Shear Strength of Cordierite Ceramic Catalyst Supports

An analytical model for estimating shear and bending stresses during canning of cordierite ceramic catalyst supports is presented. These stresses arise when the radial pressure distribution is nonuniform due, primarily, to variations in gap bulk density (GBD ) of intumescent mat around the perimeter of the substrate. Variations in GBD can occur during canning, regardless of the canning technique, due to anisotropic can stiffness or component tolerances or mat overlap. The model helps relate shear and bending stresses to substrate size and orientation, elastic modulii, cell size and wall porosity. If these stresses approach the corresponding strength of substrate, a shear crack may develop during or after the canning process depending on the magnitude of stress.

A special test fixture was developed to measure the shear strength of ceramic catalyst supports, with different cell sizes, before and after the application of washcoat. The shear and bending stresses at failure, as predicted by the model, were compared with the measured values. The agreement was found to be good lending credence to the model. The model should prove valuable in optimizing the packaging system such that the shear and bending stresses during canning are kept below the threshold limit of substrate.