Large-size high-strength heat prevention and insulation rocket end cap and manufacturing method thereof

Abstract

The invention relates to the technical field of rocket manufacturing, and discloses a large-size high-strength heat prevention and insulation rocket end cap and a manufacturing method thereof. According to the method, low-volatile-matter hot-melt phenolic resin impregnated fiber prepreg is adopted as a raw material, and under the condition of a single-face mold, the risk of internal gas retention in the forming process is reduced through staged laying, active building of interlayer exhaust channels and an intermittent compaction technology with the temperature lower than the resin gel temperature; and in the curing stage, a multi-layer collaborative exhaust packaging structure and a vacuum bag are matched, so that residual gas in the product is effectively exhausted under the action of pressure. Through collaborative design of a material system and paving, exhausting, compacting and curing processes, low-porosity forming of the large-size thick-wall rocket end cap is achieved, and the method is suitable for manufacturing of the large-size heat-proof and heat-insulation composite material end cap with a complex structure.

Description

Technical Field

[0001] This invention relates to the field of rocket manufacturing technology, specifically to a nose cone for launch vehicles and its manufacturing method, and more particularly to a manufacturing process for a low-porosity, heat-insulating integrated composite material suitable for large-size, complex-configuration nose cones. Background Technology

[0002] As the foremost component of a launch vehicle, the nose cone must withstand aerodynamic heating and mechanical loads, requiring materials with high strength, heat insulation, and low density. Currently, the mainstream technical solution in this field typically employs a high-silica glass fiber cloth / acetaminophen solvent prepreg system, and uses high-temperature hot compaction to reduce volatiles and porosity.

[0003] However, in larger and thicker end cap products, the number of hot pressing cycles and the high hot pressing temperature can easily lead to premature resin gelation, affecting the subsequent laying and final curing quality. Furthermore, it is difficult to consistently obtain low porosity products under single-sided mold autoclave process conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a large-size, high-strength, heat-insulating rocket nose cap and its manufacturing method. By selecting the material system, actively venting during the laying stage, low-temperature intermittent compaction, and a synergistic venting and encapsulation structure, the low-porosity molding of the large-size, thick-walled nose cap is achieved.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for manufacturing a large-size, high-strength, heat-resistant rocket nose cap includes the following steps: a) Raw material preparation: Prepreg made of fiber fabric impregnated with low-volatile hot-melt phenolic resin is selected as the molding raw material; b) Laying and forming: The prepreg is laid on a single-sided mold in a predetermined layering sequence to form an end cap preform; c) Staged venting and compaction: During the laying process, the laid multi-layer prepreg structure is periodically vented to form a venting channel structure inside the preform to connect the layers. As the thickness of the preform gradually increases, intermittent compaction is carried out at a temperature lower than that of the hot-melt phenolic resin gel to bond the layers together and promote gas discharge. d) Encapsulation and curing: After the preform is laid, a release layer, an exhaust control layer and an air permeable layer are sequentially set on the surface of the preform to form a multi-layer synergistic exhaust structure. After being covered with a vacuum bag for vacuum sealing, it is placed in a pressure curing environment to complete the curing and molding, thereby producing the large-size high-strength heat-insulating rocket tip cap. The exhaust control layer includes at least a porous isolation layer and a directional breathable layer, and the breathable layer may include a breathable felt layer.

[0006] Preferably, the hot-melt phenolic resin is a solvent-free hot-melt phenolic resin system, which produces fewer volatile components during the curing process than solvent-based phenolic resin systems.

[0007] Preferably, the exhaust channel structure is formed by performing partial penetration treatment, partial removal treatment and / or molding interval treatment on the laid multi-layer prepreg structure to shorten the exhaust path of the gas inside the preform.

[0008] Preferably, the temperature of the intermittent compaction is lower than the gel temperature of the hot-melt phenolic resin, so that the resin is in a flowable but uncured state.

[0009] Preferably, the intermittent compaction is achieved by a combination of heating and vacuum or external pressure.

[0010] Preferably, the multi-layer synergistic exhaust structure includes at least a porous isolation layer and a directional breathable layer, and may further include a breathable felt layer for pressure equalization or auxiliary exhaust, wherein: The porous isolation layer is used to restrict resin migration; The directional permeable layer is used to guide gas out into the vacuum channel.

[0011] Preferably, the single-sided mold is a female mold or a male mold.

[0012] A large-size, high-strength, heat-insulating rocket nose cap, which is manufactured by the above-described method.

[0013] Preferably, the end cap is a multi-layer composite structure, and its interior is provided with an exhaust channel structure for connecting the layers.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1) A low-volatile hot-melt phenolic resin system is used to reduce the source of internal gas from the material source; 2) By constructing venting channels in the layup and coordinating with low-temperature intermittent compaction, the gas discharge path is shortened, reducing the risk of porosity. 3) The surface exhaust system, consisting of a porous isolation layer and a directional permeable layer, improves the gas escape efficiency during the curing stage and is suitable for single-sided mold autoclave processes. Attached Figure Description

[0015] To illustrate the technical solutions in the embodiments of the present invention or the prior art more specifically and intuitively, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0016] Figure 1 This is a schematic flowchart of the manufacturing method of the present invention; Figure 2 This is a schematic diagram of a single-sided mold and precast structure; Figure 3 This is a schematic diagram of the hierarchical structure of the collaborative exhaust encapsulation.

[0017] In the diagram: 1—Mold; 2—Preform; 3—Demolding layer; 4—Porous isolation layer; 5—Oriented breathable layer; 6—Breathable felt; 7—Vacuum bag. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] Implementation Method 1 (1) Raw material preparation: The reinforcing fiber fabric prepreg impregnated with hot melt phenolic resin is selected as the raw material.

[0020] (2) Mold preparation and laying: Apply release agent to the single-sided mold 1 (male or female mold) and lay it according to the design layering scheme to form the precast body 2.

[0021] (3) Stepped paving and active air venting: During the paving process, interlayer air venting channels are periodically formed, and low-temperature gap hot compaction is carried out when the cumulative paving thickness reaches the predetermined range. The low-temperature gap hot compaction temperature is controlled at 55℃~65℃ to soften the resin, bond the interlayer and expel air bubbles, while retaining the process window.

[0022] (4) Vacuum bag sealing and surface venting system: After the preform is laid, the release layer 3, the porous isolation layer 4, the directional air permeable layer 5 and the air permeable felt layer 6 are laid in sequence on the surface of the preform 2, and then covered with a vacuum bag 7 for sealing. The porous isolation layer 4 is used to limit resin migration, and the directional air permeable layer 5 is used to guide the gas to the vacuum channel for discharge and reduce the risk of resin blockage.

[0023] (5) Autoclave curing: Place the packaged mold assembly into the autoclave and complete the curing according to the set curve. The pressure is applied evenly to the surface of the product through the vacuum bag 7. Combined with the internal exhaust channel and the surface exhaust system, the volatiles and residual gases are removed.

[0024] Example 1 (Engineering verification type, including curing curve and Table 1) Example 1: Prepare a rocket tip cap of a certain type with a diameter of 1.5 m and a maximum thickness of 15 mm.

[0025] 1) Materials: High-strength S-glass fiber plain weave cloth with a surface density of 180 g is impregnated with hot-melt barium phenolic resin with a resin content of 40±3% to prepare hot-melt prepreg.

[0026] 2) Mold: A female mold is used as a single-sided mold 1, and prepreg is laid on the surface of the mold.

[0027] 3) Laying and compaction: After every 5 layers, use a fine needle with a diameter of 0.4 mm to make holes in a 100 mm × 100 mm grid, with the holes penetrating the 5 layers; when the thickness reaches 3 mm (20 layers), cover with an infrared heating blanket and heat-compact at 60℃ and vacuum pressure of 0.09 MPa for 20 minutes.

[0028] 4) Encapsulation: After the installation is completed, lay out the release layer 3, the porous isolation layer 4, the nylon one-way breathable membrane (as the directional breathable layer 5), the breathable felt layer 6, and the vacuum bag 7 in sequence and seal them.

[0029] 5) Autoclave Curing: The sealed mold assembly is placed in an autoclave and cured according to the following curve: the temperature is increased to 125℃ at 1.5℃ / min and held for 30 min, then increased to 185℃ at 1℃ / min and held for 180 min, with a pressure of 0.6 MPa throughout. Finally, the assembly is cooled to below 60℃ in the furnace and depressurized to obtain the required large-size, high-strength, heat-insulating integrated end cap. The properties of the composite material are shown in Table 1.

[0030]

[0031] Example 2 (Mid-size end cap and process window variation) Prepare a rocket nose cap with a diameter of approximately 1.0 m and a maximum thickness of approximately 10 mm.

[0032] 1) Material: Reinforcing fiber fabric prepreg with hot-melt phenolic resin, with resin content controlled at 38% to 45%.

[0033] 2) Laying: Lay the precast body 2 layer by layer on the single-sided mold 1.

[0034] 3) Venting channels and compaction: During the laying process, interlayer venting channels are periodically formed, and multiple intermittent compaction is carried out under conditions below the resin gel temperature.

[0035] 4) Encapsulation and curing: The layers are encapsulated in the following order: release layer 3 / porous isolation layer 4 / directional breathable layer 5 / breathable felt layer 6 / vacuum bag 7, and cured in a pressure curing environment.

[0036] The resulting end cap has good interlayer bonding and controlled porosity, meeting the usage requirements.

[0037] Example 3 (Large-size thick-walled end cap and venting method variation) Prepare a large-sized, thick-walled rocket nose cap with a diameter of approximately 1.8 m and a maximum thickness of approximately 18 mm.

[0038] 1) Material: Low volatile hot-melt phenolic resin prepreg for reinforcing fiber fabric, resin content 40±5%.

[0039] 2) Laying: Laying on the single-sided mold 1 to form the preform 2.

[0040] 3) Exhaust channel construction: During the tiling process, a multi-layer exhaust channel structure is formed through molding interval treatment and / or local removal treatment.

[0041] 4) Low-temperature intermittent compaction: Intermittent compaction is performed multiple times at a temperature below the resin gelation temperature to improve the density of thick-walled structures.

[0042] 5) Encapsulation and curing: The product is encapsulated using a release layer 3, a porous isolation layer 4, a directional breathable layer 5, a breathable felt layer 6, and a vacuum bag 7, and then cured in a pressure curing environment.

[0043] The resulting large-size, thick-walled end caps are stably molded and meet the requirements of engineering applications.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for manufacturing a large-size, high-strength, heat-resistant rocket nose cap, characterized in that, Includes the following steps: a) Raw material preparation: Prepreg made of fiber fabric impregnated with low-volatile hot-melt phenolic resin is selected as the molding raw material; b) Laying and forming: The prepreg is laid on a single-sided mold (1) in a predetermined layering sequence to form an end cap preform (2). c) Staged venting and compaction: During the laying process, the laid multi-layer prepreg structure is periodically vented to form a venting channel structure for connecting the layers inside the preform (2). As the thickness of the preform (2) gradually increases, intermittent compaction is carried out under conditions lower than the temperature of the hot melt phenolic resin gel to make the layers bond and promote gas discharge. d) Encapsulation and curing: After the preform (2) is laid, a release layer (3), an exhaust control layer and a breathable layer are sequentially set on the surface to form a multi-layer synergistic exhaust structure. After being covered with a vacuum bag (7) for vacuum sealing, it is placed in a pressure curing environment to complete the curing and molding, thereby obtaining the large-size high-strength heat-insulating rocket end cap. The exhaust control layer includes at least a porous isolation layer (4) and a directional breathable layer (5), and the breathable layer may include a breathable felt layer (6).

2. The manufacturing method as described in claim 1, characterized in that, The hot-melt phenolic resin is a solvent-free hot-melt phenolic resin system, and the volatile components generated during its curing process are lower than those of solvent-based phenolic resin systems.

3. The manufacturing method as described in claim 1, characterized in that, The exhaust channel structure is formed by performing local penetration treatment, local removal treatment and / or molding interval treatment on the laid multi-layer prepreg structure to shorten the exhaust path of the gas inside the preform (2).

4. The manufacturing method as described in claim 1, characterized in that, The temperature of the intermittent compaction is lower than the gel temperature of the hot-melt phenolic resin, so that the resin is in a flowable but uncured state.

5. The manufacturing method as described in claim 1 or 4, characterized in that, The intermittent compaction is achieved through the combined action of heating and vacuum or external pressure.

6. The manufacturing method as described in claim 1, characterized in that, The multi-layer synergistic exhaust structure includes at least a porous isolation layer (4) and a directional breathable layer (5), and may further include a breathable felt layer (6) for pressure equalization or auxiliary exhaust, wherein: The porous isolation layer (4) is used to restrict resin migration; The directional permeable layer (5) is used to guide the gas to be discharged into the vacuum channel.

7. The manufacturing method as described in claim 1, characterized in that, The single-sided mold (1) is either a female mold or a male mold.

8. A large-size, high-strength, heat-insulating rocket nose cap, characterized in that, The rocket tip cap is manufactured by the manufacturing method described in any one of claims 1 to 7.

9. The large-size, high-strength, heat-resistant rocket nose cap as described in claim 8, characterized in that, The end cap has a multi-layer composite structure, and its interior is provided with an exhaust channel structure for connecting the layers.

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