ANALYZIS OF THE FATIGUE LIFE OF HYDROGEN HIGH PRESSURE TANKS
Nevertheless, in order to respond to the economic a nd environmental criteria, hydrogen production and storage have to be improved. This wo rk focuses on gaseous storage under high pressure (700 bar) using a type III vessel (figure 1) that is to say composed of a metal liner – which prevents gas diffusion – and of a composite l aminate wrapped by filament winding – which is used as a mechanical strengthening piece. Th problem with this type of high pressure vessel is the early explosion when it is t ested to cyclic pressures. To solve this problem, the components – liner and composite – hav e to be well-proportioned.
Optimal design of a Type 3 hydrogen vessel: Part I—Analytic modelling of the cylindrical section
The present paper aims to study the cylindrical section of a Type 3 high-pressure hydrogen storage vessel, combining an aluminium liner which prevents gas diffusion and an overwrapped composite devoted to reinforce the structure. Today, this technique is widely used but still requires consistent time investments whenever a competitive solution, involving to definitely increase weight efficiency, is needed. The laminate composite is assumed to be an elasto-damage material whereas the liner behaves as an elasto-plastic material. Based on the classical laminate theory and on Hill's criterion to take into account the anisotropic plastic flow of the liner, the model provides an exact solution for stresses and strains on the cylindrical section of the vessel under thermomechanical static loading. Part I focuses on the theoretical background. The effect of the stacking sequence on the gap occurrence, on the residual stress magnitude and on the structure stiffness may then be investigated. This will be done and be compared with results of experiments which are carried out on prototypes in the second part of this paper before an optimization is performed.
The influence of winding patterns on the damage behaviour of filament-wound pipes
Abstract Filament winding is one of the most common techniques for the manufacture of tubes. The helical winding method often produces interweaving of fibres inside the layers. The aim of this study is to characterise the influence of the degree of this interweaving on the mechanical performance of cylindrical structures under various loadings. We present, first, the basics of the helical winding method and of a filament-winding machine designed for the study. The specimens studied are glass/epoxy tubes with a [±55°]6 lay-up. All manufacturing parameters are kept constant except for the winding pattern. Quality of the fabrication is assessed by strict monitoring of the geometry and the microstructure of the tubes. Tests carried out on the specimens consist in progressive repeated loadings, aimed at characterising the damage behaviour under various loadings. Damage growth is shown to be increased by the degree of interweaving of the tubes only for closed-ended internal-pressure loading. Weeping tests under this loading show that the presence of fibre crossovers may induce premature weeping of the pipes. The undulation regions and the voids found near these regions possibly represent an initiation site for cracking, thus increasing damage growth and the possibility of leaking in high interwoven structures.