Method for designing type III hydrogen tank

Abstract

The invention relates to a computer-implemented method of designing a gas tank comprising a thin metal liner defining a plenum for gas and surrounded by a composite housing. The gas tank is represented by a computer model, and for selected diameters, thicknesses and materials of the liner, design routines calculate composite material thicknesses and / or materials to achieve target fatigue requirements of the metal liner. The design routine includes the steps of: (a) calculating a tangential stress on the liner for the pressure cycle based on predetermined geometric characteristics and material characteristics of the gas tank; and (b) increasing the thickness and / or Young's modulus of the composite shell if the tangential stress on the liner is greater than the stress target of the liner material from the fatigue profile of the liner material, or if the tangential stress on the liner is below the opposite value of the yield stress of the liner material. Steps a) and b) are repeated until the tangential stress is less than or equal to the stress target of the liner material, or if the tangential stress is greater than or equal to the opposite value of the yield stress of the liner material, then the thickness and / or Young's modulus from the final repeating step is stored.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to a method for designing a Type III hydrogen tank, and more particularly to a method for optimizing the thickness of its composite shell to improve the tank's durability and minimize its weight. BACKGROUND

[0002] Pressure vessels are used in various technical fields to store fluids at a pressure significantly higher than atmospheric pressure, typically between 350 and 700 bars. Many applications, such as hydrogen tanks for the automotive industry, require pressure vessels to be as light as possible while being strong enough to ensure that the fluid is reliably and durably sealed therein.

[0003] Modern hydrogen tanks are generally cylindrical and can be classified into five types: Type I tanks are simple metal tanks, typically formed of a relatively thick aluminum or steel cylinder. Type II tanks are similar to Type I tanks and additionally comprise a winding of glass or carbon fiber around the metal cylinder. Type III tanks are made of a composite shell that tightly surrounds a relatively thin metal liner. The metal liner mainly ensures the sealing of the fluid inside the tank, while the composite shell bears most of the mechanical load generated by the internal pressure. Type IV tanks are similar to Type III tanks but have a polymer liner instead of a metal liner. Finally, Type V tanks are fully composite tanks without a liner.

[0004] Type III and IV tanks have been considered for storing hydrogen in the context of motor vehicles. Indeed, the tanks need to undergo a homologation test with specific pressure cycle requirements. While Type IV tanks with plastic liners easily pass the test, this is not the case for Type III tanks, especially for 700 bar applications.

[0005] Therefore, Type III tanks are known to be prone to leaks and are thus considered unsuitable for some applications in the automotive industry. Indeed, during the homologation test, the pressure cycles generate fatigue behavior which eventually leads to the formation and subsequent propagation of cracks within the liner, enabling the pressurized fluid to leak through. In hydrogen fuel vehicles, these leaks can have catastrophic consequences due to the flammability of the fluid and must be prevented.

[0006] TECHNICAL PROBLEM

[0007] The object of the present invention is to provide a Type III hydrogen tank that can withstand high pressures, has no leaks throughout its lifetime, and is as light as possible.

[0008] This object is achieved by a method for designing a Type III hydrogen tank as claimed in claim 1. SUMMARY

[0009] This invention relies on the inventors’ discovery that the leading criterion for defining the thickness of composite materials in Type III tanks should be the fatigue requirements of the lining material, rather than the static burst pressure.

[0010] Therefore, the present invention provides a computer-implemented method for designing a gas tank, wherein the tank includes a thin metal liner defining a filling chamber for gas and surrounded by a composite shell, wherein the gas tank is represented by a computer model, and wherein, for selected diameter, thickness, and material of the liner, design routines calculate the composite thickness and / or material to achieve target fatigue requirements for the metal liner. Specifically, the computer routines are configured to run a simulation using the computer model by applying predetermined pressure cycles.

[0011] Therefore, the present invention provides a design method in which a composite stiffness is determined by computer simulation, enabling the metal liner to meet predetermined (target) fatigue requirements without failure. These fatigue requirements will be set according to the application and, in particular, will satisfy the pressure cycles of isomorphic testing.

[0012] The method of the present invention advantageously uses a computer model to perform iterative simulations, wherein at least one composite shell parameter is modified until the determined (maximum) tangential stress σ of the metal liner is reached. θ This corresponds to the fatigue stress target obtained from fatigue curves (SN curves, such as Wöhler curves). The simulation is performed for a predetermined pressure cycle, i.e., with a defined pattern or pressure peak. The simulation / iteration is preferably performed by varying the thickness and / or Young's modulus of the composite shell. At the end of the simulation, the obtained thickness values ​​(Young's modulus, respectively) can be used to manufacture the gas tank.

[0013] Preferably, the design routine includes the following steps:

[0014] (a) Calculate (simulate) the tangential stress on the lining under pressure cycling based on the predetermined geometric and material properties of the gas tank;

[0015] (b) If the tangential stress on the lining is greater than the stress target of the fatigue curve of the lining material, or if the tangential stress on the lining is less than the opposite value of the yield stress of the lining material, then increase the thickness and / or Young's modulus of the composite shell.

[0016] Steps a) and b) are repeated until the tangential stress is less than or equal to the stress target of the lining material, or if the tangential stress is greater than or equal to the opposite value of the yield stress of the lining material; and

[0017] (c) Store the thickness and / or Young's modulus of the final repeating step from (a).

[0018] Therefore, the simulation provides values ​​for the thickness and Young's modulus of the composite shell. In practice, iterative processing is preferably performed by modifying only one of the thickness and Young's modulus. In particular, modifying only the Young's modulus may be advantageous because it avoids altering the geometry of the computer model.

[0019] In this context, iterative calculations can involve modifying the Young's modulus of the composite shell while keeping its thickness constant. After storing the final Young's modulus in step c), the corresponding final thickness is calculated based on the composite material with the initial Young's modulus. That is, an equivalent thickness is calculated for composite materials with an initially selected Young's modulus to provide the same stiffness behavior. This method allows for working with materials having actual Young's moduli.

[0020] The geometric and material properties used for the model / simulation include: lining inner diameter, lining material and thickness, yield stress of the lining material, and initial thickness of the composite shell.

[0021] The design routines can be configured to operate any appropriate strategy to reduce the tangential stress σ in the metal liner. θ The stress converges towards the target. For example, a bisection method can be applied in design routines.

[0022] In an embodiment, if in step b), the tangential stress on the lining is lower than the stress target minus a predetermined tolerance and higher than the opposite value of the yield stress of the lining material, then the thickness t2 or Young's modulus of the composite shell is reduced; and if the tangential stress on the lining is between the stress target minus the predetermined tolerance and the stress target and higher than the opposite value of the yield stress of the lining material, then step c) is performed.

[0023] In this embodiment, the metal liner and composite shell are cylindrical or capsule-shaped. The liner material can be selected from any suitable material, such as steel, stainless steel, nickel-based alloys, duplex steel, aluminum, aluminum alloys, titanium and / or titanium alloys.

[0024] In the embodiments, the composite shell is made of fiber-reinforced polymer, particularly a resin containing glass or carbon fiber.

[0025] In an embodiment, the initial thickness of the composite shell is calculated such that its radial strain at a predetermined pressure (typically burst pressure) is less than a given percentage, such as 1%, depending on the selected fibers. It can be noted that, based on the first results, the thickness of the composite material obtained by this method will generally be sufficient to resist the burst pressure, respectively, within the radial strain limits.

[0026] In one embodiment, the inner diameter of the lining is calculated for a given capacity of the tank.

[0027] In one embodiment, calculating the tangential stress on the lining material involves simulating pressure cycles using a computer model by performing finite element analysis, wherein the computer model is constructed to represent the cross-sections of the lining and the composite shell.

[0028] Finite element analysis can involve approximating the behavior of lining materials and composite shells. The behavior of the lining material can be approximated using the bientropic hardening law, and / or the behavior of the composite shell can be approximated using Hooke's law.

[0029] For a predetermined target number of pressure cycles, the stress target for the lining material can be determined from the point on the SN curve of the lining material corresponding to a failure probability of less than 10%. The predetermined target number of fatigue pressure cycles can include between 15,000 and 25,000, preferably approximately 20,000.

[0030] Preferably, a predetermined pressure cycle pattern is simulated for a modeled tank comprising at least three pressure peaks. The first pressure peak has a maximum pressure sufficient to cause the metal liner to plastically deform outward, thereby hardening the metal liner; this deformation is referred to as auto-stamping. The first pressure is greater than the nominal operating pressure.

[0031] The second peak preferably has a maximum pressure equal to that of the first pressure peak. Subsequent peaks, referred to as durability peaks, have maximum pressures less than those of the first and second pressure peaks. These subsequent pressure peaks may have maximum pressures between 80% and 150% of the nominal operating pressure, particularly 115% or 125%. In practice, a pressure cycling pattern may consist of five pressure peaks.

[0032] According to another aspect, the present invention provides a method for manufacturing a Type III gas canister having a thin metal liner defining a gas filling chamber and being surrounded by a composite shell, the method comprising the following steps:

[0033] The composite thickness and / or material is determined using the method according to any one of the preceding claims;

[0034] Type III gas cylinders are manufactured using the determined composite thickness and / or materials.

[0035] According to another aspect, the present invention provides a Type III gas tank manufactured using the present method for designing a gas tank and the method for manufacturing a Type III gas tank, respectively.

[0036] In particular, the present invention provides a Type III gas canister comprising a thin metal liner defining a gas filling chamber and being surrounded by a composite shell, wherein the composite thickness and / or material is designed to achieve target fatigue requirements of the metal liner. Attached Figure Description

[0037] Preferred embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

[0038] Figure 1 This is a schematic diagram showing the cross-section of a typical Type III tank;

[0039] Figure 2 A flowchart illustrating an embodiment of a method for designing a Type III hydrogen tank according to the present invention;

[0040] Figure 3 It is the Wöhler curve with a metal lining;

[0041] Figure 4 This is a representation of an example of the pressure peak pattern used in this method, where the pressure varies with time;

[0042] Figure 5 It is a graph of the stress on the metal liner during the first iteration of the method of the present invention;

[0043] Figure 6 This is a graph showing the stress on the metal liner during the final iteration of the method of the present invention. Detailed Implementation

[0044] Figure 1 The schematic diagram shows a Type III hydrogen tank 1, which has a cylindrical shape and includes a cylindrical metal liner 3 surrounded by a cylindrical composite shell 5. The metal liner 3 and the composite shell 5 are hollow, thereby defining an filling chamber 7 within their internal volume. Although not shown, the hydrogen tank 1 is closed at both ends (the base of the cylinder) and also includes at least one orifice disposed at one base to fluidly connect the filling chamber 7 to the vehicle's fuel delivery circuit.

[0045] The metal liner 3 is relatively thin, having a thickness t1, and can be made of any suitable metal, such as aluminum, aluminum alloys, steel, stainless steel, titanium and / or titanium alloys, nickel-based alloys, etc. The liner is typically formed as a cylinder closed at both ends, for example by a semi-domed attached to the ends of the cylinder in a sealing manner. One of the domes has an opening with a fixed boss. This metal cylinder can be manufactured by deep extrusion. Alternatively, the liner can be manufactured by additive manufacturing, particularly with aluminum (or aluminum alloys), as a single piece (cylinder + end domes). This is merely an example of liner construction and should not be construed as limiting.

[0046] Conversely, the composite shell 5 is thicker, with a thickness of t2, and is typically made of a fiber-resin matrix material. The composite shell is usually formed by wrapping a continuous resin-coated filament around the liner. The filament / fiber can be, for example, glass fiber or carbon fiber. Thus, the composite material is wrapped and cured in place, providing close contact with the liner. Any suitable composite composition and application technique can be used.

[0047] The primary function of the metal liner 3 is to fluidly seal the volume of the inflation chamber 7 relative to the atmosphere. Due to its low thickness t1, the metal liner 3 itself does not absorb the load caused by the high pressure within the inflation chamber 7. Instead, the metal liner 3 is tightly surrounded by the composite shell 5, which bears most of the mechanical load generated by the pressure within the inflation chamber 7.

[0048] In theory, as long as the burst pressure of the composite shell 5 is greater than the maximum pressure applied in tank 1, tank 1 should be able to ensure a fluid seal. However, in practice, it has been observed that typical Type III tanks begin to leak after repeated use because fatigue of the metal liner 3 generates and propagates cracks in the latter.

[0049] To address this problem, the inventors have proposed a method for designing a Type III hydrogen tank, the flowchart of which is shown below. Figure 2 As shown. The exemplary application of method 10 of the present invention will be described in detail below using purely arbitrary and non-limiting numerical values.

[0050] This method can be implemented using any computer (data processing) system that includes at least one processor. The computer includes at least one computer program (i.e., code instructions) capable of performing simulations of physical phenomena, particularly based on the finite element method, or FEA. According to this method, the program / processor is configured to implement design routines that include iterative pressure cycles designed to achieve target fatigue requirements for the metal liner. Conventional FEA programs allow for the construction of computer models and the running of simulations with customized routines.

[0051] Prior to the simulation step, several geometric and material properties of the gas tank are determined.

[0052] First, select the capacity of 12 cans 1, that is, the volume V of the filling chamber 7. PC And calculate the corresponding inner diameter d1 of 14 lining 3. The tank length can be predefined or selected by the user.

[0053] As used in this article, the term “selected” or “choose” generally refers to a given value or parameter that a user typically defines by entering a value via a user interface or by selecting from predefined values.

[0054] Then, a 16-layer lining material M1 and a thickness t1 are selected, and its behavior is approximated using suitable methods known in the art, such as the bilinear isentropic hardening law (common in FEA software). Therefore, the method involves automatically selecting or allowing user selection of one or more bilinear isentropic hardening law models based on material M1. The bilinear isentropic hardening law typically requires Young's modulus E1, tangent modulus G1, Poisson's ratio ν1, and yield stress σ of the lining material M1. e and ultimate stress σR This data can be retrieved from a database or entered by the user.

[0055] In the next step, the stress target σ d The fatigue curve is determined by the fatigue curve corresponding to the lining material.18 The fatigue curve is typically a so-called SN curve (or graph), which plots the relationship between material stress and the number of cycles leading to failure, such as... Figure 3 As shown. Preferably, the SN curve is the Wöhler curve of the lining material (e.g., given for a failure probability of no more than 50%, more preferably 10%). For example, the stress corresponding to a 10% failure probability after 20,000 cycles can be selected as the target stress σ. d .

[0056] In step 20, a composite material and geometry are selected whose behavior is approximated using suitable methods known in the art, such as Hooke's law, which requires the composite material's Young's modulus E2, Poisson's ratio ν2, and yield stress.

[0057] In step 22, the initial thickness of the composite material is calculated based on the selected maximum pressure value or based on other characteristics, such as the maximum radial strain at a predetermined pressure. Conventional methods known in the art can be used. For example, the following formula from the "ROARK Formula for Stress and Strain" (McGraw-Hill International Edition, 6th Edition) can be used:

[0058]

[0059] Where b is the inner radius of the composite material (corresponding to the outer radius of the liner), ∆b is the change of b in response to the applied pressure q, and a is the outer radius of the composite material.

[0060] For a predetermined radial strain ∆b / b, the thickness t2 of the composite material can then be obtained from the following:

[0061]

[0062] in

[0063] Once these steps are completed, a 24-factory-analysis (FEA) model is constructed using the dimensions, materials, and behavior of the liner and composite shell. Preferably, a simplified FEA model is used, which simulates the cross-section of a tank with two distinct bodies (i.e., a metal liner and a composite shell), such as... Figure 1 As shown.

[0064] Once the FEA model is configured, the simulation begins by applying pressure cycles (based on a predetermined pressure cycle pattern) to the inner diameter of bushing 26. Most known FEA simulation software, such as Ansys, can be used. Because the model is rotationally symmetric, it is advantageous to align the model to a single quadrant (in... Figure 1 The part represented as Q) performs FEA simulation, thereby reducing computation time.

[0065] For each iteration, the following results are extracted from the FEA model simulation, step 28, and are expressed as follows:

[0066] - von Mises stress σ v , which represents the yield standard of the material;

[0067] - Radial stress σ r It is always compressive stress, and

[0068] - Tangential stress σ θ This includes compressive and tensile stresses.

[0069] These three stresses are mapped relative to the time of the pressure cycle (i.e., for each pressure peak). It should be understood that the relevant stress values ​​are the peak or maximum stress values ​​for each pressure peak.

[0070] Preferably, the radial and tangential stresses are represented relative to a cylindrical coordinate system (R, θ) centered on the central axis of the tank.

[0071] A pressure cycle can include a predetermined number of steps (i.e., pressure peaks), which can be performed at the same or different pressures, forming a pressure cycle pattern.

[0072] For example, such as Figure 4 As shown, the proposed pressure cycling pattern includes a first pressure peak, the maximum pressure of which is sufficient to cause the metal liner to plastically deform outward, thereby hardening the metal liner (so-called automatic stamping). Typically, the pressure cycling pattern also includes a second pressure peak with a maximum pressure equal to the first pressure peak, followed by multiple pressure peaks with maximum pressures less than the first and second pressure peaks. Third and subsequent peaks may correspond to predetermined pressures, such as between 80% and 150% of the nominal operating pressure, particularly 115% or 125%.

[0073] For simulation purposes, pressure cycling patterns typically include at least three pressure peaks: the self-pressure peak, the validation pressure peak, and the durability pressure peak. Pressure cycling patterns may also include several consecutive durability pressure peaks to verify system stability. However, it should be understood that this method naturally leads to a stable system, therefore a large number of cycles is not necessary: ​​a cycle with five peaks (three durability pressure peaks) is usually sufficient.

[0074] In the following text, it depends on the tangential stress σ θ The determined value is used to further simulate the iteration of the pressure cycle (using a predetermined pattern). As shown in rhombus 30, the stress target σ is... d The maximum value σ compared to θ The yield stress σ of the lining material is generated e .

[0075] If the tangential stress σ on the lining θ Higher than the target stress σ d And / or the opposite value of the yield stress of the lining material, then increase at least one of the thickness t2 of the composite shell and the Young's modulus E2.

[0076] If the tangential stress σ on the lining θ Below the target stress σ d Subtracting the predetermined tolerance and the opposite value of the yield stress of the lining material, at least one of the thickness t2 of the 32' composite shell t2 and the Young's modulus E2 is reduced.

[0077] If the tangential stress σ on the lining θ Includes subtracting the predetermined tolerance and the target stress σ from the target stress. d If the values ​​are between and greater than the opposite value of the yield stress of the lining material, then the method concludes that the final thickness t2' and Young's modulus E2' of the composite shell are suitable for the selected lining and store them, and the above values ​​are stored (34).

[0078] For tangential stress σ θ These comparisons are advantageously targeted at all durability pressure peaks and possibly at the second peak. Therefore, preferably, for all determined tangential stresses σ in the pressure cycling mode... θ Compare, except for the first pressure peak. If for at least one of these peaks, the tangential stress σ θ If the comparison indicates that the thickness t2 or Young's modulus E2 should be modified, then a new iteration is performed.

[0079] Only when all tangential stresses σ in the pressure cycling mode θ (Except for the first peak) is included in the stress target minus the predetermined tolerance and the stress target σ. d The iteration loop stops and the obtained value is stored only when the value is between and higher than the opposite value of the yield stress of the lining material (step 34).

[0080] Preferably, the iterative pressure cycling involves modifying the Young's modulus E2 of the composite shell while keeping its thickness t2 constant. Then, after the final iteration, i.e., once the final Young's modulus E2' is stored, the corresponding final thickness t2' is calculated such that the composite material with Young's modulus E2 and thickness t2' exhibits the same inner radius deformation under internal pressure as the composite material with Young's modulus E2' and thickness t2. Advantageously, this design process allows for the calculation of the final thickness t2' without modifying the geometry of the FEA model at each iteration (instead of by modifying the value of Young's modulus), thus simplifying the iterative workflow and saving computation time. It also allows for the design of tanks with predefined actual Young's moduli.

[0081] <Numerical Example>

[0082] The following provides an exemplary implementation of this method for designing a Type III tank with a nominal working pressure of 700 bar.

[0083] Select a metal liner made of 1050H19 aluminum with an inner diameter d1 = 119.5 mm and a thickness t1 = 0.5 mm, and retrieve the following liner parameters from the database:

[0084] - Young's modulus of metal (E, unit MPa): E1 = 70500 MPa

[0085] - Tangential modulus of metal lining (G, unit MPa): G1 = 491 MPa

[0086] - Poisson's ratio (ν): ν1 = 0.3

[0087] - Yield stress (σ e (unit: MPa): σ e =165 MPa

[0088] - Final stress (σ) r (unit: MPa): σ R =175 MPa

[0089] For a target cycle count of 20,000 cycles, a target stress σ of 90 MPa is derived from the Wöhler curve (failure probability 10%) for aluminum grade 1050H19. d .

[0090] Test pressure = 150% of nominal working pressure = 1050 bar

[0091] Durability pressure = 125% of nominal working pressure = 875 bar

[0092] Select a composite material of carbon fiber and epoxy resin with the following parameters:

[0093] - Carbon fiber - Young's modulus: E = 221000 MPa, and

[0094] - Epoxy group - Young's modulus: E = 3120 MPa

[0095] - Fiber content = 60%

[0096] - Composite Young's modulus E2 = 133848 MPa

[0097] - Poisson's ratio: ν² = 0.3

[0098] The initial composite material thickness t2 was then calculated such that, for a given burst pressure of 1750 bar, the maximum strain on the inner diameter did not exceed 1%. Using the aforementioned equation, the thickness t2 was calculated to be 11.3 mm.

[0099] Based on these parameters, construct the FEA model, and then use the following pattern (corresponding to) in each iteration. Figure 4 Apply pressure to it in cycles:

[0100] - First peak value q = 1050 bar ('self-pressure' peak value = verification pressure)

[0101] - The second peak value q = 1050 bar (verification pressure)

[0102] - The third to fifth peak values ​​are q = 875 bar (durability pressure).

[0103] exist Figure 5 and Figure 6 The resulting stresses on the lining used for the initial and final iterations are plotted above. Figure 5 The region R on the map indicates that the tangential stress exceeds an acceptable threshold, i.e., where the tangential stress σ θ Exceeding the target stress σ d or σ θ Below -σ e (The opposite value of yield stress).

[0104] In each iteration, the Young's modulus E2 of the composite shell is modified while its thickness t2 remains constant until a suitable final value is found, denoted as E2'. Using the above value, the value E2' = 150579 MPa is obtained.

[0105] Then, the corresponding final thickness t2' is calculated such that the composite material with Young's modulus E2 and thickness t2' has the same inner radius deformation under internal pressure as the composite material with Young's modulus E2' and thickness t2. Using the previously mentioned equation again, we finally obtain t2' = 13.5 mm.

Claims

1. A computer implementation method for designing a gas tank, wherein the tank includes a thin metal liner defining an inflation chamber for gas and surrounded by a composite shell, wherein the gas tank is represented by a computer model, and wherein, for selected diameter, thickness, and material of the liner, design routines calculate the thickness and / or material of the composite material to achieve target fatigue requirements of the metal liner.

2. The method of claim 1, wherein the design routine performs iterative simulations using the computer model, wherein at least one composite shell parameter is modified until the determined tangential stress σ of the metal liner is achieved. θ This corresponds to the stress target obtained from the fatigue curve.

3. The method according to claim 2, wherein the design routine includes the following steps: (a) Calculate the tangential stress on the lining under pressure cycling based on the predetermined geometric and material properties of the gas tank; (b) If the tangential stress on the lining is greater than the stress target of the fatigue curve of the lining material, or if the tangential stress on the lining is less than the opposite value of the yield stress of the lining material, then increase the thickness and / or Young's modulus of the composite shell. Steps a) and b) are repeated until the tangential stress is less than or equal to the stress target of the lining material, or if the tangential stress is greater than or equal to the opposite value of the yield stress of the lining material, then steps a) and b) are repeated. (c) Store the thickness and / or Young's modulus obtained from the final repeated step (a).

4. The method according to claim 3, wherein the geometric and material properties include: Lining inner diameter, lining material and thickness, and yield stress of the lining material; And the initial thickness of the composite shell.

5. The method according to claim 2 or 3, wherein in step b), if the tangential stress on the lining is lower than the stress target minus a predetermined tolerance and higher than the opposite value of the yield stress of the lining material, then the thickness or Young's modulus of the composite shell t2 is reduced, and If the tangential stress on the lining is between the stress target minus the predetermined tolerance and the stress target, and is higher than the opposite value of the yield stress of the lining material, then step c is performed.

6. The method according to any one of the preceding claims, wherein the calculation, iteration, and looping involve modifying the Young's modulus of the composite shell while maintaining its thickness constant, and After storing the final Young's modulus in step c), the corresponding final thickness is calculated based on the composite material with the initial Young's modulus.

7. The method according to any one of the preceding claims, wherein the metal liner and the composite shell are cylindrical or capsule-shaped.

8. The method according to any one of the preceding claims, wherein the lining material is selected from steel, stainless steel, nickel-based alloys, duplex steel, aluminum, aluminum alloys, titanium and / or titanium alloys.

9. The method according to any one of the preceding claims, wherein for a liner inner diameter of 700 mm or less, the metal liner has a thickness of 5 mm or less, preferably wherein for a liner inner diameter of 200 mm or less, the metal liner has a thickness of 1 mm or less.

10. The method according to any one of the preceding claims, wherein the composite shell is made of a fiber-reinforced polymer, particularly a resin having glass or carbon fibers.

11. The method according to any one of the preceding claims, wherein the initial thickness of the composite shell is calculated such that its radial strain under a predetermined pressure is less than a given percentage, for example, 1%.

12. The method according to any one of the preceding claims, wherein the inner diameter of the lining is calculated based on the selected capacity of the tank.

13. The method according to any one of the preceding claims, wherein calculating the tangential stress on the lining material involves simulating pressure cycles using a computer model by performing finite element analysis, wherein the computer model is constructed to represent the cross-section of the lining and the composite shell.

14. The method of claim 13, wherein the finite element analysis relates to approximating the behavior of the lining material and the composite shell.

15. The method of claim 13, wherein the behavior of the lining material is approximated using the bilinear isentropic hardening law, and / or wherein the behavior of the composite shell is approximated using Hooke's law.

16. The method according to any one of the preceding claims, wherein the stress target of the lining material is determined from the point on the SN curve of the lining material corresponding to a failure probability of less than 10% for a predetermined target number of pressure cycles.

17. The method of claim 16, wherein the predetermined target number of pressure cycles comprises between 15,000 and 25,000, preferably about 20,000.

18. The method according to any one of the preceding claims, wherein a simulation is performed for a predetermined pressure cycling pattern comprising at least three pressure peaks, wherein a first pressure peak has a maximum pressure sufficient to cause the metal liner to plastically deform outward, thereby hardening the metal liner.

19. The method of claim 11, wherein the pressure cycle further comprises a second pressure peak with a maximum pressure equal to the first pressure peak, followed by a plurality of pressure peaks with a maximum pressure less than the first pressure peak and the second pressure peak.

20. A method for manufacturing a Type III gas canister, the Type III gas canister having a thin metal liner defining a filling chamber for gas and surrounded by a composite shell, the method comprising the steps of: The composite thickness and / or material is determined using the method according to any one of the preceding claims; Type III gas cylinders are manufactured using the determined composite thickness and / or materials.

21. A Type III gas canister comprising a thin metal liner defining a gas filling chamber and surrounded by a composite shell, wherein the composite thickness and / or material is designed to achieve target fatigue requirements of the metal liner.

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