Composite carbon nano tube reinforced underwater covering layer with strong sound absorption and preparation method of composite carbon nano tube reinforced underwater covering layer

Abstract

The invention provides a composite carbon nano tube reinforced underwater covering layer with strong sound absorption and a preparation method of the composite carbon nano tube reinforced underwater covering layer. The strong-sound-absorption composite carbon nanotube reinforced underwater covering layer comprises a substrate, the substrate comprises a base material and reinforcement fibers arranged in the base material, the base material is made of a styrene butadiene rubber material, the reinforcement fibers are made of carbon nanotubes, and the reinforcement fibers are uniformly fused with the base material through a solution mixing method to form the substrate. According to the composite carbon nanotube reinforced underwater covering layer provided by the invention, the double-walled carbon nanotubes are added into the styrene-butadiene rubber, so that the friction force of an interface area can be increased, the damping effect and sound absorption performance caused by friction stick-slip can be greatly improved, and the sound absorption bandwidth is widened while the low-frequency sound absorption limitation of a traditional underwater covering layer is broken through; and the composite material is very suitable for being used as a sound-absorbing covering layer in high-tip fields such as underwater submarines.

Description

Technical Field

[0001] The invention relates to the technical field of underwater sound-absorbing covering layers, in particular to a highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer and a preparation method thereof. Background Art

[0002] Unlike ground detection methods, it is difficult to use electromagnetic wave detection methods to complete underwater detection work due to the rapid attenuation of electromagnetic waves in water. As the only signal that can achieve long-distance information transmission underwater, sonar technology has become the main underwater detection method. Underwater sound-absorbing covering layers have great scientific research value. In order to improve the sound absorption performance of the underwater covering layer, it is necessary to allow the sound to enter the covering layer as much as possible and to increase the loss capacity of the covering layer as much as possible. However, most underwater covering layers currently have insufficient low-frequency and broadband sound absorption performance, and it is difficult to achieve broadband sound absorption. Therefore, designing a limited thickness underwater sound-absorbing covering layer that meets the low-frequency and broadband requirements is a key task. Summary of the invention

[0003] The main purpose of the present invention is to provide a highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer and a preparation method thereof, aiming to solve the sound absorption limitations of existing underwater covering layers while broadening the sound absorption bandwidth.

[0004] To achieve the above object, the present invention provides a highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer, comprising a substrate, the substrate comprising a substrate and reinforcement fibers arranged inside the substrate, wherein:

[0005] The base material is made of styrene-butadiene rubber material, the reinforcement fibers are made of carbon nanotubes, and the reinforcement fibers are uniformly fused with the base material through a solution mixing method to form the substrate.

[0006] Preferably, the reinforcement fibers are double-walled carbon nanotubes.

[0007] Preferably, the reinforcement fiber is a double-walled carbon nanotube with chirality of (8,8) / (13,13).

[0008] Preferably, the substrate is provided with multiple layers, the multiple layers of the substrate are bonded and fixed to each other, and the material of each layer of the substrate is composed of reinforcement fibers and base materials with different volume fractions.

[0009] Preferably, the volume fraction of the reinforcement fibers of the substrate decreases gradually along the direction close to the water side.

[0010] Preferably, the substrate is a rectangular plate-shaped structure.

[0011] Preferably, the number of layers of the substrate is optimally determined using a grid search algorithm, and the thickness of each layer of the substrate and the volume fraction of the reinforcement fibers in each layer of the substrate are parameter optimized using a BOHB algorithm.

[0012] The present invention further proposes a method for preparing the above-mentioned composite carbon nanotube-reinforced underwater covering layer with strong sound absorption, comprising the following steps:

[0013] Mixed solution: dissolving styrene butadiene rubber in acetone solvent, and then dispersing carbon nanotubes in the acetone solution containing styrene butadiene rubber;

[0014] Ultrasonic dispersion: The mixed solution is placed in an ultrasonic cleaning machine for ultrasonic dispersion to preliminarily achieve uniform dispersion of the carbon nanotubes in the styrene-butadiene rubber matrix;

[0015] Magnetic stirring: The mixed solution after ultrasonic dispersion is placed on a magnetic stirring table for mechanical stirring;

[0016] Vacuum rotary evaporation: placing the mixed solution on a vacuum water bath for rotary evaporation until all the acetone solvent is precipitated to obtain a styrene-butadiene rubber-carbon nanotube mixture;

[0017] Centrifugal degassing: Add curing agent 2-ethyl-4-methylimidazole to the styrene-butadiene rubber-carbon nanotube mixture, and then put it into a centrifugal dispersant for degassing and final mixing to eliminate bubbles in the mixture;

[0018] Mold pouring: pour the degassed and mixed styrene-butadiene rubber-carbon nanotube liquid into a polytetrafluoroethylene mold;

[0019] High temperature curing: placing the mold in an oven for high temperature curing to obtain a cured styrene-butadiene rubber-carbon nanotube composite material;

[0020] Demolding: taking the cured styrene-butadiene rubber-carbon nanotube composite material out of the mold and performing demolding.

[0021] Preferably, when the mold is placed in an oven for high-temperature curing, it is first pre-cured at 55° C. to 65° C. for 2 hours, and then cured at 145° C. to 155° C. for 8 hours to obtain a cured styrene-butadiene rubber-carbon nanotube composite material.

[0022] Preferably, when the mixed solution is placed in an ultrasonic cleaning machine for ultrasonic dispersion, the time is 1.4 hours to 1.6 hours; when the mixed solution is placed in a vacuum water bath for rotary evaporation, the temperature is 65° C. to 75° C.

[0023] The composite carbon nanotube reinforced underwater covering layer proposed in the present invention can increase the friction in the interface area by adding double-walled carbon nanotubes to styrene-butadiene rubber, and the damping effect and sound absorption performance caused by friction stick-slip will be greatly improved. While breaking the low-frequency sound absorption limitation of traditional underwater covering layers, it broadens the sound absorption bandwidth and is very suitable as a sound absorption covering layer in high-tech fields such as underwater submarines. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The molecular structure diagram of the reinforcing fiber in the highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of the highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer of the present invention;

[0026] Figure 3 A schematic diagram showing a comparison of the sound absorption coefficient of the first embodiment of the highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer of the present invention after adding reinforcement fibers and that of a pure substrate;

[0027] Figure 4 A schematic diagram showing a comparison of the sound absorption coefficients of the first embodiment and the second embodiment of the highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer of the present invention;

[0028] Figure 5 Schematic diagram of the sound absorption frequency bands of the first and second embodiments of the highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer of the present invention.

[0029] In the figure, 1- substrate, 2- reinforcement fiber.

[0030] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0032] It should be noted that in the description of the present invention, the terms "transverse", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0033] The invention provides a composite carbon nanotube reinforced underwater covering layer with strong sound absorption.

[0034] Reference Figures 1 to 3The present invention proposes a first embodiment of a highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer. In this embodiment, the highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer comprises a substrate 1, the substrate 1 comprises a substrate and a reinforcement fiber 2 arranged inside the substrate, wherein:

[0035] The base material is styrene-butadiene rubber, and its density is m =1039kg / m, Young's modulus E m =9.6×10 7 Pa, shear modulus G m =3.24×10 7 Pa, loss factor η m =1, Poisson's ratio ν m =0.48, the sound absorption effect is better. The reinforcement fiber 2 is made of carbon nanotubes, and the reinforcement fiber 2 is uniformly fused with the base material by a solution mixing method to form the substrate 1.

[0036] The reinforcement fiber 2 is made of double-walled carbon nanotubes. Compared with other hard materials, double-walled carbon nanotubes have excellent mechanical properties and a larger specific surface area. Introducing them into rubber materials can improve the acoustic properties and damping properties of rubber materials. Therefore, by extending double-walled carbon nanotubes to the field of underwater acoustic stealth, a design method for a composite carbon nanotube-enhanced underwater covering layer with strong sound absorption is proposed, which is expected to break the sound absorption limitations of traditional underwater covering layers while broadening the sound absorption bandwidth.

[0037] Specifically, the reinforcement fiber 2 has a length L f = 24.6 angstroms, and a diameter of (8,8) / (13,13) double-walled carbon nanotube with a diameter of d = 17.63 angstroms. The density of the double-walled carbon nanotube is ρ f =2785.25kg / m, Young's modulus E x =E y =210GPa, E z =1265GPa, shear modulus G xy =58GPa, G xz =G yz =130GPa, Poisson's ratio ν xy =0.3, ν xz =v yz =0.17.

[0038] Furthermore, the substrate 1 is provided with multiple layers, and the multiple layers of the substrate 1 are bonded and fixed, and the material of each layer of the substrate 1 is composed of reinforcement fibers 2 and base materials with different volume fractions. For example, the substrates 1 are bonded to each other by epoxy resin AB adhesive or modified polyurethane adhesive. In this embodiment, a substrate 1 having 4 layers is taken as an example for specific description.

[0039] Furthermore, the volume fraction of the reinforcement fibers 2 decreases gradually along the direction of the substrate 1 approaching the water side. When there are four layers of substrate 1, the volume fraction V of the reinforcement fibers 2 is f The distribution from the side close to the water is 0.5%, 1.0%, 1.5% and 2.0% respectively.

[0040] Specifically, the substrate 1 is a rectangular plate structure with dimensions of 40 mm in length, 40 mm in width and 20 mm in height.

[0041] It should be noted that adding carbon nanotube reinforcement fiber 2 to the rubber material will change the Young's modulus E, shear modulus G, Poisson's ratio v and density ρ of the material. The equivalent theory of transversely isotropic composite material parameters is as follows:

[0042]

[0043]

[0044] G c =G f V f +G m V m

[0045] υ c =υ f V f +υ m V m

[0046] ρ c =ρ f υ f +ρ m υ m

[0047] Where: E m represents the Young's modulus of the substrate, V f represents the volume fraction of double-walled carbon nanotubes. E fi represents the Young's modulus of the double-walled carbon nanotube in the i direction, i = x, z, ξ represents the size factor of the double-walled carbon nanotube, where ξ = 2(l / d), l / d represents the aspect ratio of the double-walled carbon nanotube, l is the length of the double-walled carbon nanotube, d is the diameter of the double-walled carbon nanotube, G c represents the shear modulus of the composite material, G m represents the shear modulus of the substrate, G f represents the shear modulus of double-walled carbon nanotubes, υ c represents the Poisson's ratio of the composite material, υ m represents the Poisson's ratio of the substrate, υ f represents the Poisson's ratio of double-walled carbon nanotubes, ρ c represents the density of the composite material, ρm represents the density of the substrate, ρ f represents the density of double-walled carbon nanotubes.

[0048] like Figure 3 Taking the sound absorption curve of styrene-butadiene rubber as a reference, it can be observed that the sound absorption curve corresponding to the underwater covering layer containing double-walled carbon nanotubes moves toward the low-frequency direction. The sound absorption bandwidth of 0.65 is used to characterize the sound absorption effects of the two different material structures. The lower limits of the frequencies corresponding to styrene-butadiene rubber and the underwater covering layer containing double-walled carbon nanotubes are 400Hz and 780Hz; at the same time, the sound absorption effect of the latter is better than that of the former below the frequency of 1430Hz.

[0049] The sound absorption mechanism of the underwater cover can be roughly divided into three stages: (1) sound waves enter the cover from the water, (2) sound waves propagate in the cover, and (3) sound energy dissipates in the cover. In water, the incident sound wave enters the cover material through the intermediate water medium. After adding double-walled carbon nanotubes of different contents to the underwater cover, the acoustic impedance of each layer changes, ensuring that the incident sound wave can enter the underwater cover to the greatest extent and minimize the reflected wave. At the same time, the presence of double-walled carbon nanotubes causes the plane longitudinal wave to be continuously converted into a transverse wave when propagating in the cover, thereby improving the waveform conversion process. In addition, double-walled carbon nanotubes change the propagation direction of the sound wave from the longitudinal direction to the oblique or even radial direction, increasing its propagation path in the cover, causing the sound reflection wave to scatter at multiple angles in the cover, which can significantly increase the energy loss.

[0050] The composite carbon nanotube reinforced underwater covering layer proposed by the present invention can increase the friction force in the interface area by adding double-walled carbon nanotubes to styrene-butadiene rubber, and the damping effect and sound absorption performance caused by friction stick-slip will be greatly improved, while breaking the low-frequency sound absorption limitation of the traditional underwater covering layer and broadening the sound absorption bandwidth, it is very suitable as a sound absorption covering layer in high-tech fields such as underwater submarines. From the perspective of molecules, in the initial configuration, the double-walled carbon nanotubes and styrene-butadiene rubber are mixed and meshed with each other through covalent bonds, mechanical interlocking and van der Waals interactions to form a stable interface. Once the interface is subjected to dynamic stress, the previously established mechanical locking and van der Waals interactions are destroyed, resulting in the contact between the double-walled carbon nanotubes and styrene-butadiene rubber slipping, and energy dissipation will occur in this process. Therefore, the composite carbon nanotube reinforced underwater covering layer with strong sound absorption proposed by the present invention has a better sound absorption effect, which meets the requirements of low frequency and broadband for the advancement of modern underwater vehicles.

[0051] The composite carbon nanotube reinforced underwater covering layer can be applied to covering layers with high requirements for low-frequency sound absorption. By adding double-walled carbon nanotube reinforcement fiber 2, the Young's modulus of the covering layer material is increased while maintaining the overall mass unchanged, breaking through the limitation of the traditional method of increasing the sound absorption effect by increasing the structure thickness according to the mass law.

[0052] The present invention proposes a second embodiment of a highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer. This embodiment is different from the first embodiment in that the number of substrates 1, the thickness of each substrate 1 and the volume fraction of the reinforcement fibers 2 in each substrate 1 are different.

[0053] The number of layers of substrate 1 is optimized and confirmed by grid search algorithm, and the thickness of each layer of substrate 1 and the volume fraction of reinforcement fiber 2 in each layer of substrate 1 are optimized by BOHB algorithm. Due to the limitation of computing resources, the number of layers of substrate 1 n∈[2,20] is selected during optimization. Since the number of material layers is a discrete value and the number of groups is small, the grid search algorithm is used to optimize this parameter. As for the layer thickness of the number of layers of substrate 1 and the content of double-walled carbon nanotubes therein, since they are continuous values, the BOHB algorithm is used for parameter optimization. The value range of the optimization parameters is layer thickness d∈[1mm,40mm], and the content of double-walled carbon nanotubes in each layer Vf∈[0.05%,10%].

[0054] When the total thickness of the underwater cover is 80 mm, the number of layers after optimization by BOHB algorithm is n=16, and the thickness of each layer and the content of double-walled carbon nanotubes are 9.2 mm, 5.8 mm, 6.7 mm, 9.7 mm, 2.2 mm, 1.3 mm, 1.9 mm, 3.1 mm, 8.2 mm, 4.0 mm, 9.1 mm, 1.9 mm, 1.6 mm, 2.5 mm, 6.7 mm, 6.1 mm; 9.735%, 6.675%, 7.735%, 5.085%, 1.17%, 1.64%, 5.785%, 0.845%, 1.375%, 6.94%, 3.495%, 1.025%, 0.205%, 0.28%, 0.05%, 9.5%. Taking the global sound absorption curve of the original model as the reference benchmark, Figure 4 By comparison, it can be seen that the optimized 16-layer composite carbon nanotube reinforced underwater covering layer with strong sound absorption and the 4-layer composite carbon nanotube reinforced underwater covering layer with strong sound absorption of the substrate 1 in the first embodiment can effectively improve the low-frequency sound absorption characteristics. In addition, the high performance (α≥0.65) sound absorption frequency bands of the two covering layers are as follows Figure 5 As shown, it can be observed that the optimized 16-layer composite carbon nanotube reinforced underwater covering layer with strong sound absorption extends the low frequency lower limit frequency of 388Hz of the 0.65 sound absorption bandwidth of the unoptimized original model to 299Hz. The average sound absorption coefficient of the 16-layer composite carbon nanotube reinforced underwater covering layer with strong sound absorption is 0.843734 in the frequency range of 1kHz-20kHz. Compared with the first embodiment, the average sound absorption coefficient of the optimized material is increased by 2.21%.

[0055] The present invention further provides a method for preparing a composite carbon nanotube-reinforced underwater covering layer with strong sound absorption.

[0056] In this preferred embodiment, a method for preparing the above-mentioned composite carbon nanotube-reinforced underwater covering layer with strong sound absorption comprises the following steps:

[0057] Step S10, mixing the solution: dissolving the styrene butadiene rubber in an acetone solvent, and then dispersing the carbon nanotubes in the acetone solution containing the styrene butadiene rubber;

[0058] Step S20, ultrasonic dispersion: placing the mixed solution in an ultrasonic cleaning machine for ultrasonic dispersion, so as to preliminarily achieve uniform dispersion of the carbon nanotubes in the styrene-butadiene rubber matrix;

[0059] Step S30, magnetic stirring: placing the mixed solution after ultrasonic dispersion on a magnetic stirring table for mechanical stirring;

[0060] Step S40, vacuum rotary evaporation: placing the mixed solution in a vacuum water bath for rotary evaporation until all the acetone solvent is precipitated to obtain a styrene-butadiene rubber-carbon nanotube mixture;

[0061] Step S50, centrifugal degassing: adding a curing agent 2-ethyl-4-methylimidazole to the styrene-butadiene rubber-carbon nanotube mixture, and then placing it in a centrifugal dispersant for degassing and final mixing to eliminate bubbles in the mixture;

[0062] Step S60, mold pouring: pouring the degassed and mixed styrene-butadiene rubber-carbon nanotube liquid into a polytetrafluoroethylene mold;

[0063] Step S70, high temperature curing: placing the mold in an oven for high temperature curing to obtain a cured styrene-butadiene rubber-carbon nanotube composite material;

[0064] Step S80, demolding: taking the solidified styrene-butadiene rubber-carbon nanotube composite material out of the mold and performing demolding.

[0065] Specifically, in step S70, when the mold is placed in an oven for high-temperature curing, it is first pre-cured at 55°C to 65°C for 2 hours, and then cured at 145°C to 155°C for 8 hours to obtain a cured styrene-butadiene rubber-carbon nanotube composite material.

[0066] In step S20, the mixed solution is placed in an ultrasonic cleaning machine for ultrasonic dispersion for 1.4 to 1.6 hours. In step S40, the mixed solution is placed in a vacuum water bath for rotary evaporation at a temperature of 65°C to 75°C.

[0067] Since the key to the preparation of nano-reinforced composite materials lies in how to effectively and evenly disperse the nano-reinforcement in the matrix, the preparation method proposed in the present invention realizes the uniform dispersion of double-walled carbon nanotubes in the styrene-butadiene rubber matrix by adopting a solution mixing method and combining ultrasonic dispersion, magnetic stirring, vacuum rotary evaporation, centrifugal degassing and other steps, thereby improving the mechanical properties and thermal stability of the composite material. At the same time, the method is simple to operate, easy to control, and suitable for large-scale industrial production.

[0068] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer, characterized in that: The invention comprises a substrate, wherein the substrate comprises a base material and reinforcement fibers arranged inside the base material, wherein: The base material is made of styrene-butadiene rubber material, the reinforcement fibers are made of carbon nanotubes, and the reinforcement fibers are uniformly fused with the base material through a solution mixing method to form the substrate.

2. The highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer as claimed in claim 1, characterized in that: The reinforcement fibers are double-walled carbon nanotubes.

3. The highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer as claimed in claim 2, characterized in that: The reinforcement fiber is a double-walled carbon nanotube with chirality of (8,8) / (13,13).

4. The highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer as claimed in claim 1, characterized in that: The substrate is provided with multiple layers, the multiple layers of the substrate are bonded and fixed, and the material of each layer of the substrate is composed of reinforcement fibers and base materials with different volume fractions.

5. The highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer as claimed in claim 4, characterized in that: The volume fraction of the reinforcement fibers of the substrate decreases gradually along the direction close to the water side.

6. The highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer as claimed in claim 1, characterized in that: The substrate is a rectangular plate structure.

7. The highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer according to any one of claims 1 to 6, characterized in that: The number of layers of the substrate is optimally determined using a grid search algorithm, and the thickness of each layer of the substrate and the volume fraction of the reinforcement fibers in each layer of the substrate are parameter optimized using a BOHB algorithm.

8. A method for preparing the highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer according to claim 1, characterized in that: The following steps are involved: Mixed solution: dissolving styrene butadiene rubber in acetone solvent, and then dispersing carbon nanotubes in the acetone solution containing styrene butadiene rubber; Ultrasonic dispersion: The mixed solution is placed in an ultrasonic cleaning machine for ultrasonic dispersion to preliminarily achieve uniform dispersion of the carbon nanotubes in the styrene-butadiene rubber matrix; Magnetic stirring: The mixed solution after ultrasonic dispersion is placed on a magnetic stirring table for mechanical stirring; Vacuum rotary evaporation: placing the mixed solution on a vacuum water bath for rotary evaporation until all the acetone solvent is precipitated to obtain a styrene-butadiene rubber-carbon nanotube mixture; Centrifugal degassing: Add curing agent 2-ethyl-4-methylimidazole to the styrene-butadiene rubber-carbon nanotube mixture, and then put it into a centrifugal dispersant for degassing and final mixing to eliminate bubbles in the mixture; Mold pouring: pour the degassed and mixed styrene-butadiene rubber-carbon nanotube liquid into a polytetrafluoroethylene mold; High temperature curing: placing the mold in an oven for high temperature curing to obtain a cured styrene-butadiene rubber-carbon nanotube composite material; Demolding: taking the cured styrene-butadiene rubber-carbon nanotube composite material out of the mold and performing demolding.

9. The method for preparing a highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer as claimed in claim 8, characterized in that: When the mold is placed in an oven for high-temperature curing, it is first pre-cured at 55° C. to 65° C. for 2 hours, and then cured at 145° C. to 155° C. for 8 hours to obtain a cured styrene-butadiene rubber-carbon nanotube composite material.

10. The method for preparing a highly sound-absorbing composite carbon nanotube-reinforced underwater covering layer according to claim 8, characterized in that: When the mixed solution is placed in an ultrasonic cleaning machine for ultrasonic dispersion, the time is 1.4 hours to 1.6 hours; when the mixed solution is placed in a vacuum water bath for rotary evaporation, the temperature is 65° C. to 75° C.

Images