RU2297916C1 - Laminated acoustic material - Google Patents

Abstract

FIELD: manufacture of laminated acoustic materials used in aeronautical engineering and automobile industry; manufacture of safety and sound-absorbing shields for automobile roads.

SUBSTANCE: proposed material includes layer made from non-woven needle-piercing material manufactured from polyoxadiazole or polyimidic fibers impregnated with binder of the following composition, mass-%: phenylmethyl polysiloxane, 87.6-95.0; polyorganoelemnto silazane, 3.6-3.9; tetrabromodiphenyl propane, 8.8-9.6 and layer of cellular structure which is made in form of honeycomb panel on base of glass or aramide fabric impregnated with phenolformaldehyde or polyimidic resin. Non-woven material and binder are used at the following ratio, mass-%: non-woven material, 25-52; binder, 48-75. Ratio of thickness of acoustic material layers is equal to 1: (1-2). Material possesses high and stable magnitudes of sound-absorbing coefficients of about 0.8-0.99 in wide frequency range (1.25-6 kHz).

EFFECT: enhanced efficiency.

3 cl, 1 tbl, 4 ex

Description

The invention relates to the field of creating broadband acoustic materials that can be used in the aviation and automotive industries for engine shields and sound absorbing shields of roads to reduce noise on the ground, as well as in other industries.

The problem of noise reduction in the cabin of passenger aircraft and on the runway of aerodromes, as well as near highways, is one of the current challenges.

Known from the prior art, welded metal and fiberglass honeycomb panels have a high sound absorption coefficient equal to 0.8-1.0 in a narrow frequency range, are laborious to manufacture, and also have a relatively low vibration resistance.

In order to expand the frequency range, honeycomb aggregates are combined with various loose-fibrous materials, fabrics, non-woven materials and other porous layers of glass, carbon, aramid and metal fibers (US Pat. No. 4,235,303, No. 3700067).

However, the long life of the loose-fiber structures, especially if they are made of brittle fibers (glass, carbon) in combination with hard metal fibers, can cause their destruction under the influence of vibroacoustic loads, the level of impact of which in the structures under consideration is very high. In addition, loose-fiber structures are available for penetration and condensation of moisture, as well as dust and working fluids, which requires frequent replacement of elements made of such materials.

Known "semi-rigid" materials with high porosity and damping properties (UK patent No. 1268777, US patent No. 2033264, French patent No. 2480741). However, their combination with flexible layers of woven fibers is undesirable for the above reasons.

The closest of the analogues taken as a prototype is a layered acoustic material, including a layer of non-woven needle-punched material made of non-combustible glass or mineral fibers impregnated with a binder, and a layer of fire-resistant foam with open cells based on urethane, nitrile, vinyl or butadiene styrene rubbers (US patent No. 4283457).

The disadvantages of the prototype are the low average value of the sound absorption coefficient - 0.35-0.5 in the frequency range up to 2000 Hz, increased moisture absorption, reduced resistance to aggressive media (engine fluids), reduced breaking load.

An object of the invention is to develop a broadband acoustic material having a consistently high value of sound absorption coefficient in a wide frequency range (sound absorption coefficient α is 0.8-0.99 in the frequency range 1.25-6 kHz), increased strength (breaking load) and retains acoustic properties at a high level (change in sound absorption coefficient α not more than 5-10% compared to the initial value) after exposure to aggressive media, moisture and temperatures elevated to 200 ° C, reduced moisture absorption

The stated technical problem is achieved by the fact that a layered acoustic material is proposed, including a layer made of non-woven needle-punched material impregnated with a binder, and a layer with a cellular structure, while the non-woven material is made of polyoxadiazole or polyimide fibers, the composition is used as a binder, wt. %: phenylmethyl polysiloxane - 87.6-95.0; polyorganoelementosilazane - 3.6-3.9; tetrabromodiphenylpropane - 8.8-9.6; and the layer with a cellular structure is made in the form of a honeycomb panel based on glass or aramid fabric impregnated with phenol-formaldehyde or polyimide resin.

Non-woven material and a binder are used in the following amounts, wt.%: Non-woven material - 25-52, binder - 48-75.

The ratio of the thicknesses of the layers of acoustic material is 1: (1-2).

The authors found that the use of a layer of nonwoven material made of polyoxadiazole or polyimide fibers in combination with the specified binder within the stated limits ensures the production of a material with an increased breaking load, an extended sound absorption band, stable sound absorbing properties after exposure to vibrations, aggressive environments and elevated temperatures (change in sound absorption coefficient 5-10% compared to the initial value). An increase in the strength of sound-absorbing material is achieved by hardening a non-woven material of polyoxadiazole or polyimide fibers with a composition based on phenylmethyl polysiloxane. The extension of the frequency range of sound absorption from 1.25 to 6 kHz is achieved due to the structure that is formed during the curing of the composition, resistance to aggressive media - due to the formation on the pore surface of the film material, which is not wetted by aggressive media.

The use of non-woven material made of polyoxadiazole or polyimide fibers in combination with a composition based on phenylmethyl polysiloxane and in combination with a cellular aggregate provides acoustic material with distributed parameters, which allows not only to expand the frequency range of sound absorption, but also to increase the sound efficiency of sound-absorbing structures based on them, and also ensure the preservation of high values of the coefficient of sound absorption in the specified frequency range.

The ratio of the thicknesses of the layers of acoustic material is determined by the requirements for sound-absorbing structures. In the inventive layered acoustic material, it is most expedient to use the following ratio of layer thicknesses - non-woven material impregnated with a binder: layer with a cellular structure = 1: (1-2).

Examples of implementation.

Example 1

To prepare the binder, 87.6 wt.% Phenylmethylpolysiloxane (TU 2228-352-09201208-96), 3.6 wt.% Polyorganoelementosilazane (TU 6-02-1003-75) and 8.8 wt.% Tetrabromodiphenylpropane (TU 2494 -409-04872688-99). The resulting binder in an amount of 75 wt.% Was impregnated with a web of polyoxadiazole fibers (TU RB 4000312-89) in an amount of 25 wt.%. The impregnated preforms were dried in air, then formed on restrictive stops at T = 180 ° C.

The resulting layer with a thickness of 10 mm was combined with another layer, which is a honeycomb panel based on fiberglass impregnated with phenol-formaldehyde resin, with a ratio of layer thicknesses of 1: 1.

The production of the acoustic material according to examples 2, 3 is analogous to example 1. In example 2, 65 wt.% Of a binder of the following composition was used, wt.%: Phenylmethylpolysiloxane - 90.0, polyorganoelementosilazane - 3.9, tetrabromodiphenylpropane - 9.0, non-woven polyimide material fibers in an amount of 35 wt.% and a honeycomb panel of fiberglass impregnated with a polyimide resin, with a ratio of the thicknesses of the layers of acoustic material 1: 1.5, in example 3 - 48 wt.% a binder of the following composition, wt.%: phenylmethylpolysiloxane - 95.0 , organopolysilazane - 3,7, tetrabromdi phenylpropane - 9.6, nonwoven fabric made of polyoxadiazole fibers in an amount of 52 wt.% and a honeycomb panel made of aramid fabric impregnated with phenol-formaldehyde resin, with a ratio of the thicknesses of the layers of acoustic material 1: 2.

The table shows the properties of the proposed acoustic materials and prototype.

Table. Acoustic material for examples Breaking load, N Density, g / cm ³ Sound absorption coefficient α in the frequency range 1250-6000 Hz Operating temperature, ° С Moisture absorption after 30 days at φ = 98% and t = 20 ° C,% one 610 0.19 0.81-0.87 200 12 2 635 0.28 0.81-0.95 200 fourteen 3 650 0.36 0.81-0.99 200 fifteen Prototype 150-200 1,5 0.35 in the frequency range 250-2000 Hz 150 thirty

The table shows that the proposed acoustic material has a breaking load of 3-4 times more, the sound absorption coefficient is 2 times, the absorption band is 3 times more, and moisture absorption is 2 times less compared to the prototype.

Maintaining a high value of sound absorption coefficient (0.8-0.99) in a wide frequency range indicates that the proposed material has distributed acoustic properties.

The sound efficiency of sound-absorbing structures using the proposed layered acoustic material was 8-9 dB in a wide frequency range of 1000 to 6000 Hz, while in the prototype this figure is 1-2 dB.

The increased breaking load of the proposed material in comparison with the prototype allows the use of the claimed material as part of sound-absorbing structures installed in engine nacelles, in the input devices of power plants and other parts of aircraft engines operating in conditions of increased vibration.

The inventive material retains its acoustic properties even after exposure to aggressive environments (fuels, working fluids such as NGZ, etc.) used in aircraft engines. The sound absorption coefficient of the claimed material after exposure to the working fluid of the UHF for 15 days was 0.8-1 in the frequency range 1.4-5.2 kHz.

The inventive material retains its acoustic properties after exposure to T = 200 ° C for 1000 hours. The sound absorption coefficient was 0.8-1 in the frequency range 1.4-5.5 kHz.

Thus, the inventive layered acoustic material having stable high values of the coefficient of sound absorption, provides high sound efficiency of sound-absorbing structures based on it in a wide frequency range.

Claims (3)

1. A layered acoustic material comprising a layer made of a nonwoven needle-punched material impregnated with a binder and a layer with a cellular structure, characterized in that the non-woven material is made of polyoxadiazole or polyimide fibers, as a binder use a composition composition, wt.%: Phenylmethylpolysiloxane 87 6-95.0; polyorganoelementosilazane 3.6-3.9; tetrabromodiphenylpropane 8.8-9.6, and the layer with a cellular structure is made in the form of a honeycomb panel based on glass or aramid fabric impregnated with phenol-formaldehyde or polyimide resin. 2. Layered acoustic material according to claim 1, characterized in that the non-woven material and the binder are used in the following ratio, wt.%: Nonwoven fabric 25-52 Binder 48-75. 3. The layered acoustic material according to claim 1, characterized in that the ratio of the thicknesses of the layers is 1: (1-2).