Forming processing method of composite material gas cylinder

Abstract

The invention discloses a forming processing method of a composite material gas cylinder, which comprises the following steps of: positioning and embedding a pre-processed metal valve seat into a cavity of an injection mold, and performing high-pressure injection molding to form a lining pre-formed body wrapping the metal valve seat; and transferring the liner preform to blow molding equipment for blow molding integrated molding to prepare the gas cylinder liner which is integrated with the metal valve seat in a weldless manner, zero in interface gap and high in bonding strength. The method comprises the following steps: calculating laying parameters of a composite gas cylinder winding layer by adopting a grid theory on the basis of a dry-method prepreg yarn principle, and obtaining a laying layer design scheme; laying a carbon fiber winding layer on the outer surface of the gas cylinder lining subjected to surface treatment according to a laying design scheme based on a dry-method prepreg yarn winding technology; and the high-pressure composite material gas cylinder product is obtained through cooperative treatment of heating curing and mold pressing. The problems that the precision requirement of a traditional technology is difficult to meet and labor cost is high are solved.

Description

Technical Field

[0001] This invention relates to the field of composite material processing technology, and specifically to a molding and processing method for composite material gas cylinders. Background Technology

[0002] In the gas cylinder manufacturing process, the traditional method of injection molding followed by welding generally suffers from insufficient welding precision, resulting in a low yield. At the same time, the inner and outer surfaces of traditional metal valve seats are mostly smooth planes, with limited contact area with the plastic liner. The connection is achieved only through simple wrapping, resulting in a single bonding method, low interfacial shear strength, and difficulty in ensuring airtightness.

[0003] Furthermore, the traditional process adopts a step-by-step manufacturing mode of "split injection molding liner + post-welding". The split liner needs to be connected by welding process. This process is highly dependent on the operator's technical level. The positional deviation may be as high as ±1.5mm, which can easily lead to quality defects in the weld position. In addition, the weld surface has high roughness and poor flatness, and post-processing such as manual grinding or mechanical processing is required to meet the accuracy requirements, which significantly increases labor costs.

[0004] Furthermore, the traditional gas cylinder manufacturing process uses a single temperature field static curing technology. Due to the lack of dynamic pressure control and temperature gradient coordination mechanism, the resin flow path is restricted, local penetration is uneven, and problems such as thermal stress concentration, uneven resin penetration and poor dimensional stability are easily caused. Summary of the Invention

[0005] Therefore, embodiments of the present invention provide a molding and processing method for composite material gas cylinders to solve at least one of the above-mentioned technical problems.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] This invention provides a molding and processing method for composite material gas cylinders, comprising:

[0008] The pre-processed metal valve seat is positioned and embedded into the cavity of the injection mold, and then formed into an inner liner preform that encloses the metal valve seat by high-pressure injection molding.

[0009] The preformed liner is transferred to a blow molding machine for integrated blow molding, resulting in a gas cylinder liner with seamless integration of the liner and metal valve seat, zero interface gaps, and high bonding strength.

[0010] Based on the principle of dry prepreg yarn, the laying parameters of the composite gas cylinder winding layer are calculated using grid theory, and the layer design scheme is obtained.

[0011] On the outer surface of the surface-treated gas cylinder liner, a carbon fiber winding layer is laid according to the layup design scheme using a dry prepreg yarn winding technology.

[0012] High-pressure composite gas cylinder products are obtained through a combination of heating curing and molding.

[0013] In some embodiments, the bottom edge of the metal valve seat is a wing-shaped arc structure, and the bottom end of the metal valve seat has two levels of concave annular grooves to form a circumferential embedded structure.

[0014] Interlaced square annular grooves are formed on the inner and outer walls of the central deep hole to create an axial locking interface;

[0015] A circumferential protrusion structure is provided at the upper end of the valve seat. When the fiber is wound, the protrusion serves as a physical anchor point, so that the fiber layup and the protrusion form a mechanical interlock.

[0016] In some embodiments, the two levels of concave annular grooves have different depths, and the width of the concave annular groove is 3-4 mm; and / or, the width of the square annular groove is 2-3 mm and the depth is 1-2 mm.

[0017] In some embodiments, the blow molding process includes the following steps:

[0018] Mold pretreatment;

[0019] Start the heating system at the filler inlet above the preform to melt and extrude the plastic raw material;

[0020] When the extruded cylindrical molten plastic segment reaches the preset length, the left and right cavities of the blow molding die are closed. At the same time, the circumferential protrusion at the upper end of the metal valve seat and the positioning groove at the bottom of the blow molding die form a mechanical fitting structure. The axial positioning is achieved through their concave-convex fit, and the mold closing force is applied to seal the cut-off molten plastic segment and the inner liner blank together in the sealed cavity.

[0021] After the mold is closed, compressed air is injected in stages through the bottom air injection needle; first, low-pressure compressed air is injected into the interior to allow the molten plastic to initially extend and conform to the top cavity contour; then the air pressure is gradually increased to perform high-pressure shaping, and the stepped internal pressure is used to drive the molten plastic to expand evenly to ensure that it fits tightly against the entire inner wall of the mold cavity.

[0022] After blow molding, cooling and demolding are carried out. Cooling water is circulated outside the mold to quickly solidify and shape the composite material liner. After the product cools to room temperature, the blow needle is removed, and the mold and product are separated by a smooth demolding action relying on the low friction interface of the PTFE film, finally producing a seamless integrated gas cylinder liner.

[0023] In some embodiments, the calculation of the laying parameters of the composite gas cylinder winding layer using mesh theory specifically includes:

[0024] The thickness of the circumferential and longitudinal winding layers was estimated based on grid theory.

[0025] Calculate the minimum winding angle of the end cap section, select the helical ply angle, and the number of ply layers;

[0026] If the strength check determines that the winding layer initially meets the requirements, the stress-strain analysis of the gas cylinder wound according to the laying parameters is carried out using a pre-constructed finite element model, and the fiber damage is determined according to the failure criteria.

[0027] In some embodiments, the circumferential winding layer thickness and the longitudinal winding layer thickness are estimated based on mesh theory, specifically including:

[0028] Based on data such as gas cylinder size parameters and carbon fiber volume content, the layup thickness is initially estimated, and the equilibrium equation in the grid dimension is:

[0029]

[0030] The formulas for calculating the thickness of circumferential and helical fibers are derived by reverse derivation as follows:

[0031]

[0032] Where, σ fα and σ fθ These represent the longitudinal and circumferential fiber stresses, respectively; h fα and h fθ These represent the longitudinal and circumferential fiber thicknesses of the layup, respectively, with α being the longitudinal helical winding angle; p b The required burst strength of the gas cylinder.

[0033] In some embodiments, stress-strain analysis is performed on gas cylinders wound according to laying parameters using a pre-built finite element model, specifically including:

[0034] Create a 3D model of the gas cylinder;

[0035] Import the inner lining 3D model of the gas cylinder 3D model, define the material properties of the inner lining and carbon fiber and assign them to the corresponding parts respectively;

[0036] Add fiber layups by setting the layup angle and number of layers according to circumferential and helical directions;

[0037] Set the binding relationship between the lining and the ply, and perform mesh generation on it;

[0038] Apply internal pressure load and constrain valve seat displacement;

[0039] Simulate fiber failure behavior under internal pressure load and predict burst pressure and damage evolution path.

[0040] In some embodiments, determining fiber damage based on failure criteria specifically includes:

[0041] Extract the finite element analysis contour plot of the current layup;

[0042] The ply design is analyzed based on the finite element analysis cloud diagram combined with the maximum strain criterion and the Hashin criterion;

[0043] If the gas cylinder ply does not suffer through-hole damage and failure, the designed ply scheme is deemed effective; otherwise, the current ply design is deemed to have failed, and local ply optimization iterations are implemented for the loss-concentrated areas in the cloud map until the ply scheme becomes effective.

[0044] In some embodiments, the basic prepreg winding technology lays up a carbon fiber winding layer according to the layup design scheme, specifically including:

[0045] Using a non-geodetic winding forming method with non-graded holes, one end of the dry prepreg yarn is spirally wound to the opening position of the gas cylinder, and the other end is spirally wound to the closed position of the gas cylinder.

[0046] After winding, a layer of high-temperature OPP tape is wound around the entire surface of the gas cylinder. The high-temperature OPP tape is wound in a spiral direction and extends directly to the end cap and cylinder body section after winding.

[0047] In some embodiments, the heat curing and molding process is combined, specifically including:

[0048] The wound gas cylinder is transferred into a molding container, where it is cured through the combined action of gradient heating and dynamic pressure.

[0049] The gas cylinder is fixed at the top by a mold, and the molding container is heated in three stages: the low temperature stage is 80-100℃ to reduce the resin viscosity and promote fiber inter-fiber penetration; the medium temperature stage is 120-130℃ to trigger the resin cross-linking reaction to form a preliminary cured matrix; and the high temperature stage is 150-160℃ to complete the final curing and simultaneously start the external circulation cooling system of the mold for directional heat dissipation to suppress the accumulation of thermal stress.

[0050] At the same time, dynamic pressure is applied by blowing needles, and the internal pressure gradually increases with each stage of the curing process.

[0051] After curing, wait for the mold to cool down and release the pressure inside the container. Then, separate the upper and lower molds through the demolding mechanism on the mold parting surface. At the same time, start the hydraulic ejection device to smoothly push the cured gas cylinder out of the molding container to obtain the finished high-pressure hydrogen storage composite gas cylinder.

[0052] In one or more of the above specific embodiments, the molding and processing method provided by the present invention has at least the following technical effects:

[0053] 1. The interface bonding strength and airtightness are significantly improved, solving the problem of weak connection in traditional valve seats.

[0054] To address the issues of insufficient contact area and low bonding strength caused by the smooth surface of traditional metal valve seats, the molding and processing method provided by this invention utilizes a dual structure of multi-level concave annular grooves and staggered square annular grooves on the outer surface of the valve seat. Combined with high-pressure injection molding, this creates a three-dimensional interlocking interface of "radial annular groove embedding + axial square groove locking," significantly increasing the contact area between the molten plastic and the valve seat. Simultaneously, the circumferential protrusion structure at the upper end of the valve seat is compatible with fiber winding technology, forming a mechanical interlock that fixes the fiber layer. This dual-dimensional reinforcement of the structure through interface bonding and fiber locking significantly enhances sealing reliability and long-term airtightness, completely resolving the weak interface problem caused by the simple structure of traditional valve seats.

[0055] 2. Eliminate welding defects and stress concentration to improve structural reliability and yield.

[0056] Abandoning the traditional "split injection molding + welding" process, the molding and processing method provided by this invention utilizes a high-pressure injection molding preform + blow molding integrated molding technology. High-pressure injection ensures full contact between the molten plastic and the metal valve seat grooves; simultaneously, combined with blow molding and stepped internal pressure control, it achieves seamless integrated molding. This technology completely eliminates defects such as weld seam position deviation and high surface roughness, significantly improving structural reliability and production efficiency.

[0057] 3. Optimization of resin distribution uniformity and mechanical properties to solve static curing defects.

[0058] To address the issues of uneven resin penetration and thermal stress concentration in traditional static curing processes, the molding and processing method provided by this invention employs a combined strategy of dry prepreg winding technology and gradient heating-dynamic molding. The dry prepreg precisely controls the resin content (25% ± 2%), avoiding dry spots and resin-rich defects associated with wet winding. The resin viscosity evolution is optimized through a three-stage gradient heating process (80℃→120℃→150℃), and combined with dynamic pressure loading, it promotes the directional penetration of resin into the fiber gaps, while simultaneously improving dimensional stability and significantly optimizing the overall mechanical properties of the gas cylinder.

[0059] 4. Collaborative innovation in processes to achieve a balance between lightweight design and high performance.

[0060] Through the synergistic effect of a seamless integrated liner structure and a precise layup design using dry prepreg yarn, the molding and processing method provided by this invention achieves lightweighting while improving mechanical properties. The integrated design reduces redundant materials, lowering the weight of the metal valve seat and liner assembly by 15%–20%. The dry winding technology, by precisely controlling the resin content (fluctuation ±2%), avoids the resin waste (fluctuation ±5%) of traditional wet processes. Furthermore, by combining finite element analysis and multi-criteria optimization, an optimal balance between material distribution and performance is achieved while meeting the requirements of high-pressure hydrogen storage. Attached Figure Description

[0061] To more clearly illustrate the embodiments of the present invention or the technical solutions in 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 merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0062] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0063] Figure 1 One of the structural schematic diagrams of the composite material gas cylinder structure provided by the present invention;

[0064] Figure 2 This is a second structural schematic diagram of the composite material gas cylinder structure provided by the present invention;

[0065] Figure 3 This is a schematic diagram of the composite gas cylinder structure provided by the present invention under thermosetting and molding treatment conditions;

[0066] Figure 4 This is a schematic diagram of the structure of the metal valve seat provided by the present invention;

[0067] Figure 5 This is a schematic diagram of the metal valve seat provided by the present invention in the mold feeding and filling state;

[0068] Figure 6 This is a schematic diagram of the metal valve seat provided by the present invention in a cooled and demolded state.

[0069] Figure 7 This is a schematic diagram of the blow molding process provided by the present invention, wherein, Figure 7 (a) shows the extrusion state of the molten filler. Figure 7 (b) is a diagram showing the closed mold state. Figure 7 Image (c) shows the pressurized blow molding process. Figure 7 The middle (d) diagram shows the cooling and demolding state.

[0070] Figure 8 This is a contour plot of the results from the finite element analysis, where... Figure 8 (a) is the stress analysis contour plot. Figure 8(b) is a fiber failure contour map;

[0071] Figure 9 This is a simulation diagram of the circumferential winding molding of the composite material gas cylinder provided by the present invention;

[0072] Figure 10 A simulation diagram of the spiral winding forming of the composite material gas cylinder provided by the present invention;

[0073] Figure 11 A simulation diagram of the spiral winding of the closed end of the composite gas cylinder provided by the present invention;

[0074] Figure 12 A simulation diagram of the spiral winding of the open end of the composite gas cylinder provided by the present invention;

[0075] Figure 13 A simulation diagram of the spiral-oriented enlarged-hole winding of the composite material gas cylinder provided by the present invention;

[0076] Figure 14 A simulation diagram of the spiral hollow winding of the composite material gas cylinder provided by the present invention;

[0077] Figure 15 This is a schematic diagram of the molding process of the composite material gas cylinder provided by the present invention. Detailed Implementation

[0078] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0079] In one specific embodiment, the molding and processing method for composite material gas cylinders provided by the present invention includes the following steps:

[0080] S110: Position and embed the pre-processed metal valve seat 1 into the injection mold cavity, and form an inner liner preform that wraps around the metal valve seat 1 by high-pressure injection molding;

[0081] S120: The preformed inner liner is transferred to a blow molding equipment for integrated blow molding to obtain a gas cylinder inner liner 2 with seamless integration of the inner liner and metal valve seat, zero interface gaps, and high bonding strength.

[0082] S130: Based on the principle of dry prepreg yarn, the layup parameters of the composite gas cylinder winding layer are calculated using grid theory, and the layup design scheme is obtained.

[0083] S140: On the outer surface of the surface-treated gas cylinder liner, a carbon fiber winding layer 3 is laid out according to the layup design scheme using a dry prepreg yarn winding technology.

[0084] S150: High-pressure composite gas cylinder products are obtained through a combination of heat curing and molding.

[0085] In general, such as Figures 1-3 As shown, firstly, a pre-processed metal valve seat 1 is positioned and embedded into the injection mold cavity, and then high-pressure injection molding is used to form a preformed inner liner that encloses the metal valve seat. Subsequently, this preformed body is transferred to a blow molding machine for blow molding, resulting in a gas cylinder liner 2 with seamless integration between the liner and the metal valve seat, zero interface gaps, and high bonding strength. Next, a carbon fiber winding layer is precisely laid on the outside of this gas cylinder liner using a dry prepreg winding technique. Finally, after heat curing and molding synergistic treatment, the high-pressure composite gas cylinder product is obtained. This process ensures improved yield while simultaneously reducing the overall weight of the gas cylinder.

[0086] In some embodiments, the bottom edge of the metal valve seat 1 is a wing-shaped arc structure 11, and the bottom end of the metal valve seat 1 has two levels of concave annular grooves 12 to form a circumferential embedding structure; the inner and outer walls of the central deep hole have staggered square annular grooves to construct an axial locking interface; a circumferential protrusion structure 13 is provided at the upper end of the metal valve seat 1. During fiber winding, the protrusion structure 13 serves as a physical anchor point, so that the fiber layup and the protrusion structure 13 form a mechanical interlock. The two levels of concave annular grooves 12 have different depths, with the groove width of the concave annular groove 12 being 3–4 mm; and / or, the groove width of the square annular groove is 2–3 mm, and the depth is 1–2 mm.

[0087] Specifically, in the structural design of the metal valve seat 1, such as Figure 4 As shown, to ensure a high-strength bond and long-term sealing between the metal valve seat 1 and the liner, the bottom edge of the metal valve seat 1 is designed as a wing-shaped arc structure 11 with a smooth curved transition. Two levels of concave annular grooves, one deep and one shallow, are formed from the bottom, with a groove width of 3-4 mm, creating a circumferential embedding structure. Staggered square annular grooves, with a groove width of 2-3 mm and a depth of 1-2 mm, are formed on the inner and outer walls of the central deep hole, creating an axial locking interface. Simultaneously, an annular protrusion structure is provided at the upper end of the valve seat. During fiber winding, the protrusion serves as a physical anchor point, mechanically interlocking the fiber layup with the protrusion to inhibit fiber slippage. This structural design increases the contact area between the valve seat and the plastic liner by 30%-40% from a traditional smooth surface, forming a dual-combination mechanism of "radial annular groove embedding + axial square groove locking." During the injection molding process, the molten plastic is directionally filled along the groove wall. After solidification, it forms a three-dimensional interlocking interface with the metal valve seat, which improves the interface shear strength. The symmetrical groove layout structure ensures that the plastic liner is subjected to uniform stress and avoids local stress concentration.

[0088] Furthermore, such as Figure 5 and Figure 6 As shown, during the preparation of the high-pressure injection molded liner preform, the bottom end of the aforementioned metal valve seat 1 is sandblasted to further improve the interfacial adhesion between the metal valve seat and the plastic. The metal valve seat is precisely embedded into the mold cavity, and then the mold is closed to form a sealed cavity. High-pressure injection molding (pressure 80-110 MPa, material temperature controlled at 220-250℃) is used to fully fill the grooves on the surface of the valve seat with molten plastic (such as HDPE), achieving complete coverage of the bottom end of the metal valve seat. After injection molding, the mold circulation cooling system (coolant temperature 20-30℃) is activated to implement gradient cooling, allowing the plastic layer inside the mold to quickly solidify and set. After mold opening and demolding operations, the liner preform with the plastic-coated metal valve seat is obtained.

[0089] In some embodiments, such as Figure 7 As shown, the blow molding process includes the following steps:

[0090] Mold pretreatment: The inner liner preform obtained by high-pressure injection molding is inverted into the open blow molding mold, and the blow needle is introduced. At the same time, a PTFE film is pre-laid in the mold cavity to reduce interfacial adhesion by utilizing its low surface energy properties, which helps to avoid damage to the surface of the product during subsequent demolding operations.

[0091] Start the heating system at the filler inlet above the preform to melt and extrude the plastic raw material;

[0092] When the extruded cylindrical molten plastic segment reaches the preset length, the left and right cavities of the blow molding die are closed. At the same time, the circumferential protrusion at the upper end of the metal valve seat forms a mechanical fitting structure with the positioning groove at the bottom of the blow molding die. The axial positioning is achieved through the concave-convex fit (positioning error ≤ ±0.05mm), and the mold closing force is applied to seal the cut-off molten plastic segment and the inner liner blank together in the sealed cavity.

[0093] After the mold is closed, compressed air is injected in stages through the bottom air injection needle; first, low-pressure compressed air (0.5-1.0MPa) is injected into the interior to allow the molten plastic to initially extend and conform to the top cavity contour; then the air pressure is gradually increased for high-pressure shaping (2.0-3.0MPa), using stepped internal pressure to drive the molten plastic to expand evenly, ensuring that it tightly conforms to the entire inner wall of the mold cavity;

[0094] After blow molding, cooling and demolding are carried out. Cooling water is circulated outside the mold to quickly solidify and shape the composite material liner. After the product cools to room temperature, the blow needle is removed, and the mold and product are separated by a smooth demolding action relying on the low friction interface of the PTFE film, finally producing a seamless integrated gas cylinder liner.

[0095] Specifically, the outer surface treatment technology of the liner is as follows: the outer surface of the molded plastic liner is first cleaned with solvents such as alcohol, and then a polyurea or polyurethane coating is sprayed on the surface. After heating and curing (temperature 80℃, 2h), a surface coating is formed with a coating thickness of 0.2 to 0.8 mm, so as to enhance the interfacial bonding force between the plastic liner and the carbon fiber composite material layer.

[0096] In some embodiments, the calculation of the laying parameters of the composite gas cylinder winding layer using mesh theory specifically includes the following steps:

[0097] S1: The thickness of the circumferential and longitudinal winding layers is estimated based on grid theory; specifically, this includes: a preliminary estimate of the layup thickness based on cylinder size parameters and carbon fiber volume content, with the equilibrium equation in the grid dimension being:

[0098]

[0099] The key to winding layer design is determining its wall thickness. The formulas for calculating the thickness of circumferential and helical fibers can be derived from the above formulas:

[0100]

[0101] Where, σ fα and σ fθ These represent the longitudinal and circumferential fiber stresses, respectively; h fα and h fθ These represent the longitudinal and circumferential fiber thicknesses of the layup, respectively, with α being the longitudinal helical winding angle; p b To determine the required burst strength of the gas cylinder, the average value of the winding angle α is taken as 20°.

[0102] The thickness h of the wound fiber can be estimated after calculation. fα and h fθ Dividing the fiber thickness by the single-layer thickness of the fiber layer yields the number of spiral and circumferential winding layers in the composite gas cylinder; thus, the initial thickness design of the composite layer is completed.

[0103] S2: Calculate the minimum winding angle of the end cap section, select the helical layup angle, and the number of layup layers. During the end cap section angle design process, if a single winding angle is used, fiber accumulation is likely to occur at the end cap position; therefore, different winding angles need to be selected. First, based on mesh theory and fiber balance equations, the minimum winding angle is derived, as shown in the following formula:

[0104]

[0105] Where R is the radius of the cylinder section and r0 is the radius of the end cap.

[0106] Subsequently, the angles are designed in layers according to the circumferential and helical ply types. The circumferential ply angle is only 90°, while the helical ply angle is gradually transitioned according to the number of layers to complete the angle design.

[0107] S3: If the strength check determines that the winding layer initially meets the requirements, the pre-constructed finite element model is used to perform stress-strain analysis on the gas cylinder wound according to the laying parameters, and the fiber damage is determined according to the failure criteria.

[0108] During the strength verification of the gas cylinder, the longitudinal and circumferential burst pressures are calculated using the fiber balance equation based on the completed ply design to determine whether the ply meets the requirements. The formula is as follows:

[0109]

[0110] Where p α For longitudinal winding blasting pressure, p θ The circumferential blasting pressure.

[0111] In some embodiments, stress-strain analysis is performed on gas cylinders wound according to laying parameters using a pre-built finite element model, specifically including:

[0112] Create a 3D model of the gas cylinder;

[0113] Import the inner lining 3D model of the gas cylinder 3D model, define the material properties of the inner lining and carbon fiber and assign them to the corresponding parts respectively;

[0114] Add fiber layups by setting the layup angle and number of layers according to circumferential and helical directions;

[0115] Set the binding relationship between the lining and the ply, and perform mesh generation on it;

[0116] Apply internal pressure load and constrain valve seat displacement;

[0117] Simulate fiber failure behavior under internal pressure load and predict burst pressure and damage evolution path.

[0118] The determination of fiber damage based on failure criteria specifically includes:

[0119] Extract the finite element analysis contour plot of the current layup;

[0120] The ply design is analyzed based on the finite element analysis cloud diagram combined with the maximum strain criterion and the Hashin criterion;

[0121] If the gas cylinder ply does not suffer through-hole damage and failure, the designed ply scheme is deemed effective; otherwise, the current ply design is deemed to have failed, and local ply optimization iterations are implemented for the loss-concentrated areas in the cloud map until the ply scheme becomes effective.

[0122] Specifically, in the overall finite element analysis process, a three-dimensional model of the gas cylinder was established using ABAQUS finite element software. First, the constructed three-dimensional model of the liner (containing separate features for the metal valve seat and the plastic liner) was imported. Then, the material properties of the liner and carbon fiber were defined and assigned to the corresponding parts. Using the "wcm" plugin, fiber layups were added according to the circumferential and helical directions, setting the layup angle and number of layers. Subsequently, the binding relationship between the liner and the layups was established, and the mesh was generated. Internal pressure loads were applied, and valve seat displacement was constrained. Simultaneously, the Hashin criterion was introduced to simulate fiber failure behavior under internal pressure loads and predict burst pressure and damage evolution paths.

[0123] The specific formula for the Hashin criterion is as follows:

[0124] ① Fiber failure:

[0125]

[0126] ②Matrix failure:

[0127]

[0128] ③ Layering:

[0129]

[0130] in Xt, Xc, Yt, Yc, Sl, and St represent the strengths of the composite material in each direction.

[0131] After performing the above operations, you can submit the analysis. Once the analysis is complete, you can extract the finite element analysis contour plot of the current layer, such as... Figure 8 As shown.

[0132] Based on this cloud map, the ply design is analyzed using the maximum strain criterion and the Hashin criterion. If the gas cylinder ply does not suffer through-thrust damage and failure, it indicates that the designed ply scheme is effective. Otherwise, it proves that the current ply design has failed. Local ply optimization needs to be implemented for the loss-concentrated areas in the cloud map. Through multiple design iterations and re-analysis and verification, it is necessary to ensure compliance with strength standards and finally obtain an efficient and reliable ply scheme that meets the high-pressure hydrogen storage requirements.

[0133] In some embodiments, the basic prepreg winding technology lays up a carbon fiber winding layer according to the layup design scheme, specifically including:

[0134] Using a non-geodetic winding forming method with non-graded holes, one end of the dry prepreg yarn is spirally wound to the opening position of the gas cylinder, and the other end is spirally wound to the closed position of the gas cylinder.

[0135] After winding, a layer of high-temperature OPP tape is wound around the entire surface of the gas cylinder. The high-temperature OPP tape is wound in a spiral direction and extends directly to the end cap and cylinder body section after winding.

[0136] Specifically, during the carbon fiber winding layup process, an optimized layup scheme based on finite element analysis is employed, using dry prepreg winding technology to wind the fibers: dry prepreg carbon fiber yarn is loaded onto a multi-axis linkage winding device, and a robotic arm winding device winds and shapes the composite material layers. To ensure the strength of the composite material gas cylinder, this project adopts a dry prepreg winding + helical winding scheme.

[0137] During the winding process, the cylinder body section is wound circumferentially to provide circumferential strength to the composite material cylinder. Figure 9 As shown.

[0138] Dry prepreg yarn is used for helical winding. Since the gas cylinder has an open-end structure, the high coefficient of friction of the dry prepreg yarn can be utilized, employing a non-geodetic winding method with varying hole sizes, such as... Figures 10-13 As shown, one end is wound to the open position, and the other end can be wound to the closed position.

[0139] In order to ensure and meet the structural design strength requirements of the present invention during the winding process, spiral expansion winding technology with different winding angles is adopted, which can achieve the overall burst pressure requirements.

[0140] In order to further reduce the weight of the gas cylinders in this project during the winding process, a spiral winding method with partial coverage is adopted, such as... Figure 14 As shown.

[0141] After winding, a layer of high-temperature OPP tape needs to be wound onto the entire surface of the gas cylinder. The OPP tape is made of PP. During the winding process, the width of the OPP tape is 10mm and the overlap width is 6mm. It is wound in a spiral direction and can directly reach the end cap and cylinder body after winding.

[0142] In some embodiments, the heat curing and molding process is combined, specifically including:

[0143] The wound gas cylinder is transferred into a molding container, where it is cured through the combined action of gradient heating and dynamic pressure.

[0144] The gas cylinder is fixed at the top by a mold, and the molding container is heated in three stages: the low temperature stage is 80-100℃ to reduce the resin viscosity and promote fiber inter-fiber penetration; the medium temperature stage is 120-130℃ to trigger the resin cross-linking reaction to form a preliminary cured matrix; and the high temperature stage is 150-160℃ to complete the final curing and simultaneously start the external circulation cooling system of the mold for directional heat dissipation to suppress the accumulation of thermal stress.

[0145] At the same time, dynamic pressure is applied by blowing needles, and the internal pressure gradually increases with each stage of the curing process.

[0146] After curing, wait for the mold to cool down and release the pressure inside the container. Then, separate the upper and lower molds through the demolding mechanism on the mold parting surface. At the same time, start the hydraulic ejection device to smoothly push the cured gas cylinder out of the molding container to obtain the finished high-pressure hydrogen storage composite gas cylinder.

[0147] Specifically, in the combined heating and molding process, the wound gas cylinder is transferred to a dedicated molding container (the cavity contour fits the outer surface of the gas cylinder). Efficient curing is achieved through the combined effect of gradient heating and dynamic pressure. After the top of the gas cylinder is fixed by the mold, the molding container undergoes a three-stage gradient heating: a low-temperature stage (80–100℃) reduces resin viscosity to promote fiber inter-fiber penetration; a medium-temperature stage (120–130℃) triggers the resin cross-linking reaction to form a preliminary cured matrix; and a high-temperature stage (150–160℃) completes final curing while simultaneously activating the external cooling system of the mold for directional heat dissipation, suppressing the accumulation of thermal stress. At the same time, dynamic pressure (5–10 MPa of inert gas) is applied via a blower to ensure tight adhesion between fiber layers. Throughout the curing process, the internal pressure gradually increases with each stage to offset the deformation risk caused by molding shrinkage. Figure 15 As shown. After curing, wait for the mold to cool down and release the pressure inside the container. Then, separate the upper and lower molds through the demolding mechanism on the mold parting surface. At the same time, start the hydraulic ejection device to smoothly push the cured gas cylinder out of the molding container to obtain the finished high-pressure hydrogen storage composite gas cylinder.

[0148] Furthermore, the processing method provided by this invention can replace traditional welding with high-precision laser welding. Specifically, a fiber laser welding system (wavelength 1070nm, power 2-4kW) is used to precisely weld the split plastic liner. By dynamically adjusting the process parameters through focused laser beam (spot diameter ≤0.1mm) and real-time infrared thermal imaging monitoring (accuracy ±5℃), the weld width is controlled to ≤0.5mm, optimizing surface roughness while reducing thermal deformation.

[0149] The processing method provided by this invention can be used for digital photopolymerization 3D printing of the lining. Specifically, digital photopolymerization (DLP) 3D printing technology is used, with UV-curable polyurethane acrylate photosensitive resin as the raw material, to directly form a lining with a complex geometric structure. Threaded holes are pre-machined on the surface of the metal valve seat and simultaneously embedded during the printing process. Layer-by-layer exposure is achieved using an ultraviolet light source (wavelength 365nm) (exposure time 5-10s / layer), achieving a lining wall thickness accuracy of ±0.02mm. After printing, a post-curing treatment at 80℃ for 2 hours is performed to eliminate residual stress and improve dimensional stability.

[0150] The processing method provided by this invention employs ultrasonic vibration-assisted resin penetration technology. Specifically, a wet fiber winding process is used, with a high-frequency ultrasonic vibration device (vibration frequency 20–40 kHz, amplitude 5–10 μm) installed at the winding head. The ultrasonic cavitation effect disrupts the surface tension of the resin, generating micro-jets that impact the gaps between the fiber bundles. Simultaneously, a vacuum negative pressure environment forms a synergistic mechanism of "ultrasonic cavitation + vacuum suction": ultrasonic energy causes the resin to overcome the fiber interface resistance and rapidly wet the fiber, while the vacuum environment accelerates the resin penetration path through the negative pressure difference. During the process, a real-time resin viscosity monitoring system is used to dynamically adjust the ultrasonic vibration power (50–200 W) to ensure efficient penetration of resins in different viscosity ranges.

[0151] In one or more of the above specific embodiments, the molding and processing method provided by the present invention has at least the following technical effects:

[0152] 1. The interface bonding strength and airtightness are significantly improved, solving the problem of weak connection in traditional valve seats.

[0153] To address the issues of insufficient contact area and low bonding strength caused by the smooth surface of traditional metal valve seats, the molding and processing method provided by this invention utilizes a dual structure of multi-level concave annular grooves and staggered square annular grooves on the outer surface of the valve seat. Combined with high-pressure injection molding, this creates a three-dimensional interlocking interface of "radial annular groove embedding + axial square groove locking," significantly increasing the contact area between the molten plastic and the valve seat. Simultaneously, the circumferential protrusion structure at the upper end of the valve seat is compatible with fiber winding technology, forming a mechanical interlock that fixes the fiber layer. This dual-dimensional reinforcement of the structure through interface bonding and fiber locking significantly enhances sealing reliability and long-term airtightness, completely resolving the weak interface problem caused by the simple structure of traditional valve seats.

[0154] 2. Eliminate welding defects and stress concentration to improve structural reliability and yield.

[0155] Abandoning the traditional "split injection molding + welding" process, the molding and processing method provided by this invention utilizes a high-pressure injection molding preform + blow molding integrated molding technology. High-pressure injection ensures full contact between the molten plastic and the metal valve seat grooves; simultaneously, combined with blow molding and stepped internal pressure control, it achieves seamless integrated molding. This technology completely eliminates defects such as weld seam position deviation and high surface roughness, significantly improving structural reliability and production efficiency.

[0156] 3. Optimization of resin distribution uniformity and mechanical properties to solve static curing defects.

[0157] To address the issues of uneven resin penetration and thermal stress concentration in traditional static curing processes, the molding and processing method provided by this invention employs a combined strategy of dry prepreg winding technology and gradient heating-dynamic molding. The dry prepreg precisely controls the resin content (25% ± 2%), avoiding dry spots and resin-rich defects associated with wet winding. The resin viscosity evolution is optimized through a three-stage gradient heating process (80℃→120℃→150℃), and combined with dynamic pressure loading, it promotes the directional penetration of resin into the fiber gaps, while simultaneously improving dimensional stability and significantly optimizing the overall mechanical properties of the gas cylinder.

[0158] 4. Collaborative innovation in processes to achieve a balance between lightweight design and high performance.

[0159] Through the synergistic effect of a seamless integrated liner structure and a precise layup design using dry prepreg yarn, the molding and processing method provided by this invention achieves lightweighting while improving mechanical properties. The integrated design reduces redundant materials, lowering the weight of the metal valve seat and liner assembly by 15%–20%. The dry winding technology, by precisely controlling the resin content (fluctuation ±2%), avoids the resin waste (fluctuation ±5%) of traditional wet processes. Furthermore, by combining finite element analysis and multi-criteria optimization, an optimal balance between material distribution and performance is achieved while meeting the requirements of high-pressure hydrogen storage.

[0160] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of the present invention should be included within the scope of protection of the present invention.

Claims

1. A liner structure for a composite material gas cylinder, characterized in that, include: The pre-processed metal valve seat is positioned and embedded into the cavity of the injection mold, and then formed into an inner liner preform that encloses the metal valve seat by high-pressure injection molding. The preformed liner is transferred to a blow molding machine for integrated blow molding, resulting in a gas cylinder liner with seamless integration of the liner and metal valve seat, zero interface gaps, and high bonding strength. Based on the principle of dry prepreg yarn, the laying parameters of the composite gas cylinder winding layer are calculated using grid theory, and the layer design scheme is obtained. On the outer surface of the surface-treated gas cylinder liner, a carbon fiber winding layer is laid according to the layup design scheme using a dry prepreg yarn winding technology. High-pressure composite gas cylinder products are obtained through a combination of heating curing and molding.

2. The liner structure of the composite material gas cylinder according to claim 1, characterized in that, The bottom edge of the metal valve seat has a wing-shaped arc structure, and the bottom end of the metal valve seat has two levels of concave annular grooves to form a circumferential embedded structure. Interlaced square annular grooves are formed on the inner and outer walls of the central deep hole to create an axial locking interface; A circumferential protrusion structure is provided at the upper end of the valve seat. When the fiber is wound, the protrusion serves as a physical anchor point, so that the fiber layup and the protrusion form a mechanical interlock.

3. The liner structure of the composite material gas cylinder according to claim 2, characterized in that, The two levels of concave annular grooves have different depths, with the width of the concave annular groove being 3-4 mm; and / or, the width of the square annular groove being 2-3 mm and the depth being 1-2 mm.

4. The liner structure of the composite material gas cylinder according to claim 1, characterized in that, The blow molding process includes the following steps: Mold pretreatment; Start the heating system at the filler inlet above the preform to melt and extrude the plastic raw material; When the extruded cylindrical molten plastic segment reaches the preset length, the left and right cavities of the blow molding die are closed. At the same time, the circumferential protrusion at the upper end of the metal valve seat and the positioning groove at the bottom of the blow molding die form a mechanical fitting structure. The axial positioning is achieved through their concave-convex fit, and the mold closing force is applied to seal the cut-off molten plastic segment and the inner liner blank together in the sealed cavity. After the mold is closed, compressed air is injected in stages through the bottom air injection needle; first, low-pressure compressed air is injected into the interior to allow the molten plastic to initially extend and conform to the top cavity contour; then the air pressure is gradually increased to perform high-pressure shaping, and the stepped internal pressure is used to drive the molten plastic to expand evenly to ensure that it fits tightly against the entire inner wall of the mold cavity. After blow molding, cooling and demolding are carried out. Cooling water is circulated outside the mold to quickly solidify and shape the composite material liner. After the product cools to room temperature, the blow needle is removed, and the mold and product are separated by a smooth demolding action relying on the low friction interface of the PTFE film, finally producing a seamless integrated gas cylinder liner.

5. The liner structure of the composite material gas cylinder according to claim 1, characterized in that, The calculation of the laying parameters of the composite gas cylinder winding layer using grid theory specifically includes: The thickness of the circumferential and longitudinal winding layers was estimated based on grid theory. Calculate the minimum winding angle of the end cap section, select the helical ply angle, and the number of ply layers; If the strength verification determines that the winding layer initially meets the requirements, the stress-strain analysis of the gas cylinder wound according to the laying parameters is carried out using a pre-constructed finite element model, and the fiber damage is determined according to the failure criteria.

6. The liner structure of the composite material gas cylinder according to claim 5, characterized in that, The thicknesses of the circumferential and longitudinal winding layers are estimated based on mesh theory, specifically including: Based on data such as gas cylinder size parameters and carbon fiber volume content, the layup thickness is initially estimated, and the equilibrium equation in the grid dimension is: The formulas for calculating the thickness of circumferential and helical fibers are derived by reverse derivation as follows: Where, σ fα and σ fθ These represent the longitudinal and circumferential fiber stresses, respectively; h fα and h fθ These represent the longitudinal and circumferential fiber thicknesses of the layup, respectively, with α being the longitudinal helical winding angle; p b The required burst strength of the gas cylinder.

7. The liner structure of the composite material gas cylinder according to claim 5, characterized in that, Stress-strain analysis was performed on a gas cylinder wound according to the laying parameters using a pre-built finite element model, specifically including: Create a 3D model of the gas cylinder; Import the inner lining 3D model of the gas cylinder 3D model, define the material properties of the inner lining and carbon fiber and assign them to the corresponding parts respectively; Add fiber layups by setting the layup angle and number of layers according to circumferential and helical directions; Set the binding relationship between the lining and the ply, and perform mesh generation on it; Apply internal pressure load and constrain valve seat displacement; Simulate fiber failure behavior under internal pressure load and predict burst pressure and damage evolution path.

8. The liner structure of the composite material gas cylinder according to claim 7, characterized in that, The degree of fiber damage is determined according to the failure criteria, specifically including: Extract the finite element analysis contour plot of the current layup; The ply design is analyzed based on the finite element analysis cloud diagram combined with the maximum strain criterion and the Hashin criterion; If the gas cylinder ply does not suffer through-hole damage and failure, the designed ply scheme is deemed effective; otherwise, the current ply design is deemed to have failed, and local ply optimization iterations are implemented for the loss-concentrated areas in the cloud map until the ply scheme becomes effective.

9. The liner structure of the composite material gas cylinder according to claim 1, characterized in that, The basic prepreg winding technology lays up a carbon fiber winding layer according to the layup design scheme, specifically including: Using a non-geodetic winding forming method with non-graded holes, one end of the dry prepreg yarn is spirally wound to the opening position of the gas cylinder, and the other end is spirally wound to the closed position of the gas cylinder. After winding, a layer of high-temperature OPP tape is wound around the entire surface of the gas cylinder. The high-temperature OPP tape is wound in a spiral direction and extends directly to the end cap and cylinder body section after winding.

10. The liner structure of the composite material gas cylinder according to claim 1, characterized in that, The combined heat curing and molding process includes: The wound gas cylinder is transferred into a molding container, where it is cured through the combined action of gradient heating and dynamic pressure. The gas cylinder is fixed at the top by a mold, and the molding container is heated in three stages: the low temperature stage is 80-100℃ to reduce the resin viscosity and promote fiber penetration; the medium temperature stage is 120-130℃ to trigger the resin cross-linking reaction to form a preliminary cured matrix; and the high temperature stage is 150-160℃ to complete the final curing and simultaneously start the external circulation cooling system of the mold for directional heat dissipation to suppress the accumulation of thermal stress. At the same time, dynamic pressure is applied by blowing needles, and the internal pressure gradually increases with each stage of the curing process. After curing, wait for the mold to cool down and release the pressure inside the container. Then, separate the upper and lower molds through the demolding mechanism on the mold parting surface. At the same time, start the hydraulic ejection device to smoothly push the cured gas cylinder out of the molding container to obtain the finished high-pressure hydrogen storage composite gas cylinder.

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