TY - JOUR A1 - Mair, Georg A1 - Scholz, Irene A1 - Schönfelder, Thorsten T1 - The residual strength of breathing air composite cylinders toward the end of their service life - a first assessment of a real-life sample JF - Journal of pressure vessel technology N2 - Applications by fire brigades expose the composite cylinders to harsh temperature and handling conditions. Standards have been used for certifying composite cylinders, which are designed for transport of dangerous goods and do not reflect service conditions specific to fire brigades. In this paper, the residual safety of a design type (fully wrapped with aluminum and carbon fiber composite) at the end of their service life of 15 yrs is analyzed. One sample underwent hydraulic load cycle (LC) tests, another conventional burst tests, and the third slow burst tests (SBTs). The statistical evaluation and the handling of an unexpected high amount of early failures are shown. KW - Composite cylinders KW - End of life KW - Slow burst test KW - Residual strength KW - Sample testing KW - Probabilistic KW - Distribution function PY - 2016 DO - https://doi.org/10.1115/1.4033878 SN - 0094-9930 SN - 1528-8978 VL - 138 IS - 6 SP - PVT-15-1030, 1 EP - 9 PB - American Society of Mechanical Engineers CY - New York, NY AN - OPUS4-33157 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mair, Georg A1 - Hoffmann, Martin A1 - Schönfelder, Thorsten ED - Carcassi, M.N. T1 - The slow burst testing of composite cylinders - Part I: Slow burst testing of samples as a method for quantification of cylinder degradation T2 - ICHS2013 - 5th International conference on hydrogen safety (Proceedings) N2 - The current practise of focusing the periodic retesting of composite cylinders primarily on the hydraulic pressure test has to be evaluated as critical - with regard to the damage of the specimen as well as in Terms of their significance. This is justified by micro damages caused to the specimen by the test itself and by a lack of informative values. Thus BAM Federal Institute of Materials Research and Testing (Germany) uses a new approach of validation of composite for the determination of re-test periods. It enables the description of the state of a population of composite cylinders based on destructive tests parallel to operation. An essential aspect of this approach is the prediction of residual safe service life. In cases where it cannot be estimated by means of hydraulic load cycle tests, as a replacement the creep or burst test remains. As a combination of these two test procedures BAM suggests the 'slow burst test SBT'. On this a variety of about 150 burst test results on three design types of cylinders with plastic liners are presented. For this purpose both, the parameters of the test protocol as well as the nature and intensity of the pre-damage artificially aged test samples are analysed statistically. This leads first to an evaluation of the different types of artificial ageing but also to the clear recommendation that conventional burst tests be substituted totally if indented for assessment of composite pressure receptacles. T2 - ICHS2013 - 5th International conference on hydrogen safety CY - Brussels, Belgium DA - 09.09.2013 KW - Residual strength KW - CFRP KW - Gas storage KW - Reliability KW - Sample testing PY - 2013 SN - 978-2-9601366-0-9 SP - 1 EP - 12 AN - OPUS4-29260 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -