A uniform impregnation method for large-size irregularly shaped thermal insulation material components

Abstract

The application provides a uniform composite impregnation method for large-size special-shaped thermal insulation material components, and belongs to the technical field of thermal insulation materials. The method adds several in-out glue ports at the set position of a large-size component forming mold to obtain an improved forming mold for gradient glue injection, places a fiber preform in the improved forming mold, adopts a high gradient pressure glue injection mode to inject a sol precursor, sequentially uses the in-out glue ports from low to high for glue injection and glue discharge in sequence, and pressurizes and impregnates the fiber preform in the improved forming mold, increases the glue discharge amount and glue injection cycle number of the large-size component forming mold, and obtains a fiber preform component impregnated and compounded with the sol precursor. The method has no complex process, is simple and effective to operate, can greatly reduce the non-uniform composite impregnation condition, reduces the production cost, and improves the component yield.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation material technology, and in particular relates to a method for uniform composite impregnation of large-sized irregularly shaped thermal insulation material components. Background Technology

[0002] When high-speed aircraft operate at high speeds or repeatedly traverse the atmosphere, they are subjected to severe atmospheric and thermal loads. Their surfaces experience strong impacts and friction from the atmosphere, leading to a rapid increase in heat. To ensure the integrity of the aircraft's external structure and the stable operation of its internal electronic components, large-sized, irregularly shaped external thermal protection materials that combine heat resistance, insulation, and load-bearing capacity are indispensable. The silica-based sol precursor is an aqueous solution, while the organic wetting agent used in the material preform preparation process presents a degree of incompatibility. Furthermore, due to the large size (and height) of the thermal protection components in the cabin sections, traditional injection molding methods are prone to poor impregnation of the thermal insulation material when handling large components.

[0003] Therefore, it is essential to optimize the composite impregnation method for large-sized irregularly shaped thermal insulation material components to improve the uniformity of impregnation. Summary of the Invention

[0004] To address the corresponding technical challenges in existing technologies, this invention provides a method for uniform composite impregnation of large-sized, irregularly shaped thermal insulation material components. This method is simple in process and easy to operate, solving the problem of poor impregnation, reducing the production cost of thermal insulation material components, and improving the yield rate of the components.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for uniform composite impregnation of large-sized irregularly shaped thermal insulation material components includes the following steps:

[0007] (1) Add several inlet and outlet ports at the set position of the large-size component molding mold to obtain an improved molding mold with gradient injection, and place the fiber preform in the improved molding mold.

[0008] (2) The sol precursor is injected using a high gradient pressure injection method, and the injection and discharge are carried out in sequence from low to high according to the inlet and outlet of the glue port. The fiber preform in the molding die is improved by pressure impregnation.

[0009] (3) Increase the amount of glue discharged and the number of glue injection cycles for the molding mold of large-size components to obtain fiber preform components impregnated with sol precursors.

[0010] Preferably, the fibers in the fiber preform are one or more of quartz fibers, alumina fibers, and mullite fibers.

[0011] Preferably, the sol precursor is one or both of silica sol precursor and alumina sol precursor.

[0012] Preferably, the ratio of the sol precursor is: silicon source: silicon salt or aluminum salt: organic solvent: deionized water: surfactant: acid catalyst: basic catalyst in a mass ratio of (2-10):(10-30):(10-30):(10-30):(0.03-0.5):(0.05-1):(0.05-1).

[0013] Preferably, the silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, and water glass.

[0014] The silicon or aluminum salt is one or more of the following: methyltrimethoxysilane, methyltriethoxysilane, aluminum isopropoxide, aluminum sec-butoxide, and aluminum tert-butoxide.

[0015] The organic solvent is one or more of methanol, ethanol, propanol, isopropanol, butanol, and acetone.

[0016] The surfactant is one or more of the following: dodecylamine, sodium stearate, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride.

[0017] The acidic catalyst is one or more of hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, acetic acid, and acetic acid.

[0018] The alkaline catalyst is one or more of dimethylamine, triethylamine, aniline, pyridine, ammonia, and ammonium fluoride.

[0019] Preferably, the position of the inlet and outlet of the glue added in step (1) is ≤0.4m above the upper end of the formed fiber preform component, and can be 0.1m, 0.15m, 0.2m, 0.25m, 0.3m, 0.35m or 0.4m.

[0020] Preferably, the pressure for impregnation in step (2) is 0.5 to 1 MPa, which can be 0.5 MPa, 0.55 MPa, 0.6 MPa, 0.65 MPa, 0.7 MPa, 0.75 MPa, 0.8 MPa, 0.85 MPa, 0.9 MPa, 0.95 MPa or 1 MPa.

[0021] Preferably, in step (3), the amount of glue discharged in the early stage of the glue injection process is increased to 40% to 50% of the mold cavity volume, and then increased to 50% to 100% of the mold cavity volume (which can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%); the number of cycles is increased by 1 (each time 100% of the mold cavity volume of glue is discharged, it is considered that one glue discharge cycle is completed).

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] (1) Since the sol precursor is an aqueous solution, while the fiber preform is woven from inorganic fiber yarns and contains organic wetting agents, there is a certain degree of incompatibility between the two, which is an important reason for uneven impregnation. To address this, the present invention employs a highly gradient pressure injection method to impregnate the fiber preform in the molding die, improving the uniformity of the injection of the thermal insulation composite material component. Furthermore, the present invention has found that increasing the amount of adhesive discharged / the number of injection cycles can increase the number of local sol impregnation cycles and reduce cavities. The fiber preform component prepared by the present invention is a fiber preform component with a gradient structure, that is, a preform with different fiber composition and density along the thickness direction.

[0024] (2) The method of this invention has no complex procedures, is simple and effective to operate. By changing the injection method, it can significantly reduce the unevenness of composite impregnation, reduce production costs, and improve the yield of components. The method of improving the injection molding mold in this invention is simple, inexpensive, and has low risk. It only requires drilling holes at specific locations and then installing injection ports. The method of this invention requires less equipment, is easy to operate, and has little environmental pollution.

[0025] (3) The method of the present invention is applicable to thermal insulation composite material components of regular and irregular shapes, whether individually segmented or as a whole, and has broad application prospects in the aerospace industry. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the flat gradient dispensing method in Example 1.

[0027] Figure 2 This is a schematic diagram of gradient glue injection for the overall compartment components in Example 2. Detailed Implementation

[0028] To make the various technical features, advantages, or effects of the present invention more apparent and understandable, a detailed description is provided below in conjunction with the accompanying drawings.

[0029] Example 1

[0030] This embodiment uses a precast flat panel component with a height of 0.3m.

[0031] In this embodiment, multiple parallel horizontal injection ports are designated as one injection layer, with each injection layer corresponding to an injection step. Different injection steps control the injection volume, ensuring that the silica sol in each injection layer of the component molding mold is simultaneously filled, maintaining a balanced injection system. This means the amount of adhesive in each layer matches the required amount, preventing uneven impregnation caused by rapid flow channels during the impregnation process of the sol precursor filling the fiber preform and its gaps. This also avoids the silica sol in one injection layer not being fully filled before entering other injection layers, and prevents insufficient adhesive or air bubbles in certain injection layers. Controlling the injection volume through different injection steps specifically includes the following steps:

[0032] Step 1: Calculate the required number and location of additional inlet / outlet ports for each molding die based on the actual working conditions of the product.

[0033] Step 2: Set up corresponding glue injection steps at each glue inlet and outlet; during glue injection, adopt gradient glue injection method: in the pressure injection stage, first apply 1MPa pressure to the glue inlet and outlet (1), glue injection layer (1) is injected, observe glue injection layer (2), if glue comes out, apply pressure to make glue injection layer (2) inject glue, then observe glue injection layer (3), if glue comes out, glue injection layer (3) is injected, observe glue injection layer (4), if glue comes out, glue injection layer (4) is injected.

[0034] Step 3: Adjust the injection volume according to the required volume of silica sol in each injection layer until the total injection volume increases to 50% of the mold cavity volume. Then verify the injection impregnation effect.

[0035] The fiber preform contains quartz fiber, and the sol precursor is a silica sol precursor. The sol precursor has the following mass ratio: silicon source: silicon salt: organic solvent: deionized water: surfactant: acid catalyst: basic catalyst = 2:10:10:10:0.03:0.05:0.05. The silicon source is methyl orthosilicate, the silicon salt is methyltrimethoxysilane, the organic solvent is methanol, the surfactant is dodecylamine, the acid catalyst is hydrofluoric acid, and the basic catalyst is dimethylamine.

[0036] Example 2

[0037] Example 2 is basically the same as Example 1, except that:

[0038] This embodiment uses a prefabricated section component with a height of 1.1m.

[0039] The fiber preform component used in this embodiment is a ring-shaped closed structure, with inlet and outlet ports added only to the outer molding die.

[0040] Based on the issue of poor impregnation at the upper end of the front compartment components, an additional ring was added circumferentially at 1 / 3 of the height from the upper end of the components (all ≤0.4m) (corresponding to the upper end glue inlet / outlet positions).

[0041] The amount of adhesive injected is controlled by using different injection steps, specifically including the following steps:

[0042] Step 1: Calculate the required number and location of additional inlet / outlet ports for each molding die based on the actual working conditions of the product.

[0043] Step 2: Set up corresponding glue injection steps at each glue inlet and outlet; during glue injection, adopt a gradient glue injection method: in the pressure injection stage, first inject glue into the bottom glue inlet and outlet, apply 0.5MPa pressure, observe the middle glue inlet and outlet, if glue comes out, then inject glue into the middle glue injection layer glue inlet and outlet, then observe the middle glue injection layer glue inlet and outlet, if glue comes out, then inject glue into the top glue inlet and outlet.

[0044] Step 3: Adjust the injection volume according to the required volume of silica sol in each injection layer until the total injection volume increases to 70% of the mold cavity volume. Then verify the injection impregnation effect.

[0045] The fiber preform contains alumina fibers, and the sol precursor is a silica sol precursor. The sol precursor has the following composition: silicon source: silicon salt: organic solvent: deionized water: surfactant: acid catalyst: basic catalyst mass ratio of 5:20:20:20:0.1:0.08:0.08. The silicon source is tetraethyl orthosilicate, the silicon salt is methyltriethoxysilane, the organic solvent is ethanol, the surfactant is sodium stearate, the acid catalyst is hydrochloric acid, and the basic catalyst is triethylamine.

[0046] Example 3

[0047] This embodiment uses a prefabricated modular component with a height of 1.1m.

[0048] Example 3 is basically the same as Example 2, except that:

[0049] This embodiment increases the amount of glue discharged / number of glue injection cycles for the molding die of large-sized components, with the amount of glue discharged increased to 100% (1 cycle).

[0050] The amount of adhesive injected is controlled by using different injection steps, specifically including the following steps:

[0051] Step 1: Calculate the required number and location of additional inlet / outlet ports for each molding die based on the actual working conditions of the product.

[0052] Step 2: Set up corresponding glue injection steps at each glue inlet and outlet; during glue injection, adopt a gradient glue injection method: in the pressure injection stage, first inject glue into the bottom glue inlet and outlet, apply 0.8MPa pressure, observe the middle glue inlet and outlet, if glue comes out, then inject glue into the middle glue injection layer glue inlet and outlet, then observe the middle glue injection layer glue inlet and outlet, if glue comes out, then inject glue into the top glue inlet and outlet.

[0053] Step 3: Adjust the injection volume according to the required volume of silica sol in each injection layer until the total injection volume increases to 100% of the mold cavity volume. Then verify the injection impregnation effect.

[0054] The fiber preform contains mullite fiber, and the sol precursor is alumina sol precursor. The sol precursor has the following composition: silicon source: aluminum salt: organic solvent: deionized water: surfactant: acid catalyst: basic catalyst mass ratio of 10:30:30:30:0.5:1:1. The silicon source is water glass, the aluminum salt is aluminum isopropoxide, the organic solvent is acetone, the surfactant is dodecyltrimethylammonium bromide, the acid catalyst is acetic acid, and the basic catalyst is ammonia.

[0055] The data on the impregnation of the components used in each embodiment after increasing the amount of adhesive discharged are shown in Table 1, and the composite impregnation density data are shown in Table 2.

[0056] Table 1. Data on impregnation of components after increasing adhesive application rate.

[0057]

[0058] Table 2 Composite Impregnation Density Data for Components

[0059] Example 1 0.262 0.466 0.204 Example 2 0.237 0.453 0.216 Example 3 0.298 0.508 0.209

[0060] Comparative Example

[0061] A large hull mold, 1.9m high, was used with a standard mold and glue injection method. The result was uneven glue impregnation over a large area.

[0062] Based on the above verification results, the following conclusions are drawn:

[0063] 1) Increasing the amount of glue discharged during the glue injection process of product components to more than 50% of the mold cavity volume can significantly improve the impregnation quality of compartment components with a height of ≤1m;

[0064] 2) The use of a height gradient injection method (height difference ≤ 0.4m) has basically eliminated the impregnation defects of flat plate components;

[0065] 3) The same height gradient injection method was used, which significantly improved the impregnation quality of the overall ring component with a height > 1m.

[0066] 4) The composite impregnation density gain data of the components after the improved impregnation method remained uniform and stable.

[0067] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention should be covered within the protection scope of the present invention, which is defined by the claims.

Claims

1. A method for uniform composite impregnation of large-sized irregularly shaped thermal insulation material components, characterized in that, The steps include the following: (1) Several inlet and outlet ports are added to the set position of the large-size component molding mold to obtain an improved molding mold with gradient injection. The fiber preform is placed in the improved molding mold. The set position is: the height of the added inlet and outlet ports from the upper end of the molded fiber preform component is ≤0.4m. (2) The sol precursor is injected using a height gradient pressure injection method, and the fiber preform in the improved molding die is impregnated under pressure. The height gradient pressure injection method is as follows: the sol precursor is first injected from the lowest position inlet and outlet. When the sol precursor is discharged from the adjacent higher position inlet and outlet, the injection is switched to the higher position inlet and outlet. This process is repeated step by step until the highest position inlet and outlet is reached to complete the injection. The pressure of the impregnation is 0.5~1MPa. (3) Increase the amount of glue discharged and the number of glue injection cycles for the molding mold of large-size components to obtain fiber preform components impregnated with sol precursors; the increase in the amount of glue discharged and the number of glue injection cycles is as follows: the amount of glue discharged in the early glue injection process is increased to 40%~50% of the mold cavity volume, and then increased to 50%~100% of the mold cavity volume; the number of cycles is increased by 1.

2. The uniform composite impregnation method for large-sized irregularly shaped thermal insulation material components as described in claim 1, characterized in that, The fibers in the fiber preform are one or more of quartz fiber, alumina fiber, and mullite fiber.

3. The uniform composite impregnation method for large-sized irregularly shaped thermal insulation material components as described in claim 1, characterized in that, The sol precursor is one or both of silica sol precursor and alumina sol precursor.

4. The uniform composite impregnation method for large-sized irregularly shaped thermal insulation material components as described in claim 1, characterized in that, The ratio of the sol precursor is as follows: silicon source: silicon salt or aluminum salt: organic solvent: deionized water: surfactant: acid catalyst: basic catalyst mass ratio is (2~10):(10~30):(10~30):(10~30):(0.03~0.5):(0.05~1):(0.05~1).

5. The uniform composite impregnation method for large-sized irregularly shaped thermal insulation material components as described in claim 4, characterized in that, The silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, and water glass. The silicon or aluminum salt is one or more of the following: methyltrimethoxysilane, methyltriethoxysilane, aluminum isopropoxide, aluminum sec-butoxide, and aluminum tert-butoxide; The organic solvent is one or more selected from methanol, ethanol, propanol, isopropanol, butanol, and acetone; The surfactant is one or more of the following: dodecylamine, sodium stearate, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride; The acidic catalyst is one or more of hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, and acetic acid. The alkaline catalyst is one or more of dimethylamine, triethylamine, aniline, pyridine, ammonia, and ammonium fluoride.

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