• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A soundproof panel with sandwich structure comprises two outer walls, a core, and modifying elements which are held by the core in a fractal distribution. The panel presents a compromise that is improved between sound attenuation efficiency and panel weight.
    公开号:FR3017235A1
    申请号:FR1400313
    申请日:2014-02-04
    公开日:2015-08-07
    发明作者:Frank Simon；Jean Luc Brian；Valia Fascio；Philippe Vie
    申请人:Office National dEtudes et de Recherches Aerospatiales ONERA；Ateca；
    IPC主号:
    专利说明:

    [0001] The present invention relates to a soundproofing panel which is effective in transmission and which has a sandwich structure. Such panels already exist before the present invention and comprise: two external walls which are parallel to each other; a core, which is rigidly connected to the outer walls so that shear stresses are transmitted between this core and each of the outer walls, and the core keeping the outer walls at a distance from each other so as to limit an intermediate space; and - modifying elements which are contained in the intermediate space, and held by the core at locations which are fixed with respect to directions parallel to the outer walls. An acoustic wave which is incident on one of the outer walls of such a panel is transformed into a stationary vibration of the panel by bending, this stationary vibration being a superposition of eigen modes of the panel which are excited by the incident acoustic wave. Then, the transmitted acoustic wave, which emerges from the other outer wall, results from emission contributions that are generated by the eigen modes excited. In general, before the present invention, the acoustic attenuation efficiency in transmission of such a panel is obtained by using weight-based modifying elements, or by using modifying elements that are capable of absorbing energy. vibration of the panel by bending, or who are able to change the stiffness of the panel. Optionally, many of these effects are combined by choosing appropriate modifying elements. For example, the document FR 2 815 603 describes such a panel in which the core is constituted by a honeycomb structure, and the cells of this structure are filled with solid bodies or hollow. The acoustic damping is then obtained by friction between the solid bodies, or against the outer walls, or against the honeycomb structure. But such a soundproofing panel is particularly heavy because the space between its outer walls is filled by the solid bodies.
    [0002] WO 2006/128632 discloses another panel which has the sandwich structure recalled above, and in which recesses are arranged inside the core so that the panel has a one-piece behavior at low acoustic frequency, and a double wall behavior for high acoustic frequencies. But such a panel is more expensive because of the realization of the recesses in the soul, respecting appropriate dimensions for these recesses. From this situation, the purpose of the present invention is to propose new soundproofing panels which offer a better compromise between the acoustic attenuation efficiency in transmission, the weight of the panels, their manufacturing cost, and the space requirement. they produce. In particular when they are intended for use on board aircraft or aircraft, the added mass of each onboard panel is a very important constraint. To achieve these or other objects, the present invention provides a soundproof panel with two outer walls, core and modifying elements as described above, but in which the locations of the modifying elements form, in projection on a surface parallel to the outer walls, a fractal distribution with a basic pattern that is implemented at least once by self-similarity. In other words, the corresponding fractal order value is greater than or equal to unity. In addition, the fractal distribution is such that the modes of vibration of the flexural panel, said concentrated modes, have vibration bellies whose amplitudes are not zero that within a restricted area of the panel which is circumscribed by at least some of the modifying elements contributing to the fractal distribution. Then, the acoustic wave that is transmitted results only from emission contributions that are generated within the restricted area of the panel when the eigen modes excited are all concentrated modes. Thus, for a panel according to the invention, the area which is effective to produce the transmitted wave is restricted to a portion of the panel which is smaller than this, so that the radiating energy of the acoustic wave that is transmitted is decreased accordingly.
    [0003] On the other hand, the bellies of the eigen modes which really participate in the production of the transmitted wave being contained only inside the restricted zone, a destructive interference effect becomes more important, between the contributions of emission of two bellies of the same own mode that are neighbors. This effect further contributes to reducing the radiant energy of the transmitted wave. The incident and transmitted waves that are considered may have respective propagation directions that are identical or different depending on the directivity of the attenuation that is sought. The acoustic attenuation efficiency in transmission for a soundproofing panel according to the invention is therefore not based on an effect of mass increase, or ballast effect, or on an absorption effect of the vibration energy of the panel by flexion, but on a particular distribution of the modifying elements, of fractal type. This particular distribution controls the amplitudes of the vibration bellies of the panel by bending. In particular, the bellies that are effective to produce the transmitted wave, that is to say those whose amplitude of vibration is non-zero in the proper mode to which each of them belongs, are limited inside. of the restricted area. This zone is restricted by the fractal distribution of the modifying elements, surrounded by some of these elements. Those of the bellies of each mode of vibration of the panel by flexion which are located outside this restricted zone, have amplitudes of vibration which are null, so that they do not contribute to the production of the wave which is transmitted . In a soundproofing panel which is in accordance with the invention, the modifying elements may occupy only a small fraction of the space between the outer walls, and these elements may themselves have an individual mass which is limited. The total weight of the panel can thus be reduced. In addition, such a soundproofing panel can be produced at low cost, using inexpensive components and simple panel making processes. Optionally, the restriction of the surface of the panel which is effective to produce the transmitted wave, and the effect of destructive interference for the transmitted acoustic wave, for a panel according to the invention can be combined with additional effects of damping by absorbing part of the vibration energy of the panel by bending. However, depreciation efficiency will generally be much lower than the effectiveness of fractal distribution effects. Similarly, a possible ballast effect by the modifying elements will also be much smaller than the effects of the fractal distribution. In various embodiments of the invention, the following improvements may be adopted, in particular to achieve the objects of the invention to a superior extent: the basic pattern for the fractal distribution of the modifying elements may be implemented by self-similarity at least twice, preferably at least three times, corresponding to a value of the fractal order which is greater than or equal to two, preferably three; - this basic motif can be a Vicsek motif or a Sierpinski motif; the modifying elements may comprise spheres, preferably hollow spheres, spring elements, or portions of viscoelastic material; the core may have an alveolar structure, and in this case the modifying elements may be contained in a restricted selection of the cells of the structure, this selection of cells forming the fractal distribution of the modifying elements; - The soul can have a honeycomb structure; and the panel may be curved in at least one direction parallel to this panel. Such a soundproofing panel can be adapted to form all or part of an interior dressing cabin or cabin. In particular, it can be adapted to be disposed within an aircraft cabin or a rotary wing aircraft livable. Other features and advantages of the present invention will appear in the following description of nonlimiting exemplary embodiments, with reference to the accompanying drawings, in which: - Figure 1 is a sectional view of a soundproofing panel according to the invention; FIGS. 2a and 2b are plan views of soundproofing panels which are in accordance with the invention, and for which a Sierpinski base pattern has been implemented with a fractal order value which is equal to unity. for Figure 2a, and equal to three for Figure 2b; FIG. 3 is a plan view of another soundproofing panel which is in accordance with the invention, and for which a Vicsek base pattern has been implemented with a fractal order value equal to three; FIG. 4a is a plan view of yet another soundproofing panel in accordance with the invention, and FIG. 4b shows a natural mode of flexural vibration for the panel of FIG. 4a; - Figure 5 is an acoustic attenuation diagram, for three soundproofing panels according to the invention and for two soundproofing panels as existing before the invention; and FIG. 6 is a diagram showing the acoustic attenuation gain of four soundproofing panels according to the invention, compared to one of the two soundproofing panels existing before the invention and used for FIG. In clarity, the dimensions of some of the elements shown in Figure 1 do not correspond to actual dimensions or real size ratios. In addition, identical references which are indicated in different figures designate identical elements or which have identical functions. According to Figure 1, the soundproofing panel 10 includes the two outer walls 1 and 2, and the core 3 which is located therebetween. Each wall 1, 2 may be individually of a type and a composition known before the present invention, especially as commercially available. Preferably the walls 1 and 2 are based on at least one composite material.
    [0004] Their peripheral shape can be any: square, rectangular, trapezoidal, triangular, round, etc., depending on the use of the panel 10. Optionally, the walls 1 and 2 may have openings, and / or be preformed with a general curvature . The core 3 may consist of a honeycomb structure, for example aluminum or aluminum alloy, or even aramidic paper impregnated with a phenolic resin, such as the product which is designated commercially by Nomex ®. The axis of the honeycomb structure can be perpendicular to the walls 1 and 2. In addition, the core 3 can be glued to the two walls 1 and 2, on the surfaces thereof which are turned towards the Inside the panel 10. The cells of the honeycomb structure, which are referenced in FIG. 1, may have dimensions of between 0.4 cm and 3 cm (centimeters) parallel to the walls 1 and 2, and 3 may have a thickness of between 0.5 cm and 4 cm perpendicular to the walls 1 and 2. Figure 1 also shows an incident acoustic wave 01 which arrives from the left side on the outer wall 1, and an acoustic wave OT which is transmitted by the panel 10 from the incident wave 01, to the right of the panel 10. The two acoustic waves 01 and OT may have respective propagation directions that are identical. For such a sandwich panel 10 to vibrate effectively by bending, especially at frequencies which correspond to the range of acoustic frequencies, it is necessary for shear stresses to be transmitted between the outer wall 1 and the core 3, and also between the core 3 and the outer wall 2. Shear stress means stresses that tend to move each wall 1, 2 relative to the core 3, parallel to the walls 1 and 2 themselves. For this, the assembly between each wall 1, 2 and the core 3 must be sufficiently rigid, and assembly methods that are known to man are suitable, such as gluing methods. Modifying elements 4 are contained in a selection of the cells 30, and the manner of selecting those of the cells 30 which thus contain elements 4 is one of the characteristics of the invention. The modifying elements 4 may be of different natures, such as solid spheres, hollow spheres, hard spheres, flexible spheres, spring elements, or blocks of viscoelastic material also called "silent blocks". However, those of these modifying elements 4 that result in an improved compromise between weight reduction and acoustic damping for the panel 10 are preferred. In particular, panels according to the invention which are acoustically effective and which have a reduced total weight have been made using hollow spheres. In a soundproofing panel 10 according to the invention, the modifying elements 4 intervene by producing a local alteration of the capacity of the panel to vibrate by bending. For this, they locally modify certain parameters of the panel 10 which intervene in the vibrations thereof by bending. In particular, the modifying elements 4 can locally change the values of the apparent density of the panel 10, its absorption rate of the vibration energy, etc., between areas where modifying elements are located and zones that are lacking. More specifically, a bending wave propagating in the surface of the panel 10 is partially reflected at the boundary between two areas that are contiguous and one of which contains modifier elements 4 but not the other. The stationary wave structure that results from such reflections, in addition to the reflections on the peripheral limits of the panel 10, can be adapted to the vibration amplitudes of the bending vibration bellies, when the distribution of the modifying elements 4 is of fractal type. . In fact, such a fractal distribution has the capacity to determine these amplitudes of the bending vibration bellies of the panel, especially by means of the size of the basic pattern which is used to generate the fractal distribution, the geometry of the pattern itself. same, the number of repetitions of the pattern by self-similarity, or fractal order value, and its overall position with respect to the panel. In the embodiment of Figure 2a, the soundproofing panel 10 has a square-shaped peripheral edge, and a so-called "Sierpinski" fractal distribution pattern has been used only once. This pattern is constructed as follows: Each side of the square is divided into three equal segments, so that the surface of the panel 10 is divided into nine squares of the same surfaces. The core 3 of the panel 10, which consists of the honeycomb in the example under consideration, is then filled with modifying elements 4 in the central square, blackened in FIG. 2a, without modifying elements in the eight peripheral squares. The fractal order of the distribution of the modifying elements is thus equal to unity, and the surface filling ratio of the panel with modifying elements is 1/9 = 0.111.
    [0005] This basic pattern of Sierpinski can then be implemented again, inside each of the eight peripheral squares which have just been introduced with reference to the panel 10 of FIG. 2a, and then again again according to the same principle. , called self-similarity. This principle of fractal construction is well known, so there is no need to detail it further. The soundproofing panel 10 of Figure 2b is obtained in this way, where the squares which are blackened all correspond to areas of the panel 10 in which the core 3 is filled with modifying elements 4. The core 3 is devoid of modifying elements outside these blackened squares. The fractal order of the distribution of the modifying elements is now equal to three, and the surface coverage of the panel with modifying elements is 0.298. Figure 3 corresponds to Figure 2b, but for a basic pattern called "Vicsek". The fractal order of the distribution of the modifying elements 4 is still equal to three, but the surface filling ratio of the panel 10 with modifying elements is 0.171 using this basic pattern. This Vicsek pattern may be preferred to that of Sierpinski in Figure 2b because it produces a lower weight of the equivalent fractal order panel and for the same modifying elements that are used. The distribution that is desired according to the invention for the modifying elements 4 in the core 3 of the panel 10 can be achieved using the stencil principle. The core 3 is fixed on the outer wall 1, for example by gluing, and the panel 10 in this partial assembly state is arranged horizontally, with the core 3 which is exposed upwards. A mask provided with openings is then placed over the panel 10, on the core 3, and modifying elements 4 are spread excessively over the mask in this embodiment. The modifying elements 4 then fill the cells 30 of the honeycomb structure which constitutes the core 3 through the openings of the mask. Then the excess of modifying elements is removed, for example by scraping the upper surface of the mask. Practically, when the core 3 has a cellular structure with a size of the cells 30 which is fixed, the maximum value of the fractal order that can be achieved is limited by this size of the cells. This limitation is due to the decrease in size of the basic pattern each time it is repeated to produce an additional unit for the fractal order, and such a repetition is possible only if the basic pattern is still sufficiently large than the cells. More specifically, a soundproofing panel has natural modes of bending vibration which are each characterized by a number of vibrational bellies, and by the positions of these vibrational bellies in the surface of the panel. The incident acoustic wave 01 that arrives on the panel 10 excites several eigen modes of vibration thereof, with amplitudes and phase shifts of these eigen modes which are fixed by the positions of the vibration bellies for these eigenmodes, each compared to others. According to the invention, the modifying elements 4 are arranged in the core 3 according to a fractal distribution selected to confer a vibration amplitude which is zero at some of the eigenvalues bellies. In other words, some vibration bellies are removed, and this for at least a clean mode of the panel. These vibration bellies that are removed are located outside a restricted area inside the panel. This zone, where the vibrational bellies for the eigen mode concerned are conserved, is surrounded by modifying elements which belong to the fractal distribution. FIG. 4a is similar to FIG. 2b for another Sierpinski fractal pattern, and FIG. 4b shows a deformation of the panel of FIG. 4a according to a particular natural mode of flexural vibration. The fractal order is again equal to 3. When the invention is not implemented, for example when the modifying elements are evenly distributed throughout the entire surface of the panel, each mode own has bending vibration bellies that overlap the entire surface of the panel. Figure 4b shows that the eigen mode which is represented has only two bellies which are located inside the central square, when the panel is divided into three columns and three lines of the same widths. The lines of continuous levels shown in Figure 4b, and the dashed line lines indicate that the two bellies vibrate in phase opposition. The suppression of the bellies in the eight peripheral squares is obtained thanks to the fractal distribution of the modifying elements, according to Figure 4a. Each bending vibration mode of the panel 10 has an acoustic emission characteristic. The acoustic wave OT which is transmitted by the panel 10 results from contributions which are produced by all the eigen modes excited by the incident wave 01. These contributions are combined according to the principle of acoustic interferences, which depend on the zones of the panel. where the contributions from each eigenmode come from. Now these zones are the positions of the vibrational bellies of each eigenmode. Thus, by making it possible to suppress certain vibration bellies for clean modes of the panel 10, the fractal distribution of the modifying elements 4 makes it possible to control the energy of the acoustic wave OT which is transmitted by the panel 10, from the Incident acoustic wave 01. All natural modes of bending vibration can be determined theoretically or by numerical simulation using a computer, with the positions and amplitudes of their vibration bellies. Likewise, the OT wave that is transmitted can be reconstructed mathematically by combining the contributions of eigen modes that have been excited by the incident wave 01, again by digital simulation. The diagram of FIG. 5 shows the energy loss of the OT wave that is transmitted, relative to the incident wave 01 for five sound-absorbing panels, such that this attenuation has been measured experimentally. This attenuation is denoted T and expressed in decibels (dB) along the vertical axis. The horizontal axis identifies the frequency of the incident wave 01, expressed in hertz (Hz). The five panels used for this diagram have composite outer walls and a honeycomb core that are similar from panel to panel. Their common peripheral dimensions are 0.9 m (meter) x 0.9 m. These panels are distinguished in the following manner, by identifying them by their legend references: A: first reference panel, whose core has no modifying elements in the entire surface of the panel B: second reference panel, of which core is filled with modifying elements formed by rigid spheres, in the entire surface of the panel C: first panel according to the invention, whose core is filled with modifying elements formed by rigid spheres, according to the fractal distribution of FIG. 3 D: second panel according to the invention, whose core is filled with the same modifying elements as the panel C, but according to the fractal distribution of FIG. 2a E: third panel according to the invention, of which The core is filled with modifying elements formed by soft spheres, but also according to the fractal distribution of Figure 2a The spheres of the modifying elements that are used can be polymer when rigid, or elastomer when flexible. The sound attenuation of panel B is greater than that of panel A, because of the ballast effect that is provided by the rigid spheres. The sound attenuation of panel C is intermediate to those of panels A and B above 2000 Hz, and comparable to that of panel 25 A below this frequency value. The panels D and E have acoustic losses that are comparable between them between 200 Hz and 10 000 Hz, and also comparable to that of the panel B. The acoustic attenuation of the panel C is lower than those of the panels B, D and E partly because its ballast rate is lower. Thanks to the effect of the fractal distribution of the modifying elements in the panels D and E, the acoustic losses they provide are substantially as good as that of the panel B whereas their ballast rates are much lower.
    [0006] Finally, the diagram of FIG. 6 shows the energy loss differences AT which are calculated by numerical simulation, for panel C and for three additional panels, with respect to panel A described above. The same acoustic frequency range is considered: between 200 Hz and 10 000 Hz. The three additional panels, which are referenced C5, C10 and C15, are identical to panel C as regards the fractal distribution of the modifying elements and the power of ballast. of these. But a vibration damping power of the panel by bending is added, and varied as follows: C: null damping power for rigid spheres C5, C10 and C15: damping by the modifying elements corresponding to a loss factor The smooth curve, denoted by Cm, is a mean curve for panel C. The comparison of the attenuation values for the four panels C, C5, C10 and C15 shows that the power of damping of the modifying elements has no significant effect on the effect of the fractal distribution of these elements. It is to be understood that the present invention may be reproduced by modifying certain aspects with respect to the embodiments which have been described in detail, but while retaining at least some of the advantages that have been cited. Among the possible modifications, the following are mentioned: - basic patterns for the fractal distribution of the modifying elements, other than the Sierpinski and Vicsek motifs, can be used; the fractal order of the distribution of the modifying elements may be any, equal to one, preferably equal to two, still more preferably equal to three, and so on; the core may have a configuration other than that of a honeycomb structure; the panel may have any general curvature, a peripheral limit of any shape, and have openings in its surface; the two outer walls may have variable compositions, which may or may not be identical from one wall to the other; and the method of assembly of each wall with the core can be arbitrary, provided that it allows shear stresses to be transmitted between these three components. Finally, it is also understood that the invention may be combined with any modes of fixing the soundproofing panel on a supporting structure. In particular, the panel can be hung by localized supports, or punctual supports, or can be embedded at its peripheral edge in a holding frame. The modes of vibration of the flexural panel can then be partly determined by its mode of attachment, and the invention applies to eigen modes which are thus determined. In general, the acoustic wave that is transmitted by the panel, as considered in the present invention, does not take into account an additional acoustic transmission that would be produced directly by panel fasteners.
    权利要求:
    Claims (9)
    [0001]
    REVENDICATIONS1. Soundproofing panel (10) effective in transmission and sandwich structure, comprising: - two outer walls (1,
    [0002]
    2) parallel to each other; - a core (3) rigidly connected to the outer walls so that shear stresses are transmitted between said core and each of the outer walls, and the core maintaining the outer walls at a distance from each other so as to limit an intermediate space; and - modifying elements (4) contained in the intermediate space, and held by the core at fixed locations relative to directions parallel to the outer walls; wherein an acoustic wave (01) which is incident on one of the outer walls (1) is transformed into a stationary vibration of the panel (10) by bending, said stationary vibration being a superposition of eigen modes of the panel which are excited by the acoustic wave, and a transmitted acoustic wave (OT) which emerges from the other outer wall (2) as a result of emission contributions generated by the eigen modes excited, the panel being characterized in that the locations of the modifying elements (4) form, in projection on a surface parallel to the outer walls (1, 2), a fractal distribution with a basic pattern which is implemented at least once by self-similarity, said fractal distribution being such that bending vibrations of the panel, referred to as concentrated modes, have non-zero-amplitude vibrational bellies only within a restricted zone of the panel which is circumscribed p by at least some of the modifying elements contributing to the fractal distribution, so that the transmitted acoustic wave (OT) results only from emission contributions that are generated within said restricted area of the panel when the eigen modes are excited All of them are concentrated modes. 2. Panel according to claim 1, wherein the basic pattern is implemented at least three times by self-similarity to form the fractal distribution of the modifying elements (4).
    [0003]
    3. Panel according to claim 1 or 2, wherein the basic pattern is a Vicsek pattern or a Sierpinski pattern.
    [0004]
    4. Panel according to any one of the preceding claims, wherein the modifying elements (4) comprise spheres, preferably hollow spheres, spring elements, or portions of viscoelastic material.
    [0005]
    Panel according to any one of the preceding claims, wherein the core (3) has a honeycomb structure, and the modifying elements (4) are contained in a selection of cells (30) of said structure, said selection of alveoli forming the fractal distribution of the modifying elements.
    [0006]
    6. Panel according to claim 5, wherein the core (3) has a honeycomb structure.
    [0007]
    7. Panel according to any one of the preceding claims, said panel being curved in at least one direction parallel to said panel.
    [0008]
    8. Panel according to any one of the preceding claims, adapted to form at least a portion of an interior trim cockpit or cabin.
    [0009]
    9. Panel according to claim 8, adapted to be disposed within an aircraft cabin or a wing of a rotary wing aircraft.
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    同族专利:
    公开号 | 公开日
    FR3017235B1|2016-01-29|
    EP3103115A1|2016-12-14|
    US20170011728A1|2017-01-12|
    US9640166B2|2017-05-02|
    EP3103115B1|2019-04-24|
    WO2015117868A1|2015-08-13|
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    法律状态:
    2015-01-27| PLFP| Fee payment|Year of fee payment: 2 |
    2016-02-25| PLFP| Fee payment|Year of fee payment: 3 |
    2017-01-26| PLFP| Fee payment|Year of fee payment: 4 |
    2017-12-20| PLFP| Fee payment|Year of fee payment: 5 |
    2019-03-27| PLFP| Fee payment|Year of fee payment: 6 |
    2019-12-13| PLFP| Fee payment|Year of fee payment: 7 |
    2021-11-12| ST| Notification of lapse|Effective date: 20211005 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1400313A|FR3017235B1|2014-02-04|2014-02-04|SOUNDPROOF PANEL|FR1400313A| FR3017235B1|2014-02-04|2014-02-04|SOUNDPROOF PANEL|
    EP15703020.6A| EP3103115B1|2014-02-04|2015-01-28|Soundproof panel|
    US15/116,326| US9640166B2|2014-02-04|2015-01-28|Soundproof panel|
    PCT/EP2015/051642| WO2015117868A1|2014-02-04|2015-01-28|Soundproof panel|
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