Type of Publication
Year of Publication
2007
Authors
S. Anders
Abstract

Composite cylinders with metal liner are used for the storage of compressed hydrogen in automotiveapplication. These hybrid pressure cylinders are designed for a nominal working pressure of up to70 MPa. They also have to withstand a temperature range between -40 C and +85 C according GRPEdraft [1] and for short periods up to a maximum temperature of 140 C during filling (fast filling) [2].In order to exploit the material properties efficiently with a high degree of lightweight optimizationand a high level of safety on the same time a better understanding of the structural behavior of hybriddesigns is necessary. Work on this topic has been carried out in the frame of a work package on safetyaspects and regulation (Subproject SAR) of the European IP StorHy (www.storhy.net). Thetemperature influence on the composite layers is distinctive due to there typical polymer materialbehavior. The stiffness of the composite layer is a function of temperature which influences globalstrains and stress levels (residual stresses) in operation. In order to do an accurate fatigue assessmentof composite hybrid cylinders a realistic modeling of a representative temperature load is needed. Forthis, climate data has been evaluated which were collected in Europe over a period of 30 years [3].Assuming that the temperature follows a Gaussian (normal) distribution within the assessed period of30 years, it is possible to generate a frequency distribution for different temperature classes for thecold extreme and the hot extreme. Combining these distributions leads to the overall temperaturerange distribution (frequency over temperature classes). The climatic temperature influence, the fillingtemperature and the pressure load have to be considered in combination with the operation profile ofthe storage cylinder to derive a complete load vector for an accurate assessment of the lifetime andsafety level.

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