A methodological contribution to failure prediction of glass ceramics sealings in high-temperature solid oxide fuel cell stacks

Solid oxide fuel cells (SOFCs) provide electrical energy through a highly efficient direct transformation of chemical energy stored in fuels. The sealing between the stacked components of the SOFC has to prevent gas leakage towards the environment as well as mixing of fuel gas and oxidant in order to ensure a reliable long-term operability. Hence, the understanding of the sealing loading conditions and the failure assessment plays a major role regarding the improvement of current and future SOFC designs. In the present study, glass ceramics sealing failure is investigated by means of a current SOFC design. For this purpose, the stresses in the sealings are firstly examined by employing a fully parameterized three-dimensional finite element model. On the basis of a canonical example, the underlying physical mechanisms, which are responsible for the occurrence of stresses, are identified and their influence is discussed. Since the initiation of sealing failure is complex and depends on several parameters, a methodology for failure assessment is proposed. In this context, the glass transition temperature is of superordinate importance. Since the material properties differ significantly depending on whether the operating temperature is below or above the glass transition temperature, several competing failure mechanisms must be considered.