Curvature and stresses for bi-layer functional ceramic materials

Abstract

The technical application of layered functional ceramic components is challenged by curvature effects and residual stresses originating mostly from the thermal mismatch or chemical strains of the joined materials. Based on the general solution for elastic deformation of monolithic and multilayered materials the determination of curvature and residual stress for linear elastic bi-material specimens with chemical strains, chemical reduction in stiffness, shape variations, gradients in elastic modulus or thermal expansion is outlined. The use of the relationships is exemplified for ceramic solid oxide fuel cell (SOFC) and ceramic membrane materials. For SOFCs curvature changes are considered resulting from the reduction of the anode and crystallization of a glass–ceramic sealant with semi-spherical shape. For gas separation membranes which currently under development for fossil power plants the effect of chemical strains is assessed. The limits of using analytical relationships are addressed for the warpage of thin, rectangular SOFCs.