Global Failure Criteria for SOFC Positive/Electrolyte/Negative (PEN) Structure

Due to the mismatch of thermal expansion coefficients (TEC) of the various layer materials in SOFC, the internal stresses are unavoidable under temperature differential. In order to create the reliable cell and stack of solid oxide fuel cell (SOFC), it is necessary to develop a failure criterion for SOFC PEN structures for the initial failures occurred during cell/stack assembly. In this paper, a global failure criterion is developed for the initial design against mechanical failure of the PEN structure in high temperature SOFCs. The relationship of the critical energy release rate and critical curvature and maximum displacement of the warpage of the cells caused by the temperature differential is established so that the failure reliability of SOFC PEN structures may be determined by the measurement of the curvature and displacement of the warpaged cells.