A recyclable and repairable V-shaped carbon fiber full-winding gas cylinder without inner liner and a method thereof

Abstract

The present application relates to gas cylinder technical field, specifically disclose a kind of recyclable repairable V-shaped inner bag-free carbon fiber full-winding gas cylinder and its preparation method, recycling method.The gas cylinder is inner bag-free full-winding structure, preparation stage is formed with water-soluble sand core mold composite forming support by retractable umbrella-shaped metal framework, after forming, the main body of bottle is that thermoplastic resin infiltrates carbon fiber and is formed carbon fiber winding layer by winding, heat setting;Its preparation method includes framework assembly, sand core mold preparation, fiber winding, integral heat setting, sand core mold removal step in sequence, while supporting design gas cylinder matrix damage repair process and overall recycling process.The present application effectively solves the problem of poor combination of traditional inner bag-free gas cylinder core mold and framework, significantly improves the hydrogen storage efficiency, structural strength and service life of gas cylinder, realizes the integration design of gas cylinder forming, repair and recycling, preparation process is flexible, environmental protection is good, suitable for 70MPa and above high-pressure hydrogen storage, especially suitable for hydrogen fuel cell vehicle on-board hydrogen storage.

Description

Technical Field

[0001] This invention relates to the field of gas storage cylinder technology, and more specifically, to a recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder and method, which is suitable for the storage of high-pressure hydrogen, natural gas and other gases, and is particularly suitable for the field of on-board hydrogen storage in 70MPa hydrogen fuel cell vehicles. Background Technology

[0002] Gas cylinders are key core equipment in fields such as new energy vehicles, chemical storage and transportation, and aerospace. Among them, the linerless carbon fiber fully wound gas cylinder (V-type cylinder) has significant advantages such as small weight-volume ratio, high hydrogen storage density, excellent structural strength, and lightweight due to the elimination of the traditional metal / non-metal liner structure, and has become the mainstream development trend in the field of high-pressure gas storage.

[0003] Currently, there are reports on the preparation technology of linerless gas cylinders both domestically and internationally. For example, CN114368171A discloses a method for preparing a linerless high-pressure gas cylinder, which uses a removable liner and wraps thermoplastic carbon fiber unidirectional tape around its outer surface, then removes the liner after curing. The octagonal support structure is a deformable skeleton liner, but its contact area with the mandrel is small, making it prone to mandrel deformation or displacement during winding. Furthermore, this method does not address cylinder damage repair or material recycling. CN117584506A discloses a V-shaped hydrogen storage cylinder and its preparation method, which uses a water-soluble core material to mold a water-soluble liner, coats the inside and outside of the liner with gel coat, then winds carbon fiber, and finally dissolves the liner with water after curing. Although this method uses a water-soluble liner, it lacks a metal skeleton support, the sand mandrel has insufficient strength, and it is prone to breakage during high-tension winding; moreover, it uses thermosetting epoxy resin as the matrix, making it impossible to repair the cylinder after damage and difficult to recycle after disposal. CN117656523A discloses a manufacturing process for a V-shaped hydrogen storage cylinder, using a cryogenic alloy to create a fusible inner liner. After solidification, the inner liner is removed by high-temperature melting, and pressure curing is assisted by soft materials. This method requires a high-temperature melting inner liner with a melting point higher than that of the cryogenic alloy, which can cause thermal damage to the carbon fiber composite material; furthermore, it does not provide a complete solution for repair and recycling. CN106979455A discloses a lightweight, long-life composite hydrogen cylinder, using a carbon fiber cylinder body and a replaceable non-metallic elastic inner liner (F46), but the inner liner is an independent component, not a linerless structure, and does not involve the repair and recycling of the thermoplastic resin matrix.

[0004] Currently, the preparation of linerless carbon fiber gas cylinders mostly uses water-soluble core molds, sand core molds, or deformable skeletons as forming supports. After carbon fiber is wound and cured, the core mold is removed to obtain the finished product. However, existing technologies still have many technical defects that are difficult to solve:

[0005] 1. Traditional straight-tube frame has a small contact area with the core mold, poor core mold adhesion and insufficient structural strength. During the carbon fiber winding process, the core mold is prone to deformation and displacement, which seriously affects the forming accuracy of the gas cylinder. 2. During the demolding process, it is difficult to separate the core mold from the skeleton. Some core mold materials are not completely removed, and the residual substances affect the gas cylinder's gas storage sealing and performance. 3. Most existing linerless gas cylinders use thermosetting resin as the matrix. When the carbon fiber winding layer is damaged, such as microcracks, resin shedding, or local fiber breakage, there is a lack of convenient and effective repair methods. Even minor damage can lead to the scrapping of the entire cylinder, significantly reducing its service life. 4. After the gas cylinders are scrapped, the composite material formed by carbon fiber and resin is difficult to separate effectively, and most of the material is directly discarded, causing serious waste of resources and environmental problems. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies, such as poor bonding between the core mold and the skeleton of linerless gas cylinders, difficulty in demolding, difficulty in repairing damage, and low recycling rate of waste materials. This invention provides a recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder and its method, along with a gas cylinder substrate damage repair method and recycling method, thereby achieving a comprehensive improvement in the gas cylinder's structural strength, molding convenience, repair operability, and resource utilization.

[0007] The technical means employed in this invention are as follows: In a first aspect, this invention discloses a recyclable and repairable V-shaped linerless carbon fiber fully wound gas cylinder. This gas cylinder is a linerless fully wound structure. During its fabrication, it relies on a retractable umbrella-shaped metal skeleton and a water-soluble sand core mold to form a composite molding support. After molding, the main body of the gas cylinder is a carbon fiber wound layer formed by thermoplastic resin and carbon fiber composite. The retractable umbrella-shaped metal skeleton is an openable stainless steel structure that can be radially contracted and axially expanded. Its outer surface is in close contact with the inner surface of the water-soluble sand core mold, providing radial and axial structural support to the sand core mold during the winding process. Furthermore, this metal skeleton is reusable. After unfolding, it forms an umbrella-shaped support that precisely matches the inner cavity of the V-shaped gas cylinder. Compared to traditional straight-cylinder skeletons, this significantly increases the contact area with the water-soluble sand core mold, resulting in a stronger adhesion and higher structural strength. The skeleton can freely contract and expand, making insertion and removal convenient during demolding and repair. It can also be reused after cleaning and testing.

[0008] Furthermore, the retractable umbrella-shaped metal frame consists of 6 to 12 umbrella ribs, a fixing device, and two sets of moving devices. The fixing device is fixedly installed in the middle of the spindle, and the two sets of moving devices are located on both sides of the fixing device. The two ends of the spindle are threaded, and the moving devices are connected to the spindle through trapezoidal threads. One end of each umbrella rib is hinged to the fixing device, and the other end is hinged to the moving device on the corresponding side. Each umbrella rib consists of two branch ribs, and the two branch ribs are also connected by hinges. The umbrella ribs, fixing device, and moving devices together constitute a synchronous linkage mechanism.

[0009] Furthermore, the water-soluble sand core mold is made of water-soluble sand core material through molding and stepped curing. Its structure is precisely matched with the inner cavity of the V-shaped gas cylinder, providing stable forming support for carbon fiber winding. The sand core mold can be completely dissolved and removed by water rinsing, leaving no residue after dissolution and not affecting the gas cylinder's gas storage sealing and performance. The sand core material is composed of water-soluble adhesive, glass microspheres of different mesh sizes, and chopped glass fibers, balancing the structural strength and water solubility of the sand core mold, effectively avoiding problems such as deformation and sand shedding during the winding process. The carbon fiber winding layer is the core load-bearing structure of the gas cylinder. It is made of T700 grade and above high-strength carbon fiber, which is fully impregnated with thermoplastic resin and then made by a combination of longitudinal spiral winding and circumferential alternating winding on the outside of a water-soluble sand core mold. The number of winding layers can be flexibly adjusted according to the design pressure requirements of the gas cylinder. The selection of thermoplastic resin enables the gas cylinder to have the basis for melt repair and material recycling. The optimization of the winding method further improves the gas cylinder's resistance to high pressure and fatigue.

[0010] Secondly, this invention discloses a method for preparing the aforementioned recyclable and repairable V-shaped linerless carbon fiber fully wound gas cylinder, specifically including the following steps: S1: The retractable umbrella-shaped metal frame is unfolded to a preset shape, and the opening and closing state is fixed by the frame's own locking structure, forming a stable support frame whose size matches the inner cavity of the gas cylinder to be prepared. S2: Water-soluble sand core raw materials are mixed in proportion to obtain sand core material. The sand core material is made into a water-soluble sand core mold that matches the inner cavity structure of the V-shaped gas cylinder using a molding process. The surface of the sand core mold is smooth and free from defects such as sand shedding, cracking, and missing corners, and the surface is coated with a release medium layer. S3: After the carbon fiber is fully impregnated with thermoplastic resin, it is wound on the outside of the water-soluble sand core mold using a winding equipment. The winding is carried out using alternating longitudinal spiral winding and circumferential winding until the designed number of layers are formed to form a carbon fiber winding layer. The winding tension is strictly controlled between 30 and 80 N, and the tension fluctuation throughout the process does not exceed ±5%. S4: Place the wound gas cylinder blank in a heating furnace and heat it to between the melting temperature and degradation temperature of the corresponding thermoplastic resin. Maintain the temperature at a constant temperature until the resin is fully melted and impregnated. Then, cool and shape it at a rate of 5~10℃ / min to obtain a semi-finished gas cylinder with a skeleton and a water-soluble sand core mold. Specifically, the heating temperature is adjusted according to the type of thermoplastic resin selected. The gas cylinder blank is heated to between the melting temperature and the thermal degradation temperature and then kept at a constant temperature until the thermoplastic resin is fully melted and the fiber is uniformly impregnated. During the heat setting process, the gas cylinder blank is kept in a vertical position and the temperature fluctuation in the heating furnace does not exceed ±2℃ to ensure uniform resin melting and consistent cooling and setting, and to avoid local overheating degradation, insufficient impregnation or cooling stress defects.

[0011] S5: Unlock the retractable umbrella-shaped metal frame and remove it from the cylinder mouth of the semi-finished gas cylinder. Then, inject water into the inner cavity of the semi-finished gas cylinder through the cylinder mouth to dissolve the water-soluble sand core mold. Export the dissolved sand core solution from the cylinder mouth. After cleaning and drying the inner cavity of the gas cylinder in sequence, a recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder is obtained.

[0012] Further, in step S2, the water-soluble core material is composed of a water-soluble adhesive, glass microspheres of different mesh sizes, and chopped glass fibers; the water-soluble adhesive is a compound of polyvinyl alcohol, dimethyl sulfoxide, and polyvinylpyrrolidone, and the core material is formed after mixing, compaction, and step curing.

[0013] Further, in step S2, the glass microspheres of different mesh sizes are 40 mesh, 100 mesh, and 400 mesh glass microspheres, and the chopped glass fibers have a diameter of 7~13μm and their surfaces are pretreated with a silane coupling agent; the mixing mass ratio of 40 mesh, 100 mesh, and 400 mesh glass microspheres to chopped glass fibers is (2... 5):(4 6):(1 4):(1 3) The mixing mass ratio of the mixed filler to the water-soluble adhesive is 50:7; the stepped curing process is 100℃ / 3h→120℃ / 3h→100℃ / 3h.

[0014] Furthermore, in step S3, the thermoplastic resin is one of ABS, PLA, nylon, PPS, and PEEK, the tension fluctuation of the impregnated carbon fiber winding is ≤±5%, and the winding angle is optimized according to the structural characteristics of the V-shaped gas cylinder.

[0015] The release medium layer is selected from one or more of polyvinyl alcohol (PVA) aqueous solution, polyethylene glycol (PEG) or water-soluble silicone oil, with a coating thickness of 10~20μm. It is completely water-soluble with no residue and does not affect the sealing performance.

[0016] Furthermore, in step S4, the gas cylinder blank is kept vertical during the heat setting process, and the temperature fluctuation in the heating furnace does not exceed ±2℃.

[0017] Thirdly, the present invention also discloses a method for repairing matrix damage of the above-mentioned recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder, comprising the following steps: R1: Use non-destructive testing equipment to detect the location, depth and extent of damage to the carbon fiber winding layer of the gas cylinder, mark the damaged area, and use compressed air to clean the impurities in the damaged area. R2: After unfolding the retractable umbrella-shaped metal frame, insert it into the inner cavity of the gas cylinder so that the frame is precisely aligned with the damaged area. Fill the corresponding position of the damaged area of ​​the gas cylinder with water-soluble sand core material on the outside of the frame. After pressurization, cooling and shaping, a rigid support body matching the shape and size of the damaged area is formed. R3: Place the gas cylinder in a heating furnace and heat it to the melting temperature of the thermoplastic resin in the cylinder body to soften the resin in the damaged area. Depending on the degree of damage, repair the matrix damage by either pressurizing or wrapping with thermoplastic resin-impregnated carbon fiber. After repair, cool and set the resin at a rate of 3~5℃ / min to allow the resin to reform. R4: After the gas cylinder cools to room temperature, shrink the retractable umbrella-shaped metal frame and remove it from the gas cylinder mouth. Inject water into the gas cylinder cavity to dissolve the water-soluble sand core mold. After exporting the sand core solution, clean and dry the gas cylinder cavity to complete the repair of the gas cylinder base damage.

[0018] Fourthly, this invention also discloses a recycling method for a recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder, which includes the following steps when the gas cylinder fails to meet usage requirements: H1: Place the scrapped gas cylinder in a heating furnace and heat it to the melting temperature of the thermoplastic resin in the cylinder. Maintain the temperature until the resin softens completely and loses its bonding force to the carbon fiber. H2: The softened thermoplastic resin is separated from the carbon fiber using a physical peeling method, avoiding excessive damage to the carbon fiber during the separation process; H3: After the separated carbon fibers are cleaned and dried, they can be reused for fiber winding; after the softened thermoplastic resin is granulated, it can be used again as the matrix raw material for carbon fiber impregnation; the shrinkable umbrella-shaped metal skeleton can be directly reused after being cleaned and tested; after the raw materials of the water-soluble sand core mold are dissolved, they are filtered and dried, and then re-formulated into water-soluble sand core material for sand core mold preparation.

[0019] Compared with the prior art, the present invention has the following advantages: 1. Compared with the traditional straight cylindrical frame, the retractable umbrella-shaped metal skeleton significantly increases the contact area with the water-soluble sand core mold, resulting in a more secure adhesion to the sand core mold and higher structural strength. There are no core mold deformation or displacement issues during the carbon fiber winding process, ensuring the forming accuracy of the gas cylinder. The carbon fiber winding layer adopts a longitudinal spiral and circumferential alternating winding method, combined with T700 grade and above high-strength carbon fiber, further improving the gas cylinder's high pressure resistance and fatigue resistance, which can meet the requirements of high-pressure gas storage applications such as vehicle-mounted hydrogen storage.

[0020] 2. The retractable umbrella-shaped metal frame has an openable structure that can be freely retracted and expanded. When demolding, it can be quickly removed from the bottle mouth by shrinking, making the operation convenient. The water-soluble sand core mold can be completely dissolved and removed by rinsing with water, leaving no residue. This avoids the impact of core mold residue on the gas cylinder's gas storage sealing and performance. Furthermore, the sand core mold material can be recycled and reused.

[0021] 3. Design a targeted repair process for gas cylinder substrate damage. Utilize a shrinkable umbrella-shaped metal frame and water-soluble sand core mold to provide precise rigid support for the damaged area. Combined with the melting characteristics of thermoplastic resin, achieve efficient repair of the damaged area. This solves the technical problem of existing gas cylinders without inner liner being scrapped due to minor damage, and significantly improves the service life of the gas cylinder.

[0022] 4. Develop a complete gas cylinder recycling process to achieve full recycling and reuse of carbon fiber, thermoplastic resin, shrinkable umbrella-shaped metal frame, and water-soluble sand core mold raw materials, avoid material waste, reduce the cost of gas cylinders throughout their entire life cycle, and conform to the development concept of green and environmentally friendly industries.

[0023] 5. The number of carbon fiber winding layers, the type of thermoplastic resin, and the proportion of water-soluble sand core mold raw materials can all be flexibly adjusted according to the requirements of gas cylinder design pressure, operating temperature, etc., making it suitable for high-pressure gas storage needs of different specifications and application scenarios, especially suitable for hydrogen fuel cell vehicles on-board hydrogen storage, with broad industrialization prospects. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of a V-shaped support structure for a water-soluble sand core mold with a metal skeleton. Figure 2 This is a schematic diagram of the cross-sectional structure of the gas cylinder after it has been integrally formed. Figure 3 A flowchart for repairing damage to the gas cylinder substrate; Figure 4 This is a process flow diagram for the preparation of gas cylinders.

[0026] In the diagram: 1. Core mold; 2. Mandrel; 3. Umbrella rib; 4. Fixing device; 5. Moving device; 6. Hinge shaft. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0030] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0031] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0032] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0033] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0034] This invention discloses a recyclable and repairable V-shaped linerless carbon fiber fully wound gas cylinder, such as... Figure 2 As shown, the gas cylinder is a linerless, fully wrapped structure, and its manufacturing process relies on... Figure 1 The collapsible umbrella-shaped metal skeleton and water-soluble sand core mold shown form a composite molding support. After molding, the main body of the gas cylinder is a carbon fiber winding layer formed by thermoplastic resin and carbon fiber composite. The collapsible umbrella-shaped metal skeleton is an openable stainless steel structure that can be radially contracted and axially expanded. Its outer surface is in close contact with the inner surface of the water-soluble sand core mold, which is used to provide radial and axial structural support for the sand core mold during the winding process. The metal skeleton can be reused. After unfolding, it forms an umbrella-shaped support that precisely matches the inner cavity of the V-shaped gas cylinder. Compared with the traditional straight cylindrical skeleton, it greatly increases the contact area with the water-soluble sand core mold, making the sand core mold adhere more firmly and the structural strength higher. The skeleton can be freely contracted and unfolded, and the insertion and removal operations are convenient during demolding and repair. It can also be reused after cleaning and testing.

[0035] Furthermore, the retractable umbrella-shaped metal frame consists of 6 to 12 umbrella ribs, a fixing device, and two sets of moving devices. The fixing device is fixedly installed in the middle of the spindle, and the two sets of moving devices are located on both sides of the fixing device. The two ends of the spindle are threaded, and the moving devices are connected to the spindle through trapezoidal threads. One end of each umbrella rib is hinged to the fixing device, and the other end is hinged to the moving device on the corresponding side. Each umbrella rib consists of two branch ribs, and the two branch ribs are also connected by hinges. The umbrella ribs, fixing device, and moving devices together constitute a synchronous linkage mechanism.

[0036] All hinge pins are built into the supports of both the fixed and moving devices.

[0037] Optionally, after the moving device 5 is rotated to the predetermined position, it can be locked a second time by the locking nut at the end of the spindle 2. Also, optionally, the fixing device 4 is provided with a radial spring pin, which automatically engages with the positioning hole of the umbrella rib 3 when the umbrella rib 3 is fully unfolded.

[0038] When the moving device is screwed in, it moves towards the fixed device along the mandrel axis, driving all the umbrella ribs to simultaneously expand radially outward through the hinge structure, forming a uniform clamping force with the inner wall of the water-soluble sand core mold. This clamping force acts in the opposite direction on the moving device, causing the trapezoidal thread pair to produce a mechanical self-locking effect, ensuring that the moving device will not retract under force during the molding process. When the moving device is screwed out in the opposite direction, it moves away from the fixed device along the mandrel axis, driving all the umbrella ribs to simultaneously retract radially inward. After retraction, the overall outer diameter is smaller than the diameter of the sand core mold bottle mouth, facilitating demolding, maintenance, and reuse. Furthermore, the water-soluble sand core mold is made of water-soluble sand core material through molding and stepped curing. Its structure is precisely matched with the inner cavity of the V-shaped gas cylinder, providing stable forming support for carbon fiber winding. The sand core mold can be completely dissolved and removed by water rinsing, leaving no residue after dissolution and not affecting the gas cylinder's gas storage sealing and performance. The sand core material is composed of water-soluble adhesive, glass microspheres of different mesh sizes, and chopped glass fibers, balancing the structural strength and water solubility of the sand core mold, effectively avoiding problems such as deformation and sand shedding during the winding process. The carbon fiber winding layer is the core load-bearing structure of the gas cylinder. It is made of T700 grade and above high-strength carbon fiber, which is fully impregnated with thermoplastic resin and then made by a combination of longitudinal spiral winding and circumferential alternating winding on the outside of a water-soluble sand core mold. The number of winding layers can be flexibly adjusted according to the design pressure requirements of the gas cylinder. The selection of thermoplastic resin enables the gas cylinder to have the basis for melt repair and material recycling. The optimization of the winding method further improves the gas cylinder's resistance to high pressure and fatigue.

[0039] This invention discloses a method for preparing the above-mentioned recyclable and repairable V-shaped linerless carbon fiber fully wound gas cylinder, specifically including the following steps: S1: The retractable umbrella-shaped metal frame is unfolded to a preset shape, and the opening and closing state is fixed by the frame's own locking structure, forming a stable support frame whose size matches the inner cavity of the gas cylinder to be prepared. S2: Water-soluble sand core raw materials are mixed in proportion to obtain sand core material. The sand core material is made into a water-soluble sand core mold that matches the inner cavity structure of the V-shaped gas cylinder using a molding process. The surface of the sand core mold is smooth and free from defects such as sand shedding, cracking, and missing corners, and the surface is coated with a release medium layer. S3: After the carbon fiber is fully impregnated with thermoplastic resin, it is wound on the outside of the water-soluble sand core mold using a winding equipment. The winding is carried out using alternating longitudinal spiral winding and circumferential winding until the designed number of layers are formed to form a carbon fiber winding layer. The winding tension is strictly controlled between 30 and 80 N, and the tension fluctuation throughout the process does not exceed ±5%. S4: Place the wound gas cylinder blank in a heating furnace and heat it to between the melting temperature and degradation temperature of the corresponding thermoplastic resin. Maintain the temperature at a constant temperature until the resin is fully melted and impregnated. Then, cool and shape it at a rate of 5~10℃ / min to obtain a semi-finished gas cylinder with a skeleton and a water-soluble sand core mold. Specifically, the heating temperature is adjusted according to the type of thermoplastic resin selected. The gas cylinder blank is heated to between the melting temperature and the thermal degradation temperature and then kept at a constant temperature until the thermoplastic resin is fully melted and the fiber is uniformly impregnated. During the heat setting process, the gas cylinder blank is kept in a vertical position and the temperature fluctuation in the heating furnace does not exceed ±2℃ to ensure uniform resin melting and consistent cooling and setting, and to avoid local overheating degradation, insufficient impregnation or cooling stress defects.

[0040] S5: Unlock the retractable umbrella-shaped metal frame and remove it from the cylinder mouth of the semi-finished gas cylinder. Then, inject water into the inner cavity of the semi-finished gas cylinder through the cylinder mouth to dissolve the water-soluble sand core mold. Export the dissolved sand core solution from the cylinder mouth. After cleaning and drying the inner cavity of the gas cylinder in sequence, a recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder is obtained.

[0041] Further, in step S2, the water-soluble core material is composed of a water-soluble adhesive, glass microspheres of different mesh sizes, and chopped glass fibers; the water-soluble adhesive is a compound of polyvinyl alcohol, dimethyl sulfoxide, and polyvinylpyrrolidone, and the core material is formed after mixing, compaction, and step curing.

[0042] In this embodiment, the water-soluble adhesive is a compound of polyvinyl alcohol, dimethyl sulfoxide, and polyvinylpyrrolidone, with a mass ratio of (10-20):(70-85):(5-10). Preferably, the mass ratio is 15:80:5. The preparation method is as follows: first, polyvinyl alcohol and dimethyl sulfoxide are mixed, heated and stirred at 80-100°C until completely dissolved, then cooled to 40-60°C and polyvinylpyrrolidone is added, stirred until uniform and transparent, thus obtaining the water-soluble adhesive.

[0043] Further, in step S2, the glass microspheres of different mesh sizes are 40 mesh, 100 mesh, and 400 mesh glass microspheres, and the chopped glass fibers have a diameter of 7~13μm and their surfaces are pretreated with a silane coupling agent; the mixing mass ratio of 40 mesh, 100 mesh, and 400 mesh glass microspheres to chopped glass fibers is (2... 5):(4 6):(1 4):(1 3) The mixing mass ratio of the mixed filler to the water-soluble adhesive is 50:7; the stepped curing process is 100℃ / 3h→120℃ / 3h→100℃ / 3h.

[0044] Furthermore, in step S3, the thermoplastic resin is one of ABS, PLA, nylon, PPS, and PEEK, the tension fluctuation of the impregnated carbon fiber winding is ≤±5%, and the winding angle is optimized according to the structural characteristics of the V-shaped gas cylinder.

[0045] The release medium layer is selected from one or more of polyethylene wax emulsion, polytetrafluoroethylene emulsion, and stearic acid emulsion. The coating thickness is 10–20 μm. It is completely water-soluble with no residue and does not affect the sealing performance.

[0046] Furthermore, in step S4, the gas cylinder blank is kept vertical during the heat setting process, and the temperature fluctuation in the heating furnace does not exceed ±2℃.

[0047] like Figure 3 As shown, the present invention also discloses a method for repairing matrix damage of the above-mentioned recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder, comprising the following steps: R1: Use non-destructive testing equipment to detect the location, depth and extent of damage to the carbon fiber winding layer of the gas cylinder, mark the damaged area, and use compressed air to clean the impurities in the damaged area. R2: After unfolding the retractable umbrella-shaped metal frame, insert it into the inner cavity of the gas cylinder so that the frame is precisely aligned with the damaged area. Fill the corresponding position of the damaged area of ​​the gas cylinder with water-soluble sand core material on the outside of the frame. After pressurization, cooling and shaping, a rigid support body matching the shape and size of the damaged area is formed. R3: Place the gas cylinder in a heating furnace and heat it to the melting temperature of the thermoplastic resin in the cylinder body to soften the resin in the damaged area. Depending on the degree of damage, repair the matrix damage by either pressurizing or wrapping with thermoplastic resin-impregnated carbon fiber. After repair, cool and set the resin at a rate of 3~5℃ / min to allow the resin to reform. R4: After the gas cylinder cools to room temperature, shrink the retractable umbrella-shaped metal frame and remove it from the gas cylinder mouth. Inject water into the gas cylinder cavity to dissolve the water-soluble sand core mold. After exporting the sand core solution, clean and dry the gas cylinder cavity to complete the repair of the gas cylinder base damage.

[0048] like Figure 4 As shown, this invention also discloses a recycling method for a recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder, which includes the following steps when the gas cylinder fails to meet usage requirements: H1: Place the scrapped gas cylinder in a heating furnace and heat it to the melting temperature of the thermoplastic resin in the cylinder. Maintain the temperature until the resin softens completely and loses its bonding force to the carbon fiber. H2: The softened thermoplastic resin is separated from the carbon fiber using a physical peeling method, avoiding excessive damage to the carbon fiber during the separation process; H3: After the separated carbon fibers are cleaned and dried, they can be reused for fiber winding; after the softened thermoplastic resin is granulated, it can be used again as the matrix raw material for carbon fiber impregnation; the shrinkable umbrella-shaped metal skeleton can be directly reused after being cleaned and tested; after the raw materials of the water-soluble sand core mold are dissolved, they are filtered and dried, and then re-formulated into water-soluble sand core material for sand core mold preparation.

[0049] Example 1: Preparation of a 70MPa V-type linerless carbon fiber fully wound gas cylinder Step 1. Assembly of retractable umbrella-shaped metal frame: unfold the retractable umbrella-shaped metal frame made of stainless steel to the preset shape, with a cylinder section radius of 180mm and a single-side end cap height of 360mm. After being fixed by the locking structure, a stable support frame is formed. Step 2. Preparation of water-soluble sand core mold: A water-soluble adhesive composed of polyvinyl alcohol, dimethyl sulfoxide, and polyvinylpyrrolidone is mixed with 40-mesh / 100-mesh / 400-mesh glass microspheres and short-cut glass fibers (7 μm in diameter) pretreated with silane coupling agent at a mass ratio of 2:4:1:1 (the ratio of mixed filler to adhesive is 50:7) to prepare a sand core material; the sand core material is pressed into a core mold and cured in a stepped manner at 100℃ / 3h→120℃ / 3h→100℃ / 3h. After demolding, a V-shaped water-soluble sand core mold matching the skeleton is obtained. The surface of the sand core mold is coated with a polyethylene wax emulsion release medium layer; Step 3. Thermoplastic resin Carbon fiber winding: T700 carbon fiber is selected and fully impregnated with nylon resin. It is wound in a longitudinal spiral winding (winding angle 55°) and circumferential winding (winding angle 90°) alternating manner on the outside of the sand core mold to form a carbon fiber winding layer of 20 layers; the carbon fiber winding tension is controlled at 50N.

[0050] Step 4. Overall heat setting: Place the gas cylinder blank in a heating furnace and heat it to 240℃. Maintain the temperature for 3 hours to allow the resin to fully melt and impregnate the carbon fiber. Control the temperature fluctuation in the heating furnace within ±1℃. Then cool and set the shape at a rate of 8℃ / min. Step 5. Removal of water-soluble sand core mold: Shrink the metal skeleton and remove it from the bottle mouth. Continuously inject water into the inner cavity of the gas cylinder through the bottle mouth to dissolve the sand core mold. After exporting the sand core solution, blow the inner cavity dry with compressed air to obtain the finished 70MPa V-type linerless carbon fiber fully wound gas cylinder.

[0051] Example 2: Preparation of a 70MPa V-type linerless carbon fiber fully wound gas cylinder Step 1. Assemble the retractable umbrella-shaped metal frame: Same as in Example 1; Step 2. Preparation of water-soluble sand core mold: Mix water-soluble adhesive with 40 mesh / 100 mesh / 400 mesh glass microspheres and chopped glass fibers (10 μm in diameter) at a mass ratio of 3:5:2:2 to obtain the sand core material; the remaining steps are the same as in Example 1; Step 3. Thermoplastic resin carbon fiber winding: Same as in Example 1; Step 4. Overall heat setting: Same as in Example 1; Step 5. Removal of water-soluble sand core mold: Same as in Example 1.

[0052] Example 3: Preparation of a 70MPa V-type linerless carbon fiber fully wound gas cylinder Step 1. Assemble the retractable umbrella-shaped metal frame: Same as in Example 1; Step 2. Preparation of water-soluble sand core mold: Mix water-soluble adhesive with 40 mesh / 100 mesh / 400 mesh glass microspheres and chopped glass fibers (13 μm in diameter) at a mass ratio of 5:6:4:3 to obtain the sand core material; the remaining steps are the same as in Example 1; Step 3. Thermoplastic resin carbon fiber winding: Same as in Example 1; Step 4. Overall heat setting: Same as in Example 1; Step 5. Removal of water-soluble sand core mold: Same as in Example 1.

[0053] Example 4 Repairing microcracks in the gas cylinder substrate includes the following steps: Ultrasonic testing revealed a microcrack 50 mm long and 0.5 mm deep in the cylinder body. After marking the cracked area, impurities were removed by blowing away the crack with compressed air. The retractable umbrella-shaped metal frame is unfolded and inserted into the inner cavity of the gas cylinder, so that the frame is precisely aligned with the crack area. Water-soluble sand core material is filled on the outside of the frame, and the frame is pressurized, cooled and shaped to form a rigid support. The gas cylinder is heated to the melting temperature of nylon resin, 220℃. A pressure of 0.3MPa is applied to the cracked area to allow the softened resin to fully fill the crack. After maintaining the temperature for 1 hour, the temperature is slowly lowered at 3–5℃ / min to cool and solidify the resin, allowing it to reshape and restore the structural strength. Shrink the metal frame and remove it from the bottle mouth. Pour water into the inner cavity of the gas cylinder to dissolve the sand core mold. After the solution is discharged, use compressed air to dry the inner cavity to complete the repair. After repair, the gas cylinder is tested and can withstand a pressure of 70MPa, restoring its original performance.

[0054] Example 5 The disposal and recycling of gas cylinders includes the following steps: Place the scrapped 70MPa V-type gas cylinder in a heating furnace and heat it to 220℃, maintaining the temperature until the nylon resin is completely softened. Use flexible tools to physically separate carbon fiber from nylon resin, avoiding damage to the carbon fiber during the separation process; After separation, the carbon fibers retain more than 95% of their strength after cleaning and drying, and can be reused for fiber winding. Nylon resin can be used as a matrix material for carbon fiber impregnation after granulation. The stainless steel shrinkable umbrella-shaped metal skeleton has no deformation or strength loss after cleaning and testing, and can be directly reused for the preparation of new gas cylinders. The raw materials after the sand core mold is dissolved can be filtered and dried to be re-formulated into sand core materials for sand core mold molding.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A recyclable and repairable V-shaped linerless carbon fiber fully wound gas cylinder, characterized in that, The gas cylinder is a linerless, fully wound structure. During the manufacturing process, it relies on a retractable umbrella-shaped metal skeleton and a water-soluble sand core mold to form a composite molding support. After molding, the main body of the gas cylinder is a carbon fiber wound layer formed by thermoplastic resin and carbon fiber composite. The retractable umbrella-shaped metal skeleton is an openable support structure that can be radially contracted and axially expanded. Its outer surface is in contact with the inner surface of the water-soluble sand core mold, which is used to provide radial and axial structural support for the sand core mold during the winding process. Moreover, the metal skeleton can be reused.

2. The recyclable and repairable V-shaped linerless carbon fiber fully wound gas cylinder according to claim 1, characterized in that, The retractable umbrella-shaped metal frame consists of 6 to 12 umbrella ribs, a fixing device, and two sets of moving devices. The fixing device is fixedly installed in the middle of the spindle, and the two sets of moving devices are located on both sides of the fixing device. The two ends of the spindle are threaded, and the moving devices are connected to the spindle through trapezoidal threads. One end of each umbrella rib is hinged to the fixing device, and the other end is hinged to the moving device on the corresponding side. Each umbrella rib consists of two branch ribs, and the two branch ribs are also connected by hinges. The umbrella ribs, fixing device, and moving devices together constitute a synchronous linkage mechanism.

3. The recyclable and repairable V-shaped linerless carbon fiber fully wound gas cylinder according to claim 1, characterized in that, The water-soluble sand core mold is made by molding and step curing of water-soluble sand core material; The shape of the water-soluble sand core mold is adapted to the shape of the inner cavity of the V-shaped gas cylinder, and the water-soluble sand core mold is soluble in water; The carbon fiber winding layer is composed of high-strength carbon fiber of T700 grade and above and thermoplastic resin; the carbon fiber is wound on the outside of the water-soluble sand core mold in an alternating manner of longitudinal spiral winding and circumferential winding, with a winding tension of 30~80N, and the number of winding layers is set according to the design pressure.

4. A method for preparing a recyclable and repairable V-shaped linerless carbon fiber fully wound gas cylinder as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1: The retractable umbrella-shaped metal frame is unfolded to a preset shape, and the opening and closing state is fixed by the frame's own locking structure, forming a stable support frame whose size matches the inner cavity of the gas cylinder to be prepared. S2: Water-soluble sand core raw materials are mixed in proportion to obtain sand core material. The sand core material is made into a water-soluble sand core mold that matches the inner cavity structure of the V-shaped gas cylinder using a molding process. The surface of the sand core mold is smooth and free from defects such as sand shedding, cracking, and missing corners, and the surface is coated with a release medium layer. S3: After the carbon fiber is fully impregnated with thermoplastic resin, it is wound on the outside of the water-soluble sand core mold using a winding equipment. The winding is carried out in a longitudinal spiral winding and circumferential alternating winding manner until the designed number of layers are reached to form a carbon fiber winding layer. S4: Place the wound gas cylinder blank in a heating furnace and heat it to between the melting temperature and degradation temperature of the corresponding thermoplastic resin. Maintain the temperature at a constant temperature until the resin is fully melted and impregnated. Then, cool and shape it at a rate of 5~10℃ / min to obtain a semi-finished gas cylinder with a skeleton and a water-soluble sand core mold. S5: Unlock the retractable umbrella-shaped metal frame and remove it from the cylinder mouth of the semi-finished gas cylinder. Then, inject water into the inner cavity of the semi-finished gas cylinder through the cylinder mouth to dissolve the water-soluble sand core mold. Export the dissolved sand core solution from the cylinder mouth. After cleaning and drying the inner cavity of the gas cylinder in sequence, a recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder is obtained.

5. The preparation method according to claim 4, characterized in that, In step S2, the water-soluble core material is composed of water-soluble adhesive, glass microspheres of different mesh sizes, and chopped glass fibers; the water-soluble adhesive is a compound of polyvinyl alcohol, dimethyl sulfoxide, and polyvinylpyrrolidone, and the core material is formed after mixing, compaction, and step curing.

6. The preparation method according to claim 5, characterized in that, In step S2, the glass microspheres with different mesh sizes are 40 mesh, 100 mesh, and 400 mesh glass microspheres, and the diameter of the chopped glass fibers is 7 mm. 13μm and surface pretreated with silane coupling agent; the mixing mass ratio of 40 mesh, 100 mesh, and 400 mesh glass microspheres to chopped glass fibers is (2... 5):(4 6):(1 4):(1 3) The mixing mass ratio of the mixed filler to the water-soluble adhesive is 50:7; the stepped curing process is 100℃ / 3h→120℃ / 3h→100℃ / 3h.

7. The preparation method according to claim 4, characterized in that, In step S3, the thermoplastic resin is one of ABS, PLA, nylon, PPS, and PEEK. The tension fluctuation of the impregnated carbon fiber winding is ≤±5%, and the winding angle is optimized according to the structural characteristics of the V-shaped gas cylinder.

8. The preparation method according to claim 4, characterized in that, In step S4, the gas cylinder blank is kept vertical during the heat setting process, and the temperature fluctuation in the heating furnace does not exceed ±2℃.

9. A method for repairing matrix damage in a recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder as described in claim 1, characterized in that, Includes the following steps: R1: Non-destructive testing equipment is used to detect the location, depth and extent of damage to the carbon fiber winding layer of the gas cylinder, the damaged area is marked, and impurities in the damaged area are cleaned with compressed air. R2: After unfolding the retractable umbrella-shaped metal frame, insert it into the inner cavity of the gas cylinder so that the frame is precisely aligned with the damaged area. Fill the corresponding position of the damaged area of ​​the gas cylinder with water-soluble sand core material on the outside of the frame. After pressurization, cooling and shaping, a rigid support body matching the shape and size of the damaged area is formed. R3: Place the gas cylinder in a heating furnace and heat it to the melting temperature of the thermoplastic resin in the cylinder body to soften the resin in the damaged area. Depending on the degree of damage, repair the matrix damage by either pressurizing or wrapping with thermoplastic resin-impregnated carbon fiber. After repair, cool and set the resin at a rate of 3~5℃ / min to allow the resin to reform. R4: After the gas cylinder cools to room temperature, shrink the retractable umbrella-shaped metal frame and remove it from the gas cylinder mouth. Inject water into the gas cylinder cavity to dissolve the water-soluble sand core mold. After exporting the sand core solution, clean and dry the gas cylinder cavity to complete the repair of the gas cylinder base damage.

10. A method for recycling a recyclable and repairable V-shaped linerless carbon fiber fully wrapped gas cylinder as described in claim 1, characterized in that, When the gas cylinder fails to meet the usage requirements during testing Includes the following steps: H1: Place the scrapped gas cylinder in a heating furnace and heat it to the melting temperature of the thermoplastic resin in the cylinder. Maintain the temperature until the resin softens completely and loses its bonding force to the carbon fiber. H2: The softened thermoplastic resin is separated from the carbon fiber using a physical peeling method, avoiding excessive damage to the carbon fiber during the separation process; H3: After the separated carbon fibers are cleaned and dried, they can be reused for fiber winding; after the softened thermoplastic resin is granulated, it can be used again as the matrix raw material for carbon fiber impregnation; the shrinkable umbrella-shaped metal skeleton can be directly reused after being cleaned and tested; after the raw materials of the water-soluble sand core mold are dissolved, they are filtered and dried, and then re-formulated into water-soluble sand core material for sand core mold preparation.

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