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.
Mechanical behaviour of ± 55 ° filament-wound glass-fibre/epoxy-resin tubes: I. Microstructural analyses, mechanical behaviour and damage mechanisms of composite tubes under pure tensile loading, pure internal pressure, and combined loading
Abstract This series of papers on ± 55 ° filament-wound glass-fibre/epoxy-resin tubes consists of three parts. In Part I, the microstructure of the composite tube was first investigated by image processing to qualify the microstructural defects produced during manufacturing. A series of mechanical tests was then carried out under various combinations of hoop and axial stresses to evaluate the tubes' mechanical behaviour under pure axial tensile load, pure internal pressure, and under combined loading. Observations on specimens loaded to 20–50% of the ultimate tensile strength showed that the main damage initiation mechanisms are microcracking (matrix and transverse cracks) and delamination. Depending on the loading conditions, one of the mechanisms dominates over the other. The effect of microstructural defects on the damage initiation was clearly demonstrated. In Part II, micromechanical modelling of the damage initiation will be conducted in order to determine (1) the mechanical conditions under which different microcracking mechanisms occur and (2) the critical σzzσ/θθ ratio which corresponds to the change from one mechanism to another. Emphasis is placed on assessing the influence of microstructural defects and the competition between the different mechanisms. In Part III, a macroscopical behaviour law for the tubing structure with and without damage will be presented, and the simulation results will be compared with experimental ones.