Forming method of composite material pressure vessel

Abstract

The invention relates to a composite material pressure vessel forming method which comprises the following steps: rigidly connecting a front joint and a rear joint to two ends of a positioning shaft to form a support frame body; the supporting frame body is vertically fixed, the 3D printer is driven to extrude fiber reinforced thermoplastic composite wires in the circumferential direction of the positioning shaft, and a printing layer is formed between the front connector and the rear connector; the supporting frame body with the printing layer is horizontally installed on a horizontal rotating support, a positioning shaft is driven to rotate, prepreg fibers are wound around the outer surface of the printing layer, and a fiber winding layer is formed; and after the front / rear skirt is mounted, curing to form an integral structure, and finally removing the horizontal rotating bracket and the positioning shaft. The printing layer is constructed through the 3D printing technology, then the prepreg fibers are wound on the outer surface of the printing layer, and the design precision, the forming efficiency and the bursting pressure of the container are guaranteed; and finally, the prepreg fibers are cured on the printing layer, the interfacial shear strength between the prepreg fibers and the printing layer is guaranteed, and demolding is not needed.

Description

Technical Field

[0001] The present invention relates to the technical field of composite pressure vessel molding, and in particular to a composite pressure vessel molding method. Background Art

[0002] As a lightweight load-bearing component, the external dimensions of a composite pressure vessel directly affect its load-bearing capacity. The material used for composite wound pressure vessels is mainly thermosetting resin-based continuous fiber reinforced composite materials, which are wound on a core mold and then cured and molded. After curing and molding, the winding core mold needs to be separated from the composite material and demolded. The demolding process is not only time-consuming but also carries the risk of damaging the composite material. Currently, the demolding time is mainly shortened by using an airbag core mold. However, since the airbag core mold relies on internal pressure to support the surface, its surface accuracy is not high. Summary of the Invention

[0003] To address the problems of the existing winding molding technology, such as long demoulding process, easy damage to composite materials, and low surface precision, the present invention provides the following technical solutions: The present invention provides a composite pressure vessel forming method, comprising: The front joint and the rear joint are rigidly connected to both ends of the positioning shaft to form a support frame; The support frame is fixed vertically, and the 3D printer is driven to extrude fiber-reinforced thermoplastic composite material filament along the circumference of the positioning axis to form a printing layer between the front and rear joints; The support frame with the printed layer is horizontally mounted on the horizontal rotating bracket, and the positioning shaft is driven to rotate and the prepreg fiber is wound around the outer surface of the printed layer to form a winding layer; After the front / rear skirts are installed and cured to form an integral structure, the horizontal rotating bracket and positioning shaft are finally removed.

[0004] The present invention provides a composite pressure vessel forming method, comprising:

[0005] The front joint and the rear joint are rigidly connected to both ends of the positioning shaft to form a support frame;

[0006] The support frame is fixed vertically, and the 3D printer is driven to extrude fiber-reinforced thermoplastic composite material filament along the circumference of the positioning axis to form a printing layer between the front and rear joints;

[0007] The support frame with the printed layer is horizontally mounted on the horizontal rotating bracket, and the positioning shaft is driven to rotate and the prepreg fiber is wound around the outer surface of the printed layer to form a winding layer;

[0008] After the front / rear skirts are installed and cured to form an integral structure, the horizontal rotating bracket and positioning shaft are finally removed.

[0009] According to certain embodiments of the present invention, the fiber-reinforced thermoplastic composite material is a filament composed of a first fiber and a first thermoplastic resin; wherein:

[0010] The first fiber is one or a mixed fiber of carbon fiber, modified carbon fiber, quartz fiber, boron fiber, glass fiber, ceramic fiber, basalt fiber, alloy fiber; and / or,

[0011] The carbon fiber is a blend of two or more of T700 and T800; and / or

[0012] The first thermoplastic resin is one of PA, PP, PEEK, PEKK, PPS, PEI, PEEK-HT, PA12, PBT, PET, TPU, and PCL.

[0013] According to some embodiments of the present invention, the printed layer is a spiral layer; and / or,

[0014] The porosity of the printed layer is 0.5% to 0.75%; and / or,

[0015] The bearing strength of the printed layer is greater than the winding pressure of the prepreg fiber.

[0016] According to some embodiments of the present invention, the wrapped layer forms a fiber-reinforced layer with the printed layer after curing.

[0017] According to some embodiments of the present invention, the prepreg fiber is a second fiber impregnated with a second resin; and / or,

[0018] The second resin is a thermoplastic resin or a thermosetting resin, and its curing peak temperature is at least 30° C. lower than the melting point of the first thermoplastic resin; and / or,

[0019] The thickness of the printed layer accounts for 1% to 5% of the fiber reinforced layer.

[0020] According to some embodiments of the present invention, the second resin is a thermosetting resin; and / or,

[0021] The thermosetting resin is one of epoxy resin, bismaleimide, and phenolic resin; and / or,

[0022] The curing temperature of thermosetting resin is 60-160°C.

[0023] According to certain embodiments of the present invention, the front joint and the rear joint are tightly connected to the positioning shaft to achieve axial fixation and circumferential limiting connection.

[0024] According to some embodiments of the present invention, the horizontal rotating bracket is provided with two sets of horizontal rotating shafts, which are coaxially connected to the two ends of the positioning shaft, and the positioning shaft is synchronously driven to rotate around its axis by a servo motor.

[0025] According to certain embodiments of the present invention, the working pressure of the composite pressure vessel is 35-70 MPa.

[0026] According to some embodiments of the present invention, the outer surface of the printed layer is subjected to plasma treatment before winding the prepreg fibers.

[0027] The beneficial effects of the technical solutions provided in the embodiments of the present application include at least:

[0028] The present invention first uses 3D printing technology to construct a high-precision, rigidly supported printing layer to ensure the accuracy of the inner surface; then prepreg fibers are wrapped around the outer surface of the printing layer to ensure molding efficiency and the bursting pressure of the container; finally, the prepreg fibers and the printing layer are solidified into a whole, ensuring the interface shear strength between the prepreg fibers and the printing layer, and completely eliminating the traditional mold demolding process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0030] Figure 1 The figure is a flow chart of a composite pressure vessel forming method according to certain embodiments of the present invention.

[0031] Figure 2 This is a schematic diagram of the formation of a printed layer during the molding process of a composite pressure vessel in certain embodiments of the present invention.

[0032] Figure 3 Schematic diagram of the composite pressure vessel after forming a winding layer in some embodiments of the present invention.

[0033] Figure 4 This is a schematic diagram of a composite pressure vessel after being formed and after the horizontal rotating bracket and the positioning shaft are removed in certain embodiments of the present invention. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0035] For simplicity, only certain numerical ranges are explicitly disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with any other lower limit to form an unspecified range; similarly, any upper limit may be combined with any other upper limit to form an unspecified range. Furthermore, even if not explicitly stated, each point or individual value between the endpoints of a range is included in the range. Thus, each point or individual value may serve as its own lower limit or upper limit and be combined with any other point or individual value, or with other lower limits or upper limits, to form an unspecified range.

[0036] It should be noted that, in the description of the present invention, unless otherwise specified, “above” and “below” are inclusive, and the meaning of “multiple” in “one or more” is two or more. Relational terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms “include”, “comprising” or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence “comprising one…” do not exclude the presence of other identical elements in the process, method, article or device comprising the elements.

[0037] In the description of the present invention, the description with reference to the terms "any embodiment / method", "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine different embodiments / methods or examples and features of different embodiments / methods or examples described in this specification, unless they are contradictory.

[0038] The above summary of the invention is not intended to describe every disclosed embodiment or every implementation of the present invention. The following description more specifically illustrates exemplary embodiments. These embodiments can be used in various combinations. In each example, the examples are listed only as representative groups and should not be construed as exhaustive.

[0039] As mentioned above, the winding molding technology requires a core mold for support. The core mold is expensive, the surface accuracy is not high, the demolding time is long and the solidified layer is easily damaged.

[0040] Although 3D printing technology can print high-precision surfaces, its printing efficiency is low, and the printed profiles cannot meet the design requirements of the pressure vessel bursting pressure.

[0041] In view of this, the present invention first uses 3D printing technology to construct a high-precision, rigidly supported printing layer to ensure the accuracy of the inner surface; then prepreg fibers are wrapped around the outer surface of the printing layer to ensure molding efficiency and the bursting pressure of the container; finally, the prepreg fibers and the printing layer are solidified into a whole, ensuring the interface shear strength between the prepreg fibers and the printing layer, and completely eliminating the traditional mold demolding process.

[0042] Figure 1 The figure is a flow chart of a composite pressure vessel forming method according to certain embodiments of the present invention. Figure 2 This is a schematic diagram of the formation of a printed layer during the molding process of a composite pressure vessel in certain embodiments of the present invention. Figure 3 Schematic diagram of the composite pressure vessel after forming a winding layer in some embodiments of the present invention. Figure 4 This is a schematic diagram of a composite pressure vessel after being formed and after the horizontal rotating bracket and the positioning shaft are removed in certain embodiments of the present invention.

[0043] In an exemplary embodiment, as Figures 1 to 4 As shown, the composite pressure vessel forming method includes the following steps:

[0044] S1. The front joint and the rear joint are rigidly connected to both ends of the positioning shaft to form a support frame;

[0045] S2. The support frame is fixed vertically, and the 3D printer is driven to extrude the fiber-reinforced thermoplastic composite material filament along the circumference of the positioning axis to form a printed layer between the front and rear joints;

[0046] S3. The support frame with the printed layer is horizontally mounted to the horizontal rotating bracket, the positioning shaft is driven to rotate and the prepreg fiber is wound around the outer surface of the printed layer to form a winding layer;

[0047] S4. After installing the front / rear skirts and curing to form an integral structure, the horizontal rotating bracket and positioning shaft are finally removed.

[0048] The present invention first constructs a support frame as the basic structure for container molding, and the positioning shaft serves as the central axis, which can provide a reference for printing and winding, and ensure the coaxiality of the printing layer and the winding layer.

[0049] The present invention constructs the printing layer and the front and rear joints into an integrally formed core mold through 3D printing. This core mold can be directly used as the inner surface of the pressure vessel, and in the subsequent curing process, it is cured into a whole with the winding layer without the need for demolding. The present invention first places the support frame vertically, with the purpose of making the support frame the main load-bearing member in the printing process and reducing the force on the printing layer. During the printing process, the print head of the 3D printer rotates and prints along the circumference of the support frame, and accumulates the printing filament upward in circles, eventually forming a spiral or annular printing layer between the front and rear joints. Since it does not need to undergo curing deformation, the molded printing layer has high surface accuracy and can meet the accuracy requirements of the inner surface of the composite pressure vessel. The 3D printer adopts fused deposition modeling (FDM) or continuous fiber reinforced extrusion technology. Preferably, the 3D printer forms in one pass between the front and rear joints, which can save time and avoid separation between layers.

[0050] The present invention winds prepreg fibers on the outer surface of the printed layer to form a winding layer, the purpose of which is to speed up the rate of container molding. Although 3D printing technology can accurately construct complex surfaces, it is limited by the principle of layer-by-layer stacking, and the molding efficiency becomes a significant bottleneck. The present invention uses automated fiber winding technology to wind prepreg fibers on the outer surface of the printed layer, which ensures the accuracy of the inner surface of the container while significantly improving the container molding rate. In addition, from the perspective of the mechanical properties of the materials, the thermoplastic resins used in conventional 3D printing have the inherent defect of low compression modulus, which makes it difficult to meet the stringent design requirements of the bursting pressure of the pressure vessel. The present invention uses thermosetting resin as the winding matrix material, and its compression modulus is significantly improved compared to thermoplastic resin. Combined with the prestressed structure formed by the directional arrangement of fibers, the explosion resistance of the pressure vessel can be significantly improved.

[0051] The front and rear skirts installed in this invention can be used for subsequent system integration. The curing step crosslinks the resin in the prepreg fibers and diffuses it into the pores of the printed layer, enhancing the bond strength between the printed layer and the wound layer. After removing the horizontal rotating bracket and the precision positioning shaft system, a fully self-contained, independently molded pressure vessel with independent structural stability is obtained.

[0052] In an exemplary embodiment, the fiber-reinforced thermoplastic composite filament is a filament composed of a first fiber and a first thermoplastic resin. The first fiber accounts for 20% to 50% of the total weight of the filament. Too high will cause printing blockage, and too low will result in insufficient reinforcement effect. The first fiber needs to withstand the printing temperature (higher than the melting point of the first thermoplastic resin) to avoid breakage or carbonization at high temperature. Exemplarily, the first fiber is a mixed fiber of one or more of carbon fiber, quartz fiber, boron fiber, glass fiber, ceramic fiber, basalt fiber, and alloy fiber; in order to enhance the interfacial bonding force with the first thermoplastic resin, the surface of the first fiber is treated with a coupling agent. In order to ensure lightweight, the first fiber is preferably a mixed fiber of one or two of T700 and T800. The melting point range of the first thermoplastic resin needs to be compatible with the print head of the 3D printer, has good compatibility with the first fiber, and has small deformation after cooling and high impact strength. Illustratively, the first thermoplastic resin is one of PA, PP, PEEK, PEKK, PPS, PEI, PEEK-HT, PA12, PBT, PET, TPU, and PCL. To meet the burst pressure design requirements of the pressure vessel, the first thermoplastic resin is preferably PEEK or PEKK.

[0053] In an exemplary embodiment, the printed layers are spirally laid, with winding angles controlled within a range of 30°-85°. The fiber spacing is precisely positioned to ±0.2mm using CNC winding equipment. This spiral layup utilizes a constant tension, variable angle design, gradually transitioning to hoop winding in the pressure vessel head area, forming a closed-loop reinforcement structure composed of continuous fibers.

[0054] In an exemplary embodiment, the porosity of the printed layer is controlled within the range of 0.5% to 0.75%, aiming to achieve interface reinforcement with the fiber winding layer through its microporous structure. When the prepreg fibers are wound onto the surface of the printed layer, their resin matrix can penetrate into the pores by capillary action, forming a mechanical interlocking structure that penetrates the two-phase material during the subsequent curing process. This cross-scale bonding mechanism not only significantly improves the interlayer bonding strength (30% to 50% higher than that of a non-porous structure), but also optimizes the interfacial stress transfer efficiency through the chemical bonding of the resin-skeleton, thereby ensuring the structural integrity of the composite pressure vessel under high-pressure conditions.

[0055] In an exemplary embodiment, the compressive strength of the printed layer is greater than the winding pressure of the prepreg fiber (typically 0.5-3MPa). This mechanical property ensures that during the fiber winding stage, the printed layer can stably bear the winding tension and the lateral stress generated by the resin curing shrinkage, avoiding plastic deformation or structural collapse, thereby ensuring the geometric accuracy and interface bonding quality of the winding layer. The compressive strength of the printed layer can be optimized through material design and process, so that its compressive strength threshold is significantly higher than the prepreg fiber winding pressure. For example, through 3D printing path planning, the fibers are oriented along the main stress direction to improve the axial compressive strength. The thickness of the printed layer accounts for 1% to 5% of the fiber reinforced layer, which can meet the requirements.

[0056] In an exemplary embodiment, the prepreg fiber is a second fiber impregnated with a second resin. The second fiber may be of the same or different type as the first fiber. The second resin may be a thermoplastic resin or a thermosetting resin, and its peak curing temperature must be at least 30°C lower than the melting point of the first thermoplastic resin to ensure that the second resin does not affect the accuracy of the printed layer when molten. Preferably, the second resin is a thermosetting resin. Thermosetting resins have a high elastic modulus and a low thermal expansion coefficient, and do not undergo phase change after curing. Compared to thermoplastic resins, they are more suitable for scenarios requiring high temperature, high pressure, long-term loads, and high-precision dimensions. Exemplarily, the thermosetting resin is one of epoxy resin, bismaleimide, and phenolic resin. Epoxy resins with a high elastic modulus are preferred.

[0057] In an exemplary embodiment, the printing layer is T700 carbon fiber + PP resin, and the winding layer is T700 carbon fiber + epoxy resin.

[0058] In an exemplary embodiment, the wrapped layer is cured and composited with the printed layer to form a fiber-reinforced structure, with the printed layer thickness accounting for 1% to 5% of the total thickness of the fiber-reinforced structure. The curing process utilizes a gradient heating mode, with the hot pressing temperature controlled at 20-30°C above the resin melting point and the holding pressure maintained within a range of 0.5-2.0 MPa.

[0059] In an exemplary embodiment, the front joint and the rear joint are tightly connected to the positioning shaft to achieve axial fixation and circumferential limiting connection. Figure 2 As shown, the positioning shaft is I-shaped, consisting of two parallel flanges and a long axis located between them and perpendicular to them. The front / rear joint is formed by a neck and shoulder integrally formed: the neck is cylindrical; the shoulder is disc-shaped with an arcuate outer surface; and the inner cavity has a stepped surface. The stepped surface of the inner cavity of the front / rear joint abuts against the inner end surfaces of the two flanges and is fixed by positioning bolts (not shown). Multiple positioning bolts parallel to the long axis penetrate the flanges and are inserted into the stepped surface of the front joint or rear joint, achieving a tight connection between the front joint and the rear joint and the flanges, thereby achieving axial fixation and circumferential limitation of the front joint and rear joint.

[0060] In an exemplary embodiment, forming a printing layer between the front / rear joint specifically includes: Figure 2 As shown, the fiber-reinforced thermoplastic composite material filament is welded at the connection between the front / rear joint neck and the shoulder. After the printing is completed on the outer surface of the shoulder, the printing of the part between the front / rear joint shoulders is continued.

[0061] In an exemplary embodiment, as Figure 3 As shown, the horizontal rotating bracket is equipped with two sets of horizontal rotating shafts, which are coaxially connected to the two ends of the positioning shaft. The positioning shafts are synchronously driven by servo motors to rotate about their axes. The rotating shafts and the positioning shafts can be positioned and limited by positioning bolts or keyways (not shown).

[0062] In an exemplary embodiment, the composite pressure vessel has an operating pressure greater than 5 MPa. For example, the composite pressure vessel is a high-pressure hydrogen storage tank for a hydrogen fuel cell vehicle, a rocket propellant tank, a satellite pressure vessel, or a high-pressure gas storage and transport container.

[0063] In an exemplary embodiment, the outer surface of the printed layer is subjected to plasma treatment before winding the prepreg fibers. After the plasma treatment, the prepreg fiber winding process must be completed within 2 hours and maintained for 10 hours with a vacuum degassing device. -3 ~10 -2 Pa vacuum environment for interface activation.

[0064] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A composite pressure vessel forming method, characterized in that: include: The front joint and the rear joint are rigidly connected to both ends of the positioning shaft to form a support frame; The support frame is fixed vertically, and the 3D printer is driven to extrude fiber-reinforced thermoplastic composite material filament along the circumference of the positioning axis to form a printing layer between the front and rear joints; The support frame with the printed layer is horizontally mounted on the horizontal rotating bracket, and the positioning shaft is driven to rotate and the prepreg fiber is wound around the outer surface of the printed layer to form a winding layer; After the front / rear skirts are installed and cured to form an integral structure, the horizontal rotating bracket and positioning shaft are finally removed.

2. The composite pressure vessel forming method according to claim 1, characterized in that: The fiber-reinforced thermoplastic composite material filament is a filament composed of a first fiber and a first thermoplastic resin; wherein: The first fiber is one or a mixed fiber of carbon fiber, modified carbon fiber, quartz fiber, boron fiber, glass fiber, ceramic fiber, basalt fiber, alloy fiber; and / or, The carbon fiber is a blend of two or more of T700 and T800; and / or, The first thermoplastic resin is one of PA, PP, PEEK, PEKK, PPS, PEI, PEEK-HT, PA12, PBT, PET, TPU, and PCL.

3. The composite pressure vessel forming method according to claim 1, characterized in that: The printed layer is a spiral layer; and / or, The porosity of the printed layer is 0.5% to 0.75%; and / or, The pressure-bearing strength of the printed layer is greater than the winding pressure of the prepreg fibers.

4. The composite pressure vessel forming method according to claim 1, wherein: After solidification, the winding layer forms a fiber-reinforced layer with the printed layer.

5. The composite pressure vessel forming method according to claim 4, characterized in that: The prepreg fibers are second fibers impregnated with a second resin; and / or, The second resin is a thermoplastic resin or a thermosetting resin, and its curing peak temperature is at least 30° C. lower than the melting point of the first thermoplastic resin; and / or, The thickness of the printed layer accounts for 1% to 5% of the fiber reinforced layer.

6. The composite pressure vessel forming method according to claim 5, characterized in that: The second resin is a thermosetting resin; and / or, The thermosetting resin is one of epoxy resin, bismaleimide and phenolic resin; and / or, The curing temperature of the thermosetting resin is 60-160°C.

7. The composite pressure vessel forming method according to claim 1, characterized in that: The front joint and the rear joint are tightly connected to the positioning shaft to achieve axial fixation and circumferential limiting connection.

8. The composite pressure vessel forming method according to claim 1, characterized in that: The horizontal rotating bracket is provided with two sets of horizontal rotating shafts, which are coaxially connected to the two ends of the positioning shaft respectively, and the positioning shaft is synchronously driven by a servo motor to rotate around its axis.

9. The composite pressure vessel forming method according to claim 1, characterized in that: The working pressure of the composite material pressure vessel is greater than 5 MPa.

10. The composite pressure vessel forming method according to claim 1, characterized in that: Before winding the prepreg fibers, the outer surface of the printed layer is subjected to plasma treatment.

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