A method of forming a thermal insulation layer of a filament wound engine closure head

Abstract

The application discloses a kind of fibre winding engine head heat insulation layer forming method, using autoclave forming method, first metal joint bonding surface sandblasting, clean, after gluing patch with middle die assembly fixed;Then patch according to heat insulation layer profile and thickness on the surface of male die;Finally, middle die (including the metal joint of patch completion) is assembled with the mold of patch completion, overall vacuum bag is extracted, and preforming is carried out after preforming is completed, and heat insulation layer is trimmed and autoclaved.Solve the low production efficiency of traditional mould pressing mode one-pressing one-mould, and reduce the investment of tooling and equipment, reduce production cost.The forming die used is single-side die structure, only one male die is needed, compared with traditional mould pressing tooling (consisting of a male die and a female die), the tooling structure used in the application is relatively simple and low in cost.

Description

Technical Field

[0001] This invention belongs to the field of fiber-wound engine casing insulation structure forming technology, specifically relating to a method for forming a fiber-wound engine head insulation layer. Background Technology

[0002] The thermal insulation layer of a solid rocket motor is a heat-insulating material located between the inner wall of the motor casing and the propellant grain. It consists of three parts: the front and rear end insulation layers, and the casing body insulation layer. Currently, most domestic solid rocket motor composite material casing insulation layers for the front and rear end caps are produced using integral molding. However, with the increase in motor casing diameter, the investment costs in molding equipment and mold processing, as well as the production cycle, have become significantly more challenging. Autoclave molding is a novel end cap molding technology. Its main advantages are that it only requires a single-sided mold, resulting in lower mold costs, and it can produce multiple products per batch, significantly improving production efficiency.

[0003] Based on the above considerations, a method for autoclaving the insulation layer of a fiber-wound engine head is proposed. This method not only solves the problem of low production efficiency in traditional molding methods (one press, one mold), but also reduces the investment in tooling and equipment, thereby lowering production costs. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of traditional molding methods, such as high tooling and equipment investment costs and low production efficiency of one-press-one-mold production, and provides a method for molding fiber-wound engine head insulation layers with simple molding molds and multiple parts in one batch.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for forming a fiber-wound engine head insulation layer is as follows:

[0006] 1) Surface treatment of metal joints

[0007] 2) Insulation layer film treatment

[0008] The joints of the insulating film with a mating relationship are ground and beveled to produce an insulating film with a bevel.

[0009] 3) Apply and assemble the insulation film.

[0010] 3a) Metal joint surface patch: Apply adhesive to the surface of the insulation layer film to be pasted to the metal joint and let it dry. After pasting the insulation layer films on the inner and outer surfaces of the metal joint, assemble and fix them to the middle mold in the molding mold.

[0011] 3b) Applying heat insulation film to the punch surface: Apply heat insulation film with bevels to the punch surface according to the thickness and shape of the insulation layer of each part of the end cap;

[0012] 3c) Assembly: Assemble the intermediate mold from step 3a) with the punch in the molded mold after patching, and connect and fix them with bolts to form an integral mold;

[0013] 4) Pre-formed insulation layer

[0014] 4a) Pre-compress the vacuum-sealed film bag;

[0015] 4b) Pre-vulcanization to obtain a pre-formed insulation layer;

[0016] 5) Trimming of pre-formed insulation layer

[0017] 6) Vulcanization molding

[0018] 6a) Vacuum film bag making: Place the integral molding mold on the autoclave platform, first lay a layer of polytetrafluoroethylene fiberglass release cloth on the surface of the finished and pre-formed insulation layer, and overlap is allowed between the release cloths; then lay a layer of breathable felt, and overlap is allowed between the breathable felts; put the vacuum film bag on the outside, seal the opening edge of the vacuum film bag with sealing strips, and leave a vacuum tube interface.

[0019] 6b) Vacuuming: Connect the vacuum tube of the external vacuum pump to the pre-installed vacuum tube interface inside the vacuum film bag. Turn on the vacuum pump to evacuate to a vacuum level ≤ -0.1MPa. Turn off the vacuum pump and check the vacuum level after five to ten minutes. It should be ≤ -0.1MPa. If it is greater than -0.1MPa, it means that the vacuum film bag is not completely sealed. Check the vacuum film bag, find the leak, and seal it with sealing strips. After sealing, turn on the vacuum pump again to check whether the vacuum film bag is completely sealed. Repeat the check and sealing until the vacuum level is ≤ -0.1MPa after turning off the vacuum pump for five to ten minutes.

[0020] 6c) Vulcanization: After the vacuum film bag meets the vacuum requirements, the furnace door is closed for vulcanization. The vulcanization process is as follows:

[0021] ① Evacuate the vacuum to remove air and volatile substances;

[0022] ② Vacuum requirements during vulcanization: Vacuum is drawn before heating, with a vacuum degree ≤ -0.1MPa. The vacuum degree is maintained at ≤ -0.1MPa throughout the heating and heat preservation stages. Vacuum drawing is stopped after heat preservation is completed.

[0023] ③ Vulcanization process: At the start of heating, apply an initial pressure of 0.5–0.7 MPa and maintain a heating rate of 0.1–0.3 °C / min to raise the temperature from room temperature to 90–110 °C. Hold the temperature for 20–40 min. After holding, apply pressure of 0.8–1.2 MPa and maintain the pressure at 0.8–1.2 MPa. Continue heating at a rate of 0.1–0.3 °C / min to raise the temperature to 140–155 °C and hold for 100–150 min. Maintain the pressure at 0.8–1.2 MPa. After holding, cool down at a rate of 0.1–0.3 °C / min, allowing the pressure to drop naturally. Once the temperature drops below 60 °C, turn off the vacuum pump and remove the product from the furnace.

[0024] Furthermore, in step 1), the specific method for surface treatment of the metal joint is as follows:

[0025] 1a) The bonding surface of the metal joint is sandblasted, and the sandblasted metal joint surface is cleaned with ethyl acetate and then dried.

[0026] 1b) Apply two coats of primer to the bonding surface of the metal joint and let it dry. Then apply two coats of topcoat to the primer and let it dry.

[0027] Furthermore, in step 2), the beveled insulation film is cleaned with ethyl acetate to remove the sanded-off adhesive powder.

[0028] Furthermore, in step 3b), the insulation films are joined by a beveled overlap, and the overlap seams of each layer of insulation films with bevels are staggered.

[0029] Further, the specific process of step 4a) is as follows: after the patch is applied, a vacuum film bag is used for vacuum pre-compression treatment to obtain a pre-formed insulation layer; the specific process is as follows: first, a layer of polytetrafluoroethylene fiberglass release cloth is laid on the surface of the insulation layer film. The release cloth is allowed to overlap, but folding or wrinkling is not allowed; then, a layer of breathable felt is laid. The breathable felt is allowed to overlap, but folding or wrinkling is not allowed; then, a vacuum film bag is put on the outside. The opening edge of the vacuum film bag is sealed with sealing strips. Then, a vacuum pump is used to test the air extraction of the vacuum film bag and remove all the air from the vacuum film bag.

[0030] Furthermore, the specific process of the pre-vulcanization in 4b) is as follows: turn on the vacuum pump to maintain the vacuum state inside the vacuum film bag, then put the integral molding mold into the furnace at 80-100°C for 1-2 hours, and after cooling to room temperature, take it out of the furnace to obtain the pre-formed heat insulation layer.

[0031] Furthermore, the specific process of step 5) is as follows:

[0032] 5a) Remove the vacuum pump, remove the sealing strip, vacuum bag film, breathable felt, and PTFE fiberglass release cloth, compare the surface of the pre-formed insulation layer with the template, grind the protruding parts, fill the pits with raw rubber sheets according to the shape of the pits, compact them, and grind the surface protrusions to ensure a smooth transition.

[0033] 5b) Cleaning: Use ethyl acetate to clean the surface of the pre-formed insulation layer after grinding to remove grinding dust and other excess materials, ensuring that the surface of the pre-formed insulation layer is clean and free of dirt.

[0034] Furthermore, in step 5a), if there is air trapped between the layers of the preformed insulation layer, the surface of the preformed insulation layer needs to be punctured to release the gas. After the preformed insulation layer is repaired, the surface should be flat without obvious protrusions or pits, and the surface requirements should be met.

[0035] Compared with the prior art, the advantages of the present invention are as follows: by adopting the head-end autoclave molding method, it can not only solve the problem of low production efficiency of traditional molding method, but also reduce tooling and equipment investment and reduce production costs; the molding mold adopted is a single-sided mold structure, which only requires one punch. Compared with the traditional molding tooling (composed of a punch and a die), the tooling structure adopted by the present invention is simple and low cost. Attached Figure Description

[0036] Figure 1 This is a simplified schematic diagram of the molding die structure of the present invention. Detailed Implementation

[0037] The method for forming the fiber-wound engine head insulation layer of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments:

[0038] 1) Surface treatment of metal joints

[0039] 1a) The bonding surface of the metal joint is sandblasted, and the sandblasted metal joint surface is cleaned with ethyl acetate and then dried.

[0040] 1b) Apply two coats of primer (Chemlock 205) to the bonding surface of the metal joint and let it dry. Then apply two coats of topcoat to the primer and let it dry.

[0041] 2) Insulation layer film treatment

[0042] 2a) The insulation layer film is prepared by cutting and cutting the film according to the shape and thickness of the insulation layer;

[0043] 2b) The splicing positions of the insulation films with mating relationships are ground and beveled to obtain insulation films with bevels. The insulation films with bevels are cleaned with ethyl acetate to remove the sanding powder and ensure that the surface of the insulation films with bevels is clean and free of dirt.

[0044] The insulation film is made of EPDM or 824 materials.

[0045] 3) Apply and assemble the insulation film.

[0046] 3a) Metal Joint Surface Patches: Apply adhesive to the surface of the insulation layer patch to be bonded to the metal joint and allow it to dry. Then, after the insulation layer patches on the inner and outer surfaces of the metal joint are bonded, assemble them with the middle mold 1 in the molding die (e.g., Figure 1 (As shown), and fixed with bolts;

[0047] 3b) Applying heat insulation film to the surface of the punch: Apply heat insulation film with bevels to the surface of the punch 2 according to the thickness and shape of the heat insulation layer of each part of the end cap. The heat insulation film is overlapped with bevels, and the overlap seams of each layer of heat insulation film with bevels are staggered.

[0048] 3c) Assembly: Assemble the intermediate mold (i.e., the intermediate mold with the patch-finished metal connector) from step 3a) with the punch in the patch-finished molding die, and fix them together with bolts to form an integral molding die (e.g., Figure 1 (As shown), ensure that the punch is assembled in place.

[0049] 4) Pre-formed insulation layer

[0050] 4a) Vacuum film bag pre-compression: After the patch is applied, a vacuum film bag is used for vacuum pre-compression to obtain a pre-formed insulation layer; the specific process is as follows: first, a layer of polytetrafluoroethylene fiberglass release cloth is laid on the surface of the insulation layer film. The release cloth is allowed to overlap, but folding or wrinkling is not allowed; then a layer of breathable felt is laid. The breathable felt is allowed to overlap, but folding or wrinkling is not allowed; then a vacuum film bag is put on the outside. The opening edge of the vacuum film bag is sealed with sealing strips. Then, a vacuum pump is used to test the air extraction of the vacuum film bag and remove all the air inside the vacuum film bag.

[0051] 4b) Pre-vulcanization: Turn on the vacuum pump to maintain the vacuum state inside the vacuum film bag, then put the integral molding mold into the furnace at 80-100℃ (e.g., 90℃) and keep it at that temperature for 1-2 hours (e.g., 1 hour). After cooling to room temperature, remove it from the furnace to obtain the pre-formed insulation layer.

[0052] 5) Trimming of pre-formed insulation layer

[0053] 5a) Remove the vacuum pump, and remove the sealing strip, vacuum bag film, breathable felt, and PTFE fiberglass release cloth. Compare the surface of the preformed insulation layer with the template. Grind the raised parts and fill the pits with raw rubber sheets according to the shape of the pits. After compaction, grind the raised parts of the surface to ensure a smooth transition. If there is air trapped between the layers of the preformed insulation layer, the surface of the preformed insulation layer needs to be punctured to release the gas. After the preformed insulation layer is repaired, the surface should be flat without obvious protrusions or pits and meet the template requirements.

[0054] 5b) Cleaning: Use ethyl acetate to clean the surface of the pre-formed insulation layer after grinding to remove grinding dust and other excess materials, ensuring that the surface of the pre-formed insulation layer is clean and free of dirt.

[0055] 6) Vulcanization molding

[0056] 6a) Vacuum film bag: Place the integral molding mold on the autoclave platform, first lay a layer of polytetrafluoroethylene fiberglass release cloth on the surface of the finished and pre-formed insulation layer. The release cloth is allowed to overlap, but folding or wrinkling is not allowed. Then lay a layer of breathable felt. The breathable felt is allowed to overlap, but folding or wrinkling is not allowed. Put the vacuum film bag on the outside. Seal the opening edge of the vacuum film bag with sealing strips and leave the vacuum tube interface.

[0057] 6b) Vacuuming: Connect the vacuum tube of the external vacuum pump to the pre-installed vacuum tube interface inside the vacuum film bag. Turn on the vacuum pump to evacuate to a vacuum level ≤ -0.1MPa. Turn off the vacuum pump and check the vacuum level after five minutes. It should be ≤ -0.1MPa. If it is greater than -0.1MPa, it means that the vacuum film bag is not completely sealed. Check the vacuum film bag, find the leak, and seal it with sealing strip. After sealing, turn on the vacuum pump again to check whether the vacuum film bag is completely sealed. Repeat the check and sealing until the vacuum level is ≤ -0.1MPa after turning off the vacuum pump for 5 minutes.

[0058] 6c) Vulcanization: After the vacuum film bag meets the vacuum requirements, the furnace door is closed for vulcanization. The vulcanization process is as follows:

[0059] ① Evacuate the vacuum to remove air and volatile substances;

[0060] ② Vacuum requirements during vulcanization: Vacuum is drawn before heating, with a vacuum degree ≤ -0.1MPa. The vacuum degree is maintained at ≤ -0.1MPa throughout the heating and heat preservation stages. Vacuum drawing is stopped after heat preservation is completed.

[0061] ③ Vulcanization process: At the start of heating, apply initial pressure of 0.5–0.7 MPa (e.g., 0.6 MPa), maintain a heating rate of 0.1–0.3℃ / min (e.g., 0.2℃ / min) to raise the temperature from room temperature to 90–110℃ (e.g., 100℃), hold for 20–40 min, after which apply pressure of 0.8–1.2 MPa (e.g., 0.9 MPa), maintain the pressure at 0.8–1.2 MPa (e.g., 0.9 MPa), maintain a heating rate of 0.1–0.3℃ / min (e.g., 0.2℃ / min), continue heating to 140–155℃ (e.g., 150℃), hold for 100–150 min, maintain the pressure at 0.8–1.2 MPa (e.g., 0.9 MPa), after which cool down at a rate of 0.1–0.3℃ / min (e.g., 0.2℃ / min), allow the pressure to drop naturally, and remove from the furnace when the temperature drops below 60℃.

[0062] ④ After cooling to below 60℃, turn off the vacuum pump and remove from the furnace.

[0063] 7) Demolding

[0064] Open the molding mold, remove the vacuum film bag, separate the product from the middle mold and the punch, demold, and clean the flash.

Claims

1. A method for forming a fiber-wound engine head insulation layer, characterized in that: The molding method is as follows: 1) Surface treatment of metal joints 2) Insulation layer film treatment The joints of the insulating film with a mating relationship are ground and beveled to produce an insulating film with a bevel. 3) Applying and assembling the insulation film 3a) Metal joint surface patch: Apply adhesive to the surface of the heat insulation layer film to be pasted to the metal joint and let it dry. After pasting the heat insulation layer film on the inner and outer surfaces of the metal joint, assemble and fix it with the middle mold in the molding mold. 3b) Applying heat insulation film to the punch surface: Apply heat insulation film with bevels to the punch surface according to the thickness and shape of the insulation layer of each part of the end cap; 3c) Assembly: Assemble the intermediate mold from step 3a) with the punch in the molded mold after patching, and fix them with bolts to form an integral mold; 4) Pre-formed insulation layer 4a) Pre-compress the vacuum-sealed film bag; 4b) Pre-vulcanization to obtain a pre-formed insulation layer; 5) Trimming of pre-formed insulation layer 6) Vulcanization molding 6a) Vacuum film bag making: Place the integral molding mold on the autoclave platform, first lay a layer of polytetrafluoroethylene fiberglass release cloth on the surface of the finished and pre-formed insulation layer, with the release cloth overlapping; then lay a layer of breathable felt, with the breathable felt overlapping; put the vacuum film bag on the outside, seal the opening edge of the vacuum film bag with sealing strips, and leave a vacuum tube interface. 6b) Vacuuming: Connect the vacuum tube of the external vacuum pump to the pre-reserved vacuum tube interface inside the vacuum film bag. Turn on the vacuum pump to evacuate to a vacuum level ≤ -0.1MPa. Turn off the vacuum pump and check the vacuum level after five to ten minutes. It should be ≤ -0.1MPa. If it is greater than -0.1MPa, it means that the vacuum film bag is not completely sealed. Check the vacuum film bag, find the leak point, and seal it with sealing strip. After sealing, turn the vacuum pump back on to check if the vacuum film bag is completely sealed; repeat the check and sealing until the vacuum degree is ≤-0.1MPa after turning off the vacuum pump for five to ten minutes. 6c) Vulcanization: After the vacuum film bag meets the vacuum requirements, the furnace door is closed for vulcanization. The vulcanization process is as follows: ① Evacuate the vacuum to remove air and volatile substances; ② Vacuum requirements during vulcanization: Vacuum is drawn before heating, with a vacuum degree ≤ -0.1MPa. The vacuum degree is maintained at ≤ -0.1MPa throughout the heating and heat preservation stages. Vacuum drawing is stopped after heat preservation is completed. ③ Vulcanization process: At the start of heating, apply an initial pressure of 0.5~0.7MPa and maintain a heating rate of 0.1~0.3℃ / min to raise the temperature from room temperature to 90-110℃. Hold the temperature for 20~40min. After holding, apply pressure of 0.8~1.2MPa and maintain the pressure at 0.8~1.2MPa. Continue heating at a rate of 0.1~0.3℃ / min to raise the temperature to 140~155℃ and hold for 100~150min. Maintain the pressure at 0.8~1.2MPa. After holding, cool down at a rate of 0.1~0.3℃ / min, allow the pressure to drop naturally, and turn off the vacuum pump when the temperature drops below 60℃ before removing the product from the furnace.

2. The method for forming the insulation layer of a fiber-wound engine head according to claim 1, characterized in that: In step 1), the specific method for surface treatment of the metal joint is as follows: 1a) The bonding surface of the metal joint is sandblasted, and the sandblasted metal joint surface is cleaned with ethyl acetate and then dried. 1b) Apply primer to the bonding surface of the metal joint and let it dry, then apply topcoat to the primer and let it dry.

3. The method for forming the insulation layer of a fiber-wound engine head according to claim 1, characterized in that: In step 2), the beveled insulation film is cleaned with ethyl acetate to remove the sanded-off adhesive powder.

4. The method for forming the insulation layer of a fiber-wound engine head according to claim 1, characterized in that: In step 3b), the insulation films are joined by a beveled overlap, and the overlap seams of each layer of insulation films with bevels are staggered.

5. The method for forming the insulation layer of a fiber-wound engine head according to claim 1, characterized in that: The specific process of step 4a) is as follows: After the patch is applied, a vacuum film bag is used for vacuum pre-compression to obtain a pre-formed insulation layer; the specific process is as follows: first, a layer of polytetrafluoroethylene fiberglass release cloth is laid on the surface of the insulation layer film, and the release cloth overlaps with each other; then, a layer of breathable felt is laid, and the breathable felt overlaps with each other; then, a vacuum film bag is put on the outside, and the opening edge of the vacuum film bag is sealed with sealing strips around the perimeter. Then, a vacuum pump is used to test the air extraction of the vacuum film bag and remove all the air from the vacuum film bag.

6. The method for forming the insulation layer of a fiber-wound engine head according to claim 1, characterized in that: The specific process of pre-vulcanization in 4b) is as follows: turn on the vacuum pump to maintain the vacuum state inside the vacuum film bag, then put the integral molding mold into the furnace at 80~100℃ for 1~2 hours, and after cooling to room temperature, take it out of the furnace to obtain the pre-formed heat insulation layer.

7. The method for forming the insulation layer of a fiber-wound engine head according to claim 1, characterized in that: The specific process of step 5) is as follows: 5a) Remove the vacuum pump, remove the sealing strip, vacuum bag film, breathable felt, and PTFE fiberglass release cloth, compare the surface of the pre-formed insulation layer with the template, grind the protruding parts, fill the pits with raw rubber sheets according to the shape of the pits, compact them, and grind the surface protrusions to ensure a smooth transition. 5b) Cleaning: Use ethyl acetate to clean the grinding dust from the surface of the pre-formed insulation layer after grinding, ensuring that the surface of the pre-formed insulation layer is clean and free of dirt.

8. The method for forming the insulation layer of a fiber-wound engine head according to claim 7, characterized in that: In step 5a), if there is air trapped between the layers of the preformed insulation layer, the surface of the preformed insulation layer needs to be punctured to release the gas. After the preformed insulation layer is repaired, the surface should be flat without obvious protrusions or pits, and the surface requirements should be met.

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