A forming method of honeycomb sandwich structure based on excess compensation

Abstract

The present invention provides a forming method of a honeycomb sandwich structure based on excess compensation, which belongs to the technical field of composite material connection. The forming method comprises: providing a cured first skin and a second skin, and two layers of adhesive film, and obtaining the thickness of a single layer of adhesive film; obtaining a target height of a honeycomb core in the honeycomb sandwich structure, and determining a design height of the honeycomb core to be formed based on the target height and the excess compensation amount; providing a honeycomb core and a second packaging component according to the design height of the honeycomb core to be formed, and packaging according to a second packaging method to obtain a package to be cured; placing the package to be cured in an autoclave, and curing according to a curing process to obtain a honeycomb sandwich structure. The present invention compensates for the permanent shrinkage deformation of the honeycomb sandwich structure by compensating the honeycomb core, and the excess compensation amount of the honeycomb core can be predicted by a formula, so as to achieve precise control of the compensation margin of the honeycomb core, so that the geometric accuracy of the honeycomb sandwich structure meets the requirements of industry standards.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material connection, and in particular relates to a forming method of a honeycomb sandwich structure based on excess compensation. Background Art

[0002] The honeycomb sandwich structure is mainly composed of a honeycomb core, a first skin and a second skin which are arranged on both sides of the honeycomb core and connected to the honeycomb core respectively, wherein the honeycomb core is connected to the first skin and the second skin by an adhesive film. The honeycomb sandwich structure has the advantages of light weight, high specific strength and specific stiffness, and is widely used in high-precision satellites, and primary and secondary load-bearing parts such as the leading edge, wing tip, tail, and rudder of aircraft wings. According to the "Aerodynamic Outer Edge Tolerance of Civil Aircraft" (HB 7086-2023), for a class of aircraft with a cruising speed of ≥600km / h, it is stipulated that the concave and convex amount error of the control surface (rudder) is controlled within 0.5mm, and the type value error of the wing leading edge area is within 0.8mm. For commonly used military aircraft in China, the basic tolerance of the type value is (-0.5, +1.0) mm, and the limit deviation is (-0.6, +1.2) mm. For high-precision satellites, the limit deviation of the honeycomb sandwich structure is more demanding. If the dimensional accuracy of sandwich structure components does not meet the standards, it will not only affect the overall aerodynamic shape of the aircraft, but may also seriously affect the safety performance of the entire aircraft.

[0003] The honeycomb sandwich structure forming method provided by the prior art mainly adopts a secondary bonding forming method, specifically, firstly solidifying the upper and lower skins, and then solidifying the solidified upper and lower skins with the adhesive film and the honeycomb core, which has the advantages of good quality of the formed parts and simple process operation. The technical problem of the secondary bonding forming method is that during the secondary bonding forming process of the honeycomb sandwich structure, the honeycomb core will experience a high degree of permanent shrinkage (such as the patent: CN110789145B states that the honeycomb core will shrink during the forming process), which will make it difficult for the formed honeycomb sandwich structure parts to meet the thickness tolerance standards.

[0004] In response to this technical problem, the currently commonly used implementation plan is to appropriately increase the honeycomb core margin when CNC milling the honeycomb core based on work experience, and then carry out a secondary bonding and molding process. There is no specific standard for how much to increase the margin appropriately, and the margin is different for each process. This can easily lead to the honeycomb sandwich structure having difficulty meeting the external dimensions standards and relatively low molding dimensional accuracy after the secondary bonding and molding. Summary of the invention

[0005] The purpose of the present invention is to provide a method for forming a honeycomb sandwich structure based on precise honeycomb core compensation margin, which solves the technical problem of low forming accuracy of the honeycomb sandwich structure in the prior art and can meet the high precision requirements required by aerospace.

[0006] To achieve the above object, the present invention provides a forming method of a honeycomb sandwich structure based on margin compensation, the honeycomb sandwich structure comprising a first skin and a second skin arranged at intervals, and a honeycomb core sandwiched between the first skin and the second skin and having two sides respectively bonded to the first skin and the second skin, the forming method comprising the following steps:

[0007] Step S10, providing a solidified first skin and a second skin, and two layers of adhesive film, and obtaining the thickness of a single layer of adhesive film; Step S20, obtaining a target height of the honeycomb core in the honeycomb sandwich structure, and determining a design height of the honeycomb core to be formed based on the target height and the margin compensation amount, wherein the design height is the sum of the target height and the margin compensation amount, wherein: the calculation formula of the margin compensation amount includes: B=2T m +T x , T x =(H x / H n )×T n ; B is the margin compensation, T m is the thickness of a single layer of film, T x The actual height is H x The predicted deformation of the honeycomb core, H x is the target height of the honeycomb core, H n is the height of the test honeycomb core, T n The actual height is H n The shrinkage deformation corresponding to the honeycomb core of the test honeycomb core T n The method is as follows: providing a test honeycomb core, wherein the height of the test honeycomb core is H n; Under preset creep test parameters, a creep compression test is performed on the test honeycomb core using a creep machine with a plane compression creep assembly; the shrinkage deformation of the test honeycomb core is obtained, and the shrinkage deformation of the test honeycomb core is the creep shrinkage recorded by the creep machine or the shrinkage deformation of the honeycomb core actually measured; step S30, providing a honeycomb core and a second packaging component according to the design height of the honeycomb core to be formed, and packaging the first skin, the second skin, two layers of the adhesive film, the honeycomb core and the second packaging component according to a preset second packaging method to obtain a package to be cured, the second packaging component includes a second vacuum bag, and the preset second packaging method includes: stacking the first skin, a layer of the adhesive film, the honeycomb core, another layer of the adhesive film and the second skin in sequence, and packaging them in the second vacuum bag; step S40, placing the package to be cured in an autoclave, and curing it according to a honeycomb sandwich structure curing process to obtain the honeycomb sandwich structure, and the honeycomb sandwich structure curing process has a corresponding relationship with the preset creep test parameters.

[0008] In a specific embodiment, the honeycomb sandwich structure curing process includes a second curing temperature, a second curing time maintained at the second curing temperature, and a second curing pressure, wherein the second curing pressure is the sum of the pressure in the autoclave and the pressure in the second vacuum bag; the preset creep test parameters include creep temperature, creep time and loading pressure; the honeycomb sandwich structure curing process and the preset creep test parameters have a corresponding relationship, specifically: the creep temperature is the same as the second curing temperature, the creep time is the same as the second curing time, and the pressure generated by the loading pressure applied to the test honeycomb core is the same as the second curing pressure.

[0009] In a specific implementation, the shrinkage deformation of the test honeycomb core is the creep shrinkage recorded by the creep machine.

[0010] In a specific embodiment, the second packaging component also includes a second breathable felt, a third isolation membrane, a fourth isolation membrane, a second tooling plate and a second sealing strip, and the preset second packaging method is specifically: from bottom to top, the second tooling plate, the third isolation membrane, the first skin, a layer of adhesive film, the honeycomb core, another layer of adhesive film, the second skin, the fourth isolation membrane and the second breathable felt are laid in sequence, and then packaged with a second vacuum bag and a second sealing strip.

[0011] In a specific embodiment, the second curing temperature is 120° C. to 180° C., the pressure in the autoclave is 0.2 MPa to 0.5 MPa, the pressure in the second vacuum bag is 0.1 MPa, and the second curing time is 2 h to 5 h.

[0012] In a specific embodiment, the first skin and the second skin are both cured by the following method, which includes: providing a first packaging component and a carbon fiber reinforced resin-based prepreg; packaging the first packaging component and the carbon fiber reinforced resin-based prepreg according to a preset first packaging method to obtain a skin package; placing the skin package in an autoclave, and curing it according to a skin curing process to obtain the first skin or the second skin.

[0013] In a specific embodiment, the first packaging component includes a first vacuum bag, a first sealing strip, a first tooling board, a first isolation film, a second isolation film and a first breathable felt, and the first packaging method is specifically: from bottom to top, the first tooling board, the first isolation film, the carbon fiber reinforced resin-based prepreg, the second isolation film and the first breathable felt are laid in sequence, and then packaged with the first vacuum bag and the first sealing strip.

[0014] In a specific embodiment, the carbon fiber reinforced resin-based prepreg is composed of 6 to 18 layers of preimpregnated fiber materials stacked together, and two adjacent layers of preimpregnated fiber materials are laid in an orthogonal cross-laying manner.

[0015] In a specific embodiment, the skin curing process includes a first curing temperature, a first curing time maintained at the first curing temperature, and a first curing pressure, wherein the first curing pressure is the sum of the pressure in the autoclave and the pressure in the first vacuum bag, the first curing temperature is the same as the second curing temperature, the first curing time is the same as the second curing time, the pressure in the first vacuum bag is the same as the pressure in the second vacuum bag, and the pressure in the autoclave in the skin curing process is greater than the pressure in the autoclave in the honeycomb sandwich structure curing process.

[0016] In a specific embodiment, the honeycomb core is an aramid honeycomb core formed by a composite of aramid paper and phenolic resin.

[0017] The beneficial effects of the present invention include at least:

[0018] The forming method of the honeycomb sandwich structure based on the surplus compensation provided by the present invention comprises: step S10, providing a solidified first skin and a second skin, and two layers of adhesive film, and obtaining the thickness of the single layer of adhesive film; step S20, obtaining the target height of the honeycomb core in the honeycomb sandwich structure, and determining the design height of the honeycomb core to be formed based on the target height and the surplus compensation amount, wherein the design height is the sum of the target height and the surplus compensation amount; step S30, providing a honeycomb core and a second packaging component according to the design height of the honeycomb core to be formed, and packaging the first skin, the second skin, the two layers of adhesive film, the honeycomb core and the first packaging component according to a preset second packaging method. The second packaging assembly is packaged to obtain a package to be cured, and the preset second packaging method includes: the first skin, a layer of the adhesive film, the honeycomb core, another layer of the adhesive film and the second skin are stacked in sequence; step S40, placing the package to be cured in an autoclave, and curing it according to the honeycomb sandwich structure curing process to obtain the honeycomb sandwich structure, and the honeycomb sandwich structure curing process has a corresponding relationship with the preset creep test parameters; the present invention compensates for the permanent shrinkage deformation of the honeycomb sandwich structure during curing molding in the autoclave by compensating the height margin of the honeycomb core, and the margin compensation amount (height margin) of the honeycomb core can be calculated by the formula B=2T m +(H x / H n )×T n Prediction can be performed to achieve precise control of the honeycomb core excess compensation amount, thereby ensuring that the formed honeycomb sandwich structure has high precision and can meet the requirements of aerospace. At the same time, this method is applicable to honeycomb sandwich structures of different thicknesses and has the advantages of saving manpower and material resources.

[0019] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic flow chart of steps of a forming method of a honeycomb sandwich structure based on margin compensation provided in one embodiment of the present invention;

[0021] Figure 2 A schematic diagram of laying out the skin package provided by the present invention;

[0022] Figure 3 for Figure 1 The schematic diagram of laying out the package to be cured provided in step S30 is shown;

[0023] Figure 4 for Figure 1 The process parameter diagram of the honeycomb sandwich structure curing process in step S40 is shown;

[0024] Figure 5 The real-time data of creep deformation of 10mm honeycomb core recorded by the creep machine in Experiment 1;

[0025] Figure 6 This is a physical picture of the first honeycomb sandwich structure obtained by molding in Experiment 2;

[0026] Figure 7 This is a physical picture of the middle part of the sample selected in Experiment 2;

[0027] Figure 8 The actual pictures of the honeycomb core and honeycomb sandwich structure obtained from Experiments 1 to 3, where: Figure 8 a in the figure is the actual picture of the honeycomb core obtained under the process conditions of Experiment 1. Figure 8 Figure b is a physical picture of the middle part of the sample of the first honeycomb sandwich structure obtained by molding in Experiment 2. Figure 8 Figure c is a physical picture of the middle part sample of the second honeycomb sandwich structure obtained by molding in Experiment 3. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be defined and covered by various different implementations according to the claims.

[0029] In view of the high permanent shrinkage phenomenon that occurs during the secondary bonding of honeycomb sandwich structures, the existing technology currently mainly determines the honeycomb core compensation margin based on work experience, and does not study the amount of honeycomb core compensation margin, resulting in the difficulty in meeting the external dimensions of the formed honeycomb sandwich structure and relatively low molding dimensional accuracy, which affects its application in aircraft. The present invention uses a creep machine with a planar compression creep assembly to conduct a creep test on the honeycomb core and uses an autoclave to conduct a curing molding test on the honeycomb sandwich structure, creatively discovering the relationship between the shrinkage deformation amount of the honeycomb sandwich structure during curing molding and the creep amount of the honeycomb core and the adhesive film, thereby being able to predict the margin compensation margin of the honeycomb sandwich structure with honeycomb cores of different thicknesses, and achieving precise control of the honeycomb core compensation margin, thereby ensuring that the formed honeycomb sandwich structure has high precision and can meet the requirements of aerospace.

[0030] It should be noted that, when introducing the molding method below, the curing of the first skin and the second skin can be understood as a primary bonding process, and the curing of the honeycomb sandwich structure can be understood as a secondary bonding process.

[0031] See also Figures 1 to 4The present invention provides a forming method of a honeycomb sandwich structure based on excess compensation, wherein the honeycomb sandwich structure includes a first skin and a second skin that are spaced apart, and a honeycomb core that is sandwiched between the first skin and the second skin and is glued to the first skin and the second skin on both sides.

[0032] Preferably, the honeycomb core is an aramid honeycomb core formed by a composite of aramid paper and phenolic resin.

[0033] In the present invention, the density of the honeycomb core is 48kg / m 3 .

[0034] Preferably, the first skin and the second skin are made of carbon fiber reinforced resin-based composite materials.

[0035] It should be noted that, in the present invention, the first skin and the second skin are the same, and a qualifier is added only to distinguish the two skins. Specifically, Figure 3 In the perspective shown, the first skin refers to the skin located on the lower side of the honeycomb core, and the second skin refers to the skin located on the upper side of the honeycomb core.

[0036] In the present invention, the first skin and the honeycomb core, and the second skin and the honeycomb core are connected via adhesive films, and the adhesive films are epoxy resin adhesive films.

[0037] The molding method comprises the following steps:

[0038] Step S10: providing a cured first skin 10, a second skin 20, and two layers of adhesive film 30, and obtaining the thickness of a single layer of adhesive film.

[0039] Preferably, the first skin and the second skin are both cured by the following method, including:

[0040] Step (1): providing a first packaging component 50 and a carbon fiber reinforced resin-based prepreg 10A.

[0041] Preferably, the first packaging assembly 50 includes a first vacuum bag 51 , a first sealing strip 52 , a first tooling plate 53 , a first isolation film 54 , a second isolation film 55 and a first air-permeable felt 56 .

[0042] In the present invention, the carbon fiber reinforced resin-based prepreg 10A is composed of 6 to 18 layers of preimpregnated fiber materials stacked together, and two adjacent layers of preimpregnated fiber materials are laid in an orthogonal cross-laying manner.

[0043] Step (2): encapsulating the first packaging component 50 and the carbon fiber reinforced resin-based prepreg 10A according to a preset first packaging method to obtain a skin package.

[0044] Please refer to Figure 2 The first packaging method is specifically as follows: from bottom to top, the first tooling plate 53, the first isolation film 54, the carbon fiber reinforced resin-based prepreg 10A, the second isolation film 55 and the first breathable felt 56 are laid out in sequence, and then packaged with a first vacuum bag 51 and a first sealing strip 52.

[0045] In the present invention, the first isolation film and the second isolation film have the function of making it easy to peel the formed skin off from the packaging component.

[0046] Step (3), placing the skin package in an autoclave, and curing it according to a skin curing process to obtain the first skin or the second skin.

[0047] In the present invention, before starting the autoclave procedure, the skin package is also subjected to a vacuum treatment (-0.1 MPa).

[0048] The skin curing process includes a first curing temperature, a first curing time maintained at the first curing temperature, and a first curing pressure, wherein the first curing pressure is the sum of the pressure in the autoclave and the pressure in the first vacuum bag, wherein the first curing temperature is 120°C to 180°C, the pressure in the autoclave is 0.2MPa to 0.6MPa, the pressure in the first vacuum bag is 0.1MPa, and the first curing time is 2h to 5h.

[0049] It should be noted that the curing time refers to the time maintained at the curing temperature, and does not include the heating time and the cooling time.

[0050] In the present invention, the skin curing process is specifically as follows: starting from room temperature, the temperature is raised to 180°C at a rate of 5°C / min, and then the temperature is maintained at 180°C for 3 hours. After the end of the heat preservation (the time point is approximately: 30+180=210min), the temperature gradually decreases until it reaches room temperature; when the temperature in the tank reaches 180°C, the pressurization program is started, and the pressure in the tank is increased from 0MPa to 0.5MPa and maintained for 3 hours; after the pressure maintenance is completed, when the temperature in the tank drops to 60°C, the pressure in the tank is unloaded from 0.5MPa to 0MPa; the vacuum bag pressure of 0.1MPa is applied from the beginning of the experiment, maintained until the end of the pressure maintenance stage, and then unloaded to 0MPa.

[0051] It should be noted that the process parameters of the skin curing process need to be determined based on the curing process of the secondary bonding, that is, the honeycomb sandwich structure curing process below. The relationship between the two will be elaborated in detail below and will not be repeated here.

[0052] Step S20, obtaining a target height of the honeycomb core in the honeycomb sandwich structure, and determining a design height of the honeycomb core to be formed based on the target height and the margin compensation amount, wherein the design height is the sum of the target height and the margin compensation amount.

[0053] In the present invention, the permanent shrinkage deformation of the honeycomb sandwich structure during secondary bonding is compensated by increasing the height of the honeycomb core raw material.

[0054] in:

[0055] The calculation formula for the design height of the honeycomb core is: Y=X+B, where Y is the design height of the honeycomb core, X is the target height of the honeycomb core, and B is the margin compensation amount.

[0056] The calculation formula of the margin compensation includes: B=2T m +T x , T x =(H x / H n )×T n , B is the margin compensation, T m is the thickness of a single layer of film, T x The actual height is H x The predicted deformation of the honeycomb core, H x is the target height of the honeycomb core, H n is the height of the test honeycomb core, T n The actual height is H n The shrinkage deformation corresponding to the honeycomb core.

[0057] In the present invention, the target height of the honeycomb core can be understood as the required height of the finished honeycomb sandwich structure, that is, the measured height of the finished product proposed by the customer; the actual height of the honeycomb core can be understood as the height of the raw material of the honeycomb core; and the residual compensation amount is used to compensate for the corresponding shrinkage deformation during the curing of the honeycomb sandwich structure, so that the height of the molded honeycomb core is the same as the designed height, thereby ensuring that the molded honeycomb sandwich structure meets the corresponding industry standards.

[0058] Preferably, the shrinkage deformation T corresponding to the test honeycomb core n Obtain it in the following ways, including:

[0059] Step (1), providing a test honeycomb core, wherein the height of the test honeycomb core is H n .

[0060] Step (2): Under preset creep test parameters, a creep machine with a planar compression creep assembly is used to perform a creep compression test on the test honeycomb core.

[0061] In the present invention, the creep machine with a planar compression creep assembly is a creep machine protected by a patent previously applied for by the inventor, the publication number of the patent application is CN118746482A, and the name of the patent application is: A planar compression creep assembly based on a creep machine providing linear tension.

[0062] Step (3), obtaining the shrinkage deformation of the test honeycomb core, wherein the shrinkage deformation of the test honeycomb core is the creep shrinkage recorded by the creep machine or the shrinkage deformation of the honeycomb core obtained by actual measurement.

[0063] In the present invention, the shrinkage deformation of the test honeycomb core is the creep shrinkage recorded by the creep machine.

[0064] It is understandable that the creep amount of the test honeycomb core is different under different creep test parameters. In order to ensure the accuracy of the data of the residual compensation amount, the preset creep test parameters need to be determined based on the curing process of the secondary bonding, that is, the honeycomb sandwich structure curing process mentioned below. The relationship between the two will be explained in detail below and will not be repeated here.

[0065] Step S30, providing a honeycomb core and a second packaging component according to the design height of the honeycomb core to be formed, and packaging the first skin, the second skin, two layers of the adhesive film, the honeycomb core and the second packaging component according to a preset second packaging method to obtain a package to be cured, the second packaging component includes a second vacuum bag, and the preset second packaging method includes: stacking the first skin, a layer of the adhesive film, the honeycomb core, another layer of the adhesive film and the second skin in sequence, and packaging them in the second vacuum bag.

[0066] Please refer to Figure 3 Preferably, the second packaging component 60 includes a second vacuum bag 61, a second sealing strip 62, a second tooling plate 63, a third isolation film 64, a fourth isolation film 65 and a second breathable felt 66, and the preset second packaging method is specifically: from bottom to top, the second tooling plate 63, the third isolation film 64, the first skin 10, a layer of adhesive film 30, the honeycomb core 40, another layer of adhesive film 30, the second skin 20, the fourth isolation film 65 and the second breathable felt 66 are laid in sequence, and then packaged with the second vacuum bag 61 and the second sealing strip 62.

[0067] Step S40, placing the package to be cured in an autoclave, and curing it according to a honeycomb sandwich structure curing process to obtain the honeycomb sandwich structure, wherein the honeycomb sandwich structure curing process has a corresponding relationship with the preset creep test parameters.

[0068] Preferably, the honeycomb sandwich structure curing process includes a second curing temperature, a second curing time maintained at the second curing temperature, and a second curing pressure, wherein the second curing pressure is the sum of the pressure in the autoclave and the pressure in the second vacuum bag; the preset creep test parameters include creep temperature, creep time and loading pressure; the honeycomb sandwich structure curing process and the preset creep test parameters have a corresponding relationship, specifically: the creep temperature is the same as the second curing temperature, the creep time is the same as the second curing time, and the pressure generated by the loading pressure applied to the test honeycomb core is the same as the second curing pressure.

[0069] For ease of understanding, for example, in step S40, if the curing temperature is 180°C, the pressure in the autoclave is 0.4MPa, the vacuum bag pressure is 0.1MPa, and the curing time is 3h, then the creep temperature in the preset creep test parameters is 180°C, the creep time is 3h, and the loading pressure is 0.5MPa×S, where S is the nominal area of ​​the upper surface / lower surface of the test honeycomb core. In the present invention, the honeycomb core is a rectangular parallelepiped, and S=the length of the honeycomb core×the width of the honeycomb core.

[0070] Preferably, the second curing temperature is 120° C. to 180° C., the pressure in the autoclave is 0.2 MPa to 0.5 MPa, the pressure in the second vacuum bag is 0.1 MPa, and the second curing time is 2 h to 5 h.

[0071] Please refer to Figure 4 In the present invention, the curing process of the honeycomb sandwich structure is specifically as follows: starting from room temperature, the temperature is raised to 180°C at a rate of 5°C / min, and then the temperature is maintained at 180°C for 3 hours. After the end of the heat preservation (the time point is approximately: 30+180=210min), the temperature gradually decreases until it reaches room temperature; when the temperature in the tank reaches 180°C, the pressurization program is started, and the pressure in the tank is increased from 0MPa to 0.4MPa and maintained for 3 hours; after the pressure maintenance is completed, when the temperature in the tank drops to 60°C, the pressure in the tank is unloaded from 0.4MPa to 0MPa; the vacuum bag pressure of 0.1MPa is applied from the beginning of the experiment, maintained until the end of the pressure maintenance stage, and then unloaded to 0MPa.

[0072] In the present invention, the skin curing process is determined based on the honeycomb sandwich structure curing process. Specifically, the first curing temperature is the same as the second curing temperature, the first curing time is the same as the second curing time, the pressure inside the first vacuum bag is the same as the pressure inside the second vacuum bag, and the pressure inside the autoclave in the skin curing process is greater than the pressure of the autoclave in the honeycomb sandwich structure curing process. This is to ensure that the first skin and the second skin are fully cured and prevent the impact of post-curing.

[0073] It can be understood that in step S40, since the first skin and the second skin have been fully cured, the first skin and the second skin are fully cured and can be regarded as rigid bodies in this curing step, and no deformation occurs.

[0074] Example 1

[0075] The experiment verified that when the autoclave was used for secondary bonding, the shrinkage of the honeycomb sandwich structure was T=2T. m +(H x / H n )×T n , where T m is the thickness of a single layer of film, H x is the target height of the honeycomb core, H n is the height of the test honeycomb core, T n The actual height is H n The creep amount corresponding to the honeycomb core.

[0076] Experiment 1: Out-of-plane compression creep test of 10mm thick honeycomb core

[0077] Experimental materials: honeycomb core, that is, experimental honeycomb core.

[0078] The honeycomb core is an aramid honeycomb core formed by a composite of aramid paper and phenolic resin, with a density of 48kg / m 3 , the size is: length × width × height = 35mm × 35mm × 10mm, that is, H n =10mm.

[0079] Experimental apparatus: Creep machine with a planar compression creep assembly.

[0080] Experimental preparation: Use a vernier caliper with an accuracy of 0.01 mm to measure the five height points of the honeycomb core before the molding experiment, which are: 10.00, 10.02, 10.02, 10.02, 10.00, and the average height of the honeycomb core before the experiment is L1 = 10.012 mm.

[0081] Experimental conditions: creep temperature 180°C, applied pressure F=P×S=0.5MPa×35mm×35mm=612.5N, holding time 3h.

[0082] Experimental results: After the experiment, the five heights of the honeycomb core were measured to be 9.97, 9.98, 9.97, 9.98, and 9.97, respectively. The average height of the honeycomb core after the experiment was L2 = 9.974 mm. Therefore, the total shrinkage deformation of the honeycomb core = T 蜂窝 =L1-L2=0.038mm. The creep shrinkage recorded in the creep machine is T n =0.0375mm, such as Figure 5As shown in Table 1 below. As can be seen from Table 1, the shrinkage deformation T of the honeycomb core measured before and after the creep machine test 蜂窝 and creep experimental data deformation T n The deformation T of the 10mm thick honeycomb core during the forming process can be obtained. 蜂窝 =T n =0.0375mm.

[0083] Experiment 2: Secondary bonding experiment of the first honeycomb sandwich structure with a honeycomb core height of 10 mm

[0084] Experimental materials: the cured first skin and second skin, two layers of adhesive film, and the first honeycomb core, wherein the adhesive film is GXA120 toughened epoxy adhesive film with a thickness of 0.15 mm; the honeycomb core is an aramid honeycomb core formed by a composite of aramid paper and phenolic resin with a density of 48 kg / m 3 , size: length × width × height = 200mm × 200mm × 10mm, that is, H n =10mm.

[0085] The curing method of the first skin and the second skin is described above and will not be repeated here. The specific process parameters are: starting from room temperature, the temperature is raised to 180°C at a rate of 5°C / min, and then the temperature is maintained at 180°C for 3 hours. After the pressure holding is completed (the time point is approximately: 30+180=210min), the temperature gradually decreases to room temperature; when the temperature in the tank reaches 180°C, the pressurization program is started, and the pressure in the tank is increased from 0MPa to 0.5MPa and maintained for 3 hours. After the pressure holding is completed, when the temperature in the tank drops to 60°C, the pressure in the tank is unloaded from 0.5MPa to 0MPa; the vacuum bag pressure of 0.1MPa is applied from the beginning of the experiment, maintained until the end of the pressure holding stage, and then unloaded to 0MPa.

[0086] Experimental equipment: Autoclave.

[0087] Experimental preparation: Use a vernier caliper with an accuracy of 0.01 mm to measure the five height points of the first honeycomb sandwich structure before the molding experiment. The height is the sum of the heights of the first skin, the second skin, the two layers of adhesive film and the first honeycomb core.

[0088] Specifically, the five heights measured for the first honeycomb sandwich structure are 12.30, 12.34, 12.33, 12.30 and 12.30 respectively, and the average height L3 = 12.314 mm.

[0089] Experimental conditions: curing temperature 180℃, tank pressure 0.4MPa, vacuum bag pressure 0.1MPa, maintained at 180℃ for 3h.

[0090] Experimental results: The middle part of the sample (35mm×35mm) was selected, and the height of the middle part of the sample was measured. A total of 5 height points were measured, namely 11.97, 11.96, 11.96, 12.00, and 11.99. The average height L4=11.976mm.

[0091] In the present invention, the purpose of selecting the middle part of the sample to obtain the height value is to keep consistent with the size of the honeycomb core in Experiment 1, while also avoiding the deformation of the side of the honeycomb sandwich structure and the influence on its height accuracy.

[0092] The first honeycomb sandwich structure obtained by experiment 2 is shown in the figure Figure 6 As shown in the figure, the middle part of the sample is selected as follows Figure 7 shown.

[0093] Experiment 3: Secondary bonding experiment of the second honeycomb sandwich structure with a honeycomb core height of 20 mm

[0094] Experimental materials: the cured first skin and second skin, two layers of adhesive film, and the second honeycomb core, wherein the adhesive film is a GXA120 toughened epoxy adhesive film with a thickness of 0.15 mm; the honeycomb core is an aramid honeycomb core formed by a composite of aramid paper and phenolic resin with a density of 48 kg / m 3 , size: length × width × height = 200mm × 200mm × 20mm, that is, H n =20mm.

[0095] The curing method of the first skin and the second skin is described above and will not be repeated here. The specific process parameters are: starting from room temperature, the temperature is raised to 180°C at a rate of 5°C / min, and then the temperature is maintained at 180°C for 3 hours. After the pressure holding is completed (the time point is approximately: 30+180=210min), the temperature gradually decreases to room temperature; when the temperature in the tank reaches 180°C, the pressurization program is started, and the pressure in the tank is increased from 0MPa to 0.5MPa and maintained for 3 hours. After the pressure holding is completed, when the temperature in the tank drops to 60°C, the pressure in the tank is unloaded from 0.5MPa to 0MPa; the vacuum bag pressure of 0.1MPa is applied from the beginning of the experiment, maintained until the end of the pressure holding stage, and then unloaded to 0MPa.

[0096] Experimental equipment: Autoclave.

[0097] Experimental preparation: Use a vernier caliper with an accuracy of 0.01 mm to measure the five height points of the second honeycomb sandwich structure before the molding experiment. The height is the sum of the heights of the first skin, the second skin, the two layers of film and the second honeycomb core.

[0098] Specifically, the five heights measured of the second honeycomb sandwich structure are 22.45, 22.50, 22.50, 22.46 and 22.50 respectively, and the average height L5=22.482 mm.

[0099] Experimental conditions: curing temperature 180℃, tank pressure 0.4MPa, vacuum bag pressure 0.1MPa, maintained at 180℃ for 3h.

[0100] Experimental results: The middle part of the sample (35mm×35mm) was selected and the height of the middle part of the sample was measured. A total of 5 height points were measured, namely 22.13, 22.12, 22.09, 22.09 and 22.11, and the average height L6=22.108mm.

[0101] In the present invention, the purpose of selecting the middle part of the sample to obtain the height value is to keep consistent with the size of the honeycomb core in Experiment 1, while also avoiding the deformation of the side of the honeycomb sandwich structure and the influence on its height accuracy.

[0102] The structure of the honeycomb core obtained in Experiment 1 is as follows Figure 8 As shown in a in FIG. 1 , the middle part sample of the first honeycomb sandwich structure obtained by the second experiment is as follows Figure 8 As shown in b, the middle part of the sample of the second honeycomb sandwich structure obtained by the third experiment is as follows Figure 8 As shown in c.

[0103] The height data of Experiments 1, 2, and 3 are summarized in Table 1.

[0104]

[0105] It should be noted that the calculation method of the coefficient of variation in Table 1 is: first calculate the mean value of the sample group, then calculate the sample standard deviation based on the sample standard deviation calculation formula, and then calculate the coefficient of variation based on the mean value and the sample standard deviation, where the coefficient of variation = mean value / sample standard deviation × 100%.

[0106] Based on the experiment 1, the shrinkage deformation T of the honeycomb core with a thickness of 10 mm is 蜂窝 =0.0375mm, it can be predicted that the shrinkage of the 10mm honeycomb sandwich structure is T=0.338≈2T 胶膜 +T 蜂窝 =2×0.15+0.0375=0.33375mm, with a prediction accuracy of up to 99.9%; the shrinkage of the 20mm honeycomb sandwich structure can be predicted to be T=0.374≈2 T 胶膜 +20 / 10×T 蜂窝 =2×0.15+20 / 10×0.0375=0.375mm, with a prediction accuracy of up to 99.7%.

[0107] The present invention uses the shrinkage of the honeycomb sandwich structure as the excess compensation amount of the honeycomb core, and the shrinkage of the honeycomb sandwich structure can be predicted based on the shrinkage deformation of the honeycomb core with high prediction accuracy, thus ensuring that the prepared honeycomb sandwich structure can meet industry standards.

[0108] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A forming method of a honeycomb sandwich structure based on excess compensation, the honeycomb sandwich structure comprising a first skin and a second skin arranged at intervals, and a honeycomb core sandwiched between the first skin and the second skin and having two sides respectively bonded to the first skin and the second skin, characterized in that: The molding method comprises the following steps: Step S10, providing a solidified first skin and a second skin, and two layers of adhesive film, and obtaining the thickness of a single layer of adhesive film; Step S20, obtaining a target height of the honeycomb core in the honeycomb sandwich structure, and determining a design height of the honeycomb core to be formed based on the target height and the margin compensation amount, wherein: The calculation formula of the margin compensation includes: B = 2T m +T x , T x =(H x / H n )×T n ; B is the margin compensation amount, T m is the thickness of a single layer of film, T x The actual height is H x The predicted deformation of the honeycomb core, H x is the target height of the honeycomb core, H n is the height of the test honeycomb core, T n The actual height is H n The shrinkage deformation corresponding to the honeycomb core; The shrinkage deformation T corresponding to the test honeycomb core n Obtain it in the following ways, including: Provide a test honeycomb core, the height of the test honeycomb core is H n ; Under preset creep test parameters, using a creep machine with a planar compression creep assembly to perform a creep compression test on the test honeycomb core; Acquiring the shrinkage deformation of the test honeycomb core, where the shrinkage deformation of the test honeycomb core is the creep shrinkage recorded by the creep machine or the shrinkage deformation of the honeycomb core actually measured; Step S30, providing a honeycomb core and a second packaging component according to the design height of the honeycomb core to be formed, and packaging the first skin, the second skin, two layers of the adhesive film, the honeycomb core and the second packaging component according to a preset second packaging method to obtain a package to be cured, wherein the second packaging component includes a second vacuum bag, and the preset second packaging method includes: stacking the first skin, a layer of the adhesive film, the honeycomb core, another layer of the adhesive film and the second skin in sequence, and packaging them in the second vacuum bag; Step S40, placing the package to be cured in an autoclave, and curing it according to a honeycomb sandwich structure curing process to obtain the honeycomb sandwich structure, wherein the honeycomb sandwich structure curing process has a corresponding relationship with the preset creep test parameters; The honeycomb sandwich structure curing process includes a second curing temperature, a second curing time maintained at the second curing temperature, and a second curing pressure, wherein the second curing pressure is the sum of the pressure in the autoclave and the pressure in the second vacuum bag; the preset creep test parameters include creep temperature, creep time and loading pressure; the honeycomb sandwich structure curing process and the preset creep test parameters have a corresponding relationship, specifically: the creep temperature is the same as the second curing temperature, the creep time is the same as the second curing time, and the pressure generated by the loading pressure applied to the test honeycomb core is the same as the second curing pressure.

2. The forming method of the honeycomb sandwich structure based on excess compensation according to claim 1, characterized in that: The second packaging component also includes a second breathable felt, a third isolation membrane, a fourth isolation membrane, a second tooling plate and a second sealing strip. The preset second packaging method is specifically: from bottom to top, the second tooling plate, the third isolation membrane, the first skin, a layer of adhesive film, the honeycomb core, another layer of adhesive film, the second skin, the fourth isolation membrane and the second breathable felt are laid in sequence, and then packaged with a second vacuum bag and a second sealing strip.

3. The forming method of the honeycomb sandwich structure based on excess compensation according to claim 2, characterized in that: The second curing temperature is 120° C. to 180° C., the pressure in the autoclave is 0.2 MPa to 0.5 MPa, the pressure in the second vacuum bag is 0.1 MPa, and the second curing time is 2 h to 5 h.

4. The forming method of the honeycomb sandwich structure based on excess compensation according to claim 3 is characterized in that: The first skin and the second skin are both cured by the following method, including: Providing a first packaging component and a carbon fiber reinforced resin-based prepreg; The first packaging component and the carbon fiber reinforced resin-based prepreg are packaged according to a preset first packaging method to obtain a skin package; The skin package is placed in an autoclave and cured according to a skin curing process to obtain the first skin or the second skin.

5. The forming method of the honeycomb sandwich structure based on excess compensation according to claim 4 is characterized in that: The first packaging component includes a first vacuum bag, a first sealing strip, a first tooling board, a first isolation film, a second isolation film and a first breathable felt. The first packaging method is specifically: from bottom to top, the first tooling board, the first isolation film, the carbon fiber reinforced resin-based prepreg, the second isolation film and the first breathable felt are laid in sequence, and then packaged with the first vacuum bag and the first sealing strip.

6. The forming method of the honeycomb sandwich structure based on excess compensation according to claim 5, characterized in that: The carbon fiber reinforced resin-based prepreg is composed of 6 to 18 layers of preimpregnated fiber materials stacked together, and two adjacent layers of preimpregnated fiber materials are laid in an orthogonal cross-laying manner.

7. The forming method of a honeycomb sandwich structure based on excess compensation according to claim 4, characterized in that: The skin curing process includes a first curing temperature, a first curing time maintained at the first curing temperature, and a first curing pressure, wherein the first curing pressure is the sum of the pressure in the autoclave and the pressure in the first vacuum bag, wherein the first curing temperature is the same as the second curing temperature, the first curing time is the same as the second curing time, the pressure in the first vacuum bag is the same as the pressure in the second vacuum bag, and the pressure in the autoclave in the skin curing process is greater than the pressure in the autoclave in the honeycomb sandwich structure curing process.

8. The forming method of a honeycomb sandwich structure based on excess compensation according to claim 1, characterized in that: The honeycomb core is an aramid honeycomb core formed by compounding aramid paper and phenolic resin.

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