Patent Application
20240217647
The present invention relates to an aircraft glazed unit having soundproofing properties, and more particularly to an aircraft window or windshield comprising a glazed unit having such properties.
Referring to
The soundproofing of an aircraft glazed element may depend on several parameters: a variation in the temperature outside the aircraft, a variation in temperature inside the aircraft, mechanical stresses at the limit of the glazed element, the geometry and the composition of the glazed element, and/or a variation of the characteristics of the materials of the glazed element with the temperature and the mechanical stresses imposed on the glazed element. Thus, modeling the soundproofing properties of a glazed element can be complex.
It is known to improve the soundproofing of an aircraft glazed element by increasing the thickness of a glazed unit of the glazed element.
However, the increase in the thickness of the exterior glazed unit 2 is limited by the bulk of the exterior glazed unit 2 in the window 2 and by the costs that the increase in this thickness incurs.
One aim of the invention is to propose a glazed element having a soundproofing greater than that of a known glazed element, at least in an audible frequency range.
This aim is achieved in the context of the present invention owing to a glazed unit extending along a main surface and formed by a first material, the glazed unit comprising a soundproofing zone that extends along a first length l along the main surface, the soundproofing 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 in proportion 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.
The present invention is advantageously completed by the following features, considered individually or in any technically possible combination:
Another aspect of the invention is a glazed element, comprising at least two glazed units, each glazed unit being a glazed unit according to one embodiment of the invention, the two glazed units being superimposed, the glazed element comprising at least one spacer configured to separate the two glazed units.
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.
Another aspect of the invention is an aircraft window, comprising a glazed unit according to one embodiment of the invention.
Another aspect of the invention is an aircraft windshield, comprising a glazed unit according to one embodiment of the invention.
Other features, purposes and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:
In all the figures, similar elements are marked with identical references.
“Loss factor η” of a material means, the material having a complex Young's modulus, the ratio between the imaginary part E″ of the Young's modulus of the material and the real part E′ of the Young's modulus of the material. The loss factor n of a material is defined by international standard ISO 18437-2:2005 (Mechanical vibration and shock—Characterization of the dynamic mechanical properties of visco-elastic materials—Part 2: Resonance method, part 3.2). Preferentially, the loss factor η can be defined for a predetermined frequency. “A material has a first loss factor η greater than a value” means that the material has a first loss factor η greater than the value for each of the frequencies in the audible frequency range, that is, in a frequency range extending between 20 Hz and 20,000 Hz, inclusive, and preferentially between 20 Hz and 10 kHz, inclusive.
“The real part E′ of the Young's modulus of a material is greater than a value” means that 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, in a frequency range extending between 20 Hz and 20,000 Hz, inclusive, and preferentially between 20 Hz and 10 kHz, inclusive.
The real part E′ and the imaginary part E″ of the Young's modulus can be defined for a predetermined temperature. The temperature range considered in the present invention is comprised between −90° C. and 60° C. In the present invention, “the real part E′ of the Young's modulus of a material is greater than a value” means that the material has a real part E′ of the Young's modulus greater than the value for each of the temperatures comprised between −90° C. and 60° C. In the present invention, “a material has a first loss factor η greater than a value” means that the material has a first loss factor η greater than the value for each of the temperatures comprised between −90° C. and 60° C.
A dynamic characterization of a material is carried out on a visco-analyzer of the Metravib visco-analyzer type, under the following measurement conditions. A sinusoidal load is applied to the material. A measurement sample made 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 made of the material is also referred to as a shear “test specimen”. The excitation is implemented with a dynamic amplitude of 5 μm around the rest position, covering the frequency range comprised between 5 Hz and 700 Hz, and covering a temperature range comprised between −90° C. and +60° C.
The visco-analyzer makes it possible to subject each test specimen (each sample) to deformations under precise temperature and frequency conditions, and to measure the displacements of the test specimen, the forces applied to the test specimen and their phase shift, which makes it possible to measure rheological quantities characterizing the material of the test specimen.
The use of measurements makes it possible especially 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) η (also referred to as tan δ).
A value of the real part E′ of the Young's modulus and/or a loss factor η of a material are measured without the material being pre-stressed.
“Glazed unit” is understood to mean a structure comprising at least one sheet of organic or mineral glass, preferentially suitable for being mounted in an aircraft.
The glazed unit can comprise a single glass sheet or a multilayer glazed assembly at least one sheet of which is a glass sheet.
A glazed unit may comprise an organic glass sheet. Preferably, the organic glass is formed by a compound comprising acrylates, preferably by polymethyl methacrylate (PMMA). It also can be formed by polycarbonate.
A glazed unit can comprise a glazed assembly. The glazed assembly comprises at least one glass sheet. The glass can be organic or mineral glass.
The glass can be tempered. The glazed assembly is preferably a laminated glazed unit. “Laminated glazed unit” is understood to mean a glazed assembly comprising at least two glass sheets and an interlayer film formed of plastic material, preferentially viscoelastic, separating the two glass sheets. The interlayer film made of plastic material can comprise one or more layers of a visco-elastic polymer such as polyvinyl butyral (PVB) or an ethylene-vinyl acetate copolymer (EVA). The interlayer film is preferably made of standard PVB or of acoustic PVB (such as single-layer or tri-layer acoustic PVB). Acoustic PVB can comprise three layers: two outer layers of standard PVB and an inner layer of PVB with added plasticizer so as to make it less rigid than the outer layers.
“Ellipse” means a closed planar curve obtained by the intersection of a cone of revolution with a plane, provided that it intersects the axis of rotation of the cone or of the cylinder. The ellipse is a conic section of eccentricity strictly comprised between 0 and 1. The ellipse is also the locus of points whose sum of distances to two fixed points, referred to as foci, is constant.
Referring to
The soundproofing zone 11 has a first thickness h1 of the material. The first thickness h1 varies, based on a coordinate x, along the first length l, proportionally to a value of xn, wherein n is a real number strictly greater than 1, from a minimum thickness h1min until a maximum thickness h1max, the first length l being predetermined so that the minimum thickness h1min is less than or equal to one third of the maximum thickness h1max. The coordinate x is equal to zero when the thickness h1 of the soundproofing zone 11 is equal to the minimum thickness h1min. When the coordinate x is equal to the first length l, the thickness h1 of the soundproofing zone 11 is equal to the maximum thickness h1max. The first length l preferably extends in a main direction 6, the main direction 6 being locally parallel to the main surface 3.
Thus, the glazed unit 2 has higher soundproofing than the soundproofing of a known glazed unit.
Indeed, the document Mironov et al. (Mironov, M. A., 1988, “Propagation of a flexural wave in a plate whose thickness decreases smoothly to zero in a finite interval”, Soviet Physics Acoustics-USSR, 34(3), 318-319) describes that a reduction of the thickness of a thin plate on edges can render the edges non-reflective for bending waves in the material of the plate, when the reduction follows a power law, so that the thickness h of the plate is proportional to xn, wherein n is a real number strictly greater than 1.
The thickness h1 of the glazed unit 2 in the soundproofing zone 11 can be defined by the following formula (1):
wherein ε is a proportionality factor.
The phase velocity cb of the bending waves can be defined based on the thickness h(x) of the glazed unit 2 by the following formula (2):
wherein E is the Young's modulus of the material, p 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 coordinate x and w is the angular velocity of the incident sound wave.
From the phase velocity cb in the soundproofing zone 11, it is possible to calculate a transit time of a bending wave propagating in the soundproofing zone 11. When the thickness h1min tends towards zero thickness, the transit time tends towards infinity. Thus, the incident bending wave is not reflected by an edge of the glazed unit 2, which makes it possible to increase the soundproofing of the glazed unit 2.
The term “acoustic black hole” is used to designate the soundproofing zone 11. The glazed unit 2 comprises at least one acoustic black hole. The glazed unit 2 may comprise a plurality of acoustic black holes, and preferentially an array of acoustic black holes. Referring to
In practice, it is not possible to manufacture a zero thickness h1min. The inventors have observed that the soundproofing effect appears when the first length l is predetermined so that the minimum thickness h1min is less than or equal to one third of the maximum thickness h1. Especially, the first length l is predetermined so that the minimum thickness h1min is less than or equal to one fifth of the maximum thickness h1max. More preferentially, the first length l is predetermined so that the minimum thickness h1min is less than or equal to one tenth of the maximum thickness h1max.
The inventors have also observed that the soundproofing effect appears for n strictly greater than 1, especially strictly greater than 5/3, and preferentially strictly greater than 2. Moreover, n can be strictly less than 100, so as to prevent a reflection at the junction between the central part 4 and the peripheral part 5.
The soundproofing zone 11 may have a size greater than or equal to the first length l in a second main direction, the second main direction being locally perpendicular to the first main direction 6 and locally parallel to the main surface 3.
Referring to
The central part 4 has a thickness of the first material h2, and has the maximum thickness h1max 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 soundproofing zone 11.
Referring to
Referring to
A material forming the peripheral part 5 and a material forming the central part 4 are preferentially the same first material. Thus, the manufacture of the glazed unit 2 is facilitated.
The glazed unit 2 may be a monolithic aircraft glazed unit. Thus, the machining of the soundproofing zone 11 is facilitated, while avoiding reflection of the bending waves at the junction between the central part 4 and the peripheral part 5.
The glazed unit 2 may be formed by an organic glass, in particular by polymethyl methacrylate (PMMA). Thus, the machining of the peripheral part 5 is facilitated with regard to the machining of a soda-lime glass, while allowing the glazed unit 2 to be integrated into a window 12.
Referring to
Referring to
Referring to
The modal movements of the glazed unit 2, for frequencies of an incident acoustic wave greater than a cut-off frequency of the soundproofing zone 11, are concentrated around the borders forming the cut-out 8. From the ratio between the minimum thickness h1min and the maximum thickness h1max, the cut-off frequency of the glazed unit 2 may be small enough to increase the soundproofing of the glazed unit 2 in an audible frequency range.
Referring to
Referring to
Referring to
The dissipator 10 can be made of a material selected from a silicone, a nitrile and a polyurethane. Preferably, the second material has a glass transition temperature Tg less than 50° C., and preferentially less than 30° C. Thus, the second material can dampen the bending waves exhibiting audible frequencies. Preferably, the second material may have a mass density greater than 100 kg/m3, in particular greater than 500 kg/m3, and preferentially greater than 1000 kg/m3. The visco-elastic properties of the known materials can be measured by the methods described herein. The material of the dissipator 10 can have a glass transition temperature comprised between −80° C. and −50° C., inclusive. For example, the material of the dissipator 10 can comprise a methyl vinyl silicone rubber (MVQ) crosslinked by a benzoyl peroxide. The material of the dissipator 10 can also be a porous material. The loss factor of the material can also be adjusted by a tackifying agent, for example a glycerin ester, calcium carbonate or carbon nanotubes. For example, the polyurethane sealant Weberseal PU 40 (registered trademark) of the Weber brand for example has a loss factor η equal to 0.41 and a value of the imaginary part E′ of the Young's modulus equal to 7.2 MPa. For example, the polyurethane sealant Sikaflex PRO-11 FC (registered trademark) of the Sika brand for example has a loss factor η equal to 0.20 and a value of the imaginary part E′ of the Young's modulus equal to 1.2 MPa.
Another aspect of the invention is a glazed element 1. The glazed element 1 comprises at least two glazed units 2. The two glazed units 2 can be superimposed. The glazed element 1 comprises at least one spacer 9 configured to separate the two glazed units 2. Preferably, the glazed element 1 can be an aircraft window 12.
Referring to
The part forming a spacer 9 may be a seal arranged between the two glazed units 2. The part forming a spacer 9 may be arranged on the central part 4 of each of the two glazed units 2, at the border of the peripheral part 5. Thus, the spacer 9 does not obstruct the light transmission through the central part 4.
Referring to
The spacer 9 may comprise the visco-elastic dissipator 10. In this case, a part of the spacer 9 configured to receive a glazed unit 2 is formed by a third material having a first loss factor η1 strictly greater than 0.05, especially strictly greater than 0.10, and preferentially strictly greater than 0.15. Thus, the energy concentrated in a soundproofing 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 glazed unit 2 with respect to known glazed units.
Another aspect of the invention is an aircraft windshield 13, comprising a glazed unit 2 according to one embodiment of the invention. Preferably, the glazed unit 2 has a curved main surface 3. Referring to
Preferably, the windshield 13 comprises a single glazed unit 2.
Alternatively, a glazed unit 2 is suitable for use in vehicles other than an aircraft, such as a motor vehicle, or a train.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2104521 | Apr 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2022/050835 | 4/29/2022 | WO |
