Forming method suitable for high-temperature-resistant winding engine shell

Abstract

The invention discloses a forming method suitable for a high-temperature-resistant winding engine shell. Vulcanization of an internal heat insulation layer and preliminary shaping of an external composite material structure layer are synchronously completed through pre-curing treatment, and then a regional accurate temperature control strategy of internal water circulation cooling and external high-temperature curing is adopted; the contradiction between the over-vulcanization prevention temperature limitation of the internal heat insulation layer and the high-temperature curing requirement of the external composite material structure layer is thoroughly decoupled, so that the internal heat insulation layer of the shell has excellent elasticity, adhesion and heat insulation performance, and the external composite material structure layer has excellent mechanical strength, modulus and high-temperature resistance; and the overall quality and the service reliability of the final shell are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of composite material engine housing manufacturing technology, and relates to a molding method suitable for high-temperature resistant wound engine housing, specifically a molding process that resolves the conflict between the vulcanization temperature of the internal insulation layer and the high-temperature curing temperature of the external composite material. Background Technology

[0002] In the manufacturing of traditional high-temperature wound engine casings (such as solid rocket motor casings), the internal rubber insulation layer (such as EPDM and nitrile rubber) needs to be vulcanized at a medium-low temperature environment of 130-160℃ to prevent over-vulcanization, which would lead to a decrease in mechanical and ablation properties. Meanwhile, the external composite structural layer (such as carbon fiber / epoxy resin or carbon fiber / bismaleimide resin) needs to be cured at temperatures above 200℃ to achieve high mechanical and heat resistance. When traditional processes use stepwise curing, the high-temperature curing of the structural layer can trigger secondary over-vulcanization of the already vulcanized insulation layer (interface temperatures can reach above 180℃). If the entire structure is co-cured, there is a dilemma: insufficient curing at low temperatures leads to performance degradation of the structural layer, while high temperatures cause embrittlement and failure of the insulation layer. Existing technologies (such as the molding method for composite engine casings CN117227207A) cannot simultaneously address both issues, becoming a bottleneck restricting the manufacturing of high-reliability casings. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a molding method suitable for high-temperature resistant wound engine housings. This invention employs a phased, zoned temperature control strategy combining pre-curing with precise internal water circulation and external high-temperature curing. This effectively prevents over-sulfurization of the insulation layer, ensuring its performance, while simultaneously guaranteeing the composite material structural layers achieve the required high-temperature curing strength and heat resistance. This significantly improves the quality, reliability, and manufacturing efficiency of the housing product.

[0004] The objective of this invention can be achieved through the following methods: In a first aspect, the present invention provides a molding method suitable for high-temperature resistant wound engine housings, comprising the following steps: S1. Lay an inner insulation layer on the core mold system, and wrap an outer composite material around the surface of the inner insulation layer to form an outer composite material structure layer, thus obtaining a shell preform. S2. Pre-curing treatment is carried out on the precast shell to complete the vulcanization of the internal insulation layer; S3. Remove the core mold system to create an internal cavity; S4. Install an external water circulation system to inject circulating cooling water into the internal cavity and maintain the temperature of the internal insulation layer area below the anti-oversulfurization temperature threshold. S5. Heat and cure the external composite material structural layer to obtain the final product.

[0005] The molding method of the present invention includes: laying up the insulation layer, fiber winding molding, product pre-curing, removing the core mold, installing water circulation equipment, and high-temperature curing.

[0006] As one embodiment of the present invention, in step S1 or step S3, the core mold system includes a main core mold and a collapsible sand core mold filled inside it.

[0007] Furthermore, the collapsible sand core mold is made by bonding sand particles together with a water-soluble binder; wherein the sand particles include one or more of quartz sand and abrasive sand, and the water-soluble binder includes polyvinyl alcohol (PVA).

[0008] Furthermore, the step of removing the core mold system includes: detaching the shell preform from the main core mold, and then flushing and removing the collapsible sand core mold.

[0009] Furthermore, the erosion removal is achieved by impacting the sand core mold with high-pressure water. In step S3 of this invention, the internal sand core mold is disassembled after the composite material shell has been pre-cured, ensuring that the interior of the shell has a cavity for water circulation.

[0010] As one embodiment of the present invention, in step S1, the material of the inner insulation layer is a rubber-based insulation material, which includes EPDM rubber sheet; the outer composite material includes carbon fiber reinforced resin-based composite material or glass fiber reinforced resin-based composite material, which includes carbon fiber / bismaleimide resin.

[0011] In one embodiment of the present invention, in step S2, the pre-curing treatment is carried out at a temperature of 80-160°C for 1-6 hours. The pre-curing treatment of the present invention aims to initially shape the external composite material structural layer, preventing deformation and other problems in the future; and simultaneously allows the internal insulation layer to complete vulcanization.

[0012] In one embodiment of the present invention, in step S4, the over-curing temperature threshold is 160-165 ℃, which is the maximum permissible curing temperature of the material used in the internal insulation layer.

[0013] As one embodiment of the present invention, in step S4, the external water circulation system includes a thermocouple, a temperature controller, a water circulation pump, a cooling device, and a conduit; wherein the thermocouple is attached to the surface of the internal insulation layer and is sequentially connected to the temperature controller and the water circulation pump, and the water circulation pump and the cooling device are connected to the internal cavity through the conduit.

[0014] In one embodiment of the present invention, in step S4, the circulating cooling water circulates through an inlet and an outlet located in the internal cavity; the temperature of the circulating cooling water is controlled between 40-80°C. The present invention utilizes an external water circulation system to provide circulating cooling water; simultaneously, by controlling the temperature and / or flow rate of the circulating water through thermocouples, it ensures that the water temperature inside the shell is below the sulfidation temperature, thus preventing over-sulfidation of the insulation layer.

[0015] In one embodiment of the present invention, in step S5, the heating and curing temperature is 200-250°C, and the time is 2-8 hours. This curing completely cures the outer composite material structural layer; after curing, the water circulation equipment is removed (water circulation is stopped), the water in the internal cavity is drained, and low-temperature drying is performed to remove excess moisture from the inside of the shell.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention simultaneously completes the vulcanization of the internal insulation layer and the preliminary shaping of the external composite material structure layer through pre-curing treatment. Then, through a regional precise temperature control strategy of "internal water circulation cooling + external high-temperature curing", the contradiction between the internal insulation layer's anti-over-vulcanization temperature limit and the external composite material structure layer's high-temperature curing requirement is completely decoupled. This ensures that the internal insulation layer of the shell has excellent elasticity, adhesion and insulation performance, and that the external composite material structure layer has excellent mechanical strength, modulus and high-temperature resistance.

[0017] 2. On the one hand, the present invention utilizes internal water circulation for forced cooling to strictly control the temperature of the insulation layer within a safe range, effectively eliminating the risk of over-sulfurization and protecting the elasticity, adhesion, and insulation performance of the insulation layer; on the other hand, the external high-temperature environment fully ensures that the composite material structural layer reaches the required glass transition temperature (Tg) and crosslinking density, thereby obtaining optimal mechanical strength, modulus, and high-temperature resistance.

[0018] 3. The water circulation system of this invention allows for precise control of temperature and flow rate, enabling effective regulation of internal temperature and strong process controllability. At the same time, it avoids the risks of over-sulfurization and deterioration of the insulation layer and insufficient curing of the structural layer, significantly improving the overall quality and service reliability of the final shell. Attached Figure Description

[0019] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of a water circulation cooling system. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0021] Example 1 This embodiment provides a molding method suitable for high-temperature resistant wound engine housings, including the following steps: S1 Winding: Preparing the core mold system: This includes the main core mold (which needs to be disassembled) and the internally filled collapsible sand core mold. The sand core mold must be precisely shaped to ensure the internal profile of the shell. The sand core mold material is made of sand particles (quartz sand) bonded with a water-soluble binder (polyvinyl alcohol PVA), possessing sufficient winding support strength while also being able to dissolve in water and collapse upon impact.

[0022] On the core mold system, the following steps are taken: first, the inner insulation layer (uncured EPDM rubber sheet) is laid, and then the outer composite material structural layer (T800 carbon fiber / bismaleimide resin wet winding) is wound to form the shell preform (shell diameter 1m, length 3m).

[0023] S2 Pre-curing: 1. Place the wound product (along with the mandrel system) into a curing device (such as an oven or autoclave).

[0024] 2. Heat to the pre-curing temperature (160℃) and maintain the temperature for 3 hours for pre-curing.

[0025] Key function: To enable the external composite material structural layers to initially gel and cross-link, gaining sufficient "mechanical strength" to maintain shape and facilitate subsequent operations. Simultaneously, to allow the rubber insulation layer to complete its main vulcanization reaction (reaching the positive vulcanization point) at this temperature and time, acquiring basic elasticity and adhesion properties. This temperature is below the critical temperature at which the insulation layer over-vulcanizes.

[0026] S3 Product Demolding: Remove the pre-cured shell from the main core mold (the main core mold is removable). Insert a high-pressure water pipe through the shell's open end (such as the skirt or front and rear end caps). Use the high-pressure water flow to impact the sand core mold; the water-soluble adhesive dissolves in the water, and the sand particles are carried away by the water flow and flushed out of the shell. Continue rinsing until the sand core mold is completely cleaned, forming an internal cavity consistent with the design, ensuring no residual sand particles.

[0027] S4 Internal Water Circulation Cooling: Inlet and outlet water ports are installed at appropriate locations within the shell cavity (e.g., front / rear end caps or skirt) (existing openings or specially designed interfaces can be used). Connect to an external water circulation system (e.g., Figure 1As shown, it includes a thermocouple, a temperature controller, a water circulation pump, a cooling device, and a conduit; wherein the thermocouple is attached to the surface of the inner insulation layer and is connected in sequence to the temperature controller and the water circulation pump, and the water circulation pump and the cooling device are connected to the inner cavity through the conduit, so that cooling water is injected into the cavity to start the circulation.

[0028] Core control: The temperature of the area near the insulation layer inside the shell is monitored in real time via thermocouples, and the temperature (controlling the outlet water temperature to ≤65℃, corresponding to the internal insulation layer interface temperature <80℃) and flow rate (10m³ / h) of the circulating water are adjusted by the cooling equipment. 3 / h), ensuring that the temperature in this area remains below the preset "anti-over-sulfurization temperature threshold" (lower than the maximum allowable sulfidation temperature of the insulation material, i.e., far below the 165℃ risk point). The role of water circulation is to actively and forcibly remove the heat conducted in from the external high-temperature environment, forming a relatively low-temperature protective zone near the insulation layer.

[0029] S5 External High-Temperature Curing: While step S4 is in progress (i.e., internal water circulation is ongoing), place the entire shell inside a high-temperature oven. Raise the oven temperature to the high temperature required for the structural layer resin and hold it at this temperature for a sufficient time (200℃ / 2h + 250℃ / 2h) to ensure that the external composite material structural layer is completely cured and reaches its optimal performance.

[0030] Key point: Heat from the high external temperature is conducted inward through the composite material layer, but the continuous internal water circulation effectively keeps the temperature in the insulation layer area within a safe range. A state of external heat and internal coolness coexists.

[0031] S6 product molding completed: Turn off the oven heating and wait for the temperature to drop to a safe range (e.g., <80℃). Then stop the water circulation, drain the cooling water from the internal cavity, dry the product (e.g., by blowing with hot air or nitrogen), and perform final demolding (e.g., auxiliary support), cleaning, inspection and other post-processing steps.

[0032] Comparative Example 1 The molding method of this comparative example is basically the same as that of Example 1, except that the internal water circulation cooling in step S4 is omitted. As a result, when the external high-temperature curing is carried out in step S5, the already vulcanized internal insulation layer is over-vulcanized again, which leads to a decrease in the mechanical properties and ablation resistance of the shell.

[0033] It should be noted that the method for molding a high-temperature resistant wound engine housing in this embodiment is not limited to wound engine housings. As long as it involves the curing of rubber and composite materials that requires a high-temperature environment for molding, this molding method can be used and all fall within the protection scope of this application.

[0034] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0035] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A molding method suitable for high-temperature resistant wound engine housings, characterized in that, Includes the following steps: S1. Lay an inner insulation layer on the core mold system, and wrap an outer composite material around the surface of the inner insulation layer to form an outer composite material structure layer, thus obtaining a shell preform. S2. Pre-curing treatment is carried out on the precast shell to complete the vulcanization of the internal insulation layer; S3. Remove the core mold system to create an internal cavity; S4. Install an external water circulation system to inject circulating cooling water into the internal cavity and maintain the temperature of the internal insulation layer area below the anti-oversulfurization temperature threshold. S5. Heat and cure the external composite material structural layer to obtain the final product.

2. The molding method according to claim 1, characterized in that, In step S1 or step S3, the core mold system includes a main core mold and a collapsible sand core mold filled inside it.

3. The molding method according to claim 2, characterized in that, The collapsible sand core mold is made by bonding sand particles together with a water-soluble binder; wherein the sand particles include one or more of quartz sand and abrasive sand, and the water-soluble binder includes polyvinyl alcohol (PVA).

4. The molding method according to claim 2, characterized in that, The steps for dismantling the core mold system include: detaching the precast shell from the main core mold, and then flushing and removing the collapsible sand core mold; the flushing and removal is carried out by impacting the sand core mold with high-pressure water.

5. The molding method according to claim 1, characterized in that, In step S1, the material of the inner insulation layer is a rubber-based insulation material, which includes EPDM rubber sheet; the outer composite material includes carbon fiber reinforced resin-based composite material or glass fiber reinforced resin-based composite material, which includes carbon fiber / bismaleimide resin.

6. The molding method according to claim 1, characterized in that, In step S2, the pre-curing treatment is carried out at a temperature of 80-160℃ for 1-6 hours.

7. The molding method according to claim 1, characterized in that, In step S4, the anti-over-sulfurization temperature threshold is 160-165 ℃.

8. The molding method according to claim 1, characterized in that, In step S4, the external water circulation system includes a thermocouple, a temperature controller, a water circulation pump, a cooling device, and a conduit; wherein the thermocouple is attached to the surface of the internal insulation layer and is connected in sequence to the temperature controller and the water circulation pump, and the water circulation pump and the cooling device are connected to the internal cavity through the conduit.

9. The molding method according to claim 1, characterized in that, In step S4, the circulating cooling water circulates through the inlet and outlet located in the internal cavity; the temperature of the circulating cooling water is controlled at 40-80℃.

10. The molding method according to claim 1, characterized in that, In step S5, the heating and curing temperature is 200-250℃, and the time is 2-8 hours.

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