Designing and forming method and device for deep-sea bionic composite pressure-resistant shell

Abstract

The invention discloses a design forming method and equipment for a deep-sea bionic composite pressure-resistant shell. The design method comprises the steps of biological prototype digitization and reverse modeling, key geometric parameter extraction and quantitative analysis, parameterized bionic model construction and design space determination, and finite element analysis-based iterative optimization and model determination. The forming method comprises the steps of material preparation, layered laying, packaging and vacuum treatment, autoclave curing, demolding and machining and sealing assembly. The forming equipment comprises a central control module, a material preparation module, a mold preparation module, a layering forming module, a curing treatment module and a post-treatment module. According to the method, a complete technical system covering special forming equipment, a closed-loop design method and an intelligent forming process is constructed, and a closed loop is formed under the support of the special equipment through a design process of'biological feature extraction-parametric modeling-multi-objective optimization 'and a manufacturing process of'automatic layering-flexible partition pressure control-intelligent curing'.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of deep-sea equipment design and manufacturing, and in particular to a deep-sea bionic composite pressure hull design and forming method and equipment. BACKGROUND

[0002] The pressure hull is the core pressure-bearing and sealing component of deep-sea exploration equipment, and its performance directly determines the depth, reliability and effective load of the equipment. In the prior art, the pressure hull is mostly in regular geometric configurations such as spherical or cylindrical. The spherical structure has uniform stress distribution and good pressure resistance, but the internal space utilization rate is low; the cylindrical structure has high space utilization rate, but is prone to buckling instability under deep water high pressure, and the reliability is challenged. In addition, traditional metal materials (such as titanium alloy and high-strength steel) have bottlenecks in pursuing lightweight, resisting deep-sea long-term corrosion and fatigue.

[0003] Bionics provides a new way to solve the above problems. The shell of deep-sea snails (such as deep-sea black angle snails) evolved through natural selection exhibits excellent performance in pressure resistance, space utilization and damage tolerance, and its mechanism mainly reflects three aspects:

[0004] 1. Multistage material system: a functional gradient material distribution with "outer wear-resistant, middle pressure-resistant, and inner cushioning";

[0005] 2. Optimal macro-configuration: a "flat circular" structure with a diameter-height ratio greater than 1:1 is adopted to realize the unification of uniform pressure transmission and high space utilization rate;

[0006] 3. Micro-reinforced features: the shell surface features such as spiral ribs and nodules can effectively suppress shell buckling instability and prevent crack propagation.

[0007] However, there are two major challenges in converting the efficient mechanism of the above biological prototype into a product that can be engineered for application:

[0008] First, at the design level, there is a lack of a systematic closed-loop design method from accurate extraction of biological features to parameterized modeling of structures and multi-objective optimization, making it difficult to reliably convert biological advantages into quantifiable and verifiable engineering design schemes.

[0009] Secondly, at the manufacturing level, there is a lack of special equipment and processes that can form such complex bionic geometric structures and functional gradient materials with high quality and repeatability. Traditional composite material forming methods cannot accurately reproduce the micro-features such as spiral ribs and nodules, and cannot realize the integrated co-curing and interface reinforcement of the "outer rigid and inner flexible" gradient material, resulting in the loss of bionic design intent in the manufacturing process, and the product performance is difficult to meet the expectations. SUMMARY

[0010] Purpose of the invention: To address the above-mentioned problems, the purpose of this invention is to provide a design and molding method and equipment for deep-sea biomimetic composite pressure-resistant shells, ensuring that from bio-inspiration to the final product, it can possess excellent pressure resistance, high space utilization, lightweight and high reliability, thereby systematically solving the design and manufacturing challenges of deep-sea pressure-resistant shells.

[0011] Technical solution: A method for designing and molding a pressure-resistant shell made of biomimetic composite materials for deep-sea applications.

[0012] The housing design method includes the following steps:

[0013] Step 1: Digitization and reverse modeling of biological prototypes;

[0014] The selected deep-sea snail shell is modeled in 3D and converted into a B-spline surface to complete the digital reproduction of the geometric shape of the biological prototype, thus obtaining the inverse model;

[0015] Step 2: Extraction and Quantitative Analysis of Key Geometric Parameters;

[0016] The obtained reverse model is imported into engineering software for multi-level geometric feature analysis and quantization to obtain various parameters;

[0017] Step 3: Construction of parametric biomimetic model and determination of design space;

[0018] Based on the extracted parameters, a parameterized initial digital model of the biomimetic pressure-resistant shell is established to clarify the feasible domain and optimization direction of the engineering design.

[0019] Step 4: Iterative optimization and model determination based on finite element analysis;

[0020] The parametric model is imported into the finite element analysis software, and the closed-loop iterative optimization process of analysis-evaluation-adjustment is used until the optimal combination of geometric parameters that satisfies the objective function is obtained, thereby determining the final geometric model of the pressure hull.

[0021] The shell forming method includes the following steps:

[0022] Step 1: Material preparation;

[0023] Prepare the necessary composite and auxiliary materials;

[0024] Step 2: Lay in layers;

[0025] Automated laying of biomimetic functional gradient material structures on preheated molds;

[0026] Step 3: Encapsulation and vacuum treatment;

[0027] After installation, the system needs to be encapsulated in preparation for curing.

[0028] Step 4: The encapsulated body is placed into an autoclave, and the flexible zoned pressure control system is used to dynamically match the curing characteristics of the material to complete the final curing.

[0029] Step 5: After curing, demolding and machining are carried out, and finally sealing assembly is performed to form a pressure-bearing sealed shell.

[0030] Furthermore, in step one, a high-precision 3D scan is first performed on the selected deep-sea snail shell to obtain complete point cloud data of its outer surface; then, the point cloud data is optimized, including removing noise points, filling data gaps, and smoothing; based on the optimized point cloud data, a continuous mesh polygon model is generated through a surface reconstruction algorithm; finally, the mesh model is converted into a non-uniform rational B-spline surface and output in a general CAD format to complete the accurate digital reproduction of the geometric morphology of the biological prototype.

[0031] Furthermore, in step two, the parameters include contour curve fitting and macroscopic parameters. A representative contour line is obtained through the sectioning model, and a parameterized curve equation is fitted to obtain the parameterized curve equation. Based on this, key macroscopic parameters are extracted, including the diameter-to-height ratio, the proportion of helical height, and the shell wall thickness distribution gradient; helical structure parameters, which are obtained by fitting the helical line on the shell surface to quantify the range of helical angle variation and the helical expansion coefficient; and helical rib and nodule characteristic parameters, which are obtained by measuring and recording the spacing, cross-sectional shape and size of the helical ribs, as well as the distribution density, diameter and height of the nodules to analyze their distribution patterns.

[0032] In step three, a parameterized initial digital model of the biomimetic pressure hull is established based on multiple parameters. These parameters are set as design variables, and the minimum internal volume and maximum external dimensions of the pressure hull are used as constraints. The objective function is to maximize the critical buckling pressure or minimize the mass of the hull, thereby clarifying the feasible domain and optimization direction of the engineering design.

[0033] Furthermore, in step four, the established parametric model is imported into the finite element analysis software, and the hydrostatic pressure load corresponding to the target working water depth is applied. The stress distribution is evaluated through static analysis and the critical buckling pressure is calculated through nonlinear buckling analysis. The analysis results are compared with the preset objective function. If the performance is not optimal, the design parameters are automatically or manually adjusted, the model is updated and reanalyzed, forming a closed-loop iterative optimization process of analysis-evaluation-adjustment. This process is repeated until the optimal combination of geometric parameters that satisfies the objective function is obtained, thereby determining the final geometric model of the pressure hull.

[0034] Furthermore, in step 1, the materials include carbon fiber / epoxy resin prepreg for outer and middle layer layup; aramid fiber prepreg for inner layer layup; and nano-doped toughened epoxy resin film for interlayer interface reinforcement. All prepregs must be pre-cut according to the design model to ensure accurate dimensions and shapes.

[0035] Ideally, a seven-axis layup robot system is used on a precision mold preheated to 60±2°C to automatically lay up the biomimetic functional gradient material structure, including the following steps:

[0036] S21: Outer layer, i.e., horn-like layer, uses carbon fiber / epoxy resin prepreg, which is laid by a seven-axis layup robot system along ±45° direction and applies 50-100N pressure to make the material completely fit the biomimetic features of the screw ribs and nodules of the mold cavity, avoiding fiber bridging.

[0037] S22: The middle layer is laid, namely the prism-like layer and the interface layer. It uses unidirectional high-modulus carbon fiber prepreg and is laid in a 0 / 90 / ±45° layup sequence. When the thickness is half, a pre-cut nano-doped carbon nanotube toughening film is automatically added.

[0038] S23: Inner layer, i.e. imitation pearl layer, is made of aramid fiber prepreg and laid under 30-50N pressure.

[0039] Furthermore, step 3 includes the following steps:

[0040] S31: Integrated packaging: Auxiliary materials such as isolation material, adhesive absorbent material, non-porous isolation membrane, flexible partitioned pressure pad and breathable felt are sequentially covered on the layup. The pressure pad is composed of multiple independent and controllable micro airbag units.

[0041] S32: Vacuum bag sealing: The entire assembly is sealed with a vacuum bag and evacuated to above -0.095MPa using a dual-channel vacuum system. Pressure holding and leak detection are performed to remove interlayer gas and provide initial compaction pressure, allowing the prepreg to initially adhere to the mold.

[0042] Ideally, in step 4, the flexible zoned pressure control system includes an array of independent airbag units integrating microsensors, capable of applying differentiated pressure to different areas of the mold based on real-time feedback of resin viscosity and dielectric signals. The curing process includes three stages:

[0043] Phase 1: Preheating rheological period, the temperature rises from room temperature to 90°C;

[0044] Apply a pressure of 0.8-1.0 MPa to the complex regions to drive the resin to fill fully; maintain a standard pressure of 0.5 MPa in the flat regions; and use a pressure of 0.4 MPa in the interlayer transition regions to prevent interlayer slippage.

[0045] Phase 2: Layered gelation period, temperature increases from 90°C to 130°C;

[0046] When the resin of the middle main load-bearing layer is detected to be close to the gel point, the pressure in the corresponding area is rapidly increased to 1.0 MPa for compaction; at the same time, the pressure in the inner aramid region is reduced to 0.4 MPa to protect its tough structure.

[0047] Phase 3: Synergistic curing period, during which the temperature is raised from 130°C to 180°C, and the temperature and pressure are maintained.

[0048] The pressure in all areas is uniformly set to 0.7 MPa, so that each layer of material can complete the final co-curing under the coordination of the interface layer, and the heating rate is finely adjusted according to the heat release of the inner layer curing.

[0049] Most importantly, in step 5, after the curing process is completed, the temperature is controlled to drop below 60°C. A hydraulic ejection system is used in conjunction with high-pressure air gap injection technology to achieve non-destructive demolding. Subsequently, the shell flange and key assembly parts are precision machined on a five-axis CNC machining center to ensure that the flatness is ≤0.1mm and the surface roughness Ra≤3.2μm to meet the high standard of connection and sealing requirements.

[0050] The two halves of the shell, after being processed, are joined together using titanium alloy flanges, high-strength alloy bolts, and fluororubber O-rings. A torque gradient tightening process is used to ensure that the bolt preload is evenly distributed, ultimately forming a complete sealed shell.

[0051] A molding equipment for manufacturing a pressure-resistant shell using the above-mentioned deep-sea biomimetic composite material pressure-resistant shell design and molding method includes a central control module, a material preparation module, a mold preparation module, a layup molding module, a curing treatment module, and a post-processing module.

[0052] The central control module is responsible for monitoring, coordinating and optimizing the entire production process. The digital model and process parameters generated in the design phase send instructions to downstream modules and collect sensor data from each link in real time to realize the visualization, traceability and adaptive control of the production process.

[0053] The material preparation module includes a prepreg material storage bin, an automatic cutting system, and an AGV material conveying system; the prepreg is cut into specific shapes and sizes according to the designed layup scheme and then delivered to the layup forming module by the AGV material conveying system.

[0054] The mold preparation module is responsible for the preparation, inspection, and preheating of the forming mold. The mold preparation module includes a CNC machining center, a coordinate measuring machine, and a mold preheating station. The CNC machining center precisely processes the mold cavity with biomimetic features according to the final shell geometry model. The coordinate measuring machine performs quality inspection on the mold and feeds the results back to the central control module. After the qualified mold is preheated to the set temperature by the mold preheating station, it is transported to the layup station by the AGV material conveying system.

[0055] The layup module completes the biomimetic gradient material layup. The layup module includes a mold positioning platform, an online detection system, and a gantry layup robot. After the mold is preheated, it is transferred to the mold positioning platform. Under the guidance of the laser projection positioning system, the gantry layup robot lays the prepreg on the mold surface. The online detection system monitors the layup thickness and quality in real time.

[0056] The curing module combines an autoclave system with a flexible zoned pressure control system to achieve high-quality curing of the composite material. The curing module includes an automatic packaging station, an autoclave system, and a programmed cooling station. After the mold completes the layup, it first undergoes vacuum packaging at the automatic packaging station, and then the autoclave system performs fine hot-press curing. The combination of the autoclave system and the flexible zoned pressure control system dynamically adjusts the temperature and pressure of different areas according to the resin rheological properties and structural stress distribution to achieve gradient curing. After curing, the shell is cooled by the programmed cooling station.

[0057] The post-processing module is responsible for the demolding, finishing, and inspection of the shell. The post-processing module includes an automatic demolding machine, a CNC precision machining center, and a quality inspection station. After the cured shell is demolded without damage by the automatic demolding machine, the CNC precision machining center performs precision machining on the flange mating surfaces to ensure assembly accuracy and sealing. The quality inspection station conducts comprehensive performance testing on the finished product. After passing the test, the finished product is transported to the finished product warehouse by the AGV material conveying system, completing the entire manufacturing process.

[0058] This invention constructs a complete technical system encompassing specialized molding equipment, closed-loop design methods, and intelligent molding processes. Through a design process of "biological feature extraction - parametric modeling - multi-objective optimization" and a manufacturing process of "automated layup - flexible zoned pressure control - intelligent curing," a closed loop is formed with the support of specialized equipment.

[0059] Beneficial effects: Compared with the prior art, the advantages of the present invention are:

[0060] 1. System Advantages: This invention forms a complete technological closed loop from biomimetic principles to high-quality products; it organically integrates specialized molding equipment, digital design methods, and intelligent molding processes to construct a full-link system of "bio-features—parametric models—optimized design—automatic molding." This closed loop fundamentally solves the industry problems of biomimetic designs being difficult to manufacture and inconsistent product performance, ensuring that high-performance design intentions can be accurately and reliably transformed into physical products.

[0061] 2. Equipment Advantages: The molding equipment of this invention enables high-precision, repeatable, and automated manufacturing of complex biomimetic structures. The specialized molding equipment integrates a seven-axis lay-up robot, a flexible zoned pressure control system, and multi-sensor collaborative control capabilities, enabling precise reproduction of microscopic features such as ribs and nodules, and one-time co-curing of "externally rigid and internally tough" gradient materials. The automation and intelligence of the equipment significantly improve manufacturing efficiency, molding quality, and batch consistency, making it suitable for engineering-scale mass production.

[0062] 3. Advantages of the Design Method: Based on bio-feature-based parametric optimization, the performance of the pressure-resistant shell structure is significantly improved. This invention's design method establishes a parametric biomimetic model through reverse modeling of deep-sea snail shells and extraction of key geometric parameters. The optimal configuration and feature layout are then determined through finite element iterative optimization. Examples show that this design process can increase the critical buckling pressure of the shell by 40–45%, achieving a better balance between pressure resistance and lightweight design within the same volume.

[0063] 4. Molding Process Advantages: Flexible zoned pressure control matches the material's curing characteristics, achieving high-quality interface and structural molding; the molding method employs a three-stage intelligent curing process, applying differentiated pressure to different areas of the mold through independently controllable airbag units, ensuring that the resin fully fills characteristic corners, achieves dense interlayers, and enhances the interface. This process effectively avoids defects such as fiber bridging and interlayer slippage, resulting in a complete molded shell structure and a smooth performance gradient transition.

[0064] 5. Comprehensive performance advantages: Balancing pressure resistance, impact resistance, space utilization, and reliability; the final product inherits and enhances the multiple advantages of the biological prototype: the flattened spherical configuration improves space utilization; the spiral ribs and gradient materials synergistically enhance pressure resistance and buckling resistance; the nodules and tough inner layer enhance impact resistance and crack arrest performance; the overall co-curing and nano-interface ensure long-term reliability and fatigue life, fully meeting the needs of deep-sea equipment for lightweight, high reliability, and multi-functional integration. Attached Figure Description

[0065] Figure 1 Schematic diagram of a deep-sea biomimetic composite material pressure-resistant shell molding equipment system;

[0066] Figure 2 Flowchart of design methodology for deep-sea biomimetic composite pressure-resistant shells;

[0067] Figure 3 Flowchart of methods for digitizing and reverse-modeling biological prototypes;

[0068] Figure 4 This is a flowchart of the iterative optimization and model determination method based on finite element analysis.

[0069] Figure 5 Here is a 3D scan structure of a deep-sea snail shell in one embodiment;

[0070] Figure 6 This is a design implementation diagram of a deep-sea biomimetic pressure-resistant hull in one embodiment;

[0071] Figure 7 Flowchart of the molding method for a deep-sea biomimetic composite pressure-resistant shell;

[0072] Figure 8 Schematic diagram of the pressure-resistant shell material laying process;

[0073] Figure 9 This is a schematic diagram of the autoclave device.

[0074] Figure 10 This is a schematic diagram of the hot pressing molding logic. Detailed Implementation

[0075] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0076] like Figure 1 As shown, the present invention provides a deep-sea biomimetic composite material pressure-resistant shell molding equipment, including a central control module 100, a material preparation module 200, a mold preparation module 300, a layup molding module 400, a curing treatment module 500, and a post-processing module 600. Each module works collaboratively under the unified scheduling of the central control module 100, and the automatic flow of materials and semi-finished products between each workstation is realized through an AGV material conveying system, forming a continuous and closed-loop intelligent production line.

[0077] The central control module 100 is responsible for monitoring, coordinating and optimizing the entire production process. It receives digital models and process parameters generated during the design phase, issues instructions to downstream modules, and collects sensor data from each stage in real time to achieve visualization, traceability and adaptive control of the production process.

[0078] The material preparation module 200 includes a prepreg material storage 210, an automatic cutting system 220, and an AGV material conveying system 230. The prepreg is cut into specific shapes and sizes according to the designed layup scheme and delivered to the layup forming module by the AGV material conveying system 230, ensuring efficient and accurate material supply.

[0079] The mold preparation module 300 is responsible for the preparation, inspection and preheating of the forming mold. The CNC machining center 310 precisely processes the mold cavity containing biomimetic features (such as screw ribs and nodules) according to the final shell geometry model. The coordinate measuring machine 320 performs quality inspection on the mold and feeds the results back to the central control module 100. After the qualified mold is preheated to the set temperature by the mold preheating station 330, it is transported to the layup station by the AGV system 230.

[0080] The layup module 400 is a key step in completing the biomimetic gradient material layup. After the mold is preheated, it is transferred to the mold positioning platform 410. Under the guidance of the laser projection positioning system, the gantry layup robot 430 automatically and accurately lays the prepreg on the mold surface according to the three-layer functional gradient layup scheme of "external rigidity and internal toughness", especially ensuring the complete fit of the biomimetic feature areas. The online detection system 420 monitors the layup thickness and quality in real time to ensure that the tolerance is controlled within the allowable range.

[0081] The curing module 500 uses a combination of an autoclave system and a flexible zoned pressure control system to achieve high-quality curing of the composite material. After the mold completes the layup, it first undergoes vacuum sealing in the automatic encapsulation station 510, and then the autoclave system 520 performs fine hot-press curing. The combination of the autoclave system and the flexible zoned pressure control system can dynamically adjust the temperature and pressure of different areas according to the resin rheological properties and structural stress distribution to ensure clear biomimetic features, enhanced interlayer interfaces, and gradient co-curing of the three layers. After curing, the shell is cooled by the programmed cooling station 530.

[0082] The post-processing module 600 is responsible for the demolding, finishing and final inspection of the shell; after the shell is cured, it is demolded without damage by the automatic demolding machine 610, and then the CNC precision machining center 620 performs precision machining on the flange mating surface to ensure assembly accuracy and sealing; the quality inspection station 630 performs comprehensive performance testing on the finished product, and after passing the test, it is transported to the finished product warehouse by the AGV system 230 to complete the entire manufacturing process.

[0083] Through modular design and intelligent control, this equipment deeply integrates biomimetic design, material preparation, molding process and quality assurance, realizing the efficient, high-quality and repeatable manufacturing of deep-sea biomimetic composite pressure shells, providing reliable equipment support for the lightweight and high-performance of deep-sea equipment.

[0084] like Figure 2 As shown, this invention provides a design method for deep-sea pressure-resistant composite material shells, which is a closed-loop, iterative digital design process from biological prototypes to engineering products. The method includes four core steps: digitalization and reverse modeling of biological prototypes, extraction and quantitative analysis of key geometric parameters, construction of parametric biomimetic models and determination of design space, and iterative optimization and model determination based on finite element analysis. It systematically transforms the excellent pressure resistance mechanism of deep-sea snail shells into quantifiable, optimizable, and manufacturable engineering solutions.

[0085] Step 1: Digitization and reverse modeling of biological prototypes;

[0086] like Figure 3As shown, this step aims to achieve accurate 3D digitization of the biological prototype. First, a high-precision 3D scan is performed on the selected deep-sea snail shell (such as the deep-sea black horn snail) to obtain complete point cloud data of its outer surface. Then, the point cloud data is optimized, including removing noise points, filling data gaps, and smoothing. Based on the optimized point cloud, a continuous mesh polygon model is generated using a surface reconstruction algorithm. Finally, the mesh model is converted into a non-uniform rational B-spline surface and output in a general CAD format, completing the accurate digital reproduction of the biological prototype's geometry and laying the foundation for subsequent parameter extraction.

[0087] Step 2: Extraction and Quantitative Analysis of Key Geometric Parameters;

[0088] The reverse model obtained in step one is imported into engineering software for multi-level geometric feature analysis and quantization to obtain multiple parameters; this mainly includes:

[0089] Contour curve fitting and macroscopic parameter definition: Representative contour lines are obtained by cutting the model, and parametric curve equations are obtained by fitting. Based on this, key macroscopic parameters such as diameter-to-height ratio, helical height ratio, and shell wall thickness distribution gradient are extracted.

[0090] Helical structure parameterization: By fitting the helix on the surface of the shell, the range of helix angle variation, the helix expansion coefficient, and other characteristics are quantified.

[0091] Spiral rib and nodule feature extraction: The spacing, cross-sectional shape, and size of the spiral ribs, as well as the distribution density, diameter, and height of the nodules, were measured and recorded to analyze their distribution patterns. This quantitative data serves as a bridge connecting biological characteristics and engineering design.

[0092] Step 3: Construction of parametric biomimetic model and determination of design space;

[0093] Based on the key geometric parameters extracted in step two, a parameterized initial digital model of the biomimetic pressure hull is established. These parameters are set as design variables, with the minimum internal volume and maximum external dimensions of the pressure hull serving as constraints. The objective function is set as maximizing the critical buckling pressure or minimizing the mass of the hull, thereby clarifying the feasible domain and optimization direction of the engineering design.

[0094] Step 4: Iterative optimization and model determination based on finite element analysis;

[0095] like Figure 4As shown, this step is the core iterative process that drives the design towards optimal performance. The parametric model established in step three is imported into the finite element analysis software, and a hydrostatic pressure load corresponding to the target working water depth is applied. Static analysis (evaluating stress distribution) and nonlinear buckling analysis (calculating critical buckling pressure) are then performed sequentially. The analysis results are compared with the preset objective function. If the performance is not optimal, the design parameters are automatically or manually adjusted, the model is updated, and the analysis is repeated, forming a closed-loop iterative optimization process of "analysis-evaluation-adjustment." This process is repeated until the optimal combination of geometric parameters that satisfies the objective function is obtained, thereby determining the final geometric model of the pressure hull.

[0096] To illustrate the engineering implementation process and technical effects of this design method, a specific embodiment is given below in conjunction with the accompanying drawings.

[0097] like Figure 5 As shown, in a specific embodiment of the present invention, a typical deep-sea snail shell is first subjected to high-precision 3D scanning to obtain complete and accurate point cloud data of its surface, thus achieving accurate digital reproduction of the geometric morphology of the biological prototype. Based on this digital model, the key geometric features of the snail shell prototype are extracted, and its quantitative data and corresponding biomimetic design inspirations are shown in Table 1:

[0098]

[0099] like Figure 6 As shown, based on the quantitative analysis results of the above-mentioned biological characteristics in step two, the design enters the engineering implementation stage. Step three involves selecting key biomimetic characteristic parameters and adaptively adjusting and assigning values, followed by systematic finite element iterative optimization in step four, ultimately completing the optimized modeling of the pressure hull shell.

[0100] In this embodiment, the specific design variables, constraints, objective function, and optimization results are determined as follows:

[0101] 1. Design features and basic parameter settings;

[0102] Based on the characteristics of the biological prototype, the following engineering adjustments and values ​​were made:

[0103] (1) Diameter-to-height ratio: adjusted to 1.2. After step four iterative optimization, this value achieves the best balance between pressure resistance and internal space utilization.

[0104] (2) Helical portion ratio: set to <20%. This design inherits and strengthens the characteristics of the biological prototype’s “extremely short helical portion”, and as verified in step four, it can effectively avoid stress concentration at the top of the shell.

[0105] (3) Shell wall thickness distribution: The non-uniform wall thickness of the organism is simplified to the engineering reference thickness t0, and the functional gradient of "external rigidity and internal toughness" is achieved through subsequent layer design.

[0106] (4) Number of screw ribs: set to 10 to optimize structural performance and manufacturing cost.

[0107] (5) Distribution and morphology of screw ribs: A ring-shaped screw rib layout with variable spacing is adopted. Through the stress cloud diagram analysis in step four, the optimal arrangement method with relatively dense screw ribs in high stress areas and relatively sparse screw ribs in low stress areas is determined.

[0108] (6) Rib cross-section shape: A trapezoidal cross-section is adopted. Under the premise of meeting the demolding process requirements, the specific dimensional parameters are optimized through step four.

[0109] (7) Nodule features: As an optional feature, it can be decided whether to introduce it based on the specific impact resistance and crack arrest requirements of deep-sea equipment.

[0110] 2. Constraints;

[0111] (1) Internal effective volume: ≥ 0.25 m³.

[0112] (2) Maximum external dimensions: Diameter D ≤ 700 mm, height H ≤ 600 mm.

[0113] (3) Shell wall thickness: The shell adopts a three-layer composite material structure with a total thickness t = 28 mm (outer layer 5 mm, middle layer 16 mm, inner layer 5 mm, and interlayer adhesive film thickness 1 mm).

[0114] (4) Manufacturing process constraints: All geometric features must meet the demolding requirements of the compression molding process.

[0115] 3. Objective function and optimization results;

[0116] This embodiment takes minimizing the weight of the pressure shell structure while satisfying all the above constraints as its primary objective.

[0117] Following the finite element analysis and multiple rounds of iterative optimization in step four, the final model, while maintaining lightweight construction, achieved a critical buckling pressure that was approximately 40-45% higher than the baseline model without bolts, significantly enhancing structural stability. The optimization analysis further clarified the functional division of the bolts: U1 and U5 bolts provide basic constraints, U2 bolts bear the main supporting role, U3 bolts provide the strongest support in the core high-stress zone, and U4 bolts provide moderate reinforcement to the transition area. This optimized layout was scientifically determined through the systematic stress and buckling analysis in step four.

[0118] 4. The core curve equation of the parametric model;

[0119] Based on the aforementioned design variables and constraints, a parametric biomimetic profile curve was established. Rotating this curve around the shell height direction (Y-axis) generates the shell surface. The resulting profile has an enlarged spiral layer and a naturally contracting end. Its diameter-to-height ratio and spiral portion proportion are both engineering-optimal solutions determined through iterative optimization. The shell surface parametric equations are as follows:

[0120] ;

[0121] ;

[0122] Parameter range: t ∈ [0, π]

[0123] In summary, Figure 6 As shown in the figure, the embodiment fully demonstrates how to use the design method described in this invention to extract key parameters from a biological prototype, and systematically complete the optimized design of a high-performance biomimetic pressure-resistant shell through the close combination of parametric modeling and finite element iterative optimization, which fully verifies the scientific nature, practicality and engineering value of the design method of this invention.

[0124] like Figure 7 As shown, the present invention discloses a method for molding a deep-sea biomimetic composite pressure-resistant shell. This molding method is compatible with the above-mentioned molding equipment and design method. The method adopts a general process route of single-sided female mold combined with autoclave curing, and integrates flexible partition pressure control and automated layup technology. Specifically, it includes six major steps: material preparation, layer layup, encapsulation and vacuum treatment, autoclave curing, demolding and machining, and sealing assembly. It aims to achieve integrated, high-quality, and repeatable manufacturing of complex biomimetic geometric features and "externally rigid and internally tough" functional gradient material structures.

[0125] Step 1: Material preparation;

[0126] This step primarily prepares the composite materials and auxiliary materials needed for subsequent laying and curing. The core materials include carbon fiber / epoxy resin prepreg (for the outer and middle layers), aramid fiber prepreg (for the inner layer), and nano-doped toughened epoxy resin film (for interlayer interface reinforcement). All prepregs must be pre-cut according to the design model to ensure precise dimensions and shape.

[0127] Step 2: Lay in layers;

[0128] In this step, a seven-axis layup robot system is used to automatically and precisely lay up the biomimetic functional gradient material structure on a precision mold preheated to 60±2°C.

[0129] S21: Outer layer laying (simulated horn layer): Carbon fiber / epoxy resin prepreg is used. It is laid by a robot along the ±45° direction and 50-100N pressure is applied to ensure that the material completely fits the biomimetic features such as the screw ribs and nodules of the mold cavity and avoids fiber bridging.

[0130] S22: Intermediate layer layup (simulated prism layer) and interface layer placement: Unidirectional high-modulus carbon fiber prepreg is used, laid up in a 0 / 90 / ±45° layup sequence. When half the thickness is laid up, a pre-cut nano-doped carbon nanotube toughening film is automatically added to enhance interlayer performance through the "nano-bridging" effect.

[0131] S23: Inner Layer Laying (Imitation Pearl Layer): Utilizing aramid fiber prepreg, laid under low pressure (30-50N) to protect fiber toughness. The entire process is monitored by an online laser thickness gauge to ensure thickness tolerance is within ±0.1mm.

[0132] Step 3: Encapsulation and vacuum treatment;

[0133] like Figure 8 As shown, after the installation is completed, the system needs to be encapsulated in preparation for curing.

[0134] S31: Integrated Packaging: A layer of insulating material, adhesive-absorbing material, non-porous insulating membrane, flexible zoned pressure pad, and breathable felt are sequentially applied onto the laminate. This pressure pad, composed of numerous independently controllable micro-airbag units, is key to achieving precise localized pressure control.

[0135] S32: Vacuum Bag Sealing: The entire assembly is sealed using a vacuum bag, and a dual-channel vacuum system is used to evacuate the pressure to above -0.095 MPa, followed by pressure holding and leak detection. This process removes interlayer gas and provides initial compaction pressure, allowing the prepreg to initially adhere to the mold.

[0136] Step 4: Autoclave curing – Intelligent molding based on a flexible zoned pressure control system;

[0137] The encapsulated body is then placed in an autoclave for final curing. For example... Figure 9 As shown, the autoclave provides global compressed gas pressure and thermal field. (As...) Figure 10 As shown, the core of the curing process lies in the dynamic matching between the flexible partitioned pressure control system and the curing characteristics of the material.

[0138] The system consists of an array of independent airbag units integrating micro-sensors, enabling it to apply differentiated pressure to different areas of the mold (such as screw ribs, flat areas, and interlayer transition zones) based on real-time feedback from resin viscosity, dielectric signals, etc. The curing process is intelligently executed in three stages:

[0139] (1) Preheating rheological period (room temperature → 90°C): Apply higher pressure (0.8-1.0 MPa) to complex areas such as spiral ribs to drive the resin to fill fully; maintain standard pressure (0.5 MPa) in flat areas; and use lower pressure (0.4 MPa) in interlayer transition areas to prevent interlayer slippage.

[0140] (2) Layered gelation period (90°C→130°C): When the resin of the middle main load-bearing layer is detected to be close to the gel point, the pressure of the corresponding area is rapidly increased to 1.0MPa for compaction; at the same time, the pressure of the inner aramid region is reduced to 0.4MPa to protect its tough structure.

[0141] (3) Co-curing period (130°C→180°C, heat preservation and pressure preservation): The pressure in all areas is unified to 0.7MPa, so that the three-layer material can complete the final co-curing under the coordination of the interface layer, and the heating rate is finely adjusted according to the heat release of the inner layer curing.

[0142] This intelligent curing strategy ensures clear shaping of biomimetic features, full resin impregnation, and strong interlayer interfaces, achieving integration of structure and materials.

[0143] Step 5: Demolding and machining;

[0144] After the curing process is completed, the temperature is controlled to drop below 60°C, and a hydraulic ejection system combined with high-pressure air gap injection technology is used to achieve non-destructive demolding. Subsequently, key assembly parts such as the shell flange mating surface are precision machined on a five-axis CNC machining center to ensure flatness ≤0.1mm and surface roughness Ra≤3.2μm, in order to meet high-standard connection and sealing requirements.

[0145] Step 6: Sealing assembly;

[0146] The two machined shell halves are then assembled using titanium alloy flanges, high-strength alloy bolts, and fluororubber O-rings. A torque gradient tightening process is employed to ensure uniform distribution of bolt preload, ultimately forming a complete, reliable, pressure-bearing sealed shell.

[0147] In summary, this molding method integrates precision mold technology, automated layup, and a flexible, zoned pressure-controlled intelligent curing process, forming a rigorous, closed-loop manufacturing process. It ensures that the design intent, from macroscopic contours and microscopic biomimetic features to microscopic material gradients, can be transformed into a high-quality, highly consistent physical product. This results in a deep-sea biomimetic pressure-resistant shell that possesses excellent pressure resistance, high toughness, lightweight design, and high reliability.

[0148] This invention is organically composed of the following three core technology systems:

[0149] Deep-sea biomimetic composite material pressure-resistant shell molding equipment: It is a highly integrated, automated and intelligent special manufacturing system that covers functional modules such as material preparation, mold processing, layup molding, curing control and post-processing, supporting closed-loop production with full control and traceability.

[0150] Design method for deep-sea biomimetic composite pressure hull: It provides a complete design process from biological prototype digitization, feature parameter extraction, parametric modeling to finite element iterative optimization, and achieves synergistic optimization of structural performance and space utilization;

[0151] A method for molding pressure-resistant shells of deep-sea biomimetic composite materials: Based on flexible zoned pressure control and multi-stage intelligent curing process, a high-quality integrated molding of biomimetic geometric features and functionally graded materials is achieved, ensuring structural integrity and interface toughness.

Claims

1. A method for designing and molding a pressure-resistant shell made of biomimetic composite material for deep-sea applications, characterized in that, The housing design method includes the following steps: Step 1: Digitization and reverse modeling of biological prototypes; The selected deep-sea snail shell is modeled in 3D and converted into a B-spline surface to complete the digital reproduction of the geometric shape of the biological prototype, thus obtaining the inverse model; Step 2: Extraction and Quantitative Analysis of Key Geometric Parameters; The obtained reverse model is imported into engineering software for multi-level geometric feature analysis and quantization to obtain various parameters; Step 3: Construction of parametric biomimetic model and determination of design space; Based on the extracted parameters, a parameterized initial digital model of the biomimetic pressure-resistant shell is established to clarify the feasible domain and optimization direction of the engineering design. Step 4: Iterative optimization and model determination based on finite element analysis; The parametric model is imported into the finite element analysis software, and the closed-loop iterative optimization process of analysis-evaluation-adjustment is used until the optimal combination of geometric parameters that satisfies the objective function is obtained, thereby determining the final geometric model of the pressure hull. The shell forming method includes the following steps: Step 1: Material preparation; Prepare the necessary composite and auxiliary materials; Step 2: Lay in layers; Automated laying of biomimetic functional gradient material structures on preheated molds; Step 3: Encapsulation and vacuum treatment; After installation, the system needs to be encapsulated in preparation for curing. Step 4: The encapsulated body is placed into an autoclave, and the flexible zoned pressure control system is used to dynamically match the curing characteristics of the material to complete the final curing. Step 5: After curing, demolding and machining are carried out, and finally sealing assembly is performed to form a pressure-bearing sealed shell.

2. The method for designing and molding a deep-sea biomimetic composite pressure-resistant shell according to claim 1, characterized in that, In step one, a high-precision three-dimensional scan is first performed on the selected deep-sea snail shell to obtain complete point cloud data of its outer surface; Subsequently, the point cloud data is optimized, including removing noise points, filling data gaps, and smoothing. Based on the optimized point cloud data, a continuous mesh polygon model is generated using a surface reconstruction algorithm. Finally, the mesh model is converted into a non-uniform rational B-spline surface and output in a general CAD format, completing the accurate digital reproduction of the geometric shape of the biological prototype.

3. The method for designing and molding a deep-sea biomimetic composite pressure-resistant shell according to claim 1, characterized in that: In step two, the parameters include contour curve fitting and macroscopic parameters. A representative contour line is obtained through the sectioning model, and a parameterized curve equation is fitted to extract key macroscopic parameters, including the diameter-to-height ratio, the proportion of helix height, and the shell wall thickness distribution gradient; helical structure parameters, which are obtained by fitting the helix on the shell surface to quantify the range of helix angle variation and the helix expansion coefficient; and helical rib and nodule characteristic parameters, which are obtained by measuring and recording the spacing, cross-sectional shape and size of the helical ribs, as well as the distribution density, diameter and height of the nodules to analyze their distribution patterns. In step three, a parameterized initial digital model of the biomimetic pressure hull is established based on multiple parameters. These parameters are set as design variables, and the minimum internal volume and maximum external dimensions of the pressure hull are used as constraints. The objective function is to maximize the critical buckling pressure or minimize the mass of the hull, thereby clarifying the feasible domain and optimization direction of the engineering design.

4. The method for designing and molding a deep-sea biomimetic composite pressure-resistant shell according to claim 1, characterized in that: In step four, the established parametric model is imported into the finite element analysis software, and the hydrostatic pressure load corresponding to the target working water depth is applied. The stress distribution is evaluated through static analysis and the critical buckling pressure is calculated through nonlinear buckling analysis. The analysis results are compared with the preset objective function. If the performance is not optimal, the design parameters are automatically or manually adjusted, the model is updated and reanalyzed, forming a closed-loop iterative optimization process of analysis-evaluation-adjustment. This process is repeated until the optimal combination of geometric parameters that satisfies the objective function is obtained, thereby determining the final geometric model of the pressure hull.

5. The method for designing and molding a deep-sea biomimetic composite pressure-resistant shell according to claim 1, characterized in that: In step 1, the materials include carbon fiber / epoxy resin prepreg for outer and middle layer layup; aramid fiber prepreg for inner layer layup; and nano-doped toughened epoxy resin film for interlayer interface reinforcement. All prepregs must be pre-cut according to the design model to ensure accurate dimensions and shapes.

6. The method for designing and molding a deep-sea biomimetic composite pressure-resistant shell according to claim 5, characterized in that: On a precision mold preheated to 60±2°C, a seven-axis layup robot system is used to automatically lay up a biomimetic functional gradient material structure, including the following steps: S21: Outer layer, i.e., horn-like layer, uses carbon fiber / epoxy resin prepreg, which is laid by a seven-axis layup robot system along ±45° direction and applies 50-100N pressure to make the material completely fit the biomimetic features of the screw ribs and nodules of the mold cavity, avoiding fiber bridging. S22: The middle layer is laid, namely the prism-like layer and the interface layer. It uses unidirectional high-modulus carbon fiber prepreg and is laid in a 0 / 90 / ±45° layup sequence. When the thickness is half, a pre-cut nano-doped carbon nanotube toughening film is automatically added. S23: Inner layer, i.e. imitation pearl layer, is made of aramid fiber prepreg and laid under 30-50N pressure.

7. The method for designing and molding a deep-sea biomimetic composite pressure-resistant shell according to claim 1, characterized in that, Step 3 includes the following steps: S31: Integrated packaging: Auxiliary materials such as isolation material, adhesive absorbent material, non-porous isolation membrane, flexible partitioned pressure pad and breathable felt are sequentially covered on the layup. The pressure pad is composed of multiple independent and controllable micro airbag units. S32: Vacuum bag sealing: The entire assembly is sealed with a vacuum bag and evacuated to above -0.095MPa using a dual-channel vacuum system. Pressure holding and leak detection are performed to remove interlayer gas and provide initial compaction pressure, allowing the prepreg to initially adhere to the mold.

8. The method for designing and molding a deep-sea biomimetic composite pressure-resistant shell according to claim 1, characterized in that, In step 4, the flexible zoned pressure control system includes an array of independent airbag units integrating micro-sensors, capable of applying differentiated pressure to different areas of the mold based on real-time feedback of resin viscosity and dielectric signals. The curing process includes three stages: Phase 1: Preheating rheological period, the temperature rises from room temperature to 90°C; Apply a pressure of 0.8-1.0 MPa to the complex regions to drive the resin to fill fully; maintain a standard pressure of 0.5 MPa in the flat regions; and use a pressure of 0.4 MPa in the interlayer transition regions to prevent interlayer slippage. Phase 2: Layered gelation period, temperature increases from 90°C to 130°C; When the resin of the middle main load-bearing layer is detected to be close to the gel point, the pressure in the corresponding area is rapidly increased to 1.0 MPa for compaction; at the same time, the pressure in the inner aramid region is reduced to 0.4 MPa to protect its tough structure. Phase 3: Synergistic curing period, during which the temperature is raised from 130°C to 180°C, and the temperature and pressure are maintained. The pressure in all areas is uniformly set to 0.7 MPa, so that each layer of material can complete the final co-curing under the coordination of the interface layer, and the heating rate is finely adjusted according to the heat release of the inner layer curing.

9. The method for designing and molding a deep-sea biomimetic composite pressure-resistant shell according to claim 1, characterized in that: In step 5, after the curing process is completed, the temperature is controlled to drop below 60°C. A hydraulic ejection system combined with high-pressure air gap injection technology is used to achieve non-destructive demolding. Subsequently, the shell flange and key assembly parts are precision machined on a five-axis CNC machining center to ensure flatness ≤0.1mm and surface roughness Ra≤3.2μm to meet high standard connection and sealing requirements. The two halves of the shell, after being processed, are joined together using titanium alloy flanges, high-strength alloy bolts, and fluororubber O-rings. A torque gradient tightening process is used to ensure that the bolt preload is evenly distributed, ultimately forming a complete sealed shell.

10. A molding apparatus for manufacturing a pressure-resistant shell using the deep-sea biomimetic composite material pressure-resistant shell design and molding method as described in any one of claims 1 to 9, characterized in that: It includes a central control module (100), a material preparation module (200), a mold preparation module (300), a layup module (400), a curing module (500), and a post-processing module (600). The central control module (100) is responsible for monitoring, coordinating and optimizing the entire production process. The digital model and process parameters generated in the design phase are used to issue instructions to downstream modules and collect sensor data from each link in real time to realize the visualization, traceability and adaptive control of the production process. The material preparation module (200) includes a prepreg material storage tank (210), an automatic cutting system (220), and an AGV material conveying system (230); the prepreg is cut into specific shapes and sizes according to the designed layup scheme and is delivered to the layup forming module by the AGV material conveying system (230); The mold preparation module (300) is responsible for the preparation, inspection and preheating of the molding mold. The mold preparation module (300) includes a CNC machining center (310), a coordinate measuring machine (320) and a mold preheating station (330). The CNC machining center (310) precisely processes the mold cavity containing biomimetic features according to the final shell geometry model. The coordinate measuring machine (320) performs quality inspection on the mold and feeds the results back to the central control module (100). After the qualified mold is preheated to the set temperature by the mold preheating station (330), it is transported to the layup station by the AGV material conveying system (230). The layup module (400) completes the biomimetic gradient material layup. The layup module (400) includes a mold positioning platform (410), an online detection system (420), and a gantry layup robot (430). After the mold is preheated, it is transferred to the mold positioning platform (410). Under the guidance of the laser projection positioning system, the gantry layup robot (430) lays the prepreg on the mold surface. The online detection system (420) monitors the layup thickness and quality in real time. The curing module (500) adopts a combination of a hot autoclave system and a flexible zoned pressure control system to achieve high-quality curing of composite materials. The curing module (500) includes an automatic packaging station (510), a hot autoclave system (520), and a programmed cooling station (530). After the mold completes the layup, it first undergoes vacuum packaging in the automatic packaging station (510), and then the hot autoclave system (520) performs fine hot-press curing. The hot autoclave system (520) is combined with the flexible zoned pressure control system to dynamically adjust the temperature and pressure of different areas according to the resin rheological characteristics and structural stress distribution to achieve gradient curing. After curing, the shell is cooled by the programmed cooling station (530). The post-processing module (600) is responsible for the demolding, finishing and inspection of the shell. The post-processing module (600) includes an automatic demolding machine (610), a CNC precision machining center (620) and a quality inspection station (630). After the solidified shell is demolded without damage by the automatic demolding machine (610), the CNC precision machining center (620) performs precision machining on the flange mating surface and other parts to ensure assembly accuracy and sealing. The quality inspection station (630) performs comprehensive performance testing on the finished product. After passing the test, the finished product is transported to the finished product warehouse by the AGV material conveying system (230) to complete the entire manufacturing process.

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