A method for preparing a broadband high-strength sound-absorbing material by 3D printing assisted freeze casting, product and application

Abstract

The application discloses a kind of 3D printing auxiliary freeze casting preparation wide frequency high-strength sound-absorbing material method, product and application, belong to sound-absorbing material technical field, including the following steps: using 3D printing process, polymer I and polymer II are prepared to obtain Helmholtz resonator, and slurry is dispersed in Helmholtz resonator by freeze casting process to realize dispersion orientation, and wide frequency high-strength sound-absorbing material is prepared.The application utilizes 3D printing to manufacture specific structure shape on demand, to a certain extent, the sound-absorbing performance and mechanical properties of sound-absorbing material are realized;Combined with the directional orientation of freeze casting technology, effective sound absorption in wide frequency range is realized, and the sound-absorbing performance of sound-absorbing material is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of sound-absorbing materials technology, and particularly relates to a method, product and application of preparing broadband high-strength sound-absorbing materials by 3D printing-assisted cryogenic casting. Background Technology

[0002] With the development of industrial manufacturing and national defense equipment, the demand for new materials is increasing. Especially in the field of sound-absorbing materials, high-efficiency, lightweight, and environmentally friendly materials have become a research hotspot. Sound-absorbing materials prepared by traditional methods have certain limitations in structure and performance, making it difficult to meet the needs of certain specific applications. For example, CN202310947272.1 discloses a porous sound-absorbing, heat-insulating, pressure-resistant, and flame-retardant bamboo cellulose aerogel composite material and its preparation method. This material includes a substrate layer and aerogel fire-retardant particles disposed within the substrate layer. The substrate layer is made by crushing bamboo pulp, treating it with an alkaline system, dissolving it under low-temperature conditions, stirring it evenly, cross-linking it with a cross-linking agent to form a hydrogel, and finally obtaining the bamboo cellulose aerogel through directional freeze-drying with dry ice / acetone. However, its preparation process requires the use of alkaline systems and cross-linking agents, which may have a certain impact on the environment, raising concerns about environmental friendliness.

[0003] 3D printing, as a rapid prototyping technology, has made significant progress in materials science and engineering in recent years. Its unique forming method and material adaptability have made it possible to prepare novel sound-absorbing materials. Meanwhile, cryogenic casting, a method that utilizes specific phenomena during the solidification process to prepare complex structural materials, can produce materials with porous, lightweight, and high-strength properties, making it suitable for the preparation of sound-absorbing materials.

[0004] Therefore, how to utilize 3D printing and cryogenic casting technologies to solve the problems of high cost, long cycle, and low material utilization in the traditional sound-absorbing material preparation process is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a method, product, and application for preparing broadband high-strength sound-absorbing materials using 3D printing-assisted cryogenic casting.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing broadband high-strength sound-absorbing materials using 3D printing-assisted cryogenic casting includes the following steps:

[0008] A Helmholtz resonant cavity was prepared by using 3D printing technology to fabricate polymer I and polymer II, and then the slurry was dispersed and oriented in the Helmholtz resonant cavity by cryogenic casting process to prepare a broadband high-strength sound-absorbing material.

[0009] Beneficial effects: This invention uses impedance-matching polymer I composite material and polymer II with excellent mechanical properties to prepare a single-skin Helmholtz resonator structure with certain mechanical properties. Polymer II is a common engineering thermoplastic fiber reinforced material. For fluid environments, polymer I is mainly used to seal the Helmholtz resonator hole and has the characteristic that sound waves are not easily reflected directly. In gas environments, a closed structure is not required.

[0010] This invention addresses the narrow bandwidth and efficiency issues of existing materials in terms of absorption frequency. It proposes to prepare sound-absorbing structural materials using directional orientation through cryogenic casting to improve the sound absorption bandwidth and efficiency. Furthermore, to address the poor mechanical properties of cryogenically cast sound-absorbing materials, a mechanically robust framework is fabricated using 3D printing technology without sacrificing sound absorption efficiency, resulting in a structural material with specific mechanical properties. Based on this, a Helmholtz resonant structure is designed to further enhance the sound absorption coefficient at a specific frequency.

[0011] Among them, the cryogenic casting process refers to the preparation of structural sound-absorbing materials with complex structures by subjecting the dispersion in the prepared slurry I to a temperature field orientation condition through a physical process of low-temperature solidification and sublimation. Its principle is as follows: Figure 2 and 3 As shown, the printed Helmholtz structure 5 is placed in the freezing chamber, and slurry I (6) is injected into it and submerged the Helmholtz structure 5; under the action of the cold electrode 1 and the heating device 3, a temperature gradient from bottom to top is ensured, and supercooling is used to achieve Figure 3 The growth of ice crystals; during the growth process, the ice crystals repel and aggregate the mixture of fibers or particles in slurry I, thereby controlling its orientation; finally, the sound-absorbing structural material is prepared by freeze-drying.

[0012] Preferably, polymer I is a polymer material with a low reflectivity, including but not limited to natural rubber or polyurethane polymer.

[0013] Preferably, the polymer II includes, but is not limited to, one or any of the following: polyamide, polyphenylene sulfide, polyether ether ketone, polystyrene, polyethylene, polycarbonate, phenolic resin, and glass fiber reinforced epoxy resin.

[0014] More preferably, the compressive strength of the material formed by the polymer II scaffold can reach 50-120 kPa, which is much higher than the 6-12 kPa of the material obtained by single cryogenic casting; the resonant sound absorption bandwidth of cryogenic casting and Helmholtz structure can reach 5.6 kHz, which is much wider than 0.5 kHz in a specific frequency range.

[0015] Preferably, the slurry is obtained by dispersing a dispersion in a solvent;

[0016] The dispersion is generally a fiber, particle, or sheet material, including but not limited to one of carbon fiber, glass fiber, or graphene nanosheets.

[0017] More preferably, the solvent is water or a gel.

[0018] Preferably, it is necessary to select a suitable polymer I with impedance matching and a support material polymer II with suitable strength according to the specific working conditions.

[0019] Furthermore, the operating conditions refer to the spatial environment in which the sound-absorbing object is located, including the atmosphere, ocean, and solids; for example, the acoustic characteristics of air include a sound speed of 418 m / s and a density of 1.23 kg / m³. 3 The characteristic impedance is 340 Ω; the characteristic impedance Z is the ratio of density to longitudinal wave velocity. The acoustic characteristic impedance of water is approximately 1.56 Ω.

[0020] Table 1 shows a comparison of the characteristic impedance and reflection coefficient of common polymers with those of metals:

[0021] Table 1

[0022] Material Characteristic impedance (Z) Reflectance coefficient (R) aluminum 17.00 69.7％ steel 41.30 86.2％ iron 24.30 77.7％ Titanium alloy 27.30 79.9％ (50V / O) Glass Fiber / Epoxy 6.04 35.5％ (60v / o) Graphite / Epoxy Resin 4.65 25.5％ (50V / O) Boron / Epoxy Resin 6.38 37.6％ acrylic resin 3.15 12.0％ Phenolic resin 1.90 1.2％ polycarbonate 2.71 7.7％ polyethylene 2.94 10.0％ polystyrene 2.52 6.0％ polyurethane 1.59 1.0％ Rubber (natural) 1.74 0.4％

[0023] Furthermore, impedance matching refers to whether the characteristic impedances of sound waves are close during transmission, which can also be observed using the reflection coefficient, L. iw As shown below:

[0024]

[0025] Wherein: Z i ,、Z w These represent the characteristic impedance of sound waves in the two materials, respectively.

[0026] More preferably, the 3D printing process parameters are optimized based on the selected polymer II, such as controllable parameters like melt extrusion deposition printing speed and temperature, or parameters like photopolymerization exposure time and waiting time. Then, a multi-layer Helmholtz resonator structure with a single skin is fabricated using the equipment according to the structure preset in step two.

[0027] Preferably, the structure of the Helmholtz resonant cavity and the number of Helmholtz layers are designed according to the required sound absorption frequency. The number of layers is a single limitation on the sound absorption frequency of the sound-absorbing material. The absorption frequency bandwidth is increased by designing series connection of different Helmholtz resonant structures.

[0028] Preferably, the method for calculating the sound absorption frequency of the Helmholtz resonant cavity structure is as follows:

[0029]

[0030] Where c represents the speed of sound, S represents the cross-sectional area of ​​the resonant structure opening, d represents the opening diameter, l represents the opening bottleneck depth, and V represents the resonant cavity volume.

[0031] Preferably, the cryo-casting process involves pouring a slurry into the Helmholtz resonant cavity under freezing conditions. By utilizing the change in temperature gradient, water molecules crystallize along the gradient direction to displace and connect the dispersion into a shape. Specifically, it includes the construction of a temperature gradient field, slurry preparation, cryo-casting, and freeze-drying.

[0032] Preferably, the starting temperature of the temperature gradient is -30℃ to -80℃.

[0033] A method for preparing broadband high-strength sound-absorbing materials using 3D printing-assisted cryogenic casting.

[0034] Application of a broadband high-strength sound-absorbing material in sound barriers.

[0035] Preferably, the sound barrier is applied to the outer shell of spacecraft, cabin equipment, aircraft engine compartment, cockpit, or large instruments, and can also be used for sound insulation in industrial workshops, car door panels, or entertainment venues.

[0036] Compared with the prior art, the present invention has the following advantages and technical effects:

[0037] This invention combines 3D printing and cryogenic casting technologies. It uses 3D printing to fabricate a single skin with an internal Helmholtz resonator structure, and cryogenic casting utilizes the highly anisotropic curing behavior of a solvent as a template to controllably fabricate a sound-absorbing structure. This innovative fabrication method improves the performance and efficiency of sound-absorbing materials, solving many problems associated with traditional sound-absorbing material fabrication processes, such as high cost, long production cycles, and low material utilization. This invention utilizes 3D printing to manufacture specific structural shapes on demand, achieving a certain degree of sound absorption and mechanical properties in the sound-absorbing material; simultaneously, the directional orientation achieved by cryogenic casting technology enables effective sound absorption over a wide frequency range, significantly enhancing the sound absorption performance of the material. Attached Figure Description

[0038] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0039] Figure 1 This is a schematic diagram of the Helmholtz resonator structure in Example 1;

[0040] The labels are: 1 Polymer material I, 2 Polymer material II, 3 Fiber or particle dispersion, etc.

[0041] Figure 2 This is a schematic diagram of the cryogenic casting process in this invention;

[0042] The labels are: 1 cold electrode, 2 metal, 3 temperature control, 4 insulation board, 5 sound-absorbing structural component, 6 slurry I;

[0043] Figure 3 This illustrates the principle of the cryogenic casting process in this invention.

[0044] Figure 4 This is a schematic diagram illustrating the principle of 3D printing and freeze casting for preparing sound-absorbing materials in this invention.

[0045] Figure 5 The diagram shows the acoustic performance test results of Example 2 in this invention. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0049] Example 1

[0050] A method for preparing broadband high-strength sound-absorbing materials using 3D printing-assisted cryogenic casting includes the following steps:

[0051] (1) First, based on the underwater sound absorption environment, polymer I polyurethane, which matches the water impedance, is selected as the sealing material for the Helmholtz resonator component. This facilitates the incident sound waves into the Helmholtz resonator cavity. The characteristic impedance of seawater is approximately 1.56, and the characteristic impedance of polyurethane is approximately 1.59. The reflection coefficient is: L iw Approximately 1%. A suitable polymer II polyamide 6 composite material was selected as the main body of the Helmholtz resonator component based on the application conditions. The polyurethane and polyamide raw materials were dried at 60℃ and 80℃ respectively for 5 hours.

[0052] (2) Based on the resonant frequency of the Helmholtz resonance structure Design a resonator structure with a series size of 3 stages. The frequency range can be increased by changing the cavity size.

[0053] Where S is l1 is 1 mm, d1 is 2 mm, and V1 is 0.15 cm. 3 l1 is 0.7mm, d1 is 2mm, and V1 is 1.5cm. 3 Through software simulation, the sound absorption frequency range (sound absorption efficiency greater than 50%) of the material structure was obtained as 200-1000Hz and 2000-3000Hz, while the actual sound absorption range was 400-1000Hz and 1500-2500Hz.

[0054] (3) The structure designed in step (2) is materialized using a commercial 3D printer to obtain a Helmholtz resonator, the structure of which is as follows: Figure 1 As shown.

[0055] During the printing process, printing parameters were continuously optimized to stabilize the performance of the Helmholtz resonator structure. The optimized printing parameters for polymer I were: polyurethane: printing temperature 220℃, heated bed temperature 40℃, printing speed 40mm / s, layer height 0.2mm; and for polymer II, the optimized printing parameters were: polyamide: printing temperature 240℃, heated bed temperature 50℃, printing speed 30mm / s, layer height 0.2mm.

[0056] (4) 2,2,6,6-Tetramethylpiperidine-1-oxygen radical (TEMPO)-oxidized cellulose nanofibers (CNFs) were mixed with water and dispersant hydroxyethyl cellulose (1.5 g / L), and the CNF concentration was adjusted to 0.5 wt%. The mixture was stirred for 10 min under ultrasonic mechanical stirring at a stirring rate of 500 r / min to form a slurry. The slurry was placed in the cooling orientation device cavity along with the Helmholtz resonant cavity prepared in step (3). After freezing in a refrigerator at -18°C for 24 hours, it was non-directionally frozen in liquid nitrogen (-196°C). By controlling the temperature of the freezing source and the supercooling of the slurry, specifically the temperature gradient between the slurry and the contact area with the cold electrode and the non-contact area in the other direction, the orientation speed of the ice crystals was controlled by the driving force of the temperature gradient. The greater the supercooling or temperature gradient, the easier it is for the solute in the initial region to be coated by the ice crystals. When the supercooling is small, the repulsive force between the solute and the ice crystals is large, the interleaving is reduced, and thus the orientation of CNFs is achieved. To determine the stability of fiber orientation, the temperature for the cold stage was set at -30°C for 20 minutes. After orientation, the crystal template in the slurry was immediately removed using a freeze dryer, leaving the oriented portion intact to obtain the sound-absorbing material.

[0057] The absorption bandwidth of sound-absorbing materials with an absorption rate of over 50% is shown in Table 2.

[0058] Table 2 Effective Sound Absorption Bandwidth

[0059]

[0060] Example 2

[0061] A method for preparing broadband high-strength sound-absorbing materials by 3D printing-assisted cryogenic casting differs from Example 1 only in that polymer I is polyethylene, polymer II is a polyamide composite material, the slurry remains the same, and the array is increased to 4.

[0062] Where S is V is 0.5cm 3 Keeping the values ​​unchanged, l1 is 1mm, d1 is 2mm; l2 is 1mm, d2 is 1mm; l3 is 2mm, d3 is 0.5mm; l4 is 1mm, d4 is 0.5mm, corresponding to frequencies of approximately 5600Hz, 3400Hz, 1500Hz, and 1900Hz respectively.

[0063] The printing parameters for polymer polyurethane are: printing temperature 210℃, heated bed temperature 60℃, printing speed 40mm / s, and layer height 0.2mm; the printing parameters for polymer II remain unchanged.

[0064] Its tested acoustic performance is as follows Figure 5 As shown in Table 3, the sound absorption performance of the structured material with increased fiber orientation is superior to that of the material with only Helmholtz resonator structure. Furthermore, for the structure with only Helmholtz resonator, its absorption frequency is closely related to its structure, exhibiting four corresponding peaks. Analysis of the effective absorption bandwidth shows that increasing the array size helps to improve the absorption bandwidth. However, due to the reflection limitation of polymer I, the bandwidth with an absorption coefficient greater than 50% is reduced. But simultaneously, based on the increase in array size and the left shift of the frequency, the overall bandwidth with an absorption coefficient greater than 80% is increased.

[0065] Table 3 Effective Sound Absorption Bandwidth

[0066]

[0067] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing broadband high-strength sound-absorbing materials using 3D printing-assisted cryogenic casting, characterized in that, Includes the following steps: A Helmholtz resonant cavity was prepared by using 3D printing technology to fabricate polymer I and polymer II, and then the slurry was dispersed and oriented in the Helmholtz resonant cavity by cryogenic casting process to prepare a broadband high-strength sound-absorbing material. The polymer I is a polymer material with a low reflectivity; the polymer material with a low reflectivity includes natural rubber or polyurethane; The polymer II includes one or any combination of polyamide, polyphenylene sulfide, polyether ether ketone, polystyrene, polyethylene, polycarbonate, phenolic resin and glass fiber reinforced epoxy resin; The slurry is obtained by dispersing a dispersion in a solvent; The dispersion comprises one of carbon fiber, glass fiber, or graphene nanosheets; The structure of the Helmholtz resonator and the number of Helmholtz layers are designed according to the required sound absorption frequency. The method for calculating the sound absorption frequency of the Helmholtz resonant cavity structure is as follows: Where c represents the speed of sound, S represents the cross-sectional area of ​​the resonant structure opening, d represents the opening diameter, l represents the opening bottleneck depth, and V represents the resonant cavity volume. The number of layers mentioned is a single limitation on the sound absorption frequency of the sound-absorbing material. By designing series connection of different Helmholtz resonant structures, the absorption frequency bandwidth can be increased.

2. The method for preparing broadband high-strength sound-absorbing materials using 3D printing-assisted cryogenic casting according to claim 1, characterized in that, The cryogenic casting process involves pouring a slurry into the Helmholtz resonant cavity under freezing conditions. By utilizing the change in temperature gradient, water molecules crystallize along the gradient direction, displacing and connecting the dispersion to form a shape.

3. The method for preparing broadband high-strength sound-absorbing materials using 3D printing-assisted cryogenic casting according to claim 2, characterized in that, The starting temperature of the temperature gradient is -30℃ to -80℃.

4. The broadband high-strength sound-absorbing material prepared by the method for preparing broadband high-strength sound-absorbing material by 3D printing assisted cryogenic casting as described in any one of claims 1-3.

5. The application of the broadband high-strength sound-absorbing material as described in claim 4 in sound barriers.

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