Influence of pressure cycling on damage evolution in an unfilled EPDM exposed to high-pressure hydrogen

This study aims to reveal the internal damage evolution process in a transparent ethylene propylene diene rubber (EPDM) under high-pressure hydrogen cycles (9 and 15 MPa). Damage accumulation of EPDM was tracked from in-situ pictures during cycling. Several dedicated image processing routines allowed the discrimination of mechanisms (separated cavities, clusters and cracks) and sometimes the qualification of their morphology (size distribution, number, ratio of cavities reappearing at any cycle). Numerous small cavities were observed at any cycle, some of them being clustered under the highest pressure. Only part of them systematically appeared again. Some of these cavities inflated and “absorbed” small cavities around them when clustered. Finally, a few cracks were nucleated from some large cavities and grew, following a “stop and grow” process.