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A 3-D finite element analysis (FEA) model of a 3-cell stack based on a prototype planar SOFC stack design was constructed to perform thermal stress analyses at shutdown and steady operation conditions. The constructed 3-D FEA model consists of complete planar SOFC components such as positive electrode-electrolytenegative electrode (PEN) assembly, interconnect, nickel mesh, and gas-tight glass-ceramic seal. The thermal stress distributions at shutdown and steady-state stages as well as their dependence on the initial stress-free temperature and operation cycles were systematically evaluated. Modeling results indicated that the glass-ceramic sealant was the most critical part needed to be watched in terms of structural integrity, in particular at operation temperature where shear fracture of such a component was predicted. Localized plastic deformation was predicted for the metallic interconnect and frame at both shutdown and steady-state conditions. An increase in the initial stress-free temperature would significantly increase the thermal stresses in all of the components at both shutdown and steady-state stages. In addition, a notable increase of thermal stress with increasing cycle number in the PEN at steady-state stage as well as in the glass-ceramic sealant at shutdown stage was predicted.

Finite element analysis (FEA) was conducted in this study to characterize the effects of clamping load on the thermal stress distribution in a planar solid oxide fuel cell (pSOFC) stack with compliant mica-based seal gaskets. Five different compressive loads (0.06, 0.1, 0.6, 1, and 6 MPa) were applied in the modeling to clamp the given pSOFC stack. Simulation results indicate that increasing the applied clamping load from 0.06 to 0.6 MPa could eliminate bending deformation in the positive electrode-electrolyte-negative electrode (PEN) assembly plate and its supporting frame. For a further increase of the applied clamping load to 1 and 6 MPa, the critical stresses in the glass-ceramic and mica sealants increased to a potential failure level. Thus, a 0.6-MPa clamping load is considered an optimal assembly load that can both eliminate bending deformation in the PEN-frame assembly plate and maintain acceptable critical stresses in the glass-ceramic and mica sealants.