Single-suspension-frame superconducting aircraft fairing and preparation method thereof

Abstract

The invention discloses a single-suspension-frame superconducting aircraft fairing and a preparation method thereof in the technical field of superconducting aircrafts. The preparation method comprises the steps of mold preparation, gradient laying of an outer skin, preparation of a foam-honeycomb double-core structure, installation of an embedded part, regional compaction of an inner skin and the like. The function integration of high temperature resistance, flame retardance and high strength is realized through the design of the three-layer gradient outer skin; a foam supporting framework and honeycomb core composite structure is adopted to ensure light weight and stability. The gradient composite material design and the foam-honeycomb double-core structure are adopted, the weight is greatly reduced while the structural strength is guaranteed, the lightweight requirement of the superconductive aircraft is met, the ablation resistance and flame retardance in the high-temperature environment are remarkably improved through the silicon carbide fiber reinforced ablation-resistant layer and the flame-retardant transition layer of the outer skin, and the service life of the superconductive aircraft is prolonged. The problem that the mechanical property of steel is suddenly reduced at high temperature is avoided, meanwhile, flame spreading is blocked, and the safety of internal equipment is protected.

Description

Technical Field

[0001] This invention relates to the field of supersonic vehicle technology, and in particular to a fairing for a single-suspension supersonic vehicle and its preparation method. Background Technology

[0002] The fairing of the single-hover supernavigation vehicle serves as the primary shielding and protection structure for the vehicle's external equipment. Its core function is to provide a safe and stable operating environment for the precision navigation control system, power unit, and other sensitive electronic components within the cabin. It must not only effectively withstand the onslaught of complex external airflow, sandstorms, rain, snow, and other severe weather conditions, reducing wind resistance to improve the vehicle's energy efficiency and endurance, but also ensure that the internal equipment is protected from severe vibrations and impacts during high-speed movement, guaranteeing navigation accuracy and system reliability. It is one of the key external components ensuring the stable and efficient execution of missions by the single-hover supernavigation vehicle.

[0003] However, existing technologies have some problems: In the current market, steel structure fairings have been widely used due to their high strength and ease of processing in order to meet the functional requirements of structures under various load conditions and ensure sufficient rigidity. However, under the same volume design, the weight of steel structure fairings far exceeds that of composite material structures, which directly increases transportation costs and additional loads on the supporting structure, hindering the achievement of lightweight design goals. At the same time, although steel has certain heat resistance, its mechanical properties will drop sharply under high temperature environments, its fire resistance is poor, and it does not have good flame retardant properties, which cannot effectively suppress the spread of flames and the damage of high temperature to internal equipment, posing serious safety hazards. Therefore, we propose a single-suspension frame supernavigator fairing and its preparation method. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a fairing for a single-suspension supernavigator and its preparation method.

[0005] The objective of this invention is achieved as follows: a fairing for a single-suspension supersonic navigation vehicle and its preparation method, comprising the following steps:

[0006] S1, Mold preparation and assembly: Degrease the main body of the fairing mold, the flange frame mold and the cap frame mold, assemble the degreased molds and perform leak prevention treatment.

[0007] S2, outer skin preparation: layer by layer of gradient outer skin prepreg is laid on the mold, while intermittent vacuum pre-compaction is performed. After the layering is completed, the vacuum encapsulation structure is laid and cold-pressed for curing.

[0008] The outer skin is made of multiple layers of differentiated prepreg sheets stacked together;

[0009] S3, Preparation and laying of foam core: Prepare a foam block, lay it on the outer skin, preliminarily fix it with pressure-sensitive tape and vacuum-compact the foam block, fill and seal the joints of the foam block and the connection between the foam block and the outer skin to form a foam support framework;

[0010] S4, Preparation and laying of honeycomb core: Prepare a honeycomb core block based on the contour dimensions of the foam support framework, place the honeycomb core block within the intervals of the foam support framework, and fill and seal to prepare the overall structure of the fairing;

[0011] S5, Laying of embedded parts: Open honeycomb holes according to laser projection, install the embedded parts correspondingly, use foam to level the honeycomb holes, and fill and seal;

[0012] S6, Laying of inner skin: Lay inner skin prepreg in the foam support framework and honeycomb core area for thickening, and lay a vacuum encapsulation structure;

[0013] The domain progressive compaction strategy includes: First, lay the inner skin above the foam framework for thickening, and at the same time lay the inner skin above the embedded parts inside the honeycomb core for thickening, perform pressure treatment on the middle area and cold pressing treatment on the edge area;

[0014] S7, Overall curing: Place the encapsulated whole in an autoclave and cure it according to the slow-release step curing strategy;

[0015] S8, Demolding and post-treatment: Remove the auxiliary materials, demold the product, and detect the fire resistance and interface bonding strength of the product.

[0016] Optionally, in step S1, the anti-leakage treatment is specifically:

[0017] S11, Coat a layer of sealant on the surface of the mold, and then lay a layer of mold repair tape;

[0018] S12, Lay the release cloth and conduct a vacuum test to check the vacuum degree;

[0019] The mold repair tape is laid in a lap joint, and the lap width is 5 - 10 cm;

[0020] During inspection, if a single vacuum tube can tighten the vacuum bag, the inspection is qualified.

[0021] Optionally, in step S2, the gradient outer skin prepreg includes an ablation-resistant layer, a flame-retardant transition layer, and a high-strength lightweight layer;

[0022] The outer skin is laid in sequence from the outside to the inside by the ablation-resistant layer, the flame-retardant transition layer, and the high-strength lightweight layer.

[0023] Optionally, the ablation-resistant layer is the outermost prepreg of the outer skin, including silicon carbide fiber and phenolic resin;

[0024] The silicon carbide fibers are coated with a zirconium oxide nanolayer;

[0025] The phenolic resin is mixed with polyetheretherketone micro powder at high temperature.

[0026] The ablation-resistant layer is impregnated by a hot-melt method and then cured.

[0027] Optionally, the flame-retardant transition layer is the intermediate layer prepreg of the outer skin, including carbon fiber and polyetheretherketone resin;

[0028] The carbon fiber surface is coated with a silicon carbide layer;

[0029] The polyetheretherketone (PEEK) is melt-blended with the flame retardant and then degassed under vacuum at 380°C.

[0030] The flame-retardant transition layer is prepared using a hot-pressing film process.

[0031] Optionally, the high-strength lightweight layer is the innermost prepreg of the outer skin, including carbon fiber, epoxy resin, silicon carbide whiskers, and glass microspheres;

[0032] During the preparation of the high-strength and lightweight layer, silicon carbide whiskers are dispersed by ball milling with epoxy resin after acid and alkali activation, and then cured in sections after wet winding and impregnation.

[0033] Optionally, the specific process of step S2 is as follows:

[0034] S21, Preheat the mold to 60~80℃;

[0035] S22, lay the first layer of prepreg, then prepare a vacuum pre-extraction bag for pre-compaction, time is 15min;

[0036] S23, lay the subsequent prepregs in sequence, and perform a pre-compaction treatment after every 4 layers of prepregs are laid;

[0037] S24. After laying the last layer of prepreg, perform sequential precompaction.

[0038] S25, after the prepreg is laid, lay the peeling cloth, release film, breathable felt, and vacuum bag film in sequence;

[0039] S26, the entire assembly will be transferred to an autoclave for cold pressing;

[0040] S27, After cold pressing, remove the vacuum sealing structure and transfer to a clean room for further installation;

[0041] The cold pressing conditions are: 50℃, 3.5MPa, and heat preservation for 1 hour.

[0042] Optionally, the process of step S6 is as follows: divide the laying area of ​​the inner skin into a middle area and an edge area;

[0043] The ratio of the middle area to the edge area is 6:4;

[0044] The inner skin prepreg is laid sequentially. After laying the first layer of prepreg, a pre-compaction treatment is performed. Every four layers of prepreg are laid, a pre-compaction treatment is performed. After the entire layer is laid, a pre-compaction treatment is performed again.

[0045] When laying the prepreg in the middle area, a local heating treatment is performed after every two layers of prepreg are laid, followed by manual roller pressing.

[0046] The localized heating treatment specifically involves heating at 80℃ for 10 seconds.

[0047] When laying the prepreg in the edge area, after each layer of prepreg is laid, it is treated with low-temperature freeze spray at -30℃ and then manually rolled.

[0048] Optionally, the sustained-release stepwise curing specifically involves:

[0049] 1) Heat to 80±5℃, heating rate ≤2.0℃ / min, medium temperature is 85℃;

[0050] When the temperature rises to 40℃, pressurization begins, and when the pressure reaches 0.15MPa, pressure is maintained.

[0051] After the slowest thermocouple is heated to 80°C, keep it at that temperature for 1 hour.

[0052] 2) After the heat preservation is completed, the temperature is raised to 130±5℃, the heating rate is ≤2.0℃ / min, and the medium temperature is 135℃;

[0053] After the slowest thermocouple is heated to 130°C, it is kept at that temperature for 3 hours.

[0054] 3) After the heat preservation is completed, the temperature is lowered at a rate ≤2.0℃ / min;

[0055] When the thermocouple temperature drops to 60°C, release the pressure and open the can.

[0056] The product is shipped out of the autoclave after the opening time is ≥2 hours or the minimum thermocouple temperature reaches 40℃.

[0057] A fairing for a single-suspension supersonic vehicle is prepared based on the aforementioned method for preparing a fairing for a single-suspension supersonic vehicle. It comprises an outer skin, a foam core layer, and an inner skin arranged sequentially from the outside in. Both the outer and inner skins are composed of composite laminates formed by curing multiple layers of prepreg. The foam core layer is disposed between the outer and inner skins and is bonded to them via an adhesive film to form an integral structure. The foam core layer constitutes the framework of the fairing. Panel grooves are formed on the foam core layer, and a honeycomb core layer is laid within the panel grooves. Embedded parts are embedded in the honeycomb core layer, and compensation pads are provided on the outer side of the embedded parts. The embedded parts and the honeycomb core layer are filled and sealed.

[0058] Compared with the prior art, the beneficial effects of the present invention are as follows: By adopting a gradient composite material design and a foam-honeycomb dual-core structure, the present application significantly reduces the weight while ensuring structural strength, thus meeting the lightweight requirements of super-navigation vehicles. The silicon carbide fiber-reinforced ablation-resistant layer and flame-retardant transition layer of the outer skin significantly improve the ablation resistance and flame retardancy under high temperature conditions, avoiding the problem of the rapid drop in mechanical properties of steel at high temperatures, while blocking the spread of flames and protecting the safety of internal equipment.

[0059] Secondly, by adopting a segmented progressive compaction strategy, deformation caused by differences in thermal expansion coefficients is effectively suppressed; the slow-release stepped curing process ensures that the resin flows fully and cures uniformly, reducing porosity and residual stress; the vacuum sealing process of the foam-honeycomb composite core material prevents film failure and improves the overall structural stability, thus enabling the fairing to have high dimensional accuracy, excellent interfacial bonding strength and anti-delamination performance, meeting the reliability and durability requirements of supernavigators in extreme environments. Attached Figure Description

[0060] 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.

[0061] Figure 1 This is a schematic diagram of the fairing preparation method provided by the present invention.

[0062] Figure 2 This is a schematic diagram of the fairing preparation method provided by the present invention.

[0063] Figure 3 This is a schematic diagram of the framework of the outer skin preparation method provided by the present invention. Detailed Implementation

[0064] 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.

[0065] like Figures 1 to 3 The fairing of a single-suspension supersonic navigation vehicle and its manufacturing method are shown, including the following steps:

[0066] S1, Mold preparation and assembly: Degrease the main body of the fairing mold, the flange frame mold and the cap frame mold, assemble the degreased molds and perform leak prevention treatment.

[0067] S2, outer skin preparation: layer by layer of gradient outer skin prepreg is laid on the mold, while intermittent vacuum pre-compaction is performed. After the layering is completed, the vacuum encapsulation structure is laid and cold-pressed for curing.

[0068] The outer skin is made of multiple layers of differentiated prepreg sheets stacked together;

[0069] S3, Foam core preparation and laying: Prepare foam blocks, lay them on the outer skin, initially fix them with pressure-sensitive tape and vacuum compact the foam blocks, fill and seal the joints of the foam blocks and the connection between the foam blocks and the outer skin to form a foam support skeleton.

[0070] S4, Honeycomb sandwich preparation and placement: honeycomb core blocks are prepared based on the outline dimensions of the foam support skeleton, the honeycomb core blocks are placed in the intervals of the foam support skeleton, and filled and sealed to prepare the overall structure of the fairing.

[0071] S5, Laying embedded parts: Open honeycomb holes according to the laser projection, install the embedded parts accordingly, use foam pads to level the honeycomb holes, and fill and seal them;

[0072] S6, Inner skin laying: Inner skin prepreg is laid in the area between the foam support skeleton and the honeycomb core to thicken it, and a vacuum sealing structure is laid.

[0073] The segmented progressive compaction strategy includes: first, laying an inner skin on top of the foam skeleton to thicken it, and at the same time, laying an inner skin on top of the embedded parts inside the honeycomb core to thicken it, with pressure treatment in the middle area and cold pressing treatment in the edge area.

[0074] S7, Overall Curing: Place the packaged whole in an autoclave and cure it according to the slow-release step curing strategy;

[0075] S8, Demolding and Post-processing: Remove auxiliary materials, demold the product, and test the product's fire resistance and interfacial bonding strength.

[0076] Furthermore, this application addresses the issues of thermal deformation control, interfacial bonding strength, and fire resistance of the fairing through synergistic innovation in gradient material design, differentiated compaction strategies, and stepped curing processes.

[0077] First, the outer skin adopts a three-layer gradient design to meet the functional requirements of high temperature resistance, flame retardancy, and high strength of the fairing; at the same time, a domain-based progressive compaction strategy is adopted to suppress thermal stress in the edge area before curing, which solves the risk of interface delamination caused by the difference in thermal expansion coefficient of the gradient materials, and achieves precise matching between material performance and process control.

[0078] Secondly, by using foam blocks to form a support skeleton conforming to the outer skin through vacuum compaction, the problem of shape instability caused by direct laying of the honeycomb core is solved; and through the sealing process, zero-gap sealing is achieved at the foam joints and skin connections to prevent the problem of easy failure of the adhesive film seal and ensure the integration stability of the honeycomb core and the foam skeleton.

[0079] Furthermore, considering the multiphase curing characteristics of gradient materials and dual-core structures, a slow-release step-curing strategy using an autoclave is employed:

[0080] Maintain stable resin viscosity during the low-temperature stage to prevent foam core collapse;

[0081] The outer boron phenolic resin layer is cured in a gradient at medium temperature, while the middle flame-retardant epoxy layer is activated simultaneously.

[0082] The high-temperature stage achieves complete cross-linking of the inner layer nano-epoxy, and the interfacial micro-gaps between the honeycomb core and the foam skeleton are eliminated by step-by-step pressurization.

[0083] Furthermore, the degreasing treatment of the mold is as follows: the fairing mold, the flange frame mold, and the cap frame mold are transferred to a hot autoclave and heated at 180°C for 5 hours to remove the anti-rust oil from the mold surface. Then, the surface of the fairing mold is wiped with a wiping cloth dipped in anhydrous ethanol to clean the surface debris and stains. The standard for cleaning is that the wiping paper after wiping the mold surface is free of any stains. Finally, the degreased flange frame mold, cap frame mold, and fairing mold body are connected by pins and bolts.

[0084] Specifically, in step S1, the leak prevention treatment is as follows:

[0085] S11, apply a layer of sealant to the mold surface, and then apply a layer of mold repair tape;

[0086] S12, Lay out the release cloth and perform a vacuum test to check the vacuum level;

[0087] The mold repair tape is laid with an overlap, with an overlap width of 5-10cm.

[0088] During inspection, if a vacuum tube can tighten the vacuum bag, the inspection is considered qualified.

[0089] Furthermore, by successively applying sealant, overlapping and laying a mold repair tape and a release cloth on the mold surface, a three - level sealing barrier is formed: the sealant fills the microscopic gaps, the overlapping tape blocks the macroscopic leakage paths, and the release cloth evenly disperses the vacuum pressure. Adopting the single - vacuum - tube tightening test standard can ensure zero leakage risk during the curing process of the mold system, avoid the porosity of the composite material exceeding the standard due to gas residue, and at the same time, the overlapping design improves the peel strength at the tape joint, significantly reducing the probability of delamination defects during the demolding process.

[0090] Specifically, in step S2, the gradient outer skin prepreg includes an ablation - resistant layer, a flame - retardant transition layer, and a high - strength lightweight layer;

[0091] The outer skin is laid in sequence from the outside to the inside through the ablation - resistant layer, the flame - retardant transition layer, and the high - strength lightweight layer.

[0092] It should be noted that the prepreg, foam, adhesive film, foaming agent, etc. used for the fairing should comply with the corresponding material specifications and technical agreement requirements. After passing the in - factory re - inspection, they can be put into use;

[0093] Secondly, the prepreg and adhesive film need to be taken out of the cold storage one day in advance for constant temperature. When there is no water vapor on the surface of the sealed bag, the sealed bag can be opened; the prepreg is cut into sheets by an automatic cutting machine according to the cutting drawing. The prepreg needs to be placed on the reference line of the numerical control cutting machine tool, and it is necessary to check that there is no impurity on the cutting machine before cutting. Place them neatly according to the serial number on the sheet for later use.

[0094] Furthermore, the gradient outer skin realizes functional gradient collaborative protection by successively laying the ablation - resistant layer, the flame - retardant transition layer, and the high - strength lightweight layer from the outside to the inside: the outermost ablation - resistant layer directly resists the erosion of ultra - high - temperature airflow, the middle flame - retardant transition layer effectively blocks heat conduction and prevents flame spread, and the innermost high - strength lightweight layer provides core structural support. Thus, while maintaining the overall lightweight of the fairing, it has excellent ablation resistance, flame retardance, and mechanical properties, meeting the requirements of the extreme service environment of the super - navigation vehicle.

[0095] Specifically, the ablation - resistant layer is the outermost prepreg of the outer skin, including silicon carbide fibers and phenolic resin;

[0096] The silicon carbide fibers are coated with a zirconia nanolayer;

[0097] Micro - powder of polyether ether ketone is added to the phenolic resin and high - temperature blending is adopted;

[0098] After the ablation - resistant layer is impregnated by the hot - melt method, it is cured and formed.

[0099] Furthermore, the silicon carbide fibers with zirconia nano-coating form a dense oxide layer at high temperature, effectively blocking oxygen diffusion and inhibiting fiber oxidation loss; the addition of polyether ether ketone (PEEK) micro powder to phenolic resin forms an interpenetrating network structure through high-temperature blending, which not only retains the carbonization rate of phenolic resin, but also utilizes the high thermal stability of PEEK to delay resin pyrolysis. Hot-melt impregnation ensures tight bonding at the fiber / resin interface, forming a continuous ablation-resistant barrier after curing.

[0100] Specifically, the flame-retardant transition layer is the intermediate layer prepreg of the outer skin, including carbon fiber and polyetheretherketone resin.

[0101] Carbon fiber surface coated with silicon carbide layer;

[0102] Polyetheretherketone (PEEK) is melt-blended with a flame retardant and then degassed under vacuum at 380°C.

[0103] The flame-retardant transition layer is prepared using a hot-pressing film process.

[0104] Furthermore, silicon carbide-coated carbon fibers form an antioxidant protective layer at high temperatures, increasing the strength retention rate of the fibers to 85% at 600°C; the melt blending of polyetheretherketone (PEEK) and flame retardant increases the limiting oxygen index of the resin while maintaining its inherent toughness.

[0105] Vacuum degassing at 380℃ eliminates micropore defects, while the hot-pressing process ensures a strong bond at the fiber / resin interface, giving the transition layer both flame-retardant interruption effect and load transfer function, connecting the outer layer's ablation resistance and the inner layer's load-bearing requirements.

[0106] Specifically, the high-strength lightweight layer is the innermost prepreg of the outer skin, including carbon fiber, epoxy resin, silicon carbide whiskers, and glass microspheres;

[0107] In the preparation of the high-strength and lightweight layer, silicon carbide whiskers are dispersed by ball milling with epoxy resin after acid and alkali activation, and then cured in sections after wet winding and impregnation.

[0108] Furthermore, carbon fiber, as the main load-bearing skeleton, provides ultra-high specific strength, and acid-base activated silicon carbide whiskers are dispersed in epoxy resin through ball milling to form a three-dimensional nano-reinforcing network, which improves the matrix modulus and inhibits crack propagation.

[0109] The introduction of glass microspheres achieves a weight reduction of 10% to 15% while ensuring compressive strength; wet winding impregnation combined with segmented curing process ensures the interfacial bonding strength of fiber / resin / whisker, while eliminating internal stress, reducing the density of high-strength and lightweight layers, and still having excellent specific stiffness.

[0110] Specifically, the process for step 2 is as follows:

[0111] S21, Preheat the mold to 60~80℃;

[0112] S22, lay the first layer of prepreg, then prepare a vacuum pre-extraction bag for pre-compaction, time is 15min;

[0113] S23, lay the subsequent prepregs in sequence, and perform a pre-compaction treatment after every 4 layers of prepregs are laid;

[0114] S24. After laying the last layer of prepreg, perform sequential precompaction.

[0115] S25, after the prepreg is laid, lay the peeling cloth, release film, breathable felt, and vacuum bag film in sequence;

[0116] S26, the entire assembly will be transferred to an autoclave for cold pressing;

[0117] S27, After cold pressing, remove the vacuum sealing structure and transfer to a clean room for further installation;

[0118] The cold pressing conditions are: 50℃, 3.5MPa, and heat preservation for 1 hour.

[0119] Furthermore, preheating the mold at 60~80℃ reduces resin viscosity to promote impregnation; intermittent pre-compaction of every 4 layers of prepreg removes interlayer air bubbles in a stepwise manner; multi-layer vacuum bag sealing ensures uniform pressure transmission; cold pressing at 50℃ completes fiber network reconstruction before the resin gels, while avoiding the pre-curing risk caused by high temperature, resulting in a preform density of over 98%, providing a defect-free preform foundation for subsequent autoclave curing, thereby improving the interlayer shear strength of the final product.

[0120] Specifically, before preparing the foam block, the foam needs to be dehumidified. First, use clean wiping paper dipped in anhydrous ethanol to clean the surface of the foam. After drying for 15 minutes, wrap the foam core with a peelable cloth, a breathable felt, and a sealed bag in sequence. Transfer it to the oven, open the sealed bag and the breathable felt, and expose the foam to the air. Dry it at 130°C for 2 hours to dehumidify.

[0121] Then, wrap a layer of medium-temperature epoxy film (LWF-2B black petrochemical) on the surface of the foam. After the film is wrapped, place it in a vacuum bag and vacuum for 15 minutes to solidify the film on the surface of the foam.

[0122] It is important to note that the adhesive film must overlap to ensure that the entire surface of the foam is covered with adhesive film, and the dried foam should be used within 24 hours or sealed in a moisture-proof packaging bag.

[0123] In addition, the foam surface needs to be covered with 0.5mm reinforcing material sheets, i.e., 4 layers of SYT49S-12K / YZR-02S prepreg, with a layup angle of [45 / 0 / 0 / -45]. Above and below the horizontal ribs, 2mm reinforcing material sheets, i.e., 16 layers of prepreg, need to be laid with layup angles of [45 / -45 / 0 / 90 / 90 / 0 / -45 / 45].

[0124] After laying the first layer of prepreg, vacuum pre-packing bags are made and pre-compacted for 15 minutes. After the first layer is laid and pre-compacted, pre-packing is required for every 4 layers laid. Pre-packing is also required for 15 minutes when laying the last layer of prepreg, in order to strengthen the strength of the foam support skeleton.

[0125] Specifically, before the honeycomb sandwich core is prepared and laid, a layer of medium-temperature epoxy film (LWF-2B black petrochemical) needs to be laid in the area of ​​the foam support skeleton inside the fairing. The blue film of the film is not removed first. A vacuum bag is made and the film is drawn firmly onto the outer skin. Then, the honeycomb material is dehumidified.

[0126] Clean the honeycomb surface with clean wiping paper dipped in anhydrous ethanol. After drying for 15 minutes, wrap the honeycomb in sequence with a peelable cloth, a breathable felt, and a sealed bag. Transfer it to an oven, open the sealed bag and the breathable felt, and expose the honeycomb to the air. Dry it at 70°C for 2 hours to remove moisture.

[0127] It should be noted that the dried honeycomb should be used within 24 hours, or sealed in a moisture-proof packaging bag;

[0128] Then, honeycomb core blocks are prepared based on the outline dimensions of the foam support skeleton. The honeycomb is cut into appropriate sizes according to the filling size between the foams. Stretched honeycomb is used in areas with large curvature. During cutting, a vacuum cleaner is used to remove the debris cut off from the honeycomb.

[0129] Finally, remove the blue film of the medium-temperature epoxy film (LWF-2B black petrification) on the surface of the outer skin, and place the honeycomb pieces one by one in the corresponding area. Use medium-temperature expanding foam film (J-275D) to connect the seams between honeycombs and the connection between honeycombs and foam. Cut the expanding foam into strips with the same width as the height of the honeycomb. If the gap is still obvious after filling one strip of expanding foam, several strips of expanding foam need to be filled. That is, the gap filling with expanding foam must be completely filled.

[0130] Specifically, before laying the embedded parts, the embedded parts are pre-treated: First, use clean wiping paper dipped in anhydrous ethanol to clean the surface of the embedded parts, and after drying for 15 minutes, wrap a layer of medium-temperature epoxy film (LWF-2B black petrochemical) on the surface of the embedded parts. The film is overlapped to ensure that the film is present on the surface of the embedded parts. After the film is wrapped, place it in a vacuum bag and vacuum for 15 minutes to solidify the film on the surface of the embedded parts. Then, open the honeycomb holes according to the laser projection and install the embedded parts accordingly.

[0131] It should be noted that, to reduce weight, the thickness of the embedded parts is only 4mm and 6mm, while the honeycomb core thickness is 10mm. Therefore, a layer of foam needs to be placed under the embedded parts to raise them to be level with the honeycomb core. The connection between the embedded parts and the honeycomb core needs to be filled with expanding foam to ensure that the embedded parts are completely fixed.

[0132] In addition, the embedded parts at the connection point need to be reinforced with 1mm reinforcing material, i.e., 8 layers of prepreg, due to the stress requirements. Then, a layer of medium-temperature epoxy film (LWF-2B black petrochemical) is laid on the honeycomb inside the fairing. The blue film of the film is not removed first. A vacuum bag is made and the film is drawn firmly onto the honeycomb surface.

[0133] Specifically, step S6 involves dividing the inner skin laying area into a middle area and an edge area.

[0134] The ratio of the middle area to the edge area is 6:4;

[0135] The inner skin prepreg is laid sequentially. After laying the first layer of prepreg, a pre-compaction treatment is performed. Every four layers of prepreg are laid, a pre-compaction treatment is performed. After the entire layer is laid, a pre-compaction treatment is performed again.

[0136] When laying the prepreg in the middle area, a local heating treatment is performed after every two layers of prepreg are laid, followed by manual roller pressing.

[0137] The localized heating treatment specifically involves heating at 80℃ for 10 seconds.

[0138] When laying the prepreg in the edge area, after each layer of prepreg is laid, it is treated with low-temperature freeze spray at -30℃ and then manually rolled.

[0139] Furthermore, the molding quality and interfacial bonding performance of the inner skin are improved through zoned differentiated treatment. For the middle area, local heating combined with manual rolling is used to promote fiber impregnation and eliminate interlayer bubbles in the resin softened state, while avoiding premature resin curing caused by overall heating.

[0140] For the edge areas, low-temperature cryo-spraying can quickly stabilize the shape of the prepreg, prevent fiber slippage and interlayer misalignment, and the rolling operation further ensures the density of the edge areas, thereby solving the deformation problem of large-sized components caused by thermal expansion differences and edge effects.

[0141] Furthermore, the synergistic application of stepped pre-compaction and local strengthening processes achieves a balance between overall uniformity and specific local requirements. Periodic heating and rolling in the middle zone enhances the interlayer shear strength of the core, while freeze curing in the edge zone improves the accuracy of boundary dimensions. Overall pre-compaction ensures the density of the macrostructure, while precise control of zones optimizes the micro-interface performance, enabling the inner skin to possess both overall rigidity and local toughness under complex stress environments, significantly reducing the risk of residual stress during subsequent curing.

[0142] Specifically, the slow-release stepwise solidification process is as follows:

[0143] 1) Heat to 80±5℃, heating rate ≤2.0℃ / min, medium temperature is 85℃;

[0144] When the temperature rises to 40℃, pressurization begins, and when the pressure reaches 0.15MPa, pressure is maintained.

[0145] After the slowest thermocouple is heated to 80°C, keep it at that temperature for 1 hour.

[0146] 2) After the heat preservation is completed, the temperature is raised to 130±5℃, the heating rate is ≤2.0℃ / min, and the medium temperature is 135℃;

[0147] After the slowest thermocouple is heated to 130°C, it is kept at that temperature for 3 hours.

[0148] 3) After the heat preservation is completed, the temperature is lowered at a rate ≤2.0℃ / min;

[0149] When the thermocouple temperature drops to 60°C, release the pressure and open the can.

[0150] The product is shipped out of the autoclave after the opening time is ≥2 hours or the minimum thermocouple temperature reaches 40℃.

[0151] Furthermore, the slow-release stepwise curing process improves the curing quality and performance stability of composite materials through precise temperature and pressure control and gradual phase change regulation.

[0152] The first stage employs a low-temperature, slow-heating, and stepped-pressurization strategy, applying initial pressure within the critical temperature range (40℃~80℃) where the resin viscosity is lowest. This ensures the resin flows fully and evenly impregnates the fibers, while avoiding premature high pressure that could disrupt fiber arrangement. The holding pressure stage ensures that air bubbles are fully expelled, forming a dense preform structure and reducing porosity defects.

[0153] The second stage (130℃ heat preservation) involves strictly controlling the heating rate to ensure that the resin system smoothly enters the cross-linking reaction stage, avoiding the accumulation of internal thermal stress caused by violent heat release. Long-term high-temperature heat preservation ensures that the resin is completely cured and forms a high cross-linking density network, thereby improving the mechanical properties and heat resistance of the matrix.

[0154] The third stage (slow cooling and pressure relief) adopts symmetrical slow cooling to minimize the temperature gradient inside and outside the component, effectively suppressing warping deformation caused by uneven shrinkage. The delayed pressure relief and temperature balancing strategy further releases residual stress and ensures the dimensional stability of the product.

[0155] A fairing for a single-suspension supersonic vehicle is prepared based on the aforementioned method for preparing a fairing for a single-suspension supersonic vehicle. It comprises an outer skin, a foam core layer, and an inner skin arranged sequentially from the outside in. Both the outer and inner skins are composed of composite laminates formed by curing multiple layers of prepreg. The foam core layer is disposed between the outer and inner skins and is bonded to them via an adhesive film to form an integral structure. The foam core layer constitutes the framework of the fairing. Panel grooves are formed on the foam core layer, and a honeycomb core layer is laid within the panel grooves. Embedded parts are embedded in the honeycomb core layer, and compensation pads are provided on the outer side of the embedded parts. The embedded parts and the honeycomb core layer are filled and sealed.

[0156] In summary, this application, by employing a gradient composite material design and a foam-honeycomb dual-core structure, significantly reduces weight while ensuring structural strength, meeting the lightweight requirements of supernavigation vehicles. The silicon carbide fiber-reinforced ablation-resistant layer and flame-retardant transition layer of the outer skin significantly improve ablation resistance and flame retardancy under high-temperature environments, avoiding the problem of a sharp drop in the mechanical properties of steel at high temperatures, while also blocking the spread of flames and protecting the safety of internal equipment.

[0157] Secondly, by adopting a segmented progressive compaction strategy, deformation caused by differences in thermal expansion coefficients is effectively suppressed; the slow-release stepped curing process ensures that the resin flows fully and cures uniformly, reducing porosity and residual stress; the vacuum sealing process of the foam-honeycomb composite core material prevents film failure and improves the overall structural stability, thus enabling the fairing to have high dimensional accuracy, excellent interfacial bonding strength and anti-delamination performance, meeting the reliability and durability requirements of supernavigators in extreme environments.

[0158] 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 preparing a fairing for a single-suspension supersonic vehicle, characterized in that: It includes the following steps: S1, Mold preparation and assembly: Degrease the fairing mold body, flanging frame mold and hatch frame mold, assemble the degreased molds into a shape, and perform leak prevention treatment; S2, Outer skin preparation: Lay gradient outer skin prepreg layer by layer on the mold, and at the same time perform intermittent vacuum pre-compaction treatment. After completing the layup, lay a vacuum encapsulation structure and perform cold pressing and curing; The outer skin is made by stacking multiple layers of differentiated prepreg sheets, S3, Foam core preparation and laying: Prepare a foam block, lay it on the outer skin, preliminarily fix and vacuum compact the foam block with pressure-sensitive tape, and fill and seal the joints of the foam block and the connection between the foam block and the outer skin to form a foam support skeleton; S4, Honeycomb core preparation and laying: Prepare a honeycomb core block based on the contour size of the foam support skeleton, place the honeycomb core block in the interval of the foam support skeleton, and fill and seal to prepare the overall structure of the fairing; S5, Laying预埋件: Open honeycomb holes according to laser projection, install预埋件 correspondingly, use foam to level the honeycomb holes, and fill and seal; S6, Inner skin paving: In the area of the foam support skeleton and the honeycomb core, lay the inner skin prepreg using a domain-by-domain progressive compaction strategy, and lay a vacuum encapsulation structure; The domain-by-domain progressive compaction strategy includes: First, lay the inner skin above the foam skeleton to thicken it, and at the same time lay the inner skin above the预埋件 inside the honeycomb core to thicken it, perform pressure treatment in the middle area and cold pressing treatment in the edge area; S7, Overall curing: Place the encapsulated whole in a autoclave and cure it according to the slow-release stepped curing strategy; S8, Demolding and post-treatment: Remove non-product materials, demold the product, and detect the fire resistance and interface bonding strength of the product.

2. The method for preparing a fairing for a single-suspension supersonic vehicle according to claim 1, characterized in that: In step S1, the leak prevention treatment specifically is: S11, Coat a layer of sealant on the mold surface, and then lay a layer of mold repair tape; S12, Lay a release cloth and perform a vacuum test to check the vacuum degree; The mold repair tape is laid by overlapping, and the overlapping width is 5-10 cm; During the inspection, if a vacuum tube can tighten the vacuum bag, the inspection is qualified.

3. The method for preparing a fairing for a single-suspension supersonic vehicle according to claim 1, characterized in that: In step S2, the gradient outer skin prepreg includes an ablation-resistant layer, a flame-retardant transition layer, and a high-strength lightweight layer; The outer skin is laid in the order of the ablation-resistant layer, the flame-retardant transition layer, and the high-strength lightweight layer from the outside to the inside.

4. The method for preparing a fairing for a single-suspension supersonic vehicle according to claim 3, characterized in that: The ablation-resistant layer is the outermost prepreg of the outer skin, including silicon carbide fiber and phenolic resin; The silicon carbide fiber is coated with a zirconia nanolayer; Polyether ether ketone micropowder is added to the phenolic resin and high-temperature co-blending is used; After the ablation-resistant layer is impregnated by the hot-melt method, it is cured and formed.

5. The method for preparing a fairing for a single-suspension supersonic vehicle according to claim 3, characterized in that: The flame-retardant transition layer is the middle prepreg of the outer skin, including carbon fiber and polyether ether ketone resin; The carbon fiber surface is coated with a silicon carbide layer; The polyether ether ketone and the flame retardant are melt-blended and vacuum degassed at 380 °C; The flame-retardant transition layer is prepared and formed by the hot-press film process.

6. The method for preparing a fairing for a single-suspension supersonic vehicle according to claim 3, characterized in that: The high-strength lightweight layer is the innermost prepreg of the outer skin, including carbon fiber, epoxy resin, silicon carbide whiskers, and glass microspheres; During the preparation of the high-strength and lightweight layer, silicon carbide whiskers are dispersed by ball milling with epoxy resin after acid and alkali activation, and then cured in sections after wet winding and impregnation.

7. The method for preparing a fairing for a single-suspension supersonic vehicle according to claim 1, characterized in that: The specific process of step S2 is as follows: S21, Preheat the mold to 60~80℃; S22, lay the first layer of prepreg, then prepare a vacuum pre-extraction bag for pre-compaction, time is 15min; S23, lay the subsequent prepregs in sequence, and perform a pre-compaction treatment after every 4 layers of prepregs are laid; S24. After laying the last layer of prepreg, perform sequential precompaction. S25, after the prepreg is laid, lay the peeling cloth, release film, breathable felt, and vacuum bag film in sequence; S26, the entire assembly will be transferred to an autoclave for cold pressing; S27, After cold pressing, remove the vacuum sealing structure and transfer to a clean room for further installation; The cold pressing conditions are: 50℃, 3.5MPa, and heat preservation for 1 hour.

8. The method for preparing a fairing for a single-suspension supersonic vehicle according to claim 1, characterized in that: The specific process of step S6 is as follows: divide the laying area of ​​the inner skin into the middle area and the edge area; The ratio of the middle area to the edge area is 6:4; The inner skin prepreg is laid sequentially. After laying the first layer of prepreg, a pre-compaction treatment is performed. Every four layers of prepreg are laid, a pre-compaction treatment is performed. After the entire layer is laid, a pre-compaction treatment is performed again. When laying the prepreg in the middle area, a local heating treatment is performed after every two layers of prepreg are laid, followed by manual roller pressing. The localized heating treatment specifically involves heating at 80℃ for 10 seconds. When laying the prepreg in the edge area, after each layer of prepreg is laid, it is treated with low-temperature freeze spray at -30℃ and then manually rolled.

9. The method for preparing a fairing for a single-suspension supersonic vehicle according to claim 1, characterized in that: The sustained-release stepwise curing specifically involves: 1) Heat to 80±5℃, heating rate ≤2.0℃ / min, medium temperature is 85℃; When the temperature rises to 40℃, pressurization begins, and when the pressure reaches 0.15MPa, pressure is maintained. After the slowest thermocouple is heated to 80°C, keep it at that temperature for 1 hour. 2) After the heat preservation is completed, the temperature is raised to 130±5℃, the heating rate is ≤2.0℃ / min, and the medium temperature is 135℃; After the slowest thermocouple is heated to 130°C, it is kept at that temperature for 3 hours. 3) After the heat preservation is completed, the temperature is lowered at a rate ≤2.0℃ / min; When the thermocouple temperature drops to 60°C, release the pressure and open the can. The product is shipped out of the autoclave after the opening time is ≥2 hours or the minimum thermocouple temperature reaches 40℃.

10. A fairing for a single-suspension supersonic vehicle, manufactured according to the method for manufacturing a fairing for a single-suspension supersonic vehicle as described in any one of claims 1-9, characterized in that: The fairing comprises, from the outside in, an outer skin, a foam core layer, and an inner skin. Both the outer and inner skins are composed of composite laminates formed by curing multiple layers of prepreg. The foam core layer is disposed between the outer and inner skins and is bonded to them with an adhesive film to form an integral structure. The foam core layer forms the frame of the fairing. Panel grooves are formed on the foam core layer, and a honeycomb core layer is laid in the panel grooves. Embedded parts are embedded in the honeycomb core layer, and compensation pads are provided on the outside of the embedded parts. The embedded parts and the honeycomb core layer are filled and sealed.

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