Manufacturing Method of Fully Open Composite Material Shell

Abstract

The present invention discloses a method for manufacturing a fully-open composite shell in the field of aerospace engine technology. The method comprises the following steps: 1) making a composite joint and processing it into a necked end joint and an open end joint; 2) making a core mold; 3) laying a heat insulation layer; 4) preforming the heat insulation layer; 5) installing the joint; 6) inner winding, using carbon fiber soaked in a medium-temperature epoxy resin for winding, adopting a winding method of alternating longitudinal winding and circumferential winding, and adjusting and controlling the fiber tension before winding, and adjusting and controlling the tension in accordance with the requirement of gradually decreasing the tension from the inside to the outside; 7) outer winding, using carbon fiber soaked in a medium-temperature epoxy resin for winding again on the inner winding layer, adopting a circumferential winding method, and adjusting and controlling the fiber tension before winding, and adjusting and controlling the tension in accordance with the requirement of gradually decreasing the tension from the inside to the outside; 8) curing; 9) demoulding; 10) testing. The present invention improves the strength of a fully-open shell.

Description

Technical Field

[0001] The present invention relates to the technical field of aerospace engines, and in particular to a method for manufacturing an engine casing. Background Art

[0002] In the 21st century, the engine casing is the main power unit of various missile weapons and is also widely used in the aerospace field. The casing is characterized by a simple structure. Due to its advantages such as mobility, reliability, and easy maintenance, it is very suitable for the needs of modern warfare and aerospace. However, engine components must withstand high temperatures, high internal pressure requirements, high pressure and various complex loads under chemical atmosphere during operation. Therefore, the temperature and pressure resistance of the engine casing is a technical challenge.

[0003] In the 1960s, composite engine casings were used on American rocket engines. Subsequently, various countries have conducted extensive research on them. Currently, most rocket engines use carbon fiber wrapped epoxy resin composite materials, but their flange joints and other parts still use metal materials. There is room for further improvement in weight reduction, and the bonding strength between metal joints and ablation-resistant insulation layers and winding layers has always been a technical problem in the industry.

[0004] Currently, fully open engine casings are primarily made of metal, which has a high density and results in a heavy engine casing, significantly impacting the rocket's range and speed. Furthermore, metal engine casings consume a lot of fuel, and with the increasing demand for commercial satellites, there's a growing demand for lightweight, high-performance, and low-cost rocket engine casings. To achieve weight reduction, fully open engine casings commonly used in existing technology typically utilize a composite barrel with metal joints. However, due to the thermal expansion mismatch and large modulus difference between metal and composite, the joint between the metal and composite deforms mismatched under temperature or stress changes. Furthermore, the joint between the metal and composite typically requires thickening, resulting in a heavy weight reduction. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a method for manufacturing a fully-open composite material shell. The shell changes the previous situation where the bonding strength between the metal joint and the composite layer is not high. Composite material joints are bonded to the composite shell to improve the body strength and bonding strength, which solves the problem that it is difficult to produce and process fully-open composite material shells under the premise of ensuring reliability and strength.

[0006] The object of the present invention is achieved as follows: A method for manufacturing a fully open composite material shell comprises the following steps:

[0007] Step 1) preparing a composite material joint and processing it into a necked end joint and an open end joint;

[0008] Step 2) making a core mold;

[0009] Step 3) Laying the insulation layer: Laying the insulation layer on the surface of the core mold;

[0010] Step 4) preforming the heat insulation layer by vacuuming and pressurizing the heat insulation layer;

[0011] Step 5) Install the joints: install the necked end joint and the open end joint to the corresponding positions on the core mold;

[0012] Step 6) Inner winding: Winding is performed using carbon fibers soaked in medium-temperature epoxy resin, alternating between longitudinal and circumferential winding. Fiber tension must be adjusted and controlled before winding, with the tension gradually decreasing from the inside out.

[0013] Step 7) Outer winding: The carbon fiber soaked in medium-temperature epoxy resin is wound again on the inner winding layer of the open end. The hoop winding method is adopted. The fiber tension needs to be adjusted and controlled before winding, and the adjustment and control should be carried out according to the requirement of gradually decreasing the tension from the inside to the outside.

[0014] Step 8) Curing: Curing is performed by heating at normal pressure, and the shell wrapping layer and the insulation layer are cured together;

[0015] Step 9) Demolding: remove the shell from the core mold;

[0016] Step 10) Inspection, including dimensional inspection, non-destructive inspection, air tightness inspection and water pressure inspection.

[0017] As a further limitation of the present invention, in step 6), during the winding process, the pole hole where the joint and the head are connected is reinforced, and a reinforcement layer is laid between adjacent longitudinal layers.

[0018] As a further limitation of the present invention, the reinforcement layer is made of plain cloth made of glass fiber material.

[0019] As a further limitation of the present invention, the reinforcement is specifically as follows: during the reinforcement, the equipment keeps rotating, and the two sides of the head column section are used as starting points, and the reinforcement layer is circumferentially laid along the equator toward the polar holes on both sides.

[0020] As a further limitation of the present invention, when wrinkles appear during the laying process of the reinforcement layer, no cutting is done in the area close to the column section, and small cutting is done in the area away from the column section.

[0021] As a further limitation of the present invention, in step 5), during the joint installation, an elastic layer is laid on the joint surface.

[0022] In steps 6) and 7) of the present invention, the fiber tension is first adjusted and controlled before winding to achieve the specified tension accuracy. The specific purposes of doing so are:

[0023] During the actual winding process, if the tension is not detected and adjusted, the tension of the fiber layer will decrease layer by layer, resulting in a loose inside and tight outside situation. This is because the tension of the later wound layer will cause the first wound fiber layer and the inner layer to compress and deform together, making the inner fibers loose. If the appropriate tension is not tested in advance, the fibers on the shell will be loose inside and tight outside, resulting in a large difference in the initial stress of the inner and outer fibers. When the container is pressurized, the fibers cannot be evenly stressed. In severe cases, the inner fibers may wrinkle, blister, deform, and other yielding conditions, which will greatly reduce the shell strength and fatigue performance. Therefore, by testing the tension before winding, it is ensured that the wound fibers meet the requirements and avoid the loose inside and tight outside situation. Specifically, by testing whether the fiber tension meets the requirements, the tension can be adjusted as needed later. However, the prerequisite is to conduct tension testing. Without the tension testing link, subsequent adjustment is even more impossible. In this way, all wound layers can have the same deformation and initial tension from the inside to the outside. When the shell container is pressurized, the fibers can still bear the stress, which improves the container strength and enables the fiber strength to be better developed.

[0024] In order to ensure both the fiber volume content and the fiber utilization coefficient and minimize the degree of fiber wear, the fiber winding tension is controlled layer by layer. When winding the inner layer, the longitudinal winding layer and the circumferential winding layer are alternated. The gradient tension can make the layers of fibers wrapped from the inside to the outside of the shell have the same prestress, so that the overall effect of the composite material can be exerted when the shell is working. From the practical experience of scaled-down shell blasting, it is known that the fiber utilization coefficient of the entire shell wound with the same tension is generally around 70%, while the fiber utilization coefficient of the system-designed gradient tension shell blasting strength can reach more than 85%.

[0025] In order to make the thickness distribution of the head uniform and symmetrical, the present invention lays a reinforcement layer between adjacent longitudinal layers; uses glass fiber cloth as the reinforcement layer instead of non-weft cloth; the warp and weft directions near the pole hole of the head can be strengthened, and the reinforcement is local, that is, limited to the pole hole where the joint is connected to the head; considering the convenience of process implementation, comprehensive reinforcement of the entire head is difficult, and reinforcement near the equator will also bring inconvenience to the construction of the upper skirt. The strength of the entire head is mainly achieved by adjusting the thickness of the head, that is, adjusting the stress balance coefficient ks; glass fiber has higher fracture strain and fracture toughness. Although its strength is lower than that of carbon fiber, it can achieve a mixed positive effect. Reinforcing the carbon fiber shell head with glass cloth will make up for the deficiency of carbon fiber's easy brittle fracture.

[0026] Based on the difference in stiffness of the joint structure in the area with larger strain in the shell, and combined with the accuracy of the actual executable operation position, the front and rear head reinforcement areas are determined. Starting from the two sides of the front and rear head column segments, reinforcement is carried out along the equator towards the polar holes on both sides.

[0027] Compared with the prior art, the present invention has the following beneficial effects.

[0028] The use of an all-composite shell reduces weight and improves container efficiency.

[0029] The use of thermal insulation laying and joint installation followed by laying ensures the bonding of the joint to the thermal insulation and avoids the influence of traditional head compression molding pressure on the joint.

[0030] The optimization of the fully open carbon fiber composite material structure, the optimization of the head and the reinforcement of the opening reduce the weight of the combustion chamber, improve the overall quality of the product, and enhance the overall connection strength of the shell.

[0031] Due to the thermal expansion mismatch and large modulus difference between metal and composite materials, the joints between metal and composite materials deform mismatched under temperature changes or stress changes. In addition, the joints between metal and composite materials generally need to be thickened and are heavier. The shell of the present invention changes the previous situation where the bonding strength between metal joints and composite layers is not high, and uses composite material joints and composite bonding to improve the body strength and bonding strength.

[0032] The winding angle and number of winding layers are determined according to the size of the combustion chamber shell opening, the column section diameter, etc., and the connection between the closing section and the opening section is reinforced to meet the mechanical performance index requirements.

[0033] Through process selection and optimization, control of tension application, design of tension gradient and improvement of winding layer product quality, and mold design optimization to improve product quality and production efficiency, reduce weight and lower costs; under the conditions of cylinder volume and strength, the weight can be reduced by more than 40% compared with traditional shells. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0035] Figure 1 It is a cross-sectional view of the shell of the present invention.

[0036] Figure 2 Schematic diagram illustrating various areas of the housing of the present invention.

[0037] Figure 3 It is a schematic diagram of the molding of the present invention.

[0038] Figure 4 This is a schematic diagram of the joint production in the present invention. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] Existing fiber winding technology and mature processes, combined with the material selection experience of various types of winding shells and launch tube products, the T700 fiber reinforced epoxy resin system is selected for the winding carbon fiber part. The joint design requires material selection. The material system performance data is as follows:

[0041]

[0042] Regarding the product features, the fully open carbon fiber composite combustion chamber adopts a metal core mold, and two fully open carbon fiber composite combustion chambers are formed at one time (the forming diagram is shown in the figure). Figure 3 As shown), after molding, it can be demoulded by cutting it in the middle to obtain two separate fully open carbon fiber composite combustion chambers.

[0043] The joint at the necked end can be directly embedded in the composite material before the first winding. The open end is reinforced by axial layup and circumferential winding. The composite material thread is machined after the product is demoulded. The connection strength can be guaranteed by calculating the composite material thread.

[0044] The process route of the present invention is as follows:

[0045] Composite joint production => core mold manufacturing => insulation layer laying => insulation preforming => interface processing => shrink joint installation => joint surface elastic layer laying => fiber winding => hoop winding reinforcement => curing => demoulding => testing => product delivery.

[0046] The completed shell half section is as follows Figure 1 As shown, the various regions of the cross section are described as follows Figure 2 shown.

[0047] Example 1

[0048] A method for manufacturing a fully open composite material shell comprises the following steps:

[0049] Step 1) Composite material joint production:

[0050] a. Choose carbon fiber unidirectional prepreg and carbon fiber plain weave prepreg;

[0051] b. Cut the materials according to the shape and quantity designed in the expanded drawing and number them;

[0052] c. Lay the layers on the mold according to the designed laying process, with flat laying accounting for 60-90% and whole-package laying accounting for 10-40%. Vacuum exhaust and compaction are performed every 10 layers, and the time is 4 hours.

[0053] d. After the layering is completed, the mold is closed and the temperature and pressure are increased in the hot press to compact and solidify the product;

[0054] e. After cooling and demoulding, the joint blank is machined to the required size according to the design drawings and set aside.

[0055] Step 2) Manufacture of core mold: Manufacture the core mold according to the design drawing and spray polytetrafluoroethylene coating (anti-stick) on the surface.

[0056] Step 3) Laying the insulation layer: Lay 1.2mm thick EPDM rubber and apply a special EPDM adhesive to the overlapped parts of the raw sheets; clean and dry the surface of the bonding parts; Lay the rubber on the column sections and use rubber adhesive to bond the overlapped joints of the rubber on the column sections to the front and rear heads, compact and remove air; Dimensional inspection: Perform dimensional inspection on the rubber heads according to the drawing requirements.

[0057] Step 4) Preforming of the thermal insulation layer: The thermal insulation layer is preformed by vacuuming and pressurizing. Since the metal mold has good structural strength, the thermal insulation can be preformed by vacuuming and pressurizing in an autoclave, which is reliable.

[0058] Step 5) Joint processing: Select materials and process the necked end joints and open end joints according to the drawings.

[0059] Step 6) Installation of the necked end joint: After sandblasting the bonding surface of the necked end joint and applying EPDM adhesive, install it to the corresponding position of the core mold. Use special tooling to position the front and rear joint flange surfaces to constrain the axial and radial displacement of the joint.

[0060] Step 7) Laying the elastic layer on the joint surface: Lay a 0.5mm elastic layer on the joint surface.

[0061] Step 8) Winding: The inner winding is alternately longitudinal and circumferential, and the outer winding is all circumferential, and the outer winding is mainly at the open end; the inner and outer windings are both wound with T700 / 12k carbon fiber impregnated with medium-temperature epoxy resin, the number of yarn sheets is 1, the unfolded width of the yarn sheet is 1.5mm, the number of longitudinal winding layers is 6 layers (T1, T2, T3 are longitudinal layers, and one longitudinal layer is 2 layers), the number of circumferential winding layers is 2 layers (H1, H2, H3, H4, H5, H6 are circumferential layers), the fiber volume content is controlled at about 60%, and the glue content is mainly controlled by the size of the fiber tension of the winding machine.

[0062] The cylinder winding environment requires a temperature of (24±10)℃ and a relative humidity of ≤75%. The temperature and humidity conditions are recorded every 3 hours.

[0063] In order to control the fiber volume content to 59±1% and the glue content, the glue overflowing from the front and rear heads and column sections was manually scraped off during winding.

[0064] Before winding, the fiber tension should be adjusted first, and the fiber tension should be measured with a tensioner, and the tension control mechanism should be adjusted to achieve the tension accuracy specified in the document; the winding line should be set according to the design requirements, and the dipping device should be adjusted at any time to control the amount of glue on the fiber. During winding, the excess glue on the product surface should be scraped off at any time, and the yarn arrangement should be observed. If there is yarn slippage, overlap or gap, the machine should be stopped in time; new glue should be continuously added during the winding process, and the yarn hair on the rubber roller and the glue dripping on the winding equipment should be removed to keep the entire production line clean and hygienic, so as to achieve civilized production. When the winding is about to end, the outer diameter should be measured. If the requirements are met, the machine can be stopped, the product can be unloaded, and transferred to the curing furnace.

[0065] In order to simultaneously ensure the fiber volume content and fiber utilization coefficient and minimize the degree of fiber wear, the fiber winding tension is controlled layer by layer, and the longitudinal winding layer and the circumferential winding layer are alternated. The gradient tension can make the layers of fibers wrapped from the inside to the outside of the shell have the same prestress, so that the overall effect of the composite material can be exerted when the shell is working. From the experience of practical scaled-down shell blasting, it is found that the fiber utilization coefficient of the entire shell wrapped with the same tension is generally around 70%, while the fiber utilization coefficient of the system-designed gradient tension shell blasting strength can reach more than 85%. The tension gradient table of this type of shell is shown in the table below;

[0066]

[0067] The tension of the fiber layer decreases gradually from layer to layer, resulting in a loose inside and tight outside situation. This is because the tension of the later wrapped layer of fiber will cause the earlier wrapped fiber layer together with the inner layer to shrink and deform, making the inner fiber loose. If the appropriate tension is not tested in advance, the fibers on the shell will be loose inside and tight outside, and the initial stress of the inner and outer fibers will be very different. When the container is pressurized, the fibers cannot be evenly stressed. In severe cases, the inner fiber may develop wrinkles, lining bubbles, deformation and other yielding conditions, which will greatly reduce the shell strength and fatigue performance.

[0068] Therefore, by testing the tension before winding, it is ensured that the wound fibers meet the requirements and avoid the situation where the inside is loose and the outside is tight. Specifically, by testing whether the tension of the fibers meets the requirements, the tension can be adjusted as needed. However, the premise is to test the tension. If there is no tension detection link, subsequent adjustment will be even more impossible. In this way, all winding layers have the same deformation and initial tension from the inside to the outside; when the shell container is pressurized, the fibers can also be subjected to stress, so that the strength of the container is improved and the fiber strength can be better developed.

[0069] Step 9) Winding reinforcement: Through the summary and analysis of practical experience, from a qualitative perspective, some issues can still be clearly judged, for example;

[0070] (1) In order to make the thickness of the head uniform and symmetrical, "every longitudinal layer must be reinforced", that is, a reinforcement layer must be laid between adjacent longitudinal layers;

[0071] (2) Use carbon cloth or glass cloth as the reinforcement layer instead of non-weft cloth; this can strengthen both the warp and weft directions near the end hole of the head, and can prevent the occurrence of failure mode 2 and failure mode 3 at the same time;

[0072] (3) The reinforcement is local, that is, it is limited to the vicinity of the polar hole where the joint is connected to the head. Considering the convenience of process implementation, it is difficult to fully reinforce the entire head, and the reinforcement near the equator will also bring inconvenience to the construction of the upper skirt. The strength problem of the entire head is mainly solved by adjusting the thickness of the head, that is, adjusting the stress balance coefficient ks.

[0073] (4) Glass fiber has higher fracture strain and fracture toughness. Although its strength is lower than that of carbon fiber, if the positive hybrid effect can be achieved and the carbon fiber shell head is reinforced with glass cloth, it may be possible to make up for the brittle fracture of carbon fiber.

[0074] According to the areas with large strain pointed out in the cylinder strength analysis report, the differences in the stiffness of the joint structure, and combined with the accuracy of the actual executable operation positions, the front and rear head reinforcement areas are determined. Starting from the two sides of the front and rear head column sections, along the equator towards the polar holes on both sides, domestic T700 grade plain cloth is used for reinforcement.

[0075] According to the calculation results, the joint opening needs to be reinforced to a thickness of Hmm, calculated as H / 0.2 layers. During reinforcement, the equipment should be kept rotating at a speed of 2%-3%. Starting from the two sides of the front and rear head column segments, reinforcement should be applied along the equator toward the polar holes on both sides using domestically produced T700-grade, 12k plain weave fabric, with a total of H / 0.2 layers. Reinforcement should be carried out from 20mm at the polar hole to 40mm (longitudinally before the first layer), 30mm (longitudinally before the first layer), 20mm (longitudinally after the first layer), 10mm (longitudinally after the first layer), and 0mm (longitudinally after the second layer) along the equator. If there are wrinkles, do not cut in the area near the column segment, but make a small cut on the other side without cutting. The overlap width is 10-20mm. The weight of the reinforcing fabric should be weighed for each reinforcement and recorded on the winding record card.

[0076] Before winding, the fiber tension should be adjusted first, and the fiber tension should be measured with a tensioner, and the tension control mechanism should be adjusted to achieve the tension accuracy specified in the document; the winding line should be set according to the design requirements, and the yarn arrangement should be observed. If there is yarn slippage, overlap or gap, the machine should be stopped in time; keep the entire production line clean and hygienic, and achieve civilized production. When the winding is about to end, measure the outer diameter. If it meets the requirements, the machine can be stopped, the product can be unloaded, and transferred to the curing oven; after the inner winding of the skirt is completed, the skirt is installed on the winding cylinder using the upper skirt tooling.

[0077] Step 10) Curing: The shell is wrapped with T700 carbon fiber and epoxy resin. Since it is an epoxy resin system, normal pressure heating is used during the curing process, and the shell wrapping layer and the insulating rubber layer are cured together. The specific parameters are: room temperature ~ 80℃, insulation for 2h; heating rate 25℃ ~ 30℃ / h; 80℃ ~ 150℃, insulation for 2h; heating rate 25℃ ~ 30℃ / h; 150 ~ 60±5℃, turn off the heat source, turn on the blast, and exit the oven at 60℃. During the curing process, equipment maintenance personnel are deployed to ensure the normal operation of the equipment during the curing process.

[0078] Step 11) Demolding: Remove the product from the mold. Since a metal mold is used, the mold can be reused.

[0079] Step 12) Detection

[0080] a) Dimension inspection: Use measuring tools that meet the dimensional accuracy requirements to inspect the shell dimensions, and use a three-coordinate measuring machine to inspect the form and position tolerances of the shell;

[0081] b) Nondestructive testing; Ultrasonic testing and ultrasonic flaw detection. When ultrasonic testing composite products, it is used to detect defects such as pores, cracks, delamination and foreign matter inclusions, as well as to determine the glue content of the product; ultrasonic testing can also be used to detect debonding between composite shells and thermal insulation layers, and can basically accurately determine delamination and debonding at the first interface of the engine shell; Radiographic testing, including X-ray, fluoroscope, neutron and radiographic testing, are commonly used to detect defects such as cracks, porosity, delamination and foreign matter inclusions. X-ray methods are very effective in detecting pores, cracks, delamination and foreign matter inclusions in various thermal insulation components of the shell, and can directly observe internal defects of the product from images or photographs. Due to the small size and structural thickness of this shell, A-scan testing is mainly used for testing;

[0082] c) Airtightness test: The test shall be carried out in accordance with QJ1658A. The inner cavity pressure shall be 0.3 MPa. If the pressure is maintained for 1 hour without dropping, the airtightness requirements shall be met.

[0083] d) Water pressure test; the specific operation of the water pressure blasting test shall be carried out in accordance with the provisions of Q / Nt015;

[0084] Step 13) Product delivery.

[0085] Example 2

[0086] A method for manufacturing a fully open composite material shell comprises the following steps:

[0087] Step 1) joint preparation;

[0088] Mold cleaning: Use a blade or other tool to clean the mold surface and other residues to avoid scratching the mold surface. Then use a clean cloth soaked in a small amount of acetone to wipe the mold to clean the remaining small amount of glue and other residues that may affect the product, and dry it.

[0089] a. First install the lower mold template, mold inner ring, and mold outer ring. After the layup is completed, install the upper mold template. Use carbon fiber unidirectional prepreg and carbon fiber plain prepreg.

[0090] b. Cut the materials according to the shape and quantity designed in the expanded drawing and number them;

[0091] c. Lay out the layers on the mold according to the designed laying process, with flat laying accounting for 60% and full package laying accounting for 40%;

[0092] d. Figure 4As shown, the joint is divided into four areas. First, the whole package area II and I are laid. Area I is first expanded outward, and then area III is laid, and then area IV is laid. Finally, area I is turned over to the layer area III. Area III is the side package layer, and areas II and I are the whole package layer. The whole package layer is laid first, and then the side package layer, and the two are laid alternately. After laying the first layer of the whole package, vacuum is applied for 5 minutes to compact the corners.

[0093] After laying area III, lay area IV. When laying area IV, after reaching 4 / 5 of the height, turn area I over and lay it crosswise with layer IV, with the upper and lower layers staggered. After the turning is completed, lay two layers of plain fabric on the outside.

[0094] During the paving process, use a driving board to remove bubbles and compact the tiles. Vacuum exhaust and compact the tiles every 8 layers, and the time is 4 hours. If necessary, carbon filaments can be added to ensure that the tiles are flat and not suspended.

[0095] To turn the side bag, you need to put it on the one-way layer layer by layer, and put a layer of plain cloth after each layer is turned over;

[0096] After applying the release agent on the upper cover, close the mold to ensure that the mold is in place;

[0097] Joint curing: ① Place the tooling in the press, fit the heating plate on the press to the mold, set the heating temperature to 70℃, and record the curing start time; ② When the thermocouple temperature reaches 70±5℃, start pressurizing with a pressure of 2.5MPa, and keep it warm for 2h and maintain the pressure at 2.5MPa; ③ After the end of the 70±5℃ insulation, set the heating temperature to 130℃, with a heating rate of 30℃ / h, keep it warm at 130±5℃ for 0.5h, then pressurize to 12MPa, keep it warm for 1h and maintain the pressure at 12MPa; ④ After the end of the 130±5℃ insulation, set the heating temperature to 160℃, with a heating rate of ⑤ After the 160±5℃ insulation is completed, set the heating temperature to 180℃, the heating rate to 30℃ / h, and when the thermocouple temperature reaches 180±5℃, keep warm for 1.5h; ⑥ Turn off the heating device and cool naturally to room temperature; the press pressure can be released after the thermocouple temperature is lower than 60℃; during the curing process, the pressure and temperature are recorded every 30min, and any abnormal phenomena are photographed and recorded; after the curing is completed, the joints are machined according to the product drawings and processed into necked end joints and open end joints.

[0098] Step 2) Manufacture of core mold: Manufacture the core mold according to the design drawing and spray polytetrafluoroethylene coating (anti-stick) on the surface.

[0099] Step 3) Insulation paving: 1.2mm EPDM rubber is laid on the surface of the core mold and adhesive is applied to the overlapping parts.

[0100] Step 4) Insulation pre-curing: After the insulation layer is laid, use an isolation film and a medium-temperature vacuum bag to evacuate the insulation layer, put it into the autoclave and pressurize it to 0.2MPa, and pre-cured it at 120℃ for 2h; Insulation polishing: After the insulation layer is pre-cured, polish the overlapping parts. The polishing should be smooth and the step height should not exceed 0.2mm. After polishing, clean it with ethyl acetate

[0101] Step 5) Install the joint: Install the front joint before winding, clean the inner and outer surfaces of the front and rear joints with ethyl acetate, apply a layer of interface glue after cleaning, dry at 50℃ for 2h, apply a layer of interface glue, continue to dry at 50℃ for 2h, then install the joint, lay a layer of insulating rubber on the joint surface, and vacuum compact it.

[0102] Step 6) Pre-wrap the rubber core mold surface with carbon fiber yarn according to the normal winding procedure. After winding the fiber yarn once, check the linear state. The adjusted fiber yarn should not overlap or separate, but should be evenly distributed on the core mold surface. The fiber yarn should be stable and non-slip on the core mold surface.

[0103] Remove the fiber yarn on the surface of the insulation core mold, and use ethyl acetate to clean the insulation surface. The surface must be clean and free of dust, fibers and other excess materials, and take photos for record; dry the carbon fiber yarn before winding, and put the fiber yarn into the oven at 60℃~70℃ for 6 hours; weigh the glue, stir for ten minutes, and ensure that the mixing is even; introduce the winding resin into the glue tank, and pass the fiber yarn evenly through the yarn comb to ensure that the fiber yarn is fully immersed in the glue tank; the fiber yarn passes through the middle row of yarn combs with a yarn tooth spacing between two yarns; before each layer of winding, test the tension of the front row of fiber yarns, and use an electronic tension meter to measure it. It is required to maintain the tension gradient according to the winding table; tension gradient Control is carried out, and the error range is within ±2N; before winding, brush a layer of winding resin on the surface, call the longitudinal and circumferential winding procedures, and wind according to the winding table. Reinforce the joints. After each layer of winding, scrape glue on the surface. It is required that there is no obvious glue residue on the fiber surface. The winding environment is dust-free, the temperature range is: 14-34℃, the relative humidity is ≤60%, and the temperature and humidity are monitored every 1h. Before winding, use a multi-angle handheld dust collector to remove dust from the entire winding room; after winding, wrap the shell surface with peeling cloth, isolation film, and breathable felt, and then wrap one layer of longitudinal and one layer of circumferential with glass fiber for curing;

[0104]

[0105] Step 7) Curing:

[0106] Keep at -80℃ for 2h; heating rate 25℃~30℃ / h;

[0107] 80℃-150℃, keep warm for 2h; heating rate 25℃~30℃ / h;

[0108] 150-60±5℃, turn off the heat source, turn on the blast, and take it out of the oven at 60℃;

[0109] During the curing process, equipment maintenance personnel are deployed to ensure the normal operation of the equipment during the curing process.

[0110] Step 8) Demolding: Remove the glass fiber, breathable felt, isolation membrane, and peeling cloth on the surface of the shell, cut along the middle of the shell, screw the round nuts at both ends, and remove the two small shells from both sides.

[0111] Step 9) Machining: Machining the rear end thread of the product after internal winding and curing according to the shell drawing.

[0112] The winding products produced by the present invention using a metal mold have better quality and are conducive to weight reduction; the metal mold can be used repeatedly, reducing costs; winding and forming two fully open carbon fiber composite combustion chambers at a time can also reduce costs; the necked end joint uses a composite joint directly embedded in the composite material, and the technology is relatively mature; the joint step at the open end is inserted into the composite material, and axial layer reinforcement and circumferential winding reinforcement are performed to ensure the connection strength.

[0113] The joints, winding layers and anti-ablation layers are all made of composite materials and have passed all cold and hot tests and are ready for use. Xinyang Company has researched various composite internal and external threads, and the connection strength can reach 50MPa.

[0114] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for manufacturing a fully open composite shell, characterized in that: The following steps are involved: Step 1) preparing a composite material joint and processing it into a necked end joint and an open end joint; Step 2) making a core mold; Step 3) Laying the insulation layer: Laying the insulation layer on the surface of the core mold; Step 4) preforming the heat insulation layer by vacuuming and pressurizing the heat insulation layer; Step 5) Install the joints: install the necked end joint and the open end joint to the corresponding positions on the core mold; Step 6) Inner winding: Use carbon fibers soaked in medium-temperature epoxy resin for winding, using a winding method that alternates longitudinal winding and circumferential winding. Adjust the fiber tension before winding, and adjust the tension to gradually decrease from the inside to the outside. During the winding process, reinforce the pole hole where the joint and the head are connected, and lay a reinforcement layer between adjacent longitudinal layers. Step 7) Outer winding: Wind the inner winding layer again with carbon fiber soaked in medium-temperature epoxy resin, using a hoop winding method. Before winding, the fiber tension needs to be adjusted and controlled, and the adjustment and control should be carried out according to the requirement of gradually decreasing the tension from the inside to the outside; Step 8) Curing: Curing is performed by heating at normal pressure, and the shell wrapping layer and the insulation layer are cured together; Step 9) Demolding: remove the shell from the core mold; Step 10) Inspection, including dimensional inspection, non-destructive inspection, air tightness inspection and water pressure inspection.

2. The method for manufacturing a fully open composite material shell according to claim 1, characterized in that: The reinforcing layer is made of plain cloth made of glass fiber material.

3. The method for manufacturing a fully open composite material shell according to claim 1, characterized in that: The specific reinforcement is as follows: the equipment keeps rotating during reinforcement, with both sides of the head column section as the starting points, and the reinforcement layer is circumferentially laid along the equator towards the polar holes on both sides.

4. The method for manufacturing a fully open composite material shell according to claim 1, characterized in that: When wrinkles appear during the laying of the reinforcement layer, do not cut in the area close to the column section, but make small cuts in the area away from the column section.

5. The method for manufacturing a fully open composite material shell according to any one of claims 1 to 4, characterized in that: Step 5) When installing the joint, lay an elastic layer on the joint surface.

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