Slow burst testing of samples as a method for quantification of composite cylinder degradation

An essential aspect of this approach is the validation of current residual strength and its prediction at any point of service life. In cases of gas cylinders with very high cycle strength, residual strength cannot be quantified statistically by means of hydraulic load cycles. As a replacement, creep tests or burst tests may be employed. BAM suggests the “slow burst test SBT” as a combination of these two test procedures. This is a compromise between the practicability of the (conventional) burst test and the practical relevance of sustained loads during service, to be tested in creep rupture tests. In this paper, a variety of 99 burst results of a cylinder design type used for breathing apparatus (CFRP with PE-liner) is evaluated. The influence of test procedure parameters and nature and intensity of artificial ageing on the test sample strength are analysed statistically. This leads to an evaluation of different procedures of artificial ageing and the recommendation to substitute conventional burst tests by slow burst tests for the assessment of composite pressure receptacles.