A study by Hamidreza Vanaei, professor and researcher at ESILV, explores the use of stereolithography (SLA) to manufacture polymer liners for Type IV hydrogen storage tanks. The research combines material characterisation, non-destructive testing and structural validation, providing new insights into additive manufacturing for hydrogen storage applications.
Hydrogen is expected to play an increasingly important role in the transition towards low-carbon mobility. One of the technological challenges remains the safe and efficient storage of compressed hydrogen, particularly for fuel cell vehicles. Type IV pressure vessels, which combine a polymer liner with a carbon fibre composite shell, have become a reference solution because they offer a favourable balance between weight and performance.
Evaluating stereolithography as a manufacturing process
Conventional polymer liners for Type IV hydrogen storage tanks are generally manufactured using rotational moulding. Although well established, this process offers limited design flexibility and can be restrictive when developing prototypes or complex geometries.
Research conducted by Hamidreza Vanaei, professor and researcher at ESILV, investigates stereolithography (SLA) as an alternative manufacturing route. Using a polyacrylic-based photopolymer resin (Resin Black V4), the study evaluates whether additive manufacturing can produce liner components with the mechanical performance required for hydrogen storage applications.
The work provides a comprehensive experimental assessment covering mechanical behaviour, thermal stability, fatigue performance, viscoelastic properties and structural validation.
Build orientation strongly influences mechanical behaviour.
One of the main objectives of the study was to understand how the orientation of printed parts affects their performance. Specimens were manufactured at five different build orientations, ranging from 0° to 90°, and subjected to extensive mechanical testing.
The results demonstrate a clear anisotropic behaviour. Tensile strength decreases by approximately 13% between the 0° and 90° orientations, while the compressive modulus is reduced by as much as 72%. These findings confirm that printing orientation remains a key design parameter when manufacturing structural components through stereolithography.
To predict these orientation-dependent properties, the research applied the Tsai-Hill and Tsai-Wu failure criteria. Both models closely matched the experimental results, with deviations remaining below 6%.
Optimising post-processing for strength and durability
The research also compares several post-curing conditions combining ultraviolet curing with different temperatures.
Among the tested configurations, UV curing followed by heating at 60 °C provides the most balanced performance. Samples reached a tensile strength of 74.5 MPa while maintaining 7.7% ductility and demonstrating fatigue endurance of up to 10⁵ loading cycles at 15 MPa.
By comparison, post-curing at 80 °C further increases the static tensile strength to nearly 80 MPa but also makes the material significantly more brittle, reducing its fatigue life.
Dynamic mechanical analysis also reveals that post-curing increases the glass transition temperature by up to 35 °C, improving the thermal performance of the printed material.
Combining non-destructive testing with structural validation
Beyond laboratory characterisation, the research integrates ultrasonic inspection as a non-destructive quality control method for SLA-manufactured components.
Ultrasonic measurements show approximately 30% improvement in elastic constants together with a 30% reduction in signal attenuation after optimised post-processing. These results demonstrate the potential of ultrasonic testing for assessing material quality without damaging printed parts.
To evaluate the structural behaviour of complete liners, finite element simulations were compared with experimental burst tests performed on scaled prototype tanks featuring wall thicknesses of 1, 3 and 6 mm.
The numerical predictions accurately identified both failure and survival conditions across all tested configurations, confirming the reliability of the modelling approach.
Supporting future hydrogen storage technologies
The study concludes that stereolithography represents a technically viable manufacturing process for Type IV hydrogen storage liners when appropriate printing parameters and post-processing conditions are applied.
By combining multi-scale material characterisation, fatigue analysis, non-destructive evaluation and structural validation, the research provides a comprehensive framework for assessing additively manufactured hydrogen storage components.
As hydrogen technologies continue to evolve for transport and energy applications, additive manufacturing offers new possibilities for producing lighter, more adaptable and highly customised components while supporting rapid prototyping and future industrial development.
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