Mechanical Property Characterizations and Performance Modeling of SOFC Seals

The objective of this work was to provide a modeling tool for the design of reliable seals for SOFC stacks. The work consisted of experimental testing to determine thermal-mechanical properties of a glass-ceramic sealing material and numerical modeling of stack sealing systems. The material tests captured relevant temperature-dependent property data for Pacific Northwest National Laboratory's (PNNL) G18 sealant material as required by the analytical models. A viscoelastic continuum damage model for this glass-ceramic sealant was developed and implemented in the MSC MARC finite element code and used for a detailed analysis of a planar SOFC stack under thermal cycling conditions. Realistic thermal loads for the stack were obtained using PNNL's multiphysics solver SOFC-MP. The accumulated seal damage and component stresses were evaluated for multiple thermal loading cycles. The seals nearest the stack mount location were most susceptible to damage which began during the first operational cycle and accumulated during shutdown. Viscoelastic seal compliance was also found to beneficially reduce the stresses in the anode.