Variable Thickness High Pressure Resistant Composite Metal Shell for Deep-Sea Equipment and Its Preparation Method

Abstract

This application provides a variable-thickness, high-pressure-resistant composite-metal shell for deep-sea equipment and its preparation method, belonging to the field of pressure-resistant structure design and manufacturing technology for deep-sea equipment. The method includes the following steps: determining the overall structure of the pressure-resistant shell; designing the variable thickness and layup of the composite shell; performing finite element verification and structural optimization; flange design and pretreatment; integral winding molding; integral curing molding; and demolding. Through the variable-thickness partitioning and continuous gradual transition design of the composite main load-bearing shell, and adopting a symmetrical layup-winding scheme with circumferential load bearing as the main characteristic, the load-bearing path distribution under external pressure loads is improved, reducing stress concentration and local instability risks in the transition and end areas, and improving overall external pressure resistance stability. By configuring axial and ±45° layups at the ends and transition areas, the end load can be gradually transitioned and smoothly introduced into the composite main load-bearing structure, improving the uniformity of force transmission at the ends and enhancing structural reliability.

Description

Technical Field

[0001] This application belongs to the field of pressure-resistant structure design and manufacturing technology for deep-sea equipment, specifically relating to a composite-metal shell with variable thickness for high pressure resistance of deep-sea equipment and its preparation method. Background Technology

[0002] Currently, deep-sea equipment is developing rapidly, and deep-sea operating conditions present comprehensive requirements such as high external pressure, low temperature, corrosion resistance, and watertightness. The superposition of extremely high seawater external pressure and structural stress makes pressure-resistant structures subject to severe stress and prone to instability; at the same time, the reduced oxygen content in the deep sea weakens the passivation ability of material surfaces, increasing the tendency for corrosion and cracking, which places higher demands on the safety and reliability design of pressure-resistant structures. Carbon fiber reinforced epoxy resin matrix composites (CFRP) have advantages such as light weight, high strength, and designability, and are increasingly being used in deep-sea pressure hulls.

[0003] In existing deep-sea pressure-resistant equipment, the following designs utilize composite materials in conjunction with flanges for connection:

[0004] (1) Flange directly connected to composite material cylinder, with an outer polymer transition layer:

[0005] A typical technology using this solution is a Chinese utility model patent for a connection structure between a pressure-resistant pontoon composite material cylinder and a metal joint (publication number CN216424689U). Its polyurethane anti-seepage layer covers the outer surface of the connecting cylinder, and the two ends of the polyurethane anti-seepage layer cover the outer circumferential surfaces of the upper end cover flange and the lower end cover flange, respectively. The surface of the polyurethane anti-seepage layer is smooth and continuous.

[0006] The polyurethane anti-seepage layer in this solution plays a role in dispersing stress, but it does not solve the problem of mismatch in mechanical properties between the composite material cylinder and the flange connection position.

[0007] (2) Composite material cylinder sleeved outside the flange:

[0008] A typical technology employing this solution is a Chinese invention patent for a composite material pressure-resistant housing, its molding die and molding method (publication number CN118651337A). It features reinforcing ribs integrally formed with the housing body, the reinforcing ribs being located on the inner wall of the housing body, and symmetrical first and second oblique angles on the end faces of the reinforcing ribs, as well as metal flange rings. It also includes mounting holes for instrument and equipment installation and groove structures for arranging cable guides. A metal flange ring abuts against each of the first and second oblique angles.

[0009] This scheme uses a combination of reinforcing ribs and metal flanges to cover the composite material cylinder with flanges. In essence, it is not a scheme to connect the metal flange to the composite material cylinder. The metal flange merely serves as the internal skeleton of the composite material cylinder.

[0010] (3) Composite material core material filling scheme with flange bolted core material filling scheme:

[0011] A typical technology employing this solution is a Chinese invention patent (publication number CN113815767A) describing an end connection structure and manufacturing method for a sandwich composite pressure-resistant shell. This structure includes an inner composite material layer, an outer composite material layer, and an internal filling core material between the inner and outer composite material layers. The end connection structure includes an inner composite material flange at the end of the inner composite material layer, an outer composite material flange at the end of the outer composite material layer, a split-type embedded ring installed between the inner and outer composite material flanges, a transition flange at the end of the connection structure, and a composite material reinforcing ring at the connection between the split-type embedded ring and the internal filling core material. The transition flange has countersunk threaded through holes and is fixedly connected to the split-type embedded ring using countersunk / counterhead bolts.

[0012] This design features an inner and outer composite material cylinder, with an internal filling core material having a transition structure sandwiched between the two cylinders. The internal filling core material is then bolted to the flange. Although this design avoids direct connection between the composite material cylinder and the metal flange, stress concentration issues still exist at the bolted connection point. Furthermore, the addition of the core material further exacerbates the pressure mismatch problem among the various materials.

[0013] (4) Setting up a matching scheme between a continuously tapered flange and a composite material cylinder:

[0014] A typical technology that adopts this solution is a Chinese invention patent for a composite material pressure-resistant shell and its molding method (publication number CN103482014A). The pressure-resistant shell includes a metal frame, and a first fiberglass layer, a titanium wire winding layer, a second fiberglass layer, a carbon fiber layer and a protective layer that are laid out outside the metal frame.

[0015] The scheme combines the transition structure of the metal flange with the multi-layer pressure-bearing layer. The layered pressure-bearing of this scheme is not substantially improved compared with scheme (3). It only removes the bolted connection. The stress transmission problem still exists at the overlap position of the composite material and the metal flange.

[0016] (5) Composite material cylinder as internal skeleton:

[0017] A typical technology that adopts this solution is the pressure-resistant structure of a deep-sea submersible (publication number CN110217336A), which is made of rolled titanium alloy plate and welded by longitudinal welds. The shrinkage force of the welded shell makes its inner wall fit tightly with the inner shell ring rib. The shell is then connected to the left flange and the right flange by the ring welds on both sides.

[0018] In this design, the composite material cylinder is used as a supporting frame. However, under pressure, the deformation of the composite material cylinder and the outer shell are significantly asynchronous, as can be seen from the accompanying drawings in the instruction manual. Figure 1 The design of the inner shell with distributed support shows that it also fails to solve the problem of the fit between the composite material cylinder and the metal flange, and cannot effectively distribute the stress at the contact point.

[0019] However, the existing manufacturing technologies mentioned above still have significant shortcomings under the requirements of deep-sea external pressure service: First, existing composite pressure-resistant cylinders mostly adopt equal thickness design or local stepped thickening reinforcement to meet the end load-bearing requirements. However, under the combined action of external pressure and end constraints, equal thickness structures are prone to stress concentration and local instability risks near the ends. Stepped thickening will also create stiffness discontinuity at the thickness abrupt change, resulting in uneven load transmission and easily inducing interlayer stress concentration, resin enrichment, or molding defects, thereby reducing the external pressure stability and structural reliability. Second, the flange-composite material connection is a dissimilar material connection interface, which must not only bear the force but also directly form the interface sealing path at the shell end. Existing practices mostly rely on flange surface pretreatment and composite material overlap to achieve the connection. However, under the conditions of equal thickness or simple geometric connection ends, the interface stress caused by shear / peel load and curing shrinkage in the connection area is difficult to effectively disperse. The interface bonding strength and interface density are quite sensitive to the pretreatment quality, overlap structure, and molding process, resulting in the risk of interface micro-leakage and uncertainty of long-term watertight reliability. Third, for long-scale pressure shells, under the combined action of external pressure and end connection constraints, if the thickness transition of the composite material and the geometric configuration of the flange connection end are not optimized in coordination, problems such as uneven load transfer in the connection area and stress concentration at the interface will be aggravated, which is not conducive to simultaneously obtaining stable load-bearing capacity and interface watertight reliability. Summary of the Invention

[0020] This invention proposes a method for preparing a composite-metal shell with variable thickness for deep-sea equipment under high pressure. It focuses on the coordinated optimization of two aspects: "variable thickness transition of composite shell" and "variable thickness geometry of flange connection end". By continuously and gradually varying the thickness of the composite shell along the axial direction and optimizing the layup-winding, the load is smoothly transferred between the shell body and the end connection area. By constructing a more favorable composite covering-lap joint force transmission path through the variable thickness structure of the flange connection end and improving the shear resistance and peel resistance of the connection area, the stable load-bearing capacity and long-term service reliability of the shell under high external pressure environment are improved.

[0021] Addressing the bottleneck of hulls facing both high external pressure and highly reliable watertight connections in deep-sea environments, this invention solves the technical problems of existing composite material hulls, such as instability under long-term external pressure, stress concentration in the transition zone of varying thickness, easy peeling and uneven force transmission at the end metal-composite interface, leading to insufficient watertight reliability and long-term service stability at the connection interface. This invention is based on a combined structure of metal end connectors and a composite material main load-bearing hull. It collaboratively designs stable external pressure bearing, smooth end load introduction, and watertight reliability at the connection interface as unified objectives, and integrates structural design with manufacturing process constraints, enabling the structural design results to be directly converted into a set of manufacturable process parameters.

[0022] A method for preparing a variable-thickness, high-pressure-resistant composite-metal shell for deep-sea equipment includes the following steps:

[0023] Step S1: Determine the overall structure of the pressure-resistant shell, perform variable thickness design and layup design of the composite material shell, and conduct finite element verification and structural optimization;

[0024] Step S2: Flange design and pretreatment;

[0025] Step S3: Laying and wrapping into one piece;

[0026] Step S4: Integrated curing and molding;

[0027] Step S5: Demolding.

[0028] Optionally, in step S1, the overall structure of the pressure-resistant shell adopts a combination of metal flanges and composite material shell;

[0029] The variable thickness design of the composite material shell includes: dividing the composite material shell along the axial direction into a conventional load-bearing zone, a reinforcement zone, and a transition zone between the conventional load-bearing zone and the reinforcement zone. The reinforcement zone is thicker than the conventional load-bearing zone, and the transition zone adopts a continuous and gradual thickness transition.

[0030] The composite material shell layup design includes: treating the end connection constraints as design inputs for the overall pressure shell structure; using [90° / 0° / 90° / +45° / -45° / -45° / +45° / 90° / 0° / 90°]n layup as the basic layup method for the conventional load-bearing zone, reinforcement zone, and transition zone; adding ±45° layup in the reinforcement zone near the metal flange and transition zone; and adding axial layup in the conventional load-bearing zone near the transition zone.

[0031] The ±45° ply configuration is [+45° / -45° / -45° / +45°]n or [-45° / +45° / +45° / -45°]n;

[0032] The axial layup pattern is [90° / 0° / 0° / 90°]n or [0° / 90° / 90° / 0°]n.

[0033] Optionally, in step S2, the flange design includes: forming an end load introduction and interface force transmission structure between the metal flange and the composite material shell through an overlap-coverage connection area; the metal flange is provided with an outer peripheral sidewall connection section integrally formed with the composite material shell; the outer peripheral sidewall connection section is located on the outer surface of the metal flange; during the forming process, the composite material overlaps and covers the outer peripheral sidewall connection section and is cured to form a continuous overlap-coverage connection area outside the outer peripheral sidewall connection section, and continuously transitions with the composite material shell layup.

[0034] Optionally, in step S2, the flange design further includes: providing at least two circumferentially arranged boss structures at the tail end of the metal flange, wherein the boss is an outwardly protruding structure provided on the outer surface of the tail end of the metal flange, and at least two are arranged circumferentially without interval; the boss outline adopts an arc-shaped structure, and the outer diameter of the boss protrudes outward relative to the outer diameter of the reinforcement area.

[0035] Optionally, in step S2, the pretreatment includes: roughening the metal surface of the connecting section of the outer peripheral sidewall by sandblasting before the composite material is laid and wound into an integral shape.

[0036] Optionally, in step S2, the pretreatment also includes: cleaning, drying, and anti-corrosion or primer treatment after sandblasting roughening the metal surface.

[0037] Optionally, in step S3, the composite material shell and the end connection interface are constructed synchronously in the same forming process using an integrated lay-up process. This allows the composite material to form a continuous overlapping-covering connection area on the outer peripheral sidewall connection section with a boss at the tail end of the metal flange. The outer peripheral sidewall connection section does not include the outer peripheral sidewall of the large disc at the bottom of the metal flange. It is continuously connected with the lay-up of the shell's conventional load-bearing area, transition area, and reinforcing area, so that the overlapping-covering connection area and the conventional load-bearing area of ​​the composite material shell are continuously transitioned in space, forming an integrated structure of flange-composite material shell. The lay-up method of the overlapping-covering connection area is [90° / 0° / 90° / +45° / -45° / -45° / +45° / 90° / 0° / 90°]n lay-up.

[0038] Optionally, in step S4, the flange-composite material shell integrated structure after the laying is integrally cured and molded, so that the overlapping-covering connection area and the composite material shell are cured synchronously to form an integral load-bearing structure;

[0039] In step S4, during the integral curing process, the layup structure is compressed and / or vacuum degassing is controlled so that the interface bonding of the end overlap-coverage connection area and the load-bearing performance of the shell body are formed consistently in the same curing process.

[0040] Optionally, in step S5, demolding includes: demolding after integral curing and molding, removing the mold and curing auxiliary materials, and obtaining a pressure-resistant shell component with an integrally formed composite material shell and flange.

[0041] This application also provides a composite-metal shell for deep-sea equipment with variable thickness and high pressure resistance, which is prepared using any of the aforementioned methods for preparing a composite-metal shell for deep-sea equipment with variable thickness and high pressure resistance.

[0042] It includes a metal flange, a composite material shell, and an lap-covered connection area. The composite material shell includes a conventional load-bearing area, a reinforcing area, and a transition area between the conventional load-bearing area and the reinforcing area.

[0043] The beneficial effects of this invention are as follows:

[0044] (1) By using the variable thickness partitioning and continuous gradual transition design of the composite main load-bearing shell, and adopting the symmetrical lay-up-winding scheme with circumferential load as the main component, the load-bearing path distribution under external pressure load is improved, the stress concentration and local instability risk in the transition zone and end area are reduced, and the overall external pressure resistance stability is improved.

[0045] (2) By configuring axial and ±45° ply between the end and the transition zone, the end load can be gradually transitioned and smoothly introduced into the composite main load-bearing structure, thereby improving the uniformity of end force transmission and enhancing structural reliability.

[0046] (3) By sandblasting the flange-composite interface to form a rough morphology and micro-pit structure, resin wetting and mechanical interlocking are promoted. Combined with the "variable thickness" structure of at least two bosses at the tail end, the force direction of the interface is changed, the risk of unfavorable stress and peeling of the interface is reduced, and the reliability of metal-composite interface bonding and end force transmission is improved. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 A three-dimensional schematic diagram of a high-pressure-resistant composite-metal shell for deep-sea equipment with variable thickness provided in this application embodiment;

[0049] Figure 2 A front view schematic diagram of the variable thickness, high-pressure resistant composite-metal shell for deep-sea equipment provided in this application embodiment.

[0050] Figure 3 for Figure 2 AA section view;

[0051] Figure 4 The diagram shows the layup / winding angle and fiber direction, where (a) is a schematic diagram of axial layup; and (b) is a schematic diagram of ±45° layup.

[0052] Figure 5 A three-dimensional schematic diagram of the variable-thickness, high-pressure resistant composite-metal shell for deep-sea equipment, provided in an embodiment of this application, after concealing one end of the overlap and covering the connection area;

[0053] Figure 6 A front view of the variable thickness, high pressure resistant composite-metal shell for deep-sea equipment provided in this application embodiment after concealing one end of the overlap-covering connection area;

[0054] Figure 7 for Figure 6 Enlarged view of point B;

[0055] The attached figures are labeled as follows: 1-Composite material shell; 2-Metal flange; 3-Conventional load-bearing area; 4-Transition area; 5-Reinforcement area; 6-Flange variable thickness boss; 7-Overlap-coverage connection area. Detailed Implementation

[0056] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0057] See Figures 1-3 This application provides a method for preparing a composite-metal shell with variable thickness and high pressure resistance for deep-sea equipment, which specifically includes the following steps:

[0058] Step S1: Determine the overall structure of the pressure-resistant shell, design the variable thickness and layup of the composite material shell 1, and perform finite element verification and structural optimization.

[0059] In step S1, the overall structure of the pressure-resistant shell adopts a combination of metal flange 2 (i.e., metal end connector) and composite material main load-bearing shell (i.e., composite material shell 1), and is designed as an integrated system with stable load bearing under external pressure conditions and smooth introduction of end loads as the core. The composite material main load-bearing shell is divided along the axial direction into a conventional load-bearing zone 3, a reinforcement zone 5, and a transition zone 4 between the two. The reinforcement zone 5 is thicker than the conventional load-bearing zone 3, while the transition zone 4 is not a stepped thickening or a local abrupt change, but a continuous and gradual thickness transition, so that the shell stiffness and load-bearing capacity are continuously varied along the axial direction. To reduce stress concentration and instability sensitivity, the overall structure incorporates "end connection constraints" as a design input. A ±45° layup is added in the reinforcement zone 5 near the metal flange 2 and transition zone 4, and an axial layup is added in the conventional load-bearing zone 3 near the transition zone 4. This allows the end load to transition smoothly from the metal end connector to the composite main load-bearing shell, thus forming a "circumferential main load-bearing - multi-directional force transmission at the end / transition zone 4 - continuous gradual anti-concentration" overall design approach together with the symmetrical layup in the conventional load-bearing zone 3, which is predominantly circumferential.

[0060] Compared to common schemes involving uniform shell thickness, stepped thickness, or localized stress concentration caused by end rigidity, this approach significantly reduces stress concentration and instability sensitivity in the transition region between the ends and varying thicknesses, thereby improving the overall stability and load-bearing capacity under external pressure. Furthermore, based on finite element analysis results, structural optimization was performed on the range of reinforcement zone 5, the gradual change form of transition zone 4, and the ply parameters at the ends / transition zone 4.

[0061] In this embodiment, the specific implementation of "treating the end connection constraints as design inputs for the overall pressure hull structure" is as follows:

[0062] First, clarify the core boundary conditions and load inputs of the end connection constraints: define the connection interface between the metal flange 2 (end connector) and the composite shell 1 as a fixed constraint, and limit the axial displacement, radial displacement and rotational degrees of freedom of this interface; at the same time, in combination with the characteristics of deep external pressure conditions, incorporate the axial tensile force, shear force, bending stress, modulus difference and stiffness difference between the metal flange 2 and the composite shell 1 generated by the external pressure into the design input parameters.

[0063] Based on the above constraints, the layup design of the composite shell 1 ensures a smooth transition in stiffness during the transfer of load from the metal flange 2 to the composite shell 1, avoiding sudden load changes caused by constraints.

[0064] In this embodiment, the "structural optimization of the range of reinforcement zone 5, the gradient form of transition zone 4, and the ply parameters of end / transition zone 4 based on the finite element verification results" adopts a closed-loop iterative process, and the specific steps are as follows:

[0065] First, construct the overall finite element model of the pressure-resistant shell. Import the material performance parameters of the composite shell 1 (including at least the elastic modulus, Poisson's ratio, and ultimate tensile strength), the structural parameters and material properties of the metal flange 2, the external pressure load value, the aforementioned end connection constraints, the initial design of the variable thickness zones (conventional load-bearing zone 3, reinforcing zone 5, and transition zone 4), and the initial layup scheme (including the initial layup angle, number of layers, and arrangement sequence) into the finite element analysis software to complete the model construction.

[0066] Then, finite element verification and key index extraction were performed. Stress analysis and stability analysis were conducted on the above model under external pressure conditions, and core verification indices were extracted. The core verification indices include at least the maximum principal stress and stress concentration factor of the conventional bearing zone 3, the reinforcement zone 5 and the transition zone 4; the overall instability critical pressure and buckling mode of the shell; the stiffness change rate of the transition zone 4; and the shear stress and peel stress at the connection interface between the metal flange 2 and the composite shell 1.

[0067] Based on the above conditions, iterative optimization is carried out, including sequential optimization of the range of reinforcement zone 5, optimization of the gradient form of transition zone 4, and optimization of the ply parameters of end / transition zone 4.

[0068] The optimization of the reinforcement zone 5 includes: if the finite element verification results show that the stress value of a certain axial interval is close to the material strength limit or the instability risk coefficient exceeds the standard, then the reinforcement range of the region is expanded along the axial direction; if the stress level of a certain reinforcement zone 5 is significantly lower than the design threshold and does not affect the overall stability, then its axial length can be shortened or its circumferential coverage can be reduced to achieve lightweight design.

[0069] The optimization of the transition zone 4 gradient form includes: if the check finds that there is a stress peak or stiffness change in the transition zone 4, the original stepped transition or local change form will be adjusted to a continuous gradient form. As a feasible implementation plan, linear gradient or nonlinear gradient (such as parabolic gradient) can be adopted. By adjusting the axial length and gradient slope of the transition zone 4, the shell wall thickness can be continuously changed along the axial direction to ensure a smooth transition of stiffness and load-bearing capacity and reduce the stress concentration factor.

[0070] The optimization of the ply parameters in the end / transition zone 4 includes: if the shear stress at the end connection interface exceeds the standard, or the axial load transfer is not smooth, then increase the number of ±45° ply layers or adjust their ply ratio; if the axial tension causes excessive local stress, then increase the number of axial ply layers; after adjusting the ply parameters, it is necessary to ensure that the total thickness of the axial ply and the ±45° ply does not exceed the design allowable range and is compatible with the thickness gradient law of the transition zone 4.

[0071] Finally, optimization verification is carried out. The adjusted structural parameters and layup scheme are re-imported into the finite element model, and the optimization verification process is repeated iteratively until the stress concentration coefficient of each region is controlled within the allowable range, the critical pressure of shell instability meets the design requirements, the end load is smoothly transferred, and the overall structure achieves the optimal balance between weight and strength, thus completing the structural optimization.

[0072] like Figures 1-3 As shown, the overall structure of the pressure-resistant shell consists of a composite material shell 1 and a metal flange 2 located at the end of the shell. The composite material shell 1 is divided into a conventional load-bearing zone 3, a transition zone 4 and a reinforcement zone 5 along the axial direction. The reinforcement zone 5 is thicker than the conventional load-bearing zone 3. The transition zone 4 adopts a continuous and gradual thickness transition, so that the shell stiffness and load-bearing capacity change continuously along the axial direction, thereby reducing stress concentration and instability sensitivity caused by sudden changes in thickness.

[0073] The composite shell 1 ply design includes: treating the end connection constraints as design input for the overall pressure shell structure, using [90° / 0° / 90° / +45° / -45° / -45° / +45° / 90° / 0° / 90°]n ply as the basic ply method for the conventional load-bearing zone 3, the reinforcing zone 5, and the transition zone 4, adding ±45° ply in the area of ​​the reinforcing zone 5 near the metal flange 2 and the transition zone 4, and adding axial ply in the area of ​​the conventional load-bearing zone 3 near the transition zone 4.

[0074] The ±45° ply pattern is [+45° / -45° / -45° / +45°]n or [-45° / +45° / +45° / -45°]n;

[0075] The axial layup pattern is [90° / 0° / 0° / 90°]n or [0° / 90° / 90° / 0°]n.

[0076] n indicates the number of times the layer is repeated, which is determined based on actual needs.

[0077] Adding a ply can refer to directly adding a corresponding ply at a given location, or, when using an optimization method based on finite element analysis, using a ply of the appropriate type at that location to compensate for strength.

[0078] In this embodiment, the layup angle is as follows: Figure 4 (a) and Figure 4As shown in (b), the shell adopts symmetrical plying with circumferential plying as the main form of the external pressure main load-bearing structure. Simultaneously, ±45° plying is added near the ends and in transition zone 4 (in this embodiment, ±45° plying is added throughout the reinforcement zone 5) to bear the axial and shear transmission requirements introduced by the end connection constraints. This allows the end load to transition smoothly from the metal end connectors to the composite main load-bearing shell, thus forming a continuous, gradually varying thickness structure of "conventional load-bearing zone 3 - transition zone 4 - reinforcement zone 5" together with the overall design route of "circumferential main load-bearing - multi-directional force transmission at the ends / transition zone 4 - continuous, gradually varying anti-concentration". Based on the finite element verification results, the range of reinforcement zone 5, the gradual change form of transition zone 4, and the plying parameters of the ends / transition zone 4 are structurally optimized.

[0079] Step S2: Flange design and pretreatment.

[0080] In step S2, the metal flange 2 and the composite material main load-bearing shell form an end load introduction and interface force transmission structure through an overlap-coverage connection area 7. The structural design and pretreatment of the metal flange 2 are focused on improving the anchoring capacity of the metal-composite interface and reducing unfavorable interface forces: the metal flange 2 is provided with an outer peripheral sidewall connection section for integral forming with the composite material shell 1, so that the composite material forms a continuous overlap-coverage connection area 7 in the outer peripheral sidewall connection section and transitions continuously with the shell ply, so as to achieve a smooth introduction of end loads to the composite material main load-bearing structure. To reduce the concentrated load and peeling risk at the metal-composite interface, the metal flange 2 is provided with at least two circumferentially arranged boss structures at its tail end. The bosses form a locally "variable thickness" geometric transition, which changes the direction of the interface force transmission path, thereby transforming the unfavorable interface force components into more favorable shear / compression force transmission components, thereby reducing the interface load and improving the peeling resistance reliability of the end connection area.

[0081] like Figures 5-7 As shown, the metal flange 2 and the composite material shell 1 form an end load introduction and interface force transmission structure through an overlap-coverage connection area 7. To reduce the concentrated load and peeling risk at the metal-composite interface, the metal flange 2 is provided with at least two flange variable thickness bosses 6 arranged circumferentially at its tail end. The bosses form a local "variable thickness" geometric transition, which changes the direction of the interface force transmission path, thereby transforming the unfavorable force component of the interface into a more favorable shear / compression force component, thereby reducing the interface load and improving the peeling resistance reliability.

[0082] Specifically, in this embodiment, at least two circumferentially arranged boss structures are provided at the tail end of the metal flange 2. The bosses are outwardly protruding structures provided on the outer surface of the tail end of the metal flange 2, and at least two are arranged circumferentially without intervals. The boss transition adopts an arc-shaped structure, and the outer diameter of the boss protrudes outward relative to the outer diameter of the reinforcing area 5. The provision of the boss at the tail end of the metal flange 2 forms a locally "variable thickness" geometric transition: on the one hand, the arc transition ensures that the composite material layup can continuously overlap and cover at this point and continuously transition with the shell layup, avoiding sharp bends in the layup; on the other hand, after curing, a geometric interlocking / locking interface of "boss-composite layer" is formed, thereby improving the anti-peeling and anti-relative slippage ability of the connection area, and realizing a reliable fit and integrated connection between the boss structure and the composite material shell 1.

[0083] Before the composite material is integrally wound, the connection section between the metal flange 2 and the integrally formed outer peripheral sidewall of the composite material is pretreated. Pretreatment includes at least cleaning, drying, and sandblasting to roughen the metal surface, creating an uneven, rough morphology and micro-pitted structure. This rough morphology and micro-pitted structure facilitate resin wetting and penetration, forming mechanical interlocking, thereby improving the bonding strength and density of the composite-metal interface. Simultaneously, it allows the resin to embed and form mechanical interlocking and locking after curing, thus strengthening the metal-composite interface bonding force. After sandblasting, cleaning, drying, and necessary anti-corrosion / priming treatments can be performed to improve the durability of the interface bonding in a seawater environment.

[0084] Step S3: Laying and wrapping into one piece.

[0085] In step S3, the composite shell 1 and the end connection interface are constructed synchronously in the same forming process by using a lay-up and / or fiber winding integrated lay-up process. This allows the composite material to form a continuous overlap-coverage connection area 7 on the outer surface of the metal flange 2, and continuously connect with the conventional load-bearing area 3 / transition area 4 / reinforcing area 5 of the shell. By making the overlap-coverage connection area 7 and the main load-bearing lay-up of the shell continuously transition in space and gradually introduce the end load in terms of force, the local concentration effect caused by the "rigid cut-off" connection at the end is avoided. This allows the end load to be transmitted more smoothly from the metal flange 2 to the main load-bearing structure of the composite shell 1, improving the uniformity of force transmission in the end area and the interface anti-peeling reliability.

[0086] The metal flange 2 and the composite material shell 1 are integrally formed by laying and wrapping. The composite material shell 1 and the end connection interface are constructed synchronously in the same forming process, so that the composite material forms a continuous overlapping-covering connection area 7 on the outer surface of the metal flange 2, and is continuously connected with the conventional load-bearing area 3, transition area 4 and reinforcement area 5 of the shell.

[0087] The composite material can be made of carbon fiber reinforced epoxy resin-based prepreg; the layup angle is as follows: Figure 4As shown, the base ply uses a [90° / 0° / 90° / +45° / -45° / -45° / +45° / 90° / 0° / 90°]n ply, where 0° and ±45° can be formed by unidirectional ply, and 90° can be formed by winding.

[0088] Step S4: Integral curing and molding.

[0089] The flange-composite material shell integrated structure, after being laid up, is integrally cured and molded, so that the overlap-coverage connection area 7 and the composite material shell 1 are cured simultaneously to form an integral load-bearing structure. During the curing process, the layup structure can be compressed and / or vacuum degassing controlled to reduce porosity and inclusion defects and improve the interlayer bonding quality. This ensures that the interfacial bonding of the end overlap-coverage connection area 7 and the load-bearing performance of the shell body are formed consistently in the same curing process, thereby guaranteeing the shell's forming consistency and structural integrity.

[0090] Step S5: Demolding.

[0091] After curing, demolding is performed to remove the mold and curing auxiliary materials, resulting in a pressure-resistant shell component with composite material shell 1 integrally formed with the flange.

[0092] The specific finite element simulation method in step S1 can be achieved by those skilled in the art using general finite element software, and will not be described in detail here.

[0093] To avoid the impact of air bubbles on shell performance during the layup process, periodic vacuum degassing can be performed during layup / winding; after layup and winding at the predetermined layup angle, segmented pre-pressing and shaping and surface repair can be performed; after layup, curing, cooling and demolding can be performed according to the resin system process requirements;

[0094] To improve the protection of the outer surface and the watertightness of the pores, the outer surface can be polished, coated with primer, and then sprayed with a protective layer to form a hydrophobic layer, thereby improving the adaptability to the marine environment and the reliability of long-term service.

[0095] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a high-pressure resistant composite-metal shell for deep-sea equipment with variable thickness, characterized in that: Includes the following steps: Step S1: Determine the overall structure of the pressure-resistant shell, perform variable thickness design and layup design of the composite material shell, and conduct finite element verification and structural optimization; Step S2: Flange design and pretreatment; Step S3: Laying and wrapping in one piece; Step S4: Integrated curing and molding; Step S5: Demolding; In step S1, the overall structure of the pressure-resistant shell adopts a combination of metal flanges and composite material shells; The variable thickness design of the composite material shell includes: dividing the composite material shell along the axial direction into a conventional load-bearing area, a reinforcement area, and a transition area between the conventional load-bearing area and the reinforcement area; the reinforcement area is thicker than the conventional load-bearing area; and the transition area adopts a continuous and gradual thickness transition. The composite material shell layup design includes: processing the end connection constraints as design input for the overall structure of the pressure-resistant shell, using [90° / 0° / 90° / +45° / -45° / -45° / +45° / 90° / 0° / 90°]n layup as the basic layup method for the conventional load-bearing area, reinforcement area and transition area, adding ±45° layup in the reinforcement area near the metal flange and transition area, and adding axial layup in the conventional load-bearing area near the transition area; The ±45° ply pattern is [+45° / -45° / -45° / +45°]n or [-45° / +45° / +45° / -45°]n; The axial layup pattern is [90° / 0° / 0° / 90°]n or [0° / 90° / 90° / 0°]n; In step S2, the flange design includes: forming an end load introduction and interface force transmission structure between the metal flange and the composite material shell through an overlap-coverage connection area; the metal flange is provided with an outer peripheral sidewall connection section integrally formed with the composite material shell; the outer peripheral sidewall connection section is located on the outer surface of the metal flange; during the forming process, the composite material overlaps and covers the outer peripheral sidewall connection section and is cured to form a continuous overlap-coverage connection area outside the outer peripheral sidewall connection section, and continuously transitions with the composite material shell layup.

2. The method for preparing a variable-thickness, high-pressure-resistant composite-metal shell for deep-sea equipment as described in claim 1, characterized in that: In step S2, the flange design further includes: providing at least two circumferentially arranged boss structures at the tail end of the metal flange, wherein the boss is an outwardly protruding structure provided on the outer surface of the tail end of the metal flange, and at least two are arranged circumferentially without intervals; the boss outline adopts an arc-shaped structure, and the outer diameter of the boss protrudes outward relative to the outer diameter of the reinforcement area.

3. The method for preparing a variable-thickness, high-pressure-resistant composite-metal shell for deep-sea equipment as described in claim 1, characterized in that: In step S2, the pretreatment includes: roughening the metal surface of the outer peripheral sidewall connecting section by sandblasting before the composite material is laid and wound into an integral shape.

4. The method for preparing a variable-thickness, high-pressure-resistant composite-metal shell for deep-sea equipment as described in claim 3, characterized in that: In step S2, the pretreatment further includes: cleaning, drying, and anti-corrosion or primer treatment after sandblasting roughening the metal surface.

5. The method for preparing a variable-thickness, high-pressure-resistant composite-metal shell for deep-sea equipment as described in claim 1, characterized in that: In step S3, the composite material shell and the end connection interface are constructed synchronously in the same forming process using an integrated lay-up process. This allows the composite material to form a continuous overlapping-covering connection area on the outer peripheral sidewall connection section with a boss at the tail end of the metal flange. The outer peripheral sidewall connection section does not include the outer peripheral sidewall of the large disc at the bottom of the metal flange. It is continuously connected with the lay-up of the shell's conventional load-bearing area, transition area, and reinforcing area, so that the overlapping-covering connection area and the conventional load-bearing area of ​​the composite material shell are continuously transitioned in space, forming an integrated flange-composite material shell structure. The lay-up pattern of the overlapping-covering connection area is [90° / 0° / 90° / +45° / -45° / -45° / +45° / 90° / 0° / 90°]n lay-up.

6. The method for preparing a variable-thickness, high-pressure-resistant composite-metal shell for deep-sea equipment as described in claim 1, characterized in that: In step S4, the flange-composite material shell integrated structure that has been laid and wrapped is integrally cured and molded, so that the overlapping-covering connection area and the composite material shell are cured synchronously and form an integral load-bearing structure. In step S4, during the integral curing process, the layup structure is compressed and / or vacuum degassing is controlled so that the interface bonding of the end overlap-coverage connection area and the load-bearing performance of the shell body are formed consistently in the same curing process.

7. The method for preparing a variable-thickness, high-pressure-resistant composite-metal shell for deep-sea equipment as described in claim 1, characterized in that: In step S5, the demolding includes: demolding after the integral curing molding is completed, removing the mold and curing auxiliary materials, and obtaining a pressure-resistant shell component with an integrally formed composite material shell and flange.

8. A composite-metal shell for deep-sea equipment with variable thickness and high pressure resistance, characterized in that: It was prepared using the method for preparing a variable-thickness, high-pressure resistant composite-metal shell for deep-sea equipment as described in any one of claims 1-7; It includes a metal flange, a composite material shell, and an overlap-coverage connection area. The composite material shell includes a conventional load-bearing area, a reinforcing area, and a transition area between the conventional load-bearing area and the reinforcing area.

Images