Flexible inflatable material and preparation method thereof

Abstract

The invention discloses a flexible inflatable material and a preparation method thereof, and belongs to the field of flexible inflatable materials. According to the method, by analyzing a model, forming a wire drawing hole in a removable supporting mold and combining a dotted single-knot type, through end point type and row-column sectional type specific wire drawing process, the arrangement of interval wires of the flexible inflatable material is comprehensively adjustable in position, length and pre-tightening force, and the structural adaptability and stability are improved; through in-situ glue brushing, film forming and sealing, the flexible inflatable material is uniform in sealing and stacking, not prone to leakage, not prone to wrinkling, not prone to secondary deformation and not prone to layering. The method can be used for preparing the high-pressure and high-shape-preserving special-shaped flexible inflatable material, and the shape preserving precision of the flexible inflatable material in a complex mechanical environment is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flexible inflatable materials, in particular to a high-pressure high-conformal profile flexible inflatable material assisted by a removable supporting mold and a preparation method thereof. BACKGROUND

[0002] Inflatable structures are widely used in emergency rescue equipment, inflatable boats, inflatable tents and other scenes due to their light weight, foldability and rapid deployment. Such traditional inflatable materials have relatively low shape accuracy requirements, and a single air bag can generally meet the bearing and sealing requirements. However, in high-conformal inflatable materials such as unmanned aerial vehicle flexible wings, inflatable antenna reflectors, and deployable aerospace skins, the working performance directly depends on the geometric accuracy and stability of the complex curved surface, and needs to maintain a shape error of ±1mm for a long time under high internal pressure (≥30kPa), which has high requirements for inflatable structures.

[0003] To improve the out-of-plane stiffness under pressure, the existing technology usually arranges spacer yarns between the upper and lower skins, so that the inflatable structure is upgraded from a pure film air bag to a "pressure-tension" mixed bearing system. Although the woven or warp-knitted spacer fabric can inhibit overall bulging, the spacer yarn length and spacing can only remain constant and equidistant due to the structure of the loom and the needle bed stroke, and can only be used for forming plate-shaped or simple curved inflatable parts, which cannot meet the needs of complex curvature change profile curved surfaces. Patent CN115335214A discloses limiting the inflation shape of the air bag by means of robot point-by-point hot pressing or pasting connecting bands on the film surface. This scheme can adjust the layout of the connecting bands to a certain extent, but it is highly dependent on visual positioning, six-axis robot synchronization and multiple hot pressing path planning. The width and step resolution of the adhesive tape limit the minimum radius of curvature, and stress concentration easily occurs at the linear adhesive interface of the long tape, leading to peeling or adhesive line migration under high pressure.

[0004] In addition, the existing technology also has the following pain points: high flexibility materials often lack tear resistance, while high-strength materials may lose flexibility, and it is difficult to balance flexibility and strength; there are structural mechanics defects, and deformation easily occurs due to local stress concentration under high load; due to the existing process, the production of flexible inflatable materials with complex profile structures is difficult, the precision level is low, the production cost is high, and the defective product rate is high; the current sealing process cannot meet the large deformation of profiled curved surfaces: the calendering composite needs to be flat and straight, and the high double curvature area is prone to wrinkling; the roll coating and film lamination need to be overlapped multiple times at sharp corners, and the uneven thickness of the lamination layer has a high leakage probability; the modulus difference between the film and the fabric causes secondary deformation after inflation, and there is a risk of insufficient interfacial adhesion strength, and the film layer and the fabric are prone to peeling, which cannot meet the requirements of high pressure and high conformality.

[0005] In view of this, it is necessary to develop a flexible inflatable material and a preparation method thereof, which takes into account flexibility and strength; can adapt to complex mechanical conditions and keep its performance parameters within a small tolerance; reduces mechanical defects of special-shaped complex structures; reduces the problems of uneven thickness of the existing sealing process, high leakage probability, easy delamination, difficulty in sealing the secondary deformation special-shaped part after inflation; and complex production process, high production cost and the like. SUMMARY

[0006] The present application provides a flexible inflatable material and a preparation method thereof, which solves the problem that flexibility and strength are difficult to be taken into account; solves the problem that folding of the flexible inflatable material affects its performance; cannot adapt to complex mechanical environment, and its performance parameters vary greatly; special-shaped complex structures have mechanical defects; poor sealing performance, easy to leak, easy to deform and easy to delaminate; complex production process, dependent on high-performance equipment, high production cost and the like.

[0007] The core technical scheme of the present application is that: through modeling analysis, according to the analysis results of normal stress field and shear stress field, interval wire distribution calculation is carried out, and wire drawing holes are set on the removable support mold, a specific wire drawing process is adopted to manufacture a preformed part, and the sealing performance is improved through in-situ glue brushing film sealing process.

[0008] The method includes but is not limited to the following steps: A flexible inflatable material preparation method, the method comprises: S1, a model is established and analyzed based on performance requirements, the analysis results include the normal stress field and shear stress field of the model; S2, interval wire distribution calculation; S3, removable support mold design and shaping, the removable support mold is provided with wire drawing holes; S4, preformed part manufacturing: using a wire drawing process to manufacture a preformed part; S5, in-situ glue brushing film sealing; S6, removable support mold removal.

[0009] Further, it further comprises the step of: based on the analysis results of S1, S21, the model is divided into regions and classified; S22, the wire drawing holes are designed for different regions respectively.

[0010] Further, it further comprises the step S211: If the normal stress of the model region is greater than σ1 MPa or the shear stress is greater than T1 MPa, the region is divided into a high stress zone; If the normal stress of the model region is between σ2-σ1 MPa or the shear stress is between T2-T1 MPa, the region is divided into a medium stress zone; If the model area normal stress <σ2 MPa and shear stress <T2 MPa, the area is divided into low stress area; Wherein σ2 <σ1, T2 <T1.

[0011] Further, it further comprises the step S221: The high stress area hole spacing is set to L1-L2 mm, and high density cross setting is adopted; The hole spacing of the medium stress area is set to L3-L4 mm, and the linear or ring setting of medium density is adopted; The hole spacing of the low stress area is set to ≥L5 mm or no hole position is set; Wherein L1 <L2 <L3 <L4 <L5.

[0012] Further, it further comprises the step: S41 lays the fabric reinforcement layer on the surface of the removable support mold, and makes the fabric reinforcement layer adhere to the surface of the removable support mold through vacuum adsorption; S42 adopts different wire drawing processes to draw the spacer wire through the wire drawing hole and the fabric reinforcement layer, so that the fabric reinforcement layer is fixed on the surface of the removable support mold.

[0013] Further, the wire drawing process comprises: Point single knot type: a single ring knot node is formed on each side of the preset wire drawing hole by the spacer wire, so as to realize accurate positioning and pre-tightening force adjustment; Row and column segmented type: according to the preset wire drawing path, the spacer wire is drawn through a plurality of preset wire drawing holes and then knotted, forming a segmented support structure, which is used for considering the strength and flexibility of large-span area; Through the end point type: one spacer wire penetrates all the preset wire drawing holes in turn, and is fixed by a knot or a double ring knot node at the end of the wire drawing, which is used for maintaining the overall tension of the whole spacer wire.

[0014] Further, it further comprises the step of applying a preset pre-tightening force to draw the spacer wire, and knotting after the wire drawing is completed, so as to ensure that the preset pre-tightening force is constant.

[0015] Further, it further comprises the step of coating a plurality of glue layers on the surface of the preform, and coating the next glue layer when the previous glue layer is in a 90% dry state, so as to improve the adhesion between adjacent glue layers.

[0016] A flexible inflatable material, comprising: A fabric reinforcement layer and a spacer wire, the fabric reinforcement layer being connected by the spacer wire, the connection adopting a wire drawing process, the wire drawing process comprising point single knot type, through end point type and row and column segmented type; A sealing film is coated on the fabric reinforcement layer, and the sealing film comprises multiple layers of glue layers, and the next layer of glue layer is coated when the current layer of glue layer is in a 90% dry state.

[0017] Further, the fabric reinforcement layer is formed by fabric of one or more of aramid (Kevlar® / Twaron®), ultra-high molecular weight polyethylene (UHMWPE, Dyneema® / Spectra®), high-strength polyester (HT-PET), high-strength nylon 66, liquid crystal polymer fiber (LCP, Vectran®), PBO, glass fiber, carbon fiber, and basalt fiber.

[0018] The present application has the following technical effects: The flexible inflatable material has high performance, can adapt to complex mechanical conditions, and keeps the variation of its own performance parameters within a small tolerance, has high geometric precision and stability, has flexibility and strength, has no mechanical defects, is foldable, lightweight, easy to store, and does not affect the high performance of the flexible inflatable material after folding; the interval wire layout in the preparation process can be adjusted according to different stresses to meet the requirements of special-shaped curved surfaces with complex curvature changes; the sealing layer is uniformly stacked, is not easy to leak, is not easy to wrinkle, will not be deformed again, and the multi-layer composite material is not easy to delaminate; the in-plane uniformity and folding durability after air-tight covering are considered; the removable support mold is provided with a wire drawing hole, which reduces the difficulty of the interval wire threading process; the special wire drawing and knotting process realizes adjustable interval wire pretightening force and uniform interval wire pretightening force, and reduces the influence of local interval wire damage on the whole; the overall process steps are simple, the operability is high, the production difficulty is reduced, the production efficiency is improved, and the finished product qualification rate is improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Figure 1 is a process flow diagram of a flexible inflatable material preparation method of the present application; Figure 2 Figure 2 is a schematic diagram of a removable support mold in an embodiment of the present application; Figure 3 Figure 3 is a schematic diagram of a removable support mold in another embodiment of the present application; Figure 4 Figure 4 is a schematic diagram of three wire drawing processes of the present application; Figure 5 Figure 5 is a physical diagram of a flexible inflatable material prepared by the method provided by the present application; REFERENCE SIGNS: 1, wing model; 2, removable support mold; 21, wire drawing hole; 3, interval wire; 4, knot. DETAILED DESCRIPTION

[0020] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0021] Wherein, the same parts are denoted by the same reference numerals. It should be noted that the words "front", "back", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings of the present application specification, and the words "bottom" and "top", "inner" and "outer" refer to the directions towards or away from a particular part. In addition, the terms "first", "second" are used only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more features. In the description of the present application specification, the meaning of "a plurality of" is two or more.

[0022] Embodiment one As shown in Figure 1 A flexible inflatable material preparation method, the method comprising the following steps: A model is established and analyzed based on performance requirements, and the analysis results include the normal stress field and shear stress field of the model; based on the analysis calculation results, the distribution of the spacer wires 3 is calculated; the removable support mold 2 is designed and shaped, and the removable support mold 2 is provided with wire drawing holes 21; a preform is made by using a wire drawing process; the preform is sealed by in-situ glue brushing and film forming; and the removable support mold 2 is removed.

[0023] In this embodiment, the method first establishes a model based on the finished product, and performs finite element stress analysis on the model based on the performance requirements of the finished product, to obtain the normal stress and shear stress distribution of each potential wire drawing node, and to optimize the arrangement direction, spacing and pre-tightening force of the spacer wires 3 and other parameters accordingly; then, the removable support mold 2 is used as a reference for the preform, and the space position of the spacer wires 3 is reserved, the spacer wires 3 are drawn through a specific wire drawing process to make the preform, and then a sealing process of in-situ glue brushing and film forming is combined to realize the preparation of high-pressure high-conformal special-shaped flexible inflatable material with arbitrary matching of curved surfaces.

[0024] In the present embodiment, the model is established and the analysis is performed based on the performance requirements, which specifically includes, first, selecting finite element software ANSYS or Abaqus, establishing a three-dimensional model of the curved surface and the upper and lower skin system based on CAD in the finite element software, and setting the corresponding elastic modulus, Poisson's ratio and other mechanical properties of the skin material; then, the skin is divided into grid attributes such as shell element or solid element, and the grid is further refined in the high-curvature and connection area, the assembly state is simulated by fixing the flexible inflatable material boundary or elastic support, the design internal pressure (≥30 kPa), gravity and possible external aerodynamic load are applied, and preliminary stress-deformation analysis is performed to identify the normal stress and in-plane shear stress concentration area and the maximum bulging deflection point. This step can adjust the parameter settings according to different performance requirements of the finished product, which is not described here.

[0025] According to the analysis results of the three-dimensional model by the software, the distribution of the spacer wire 3 is calculated, and the analysis results include but are not limited to the normal stress field and shear stress field of the model. According to the normal stress contour and shear stress threshold, the layout path of the spacer wire 3 is determined, and the required pre-tightening force of each spacer wire 3 is calculated to realize the cooperative stress of the spacer wire 3 and the skin. Finally, the layout scheme of the spacer wire 3 is reloaded into the model, and the maximum deflection is controlled within ±1 mm and all component stresses are within the allowable range under the same load, so as to determine the position, direction, number and pre-tightening force of the spacer wire 3 and other wire drawing process parameters, which provide reliable basis for the design and formation of the removable support mold 2 and the threading and knotting of the spacer wire 3 in the subsequent steps.

[0026] Then, the removable support mold 2 is designed and formed. The removable support mold 2 can be flexibly designed according to the curved surface and internal spacer wire 3 layout requirements. Chemical reaction type materials such as water-soluble polyvinyl alcohol (PVA), alkali-soluble support resin or acid-soluble copolymer can be selected. After forming, the corresponding solvent (pure water, weak alkali or weak acid) is dissolved and the residual liquid is discharged. Physical removal type materials such as paraffin or low melting point hot melt wax can be used. After forming, the mold is melted and flowed out or phase changed to separate by heating. The above-mentioned removable materials such as chemical reaction type or physical removal type can realize non-destructive demolding after forming, avoiding the damage to the shape and internal support structure of the traditional mechanical demolding of the special-shaped flexible inflatable material.

[0027] The removable support mold 2 can adopt different molding processes according to the material mechanism. For example, for chemical reaction type materials, 3D printing molding, vacuum casting or injection molding is preferred to obtain complex internal cavity structure, and local modification can be made by low speed, dry CNC milling; for physical removal type materials, remelting type stereoscopic printing or compression molding can be used, and then small cutting depth numerical control finishing is carried out under the condition of cold wind atomization cooling to avoid local softening deformation. By flexibly combining the above additive manufacturing, molding casting and numerical control processing means, the removable support mold 2 meeting the needs of different demolding mechanisms can be efficiently prepared under the premise of ensuring the size accuracy and surface consistency.

[0028] After the removable support mold 2 is prepared according to the above steps, the next step of preforming can be carried out. First, select a suitable fabric reinforcement layer. Single component fabrics such as aramid (Kevlar® / Twaron®), ultra-high molecular weight polyethylene (UHMWPE, Dyneema® / Spectra®), high-strength polyester (HT-PET), high-strength nylon 66, liquid crystal polymer fiber (LCP, Vectran®) or PBO can be selected according to actual application requirements. Mixed / interwoven composite fabrics of the above fibers and glass fibers, carbon fibers or basalt fibers can also be used. The fabric organization can be selected from plain weave, 2 / 1 or 3 / 1 twill, rip-stop, warp or weft spaced strong gauze organization and double / multi-layer woven structure. Plain weave or small grid rip-stop plain weave is preferred to balance the uniformity and folding durability after air-tight covering.

[0029] In order to further ensure that the film layer can uniformly infiltrate in the subsequent in-situ glue brushing film sealing process, the surface density of the fabric reinforcement layer is preferably in the range of 50-300 g / m 2 to realize the uniformity of the film layer wrapping the fabric reinforcement layer.

[0030] After the material and density of the fabric reinforcement layer are determined, the preparation process of the fabric reinforcement layer is further optimized. The fabric reinforcement layer can be prepared by weaving, knitting and non-woven. The woven and non-woven fabrics can be prepared by vertical cutting and plate making, and the knitted fabrics can be prepared by integrated knitting. This solves the problem of uneven fitting and easy wrinkling of the fabric reinforcement layer when it is fitted with the removable support mold 2, especially with the complex shaped removable support mold 2.

[0031] Next, a suitable spacer yarn 3 is selected. The spacer yarn 3 can be selected from aramid filaments, ultra-high molecular weight polyethylene (UHMWPE) filaments, or high-strength polyester filaments, and the specifications are limited to: single-filament outer diameter of 0.25-0.70 mm, or multi-filament fineness of 200-600 dtex, tensile strength not less than 6.5 cN / dtex, and preferably aramid or UHMWPE single-filament specific strength ≥20 cN / dtex. If necessary, the yarn surface is treated with silicone oil or low-friction sizing to reduce the threading and knotting resistance.

[0032] After the required material selection is completed, a specific drawing process is used to manufacture a preform, and a removable support mold 2 is used to support the upper and lower fabric reinforcement layers. The removable support mold 2 is pre-set with a drawing path according to the analysis and calculation results of the previous steps, i.e., the spacer yarn 3 is introduced into the hollow area. The spacer yarn 3 is drawn through the predetermined position on the surface of the removable support mold 2 and knotted to form a preform with the removable support mold 2 as the support core, the surface attached with the fabric reinforcement layer, and the two connected and fixed by the spacer yarn 3.

[0033] The threading and knotting of the spacer yarn 3 can be done manually or automatically. Depending on the distribution of the spacer yarn 3 inside the flexible inflatable material, different knotting methods can be used, such as point-like single-knot, through-end, and row-column segmented. The spacer yarn 3 is threaded with a certain pre-tightening force, allowing it to be flexibly arranged according to different local aerodynamic loads and structural requirements, achieving overall adjustability of the spacer yarn 3 in position, length, and pre-tightening force, and improving adaptability and stability.

[0034] Taking the through-end method as an example, one spacer yarn 3 is sequentially threaded through all the predetermined drawing holes 21, and only knotted at the beginning and end of the drawing. The specific process of threading can have multiple derivative schemes. One preferred derivative method is as follows: the spacer yarn 3 is threaded through the guide hole of the threading needle tip and attached to the two sides of the threading needle; then, the threading needle with the spacer yarn 3 passes through the predetermined drawing hole 21 from the upper surface of the removable support mold 2 to the lower surface of the removable support mold 2; at the position of the lower surface of the removable support mold 2, the picking needle is threaded through the gap between the threading needle and the spacer yarn 3 and picks out the spacer yarn 3 to form a loop; then, the picking needle moves the loop outward along the lower surface of the removable support mold 2 to a position below the next predetermined drawing hole 21. Then, the threading needle with the spacer yarn 3 continues to pass through the next predetermined drawing hole 21 from the upper surface of the removable support mold 2, and passes through the loop picked out by the previous drawing hole 21 to achieve the interweaving and closing of the loop and the spacer yarn 3. The above steps are repeated to keep each loop independent of each other, thereby forming a stable and controllable connection method.

[0035] A feasible artificial way to precisely control the pre-tightening force of the spacer wire 3 is to use a portable pre-tightening force control device, such as a portable micro-digital force gauge or a spring dynamometer, to monitor the pre-tightening force in real time during the wire drawing, threading and knotting process. The specific operation steps are as follows: First, fix one end of the spacer wire 3 at the position of the preset wire drawing hole 21; then connect the portable pre-tightening force control device to the other end of the spacer wire 3, and slowly apply a tensile load by hand; when the portable pre-tightening force control device displays that the set pre-tightening force value (such as 3.0 N ± 0.1 N) is reached, fix the spacer wire 3 by knotting; after knotting is completed, use the portable pre-tightening force control device to recheck to ensure the accuracy of the pre-tightening force; if the pre-tightening force deviation exceeds the allowed range, the knot can be untied on site and the above steps can be repeated for adjustment to ensure that the overall structure pre-tightening force control error does not exceed ± 3% of the set value.

[0036] After the preform is completed, the next step is to seal the preform in situ by brushing and forming a film. The sealing material can be prepared into a certain flowable adhesive layer using composite adhesive powder, solvent-based glue, etc. Through multi-layer brushing, spraying and other layer-by-layer stacking methods, the adhesive powder film or glue film is formed. During the process of layer-by-layer stacking of the adhesive layer, the previous layer of adhesive layer is in a 90% dry state, and the next layer of adhesive layer is coated or sprayed to improve the adhesion between adjacent layers. Then, a gas-tight film is formed on the surface of the fabric reinforcement layer to meet the requirements of gas tightness and mechanical properties under different environmental conditions. During the sealing process, an air nozzle is reserved for subsequent inflation and removal of the dissolved residual liquid of the support mold 2.

[0037] In order to achieve the best effect of in-situ brushing and film sealing process, further fine control of film thickness uniformity and film forming drying process is required. Film thickness uniformity can be measured by detection instruments such as non-metal ultrasonic thickness gauge. During the glue scraping process, multi-point measurement is used to ensure film thickness uniformity. After preparation, non-metal ultrasonic thickness gauge is used for non-destructive measurement to verify the film thickness uniformity again. The brushing operation should follow the principle of "small amount and multiple times". The thickness of each coating should not be too large to prevent peeling during the drying process, which may cause the adhesion between the adhesive layer and the fabric substrate to decrease. The environmental temperature can be determined according to the type of adhesive, which is generally controlled at 40-60 ℃, and the relative humidity is maintained at 40-60 %RH. In order to ensure uniform drying and avoid surface defects, a stable air flow rate should be maintained in the space, which is a low-speed laminar flow in the range of 0.2-0.5 m / s to prevent local over-drying or over-wetting.

[0038] During the drying process, the compactness and integrity of the film should be considered: excessive drying can easily lead to surface cracking or edge lifting of the adhesive layer; too high humidity may cause water stains or whitening. After each brushing, 2-3 h of static drying should be carried out, and by accurately controlling the temperature, humidity and wind speed, a suitable drying rate can be achieved. Too fast drying speed may introduce surface shrinkage cracks, and too slow drying speed may easily form pores, significantly reducing the air tightness and pressure resistance of the film layer After the sealing is completed, the removable support mold 2 is removed, the removable support mold 2 is dissolved under corresponding conditions, after the mold is dissolved, the internal residual liquid is discharged through the reserved air nozzle position.

[0039] After the complete dissolution and liquid discharge of the removable support mold 2, the air nozzle and accessories are installed, the air nozzle is welded at the reserved position by ultrasonic high-frequency welding, and then the flexible inflatable material is inflated and unfolded from the air nozzle, so that a flexible inflatable material with high air pressure, stable internal spacing support structure and foldable, lightweight is obtained, realizing rapid deployment and efficient preparation.

[0040] A flexible inflatable material is prepared by the above method, which comprises a fabric reinforcement layer and a spacing wire 3, and a sealing film coated on the surface of the fabric reinforcement layer. The fabric reinforcement layer is connected by the spacing wire 3, and the connection direction is determined according to the actual demand. The connection adopts wire drawing process, which includes point-like single knot type, through end type and row-column segmented type. The sealing film comprises a plurality of adhesive layers, which are prepared by coating the next layer of adhesive on the current layer of adhesive at 90% dryness.

[0041] Example two In this embodiment, a wing model Figure 1 is taken as an example, as shown in Figure 2 , first, a non-porous three-dimensional solid model of the target flexible inflatable material is established in Abaqus software, the fabric reinforcement layer is set as aramid plain fabric, the skin thickness is 0.12 mm, the design internal pressure is 35 kPa, the gravity is 1 g and the equivalent wind pressure is 10 ms-1. According to the high stress zone, 2 mm x 2 mm reference grid is generated on the curved surface, and then the nodes meeting the wire drawing criteria are selected as the positions of the wire drawing holes 21. According to the stress analysis results, the wire drawing hole 21 has a diameter of 2 mm, and the wire drawing hole 21 is arrayed with a distance interval of 2 mm. Then, the 3D modeling paper is sliced into printing paper suitable for 3D printers, and the water-soluble PVA is used as the printing consumables. After the consumables are dried at 50-60℃ for 8 hours, they are put into the printer to obtain water-soluble removable support mold 2. During the 3D printing process, the internal chamber temperature of the printer is 40℃, the hot bed temperature is 50℃, and the nozzle temperature is 210℃.

[0042] Then, the aramid woven plain cloth (gram weight 140 g / m 2As the upper and lower fabric reinforcement layers are laid on the surface of the removable support mold 2 respectively, the fabric reinforcement layers are tightly attached to the surface of the removable support mold 2 through vacuum adsorption, so as to ensure that the fabric reinforcement layers completely conform to the shape of the removable support mold 2. The spacing wire 3 is made of high-strength polyester multifilament with a diameter of 0.3 mm. The spacing wire 3 is drawn through the preset wire drawing hole 21 of the removable support mold 2 by manual wire drawing, and the wire drawing length is 2-45 mm. After the wire drawing is completed, the ends of the spacing wire 3 are knotted with a pre-tightening force of 3 N to form a special-shaped flexible inflatable material preform with aramid woven plain cloth as the fabric reinforcement layer, high-strength polyester multifilament as the spacing wire 3, and the removable support mold 2 as the support core.

[0043] After the preform is completed, a liquid TPU glue is prepared with polycarbonate TPU master batch as solute and DMF as solvent. The liquid glue is applied on the surface of the fabric reinforcement layer in multiple times, and the thickness of the glue is 0.1-0.8 mm. The glue is dried in a 50°C oven, and a film is formed on the surface. During the film forming process, a gas nozzle with a diameter of 8 mm is reserved at the wing root.

[0044] After the film forming is completed, the entire preform is placed in a 40°C ultrasonic water bath, and the PVA mold is dissolved by ultrasonic assisted water dissolution method. The dissolution time is about 6 hours. After the mold is completely dissolved, the residual aqueous solution is discharged through the gas nozzle. After the liquid discharge is completed, the gas nozzle is welded at the reserved gas nozzle position by ultrasonic high-frequency welding.

[0045] Finally, air is filled into the interior through the gas nozzle to an internal pressure of 50 kPa. The special-shaped flexible material is rapidly inflated and expanded to obtain a high-pressure high-shape-retention special-shaped flexible inflatable material with structural stability and foldable recycling.

[0046] Example Three Firstly, a three-dimensional finite element model of the special-shaped flexible inflatable material is established by using Abaqus software: the upper and lower skins are set as PU-coated twill UHMWPE fabric with a grammage of 240 g / m 2 , a thickness of 0.10 mm, E≈65 GPa, and v=0.31; and the material of the removable support mold 2 is SR-35 alkali-soluble polystyrene-blended body with E≈3.5 GPa. In the model, a design internal pressure of 30 kPa is applied, and a 1g self-weight and an equivalent wind pressure of 15 ms-1 (about 115 Pa) are superimposed. According to the stress analysis result, a 1mm×4mm reference grid is generated on the curved surface, 96 high-stress nodes are selected as the perforation positions, and 28 radial main spacing wires 3 and 10 ring-shaped auxiliary spacing wires 3 are planned along the principal stress direction. Through two rounds of iterative optimization, the average wire spacing is controlled in 18-22 mm, the pre-tightening force is adjusted to 1-3 N, the maximum deflection is reduced to 0.95 mm, and the safety factor of all nodes is ≥1.7.

[0047] The 3D modeling drawing obtained from the above simulation analysis contains information such as the arrangement of 21 drawing holes with a diameter of 1 mm and a pitch of 4 mm, and the orientation of the spacer wire 3, and then the sliced 3D modeling drawing of the optimized design in this embodiment is converted into a printing file suitable for FDM 3D printers. An alkali-soluble mold is prepared using Stratasys QSR SR-35 alkali-soluble printing consumables. Before printing, the SR-35 printer operating environment temperature is set to room temperature (about 25°C), and the printing process controls the printing cabin temperature at 60-80°C, the hot bed temperature is set to 90-115°C, and the nozzle temperature is set to 215-225°C, to ensure uniform extrusion and stable accumulation of the consumables, and to ensure the forming precision and the integrity of the mold. After printing is completed, an alkali-soluble removable support mold 2 that meets the requirements of high-aspect-ratio airfoil shape and internal spacer wire 3 arrangement is obtained, which provides a high-precision preforming support structure for subsequent wire drawing, knot tying, and sealing to obtain high-pressure high-shape-retention special-shaped flexible inflatable materials.

[0048] After the completion of the removable support mold 2, choose twill super high woven fabric as the upper and lower fabric reinforcement layer to cover the surface of the removable support mold 2, and ensure that the fabric reinforcement layer fits the complex shape of the removable support mold 2 through the vacuum forming process. The spacer wire 3 is drawn through the removable support mold 2 preset wire drawing hole 21, and the spacer wire 3 uses super high wire (multifilament diameter 0.5 mm), and is fixed by using 1-3 N pre-tightening force, and is knotted after drawing, to ensure that the spacer wire 3 effectively supports the upper and lower fabric reinforcement layers during the production of the preform, while avoiding local indentation or mold deformation. In addition, the wire drawing length (18-22 mm) and pre-tightening force can be flexibly adjusted according to the local structure requirements to complete the production of the preform.

[0049] Then the preform is sealed, and composite PC glue with a thickness of 0.2 mm is spread on the surface of the preform, and each side is heated at 180°C for 4 minutes, so that the glue powder melts and flows on the surface of the preform to form a continuous and dense film layer, and then it is naturally cooled to room temperature to complete the film formation, forming a thermoplastic polycarbonate film that is well combined with the fabric reinforcement layer, with good flexibility and air tightness. The pre-set diameter 10 mm air nozzle position is used for subsequent liquid discharge and inflation during the sealing process.

[0050] After sealing is completed, the preform is immersed in a NaOH solution (concentration of 1-2 wt%) and Ecoworks surfactant (0.5-1 wt%) dissolving solution, and soaked at 70°C for 6 hours to dissolve the alkali-soluble removable support mold 2. The residual alkali solution is discharged through the reserved air nozzle position and washed with pure water until the liquid is clear. After the liquid is discharged, the air nozzle is welded at the reserved air nozzle position by ultrasonic high-frequency welding.

[0051] Finally, the inside is inflated to 20 kPa internal pressure by the air nozzle, and after the inflation is completed, the special-shaped flexible inflatable material is deployed, and the high-pressure high-shape-retaining special-shaped flexible inflatable material is prepared.

[0052] Example Four Example Four is further optimization of the distribution calculation of the spacer wire 3 based on the three preceding examples. For different stress conditions, the present application uses a finite element analysis method to determine the position and density of the wire drawing holes. First, a special-shaped curved surface model is established in the finite element software ANSYS or Abaqus, the material properties and boundary conditions of the model are set, different internal pressure loads are applied for simulation analysis, and the analysis results at least include the normal stress field and the shear stress field. According to the analysis results, the model is divided into regions and classified. In this embodiment, if the normal stress is > 1.5 MPa or the shear stress is > 0.8 MPa, the region is divided into a high stress zone; if the normal stress is between 1.0-1.5 MPa or the shear stress is between 0.5-0.8 MPa, the region is divided into a medium stress zone; if the normal stress is < 1.0 MPa and the shear stress is < 0.5 MPa, the region is divided into a low stress zone. It should be noted that for different structures and different stress environments, the stress region division can be adjusted accordingly. The numerical values are only one possible embodiment and do not limit the method.

[0053] Further optimization, after the model is divided into regions, the wire drawing holes 21 can be designed for different stress regions respectively, such as Figure 3 In one possible embodiment, the hole spacing in the high stress zone is set to 2-4 mm, and high-density cross arrangement is used; the hole spacing in the medium stress zone is set to 5-8 mm, and linear or ring arrangement with medium density is used; the hole spacing in the low stress zone is set to ≥10 mm or no hole is set; the arrangement of the wire drawing holes 21 should be preferentially along the principal stress direction of the structure, and the hole arrangement position should avoid sharp turning points. If it cannot be avoided, the local hole density or cross arrangement needs to be increased; Example Five Example Five is further optimization of the wire drawing process based on the preceding examples. Due to the complex stress of the special-shaped flexible inflatable material, different regions need to be used for targeted wire drawing process, such as Figure 4The embodiment provides three different wire drawing processes: point single knot type, through end point type and row and column segmented type. The point single knot type is that the spacer wire 3 is drawn from the back of the fabric reinforcement layer at each preset wire drawing hole 21 and a single loop knot node 4 is formed on the side of the wire drawing hole 21, so that accurate positioning and adjustable pre-tightening force are realized; the row and column segmented type is that the spacer wire 3 is drawn and knotted every several wire drawing holes 21 in the row or column direction, and a segmented support structure is formed, so that the strength and flexibility of the large-span area are considered; the through end point type is that one spacer wire 3 penetrates all preset wire drawing holes 21 in turn, and is finally fixed through a loop knot or double loop knot node 4 at the end, and is suitable for application requirements of maintaining the overall tension of the whole spacer wire 3. During the wire drawing process, preset pre-tightening force needs to be applied, and any one of the three wire drawing processes is adopted according to specific requirements, and the knot is tied after the wire drawing is completed, so that the applied pre-tightening force can be kept constant.

[0054] Comparative example In the method provided by the application, in-situ glue brushing and film sealing are adopted. In order to further verify that the sealing process of the application has a significant beneficial effect compared with the traditional TPU calendering process, part of the key performance indicators are compared and tested, as shown in the following table: Through the comparison of key parameters and in combination with the physical object as shown in Figure 5 It can be known that the in-situ glue brushing and film sealing of the application fully immerse into the fabric fiber pores through capillary wicking, the film and fabric interface bonding strength is high, the film thickness is continuous and uniform, and there is no obvious interface stress gradient between the film and the fabric.

[0055] In comparison, in the traditional TPU calendering process, whether it is hot pressing or rolling process, since the film layer needs to be compounded on the fabric in a flat state, obvious lap thickness unevenness easily occurs in the corner or complex curved surface area, local stress concentration points are generated, thereby reducing the peeling performance and increasing the risk of bubbling and local bulging.

Claims

1. A method for preparing a flexible inflatable material, characterized in that, The method includes: S1 establishes a model and performs analysis based on performance requirements. The analysis results include the normal stress field and shear stress field of the model. S2 spacer distribution calculation; S3 is designed and formed with a removable support mold, and the removable support mold is provided with a wire drawing hole; S4 preform fabrication: Preforms are fabricated using a wire drawing process; S5 in-situ adhesive application for film sealing; S6 removable support mold removal.

2. The method for preparing flexible inflatable material according to claim 1, characterized in that, S2 further includes: the analysis results based on S1, S21 divides the model into regions and classifies the regions; S22 features separate wire drawing holes designed for different areas.

3. The method for preparing flexible inflatable material according to claim 2, characterized in that, S21 further includes S211: If the normal stress in the model region is greater than σ1 MPa or the shear stress is greater than T1 MPa, then the region is classified as a high-stress region. If the normal stress in the model region is between σ2 and σ1 MPa or the shear stress is between T2 and T1 MPa, then the region is classified as a medium stress region. If the normal stress in the model region is less than σ² MPa and the shear stress is less than T² MPa, then the region is classified as a low-stress region. Where σ2 < σ1, T2 < T1.

4. The method for preparing flexible inflatable material according to claim 3, characterized in that, S22 further includes S221: The hole spacing in the high-stress zone is set to L1-L2 mm, and a high-density cross arrangement is adopted. The hole spacing in the medium stress zone is set to L3-L4 mm, and is set in a medium density linear or circumferential manner. The hole spacing in the low-stress zone is set to ≥L5 mm or no holes are set. Where L1 < L2 < L3 < L4 < L5.

5. The method for preparing flexible inflatable material according to claim 1, characterized in that, The S4 further includes: S41 lays the fabric reinforcement layer on the surface of the removable support mold and uses vacuum adsorption to make the fabric reinforcement layer adhere tightly to the surface of the removable support mold. S42 employs a different drawing process, drawing spacer yarns through the drawing holes and fabric reinforcement layer, thus fixing the fabric reinforcement layer to the surface of the removable support mold.

6. The method for preparing flexible inflatable material according to claim 5, characterized in that, S42 further includes: the wire drawing process includes: Dotted single knot type: The spacer wire forms a single loop knot on each preset drawing hole side to achieve precise positioning and preload adjustment; Segmented row and column type: According to the preset wire drawing path, the wires are threaded through several preset wire drawing holes and then knotted to form a segmented support structure, which is used to balance the strength and flexibility of large span areas. Through-end type: A spacer wire passes through all the predetermined drawing holes in sequence, and is fixed at the end of the drawing by a loop or double ring knot to maintain the overall tension of the entire spacer wire.

7. The method for preparing flexible inflatable material according to claim 6, characterized in that, The S42 further includes: applying a preset pre-tightening force to thread the spacer wire, and knotting it after drawing the wire to ensure that the preset pre-tightening force is constant.

8. The method for preparing flexible inflatable material according to claim 1, characterized in that, The S5 in-situ adhesive film-forming sealant also includes: Multiple layers of adhesive are applied to the surface of the preform. The next layer of adhesive is applied when the previous layer is 90% dry, in order to improve the adhesion of adjacent adhesive layers.

9. A flexible inflatable material, characterized in that, The flexible inflatable material is made according to any one of claims 1 to 9, wherein the material comprises: The fabric reinforcement layer and spacer yarns are connected by the spacer yarns. The connection is made by a drawing process, which includes point-like single-knot type, through-end point type and row-column segmented type. A sealing film is coated on the fabric reinforcement layer. The sealing film comprises multiple adhesive layers, with the next adhesive layer being coated when the current adhesive layer is 90% dry.

10. The flexible inflatable material according to claim 9, characterized in that, The fabric reinforcement layer is a fabric formed from one or more of the following: aramid (Kevlar® / Twaron®), ultra-high molecular weight polyethylene (UHMWPE, Dyneema® / Spectra®), high-strength polyester (HT-PET), high-strength nylon 66, liquid crystal polymer fiber (LCP, Vectran®), PBO, glass fiber, carbon fiber, and basalt fiber.

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