Polymer Liner Research Articles

Analysis of rapid decompression failure in polymer liner of Type IV hydrogen storage vessels using a novel fluid–solid coupling model

Type IV vessels have been developed for hydrogen storage systems, but the rapid decompression failure during the decompression process can lead to the collapse of the liner, significantly reducing the lifespan of the vessels. This study aims to investigate nonlinear buckling behaviors and collapse mechanisms of polymer liner in Type IV hydrogen storage vessels. Considering the intrinsic coupling between hydrogen gas depletion and mechanical behavior of vessels, a fluid–solid coupling model was proposed using the fluid cavity techniques and HyperMesh. Results indicated that the pressure difference generated on the liner is the primary cause leading to the polymer liner collapse. The critical pressure difference significantly increases with the thickness of the liner, while it decreases nonlinearly with the increase in void defect size. Parametric sensitivity analysis highlighted the depth of initial void defect and the liner thickness as two significant influencing factors in the critical decompression rate.

Molecular investigation on physical and tensile properties of polyethylene (PE) under high-pressure hydrogen environments

Polymer liners are key components of high-pressure hydrogen storage tanks, and understanding their behaviour under such environments is crucial for safety. This study employs molecular dynamics (MD) simulation to investigate the physical and tensile properties of amorphous polyethylene (PE) under the effects of hydrogen content, pressure, temperature. It is found that hydrogen molecules decrease glass transition temperature by approximately 3%, while pressure have no noticeable impact. Meanwhile, hydrogen molecules enhance diffusivity, while pressure suppresses diffusivity and exhibits a more pronounced impact, resulting in an overall decrease of 44% in diffusivity under high-pressure hydrogen. Tensile stress also increases the diffusivity by 17%. Hydrogen molecules weaken the non-bonded molecular interactions of PE, which reduces the percentage of trans conformation and orientation parameters. Meanwhile, hydrogen also suppresses the internal energy change of PE induced by tensile deformation. Therefore, hydrogen molecules lead to a decrease in tensile properties. Comparatively, pressure causes PE to produce more trans conformations under tension, which improves orientation, entanglement parameters, and the internal energy change of PE, and finally enhances the tensile properties of PE. The effect of pressure surpasses that of hydrogen, which results in an approximately 40% increase in tensile properties under high-pressure hydrogen. This study provides molecular-level insights into the individual and coupled effects of hydrogen and pressure, forming a foundation for predicting polymer behaviour under high-pressure hydrogen conditions.

Effects of hydrogen cycling on the performance of 70 MPa high-pressure hydrogen storage tank liners formed by different processes

Current research on the compatibility between plastic liners utilized in Type IV high-pressure hydrogen storage containers and hydrogen remains insufficiently comprehensive. Therefore, further exploration into how the high-pressure hydrogen storage process influences the crystalline phase transition of polymers is essential to improve the applicability and safety of plastic lining materials. This study primarily investigated the preparation of polyamide 1012 (PA1012) and polyamide 11 (PA11) through rotational molding and injection molding, denoted as Roto-PA1012/Roto-PA11 and In-PA1012/In-PA11, respectively. Considering the operational parameters of the 70 MPa Type IV hydrogen storage tank, we conducted hydrogen cycling experiment using the long carbon chain polyamide (LCPA) liner materials and comprehensively analyzed the morphology, crystal structure, grain size, mechanical properties and hydrogen barrier properties of polyamide materials before and after hydrogen cycling. The results showed that after hydrogen cycling, no significant changes were observed in Roto-PA1012/Roto-PA11, while In-PA1012/In-PA11 demonstrated severe foaming. Rotational molding of LCPA maintained stable mechanical and hydrogen barrier properties throughout the hydrogen cycle, which can be attributed to the favorable thermodynamic stability of the α' form achieved during rotational molding, leading to uniform and stable crystal sizes. In conclusion, this study provides a theoretical foundation for future investigations into the molding process and material selection of high-barrier polymer liners, as well as the actual production and utilization of Type IV hydrogen storage tanks.

Design of Silicon Core Coaxial TSVs to Reduce Crosstalk Effects for 3D IC Applications

This paper presents the effectiveness of the copper (Cu)-based coaxial through silicon vias (CTSVs) to reduce crosstalk noise and propagation delay. In the proposed CTSVs, the polymer liners are used as insulating material which cancels the crosstalk functional failures. The impacts of the proposed CTSVs on the electrical performance are noticed for different parameters and properties of the material. Simulations of the proposed CTSVs are executed using the standard HSPICE and SYMICAD tools. The results indicated that the effects of crosstalk are reduced using the polymer liners instead of silicon dioxide (SiO2) liners in the proposed CTSVs. The electrical performances of the proposed CTSVs are investigated for various thicknesses of Cu and BCB. Furthermore, a comparative study has been carried out for the SiO2 and benzocyclobutene (BCB) liners. It is observed that BCB liner-based CTSVs crosstalk noise and delay values are reduced by up to 25.06% and 27.8% compared to the SiO2 liner-based TSVs.

Molecular Dynamics Simulation of Hydrogen Barrier Performance of Modified Polyamide 6 Lining of IV Hydrogen Storage Tank with Graphene.

The polymer liner of the hydrogen storage cylinder was studied to investigate better hydrogen storage capacity in Type-IV cylinders. Molecular dynamics methods were used to simulate the adsorption and diffusion processes of hydrogen in a graphene-filled polyamide 6 (PA6) system. The solubility and diffusion characteristics of hydrogen in PA6 systems filled with different filler ratios (3 wt%, 4 wt%, 5 wt%, 6 wt%, and 7 wt%) were studied under working pressures (0.1 MPa, 35 MPa, 52 MPa, and 70 MPa). The effects of filler ratio, temperature, and pressure on hydrogen diffusion were analyzed. The results show that at atmospheric pressure when the graphene content reaches 5 wt%, its permeability coefficient is as low as 2.44 × 10-13 cm3·cm/(cm2·s·Pa), which is a 54.6% reduction compared to PA6. At 358 K and 70 MPa, the diffusion coefficient of the 5 wt% graphene/PA6 composite system is 138% higher than that at 298 K and 70 MPa. With increasing pressure, the diffusion coefficients of all materials generally decrease linearly. Among them, pure PA6 has the largest diffusion coefficient, while the 4 wt% graphene/PA6 composite system has the smallest diffusion coefficient. Additionally, the impact of FFV (free volume fraction) on the barrier properties of the material was studied, and the movement trajectory of H2 in the composite system was analyzed.

Automated manufacture and experimentation of composite overwrapped pressure vessel with embedded optical sensor

In recent years, the mobility (air/land) industry has been developing fuel-cell vehicles for mass adoption as hydrogen technology matures. Compared to conventional metallic design, the composite overwrapped pressure vessel without a metal or polymer liner results in a lightweight solution for gaseous hydrogen storage which further improves fuel efficiencies. Since the capabilities of automated fiber placement for making multi-stiffened structures are distinct from other automated manufacturing techniques, this study aimed to evaluate the feasibility of implementing AFP into the manufacture of a small scale COPV with a partially composite liner. The manufacturing related challenges are identified and discussed. During the manufacturing process, Distributed fiber optic sensor was embedded between the plies, as a structural health monitoring solution, to monitor the mechanical performance of the pressurized tank. In addition, finite element study was done to predict the internal strains for different pressure levels and the measured experimental strains at the sensor's location are found to be in close agreement with the finite element results. It is shown that such sensors can be integrated into automated fiber placement manufactured tanks for internal strain monitoring.

Rational design of semi-interpenetrating network based on hyperbranched polyglycerol grafted MXene/polyurethane–epoxy for compressed hydrogen storage

Hydrogen (H2) energy has emerged as a promising alternative in the automotive sector to replace fossil fuel; however, its storage with volumetric efficiency remains a challenge. The latest type IV storage vessel featuring a polymeric liner with composite overwrap incurs hydrogen saturation, which eventually causes failure. To prevent the H2 dissolution in the liner, we have developed a barrier coating comprised of polyurethane/epoxy semi-interpenetrating network (S-IPN) combined with hyperbranched polyglycerol grafted MXene (h-MXene). The hyperbranched structure facilitated the dispersion of MXene in the coating solution by enhancing the exfoliation and improved the polymer filler interaction by forming covalent and H-bonding through end-terminal hydroxyl groups. Leveraging the dense network of S-IPN combined with the dispersed layer structured h-MXene significantly increased the tortuosity of the spray-coated barrier film applied to the nylon 6 liner. The coating exhibited a 90 % reduction in the H2 gas permeability at only 2 wt% h-MXene concentration, which further improved to above 98 % at 10 wt% loading. Additionally, the h-MXene considerably improved the adhesion with the liner even in a highly stretched condition, signifying the durability of the coating under cyclic pressurization and depressurization of the storage vessel.

Distributed fiber optic strain sensing for structural health monitoring of 70 MPa hydrogen vessels

We report on the development and testing of 70 MPa hydrogen pressure vessels with integrated fiber optic sensing fibers for the automotive use. The paper deals with the condition monitoring of such composite pressure vessels using the optical backscatter reflectometry (OBR) which was applied for a distributed fiber optic strain sensing along fully integrated polyimide-coated single-mode glass optical fiber (SM-GOF). The sensing fibers were embedded into the vessel structure by wrapping them over the inside polymer liner during the manufacturing process of the outside carbon fiber reinforced polymer (CFRP). Detecting local strain events by the integrated fiber optic sensors might be an opportunity for monitoring the material degradation. Regarding the investigation of the ageing behavior, both ambient hydraulic cycling tests and slow burst tests were conducted on 70 MPa pressure vessels with embedded fiber optic sensors. The achieved results contribute to the knowledge about material fatigue to guarantee the safe usage during the entire lifetime of the composite hydrogen storage vessels. The presented work stands in context of the European Horizon 2020 research project SH2APED focused on the development of an innovative hydrogen storage system composed of an assembly of nine 70 MPa tubular pressure vessels used as an automotive battery pack.

Study of the Failure Mechanism of a High-Density Polyethylene Liner in a Type IV High-Pressure Storage Tank.

The use of Type IV cylinders for gas storage is becoming more widespread in various sectors, especially in transportation, owing to the lightweight nature of this type of cylinder, which is composed of a polymeric liner that exerts a barrier effect and an outer composite material shell that primarily imparts mechanical strength. In this work, the failure analysis of an HDPE liner in a Type IV cylinder for high-pressure storage was carried out. The breakdown occurred during a cyclic pressure test at room temperature and manifested in the hemispherical head area, as cracks perpendicular to the liner pinch-off line. The failed sample was thoroughly investigated and its characteristics were compared with those of other liners at different stages of production of a Type IV cylinder (blow molding, curing of the composite material). An examination of the liner showed that no significant chemical and morphological changes occurred during the production cycle of a Type IV cylinder that could justify the liner rupture, and that the most likely cause of failure was a design-related fatigue phenomenon.

Investigation of Hydrogen Transport Properties through the Liner Material of 70 MPa Type IV Composite Overwrapped Pressure Vessels

In zero-emission solutions for the hydrogen supply chain, high-pressure hydrogen storage in Type IV composite overwrapped pressure vessels (COPVs) is crucial for being safe and secure for a variety of stationary and transport applications. These COPVs consist of a polymeric liner material that works as a barrier for the stored hydrogen, while the carbon fiber-based composite provides the strength to hold the high-pressure hydrogen (of nominal working pressure more than 70 MPa to achieve the competitive driving range). Several experimental studies and simulation work have been performed on the viability of various polymers as low-permeability materials under low-pressure conditions. However, because of their proprietary nature and commercialized research, the characteristics of hydrogen permeation through polymers and their behavior at high pressure are still readily available in the literature. It is a major concern and the most crucial component of Type IV COPVs that these polymeric liners hold high pressure and maintain the necessary density of hydrogen (state of charge) toward operational requirements and safety concerns related to the cause of failures due to permeation (such as blistering, buckling, cracking, and so on). This paper investigates the role of polymeric liners on hydrogen permeation behavior using finite element modeling. For this, a UMATHT subroutine is developed within the Abaqus software to implement a new hydrogen permeation transport model with extended governing equations. Through the simulations and material modeling, the role of hydrogen transport properties (permeability, diffusivity, and solubility), structural characteristics (crystallinity, free volume, thickness) of plastic liners, and the role of operational parameters (concentration, pressure) are combined to validate the model from the experimental data in the literature to estimate the effective thickness required to maintain the permeation limit of the polymeric liner of 70 MPa Type IV COPVs.

Using EPS and CFRP liner to strengthen prestressed concrete cylinder pipe

The prestressed concrete cylinder pipe (PCCP) with broken wires should be strengthened to maintain the safe operation of the pipeline. A new reinforcement technology is proposed in this study: expanded polystyrene (EPS) + carbon fiber reinforced polymer (CFRP) liner. The innovative method allows CFRP to bear the internal pressure prior to PCCP, greatly improving the reinforcement effect of the pipe. A three-dimensional finite element model is established and assessed by the experimental results. Then, the mechanical properties of the PCCP when subjected to different pressures and wire breakage are analyzed under three conditions (i.e. no strengthen, strengthened by only CFRP liner, and strengthened by EPS+CFRP liner). And the improvement effect of the innovative technology on the PCCP's bearing capacity compared with the traditional method is studied. The results showed that when repaired by 8-layer CFRP liner only and EPS and 6-layer CFRP composite liner, the internal pressure bearing capacity of PCCP can be increased by 9.17% and 50.83%, respectively. Based on the elastic limit state of the pipe, the wire breakage threshold of PCCP is 65 and 89 under the cases of no repair and CFRP liner repair. For the case of EPS + CFRP liner repair, when the number of broken wires is 100, the steel cylinder does not yield.

Impact response of filament-wound structure with polymeric liner: Experimental and numerical investigation (Part-A)

Filament wound pipelines and Type IV composite pressure vessels (CPVs) constitute polymeric liners and are extensively used to transport and store petroleum products, hydrogen, and compressed natural gas (CNG). The polymeric liner does not share much pressure load; hence, the composite layers share most of the load. The situation gets worse under transverse impact loads on such structures. For the polymeric liner to be effectively used in pipelines and CPVs, it is crucial to study impact response through testing and computational methods. This article presents experimental and numerical investigations of the transverse low-velocity impact response of filament wound samples. High-density polyethylene (HDPE) liner was adopted, and carbon fiber (T700) continuous filaments with epoxy resin were wound over the liner with several layers. A drop-weight impact loading with 40 J energy has been applied to the fabricated samples. The development of impact damage was assessed using the finite element method, and the damage modes have been discussed. The specimen remains unperforated at the chosen energy level. Though HDPE is ductile, however at impact loads liner damage was encountered, displaying a brittle fracture. At higher strain rates, the material reaches its brittle fracture point sooner, leading to failure. The material breaks as brittle due to its inability to dissipate impact energy quickly, resulting in fracturing instead of deformation. Fiber damage was scarcely seen; however, matrix damage has been the dominant failure mode at the chosen impact energy. Comparisons between the simulation and test findings were made, and they agreed on force-time and force-displacement histories.

Influence of winding angles on hoop stress in composite pressure vessels: Finite element analysis

Various pressure vessels from Type I to Type IV are used to store hydrogen and compressed natural gas (CNG) at high pressures. The polymeric liner in Type IV composite pressure vessels (CPVs) does not share the load, unlike those with metallic liners (Type III); hence, the composite layers share the entire load. The winding angles play a crucial role in tailoring the pressure-bearing properties of CPVs. This study investigated the effect of fiber winding angles on the hoop stress in Type IV CPVs using finite element (FE) analysis, and the advantage of multi-angle winding was realized. Stress analysis is vital to ensure that the vessel can withstand the intended operating conditions without undergoing failure. A series of finite element analyses (FEA) was carried out using the Abaqus FE simulation software to study the behavior of an anisotropic fiber-reinforced CPV with varied winding schemes. A stress analysis was performed, and various winding schemes were compared for different cases. The hoop stress in various configurations was documented to assess and compare various winding configurations.

Prospects in the application of a frontally curable epoxy resin for cured‐in‐place‐pipe rehabilitation

AbstractPhotocurable acrylates and vinyl esters are among the most commonly used resins in cured‐in‐place‐pipe (CIPP) rehabilitation technology, as they impart excellent thermomechanical properties in composite pipes. In the quest for achieving a higher energy efficiency of the photo‐curing process in CIPP, the frontal polymerization technique is a viable alternative that requires a lower irradiation dosage coupled with exceptionally high curing speeds and depths. Herein, for the first time, we report the application of frontal polymerization in the rehabilitation of underground pipes using a newly developed frontally curable epoxy‐based resin (Trelleborg Self‐Curing*). The neat resin is characterized for degree of cure, glass transition temperature, and mechanical properties via FTIR, DMA, and tensile tests, respectively. In a comprehensive way, the properties are benchmarked against commercially available acrylate (Trelleborg Light Cure*) and vinyl ester (Trelleborg Rapid Cure*) resins to evaluate their applicability for CIPP. The results show a higher glass transition temperature and final monomer conversion for the frontally cured resin, which cures significantly faster than the reference resins under the same irradiation conditions. In proof‐of‐concept trials, the newly developed resin successfully cures polymeric liners in a PVC host pipe with 100% water tightness and without losing its structural integrity. Results from ring stiffness tests for cured composite pipes additionally show that liners cured with Trelleborg Self‐Curing* resin pass the minimum required Young's modulus for non‐pressure drainage pipes as per ASTM F1216. Thus, frontally curable epoxy‐based resins are a promising and competitive alternative to acrylates and vinyl esters in CIPP.

Non-Destructive Characterization of Cured-in-Place Pipe Defects.

Sewage and water networks are crucial infrastructures of modern urban society. The uninterrupted functionality of these networks is paramount, necessitating regular maintenance and rehabilitation. In densely populated urban areas, trenchless methods, particularly those employing cured-in-place pipe technology, have emerged as the most cost-efficient approach for network rehabilitation. Common diagnostic methods for assessing pipe conditions, whether original or retrofitted with-cured-in-place pipes, typically include camera examination or laser scans, and are limited in material characterization. This study introduces three innovative methods for characterizing critical aspects of pipe conditions. The impact-echo method, ground-penetrating radar, and impedance spectroscopy address the challenges posed by polymer liners and offer enhanced accuracy in defect detection. These methods enable the characterization of delamination, identification of caverns behind cured-in-place pipes, and evaluation of overall pipe health. A machine learning algorithm using deep learning on images acquired from impact-echo signals using continuous wavelet transformation is presented to characterize defects. The aim is to compare traditional machine learning and deep learning methods to characterize selected pipe defects. The measurement conducted with ground-penetrating radar is depicted, employing a heuristic algorithm to estimate caverns behind the tested polymer composites. This study also presents results obtained through impedance spectroscopy, employed to characterize the delamination of polymer liners caused by uneven curing. A comparative analysis of these methods is conducted, assessing the accuracy by comparing the known positions of defects with their predicted characteristics based on laboratory measurements.

Exploring fatigue characteristics of metallic boss-polymer liner adhesion in hydrogen storage tanks: Experimental insights post surface treatment

Progress in hydrogen fuel powered systems has been propelled by the implementation of secure, reliable, and cost-effective hydrogen storage and transportation technologies. The fourth category, distinguished by a polymer liner serving as a hydrogen diffusion barrier, fully encapsulated within a fiber-reinforced composite to bestow structural integrity, has garnered substantial attention from the automotive industry due to its lightweight nature and rational manufacturing process. The method of rotomolding has sparked interest among manufacturers due to its capability to directly bond the metallic component to the polymer substrate, specifically the liner, thus negating the need for welding and its attendant imperfections. In fact, a pivotal facet of fourth-generation hydrogen storage systems revolves around the interface connection between the polymer liner and the metallic boss, posing as a structural Achilles' heel. For the study's purposes, a scaled-down demonstrator was fabricated using rotomolding in which a nozzle-liner interface mimics the boss-liner interface of the actual system. This demonstrator was designed to facilitate the mechanical characterization of the interface under quasi-static and fatigue loading. The thermal cycling phases of rotational molding and the surface treatments undertaken have been optimized in order to enhance direct adhesion within the metal-polymer interface. This study commences by assessing the efficacy of two treatments (sandblasting and flaming) applied to the aluminum nozzle surface. Subsequently, we explore the adhesion microstructural and mechanical characteristics of the treated nozzle onto a medium-density polyethylene polymer (liner). Lastly, we delve into an exploration of the damage and fatigue behaviors endemic to the metal-polymer interface region. The obtained Wöhler curves disclose a linear trend for the metal-polymer interface. Moreover, the metal-polymer interface evinces heightened resilience against damage and fracture for sandblasted interfaces. This inquiry underscores the potency of innovative polymer-metal interfaces treatment in amplifying the reliability and robustness of hydrogen storage technology.

Degradation and damage analysis of composite pressure vessels via experimental modal analysis

For mobile gas storage systems, the application of type IV pressure vessels is state of the art. Type IV tanks consist of an inner polymer liner fully wrapped with fibre-reinforced plastic (FRP). Because of the complex fabric of the FRP as well as a difficulty estimable interaction behaviour between the single components under load, there are still no satisfying non-destructive testing methods to assess the current state of failure nor to estimate the level of degradation accurately and economically. At BAM division 3.5, analysing the ageing process of mobile composite pressure vessels is a major task to ensure safe usage over the whole lifetime. In this context, key aspects of our ongoing research activities are the invention of new test procedures and the development of accurate lifetime prediction models. In order to determine the level of degradation or damage, one meaningful non-destructive approach is to analyse the structural dynamic behaviour via an experimental modal analysis (EMA). Over the last few years, different types and sizes of composite pressure vessels have been tested in several research projects. The presented paper gives an insight into how to extract and interpret modal parameters and how to fit them to the results of residual strength tests.

Study of blister phenomena on polymer liner of type IV hydrogen storage cylinders

Type IV hydrogen storage cylinder is a rising high-pressure hydrogen storage equipment, which is composed of a polymer liner and a fully wrapped carbon fiber composite. It is found that local blisters occur on polymer liners after rapid depressurization tests during the research and development process. Some manufacturers choose to add adhesives at the liner-composite interface to avoid blisters. In order to study the effect of adhesives to the local blisters, two type IV cylinders have been manufactured and tested, in which one has adhesives at the interface and the other does not. The depressurization tests were conducted from around 70 MPa–2 MPa under various mass flow rates. Digital radiography (DR) and videoscope have been used to conduct post-test inspections. Finite element analysis (FEA) was performed to verify the effect of adhesives, as well as estimating the pressure differential at the interface based on test results. According to the results of the test and FEA results, the use of adhesives at the interface does not effectively prevent the occurrence of local blisters. However, it does serve to slow down the blister propagation though. The results also indicate that the mass flow rate plays a crucial role in affecting the size of the local blister. Furthermore, based on the test and FEA results, an estimation of the local pressure differential at the interface that causes local blister was made. During the post-test inspection, it was observed that the size of several blisters initially increased but eventually decreased over time. Additionally, adjacent blisters were observed to merge as a single larger blister after the hydrostatic test. These results provide valuable insights into the formation and behavior of local blisters, which can inform future research and practical applications in relevant fields.

Performance analysis of Cu-MWCNT bundled HCTSVs using ternary logic

This paper presents an investigation of crosstalk issues for coupled heterogeneous coaxial through silicon vias (HCTSVs) in ternary logic. Crosstalk issues are investigated for coupled HCTSVs using Cu-MWCNT as a conductive filler and polymer liners such as polyimide, polypropylene carbonate (PPC), and benzocyclobutene (BCB) as insulating materials. The electrical equivalent circuit model is utilized to investigate the crosstalk induced by the ternary inverter in coupled HCTSVs. The effects of crosstalk such as functional and dynamic crosstalk for proposed HCTSVs are compared with Multi-walled CNT (MWCNT) TSVs using Hewlett simulation program with integrated circuit emphasis (HSPICE) simulations. Other performance parameters are also investigated, including power dissipation, power delay product (PDP), and energy delay product (EDP). The proposed model's crosstalk effects are also investigated for various TSV heights. The BCB-based coupled Cu-MWCNT HCTSVs provide a significant improvement in crosstalk at reduced TSV height. The proposed HCTSVs also improved overall performance by 32.12% when compared to the MWCNT based TSVs. As a result, Cu-MWCNT based HCTSVs with BCB liner are better than conventional TSVs for ternary logic integrated circuits (ICs).

Review of common hydrogen storage tanks and current manufacturing methods for aluminium alloy tank liners

With the growing concern about climate issues and the urgent need to reduce carbon emissions, hydrogen has attracted increasing attention as a clean and renewable vehicle energy source. However, the storage of flammable hydrogen gas is a major challenge, and it restricts the commercialisation of fuel cell electric vehicles (FCEVs). This paper provides a comprehensive review of common on-board hydrogen storage tanks, possible failure mechanisms and typical manufacturing methods as well as their future development trends. There are generally five types of hydrogen tanks according to different materials used, with only Type III (metallic liner wrapped with composite) and Type IV (polymeric liner wrapped with composite) tanks being used for vehicles. The metallic liner of Type III tank is generally made from aluminium alloys and the associated common manufacturing methods such as roll forming, deep drawing and ironing, and backward extrusion are reviewed and compared. In particular, backward extrusion is a method that can produce near net-shape cylindrical liners without the requirement of welding, and its tool designs and the microstructural evolution of aluminium alloys during the process are analysed. With the improvement and innovation on extrusion tool designs, the extrusion force, which is one of the most demanding issues in the process, can be reduced significantly. As a result, larger liners can be produced using currently available equipment at a lower cost.