ACOUSTIC INSULATING GLAZING FOR AN AIRCRAFT

Abstract

The present invention relates to glazing formed from a first material, comprising a sound insulation zone extending along a first length l along the main surface, the sound insulation zone having a first thickness h1 of the material, the first thickness h1 varying, as a function of a coordinate x, along the first length l, proportionally to a value of xn, where n is a real number strictly greater than 1, from a minimum thickness h1min to a maximum thickness h1max, the first length l being predetermined such that the minimum thickness h1min is less than or equal to one-third of the maximum thickness h1max. Figure for the abstract: Fig. 5

Description

Title of the invention: ACOUSTIC INSULATING GLAZING FOR AN AIRCRAFT FIELD OF INVENTION

[0001] The present invention relates to aircraft glazing having acoustic insulation properties, and more particularly to an aircraft window or windscreen comprising glazing having such properties. STATE OF THE ART

[0002] With reference to [Fig. 1], it is known to mount a glazed element 1, preferably a window 12 or a windshield 13, to the fuselage of an aircraft. The window 12 may comprise an outer pane of glass 2 and an inner pane of glass 2, which are mounted on a metal frame 14 within a sealing gasket 15. The sealing gasket 15 covers the edge of the outer and inner panes of glass 2. The sealing gasket 15 is held in place by a metal profile 16 mounted on a hinge 17, which is fixed to the metal frame 14.

[0003] The acoustic insulation of an aircraft glazing element can depend on several parameters: temperature variations outside the aircraft, temperature variations inside the aircraft, mechanical stresses at the boundaries of the glazing element, the geometry and composition of the glazing element, and / or variations in the material characteristics of the glazing element with temperature and the mechanical stresses imposed on the glazing element. Therefore, modeling the acoustic insulation properties of a glazing element can be complex.

[0004] It is known to improve the acoustic insulation of an aircraft glazed element by increasing the thickness of the glazing of the glazed element.

[0005] However, the increase in the thickness of the outer glazing 2 is limited by the bulk of the outer glazing 2 in the porthole 2 and by the costs involved in increasing this thickness. Description of the invention

[0006] An object of the invention is to propose a glazed element exhibiting superior acoustic insulation compared to a known glazed element, at least in a range of audible frequencies.

[0007] This objective is achieved within the framework of the present invention by means of a glazing extending along a principal surface and formed of a first material, the glazing comprising a sound insulation zone extending along a first length l along the principal surface, the sound insulation zone having a first thickness hj of the material, the first thickness hj varying, as a function of a coordinate x, along of the first length / proportionally to a value of xn, where n is a real number strictly greater than 1, from a minimum thickness h Imin to a maximum thickness h lmax, the first length / being predetermined so that the minimum thickness h Imin is less than or equal to one third of the maximum thickness h lmax •

[0008] The present invention is advantageously complemented by the following features, taken individually or in any of their technically possible combinations: - the glazing comprises a central part and a peripheral part, the peripheral part being arranged around the periphery of the central part relative to the main surface and in direct contact with the central part, the central part having a first thickness h Imax of the material in contact with the peripheral part, and the peripheral part comprising the acoustic insulation zone, - the glazing is a monolithic aircraft glazing, - the first material is isotropic, - n is strictly greater than 5 / 3, and preferably strictly greater than 2, - n is strictly less than 100, - the acoustic insulation zone forms a thinning of the glazing from the central part to an edge of the glazing, and n being preferably a real number greater than or equal to 2, -the central part has two opposing edges, and the peripheral part is arranged in contact with the two edges, the peripheral part preferentially surrounding the central part, - the soundproofing zone has at least one recess, n preferably being a real number greater than or equal to 5 / 3, - the hollow has an elliptical and preferably circular shape, - an opening is formed in the center of the recess, - the glazing includes a viscoelastic heat sink, the heat sink being fixedly mounted in contact with at least part of the acoustic insulation zone, the heat sink being formed by a viscoelastic material having a first loss factor / / ; strictly greater than 0.05, in particular strictly greater than 0.10, and preferably strictly greater than 0.15.

[0009] Another aspect of the invention is a glazed element, comprising at least two glazings, each glazing being a glazing according to an embodiment of the invention, the two glazings being superimposed, the glazed element comprising at least one spacer configured to separate the two glazings.

[0010] Advantageously, the spacer is formed by a material having a value of the real part E' of the Young's modulus less than 20 MPa.

[0011] Another aspect of the invention is an aircraft window, comprising glazing according to an embodiment of the invention.

[0012] Another aspect of the invention is an aircraft windscreen, comprising glazing according to an embodiment of the invention. DESCRIPTION OF THE FIGURES

[0013] Other features, objectives and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0014] [fig. 1] - the [fig. 1] schematically illustrates a cross-section of a known porthole,

[0015] [fig.2] - Fig.2 schematically illustrates a cross-section of a glazing unit according to a method of realization of the invention,

[0016] [fig.3] - Fig.3 schematically illustrates glazing according to one embodiment of the invention,

[0017] [fig.4] - Fig.4 schematically illustrates glazing according to one embodiment of the invention,

[0018] [fig.5] - [fig.5] schematically illustrates a cross-section of an insulation zone acoustics of glazing according to an embodiment of the invention, in which the acoustic insulation zone forms a thinning of the glazing from the central part to an edge of the glazing,

[0019] [fig.6] - Fig.6 schematically illustrates a cross-section of an insulation zone acoustics of glazing according to an embodiment of the invention, in which the acoustic insulation zone has a recess in the glazing,

[0020] [fig.7] - [fig.7] schematically illustrates an isometric view of an area acoustic insulation of glazing according to an embodiment of the invention, in which the acoustic insulation zone has a recess in the glazing,

[0021] [fig.8] - Fig.8 schematically illustrates the profile of a thinning of an area acoustic insulation according to one embodiment of the invention,

[0022] [fig.9] - [fig.9] schematically illustrates the profile of a thinning of an area acoustic insulation according to one embodiment of the invention,

[0023] [fig. 10] - [fig. 10] schematically illustrates the profile of a thinning of an area acoustic insulation according to one embodiment of the invention,

[0024] [fig. 11] - Fig. 11 schematically illustrates the profile of a thinning of an area acoustic insulation according to one embodiment of the invention,

[0025] [fig. 12] - [fig. 12] schematically illustrates the profile of a thinning of an area acoustic insulation according to one embodiment of the invention,

[0026] [fig. 13] - Fig. 13 schematically illustrates glazing comprising a heat sink viscoelastic material fixedly mounted on the acoustic insulation area,

[0027] [fig. 14] - Fig. 14 schematically illustrates a glazed element according to an embodiment of the invention, comprising two panes of glass,

[0028] [fig. 15] - Fig. 15 schematically illustrates a glazed element according to an embodiment of the invention, comprising two panes of glass,

[0029] [fig. 16] - [fig. 16] is a diagram illustrating the acoustic insulation of different glazings as a function of the frequency of a wave incident on the glazings,

[0030] [fig. 17] - [fig. 17] is a diagram illustrating the acoustic insulation of different glazings as a function of a wave incident on the glazings,

[0031] [fig. 18] - Fig. 18 schematically illustrates two glazing units, one of which is curved, according to an embodiment of the invention,

[0032] [fig. 19] - the [fig. 19] is a diagram illustrating the acoustic insulation of different glazings as a function of the frequency of a wave incident on the glazings.

[0033] Throughout the figures, similar elements bear identical reference numerals. DEFINITIONS

[0034] The term "loss factor rj" of a material, in the case of a material with a complex Young's modulus, refers to the ratio between the imaginary part E' of the material's Young's modulus and the real part E' of the material's Young's modulus. The loss factor rj of a material is defined by the international standard ISO 18437-2:2005 (Mechanical vibration and shock — Characterization of the dynamic mechanical properties of viscoelastic materials — Part 2: Resonance method, section 3.2). Preferably, the loss factor rj can be defined for a predetermined frequency. In this context, "a material has a first loss factor greater than a certain value" means that the material has a first loss factor rj greater than the value for each of the frequencies in the audible frequency range, that is, in a frequency range extending from 20 Hz inclusive to 20,000 Hz inclusive. and preferably between 20 Hz inclusive and 10 kHz inclusive.

[0035] The term "a value of the real part E' of the Young's modulus of a material is greater than a value" means that a value of the real part E' of the Young's modulus of the material is greater than the value of the real part E' of the Young's modulus of the material for each of the frequencies in the audible frequency range, that is to say in a frequency range extending between 20 Hz inclusive and 20,000 Hz inclusive, and preferably between 20 Hz inclusive and 10 kHz inclusive.

[0036] The real part E' and the imaginary part E” of Young's modulus can be defined for a predetermined temperature. The temperature range considered in the present invention is between -90°C and 60°C. In the present invention, "the real part E' of Young's modulus of a material is greater than a value" means that the material has a real part E' of Young's modulus greater than the value for each of the temperatures between -90°C and 60°C. In this context, "a material has a first loss factor r) greater than a value" means that the material has a first loss factor rj greater than the value for each of the temperatures between -90°C and 60°C.

[0037] A dynamic characterization of a material is performed on a Metravib-type viscoanalyzer under the following measurement conditions. A sinusoidal load is applied to the material. A measurement sample of the material to be measured consists of two rectangular parallelepipeds, each parallelepiped having a thickness of 3.31 mm, a width of 10.38 mm, and a height of 6.44 mm. Each parallelepiped formed by the material is also referred to as a shear specimen. The excitation is implemented with a dynamic amplitude of 5 pm around the rest position, traversing the frequency range from 5 Hz to 700 Hz, and traversing a temperature range from -90°C to +60°C.

[0038] The viscoanalyzer allows each specimen (each sample) to be subjected to deformations under precise temperature and frequency conditions, and the displacements of the specimen, the forces applied to the specimen and their phase shift to be measured, which allows the measurement of rheological quantities characterizing the material of the specimen.

[0039] The exploitation of the measurements makes it possible in particular to calculate the Young's modulus E of the material, and particularly the real part E' of the Young's modulus and the imaginary part E” of the Young's modulus of the material, and thus to calculate the tangent of the loss angle (or loss factor) rj (also designated by tan 0).

[0040] A value of the real part E' of Young's modulus and / or a loss factor rj of a material are measured without the material being prestressed.

[0041] The term “glazing” means a structure comprising at least one sheet of organic or mineral glass, preferably adapted for mounting in an aircraft.

[0042] The glazing may comprise a single sheet of glass or a multi-layered glazed assembly of which at least one layer is a sheet of glass.

[0043] A glazing unit may include a sheet of organic glass. Preferably, the organic glass is formed from a compound comprising acrylates, preferably polymethyl methacrylate (PMMA). It may also be formed from polycarbonate.

[0044] A glazing unit may comprise a glazing assembly. The glazing assembly comprises at least one sheet of glass. The glass may be organic or mineral glass. The glass may be tempered. The glazing assembly is preferably laminated glazing. "Laminated glazing" is defined as a glazing assembly comprising at least two sheets of glass and an interlayer film made of plastic, preferably viscoelastic, separating the two sheets of glass. The plastic interlayer film may comprise one or more layers of a viscoelastic polymer such as poly(vinyl butyral) (PVB) or an ethylene-vinyl acetate (EVA) copolymer. The interlayer film is preferably made of standard PVB or acoustic PVB (such as single-layer or three-layer acoustic PVB). Acoustic PVB may comprise three layers: two outer layers of standard PVB and an inner layer of PVB with added plasticizer to make it less rigid than the outer layers.

[0045] An “ellipse” is understood to be a closed plane curve obtained by the intersection of a right circular cone with a plane, provided that the plane intersects the axis of rotation of the cone or cylinder. The ellipse is a conic section with an eccentricity strictly between 0 and 1. The ellipse is also the locus of points whose sum of distances to two fixed points, called foci, is constant. DETAILED DESCRIPTION OF THE INVENTION

[0046] General architecture and theoretical elements

[0047] With reference to [Fig. 1], [Fig. 5], and [Fig. 6], a glazing unit 2 extends along a principal surface 3. The glazing unit 2 is formed of a first material. The glazing unit 2 includes a sound insulation zone 11 extending along a first length 1 along the principal surface 3.

[0048] The sound insulation zone 11 has a first thickness h of the material. The first thickness h varies, as a function of a coordinate x, along the first length l proportionally to a value of xn, where n is a real number strictly greater than 1, from a minimum thickness hImin to a maximum thickness hmax, the first length l being predetermined such that the minimum thickness hImin is less than or equal to one-third of the maximum thickness hlmax. The coordinate x is equal to zero when the thickness hj of the sound insulation zone 11 is equal to the minimum thickness hlmin. When the coordinate x is equal to the first length l, the thickness hi of the sound insulation zone 11 is equal to the maximum thickness hmax. The first length l preferably extends along a principal direction 6, the principal direction 6 being locally parallel to the principal surface 3.

[0049] Thus, glazing 2 has a higher acoustic insulation than the acoustic insulation of a known glazing.

[0050] Indeed, the paper Mironov et al. (Mironov, MA, 1988, “Propagation of a flexural wave in a plate whose thickness decreases smoothly to zero in an afinite interval”, Soviet Physics Acoustics-USSR, 34(3), 318-319) describes how a decrease in the thickness of a thin plate at its edges can render the edges non-reflective to flexural waves in the plate material, when the decrease follows a power law, such that the thickness h of the plate is proportional to x n, where n is a real number strictly greater than 1.

[0051] The thickness h of the glazing 2 in the acoustic insulation zone 11 can be defined by the following formula (1):

[0052] hj (x) = e.xn (1)

[0053] where e is a proportionality factor.

[0054] The phase velocity cb of the bending waves can be defined as a function of the thickness h(x) of the glazing 2 by the following formula (2):

[0055] / Eh(xfa:2 V74 <2) Lb b2 / j(l-v2). /

[0056] where E is the Young's modulus of the material, q is the density of the material, v is the Poisson's ratio of the material, h(x) is the thickness of the plate at the x coordinate and co is the incident acoustic fundamental frequency.

[0057] From the phase velocity cb in the acoustic insulation zone 11, it is possible to calculate a transit time of a bending wave propagating in the acoustic insulation zone 11. When the thickness h lmin tends towards zero, the transit time tends towards infinity. Thus, the incident bending wave is not reflected by an edge of the glazing 2, which increases the acoustic insulation of the glazing 2.

[0058] The term “acoustic black hole” refers to the acoustic insulation zone 11. The glazing 2 comprises at least one acoustic black hole. The glazing 2 may comprise a plurality of acoustic black holes, and preferably an array of acoustic black holes. With reference to [Fig. 2], the glazing 2 may be entirely formed by a single acoustic black hole.

[0059] In practice, it is not possible to manufacture a thickness hmin of zero. The inventors have found that the sound insulation effect appears when the first length l is predetermined such that the minimum thickness hmin is less than or equal to one-third of the maximum thickness hmax. In particular, the first length l is predetermined such that the minimum thickness hmin is less than or equal to one-fifth of the maximum thickness hmax. More preferably, the first length l is predetermined such that the minimum thickness hmin is less than or equal to one-tenth of the maximum thickness hmax.

[0060] The inventors also found that the sound insulation effect appears for n strictly greater than 1, in particular strictly greater than 5 / 3, and preferably strictly greater than 2. In addition, n can be strictly less than 100, so as to avoid a reflection at the junction between the central part 4 and the peripheral part 5.

[0061] The sound insulation zone 11 may have a size greater than or equal to the first length l along a second principal direction, the second direction principal being locally perpendicular to the first principal direction 6 and locally parallel to the principal surface 3.

[0062] Adaptation to the visual comfort of a user

[0063] With reference to [Fig. 3] and [Fig. 4], the glazing 2 comprises a central part 4 and a peripheral part 5. The peripheral part 5 is arranged at the periphery of the central part 4 with respect to the main surface 3 and in direct contact with the central part 5, so as to allow transmission of bending waves between the central part 4 and the peripheral part 4. Thus, the glazing 2 exhibits higher acoustic insulation than the acoustic insulation of a known glazing, while comprising a central part 4 in which the optical transmission through the glazing is not degraded compared to the optical transmission of a known glazing.

[0064] The central part 4 has a thickness of the first material h 2, and has the maximum thickness h]max of the material in contact with the peripheral part 5, in a direction normal to the main surface 3. The peripheral part 5 comprises the sound insulation zone IL

[0065] With reference to [Fig. 3], the peripheral portion 5 can surround the central portion 4 with respect to the main surface 3. With reference to [Fig. 4], the peripheral portion 5 can partially border the central portion 4. In particular, the peripheral portion 5 can be arranged along an edge of the central portion 4. The glazing 2 can also comprise several disjointed peripheral portions 5 arranged around the periphery of the central portion 4 with respect to the main surface 3. In particular, the peripheral portion 5 can be arranged in contact with two opposite edges of the central portion 4.

[0066] With reference to [fig.5], the thickness h2 of the central part 4 is constant over the whole of the central part 4. Preferably, the thickness h2 of the central part 4 is between 100 pm and 5 cm.

[0067] A material forming the peripheral part 5 and a material forming the central part 4 are preferably the same first material. Thus, the manufacture of the glazing 2 is facilitated.

[0068] The glazing 2 can be a monolithic aircraft glazing. Thus, machining of the acoustic insulation zone 11 is facilitated, while avoiding reflection of bending waves at the junction between the central part 4 and the peripheral part 5.

[0069] The glazing 2 can be made of an organic glass, in particular polymer methacrylate (PMMA). Thus, machining the peripheral part 5 is easier compared to machining soda-lime glass, while also allowing the integration of the glazing 2 into a porthole 12.

[0070] Acoustic insulation zone 11

[0071] With reference to [fig. 5], the sound insulation zone 11 can form a min The glazing 2 is cut from the central part 4 to an edge of the glazing 2. Preferably, n is a real number greater than or equal to 2. The acoustic insulation zone 11 thus forms a blade extending along the second principal direction 16. Thus, it is possible to increase the acoustic insulation of the glazing 2 compared to a known glazing, while also facilitating the manufacture of the glazing 2. Preferably, the acoustic insulation part 2 extends along the second principal direction 19 over a length greater than or equal to the length 1.

[0072] With reference to [Fig. 6] and [Fig. 7], the sound insulation zone 11 may have at least one recess 7, where n is a real number greater than or equal to 5 / 3. Preferably, the recess 7 has a minimum size Wmin along the main surface 3 greater than or equal to the first length 1. The recess 7 may be elliptical, and preferably circular. An ellipse formed by the recess 7 may have a minimum radius rmin. Preferably, the minimum radius rmin of the ellipse is greater than or equal to the first length 1. The recess 7 may also be square or rectangular.

[0073] With reference to [fig.2] and [fig.6], an opening 8 can be formed in the center of the recess 7. Thus, a sound insulation zone 11 having the minimum thickness hlmin can be manufactured so that the minimum thickness hlmin is as close as possible to zero thickness, which makes it possible to increase the sound insulation of the glazing 2. Preferably, when the recess has an elliptical shape, the first length 1 is greater than the difference between the radius r or the minimum radius rmin of the recess 7 and the radius of the opening.

[0074] The modal displacements of the glazing 2, for frequencies of an incident acoustic wave greater than a cutoff frequency of the acoustic insulation zone 11, are concentrated around the edges forming the opening 8. By the ratio between the minimum thickness h Imin and the maximum thickness h lmax, the cutoff frequency of the glazing 2 can be small enough to increase the acoustic insulation of the glazing 2 in a range of audible frequencies.

[0075] With reference to [Fig. 8], [Fig. 9], [Fig. 10], [Fig. 11], and [Fig. 12], the sound insulation zone 11 can have different shapes. With reference to [Fig. 8], the material can form an edge at the boundary of the sound insulation zone 11. With reference to [Fig. 9], the material can have a fork-shaped cross-section, with the sound insulation zone 11 forming two edges at its boundary. The thickness hl can, in this case, be measured by adding the thicknesses of each of the fork's branches. With reference to [Fig. 10], the material can form a recess 7. With reference to [Fig. 11], the material can form a cavity 18. In this case, the thickness hl of the sound insulation zone 11 is measured by adding the thicknesses of the material forming the cavity according to a direction locally perpendicular to the main surface 3. With reference to [Fig. 12], the sound insulation zone 11 can extend along a curved surface. In this case, the thickness hl of the sound insulation zone 11 is measured by measuring the thickness of the material along a direction locally perpendicular to the curved surface.

[0076] Viscoelastic heat sink 10

[0077] With reference to [Fig. 13], [Fig. 14], and [Fig. 15], the glazing 2 may include a viscoelastic heat sink 10. The heat sink 10 may be fixedly mounted in contact with at least a portion of the acoustic insulation zone 11. The heat sink 10 may be formed from a second viscoelastic material having a first loss factor ql strictly greater than 0.05, in particular strictly greater than 0.10, and preferably strictly greater than 0.15. Thus, the energy concentrated in an acoustic insulation zone 11 by incident bending waves is dissipated viscously, thereby reducing the reflection of a bending wave in the glazing 2 compared to a known glazing. The second material is viscoelastic, and can have a real part E' of Young's modulus of less than 100 MPa, and preferably less than 10 MPa.

[0078] With reference to [Fig. 13], the heat sink 10 can be fixedly mounted on a portion of the acoustic insulation zone 11 having a thickness between hlmin and hlmax / 2. Thus, the bending waves are dissipated by the viscoelastic heat sink 10 at the point where they are most concentrated. Preferably, a portion of the heat sink 10 is in contact with the portion of the acoustic insulation zone 11 having the minimum thickness hlmin. Preferably, the heat sink 10 can be formed by a layer of viscoelastic material fixedly mounted on the acoustic insulation zone, the thickness of the viscoelastic material layer being greater than hlmin / 2, in particular greater than hlmin, and preferably greater than hlmax.

[0079] The heat sink 10 can be made of a material selected from silicone, nitrile, and polyurethane. Preferably, the second material has a glass transition temperature (Tg) below 50°C, and preferably below 30°C. Thus, the second material can dampen bending waves with audible frequencies. Preferably, the second material can have a mass density greater than 100 kg / m³, in particular greater than 500 kg / m³, and preferably greater than 1000 kg / m³. The viscoelastic properties of known materials can be measured by the methods described herein. The heat sink material 10 can have a glass transition temperature between -80°C and -50°C inclusive. For example, the heat sink material 10 can comprise methyl vinyl silicone (MVQ) crosslinked with benzoyl peroxide. The heat sink material 10 can also be a porous material.The material loss factor. It can also be adjusted by a tackifying agent, for example, a glycerin ester, calcium carbonate, or carbon nanotubes. For example, Weber's Weberseal PU 40 polyurethane sealant (registered trademark) has a loss factor of 0.41 and a Young's modulus value of 7.2 MPa. For example, Sikaflex PRO-11 FC polyurethane sealant (registered trademark) has a loss factor of 0.20 and a Young's modulus value of 1.2 MPa.

[0080] Glazed element 1 and porthole 12

[0081] Another aspect of the invention is a glazed element 1. The glazed element 1 comprises at least two panes of glass 2. The two panes of glass 2 may be superimposed. The glazed element 1 comprises at least one spacer 9 configured to separate the two panes of glass 2. Preferably, the glazed element 1 may be an aircraft window 12.

[0082] With reference to [Fig. 14], the spacer 9 can be a piece formed from a third material, having a thickness, arranged in contact with each of the two glazing units 2, each glazing unit being in contact on either side of the piece. The third material can have a value of the real part E' of the Young's modulus strictly less than 20 MPa, and preferably strictly less than 10 MPa. Thus, the incident bending waves, from the central part 4 to the peripheral part 5, can be transmitted to the peripheral part 5 without being reflected by excessive rigidity of the material of the central part 4 imposed by a rigid spacer. The third material can have a mass density greater than 100 kg / m³, in particular greater than 500 kg / m³, and preferably greater than 1000 kg / m³.The third material may have a damping factor strictly greater than 0.05, in particular strictly greater than 0.10, and more preferably greater than 0.5. The third material and the second material may be the same material.

[0083] The spacer 9 can be a sealing gasket arranged between the two panes of glass 2. The spacer 9 can be arranged on the central part 4 of each of the two panes of glass 2, at the edge of the peripheral part 5. Thus, the spacer 9 does not obstruct the transmission of light through the central part 4.

[0084] With reference to [fig. 15], the spacer 9 can be a sealing gasket configured to receive each of the glazing units 2. The spacer 9 can preferably comprise two housings, preferably two notches, each housing being configured to receive an edge of a glazing unit 2. The edge of the glazing unit 2 received by the housing can be the peripheral part 5.

[0085] The spacer 9 may include the viscoelastic heat sink 10. In this case, a portion of the spacer 9 configured to receive a glazing 2 is formed by a third material having a first loss factor r)} strictly greater than 0.05, in particular strictly greater than 0.10, and preferably strictly greater than 0.15. Thus, the energy concentrated in an acoustic insulation zone 11 by incident bending waves is dissipated in a viscous manner, which makes it possible to reduce the reflection of a bending wave in the glazing 2 compared to known glazings.

[0086] Figure 16 illustrates the acoustic insulation of different glazing units as a function of the frequency of an incident acoustic wave. Curve (a) illustrates the acoustic insulation of a known porthole, comprising two superimposed glazing units separated by a layer of air. Curve (b) illustrates the acoustic insulation of a porthole 2 according to an embodiment of the invention, comprising two superimposed glazing units separated by a layer of air. The thicker of the two glazing units includes an acoustic black hole, formed by a thinning of the glazing unit 2 from the central portion 4 to an edge of the glazing unit 2. Curve (c) illustrates the acoustic insulation of a porthole 2 according to an embodiment of the invention, comprising two superimposed glazing units 2 separated by a layer of air. The thinner of the two glazing units includes an acoustic black hole, formed by a thinning of the glazing unit 2 from the central portion 4 to an edge of the glazing unit 2.Curve (d) illustrates the acoustic insulation of a porthole 2 according to an embodiment of the invention, comprising two superimposed panes of glass 2 separated by a thickness of air. Each pane of glass 2 includes an acoustic black hole, formed by a thinning of the pane of glass 2 from the central part 4 to an edge of the pane of glass 2.

[0087] Figure 17 illustrates the sound insulation of a known glazing unit and through a glazing unit according to an embodiment of the invention, as a function of the frequency of an incident acoustic wave. Curve (e) illustrates the sound insulation of a known porthole. The porthole comprises a first circular glazing unit with a thickness of 12.7 mm and a second circular glazing unit with a thickness of 6.1 mm. The diameter of each glazing unit is 520 mm. The two glazing units are separated by a 5 mm air gap. Curve (f) illustrates the sound insulation of a porthole 2 according to an embodiment of the invention. The porthole 2 comprises a first circular glazing unit with a thickness hl of the central portion 4 of 12.7 mm, and a second circular glazing unit with a thickness hl of the central portion 4 of 6.1 mm. Each pane of glass has a diameter of 520 mm. The two panes of glass are separated by a 5 mm air gap.Each of the first glazing 2 and second glazing 2 includes an acoustic black hole, formed by a thinning of the glazing 2 from the central part 4 to an edge of the glazing 2. Each glazing 2 includes a heat sink 10, fixedly mounted on the acoustic insulation zone 11 of the glazing.

[0088] Windscreen 13

[0089] Another aspect of the invention is an aircraft windshield 13, comprising a glazing 2 according to an embodiment of the invention. Preferably, the glazing 2 has a curved principal surface 3. With reference to [Fig. 18], the inventors discovered that a glazing 2, having a curved principal surface 3, and comprising at least one acoustic black hole, exhibits increased sound insulation compared to the same glazing in the absence of an acoustic black hole.

[0090] Preferably, the windscreen 13 comprises a single pane of glass 2.

[0091] Figure 19 illustrates the acoustic insulation of a known windshield and a windshield 13 according to an embodiment of the invention. Curve (g) illustrates the acoustic insulation of a known windshield. The windshield is formed by PMMA glazing, and the main surface 3 of the windshield has a radius of curvature of 800 mm. Curve (h) illustrates the acoustic insulation of a windshield 13 according to an embodiment of the invention. The windshield 13 is formed by PMMA glazing 2, and the main surface 3 of the windshield has a radius of curvature of 800 mm. The windshield 13 comprises two peripheral parts 5, arranged on either side of the windshield 13. Each peripheral part 5 comprises an acoustic black hole. Each acoustic black hole is formed by a thinning of the glazing 2 from the central part 4 to an edge of the glazing 2.

[0092] Alternatively, a glazing 2 is adapted for use in vehicles other than an aircraft, such as a car or a train.

Claims

Demands

1. Glazing (2) extending along a principal surface (3) and formed of a first material, characterized in that it comprises an acoustic insulation zone (11) extending along a first length l following the principal surface (3), the acoustic insulation zone (11) having a first thickness hj of the material, the first thickness hj varying, as a function of a coordinate x, along the first length Z, proportionally to a value of xn, where n is a real number strictly greater than 1, from a minimum thickness h lmin to a maximum thickness h Imax, the first length / being predetermined so that the minimum thickness h Imin is less than or equal to one third of the maximum thickness h lmax.

2. Glazing (2) according to claim 1, comprising a central part (4) and a peripheral part (5), the peripheral part (5) being arranged at the periphery of the central part (4) with respect to the main surface (3) and in direct contact with the central part (4), in which: - the central part (4) has a first thickness h lmax of the material in contact with the peripheral part (5), - the peripheral part (5) includes the acoustic insulation zone (H).

3. Glazing (2) according to claim 1 or 2, glazing (2) being monolithic aircraft glazing.

4. Glazing (2) according to any one of the preceding claims, wherein the sound insulation zone (11) forms a thinning of the glazing (2) from the central part (4) to an edge of the glazing (2).

5. Glazing according to claim 4, wherein the central part (4) has two opposite edges, and wherein the peripheral part (5) is arranged in contact with the two edges.

6. Glazing (2) according to any one of the preceding claims, wherein the sound insulation zone (11) has at least one recess (7).

7. Glazing (2) according to any one of the preceding claims, comprising a viscoelastic heat sink (10), in which the heat sink (10) is fixedly mounted in contact with at least a part of the sound insulation zone (11), the heat sink (10) being formed of a viscoelastic material having a first loss factor / / ; strictly greater than 0.05, in particular strictly greater than 0.10, and preferably strictly greater than 0.

15.

8. Glazed element (1), comprising at least two glazings (2), each glazing (2) being a glazing (2) according to any one of claims 1 to 7, the two glazings (2) being superimposed, the glazed element (1) comprising at least one spacer (9) configured to separate the two glazings (2).

9. Glazed element (1) according to claim 8, wherein the spacer is formed by a viscoelastic material having a value of the real part of Young's modulus E' of less than 20 MPa.

10. Aircraft porthole (12), comprising glazing (2) according to any one of claims 1 to 7.

11. Aircraft windscreen, comprising glazing (2) according to any one of claims 1 to 7.

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