CN112669800A - Film-porous material composite structure with high-efficient sound absorption performance - Google Patents
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Abstract
The invention provides a film-porous material composite structure with high-efficiency sound absorption performance, which consists of a porous material substrate and a film fixedly connected to one end face of the porous material substrate in an attached mode. The film adopts a metal film or a flexible film, and the porous material is a fiber porous material or a foam material; when the film is a metal film, the porous material is a fiber porous material, and the metal film is fixedly connected with the edge of the end face of the porous material substrate. When the film is a flexible film, the porous material is made of foam material, and the flexible film is fixedly connected with the end face of the porous material substrate in a full-bonding or edge-bonding mode. The sound absorption material provided by the invention is thin, is 1/8-1/10 of the thickness of the sound absorption material used in the industry at present when in use, has high-efficiency sound absorption performance, and can reduce the cost; and the film and the porous material are combined, so that the diversity of the porous material structure is realized, and the broadband sound absorption performance of the porous material is effectively improved.
Description
Technical Field
The invention relates to the technical field of noise control, in particular to a film-porous material composite structure with high-efficiency sound absorption performance.
Background
With the development of society, the invention and the use of various machines and equipment bring great convenience to the life of people and prosperity to the world. But at the same time, it is inevitable to bring noise to people's life and work. In environments that affect human health, noise pollution is second only to atmospheric pollution. The noise pollution can cause great harm to the physiological, psychological and surrounding environment aspects of people, for example, the long-term action of low noise level can cause the increase of the annoyance degree of people, and further cause physiological pathological changes; high noise levels can also cause diseases such as deafness; in addition, noise can also cause damage to machinery, construction, materials, and the like. Noise control is thus of particular importance. The main methods of noise control are active noise reduction and passive noise reduction, wherein the active noise reduction adopts the anti-phase action of secondary sound waves and primary sound waves to eliminate the sound waves, the method can completely eliminate the primary sound waves and is an effective method for eliminating the sound, but because the development of a sound generating device of a secondary sound source is not up to the requirement, if the noise is generally random broadband sound waves, the current sound generating device can not meet the requirement of the noise frequency band, and the application cost is very high, so the active noise reduction is rarely applied to practical engineering. The passive noise reduction is mainly realized by adopting a sound absorption and insulation material or a structure, wherein the sound absorption material is mainly used for absorbing and attenuating incident wave energy to reduce the noise intensity. The sound absorption material has wide application in practice, such as common foam sound absorption materials, such as foam plastics, foam metal and the like, and fiber porous materials, such as superfine glass fiber, stainless steel felt, polyester fiber felt and the like. Such porous materials have excellent sound absorption properties.
The sound-absorbing materials are mainly classified into porous sound-absorbing materials and resonant sound-absorbing materials (e.g., cavity type mufflers). Wherein the porous material has broadband and high sound absorption characteristics, and is wide in application occasions; the resonance sound absorption is narrow-band sound absorption and is generally applied to special occasions such as pipeline sound elimination and the like; the two are used differently. The general noise is characterized by random broadband, when sound waves enter a porous material pore channel, air molecules and wall surfaces are rubbed to consume sound energy, and the complex structure of the pore channel embodies the broadband sound absorption characteristic and has a large sound energy consumption effect, so that the porous material has excellent sound absorption performance, and the porous sound absorption material is also effectively applied to noise reduction, such as the application of various foam and fiber porous materials. The research on porous sound-absorbing materials has been pursued for higher sound-absorbing coefficient and wider sound-absorbing frequency band.
The parameters of the porous sound absorption material for controlling the sound absorption performance comprise thickness, porosity, pore diameter and other factors, the larger the thickness is, the better the sound absorption performance is, but the sound absorption performance cannot be increased if the thickness exceeds a certain thickness (such as more than 100mm), and on the contrary, the cost is increased; the porosity is in a certain range (such as 0.75-0.98), and the sound absorption performance is good; the sound absorption effect is better when the aperture is within a certain range of 0.1 mm-1 mm; when the aperture is larger than 1mm, the sound resistance is small, sound waves easily pass through and are not absorbed, the sound absorption performance is poor, the aperture is too small (such as smaller than 0.1mm), the sound resistance is large, the sound waves are not easy to enter materials, and therefore the sound absorption performance is not absorbed, and the sound absorption performance is also poor.
The resonant sound absorption material mainly comprises a cavity resonant structure formed by a film or a thin plate and an air layer at the back of the film or the thin plate, sound waves enter the cavity through the vibration of the film or the thin plate, the cavity is caused to resonate, and the structure is derived from the evolution of a Helmholtz resonator and absorbs sound. The volume of the cavity determines the resonance of the cavity under a certain fixed frequency to play a sound absorption role, so that the volume of the cavity determines a sound absorption frequency band, and the sound absorption frequency band is very narrow and can be generally used as a sound wave filter or narrow-band sound absorption. When the structure is applied to broadband noise, the sound absorption frequency band of the structure needs to be widened, a typical representative of the development of the cavity material is a micro-perforated plate sound absorber invented by Masda 29495, the sound absorption structure has a wider frequency band, and the sound absorption frequency band of the sound absorption structure is still far smaller than that of a porous material.
When the film is used as a sound absorption material at present, a resonance sound absorption structure is adopted. The film is added in front of a certain cavity, such as a leather drum structure, when sound waves are radiated to the skin (film) of the drum, the film is caused to vibrate, so that the sound waves are transmitted into the cavity, and the cavity is caused to resonate to absorb sound; however, the cavity structure has the sound wave amplification effect, namely the resonance effect, so that secondary sound can be generated when the cavity structure is not applied properly. The sound absorption frequency band is still limited by the volume of the cavity, namely narrow-band sound absorption. Structurally, in the cavity sound absorber, an air layer left behind the cavity sound absorber plays a main role in sound absorption, and meanwhile, the reserved air layer also limits the application of materials. This structure has natural drawbacks for use in the field of noise control. With the development of new technology, for noise control, people pursue high sound absorption performance and optimization and high efficiency of material parameters, for example, the sound absorption performance is high while the thickness of the material is required to be reduced, so that the high-efficiency sound absorption effect is realized. When the porous material is used as a sound absorption material at present, the thickness is about 10cm generally, and the thickness can be increased according to the requirement in the common engineering. In fact, as the sound absorbing material, when the thickness is increased to a certain extent, the sound absorbing performance reaches the limit, that is, the sound absorbing performance is not increased by increasing the thickness. Therefore, if the application thickness of the material can be reduced, i.e. the material is required to absorb sound efficiently, the sound absorption combination performance of the material is a leap.
Disclosure of Invention
As mentioned above, the application of the film in the noise control field is very wide, such as sound generating devices like speakers, but at present, when the film is used together with the porous material, a wrapping method is generally adopted, that is, the film material is wrapped outside the sound absorbing material, in order to allow the film to be used for the functions of dust prevention and sound transmission, and the connection between the film and the porous material is not fixed, so that the film cannot play a significant sound absorbing role.
At present, the research on the structural composition of the film and the porous material to form a new sound absorption material is not reported yet. The invention firstly provides a thin material formed by compounding a film and a porous material, has broadband sound absorption performance, and is a high-efficiency and excellent sound absorption material.
The technical scheme of the invention is as follows:
the film-porous material composite structure with high-efficiency sound absorption performance comprises a porous material substrate and a film which is attached and fixedly connected to one end face of the porous material substrate.
Further, the film is a metal film or a flexible film.
Further, the porous material is a fibrous porous material or a foam material.
Further, when the film is a metal film, the metal film is fixedly connected with the edge of the end face of the porous material substrate.
Further, when the film is a metal film, the porous material is a fibrous porous material.
Furthermore, the thin film is a copper film with the thickness of 0.01mm-0.1 mm; the porous material is a copper fiber porous material, the diameter of the copper fiber is 0.01mm-0.2mm, and the porosity is 0.50-0.99.
Further, when the film is a flexible film, the flexible film is fixedly connected with the end face of the porous material substrate in a full-bonding or edge-bonding mode.
Furthermore, the film adopts a flexible film, and when the sound absorption performance of medium and low frequencies needs to be improved, the flexible film and the end face of the porous material substrate are fixedly connected in a full-bonding mode.
Further, when the film is a flexible film, the porous material is a foam material.
Further, the film is a PE film, and the porous material is melamine foam.
Advantageous effects
The invention provides a sound absorption material compounded by a film and a porous material, which has the following advantages:
1. the thickness is thin: when in use, the thickness of the sound absorption material used in the industry at present is 1/8-1/10, so that the sound absorption material has high-efficiency sound absorption performance and can reduce the cost;
2. the film and the porous material are combined, the diversity of the porous material structure is realized, and the broadband sound absorption performance of the porous material is effectively improved.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic structural diagram of a copper film-copper fiber composite material. Coating glue on the excircle of a copper fiber matrix to form a belt-shaped ring with the width of 2-3 mm; sticking the copper mould on the copper fiber matrix; combining the copper fiber and copper mold composite structure sample.
FIG. 2 is a graph showing the sound absorption curves of a copper fiber porous material with a material thickness of 2mm and a copper fiber porous material-copper film composite structure with a material thickness of 2 mm.
FIG. 3 is a graph of sound absorption coefficient curves of a copper fiber porous material with a material thickness of 10mm and a copper fiber porous material-copper film composite structure with a material thickness of 10 mm.
FIG. 4 is a graph showing sound absorption curves of a copper fiber porous material-copper film (bonded) and a copper fiber porous material-copper film (unbonded) composite structure with a material thickness of 10 mm.
FIG. 5 is a graph showing sound absorption curves of a copper fiber porous material with a material thickness of 10mm and a copper fiber porous material-latex film composite structure with a material thickness of 10 mm.
FIG. 6 is a graph showing the sound absorption curves of a composite structure of 10mm foam and 10mm foam-PE film.
FIG. 7 is a graph of sound absorption for a composite structure of 10mm foam-PE film (bonded) and 10mm foam-PE film (unbonded) material thickness.
FIG. 8 is a graph of sound absorption curves for a composite structure of 10mm foam-PE film (fully bonded) and 10mm foam-PE film (closed loop bonded) material thickness.
FIG. 9 is a graph showing sound absorption curves of a composite structure of a copper fiber porous material + copper film (full bonding) with a material thickness of 10mm and a copper fiber porous material + copper film (closed ring bonding) with a material thickness of 10 mm.
FIG. 10 is a schematic view of the bonding mode; (a) bonding a closed ring; (b) fully bonding; (c) semi-bonding; (d) central line bonding; (e) and (4) bonding the central points.
Detailed Description
The invention structurally compounds the film and the porous material to form a thinner material.
The technical scheme and the effect of the invention are illustrated by specific research process analysis and combined with the embodiment as follows:
firstly, taking a metal copper film and a copper fiber porous material as research objects, and sticking the metal copper film on the surface of the copper fiber porous material pressed into a block to form a copper film-copper fiber composite material, wherein the process for forming the structure is shown in figure 1. The sound absorption is characterized in that: when the copper film faces a sound source, the composite structure material has the characteristic of broadband sound absorption when the thickness is thin (about 10 mm); and when the copper fiber porous material faces the sound source, the copper film faces away from the sound source, the effect of the copper film is eliminated, and the effect is only the sound absorption effect of the copper fiber porous material.
The sound absorption principle of the copper film-copper fiber composite material is as follows: when sound waves are radiated to the surface of the copper film, firstly, the sound waves cause the copper film to vibrate, and the radiated sound is transmitted into the internal copper fiber porous material to be absorbed; meanwhile, the vibration of the copper film can convert sound energy into vibration to be transmitted into the copper fiber solid to cause solid sound transmission consumption, and secondly, because the copper film is very thin, the sound can simultaneously penetrate through the copper film to be transmitted to the copper fiber porous material to be absorbed. The two modes jointly dissipate the function of sound energy, so that the sound-absorbing material has the property of broadband sound absorption.
The copper film-copper fiber porous material composite structure consists of three parts:
(1) common open-cell porous material-copper fiber porous material. Generally, the surface characteristic impedance of the open-cell porous material is matched with that of air, sound waves easily enter the interior of the porous material through the air, the sound waves entering the interior can cause the movement of an air medium, and friction is generated between the sound waves and the inner surface of the material to be converted into heat for consumption, namely, sound energy is converted into heat. The material has broadband sound absorption characteristics, after other parameters are determined, the sound absorption coefficient depends on the thickness of the material, the larger the thickness is, the better the sound absorption performance is, when the thickness is less than 10mm, the sound absorption performance is generally lower, for example, a 10mm pure copper wire porous material, the average sound absorption coefficient is only 0.37, and the initial sound absorption frequency is 2016 Hz.
When sound waves are radiated on the surface of the porous material, if the sound waves encounter gaps, the sound waves enter the material, if the material per se encounters impedance mismatch, and most of the sound waves are reflected. Therefore, when the porous material receives sound radiation, the capacity of receiving sound waves is reduced due to the existence of actual materials on the surface, and part of the sound waves are reflected back to air and are not absorbed. When the porous material is thin, the material becomes small in acoustic resistance, and sound waves easily pass through and the sound absorption capability is reduced.
(2) And (5) a copper film. And adhering the copper film on the surface of the copper fiber porous material in a bonding mode. When the copper film faces the sound source, firstly, when sound waves are radiated to the film surface of the copper film-porous material, the sound waves can cause the vibration of the copper film due to the thinness of the copper film, the copper film plays a role in converting sound and vibration, namely a sound vibration converter, and the vibration is transmitted to the porous material through the fiber porous material and the bonding layer, so that the fiber vibration, friction and the like can be consumed in the porous material due to the vibration. The thinner the copper film is, the more easily the vibration of the film is caused, and the more favorable the sound acceptance is; secondly, because the vibration of the copper film can generate radiation sound, the sound can be transmitted into the copper fiber porous material on the other side from the air, and the sound wave enters the pore channel and is converted into heat to be consumed.
(3) Adhesion layer between copper film and porous material
When the copper film is excited by sound waves, the generated vibration waves enter the solid, and structural damping existing in the solid can consume the vibration waves to change into heat, so that part of sound can be converted into vibration. If this part of the vibration can be transmitted to the porous material, this part of the sound energy will be absorbed by the solid part of the porous material. The vibration is very easy to propagate in the solid, it is very important to connect the copper film and the porous material, if not both, then the vibration will not be transmitted to the porous material and the copper film will not function. Therefore, the connection between the copper film and the porous material is also very important, and there are three connection methods:
(a) full adhesion of copper film and copper fiber porous material surface
The copper film is completely adhered to the surface of the porous material, the film and the porous material are integrated at the moment, the vibration of the film is limited, if the film cannot vibrate, the conversion function of sound and vibration is actually lost, and therefore the connection mode is not good;
(b) copper film and copper fiber porous material open type bonding
The copper film and the surface of the porous material are bonded by adopting point mode or line, the connecting part is not enough, the vibration transmission of the film can be radiated by the edge to become secondary radiation sound, the transmission efficiency is not high, and the conversion of the sound is not good;
(c) copper film and copper fiber porous material closed type bonding
The copper film and the copper fiber porous material are bonded in a closed circular ring mode, a micro cavity is formed between the porous material and the film in the bonding mode, sound waves easily cause vibration of the film, and then the vibration is transmitted into the porous material through the bonding layer and is absorbed by the porous material. It can be seen that in the bonding mode of the membrane, the mode which is favorable for the vibration of the membrane is to form a micro-cavity, the circular ring type closed connection can transmit all vibration waves into the solid porous material through the connecting ring, the transmission efficiency is high, and the elimination of vibration is favorable. It can be seen that the copper film functions to receive, convert and transmit acoustic energy.
Of course, the above analysis of the connection mode is based on the copper film and the copper fiber porous material, because the copper film is a metal film, which is a hard film and has high rigidity, when the copper film is completely bonded with the surface of the porous material, the film cannot vibrate, but if the film is changed into a polymer film, such as a rubber film, the film is easy to excite, when the rubber film is completely bonded with the surface of the porous material, the film can still vibrate, and has a corresponding sound-vibration conversion effect, and the analysis of the following embodiment also relates to the analysis.
The copper film has different effects on absorbing sound energy because of different positions with the sound source. When the sound source faces the copper film, the sound waves can directly excite the copper film, causing vibration of the film. When the copper film faces away from the sound source, the sound source does not act directly on the surface of the film, i.e. there is no excitation of sound, and the film does not vibrate. Thus the material should be applied with the membrane facing the sound source.
In addition, the properties of the film are influenced by the type of film. For a hard thin film such as a metal film, since it is high in elasticity and rigidity, it is easy to transmit vibration by connection, but it is difficult to excite vibration, so that for a metal film, the thinner the better; for polymer films such as rubber films, the film is easily excited, and thus better connection with the matrix porous material can play a better role.
The parameters of the copper film-copper fiber porous material composite structure are as follows: the porosity range of the porous material is 0.50-0.99, the diameter of the copper fiber is 0.01-0.2 mm, and the thickness of the copper film is 0.01-0.1 mm. The connection mode of the copper film and the copper fiber porous material is edge bonding, the copper film and the copper fiber porous material are bonded into a strip-shaped closed form (as shown in figure 1), the width of the bonding strip is 2mm-4mm, the middle part of the bonding strip is not bonded, and a micro space capable of enabling the copper film to vibrate is formed on the structure. The connection mode of the copper film and the copper fiber porous material is as follows: hard or soft connections, such as welding and gluing.
Further, the requirements of the film-porous material composite structure on the material can be expanded, namely, the surface film types can be as follows: metal films, rubber films, plastic films, and the like. The kind of porous material: fibrous porous materials such as metal fiber and glass fiber porous materials, etc.; foam materials such as foam plastics and metal foams are also possible. Bonding structure form: the bonding layer is closed, wherein the enclosed micro space can be a plurality of and the area can be different; the film used may be a multi-layer adhesive combination.
The invention is described below with reference to specific examples:
example 1: 2mm copper fiber porous material + copper film (closed ring bonding)
In the first step, copper fiber with the diameter of 0.12mm and the mass of 2.9g is used, the copper fiber is disturbed and is filled into a cylindrical die to be pressed into a cylinder with the porosity of 0.75, the thickness of 2mm and the diameter of 29mm, and then the copper fiber porous material is formed, and the sound absorption coefficient curve is shown as a dotted line in figure 2. And secondly, preparing a copper film with the thickness of 0.05mm into a wafer with the diameter of 29mm, coating 502 glue on the outer edge of the wafer to form a belt-shaped ring with the width of 2-3mm, and adhering the copper wafer to a cylinder (the diameter of the cylinder is 29mm) pressed by copper fibers, thereby preparing the copper film-copper fiber porous material composite structure. Third, the material was tested for sound absorption coefficient (membrane facing the sound source).
The measured coefficient curves are shown as solid lines in fig. 2.
As can be seen from the dotted line in FIG. 2, the average sound absorption coefficient of the copper fiber porous material with the thickness of 2mm is 0.08, and the sound absorption coefficient of the material which is generally considered in the industry to be more than 0.2 is considered to have sound absorption effect. Therefore, the copper fiber porous material having a thickness of 2mm has no sound absorption, so that it has no sound absorption when the porous material is thin. When a copper film with the thickness of 0.05mm is adhered to the surface of the material, the average sound absorption coefficient can reach 0.47, and the sound absorption performance is greatly improved, as shown by a solid line in figure 2. However, when only the copper thin film is used, the copper thin film does not have a sound absorbing effect.
The copper film-copper fiber composite structure material can achieve better sound absorption performance when the thickness is 2mm, and the initial sound absorption frequency is 2264Hz, namely, no sound absorption performance exists when the initial sound absorption frequency is less than the frequency. That is to say, the sound absorption performance of the material of the structure is poor in the middle and low. But the sound absorption of medium-high frequency is excellent, the peak sound absorption frequency is 4000-5000Hz, and the sound absorption coefficient can reach more than 0.95 at most. Therefore, the composite mode can effectively improve the sound absorption performance of the thinner material at medium and high frequencies.
Example 2: 10mm copper fiber porous material + copper film (closed ring bonding)
In the first step, copper fiber with a diameter of 0.16mm and a mass of 25.9g is used, the copper fiber is disturbed and filled into a cylindrical die and pressed into a cylinder with a porosity of 0.55, a thickness of 10mm and a diameter of 29mm, and thus a copper fiber porous material is formed, and the sound absorption coefficient curve is shown by a dotted line in fig. 3. And secondly, preparing a copper film with the thickness of 0.05mm into a wafer with the diameter of 29mm, coating 502 glue on the outer edge of the wafer to form a belt-shaped ring with the width of 2-3mm, and adhering the wafer to a cylinder (the diameter of the cylinder is 29mm) pressed by copper fibers, thereby preparing the copper film-copper fiber porous material composite structure. Third, the sound absorption coefficient of the material is tested, and the sound absorption curve is shown as a solid line in fig. 3.
As can be seen from the dotted line in FIG. 3, the average sound absorption coefficient of the copper fiber porous material with the thickness of 10mm is 0.35, the initial sound absorption frequency is 2128Hz, broadband sound absorption is realized, the sound absorption at medium and low frequencies is poor (no sound absorption effect is less than 2128 Hz), and the sound absorption performance is general. As shown by a solid line in figure 3, the sound absorption coefficient curve tested after the copper film with the thickness of 0.05mm is adhered on the surface of the copper fiber material with the thickness of 10mm can be seen, the average sound absorption coefficient can reach 0.71, and the sound absorption performance is greatly improved.
The copper film-copper fiber composite structure material has excellent sound absorption performance when the thickness is 10mm, the average sound absorption coefficient reaches 0.71, and the sound absorption coefficient is improved by 91% compared with that of a pure copper fiber material. The initial sound absorption frequency is 792Hz, the low frequency is shifted by 1336Hz, the sound absorption performance of the medium and low frequency is obviously improved, and the sound absorption performance of the material with the structure at the medium and low frequency is better. The sound absorption coefficient is 0.75-0.90 at the frequency of more than 2000Hz, so that the sound absorption performance is very excellent at medium and high frequencies. It has wide band and high sound absorption coefficient.
Example 3: 10mm copper fiber porous material + copper film (not bonded)
The sound absorption coefficient of the material was measured by using the sample of example 2, i.e., a cylinder having a thickness of 10mm and a diameter of 29mm, and forming a disc having a diameter of 29mm from a copper thin film having a thickness of 0.05mm, and covering the disc on the surface of the copper fiber porous material, without fixedly bonding the copper thin film to the copper fiber porous material, and the sound absorption curve is shown by a dotted line in fig. 4.
As can be seen from the dotted line of fig. 4, the vibration body of the copper film exhibits multimodal sound absorption characteristics, which are the vibration characteristics of the copper film. The average sound absorption coefficient of the structural material is 0.42, the initial sound absorption frequency is 856Hz, and compared with the solid line in FIG. 4, the solid line is a closed circular ring structure formed by adhering a layer of 502 glue between a copper film and a copper fiber porous material, and it can be seen that the average sound absorption coefficient is 0.71, the initial sound absorption frequency is 792Hz, and the sound absorption performance of the adhered structure is higher than that of an unbonded structure. The multiple peaks in the figure show that the copper film vibrates more, the copper film is excited, and because the copper film is not effectively connected with the matrix copper fiber porous material and has few unfixed lap joints, the vibration is transmitted into the porous material less, so the absorption is less, and the sound absorption performance is slightly better than that of the matrix copper fiber porous material (such as a dotted line in figure 3).
Example 4: 10mm copper fiber porous material + latex film (closed ring bonding)
In the first step, copper fiber with a diameter of 0.04mm and a mass of 14.5g was used, the copper fiber was disrupted, and the resulting material was packed in a cylindrical mold and pressed into a cylinder having a porosity of 0.75, a thickness of 10mm and a diameter of 29mm, thereby forming a porous material of copper fiber, and the sound absorption coefficient curve is shown by a dotted line in FIG. 5. And secondly, tightly sticking a latex film with the thickness of 0.01mm on the surface of a copper fiber cylinder with the diameter of 29mm, and coating a banded ring with the edge width of 2-3mm by adopting 502 glue, so that a composite structure of the latex film and the copper fiber porous material is manufactured. And thirdly, testing the sound absorption coefficient of the material. As shown by the solid line in fig. 5.
As can be seen from the dotted line in fig. 5, the average sound absorption coefficient of the copper fiber porous material with the thickness of 10mm is 0.37, the initial sound absorption frequency is 2016Hz, broadband sound absorption is achieved, the sound absorption at medium and low frequencies is poor (no sound absorption effect is less than 2016 Hz), and the sound absorption performance is general. The latex film with the thickness of 0.01mm is adhered on the surface of the copper fiber material with the thickness of 10mm, the average sound absorption coefficient can reach 0.45 and is improved by 21%, as can be seen from a solid line, the sound absorption peak value is in the range of 1000Hz-2000Hz, the initial sound absorption frequency is 488Hz, the sound absorption frequency is shifted to the low frequency by 1528Hz, the sound absorption performance of the medium and low frequency is obviously improved, and the sound absorption performance of the medium and high frequency is reduced to some extent.
The latex film-copper fiber composite structural material has excellent low-medium frequency sound absorption performance when the thickness of the material is 10mm, so that the latex film can be selected as a surface pasting material when the low-medium frequency sound absorption performance of the material needs to be improved.
Example 5: 10mm foam + polyethylene film (closed ring bond)
In a first step, melamine foam (open cell type), with a porosity of 0.97, a thickness of 10mm, and a sample diameter of 29mm cylinder, is used, and the sound absorption coefficient curve is shown by the dashed line in FIG. 6. And secondly, preparing a PE film with the thickness of 0.01mm into a wafer with the diameter of 29mm, coating 502 glue on the outer edge of the wafer to form a belt-shaped ring with the width of 2-3mm, and adhering the wafer to a melamine foam plastic cylinder sample (the cylinder diameter is 29mm), so that a composite structure of the PE film and the melamine foam porous material is prepared. And thirdly, testing the sound absorption coefficient of the material. The measured sound absorption coefficient curve is shown by the solid line in fig. 6.
As can be seen from the dashed line in FIG. 6, the 10mm melamine foam sound absorption curve is a flat broadband absorption with an average sound absorption coefficient of 0.41 and an initial sound absorption frequency of 1472 Hz. After the PE film is adhered to the surface of the sound absorbing film, the sound absorbing performance of the sound absorbing film is greatly improved. As can be seen by the solid line in fig. 6, the average sound absorption coefficient was 0.73, which is an improvement of 78%. The initial sound absorption frequency is moved to low frequency by 376Hz, and the overall sound absorption performance is obviously improved.
Example 6: 10mm foam + polyethylene film (unbonded)
The sample of example 5, i.e. melamine foam (open-cell type), with a porosity of 0.97, a thickness of 10mm and a sample diameter of 29mm, was used to test the sound absorption coefficient of the material, as shown by the dotted line in fig. 7, by forming a 29mm diameter circular disc from 0.01mm thick PE film, which was applied to the surface of the melamine foam, without permanent adhesion of the PE film to the melamine foam.
As can be seen from the dotted line of fig. 7, the vibration of the PE film also exhibits multimodal sound absorption characteristics, but is not as large as the amplitude of the copper film vibration, which is a characteristic of the PE film vibration. The average sound absorption coefficient of the structural material is 0.50, the initial sound absorption frequency is 1624Hz, and compared with the solid line in FIG. 7, the solid line is a closed circular ring structure which is formed by adhering a layer of 502 glue between the PE film and the fiber porous material, and it can be seen that the average sound absorption coefficient is 0.73, the initial sound absorption frequency is 376Hz, and the sound absorption performance of the adhered structure is higher than that of an unbonded structure. The multiple peaks in the figure show that the PE membrane vibrates relatively much, the membrane is excited, and because there is no effective connection to the cellular foam, and there is little loose lap, vibration is transmitted into the cellular material and is therefore absorbed only very little. Substantially the same as the sound absorption properties of the foam (as shown in dashed lines in fig. 6).
Example 7: 10mm foamed plastic + polyethylene film (full adhesion)
The sample used was identical to that of example 5, i.e.melamine foam (open-cell type), with a porosity of 0.97, a thickness of 10mm and a sample diameter of 29mm cylinder. A PE film with the thickness of 0.01mm is made into a circular sheet with the diameter of 29mm, the whole circular sheet is coated with 502 glue, and the circular sheet is adhered to a melamine foam plastic cylinder sample (the diameter of the cylinder is 29mm), so that a full-adhered PE film-melamine foam porous material composite structure is manufactured. The sound absorption coefficient of this material was tested. The measured sound absorption coefficient curve is shown by a dotted line in fig. 8, and the solid line is a sound absorption curve of the closed loop bonding manner.
As can be seen from FIG. 8, the sound absorption coefficient curves of the foam surfaces adopting the full-bonding and closed-loop bonding modes of the PE film are almost the same, and the average sound absorption coefficients are all 0.73. At 2000Hz, the sound absorption performance of the full bond is better than that of the closed ring bond. The sound absorption onset frequency of the full-face material was 776Hz, while the sound absorption onset frequency of the closed loop bond was 1096 Hz. The flexibility of the PE film is far higher than that of a metal film, the surface of the foam plastic is uneven, the film is bonded with the film, a gap for enabling the film to vibrate is still reserved, the film is still easy to excite and vibrate even though the film is fully bonded, vibration transmission is facilitated, the middle part of the closed ring bonding is not connected with the substrate, the vibration transmission efficiency of the full bonding is higher than that of the closed ring bonding, the full bonding can improve the sound absorption performance of medium and low frequencies, the sound absorption initial frequency is enabled to move to 320Hz (1096Hz-776Hz) towards the low frequency, and the moving amplitude is wide. Therefore, the flexible membrane adopts full adhesion, and can effectively improve the sound absorption performance of medium and low frequencies.
Example 8: 10mm copper fiber porous material + copper film (full adhesion)
Using the same sample as in example 2, i.e., copper fibers having a diameter of 0.16mm and a mass of 25.9g, the copper fibers were disrupted, charged into a cylinder mold, and pressed into a cylinder having a porosity of 0.55, a thickness of 10mm and a diameter of 29 mm. A copper film with a thickness of 0.05mm is made into a wafer with a diameter of 29mm, glue is coated 502 on the whole wafer, and the wafer is stuck on a cylinder (the diameter of the cylinder is 29mm) pressed by copper fibers, so that a composite structure of the copper film-copper fiber porous material is manufactured. The sound absorption coefficient of the material is tested, and the sound absorption curve is shown as a dotted line in fig. 9, and the solid line is the sound absorption curve of the closed ring bonding mode.
As can be seen from FIG. 9, the surface of the copper fiber porous material adopts a copper film full-bonding and closed ring bonding mode, the sound absorption coefficient of the closed ring bonding is 0.71, the initial sound absorption frequency is 792Hz, the full-bonding is 0.43, the initial sound absorption frequency is 368Hz, the sound absorption performance of the full-bonding in the range of 368 Hz-1500 Hz is higher than that of the closed ring bonding, a highest absorption peak is formed at 1200Hz, the sound absorption coefficient can reach more than 0.95, but the peak is very narrow, so the medium and low frequency sound absorption performance of the full-bonding is higher. Above 1500Hz, the sound absorption performance of the closed ring bonding is obviously superior to that of the full bonding. In general, closed loop bonds have higher sound absorption than full bonds. Because the rigidity of the copper film is high, if the copper film is completely bonded, the vibration of the film is limited by the bonding layer, the film is not easy to excite, and the efficiency of sound conversion vibration is reduced, so the sound absorption performance of the copper film is not as good as that of a closed ring bonding mode. But the sound absorption performance of medium and low frequency can be improved by adopting a full bonding mode.
Example 9: comparison of film bonding modes
Five bonding modes are selected for comparison, the sound absorption coefficient of the composite structure of the porous material of the membrane is tested, and the results are shown in tables 1 and 2.
TABLE 1 comparison of sound absorption properties of copper film-copper fiber porous material with different bonding methods
As can be seen from table 1, different sound absorption performances are obtained for different bonding modes of the copper film-copper fiber porous material composite structure, wherein the average sound absorption coefficient of the closed loop bonding mode is 0.71 at most, and the sound absorption coefficient of the full bonding mode is 0.43 at least. This is related to the vibration and transmission of the membrane, and the closed loop bonding can achieve vibration better than other bonding, which is a drum-like structure with fixed edges and full vibration of the tympanic membrane, and the drum sound is loud. Therefore, the sound absorption coefficient of the closed ring bonding is highest, the vibration of the full bonding limiting membrane is less in sound conversion vibration, and the sound absorption coefficient of the full bonding is minimum. While the more solid connections the better the vibration transmission needs, it can be seen that of the five types of bonding or connections, full bonding is the most sufficient connection and is the most beneficial for the transmission of vibration. The more sufficient the vibration transmission, the better the effect on low frequencies, and therefore, the starting sound absorption frequency of the full bonding is the lowest, that is, the low frequency sound absorption is excellent. The larger the bonding area is, the better the low-frequency performance is, and the middle-high frequency sound absorption performance is poorer.
In summary, the bonding mode can control the average sound absorption coefficient and the initial sound absorption frequency, and the bonding modes can be further optimized in engineering, such as bonding in various modes, namely closed ring + center and the like, so as to obtain excellent sound absorption performance.
TABLE 2 comparison of sound absorption Properties of PE film-foam materials with different adhesion modes
As can be seen from table 2, the sound absorption performance obtained for the PE film-foamed plastic porous material composite structure is different depending on the bonding manner, wherein the average sound absorption coefficient of the closed loop bonding manner is 0.73, the initial sound absorption frequency is 1096Hz, the average sound absorption coefficient of the full bonding is 0.73, and as with the closed loop bonding, the initial sound absorption frequency is 776Hz, which is 320Hz shifted from the closed loop bonding toward the low frequency, it can be seen that the sound absorption performance of the full bonding is superior to that of the closed loop bonding manner, and particularly the performance at the medium and low frequencies is superior to that of the closed loop bonding manner. The reason is that the full bonding can obtain the maximum vibration transmission, the initial sound absorption frequency moves to the low frequency, meanwhile, the PE film is light and soft, and a large number of concave-convex pits exist on the surface of the foam plastic, so that a large number of micro bubble spaces are formed when the film is bonded with the surface of the foam plastic, and a space is reserved for the vibration of the film, so that the film can be excited to fully vibrate to consume sound, and the film can transmit part of sound to the foam plastic, so that most of sound waves are absorbed, and the sound absorption performance is excellent. The bonding area of the closed ring is not as large as that of the full bonding, so the initial sound absorption frequency of the closed ring is higher than that of the full bonding. The PE film can be fully vibrated by the bonding of the closed ring, so that the sound absorption coefficient is high.
The other bonding modes have basically the same sound absorption performance, because the bonding modes are open type, vibration cannot be fully excited by sound, the bonding area is small, and vibration transmission is not sufficient, so the sound absorption performance of the bonding modes is not as good as that of the full bonding and closed ring bonding modes.
Example 10: multiple combined test results
On the base materials of the copper fiber porous material and the foamed plastic, a rubber film, a PE film, an emulsion film and a copper film are bonded and compounded with the two base materials in a closed ring bonding mode, and the sound absorption performance is tested and shown in Table 3.
TABLE 3 test results of sound absorption performance of composite structure of porous materials with different base materials and different membranes
As can be seen from table 3, when the thin copper metal fibers and the melamine foam are used as the base material, different types of film materials are adhered to the surface of the thin copper metal fibers and the melamine foam to form the film-porous material composite structure, so that the sound absorption performance is improved, wherein the most significant improvement of the sound absorption coefficient is that the PE film is adhered to the surface of the melamine foam, which is improved by 105.7%, and meanwhile, the initial sound absorption frequency is shifted to 376Hz at a low frequency. In addition, the initial sound absorption frequency moves to the low frequency most by sticking a rubber film on the surface of the copper fiber porous material, so that 1568Hz is moved, the sound absorption performance of the medium and low frequency is obviously improved, and meanwhile, the sound absorption coefficient is improved by 21.6 percent. It can be seen that the hard metal film is less advantageous than the soft organic film in terms of sound absorption frequency.
In conclusion, the sound absorption performance of the material can be obviously improved by adopting the composite structure of the film and the porous material, and the thinner material can achieve the excellent sound absorption performance by selecting the proper composite structure and the proper type of the film, so that the material has the characteristic of realizing high-efficiency sound absorption, can save the cost and is very beneficial to engineering application.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.
Claims (10)
1. A film-porous material composite structure with high-efficiency sound absorption performance is characterized in that: consists of a porous material substrate and a film which is fixedly connected with the end face of the porous material substrate in an attaching way.
2. The membrane-porous material composite structure with high sound absorption efficiency as claimed in claim 1, wherein: the film is a metal film or a flexible film.
3. The membrane-porous material composite structure with high sound absorption efficiency as claimed in claim 1, wherein: the porous material is a fibrous porous material or a foam material.
4. The membrane-porous material composite structure with high sound absorption performance as claimed in claim 2, wherein: when the film is a metal film, the metal film is fixedly connected with the edge of the end face of the porous material substrate.
5. The membrane-porous material composite structure with high sound absorption performance as claimed in claim 4, wherein: when the film is a metal film, the porous material is a fiber porous material.
6. The membrane-porous material composite structure with high sound absorption performance as claimed in claim 5, wherein: the thin film is a copper film, and the thickness of the thin film is 0.01mm-0.1 mm; the porous material is a copper fiber porous material, the diameter of the copper fiber is 0.01mm-0.2mm, and the porosity is 0.50-0.99.
7. The membrane-porous material composite structure with high sound absorption performance as claimed in claim 2, wherein: when the film is a flexible film, the flexible film is fixedly connected with the end face of the porous material substrate in a full-bonding or edge-bonding mode.
8. The membrane-porous material composite structure with high sound absorption performance as claimed in claim 7, wherein: the film adopts a flexible film, and when the sound absorption performance of medium and low frequencies needs to be improved, the flexible film and the end face of the porous material substrate are fixedly connected in a full-bonding mode.
9. The membrane-porous material composite structure with high sound absorption performance as claimed in claim 7, wherein: when the film is a flexible film, the porous material is a foam material.
10. The membrane-porous material composite structure with high sound absorption performance as claimed in claim 8, wherein: the film adopts a PE film, and the porous material adopts melamine foam.
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