A large composite pressure shell mold yarn parameter longitudinal winding low overlap layer design method

Abstract

This invention discloses a method for designing a low-overlapping layup of yarn parameters for longitudinal winding of a large composite pressure-resistant shell mold, belonging to the field of composite material technology. The method includes the following steps: determining the winding mold, yarn, and working parameters for the large composite pressure-resistant shell; constructing a mold model; setting the number of yarn balls, yarn spread width, initial winding angle, and interface friction coefficient; generating an initial longitudinal winding program and determining the initial number of cutting points; optimizing the winding angle; determining if the initial number of cutting points is ≤2; if it is greater than 2, using the initial angle α as a reference, fine-tuning in 0.1° increments to re-verify the number of cutting points; adjusting the friction coefficient to optimize the trajectory; if the angle adjustment does not meet the standard, fine-tuning the friction coefficient within the range of 0.15-0.3; optimizing the trajectory of variable cross-section, end angle, and yarn intersection area; iterating until the number of cutting points is ≤2; controlling the starting point and cycle number after the qualified program; prohibiting continuous longitudinal winding of 2 cycles or more, with 1-2 circumferential layups after each longitudinal layup layer.

Description

Technical Field

[0001] This invention belongs to the field of composite material molding technology, specifically relating to a method for designing longitudinal winding low-overlap layer layup of yarn parameters for a large composite pressure-resistant shell mold. Background Technology

[0002] Large composite pressure hulls are core pressure-bearing components of deep-sea equipment, enduring harsh conditions such as external pressure, seawater corrosion, and fatigue loads over long periods. This places extremely high demands on the hull's density, uniformity, interlayer bonding strength, and overall mechanical stability. Currently, the industry commonly uses the carbon fiber wet winding process to fabricate large pressure hulls, as this process offers high forming efficiency, controllable fiber orientation, and good overall strength.

[0003] However, during the longitudinal winding process, due to the large shell diameter, long length, numerous yarn bundles, narrow single yarn spread width, low axial tension, and long stroke, problems such as yarn overlap, localized gaps, slippage, uneven yarn spread, and interlayer separation are prone to occur. Overlapping will cause local thickness deviations and stress concentration; gaps will form internal voids, increase porosity, and reduce mechanical properties; slippage and separation will directly lead to unstable longitudinal layup and poor bonding at the circum-longitudinal interface, seriously affecting the pressure-bearing capacity and service life of the pressure-resistant shell.

[0004] Existing technologies largely rely on experience to manually adjust angles, trajectories, and layup sequences, lacking a systematic, quantifiable, and software-optimizable longitudinal winding design method. This results in poor process repeatability, low product consistency, and high scrap rates. Therefore, there is an urgent need for a design method that can precisely control the number of cutting points, suppress overlapping and gaps, uniformly disperse longitudinal layups, and improve process stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a design method for longitudinal winding of yarn parameters with low overlap in large composite pressure-resistant shell molds. Through parametric modeling, software optimization, coordinated adjustment of angle and friction coefficient, and uniform arrangement of layup, the number of longitudinal winding cutting points is controlled to ≤2, which significantly reduces overlap and improves the density, uniformity and overall performance of the shell.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution: On one hand, the present invention provides a method for designing longitudinal winding low-overlap layer ply of yarn parameters for large composite pressure-resistant shell molds, characterized by comprising the following steps: Step S1: Determine the winding mold parameters, yarn parameters, and working condition parameters corresponding to the large composite pressure-resistant shell. Input the obtained parameters into CADWIND software to build the mold model, set the number of yarn balls, the single yarn spreading width, the initial winding angle, and the interface friction coefficient, initially generate the longitudinal winding program, and determine the initial number of cutting points. Step S2: Optimize the winding angle and adjust the number of cutting points. Determine if the initial number of cutting points is ≤2. If it is greater than 2, take the initial longitudinal winding angle α as the reference and fine-tune the winding angle in 0.1° increments within the range of ±α×5%. Regenerate the longitudinal winding program and verify the number of cutting points. Step S3: Based on the winding angle and the number of cutting points, optimize the trajectory by adjusting the friction coefficient. If adjusting the winding angle alone cannot make the number of cutting points ≤ 2, fine-tune the interface friction coefficient within the range of 0.15-0.3, and simultaneously optimize the longitudinal winding motion trajectory of the mold cross section, end corner and yarn intersection area. Repeat steps S2-S3 until a qualified longitudinal winding program with the number of cutting points ≤ 2 is generated. Step S4: Import the qualified longitudinal winding program into the winding machine as a subroutine, set the main program to control the winding start point and number of cycles of the subroutine; follow the layup rules to prohibit continuous longitudinal winding of 2 cycles or more, and lay 1-2 circumferential layups after each longitudinal layup is completed to complete the overall winding and suppress overlapping and bridging.

[0007] Furthermore, in step S1, the diameter of the winding mold is ≥800mm, the mold length is ≥6m, and the shell wall thickness is ≥50mm; the number of yarn spools is ≥6, and the single yarn spreading width is 2.5-5mm; the initial setting value of the interface friction coefficient is 0.15-0.3; the mold length is calculated according to the formula: mold length = product length + 100mm + product thickness / 10mm × 40.

[0008] Furthermore, the number of yarn spools is determined according to the formula: ; In the formula, N s The number of yarn spools represents a positive integer; t represents the shell wall thickness in mm; when the number of yarn spools... N s When the number of yarn clusters is ≥6, the spread width of a single yarn is preset to 2.5-3mm. The larger the number of yarn clusters, the smaller the spread width of a single yarn.

[0009] Furthermore, in step S4, after winding is completed, the deviation between the longitudinal program center and the mold center is ≤ ± mold length × 0.2% mm; the longitudinal winding cycle number needs to be increased by 1-2 pieces based on the software output cycle number M, that is, set to M +1 or M +2, and the first 1-2 unstable yarn pieces are removed after winding.

[0010] Furthermore, the methods for setting the layup parameters include: Let the shell's circumferential thickness be A, longitudinal thickness be B, circumferential single-layer thickness be a, longitudinal single-layer thickness be b, circumferential layer number X = A / a, and longitudinal cycle number Y = B / b; after removing the first 4 circumferential layers and the surface 8 circumferential layers, the number of intermediate circumferential layers is (X-12) / Y, and the layering sequence is: 4 circumferential layers, 1 longitudinal cycle, (X-12) / Y circumferential layers, 1 longitudinal cycle, ..., 8 circumferential layers to finish.

[0011] Furthermore, in step S3, for the yarn bending area at the corner of the mold end, the curvature change area at the cross-section, and the area where multiple yarns intersect and overlap, the yarn path is adjusted to make the yarn closely fit the mold surface, eliminating the risk points of local overlap and gaps.

[0012] Furthermore, in step S2, the winding angle adjustment has a higher priority than the friction coefficient adjustment. When adjusting, the winding angle is first coarsely adjusted in 0.5° increments to lock the downward trend of the number of cutting points, and then finely adjusted in 0.1° increments to the target number of cutting points.

[0013] Furthermore, the large composite pressure-resistant shell is a cylindrical deep-sea pressure-bearing shell with an inner diameter ≥800mm, a wall thickness ≥50mm, and a product length ≥6000mm, and is formed by wet winding of T700 or T800 carbon fiber.

[0014] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: The method for designing longitudinal winding low-overlap ply layup of yarn parameters for large composite pressure-resistant shell molds provided by this invention, through software parametric modeling, fine-tuning of angles by ±5%, and collaborative optimization of friction coefficient, stably controls the number of longitudinal cutting points to ≤2, resulting in neat, smooth, and tightly bonded yarn arrangement. This eliminates overlapping, gaps, and suspension defects at the source, significantly reducing porosity. The method employs alternating ring and longitudinal layup, prohibiting continuous longitudinal winding, ensuring uniform dispersion and real-time compaction of longitudinal layers, balancing the anisotropy of carbon fibers, and improving the shell's pressure-bearing strength, interlaminar shear strength, and fatigue resistance, making it suitable for high-pressure deep-sea conditions. Standardized parameters and software-driven design reduce reliance on manual experience; starting point positioning, cycle number setting, and layup sequence are all quantifiable and controllable, avoiding slippage and uneven yarn spreading problems. This method is suitable for large-scale production of large shells, covering different wall thicknesses and yarn counts, and offers strong process operability. Attached Figure Description

[0015] Figure 1 The flowchart illustrates a method for designing a long-term winding low-overlap layer layout of yarn parameters for a large composite pressure-resistant shell mold, as provided in an embodiment of the present invention.

[0016] Figure 2 This is a schematic diagram of a longitudinal program header with 10 cutting points, provided as an embodiment of the present invention.

[0017] Figure 3This is a schematic diagram of the actual winding situation of a longitudinal program with 10 tangent points, provided as an embodiment of the present invention.

[0018] Figure 4 This is a schematic diagram of a longitudinal program header with one cutting point, provided as an embodiment of the present invention.

[0019] Figure 5 A schematic diagram (front view) of the actual winding situation of a longitudinal program with 1 tangent point, provided for an embodiment of the present invention.

[0020] Figure 6 A schematic diagram (45° plane) of the actual winding situation of a longitudinal program with 1 tangent point provided for an embodiment of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0022] like Figure 1 As shown in the figure, this embodiment of the invention provides a method for designing the longitudinal winding low-overlap layer of yarn parameters for a large composite pressure-resistant shell mold, characterized by including the following steps: Step S1: Determine the winding mold parameters, yarn parameters, and working condition parameters corresponding to the large composite pressure-resistant shell. Input the obtained parameters into CADWIND software to build the mold model, set the number of yarn balls, the single yarn spreading width, the initial winding angle, and the interface friction coefficient, initially generate the longitudinal winding program, and determine the initial number of cutting points. Step S2: Optimize the winding angle and adjust the number of cutting points. Determine if the initial number of cutting points is ≤2. If it is greater than 2, take the initial longitudinal winding angle α as the reference and fine-tune the winding angle in 0.1° increments within the range of ±α×5%. Regenerate the longitudinal winding program and verify the number of cutting points. Step S3: Based on the winding angle and the number of cutting points, optimize the trajectory by adjusting the friction coefficient. If adjusting the winding angle alone cannot make the number of cutting points ≤ 2, fine-tune the interface friction coefficient within the range of 0.15-0.3, and simultaneously optimize the longitudinal winding motion trajectory of the mold cross section, end corner and yarn intersection area. Repeat steps S2-S3 until a qualified longitudinal winding program with the number of cutting points ≤ 2 is generated. Step S4: Import the qualified longitudinal winding program into the winding machine as a subroutine, set the main program to control the winding start point and number of cycles of the subroutine; follow the layup rules to prohibit continuous longitudinal winding of 2 cycles or more, and lay 1-2 circumferential layups after each longitudinal layup is completed to complete the overall winding and suppress overlapping and bridging.

[0023] In this embodiment, the large composite pressure shell, designed using the longitudinal winding low-overlap layer design method for the yarn parameters of the large composite pressure shell mold, is a core pressure-bearing component in the deep-sea equipment system that bears external pressure, provides spatial sealing, and protects equipment. Its geometric dimensions are an inner diameter of 800mm, a designed wall thickness of 200mm, and an effective working length of 6000mm. The overall structure is a cylindrical rotating body. The molding process uses T700-12K carbon fiber wet winding technology, which has significant advantages such as high molding efficiency, controllable fiber orientation, strong overall structural integrity, and excellent mechanical properties. It can adapt to the harsh working environment of deep-sea high pressure, high humidity, corrosion, and long-term fatigue load.

[0024] Before formally carrying out the winding process design, it is necessary to first systematically determine the structural parameters of the large composite pressure-resistant shell mold, the yarn process parameters, and the interface contact parameters. Precise parameter setting is the basic prerequisite for achieving the goal of low overlap and minimal overhead in longitudinal winding. The values ​​are all quantitatively calculated based on engineering empirical formulas to ensure that the parameter values ​​have engineering operability and process stability.

[0025] Specifically, the length of the large composite pressure-resistant shell mold is equal to the sum of the product length and a 100mm process allowance, plus a 40mm extension compensation for every 10mm of product wall thickness. In this embodiment, the product length is 6000mm and the product wall thickness is 200mm. Substituting these values ​​into the formula, the mold length is calculated as 6000mm + 100mm + (200mm ÷ 10mm) × 40mm, ultimately determining the mold length to be 6900mm. The outer diameter of the mold is consistent with the inner diameter of the shell and is set to 800mm. The mold is made entirely of rigid metal, and its surface undergoes high-precision machining and demolding treatment to ensure yarn adhesion during winding and smooth implementation of the subsequent demolding process.

[0026] In this embodiment, the determination of yarn process parameters needs to take into account the upper limit of the mechanical performance of the winding equipment, the production efficiency optimization target, and the product quality stability requirements. The number of yarn spools is determined by calculation based on an empirical formula, that is, the number of yarn spools is equal to the sum of the base value of 6 and the incremental value corresponding to every 10mm of shell wall thickness.

[0027] The shell wall thickness is 200mm. Substituting this into the formula... ; N s The number of yarn spools represents a positive integer; t represents the shell wall thickness in mm; when the number of yarn spools... N s When the number of yarn spools is ≥6, the preset width of a single yarn spread is 2.5-3mm. The larger the number of yarn spools, the smaller the width of a single yarn spread. The number of yarn spools can be obtained. N sThe number of yarn spools is 26. This number of spools fully utilizes the multi-spool synchronous yarn unfolding capability of the winding machine while avoiding potential risks such as uneven tension, disordered yarn unfolding, and overloading of the equipment caused by an excessive number of spools. The unfolding width of a single yarn is matched and set according to the number of yarn spools. When the number of yarn spools is not less than 6, the unfolding width of a single yarn is in the range of 2.5mm to 3mm. As the number of yarn spools increases, the unfolding width of a single yarn needs to be selected accordingly to ensure the compactness and uniformity of the yarn arrangement. In this embodiment, the number of yarn spools is 26, which is significantly higher than the benchmark value. Therefore, the unfolding width of a single yarn is set to 2.75mm. This value is an empirical preset value. It needs to be finely adjusted on-site based on the mechanical precision of the actual yarn unfolding mechanism of the winding machine, the stability of tension control, and the extensibility characteristics of the yarn itself to ensure that the edges of the unfolded yarn are flat, without wrinkles, tears, or overlaps.

[0028] In this embodiment, after the quantification and determination of mold parameters and yarn parameters are completed, the software modeling and initial program generation stage is entered. This embodiment selects the mainstream CADWIND winding simulation software (version V5.8) as the process design tool. The software has core functions such as parametric modeling, trajectory simulation, tangent point calculation and program output, which can provide accurate digital support for the optimization of longitudinal winding process.

[0029] First, the established basic parameters, such as the outer diameter of the mold (800mm), the mold length (6900mm), the number of yarn balls (26), and the single yarn spreading width (2.75mm), are completely input into the software system to construct a three-dimensional digital model that is completely consistent with the actual mold geometry.

[0030] Subsequently, T700-12K carbon fiber was selected from the software material library as the reinforcing material, and epoxy resin matrix was selected as the impregnation system. The initial longitudinal winding angle was set to 24°, and the initial value of the interface friction coefficient was set to 0.2. This friction coefficient is within a reasonable range of 0.15 to 0.3, which can truly reflect the actual contact friction state between the carbon fiber yarn and the metal surface of the mold.

[0031] After inputting the parameters, the software's automatic longitudinal winding program generation module is activated. The software performs trajectory calculations based on geometric algorithms and mechanical simulation logic, ultimately outputting the initial longitudinal winding program. After analysis by the software's backend, the initial program corresponds to 10 longitudinal winding tangent points. From the simulation top-down view, it is clearly observed that the yarn arrangement exhibits a large number of overlapping points, a scattered distribution, and locally dense interweaving. The yarn direction shows obvious bends and intersections, and some areas have suspended yarns, posing a significant risk of overlap and suspension. If this program is directly used for actual winding, it will inevitably lead to quality defects such as local thickness deviations in the shell, increased internal porosity, and decreased interlayer bonding strength. This would completely fail to meet the high density and high mechanical performance requirements of large composite pressure-resistant shells, necessitating subsequent parameter optimization.

[0032] To address the issue that the number of initial program cut points far exceeds the control target (≤2), this embodiment prioritizes a collaborative optimization strategy that uses the longitudinal winding angle as the primary factor and the interface friction coefficient as a secondary factor. Following the technical logic of prioritizing the primary factor, coarse-grained optimization, and gradually approaching the optimal solution, this approach can efficiently achieve precise control of the number of cut points while ensuring process feasibility.

[0033] First, the winding angle is finely adjusted, and the adjustment range is strictly limited to ±5% of the initial angle. In this embodiment, the initial angle is 24°, and the calculated adjustment range is 22.8° to 25.2°. This range ensures the effectiveness of the angle adjustment and avoids problems such as winding trajectory distortion, yarn tension loss and loss of process feasibility caused by excessive angle deviation.

[0034] The angle adjustment process is divided into two stages: coarse adjustment and fine adjustment. In the coarse adjustment stage, a large step size of 0.5° is used for exploratory adjustments to quickly determine the overall trend of the number of tangent points changing with the angle. In this embodiment, after the angle is initially adjusted to 24.5°, the software simulation results show that the number of tangent points shows a significant downward trend, thus determining that positive angle adjustment is an effective optimization direction.

[0035] After locking the effective adjustment direction, the fine-tuning stage begins, using an extremely small step size of 0.1° for successive fine adjustments. After each adjustment, the longitudinal winding program is regenerated and the corresponding number of cutting points is read. The process is continuously iterated and optimized until the number of cutting points is reduced to within the target range.

[0036] When the longitudinal winding angle is finely adjusted to 24.8°, the number of cutting points corresponding to the optimized longitudinal winding program output by the software is 1, which fully meets the control requirement of ≤2. It can be intuitively observed from the simulation top view and the three-dimensional isometric view that the optimized yarn arrangement has the characteristics of regular direction, smooth transition, single and concentrated overlapping points, and close contact between the yarn and the mold surface. There is no obvious suspended area, the risk of overlapping and suspension is fundamentally suppressed, and the trajectory shape has excellent process feasibility.

[0037] After optimizing the winding angle and obtaining the qualified number of cutting points, it is necessary to further verify the interface friction coefficient to ensure the compatibility between process parameters.

[0038] In this embodiment, after angle optimization, the interface friction coefficient is kept unchanged at the initial set value of 0.2. The software simulation results show that the yarn bonding state in the corner area of ​​the mold end, the area of ​​sudden change in curvature of the variable cross section, and the area where multiple yarns intersect is good, with no local suspension, curling or slippage. The smoothness and stability of the trajectory meet the process requirements, and no additional adjustment to the friction coefficient is required.

[0039] If the number of cut points cannot be obtained by angle optimization alone under other working conditions, the friction coefficient needs to be adjusted in the range of 0.15 to 0.3 with an initial step size of 0.1. Then, the angle is combined with coordinated fine-tuning until the optimal match between the number of cut points, the winding angle and the friction coefficient is achieved, while ensuring the tightness of the longitudinal winding trajectory in the key area of ​​the mold.

[0040] After the qualified longitudinal winding program is generated, the process parameters for layup are set and the actual winding is executed. Through a scientific and reasonable layup layout design, the uniform dispersion of the longitudinal layup and the compaction and strengthening of the circumferential layup are achieved, further suppressing the overlapping and overhead defects from the process execution level.

[0041] First, the winding program is imported and its positioning accuracy is controlled. The optimized longitudinal winding program with one cutting point is imported as a subroutine into the winding machine control system. Simultaneously, a main program is written to precisely control the winding start point and cycle number of the subroutine. The positioning accuracy of the winding start point directly affects the symmetry and uniformity of the longitudinal yarn. After winding, the deviation between the longitudinal program center and the die center must not exceed (±die length × 0.2%). In this embodiment, the die length is 6900mm, and the calculated maximum allowable deviation is ±13.8mm. In actual operation, the high-precision positioning system of the winding machine and the laser alignment device work together to ensure that the starting point deviation is strictly controlled within the allowable range, avoiding problems such as yarn offset, local accumulation, or excessive gaps caused by positioning deviation.

[0042] The setting of the number of longitudinal winding cycles should fully consider the instability characteristics of the preceding yarns during the longitudinal winding process of large composite material shells. Due to the large shell length, long axial stroke, and significant yarn tension attenuation, the first 1 to 2 yarns in the longitudinal winding are prone to slippage, uneven yarn spreading, edge separation, and poor bonding with subsequent yarns.

[0043] To ensure the quality stability of the effective working layer of the shell, in this embodiment, the actual number of cycles needs to be increased by 1 to 2 layers based on the theoretical number of cycles M output by the software, that is, set to M+1 or M+2.

[0044] In this embodiment, considering the process characteristics of large composite material shells, such as large single-layer thickness, low axial tension, and high difficulty in interlayer bonding, the uniform distribution and real-time compaction of longitudinal layers are achieved by setting the interval of circumferential layup.

[0045] First, based on the shell structure design parameters, the basic parameters of the circumferential and longitudinal ply layup are quantitatively calculated. Let the total circumferential thickness of the shell design be A, the total longitudinal thickness be B, the thickness of a single circumferential winding layer be a, and the thickness of a single longitudinal winding layer be b. Then, the required total number of circumferential layers X = A / a, and the required total number of longitudinal loops Y = B / b.

[0046] In this embodiment, the total circumferential thickness is designed to be 160mm, the thickness of a single circumferential layer is 0.2mm, and the total number of circumferential layers X is calculated to be 800. The total longitudinal thickness is designed to be 40mm, the thickness of a single longitudinal layer is 0.4mm, and the total number of longitudinal cycles Y is calculated to be 100.

[0047] In the layup arrangement, four circumferential layups are first laid as the head layer, which serves to level the mold surface, strengthen the initial interface, and support the subsequent longitudinal layup base; then the middle section alternating layup stage is entered, and after each cycle of longitudinal layup is completed, (X−12) / Y layers of circumferential layups are laid at intervals.

[0048] In this embodiment, after deducting the 4-layer top layer and 8-layer top layer circumferential layup, the effective number of intermediate circumferential layers is 788. Dividing this by the longitudinal cycle number of 100, the circumferential interval between each two longitudinal layups is calculated to be approximately 8 layers. Through this interval circumferential layup, the longitudinal yarns are compacted, fixed, and integrated in a timely manner, effectively eliminating the risk of slippage, separation, and bridging of the longitudinal yarns. At the same time, the longitudinal layup is evenly distributed throughout the entire shell wall thickness range, balancing the anisotropic properties of the composite material and improving the overall mechanical properties of the shell. After all the intermediate alternating layups are completed, the final 8 layers of circumferential layup are laid as the top layer, which serves to seal the edges, smooth the surface, strengthen the structure, and provide protection.

[0049] After all process parameters have been precisely set, the wet winding equipment is started and the actual winding operation is executed according to the collaborative control logic of the main program and subprograms. During the winding process, the amount of resin impregnation, yarn tension stability, yarn spreading uniformity and compaction roller pressure are strictly controlled to ensure that each layer of yarn is fully impregnated with resin, tightly bonded, without wrinkles, bubbles and slippage.

[0050] After the winding process is completed, the shell and mold are moved into the curing oven as a whole. The oven is heated, kept warm, and cooled according to the preset curing regime to fully cross-link and cure the resin matrix, forming a dense and stable composite material structure. After curing, the shell is demolded, the surface is trimmed, the dimensions are inspected, and non-destructive testing is performed. Finally, a large composite pressure-resistant shell with low overlap, no gaps, dense and uniform structure, and excellent mechanical properties is obtained, which fully meets the requirements for long-term safe use under deep-sea high-pressure conditions.

[0051] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for designing longitudinal winding low-overlap layer layup of yarn parameters for a large composite pressure-resistant shell mold, characterized in that, Includes the following steps: Step S1: Determine the winding mold parameters, yarn parameters, and working condition parameters corresponding to the large composite pressure-resistant shell. Input the obtained parameters into CADWIND software to build the mold model, set the number of yarn balls, the single yarn spreading width, the initial winding angle, and the interface friction coefficient, initially generate the longitudinal winding program, and determine the initial number of cutting points. Step S2: Optimize the winding angle and adjust the number of cutting points. Determine if the initial number of cutting points is ≤2. If it is greater than 2, take the initial longitudinal winding angle α as the reference and fine-tune the winding angle in 0.1° increments within the range of ±α×5%. Regenerate the longitudinal winding program and verify the number of cutting points. Step S3: Based on the winding angle and the number of cutting points, optimize the trajectory by adjusting the friction coefficient. If adjusting the winding angle alone cannot make the number of cutting points ≤ 2, fine-tune the interface friction coefficient within the range of 0.15-0.3, and simultaneously optimize the longitudinal winding motion trajectory of the mold cross section, end corner and yarn intersection area. Repeat steps S2-S3 until a qualified longitudinal winding program with the number of cutting points ≤ 2 is generated. Step S4: Import the qualified longitudinal winding program into the winding machine as a subroutine, set the main program to control the winding start point and number of cycles of the subroutine; follow the layup rules to prohibit continuous longitudinal winding of 2 cycles or more, and lay 1-2 circumferential layups after each longitudinal layup is completed to complete the overall winding and suppress overlapping and bridging.

2. The method for designing longitudinal winding low-overlap layer ply of yarn parameters for large composite pressure-resistant shell molds according to claim 1, characterized in that, In step S1, the diameter of the winding mold is ≥800mm, the mold length is ≥6m, and the shell wall thickness is ≥50mm; the number of yarn balls is ≥6, and the single yarn spreading width is 2.5-5mm; the initial setting value of the interface friction coefficient is 0.15-0.3; the mold length is calculated according to the formula: mold length = product length + 100mm + product thickness / 10mm × 40.

3. The method for designing longitudinal winding low-overlap layer ply of yarn parameters for large composite pressure-resistant shell molds according to claim 2, characterized in that, The number of yarn spools is determined by the formula: ； In the formula, N s The number of yarn spools represents a positive integer; t represents the shell wall thickness in mm; when the number of yarn spools... N s When the number of yarn clusters is ≥6, the spread width of a single yarn is preset to 2.5-3mm. The larger the number of yarn clusters, the smaller the spread width of a single yarn.

4. The method for designing longitudinal winding low-overlap layer ply of yarn parameters for large composite pressure-resistant shell molds according to claim 1, characterized in that, In step S4, after winding is completed, the deviation between the longitudinal program center and the mold center is ≤ ± mold length × 0.2% mm; the longitudinal winding cycle number needs to be increased by 1-2 pieces based on the software output cycle number M, that is, set to M +1 or M +2, and the first 1-2 unstable yarn pieces are removed after winding.

5. The method for designing longitudinal winding low-overlap layer ply of yarn parameters for large composite pressure-resistant shell molds according to claim 4, characterized in that, Methods for setting layup parameters include: Let the shell's circumferential thickness be A, longitudinal thickness be B, circumferential single-layer thickness be a, longitudinal single-layer thickness be b, circumferential layer number X = A / a, and longitudinal cycle number Y = B / b; after removing the first 4 circumferential layers and the surface 8 circumferential layers, the number of intermediate circumferential layers is (X-12) / Y, and the layering sequence is: 4 circumferential layers, 1 longitudinal cycle, (X-12) / Y circumferential layers, 1 longitudinal cycle, ..., 8 circumferential layers to finish.

6. The method for designing longitudinal winding low-overlap layer ply of yarn parameters for large composite pressure-resistant shell molds according to claim 1, characterized in that, In step S3, for the yarn bending area at the corner of the mold end, the curvature change area at the cross-section, and the area where multiple yarns intersect and overlap, the yarn path is adjusted to make the yarn closely fit the mold surface, eliminating the risk points of local overlap and gaps.

7. The method for designing longitudinal winding low-overlap layer ply of yarn parameters for large composite pressure-resistant shell molds according to claim 1, characterized in that, In step S2, the winding angle adjustment has a higher priority than the friction coefficient adjustment. When adjusting, first make a coarse adjustment in 0.5° increments to lock the downward trend of the number of cutting points, and then make a fine adjustment in 0.1° increments to the target number of cutting points.

8. The method for designing longitudinal winding low-overlap layer ply of yarn parameters for large composite pressure-resistant shell molds according to claim 1, characterized in that, The large composite pressure-resistant shell is a cylindrical deep-sea pressure-bearing shell with an inner diameter ≥800mm, a wall thickness ≥50mm, and a product length ≥6000mm, and is formed by wet winding of T700 or T800 carbon fiber.

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