these parameters is measured to be only 0.489 g, and the specific strength of the sandwich structure under these parameters is calculated to be 33.66 MPa / g. It exhibits strong load-bearing capacity and lightweight potential.

[0114] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0115] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A sandwich structure with sound absorption and load-bearing functions, characterized in that, It includes a micro-perforated plate (1), a perforated bending folded core (2), and a base plate (3); The perforated bending fold core (2) is sandwiched between the micro-perforated plate (1) and the base plate (3). After the perforated bending fold core (2) is connected to the micro-perforated plate (1) and the base plate (3), it naturally forms multiple upright curved trapezoidal cavities (6) and multiple inverted curved trapezoidal cavities (5). In the first direction, the upright curved trapezoidal cavity (6) and the inverted curved trapezoidal cavity (5) are arranged at intervals. In the second direction, both the upright curved trapezoidal cavity (6) and the inverted curved trapezoidal cavity (5) are wavy. The first direction is perpendicular to the second direction.

2. The sandwich structure with sound absorption and load-bearing functions according to claim 1, characterized in that, The micro-perforated plate (1), the perforated bending folded core (2), and the base plate (3) are all made of carbon fiber reinforced composite material.

3. The sandwich structure with sound absorption and load-bearing functions according to claim 1, characterized in that, The upper side of the perforated bending fold core (2) is bonded and fixed to the lower side of the perforated plate, and the lower side of the perforated bending fold core (2) is bonded and fixed to the upper side of the base plate (3).

4. The sandwich structure with sound absorption and load-bearing functions according to claim 1, characterized in that, A cell comprises multiple cells, including an upright curved trapezoidal cavity (6) and an inverted curved trapezoidal cavity (5) forming one cell.

5. The sandwich structure with sound absorption and load-bearing functions according to claim 1, characterized in that, The micro-perforated plate (1) has a variety of first micro-perforations (4) of different diameters. The perforated curved fold core (2) has a row of second micro-perforations (7) on both sides. The second micro-perforations (7) are located at the center of the top view of the side of the fold core and their direction is consistent with the direction of the curved trapezoidal cavity. The first micro-perforations (4) correspond one-to-one with the second micro-perforations (7) on the inverted curved trapezoidal cavity (5).

6. The sandwich structure with sound absorption and load-bearing functions according to claim 1, characterized in that, The first micro-perforation (4) is divided into multiple rows. The diameter of the first micro-perforation (4) in each row is equal. The spacing between the first micro-perforations (4) in adjacent rows is consistent. The direction of the first micro-perforation (4) in each row is consistent with the direction of the inverted curved trapezoidal cavity (5).

7. The sandwich structure with sound absorption and load-bearing functions according to claim 1, characterized in that, The cross section of the perforated bending folded core (2) is an isosceles trapezoid.

8. A method for manufacturing a sandwich structure with sound absorption and load-bearing functions, characterized in that, Includes the following steps: S1: Determine the sound absorption frequency range and maximum load-bearing stress of the sandwich structure; S2: Select materials according to the sound absorption frequency range and maximum load-bearing stress. Among them, the micro-perforated plate (1) and the base plate (3) are selected as flat and flawless thin plates, and the plate thickness is designed according to the requirements of S1. S3: Design the curved crease folded core cell. The geometric parameters of the cell are designed according to the requirements in S1. The cells are arranged in an array to obtain a complete curved crease folded core. S4: Manufacturing and processing the perforated, bent, creased, folded core and micro-perforated plate, specifically including the following sub-steps: S41: Manufacturing of perforated bending folded core: Design and manufacture two molds according to the geometric parameters designed in S3. Select carbon fiber prepreg and select the thickness according to the design results of S3. Preheat the carbon fiber prepreg and the mold and apply a release agent to the mold surface. After preheating, lay the carbon fiber prepreg on the mold surface. After laying, close the two molds and press them. Move the pressed mold to the autoclave for heating, pressurizing and storing for a certain time until it is completely cured. After curing, cool and demold to obtain a bending folded core with flash. Cut and drill the core layer according to the geometric parameters in S3 to obtain the perforated bending folded core (2). S42: Manufacturing of micro-perforated plate: Based on the design results of S3, the direction and detailed parameters of the curved trapezoidal cavity are obtained. At the same time, the micro-perforation diameter is obtained from the sound absorption coefficient design process. The reinforced carbon fiber plate with the thickness designed in S3 is used to drill holes using a drilling machine to obtain the micro-perforated plate (1). S43: The perforated bending folded core (2) and the micro-perforated plate (1) are obtained from the processes of S41 and S42. The base plate (3) with the thickness designed in S3 is used. The micro-perforated plate (1), the perforated bending folded core (2) and the base plate (3) are aligned with the hole positions and glued together. After curing, a sandwich structure with sound absorption and load-bearing functions is obtained.

9. The method for manufacturing a sandwich structure with sound absorption and load-bearing functions according to claim 8, characterized in that, The sound absorption coefficient design should follow these settings: Cellular curved trapezoidal cavity volume V ct The design meets the following requirements: V ct =[(w+W)H c / 2]L(1) W=w+2H c / tanβ(2) L=(4θ / 360°)×πl(3) Where w and W are the lengths of the short and long bases of the trapezoidal cross section, respectively; β is the base angle of the trapezoidal cross section; l and L are the characteristic arc length and length along the bending direction, respectively; and H... c Where θ is the cavity height and θ is the bending angle; Cell surface normalized impedance Z s The calculation is as follows: WITH k =Z Mk +Z Ck (5) Among them, Z s Represents the cell-normalized surface impedance. Z represents the proportion of the incident surface area of ​​a single cavity to the total incident area of ​​the cell. k Z represents the surface acoustic impedance of a single cavity. Ck Z represents the acoustic impedance of the cavity. Mk Z0 represents the acoustic impedance of the micro-perforated plate, j represents the imaginary unit, Z0 represents the characteristic impedance of air, ω represents the angular frequency, and t represents the acoustic impedance of the micro-perforated plate. k p represents the depth of each micropore. k d represents porosity. k The diameter of each micropore is represented, c0 represents the speed of sound in air, and H represents the speed of sound in air. c This indicates the cavity height, and ρ0 represents the air density. This represents the ratio of pore size to the thickness of the viscous layer boundary, where J0 and J1 represent the 0th and 1st order Bessel functions, respectively, and μ = 1.8 × 10⁻⁶. -5 Pa·s represents the kinetic viscosity of air; The cell absorption coefficient α is specifically: Where R represents the reflection coefficient, Z0 represents the air characteristic impedance, and Z s Z0 represents the cell-normalized surface impedance, and Z0 = c0ρ0, where c0 represents the speed of sound in air and ρ0 represents the air density. The design of the maximum load-bearing stress of a structure follows the process below: The structural buckling strength is: E s t represents the average tensile modulus. c H represents the thickness of the sandwich panel, l is the characteristic arc length along the bending direction, and H is the thickness of the sandwich panel. c Let μ represent the cavity height, β be the base angle of the trapezoidal section, w be the length of the shorter base of the trapezoidal section, and μ = 1.8 × 10⁻⁶. -5 Pa·s represents the kinetic viscosity of air, and θ is the bending angle; The structural failure strength is: Where, σ f Indicates fracture strength, t c The thickness of the sandwich panel is represented by α, the intermediate integration parameter is represented by β, and the base angle of the trapezoidal section is represented by H. c The cavity height is represented by w, the length of the shorter base of the trapezoidal cross section is w, the bending angle is θ, and dα is represented by the differential symbol.

10. The method for manufacturing a sandwich structure with sound absorption and load-bearing functions according to claim 8, characterized in that, It also includes S5, which is a performance simulation calculation, specifically including the following sub-steps: S51: Sound absorption performance calculation: The sound absorption effect of the model is verified by finite element simulation. The pressure acoustics and thermoviscous acoustics modules of COMSOL Multiphsics are used for finite element simulation. The simulation frequency range is set to 0 to 2000 Hz. Periodic boundary conditions are used on both sides of the cell. The corresponding sound wave channel is established based on the shape of the model and plane wave radiation is added. The normal incidence condition of the upper surface is simulated with an amplitude of 1 Pa. No slip and isothermal boundary conditions are applied at the air and structural adjacent areas. Second-order Lagrangian elements are used. S52: Load-bearing capacity calculation: Quasi-static compression analysis was performed in Abaqus / Explicit. Periodic boundary conditions were used to simulate the folded core with bending creases and infinite unit cells. The two-dimensional Hashin criterion based on energy damage evolution was used to simulate the failure mode of the structure. The periodic boundary conditions satisfy the following relationship: in, This represents the displacement components of a pair of opposite edges in the i-direction. Represents the angular component of a pair of opposite edges about the i-th direction; The finite element model of the composite laminate is divided into quadrilateral shell elements S4R mesh. The influence of the perforations on the folded core due to bending creases on the strength of the core layer is ignored. The frictional force between the core layer and the bottom plate is defined by a penalty function to limit the rigid body movement of the core layer. The bottom rigid plate is fixed, and the rigid plate above the core layer moves downward at a speed of 1 mm / s to simulate the quasi-static compression of the structure.

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