Method of forming erosion resistant engine case thermal shield head

Abstract

The application discloses a kind of erosion-resistant engine shell heat-insulating seal head forming methods, heat-insulating seal head includes by inside and outside heat-insulating rubber layer, erosion-resistant layer and metal joint, wherein, erosion-resistant layer is clamped in heat-insulating rubber layer, heat-insulating rubber layer is divided into front seal head heat-insulating layer and rear seal head heat-insulating layer, the insulating rubber layer is also provided with seal head cover layer, the heat-insulating rubber layer, erosion-resistant layer, seal head cover layer are extended to cylinder section by metal joint, the forming method includes the following steps: step 1) front seal head heat-insulating layer laying forming;Step 2) erosion-resistant layer forming;Step 3) rear seal head heat-insulating layer laying forming;Step 4) seal head cover layer laying forming;Step 5) seal head cover layer and seal head bottom layer forming, the present application solves the problem that the prior art erosion-resistant layer is short and cannot extend to the cylinder portion, also solves the problem of the inner layer tension effect after the rocket engine shell is injected and cooled and shrunk, reduces the strain concentration level of engine end under high temperature during engine operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite materials, in particular to a rocket engine shell. BACKGROUND

[0002] With the development of the composite material industry, the solid rocket engine shell combustion chamber material is constantly updated, gradually replacing the original metal material with a large proportion of composite material. Due to the high specific strength, specific stiffness and superior internal pressure resistance of the composite material. The main functions of the engine adiabatic head are: preventing high-temperature gas from burning the shell structure winding layer, buffering the stress transmission when the propellant burns, and sealing the entire engine shell; and the adiabatic head is the place with the largest internal pressure of the entire engine, and has high requirements for its structural strength, ablation resistance and erosion resistance.

[0003] At present, the mainstream engine shell adiabatic head mainly uses EPDM as the main raw material, and an anti-erosion layer (the anti-erosion layer has high hardness, and the anti-erosion layer is a preform, and the overall installation and positioning is difficult) is added to the back surface area of the metal joint of the head. For example, a rocket engine shell composite material adiabatic head manufacturing method in the prior art, its publication number is: CN112297461A, and the publication date is: 2021-02-02, which is difficult to form an integral rear head anti-erosion layer to improve the anti-erosion ability of the shell rear head area. How to form the anti-erosion layer to the cylinder segment is a problem that everyone wants to solve. Why do we need to extend the anti-erosion layer: During the propellant combustion process of the solid rocket engine shell combustion chamber, a relatively large erosion force is generated at the tail of the engine. EPDM rubber has certain ablation resistance and heat insulation capacity, but the anti-erosion ability is poor. The anti-erosion layer has strong ablation resistance and anti-erosion ability, but the heat insulation capacity is general. Therefore, an anti-erosion layer needs to be added between the adiabatic layer of the shell tail to improve the anti-erosion ability of the engine combustion chamber structure layer during the engine combustion chamber operation. Some special type engine shells have high erosion force during propellant combustion, so the requirement for the erosion resistance of the engine tail is also high. The common process for adiabatic forming of the domestic head is die pressing process, and the anti-erosion layer can only be pasted to the curvature area and cannot be formed in the straight cylinder segment (if the anti-erosion layer is pasted to the straight cylinder segment, it is easy to deform during die pressing). The hot press tank process forms a relatively uniform pressure surface, which can ensure the thickness of the anti-erosion layer (the die pressing process cannot guarantee it). The extension of the anti-erosion layer to the cylinder segment can improve the ablation resistance, pressure resistance and anti-erosion ability of the engine tail, and improve the safety factor of the rocket / missile engine shell. SUMMARY

[0004] To address the shortcomings of existing technologies, this invention provides a method for forming an insulating head for an erosion-resistant engine casing. This method solves the problem of short erosion-resistant layers in existing technologies, which cannot extend to the cylinder body. It also addresses the issue of tension in the inner layer of the rocket engine casing after propellant injection and cooling contraction, thereby reducing the strain concentration level at the engine end under high temperatures during engine operation.

[0005] The objective of this invention is achieved as follows: a method for forming an erosion-resistant engine housing insulation head, the insulation head comprising, from the inside out, an insulation rubber layer, an anti-erosion layer, and a metal joint, wherein the anti-erosion layer is sandwiched within the insulation rubber layer, the insulation rubber layer is divided into a front end insulation layer and a rear end insulation layer, characterized in that a cover layer is further provided within the insulation rubber layer, and the insulation rubber layer, the anti-erosion layer, and the cover layer all extend to the cylindrical section from the metal joint, the forming method comprising the following steps:

[0006] Step 1) Laying and molding the front end heat insulation layer: Place the metal joint in the lower mold, lay the rubber layer, and brush the adhesive on the corresponding bonding areas of the metal joint and the front end heat insulation layer. When laying, extend from the metal joint to the cylinder section. After laying, use the autoclave process for pre-curing.

[0007] Step 2) Forming the erosion layer: Apply adhesive to the surface of the erosion layer and the front end heat insulation layer. The erosion layer also extends from the metal joint to the cylinder section. After placing the erosion layer, make a vacuum bag and vacuum it. Then lay a rubber layer on the surface and pre-cur it using a thermostatic can process.

[0008] Step 3) After the end cap insulation layer is laid and formed, the surface of the rubber layer on the anti-erosion layer is polished and cleaned, adhesive is applied, and then the rubber layer is laid. After the laying is completed, it is molded and cured to obtain the bottom layer of the end cap.

[0009] Step 4) Laying and shaping the end cap layer: Apply adhesive to the R-corner area of ​​the end cap mold surface and the rubber surface to be laid. Apply adhesive to the next area after each area is laid, lay and press firmly, and then mold and cure after completion.

[0010] Step 5) Molding the head cover and head bottom layer: Trim and clean the molded parts of the head cover and head bottom layer; First, clean the surface where the head bottom layer and head cover layer are in contact; then, apply a release cloth to the release layer area of ​​the head bottom layer, which is the area where the head cover and head bottom layer are in contact; then, sand the area where the release cloth is not applied, clean it after sanding, let it dry, and finally brush a layer of adhesive on the surface; then clean the surface where the head cover layer and head bottom layer are in contact; sand the area where it is in contact with the bottom layer, clean it after sanding, let it dry, and finally brush a layer of adhesive on the surface; finally, place the head bottom layer into the female mold of the bottom layer mold; lay a layer of EPDM green sheet on the bonding surface of the head bottom layer and head cover layer; then merge the cover layer into the bottom layer; finally, bag and cure, and demold to obtain the erosion resistant engine housing heat insulation head.

[0011] As a further limitation of the present invention, step 1) specifically includes: applying a layer of primer to the bonding area between the metal joint and the front end heat insulation layer, letting it dry, then applying a layer of adhesive, then applying a layer of adhesive to the cleaned rubber surface, and laying the metal joint and the rubber surface adhesive after they have dried. The laying requirement is to pre-extract the bag after the first layer is laid.

[0012] As a further limitation of the present invention, after placing the anti-erosion layer in step 2), a small amount of adhesive is brushed on the surface before vacuuming the vacuum bag.

[0013] As a further limitation of the present invention, after step 3) is completed, an inspection is required, specifically including: inspecting the surface of the insulation layer to be flat, clean and free of dirt, free of excess material, and not allowing obvious bulges, pits, cracks, missing material, looseness, pressure marks, air holes, scratches, or wrinkles; using X-rays to perform non-destructive testing on the insulation layer to check for debonding.

[0014] As a further limitation of the present invention, step 4) specifically involves: taking out the sealed packaged rubber, cleaning it with medical degreased gauze soaked in ethyl acetate chemical reagent at least twice until the surface is clean and dust-free, and drying it for at least 15 minutes. Apply adhesive to the R-corner area of ​​the mold surface of the cover layer, only applying it to the R-corner and the middle of the material sheet, and drying it for 3-5 minutes. Then, lay it on the surface and press it until it is slightly concave. Apply adhesive to the next area after laying one area. Press the mold firmly, with an overlap of 10-15mm between the rubber pieces. Measure with calipers. After laying, it needs to be molded and cured.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) The heat-insulating head manufactured by the present invention can withstand 3000℃ ablation for about 3 minutes, which can meet the requirements of solid engine casing combustion chamber;

[0017] (2) The heat insulation head manufactured by the present invention has higher quality than the traditional solution, with the anti-erosion layer extending to the cylinder section area, higher strength, stronger anti-erosion ability, and stronger ablation resistance, thereby improving the engine operating safety factor and improving the engine working stability.

[0018] (3) The heat insulation head manufactured by the present invention adopts a multi-stage pre-compression molding scheme, which can ensure the thickness of each material area and is easier to meet the relevant design thickness requirements of various models of products than the one-piece head molding scheme.

[0019] (4) The bonding quality between the heat-insulating head cover layer and the bottom layer manufactured by the present invention is higher than that of the traditional head molding method;

[0020] (5) The thermal insulation head manufactured by the present invention has a tensile strength and shear strength of more than 3.0 MPa between the metal, thermal insulation and erosion-resistant layers, which is higher than that of the traditional one-piece molding process.

[0021] (6) This invention is applicable to the fabrication of all solid rocket motor casing heads, and has a wider range of applications. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a view of the external shape of the heat-insulating head obtained by the present invention.

[0024] Figure 2 This is a cross-sectional view of the thermally insulating head obtained by the present invention.

[0025] Figure 3 This is a mold used for fabricating the bottom layer of the end cap in this invention.

[0026] Figure 4 This is a mold used for manufacturing the end cap layer in this invention.

[0027] Figure 5 This is a schematic diagram of the application and adhesive application of the end cap layer in this invention.

[0028] The components are: 1. Head cover layer, 2. Rear head insulation layer, 3. Erosion resistant layer, 4. Front head insulation layer, 5. Metal joint, and 6. Head bottom layer. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] like Figures 1-2 As shown, the end cap obtained by the present invention includes, from the inside out, an end cap cover layer 1, a rear end cap insulation layer 2, an anti-erosion layer 3, a front end cap insulation layer 4, and a metal joint 5. The anti-erosion layer 3 mainly provides the engine with resistance to propellant combustion erosion and ablation, while the end cap cover layer 1 mainly reduces the strain concentration level at the engine end under high temperature during engine operation.

[0031] The working environment requirements of the heat-insulating head are mainly as a heat-insulating structural layer for the combustion chamber of the engine casing. Its main function is to prevent the combustion chamber casing from being burned by high-temperature combustion gases, to prevent the casing strength from decreasing due to excessive temperature, and to reduce the weight of the head as much as possible, thereby reducing the weight of the engine casing.

[0032] The material selection plan is as follows:

[0033] Table 1 Properties of EPDM Rubber

[0034] Density (g / cm 3 ) Oxyacetylene wire ablation rate (mm / s) Tensile strength (MPa) Elongation at break (%) Index requirement ≤1.1 ≤0.12 ≥3.5 ≥200

[0035] Ethylene propylene diene monomer (EPDM) rubber has excellent comprehensive properties, making it a good base material for thermal insulation layers. EPDM rubber has low density and high elongation, exhibiting good ablation resistance and thermal insulation properties. It can be stored for a long time and has excellent chemical compatibility with propellants.

[0036] Table 2. Properties of ablation-resistant braided fabrics

[0037] Density (g / cm 3 )]]> Oxyacetylene wire ablation rate (mm / s) Tensile strength (MPa) Elongation at break (%) Index requirement ≤1.40 ≤0.04 ≥15 ≥15

[0038] The ablation-resistant braided fabric (anti-erosion layer) has a low oxyacetylene ablation rate and high tensile strength, which can effectively improve the propellant erosion resistance of the entire rear end of the engine, thereby improving the engine's operational safety factor and working stability; however, the ablation-resistant braided fabric has high hardness and is difficult to position.

[0039] The molding process is as follows:

[0040] Step 1) Front end heat insulation layer 4 laying and molding process: Apply a layer of metal-rubber bonding primer Chemlock 205 to the bonding area of ​​the metal joint 5 (let it dry for 15 minutes). After drying, apply a layer of AE-2 (metal-rubber adhesive). Then apply a layer of AE-2 to the cleaned 1mm rubber surface. After the adhesive on the metal joint 5 and the rubber surface has dried, lay the metal joint 5. The laying requirement is that the first layer is laid and the bag is pre-extracted. The pre-extraction time is ≥15 minutes, and the vacuum degree in the empty bag reaches ≤-0.085MPa. Starting from point a, the calculation is performed by pulling out one tube after each layer is laid, with a time of ≥15 minutes. After the rubber insulation layer 4 of the front end cap is laid, a vacuum bag is made to pre-form the insulation layer before the anti-erosion layer 3. The vacuum bag curing method can reduce the investment in molding molds, reduce product manufacturing costs, and ensure that the surface of the insulation rubber before the anti-erosion layer 3 is close to the theoretical surface, so that it fits well with the subsequent anti-erosion layer 3. After pre-forming, a surface template can be used for matching and testing, and the protruding positions are ground to ensure that the surface fits completely with the subsequent anti-erosion layer 3.

[0041] Step 2) Anti-erosion layer 3 laying and molding process: Brush a small amount of AE-3 (carbon material and rubber adhesive) on the surface of anti-erosion layer 3, and then dry the surface of anti-erosion layer 3 for 3-5 minutes; install anti-erosion layer 3 into front end heat insulation layer 4, and then lay another layer of rubber heat insulation layer on the surface of anti-erosion layer 3. After completion, make a vacuum bag for pre-forming.

[0042] Step 3) Rear end heat insulation layer 2 molding process: The rubber heat insulation layer surface on the erosion layer 3 is polished, cleaned with ethyl acetate, coated with AE-4 (heat insulation semi-cured sheet and cured sheet adhesive), and then the heat insulation rubber of the rear end heat insulation layer 2 is laid. After laying, it is molded and cured to obtain the end cap bottom layer 6.

[0043] Step 4) Head cap layer 1 molding process: Apply a small amount of AE-1 adhesive (adhesive to improve interface adhesion) to the R-corner area of ​​the special lower mold surface for the cap layer, and at the same time apply AE-1 adhesive to the rubber surface. Apply adhesive to the next area after each area is laid. Press the mold to lay and compact it. After the laying is completed, close the mold and cure it.

[0044] Step 5) Insulation bonding molding process of end cap 1 and rear end cap insulation layer 2: Trim and clean the end cap 1 and end cap bottom layer 6 molded parts, clean the surface of the bottom layer in contact with the male mold, then apply release cloth to the release layer area, then sand the area without release cloth (sand with a file), clean with ethyl acetate after sanding, let it dry, and finally brush a layer of AE-4 on the surface; clean the surface of the cover layer in contact with the female mold, sand the area in contact with the bottom layer (sand with a file), clean with ethyl acetate after sanding, let it dry, and finally brush a layer of AE-4 on the surface. The bottom layer is placed in the female mold of the bottom layer mold. A 0.5mm thick EPDM green sheet is laid on the bonding surface of the bottom layer and the top layer. Then the top layer is merged into the bottom layer. Finally, it is bagged and cured. The adhesion performance between the green sheet and the semi-cooked sheet is better. Therefore, a layer of green sheet is sandwiched between the pre-formed bottom layer and the top layer and coated with the green sheet and semi-cooked sheet adhesive. Moreover, the autoclave molding process can ensure that the pressure is evenly distributed on the inner surface of the product. Compared with the compression molding process, the semi-cooked sheet compression molding may cause the rubber to be not compacted and loose.

[0045] The main process of laying the rubber insulation layer is as follows:

[0046] The process mainly consists of the following five parts: 1. Cutting and chamfering; 2. Cleaning; 3. Applying adhesive; 4. Laying; 5. Removing bubbles. In order to ensure the bonding quality of the rubber shell after vulcanization, the specific process is as follows.

[0047] 1) Divide the sheet material between the same layer of the end cap into 8 equal parts to design the layering and cutting drawing, and then perform CAD layout and cutting according to the cutting drawing.

[0048] 2) Overlapping should be done in the direction of airflow, with no overlap at the circumferential seams. Seams should be staggered by at least 2mm, and the overlap should be 10-15mm. Overlapped areas should be beveled to ensure consistent product thickness and meet the requirements for insulation layer construction. Apply the specified J-1 adhesive between rubber layers and bond them together, ensuring no rubber bubbles appear after bonding.

[0049] 3) During the fabrication of the insulation layer structure, there should be no insulation material debris or other foreign matter between the sheets. Foreign matter shall be treated in accordance with the QJ2850 standard. The insulation fabrication environment requires an on-site temperature of 24±10℃ and a relative humidity of ≤75%. The temperature and humidity shall be recorded daily as required.

[0050] 4) Record parameters such as the adhesive application time, drying time, and bonding time for each insulation layer. The thickness of each insulation layer must be measured, the amount of adhesive applied, and the total weight of the insulation layer and the weight of the adhesive after bonding are recorded.

[0051] To ensure that the thermal insulation rubber properties of the front and rear end caps are not affected by the release agent, the release agent is prohibited. The mold surface is sintered with polytetrafluoroethylene, and a good demolding effect can be achieved without the use of the release agent.

[0052] The invention will be further illustrated below with specific examples.

[0053] A method for forming an erosion-resistant engine casing heat insulation head includes the following steps.

[0054] 1) Prepare the joint. Spray the surface of the metal joint 5 with 40-mesh quartz sand. Sandblasting can improve the bonding strength between the metal joint 5 and the insulation layer.

[0055] 2) Apply a small amount of adhesive to the surface of the female mold of the bottom layer 6 of the head, and at the same time apply the first layer of rubber material. Let it dry for about 5 minutes, then lay it on the surface of the mold and press it firmly. After each position is laid, apply adhesive to the next position, lay it firmly, and weigh it before and after applying adhesive. This is a rubber-to-rubber interface adhesive application operation.

[0056] 3) Apply a layer of Chemlock 205 primer to the bonding area of ​​metal connector 5 (i.e. the area where metal connector 5 contacts the rubber) and let it dry for 15 minutes. After it dries, apply a layer of AE-2 and let it dry for 15 minutes.

[0057] 4) Remove the sealed rubber package and clean it with medical degreased gauze soaked in ethyl acetate (at least twice) until the surface is clean and dust-free, and let it air dry for at least 15 minutes.

[0058] 5) Apply a layer of AE-2 to the cleaned rubber surface, let it dry for 15 minutes, then place it into the joint. Press the dried rubber onto the joint surface firmly (until the surface is slightly concave). Lay the remaining pieces in numerical order. Apply a small amount of AE-1 adhesive to the R-corner area of ​​the lower mold surface, and apply it to one of the pieces at the same time. Let it dry for 3-5 minutes, then lay it on the surface and press it firmly until it is slightly concave. After laying one area, apply adhesive to the next area. Press the mold firmly (overlap 10-15mm between rubber pieces, measure with calipers). This is the rubber-to-rubber interface adhesive application operation.

[0059] 6) During the above-mentioned laying process, after each layer is laid, check the condition of the rubber surface and use a trowel to compact all areas. If it is found that it is not compacted, use a steel needle to puncture the residual air bubbles during laying and compact it. If it cannot be compacted, use a syringe to inject an appropriate amount of glue, let it dry for about 5 minutes, and then compact it.

[0060] 7) Front end cap insulation layer 4 insulation pre-curing: Connect to a vacuum system, apply a vacuum pressure below -0.085MPa, and apply an air pressure of 0.5MPa, maintaining this pressure for at least 15 minutes without leakage. Curing parameters:

[0061] I) Pressurize at room temperature to 0.5 MPa at a rate of 0.02 MPa / min, and then heat at room temperature at a rate of 1 °C / min;

[0062] II) Set the medium temperature to 85℃. After the slowest heating thermocouple reaches 80℃, keep it at that temperature for 1 hour.

[0063] III) Set the medium temperature to 95℃. After the slowest heating thermocouple reaches 90℃, keep it at that temperature for 2 hours.

[0064] IV) Set the medium temperature to 135℃. After the slowest heating thermocouple reaches 130℃, keep it at that temperature for 2 hours.

[0065] V) Cool at a rate not exceeding 1°C / min. When the temperature of the thermocouple with the slowest cooling rate drops below 60°C, depressurize. After depressurization, the can can be opened.

[0066] 8) Laying the erosion layer 3: Place the bottom layer of the erosion layer 3 for insulation, brush a small amount of AE-3 on the surface (dry for 3-5 minutes), then brush a small amount of AE-3 on the surface of the erosion layer 3 (dry for 3-5 minutes), place it, make a vacuum bag and vacuum for 2 hours, then lay a 1mm EPDM layer on the surface, set up the vacuum device, and prepare for pre-compression.

[0067] 9) Anti-erosion layer 3 pre-curing, curing parameters:

[0068] I) Pressurize at room temperature to 0.5 MPa at a rate of 0.02 MPa / min, and then heat at room temperature at a rate of 1 °C / min;

[0069] II) Set the medium temperature to 85℃. After the slowest heating thermocouple reaches 80℃, keep it at that temperature for 1 hour.

[0070] III) Set the medium temperature to 95℃. After the slowest heating thermocouple reaches 90℃, keep it at that temperature for 2 hours.

[0071] IV) Set the medium temperature to 135℃. After the slowest heating thermocouple reaches 130℃, keep it at that temperature for 2 hours.

[0072] V) Cool at a rate not exceeding 1°C / min. When the temperature of the thermocouple with the slowest cooling rate drops below 60°C, depressurize. After depressurization, the can can be opened.

[0073] 10) Erosion-resistant layer, 3-layer thermal insulation installation:

[0074] After roughening the surface of the erosion-resistant layer 3 with 80-grit sandpaper and a grinding disc (to improve bonding strength), clean it with ethyl acetate (dry for 3-5 minutes), then lay the rubber, and finally mold it for curing. Before closing the mold, check the mold surface for any unwanted debris. Molding curing parameters:

[0075] (1) The heating rate is 20℃ / h, the room temperature is -80℃, the exhaust is vented once at 80℃, and the pressure is increased to 1MPa after 1h of heat preservation;

[0076] (2) The heating rate is 20℃ / h, from 80℃ to 100℃, and exhausts the gas 3 times at 100℃. After holding the temperature for 1 hour, pressurize to 3MPa.

[0077] (3) The heating rate is 20℃ / h, from 100℃ to 120℃, and exhausts the gas 3 times at 120℃. After holding the temperature for 1 hour, pressurize to 6MPa.

[0078] (4) Heating rate 20℃ / h, 120℃-135℃, hold for 2h;

[0079] (5) Cooling rate 20℃ / h, 135℃-50℃, depressurize, remove from furnace, and obtain the bottom layer of the head 6.

[0080] 11) Inspection of the bottom layer of the end cap: The surface of the insulation structure must be flat, clean, and free of contaminants and excess material. Obvious bulges (air traps), pits, cracks, missing material, looseness, dents, pores, scratches, and wrinkles are not permitted. Non-destructive testing of the insulation layer is performed using X-rays. Check for any debonding.

[0081] 12) Head Cap Layer 1 Laying: Remove the sealed and packaged rubber, and clean it with medical degreased gauze soaked in ethyl acetate (at least twice) until the surface is clean and dust-free. Allow it to dry for at least 15 minutes. Apply a small amount of AE-1 adhesive to the R-corner area of ​​the lower mold surface of Head Cap Layer 1, simultaneously applying it to the 15mm R-corner area and two points at the top and bottom of the fan-shaped surface, as detailed below. Figure 5 As shown, due to the poor self-adhesion of EPDM raw rubber sheets, to prevent the sheets from shifting during insulation installation, a high-adhesion adhesive needs to be applied to the surface of the sheets for installation. However, the adhesive can have a negative effect on the bonding of the rubber itself. Therefore, when installing the sheets, it is necessary to apply as little adhesive as possible while ensuring they are firmly bonded. Thus, a five-point application method is used during the insulation installation process. After drying for 3-5 minutes, the sheets are applied to the surface and pressed until slightly indented. After each area is completed, the next area is applied. The sheets are then molded and pressed firmly (the overlap between rubber sheets is 10-15mm, measured with calipers). This is an adhesive application operation at the rubber-to-rubber interface. After installation, molding and curing are required.

[0082] 13) Molding and curing of the head cover layer 1, curing parameters:

[0083] The heating rate is 20℃ / h, the room temperature is -80℃, the exhaust is vented once at 80℃, and after holding the temperature for 1 hour, the pressure is increased to 1MPa.

[0084] The heating rate is 20℃ / h, the temperature range is 80℃-100℃, the exhaust is 3 times at 100℃, and the pressure is increased to 3MPa after holding the temperature for 1 hour.

[0085] The heating rate is 20℃ / h, from 100℃ to 120℃, and exhausts the gas 3 times at 120℃. After holding the temperature for 1 hour, the pressure is increased to 6MPa.

[0086] Heating rate 20℃ / h, 120℃-135℃, hold for 2h;

[0087] Cooling rate 20℃ / h, 135℃-50℃, depressurize, remove from furnace, and obtain head cover layer 1.

[0088] 14) End cap cover layer 1, end cap bottom layer 6-piece mold laying

[0089] Clean the surface of the end cap bottom layer 6 that contacts the male mold of the end cap bottom layer 6. Then, apply release cloth to the release layer area. Next, sand the area where the release cloth was not applied (using a file). After sanding, clean with ethyl acetate, let it dry, and finally brush a layer of AE-4 on the surface. Clean the surface of the end cap top layer 1 that contacts the female mold of the end cap top layer 1. Sand the area that contacts the end cap bottom layer 6 (using a file). After sanding, clean with ethyl acetate, let it dry, and finally brush a layer of AE-4 on the surface. Combine the end cap bottom layer 6 and the end cap top layer 1 (apply another layer of rubber to the bonding area to improve the bonding strength) and place them into the female mold of the bottom layer mold. Finally, perform final curing.

[0090] 15) The entire head is cured using an autoclave process. The curing parameters are as follows:

[0091] The pressure was increased to 0.5 MPa at room temperature at a rate of 0.02 MPa / min, and the temperature was increased at room temperature at a rate of 1 °C / min.

[0092] The medium temperature is set to 95℃. After the slowest heating thermocouple reaches 90℃, it is kept at that temperature for 1 hour.

[0093] The medium temperature is set to 140℃. When the slowest heating thermocouple reaches 135℃, it is kept at that temperature for 3 hours.

[0094] Cool at a rate not exceeding 1°C / min. Once the temperature of the thermocouple, which cools the slowest, drops below 60°C, depressurize. The can be opened after depressurization.

[0095] 16) Demolding to obtain the final shell insulation head.

[0096] Testing revealed that the thermal insulation head manufactured by this invention can withstand ablation at 3000℃ for approximately 3 minutes, meeting the requirements for use in the combustion chamber of a solid rocket motor casing. Compared to traditional methods, the thermal insulation head manufactured by this invention features an anti-erosion layer 3 extending into the cylinder section, resulting in higher strength, stronger erosion resistance, and greater resistance to ablation, thereby improving the engine's operational safety and stability. The thermal insulation head manufactured by this invention employs a multi-stage pre-compression molding process, ensuring the thickness of each material region and making it easier to meet the design thickness requirements of various product models compared to a one-piece head molding method. The bonding strength between the cover layer 1 and the bottom layer of the thermal insulation head manufactured by this invention is higher than that of traditional head molding. The thermal insulation head manufactured by this invention exhibits a tensile strength and shear strength exceeding 3.0 MPa between the metal, thermal insulation, and anti-erosion layers, surpassing traditional one-piece molding processes. This invention is applicable to the manufacture of all solid rocket motor casing heads, offering a wider range of applications.

[0097] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for forming an erosion-resistant engine casing heat-insulating head, the heat-insulating head comprising, from the inside out, an heat-insulating rubber layer, an erosion-resistant layer, and a metal joint, wherein, An erosion-resistant layer is sandwiched within a heat-insulating rubber layer, which is divided into a front end heat-insulating layer and a rear end heat-insulating layer. The key feature is that an end cap layer is also provided within the heat-insulating rubber layer. The heat-insulating rubber layer, erosion-resistant layer, and end cap layer all extend to the cylinder section via metal joints. The erosion-resistant layer is an ablation-resistant braided material. The molding method includes the following steps: Step 1) Laying and molding the front end heat insulation layer: Place the metal joint in the lower mold, lay the rubber layer, and brush the adhesive on the corresponding bonding areas of the metal joint and the front end heat insulation layer. When laying, extend from the metal joint to the cylinder section. After laying, use the autoclave process for pre-curing. Step 2) Forming the erosion layer: Apply adhesive to the surface of the erosion layer and the front end heat insulation layer. The erosion layer also extends from the metal joint to the cylinder section. After placing the erosion layer, make a vacuum bag and vacuum it. Then lay a rubber layer on the surface and pre-cur it using a thermostatic can process. Step 3) After the end cap insulation layer is laid and formed, the surface of the rubber layer on the anti-erosion layer is polished and cleaned, adhesive is applied, and then the rubber layer is laid. After the laying is completed, it is molded and cured to obtain the bottom layer of the end cap. Step 4) Laying and shaping the end cap layer: Apply adhesive to the R-corner area of ​​the end cap mold surface and the rubber surface to be laid. Apply adhesive to the next area after each area is laid, lay and press firmly, and then mold and cure after completion. Step 5) Molding the head cover and head bottom layer: Trim and clean the molded parts of the head cover and head bottom layer; First, clean the surface where the head bottom layer and head cover layer are in contact; then, apply a release cloth to the release layer area of ​​the head bottom layer, which is the area where the head cover and head bottom layer are in contact; then, sand the area where the release cloth is not applied, clean it after sanding, let it dry, and finally brush a layer of adhesive on the surface; then clean the surface where the head cover layer and head bottom layer are in contact; sand the area where it is in contact with the bottom layer, clean it after sanding, let it dry, and finally brush a layer of adhesive on the surface; finally, place the head bottom layer into the female mold of the bottom layer mold; lay a layer of EPDM green sheet on the bonding surface of the head bottom layer and head cover layer; then merge the cover layer into the bottom layer; finally, bag and cure, and demold to obtain the erosion resistant engine housing heat insulation head.

2. The method for forming an erosion-resistant engine casing heat-insulating head according to claim 1, characterized in that, Step 1) Specifically includes: applying a layer of primer to the bonding area between the metal joint and the front end heat insulation layer, letting it dry, then applying a layer of adhesive, then applying a layer of adhesive to the cleaned rubber surface, and laying the metal joint and rubber surface adhesive after they have dried. The laying requirement is to pre-extract the bag after the first layer is laid.

3. The method for forming an erosion-resistant engine casing heat-insulating head according to claim 1 or 2, characterized in that, Step 2) After placing the erosion-resistant layer, before vacuuming the vacuum bag, brush a small amount of adhesive onto the surface.

4. The method for forming an erosion-resistant engine casing heat-insulating head according to claim 1 or 2, characterized in that, After step 3) is completed, further testing is required, including: checking that the surface of the insulation layer is flat, clean and free of dirt and foreign matter, and that there are no obvious bulges, pits, cracks, missing materials, looseness, pressure marks, air holes, scratches and wrinkles. Use X-rays to perform non-destructive testing on the insulation layer to check for debonding.

5. The method for forming an erosion-resistant engine casing heat-insulating head according to claim 1 or 2, characterized in that, Step 4) Specifically: Take out the sealed packaged rubber, clean it with medical degreased gauze soaked in ethyl acetate chemical reagent at least twice, clean until the surface is clean and dust-free, and let it dry for more than 15 minutes. Apply adhesive to the R-corner area of ​​the mold surface of the cover layer, only brushing the R-corner and the middle of the material sheet, let it dry for 3-5 minutes, and then lay it on the surface, pressing it until it is slightly concave. After laying one area, apply adhesive to the next area. Press the mold firmly, with an overlap of 10-15mm between the rubber pieces. Use calipers to measure. After laying, it needs to be molded and cured.

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