Method for preventing collapse of honeycomb sandwich composite acoustic liner thin-wall skin

Abstract

The invention discloses a method for preventing collapse of a honeycomb sandwich composite acoustic liner thin-wall skin. The method comprises the steps of cementing, paving, sealing, double-layer packaging, co-curing, demolding and forming and the like. Before packaging, the skin is fully sealed by using a sealing material, so that gas in the large-size honeycomb acoustic liner is prevented from escaping; two vacuum bags are used for sequentially packaging the large-size honeycomb acoustic liner and regulating and controlling air pressure, based on the universal gas law pV = nRT, a part of gas is sealed in a honeycomb core grid, the gas is heated to expand in the co-curing process, certain pressure can be given to the skin, the skin is prevented from collapsing due to the fact that the pressure intensity in a tank is too large, and the forming quality of the honeycomb acoustic liner part is guaranteed. The method for preventing collapse of the honeycomb sandwich composite acoustic liner thin-wall skin has the advantages that operation is easy, the period is short, a pressure pad or other high-cost measures are not needed, surface smoothness after co-curing of the skin and a honeycomb can be achieved, and the method has good practical value.

Description

Technical Field

[0001] The invention relates to a method for preventing a thin-wall skin of a honeycomb sandwich composite material sound liner from collapsing. Background Art

[0002] With the development of aviation technology and the enhancement of environmental awareness, people have increasingly stringent requirements on aviation noise. Intake fan noise has become the main source of noise in modern large bypass ratio aircraft engines. Laying acoustic liners in the air intake duct is one of the important ways to reduce noise in aircraft engines. The porous perforated plate honeycomb structure of the acoustic liner can be regarded as several parallel Helmholtz resonance structures, which have a noise reduction effect when its resonance frequency matches the noise frequency. Compared with traditional multi-degree-of-freedom acoustic liners, the acoustic liners made of honeycombs have the advantages of thin thickness, small installation space, and high overall structural strength of the acoustic liner.

[0003] The honeycomb sandwich composite material sound lining is a honeycomb sandwich structure, which consists of a perforated panel, a honeycomb and a back panel. The perforated panel can be bonded with the honeycomb for secondary molding, and the back panel and the components are co-cured. The noise reduction performance of the sound lining is greatly affected by factors such as the aperture size, the hole spacing, the honeycomb core grid, and the honeycomb height. When a large-aperture honeycomb core is used to manufacture the sound lining, the back panel prepreg is easy to sag under the action of the tank pressure, resulting in an uneven surface of the sound lining back panel, which is an urgent problem to be solved. Summary of the invention

[0004] In view of the problems existing in the preparation method of the above-mentioned existing composite honeycomb sandwich sound lining structure, the present invention provides a method for preventing the thin-walled skin of a honeycomb sandwich composite sound lining from collapsing, aiming to solve the problem of prepreg depression caused by the large-sized honeycomb core during the curing process, thereby manufacturing qualified composite honeycomb sound lining structure parts. The specific technical scheme is as follows:

[0005] S1. Bonding: bonding the large-sized honeycomb and the composite material perforated plate from top to bottom to form a large-sized honeycomb sound lining assembly;

[0006] S2, laying: placing the large-sized honeycomb acoustic lining assembly obtained in step S1 with the hole surface facing downward on the forming tool, and laying the composite material prepreg skin with the adhesive film laid on the large-sized honeycomb;

[0007] S3, sealing: pasting a sealing material on the composite material perforated plate of the large-size honeycomb acoustic liner assembly laid in step S2 for sealing, and vacuuming and compacting to seal the pore area on the composite material perforated plate;

[0008] S4, double-layer packaging: the large-sized honeycomb acoustic liner assembly sealed in step S3 is packaged in the first layer using a surface breathable material and a vacuum bag, and is vacuumed for sealing. After the sealing is completed, the large-sized honeycomb acoustic liner assembly packaged in the first layer is packaged in the second layer according to the same packaging steps, and is vacuumed for sealing;

[0009] S5, co-curing: hot-pressing and co-curing the large-size honeycomb acoustic liner assembly and the molding tooling packaged in step S4;

[0010] S6. Demolding and molding: After the co-curing is completed, the laying and molding tools on the components are demoulded to obtain the honeycomb sandwich composite material sound lining parts.

[0011] As a preferred technical solution, the large-sized honeycomb in step S1 is hexagonal in shape, and the core cell size is greater than 4.8 mm and has a certain thickness.

[0012] As a preferred technical solution, the composite material perforated plate in step S1 is obtained by drilling a large number of circular holes in a carbon fiber composite material laminate.

[0013] As a preferred technical solution, in step S2, the surface of the molding tool is cleaned and then paved with a release cloth.

[0014] As a preferred technical solution, the adhesive film in step S2 is located between the composite material prepreg skin and the large-sized honeycomb.

[0015] As a preferred technical solution, the pore area in step S3 is a perforated area on the composite material perforated plate.

[0016] As a preferred technical solution, in step S4, the surface breathable material is located inside the vacuum bag.

[0017] As a preferred technical solution, an isolation membrane is further provided between the surface air-permeable material and the large-size honeycomb acoustic liner assembly in step S4.

[0018] As a preferred technical solution, the co-curing condition in step S5 is: according to the ideal gas state equation pV=nRT, it is required that the pressure in the tank is gradually increased as the temperature rises during the curing process to be equal to the gas pressure sealed in the honeycomb core cell;

[0019] In the ideal gas state equation pV=nRT, p is the pressure, V is the gas volume, n is the amount of gas, R is the molar gas constant, and T is the Kelvin temperature.

[0020] The beneficial effects of the present invention are:

[0021] The present invention discloses a method for preventing the thin-walled skin of a honeycomb sandwich composite material from collapsing. The method comprises laying a skin prepreg on a honeycomb part to which a perforated plate has been glued, and sealing a portion of gas inside the honeycomb core cell based on the universal gas law pV=nRT. The gas will expand due to heat during the co-curing process, and a certain pressure can be applied to the skin to prevent the skin from collapsing. The main advantages of the method for preventing the thin-walled skin of a honeycomb sandwich composite material from collapsing are as follows: (1) the operation is simple. When a suitable back pressure is found, the curing procedure can be adjusted. (2) the original manufacturing cycle of the part is not affected. (3) the surface of the skin and the honeycomb can be made smooth after co-curing without adding a pressure pad or other costly measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A method for preventing the thin-walled skin of a honeycomb sandwich composite material sound liner from collapsing according to the present invention;

[0023] Figure 1 Meaning of the marks: 1. Molding tooling; 2. Sealing material; 3. Composite material perforated plate; 4. Large size honeycomb; 5. Composite material prepreg skin; 6. Isolation membrane; 7. Surface breathable material; 8. Vacuum bag; 9. Surface breathable material; 10. Vacuum bag. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments.

[0025] Example 1

[0026] This embodiment is a method for preventing the thin-walled skin of a honeycomb sandwich composite material acoustic liner from collapsing, and the specific steps are as follows:

[0027] S1, bonding: bonding the large-sized honeycomb 4 and the composite material perforated plate 3 from top to bottom to form a large-sized honeycomb sound lining assembly;

[0028] S2, laying: firstly, clean the surface of the molding tool 1 and lay the release cloth, then place the large-sized honeycomb acoustic liner assembly with the hole surface downward on the molding tool 1, and lay the composite material prepreg skin 5 with the adhesive film laid on the large-sized honeycomb 4;

[0029] S3, sealing: the composite material perforated plate 3 of the large-size honeycomb acoustic lining assembly laid in step S2 is sealed with 2 lines of sealing material, and vacuumed and compacted to seal the pore area of ​​the composite material perforated plate 3 to avoid air leakage during the curing process resulting in insufficient gas expansion pressure;

[0030] S4, double-layer packaging: placing an isolation film 6, a surface air-permeable material 7 and a vacuum bag 8 on the surface of the large-sized honeycomb acoustic lining assembly sealed in step S3 in sequence for the first packaging, and evacuating to seal, and after the sealing is completed, continue to use the surface air-permeable material 9 and the vacuum bag 10 in sequence to perform the second-layer packaging of the large-sized honeycomb acoustic lining assembly that has been packaged in the first layer, and evacuate to seal;

[0031] S5, co-curing: the large-size honeycomb acoustic liner assembly and the tooling packaged in step S4 are sent into the autoclave for co-curing. The co-curing requires the vacuum temperature and pressure requirements throughout the process as shown in Table 1 below;

[0032] Table 1

[0033] Curing temperature / ℃ Curing pressure / MPa 60 0.114 80 0.121 100 0.127 120 0.134 140 0.141 160 0.147 180 0.155

[0034] S6. Demolding and molding: After the co-curing is completed, the material on the component and the molding tool 1 are demolded to obtain the honeycomb sandwich composite material sound lining part.

[0035] In general, the method for preventing the thin-walled skin of a honeycomb sandwich composite material from collapsing is to lay the skin prepreg on the honeycomb part to which the perforated plate has been glued, and based on the universal gas law pV=nRT, a part of the gas is sealed inside the honeycomb core cell, and the gas will expand due to heat during the co-curing process, which can give the skin a certain pressure to prevent the skin from collapsing; the main advantages of the method for preventing the thin-walled skin of a honeycomb sandwich composite material from collapsing are: (1) simple operation, when the appropriate back pressure is found, the curing procedure can be adjusted; (2) no impact on the original manufacturing cycle of the parts; (3) no need to add pressure pads or other costly measures to achieve a smooth surface after the skin and honeycomb are co-cured. The technical problem is effectively solved in a simple way, the scheme is ingeniously conceived, and has good practical value.

[0036] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0037] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preventing the thin-walled skin of a honeycomb sandwich composite material from collapsing, characterized in that: The steps include: S1. Bonding: bonding the large-sized honeycomb and the composite material perforated plate up and down to form a large-sized honeycomb sound lining assembly; S2, laying: placing the large-sized honeycomb acoustic lining assembly obtained in step S1 with the hole surface facing downward on the forming tool, and laying the composite material prepreg skin with the adhesive film laid on the large-sized honeycomb; S3, sealing: pasting a sealing material on the composite material perforated plate of the large-size honeycomb acoustic liner assembly laid in step S2 for sealing, and vacuuming and compacting to seal the pore area on the composite material perforated plate; S4, double-layer packaging: the large-sized honeycomb acoustic liner assembly sealed in step S3 is packaged in the first layer using a surface breathable material and a vacuum bag, and then vacuumed and sealed. After the sealing is completed, the large-sized honeycomb acoustic liner assembly packaged in the first layer is packaged in the second layer according to the same packaging steps, and then vacuumed and sealed; S5, co-curing: hot-pressing and co-curing the large-size honeycomb acoustic liner assembly and the molding tooling packaged in step S4; S6. Demolding and molding: After the co-curing is completed, the laying and molding tools on the components are demoulded to obtain the honeycomb sandwich composite material sound lining parts.

2. The method for preventing the thin-walled skin of a honeycomb sandwich composite material acoustic liner from collapsing according to claim 1, characterized in that: In step S1, the large-sized honeycomb is hexagonal in shape, has a core cell size greater than 4.8 mm and has a certain thickness.

3. The method for preventing the thin-walled skin of a honeycomb sandwich composite material acoustic liner from collapsing according to claim 1, characterized in that: The composite material perforated plate in step S1 is obtained by drilling a large number of circular holes in a carbon fiber composite material laminate.

4. The method for preventing the thin-walled skin of a honeycomb sandwich composite material acoustic liner from collapsing according to claim 1, characterized in that: In step S2, the surface of the molding tool is cleaned and then paved with a release cloth.

5. The method for preventing the thin-walled skin of a honeycomb sandwich composite material acoustic liner from collapsing according to claim 1, characterized in that: In step S2, the adhesive film is located between the composite material prepreg skin and the large-size honeycomb.

6. The method for preventing the thin-walled skin of a honeycomb sandwich composite material acoustic liner from collapsing according to claim 1, characterized in that: The pore area in step S3 is a perforated area on the composite material perforated plate.

7. The method for preventing the thin-walled skin of a honeycomb sandwich composite material acoustic liner from collapsing according to claim 1, characterized in that: In step S4, the surface breathable material is located inside the vacuum bag.

8. The method for preventing the thin-walled skin of a honeycomb sandwich composite material acoustic liner from collapsing according to claim 1, characterized in that: In step S4, an isolation film is also laid between the surface air-permeable material and the large-size honeycomb sound lining assembly.

9. The method for preventing the thin-walled skin of a honeycomb sandwich composite material acoustic liner from collapsing according to claim 1, characterized in that: The co-curing condition in step S5 is: according to the ideal gas state equation pV=nRT, it is required that the pressure in the tank is gradually increased as the temperature rises during the curing process to be equal to the gas pressure sealed in the honeycomb core cell; In the ideal gas state equation pV=nRT, p is the pressure, V is the gas volume, n is the amount of gas, R is the molar gas constant, and T is the Kelvin temperature.

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