Untersuchungen zur Alterungsbeständigkeit von Dichtungen in PEM-Brennstoffzellen
Auch gedruckt in der BibliothekW: W-H 14.201
FakultätFakultät für Ingenieurwissenschaften und Informatik
Ressourcen- / MedientypDissertation, Text
Datum der Freischaltung2015-05-29
An in-depth insight in the ageing resistance of sealings and its impact on the cell-performance is necessary for the optimization of a fuel cell’s durability and reliability. But in the past relative little attention has been paid to this component. Furthermore the existing and commonly used methods for evaluating the sealing-properties are found not to be sufficient. Within the scope of this thesis recent ex-situ test methods are compared to evaluate material samples as well as full-size sealings in terms of ageing behavior. Due to its importance, a special attention is paid to the relaxation behavior. The specimen were made of two common sealing materials, an EPDM and a silicone, and aged in fuel cell-relevant media beforehand. FEM-simulation is used to investigate the influence of the specimen-geometry on the ageing-behavior and on the simulation-quality. A seal ageing test-bench is developed to fill the gap between material-tests and stacktests. Since this is an ex-situ test method, there is no need for expensive MEAs. Sealings are investigated under realistic ageing conditions, as stack-like compression, variable temperature- and humidity cycles and the application of an internal pressure. Furthermore the different seal areas are in contact with the same media like in a fuel cell stack. Results indicate that deviations in the production process can have a significant influence on material properties. Results furthermore point to different ageing behavior of material samples compared to fuel cell sealings. Recommendations are given to prefer particular test methods as against others and to adopt the compression set test method to the fuel cell conditions.