Permeation and Leak Testing of Composites for Tank Systems under Tensile Stress
Dr. Andreas Konrad*, Bernd Pannwitt, Mecadi GmbH, D-66450 Bexbach Prof. Dr. Rolf Hempelmann, Francesco Arena, Universität des Saarlandes, FR 8.1, D-66123 Saarbrücken Dr. Waldhauser, JOANNEUM RESEARCH Forschungsgesellschaft mbH Laserzentrum, Leoben, A-8712 Niklasdorf Ludger Strack, Wolfgang Oelerich, GM Europe Engineering, IPC MK-01 D-65423 Rüsselsheim Matthias Block, Alcatel Hochvakuumtechnik GmbH, D-97877 Wertheim * Lecturer
Tank systems from plastic will allow storage of hydrogen under a pressure of 700 bar. In the temperature range from –40 °C up to +85 °C mechanical stability and low permeation rates must be ensured simultaneously. These requirements make the application of composite material with reinforcement and barrier layers necessary. However the qualification of composites regarding conformance of permeation limit value under mechanical and thermic stress is desirable before prototyping to make a preselection of potential material versions.
Mecadi has developed a test equipment, which makes it possible to measure permeation rates of composite films under thermic stress (-80 °C - +200 °C) and tensile strength (0-20 % uniaxial elongation). Therefore a Mecadi permeation measuring cell for polymer film samples (0.01-10 mm thickness) was upgraded by a pulling equipment. For verification of tightness and for detection of permeation rates a high sensitive hydrogen leak detector is utilised. Metal-polymer and polymer composites were investigated. Metal-polymer composites show a noticeable lost of barrier properties under tensile strength (order of magnitude), but some polymer composites change negligibly or within the order of magnitude the permeation characteristic under conditions which were expected for tank systems.
Concepts based on these measurements were developed to qualify materials for tank systems in pre-tests.