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- 2016 (16) (entfernen)
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- Degradation (6)
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Eingeladener Vortrag
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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.
This slides explain the functionality and the procedure of the UN-service life checks as they are operated by BAM as German authority. These are based on the probabilistic approach including evaluation of current safety level and its comparison with assessments of different status of degrdation including extrapolation towards end of safe service life.
The similarity to the approach for determiantion of retest periods by BAM is explained.
Gas cylinders made of composite materials receive growing popularity in light-weight applications. Current standards are mostly based on safety determination relying on minimum amounts of endured load cycles and a minimum burst pressure of a small number of specimens. This paper investigates the possibilities of a probabilistic strength assessment for safety improvements as well as cost and weight savings. The probabilistic assessment is based on destructive testing of small sized samples. The influence of sample size on uncertainty of the assessment is analysed. Furthermore, methods for the assessment of in-service ageing (degradation) are discussed and displayed in performance charts.
The set of slides summarises the expectations of participants discussed during the opening session. Then the most important aspects of the presentations during the first two days are compiled. At the end the conclusions coming out of a joint discussion are presented. This show what participants expect BAM to do for implementation of the PA in near future.
Current standards governing the design, qualification and in-service inspection of carbon fibre composite cylinders do not facilitate to optimise cylinder design. The requirements have been adapted from standards for metallic cylinders and cannot easily quantify the degradation processes in composite materials. In this article, the results of hydraulic and hydrogen pressure cycle life tests performed on composite reinforced tanks with a metal liner (type 3) and with a high density polymer liner (type 4) are shown. Moreover, the degradation measured by means of residual strength of the tanks after the cycling tests have been compared. It has been found that the most critical aging for metal based composite cylinder is the gaseous cycling while type 4 designs seem to be more sensitive to hydraulic cycling at high temperature.