Out‐of‐plane Mechanical Characterization of Acicular Mullite and Aluminum Titanate Diesel Particulate Filters

This study characterizes the flexural and compressive behavior of two porous ceramic honeycombs commonly used in diesel particulate filtration, acicular mullite and aluminum titanate. Compression along the axis normal to the honeycomb cross-section, referred to as out-of-plane compression, is compared to in-plane flexure. The relationship between these loading modes is assessed using the failure strength and elastic modulus of the honeycomb structure and the constituent wall material. Weibull analyzes showed that flexure and out-of-plane compression exhibit similar behavior in cases where failure is governed by a single flaw, such as in acicular mullite. However, in heavily microcracked systems like aluminum titanate, compressive failure occurs by damage accumulation rather than growth of a single flaw, so compressive failure strengths are higher than flexural ones. Buckling was also shown to occur in both systems, but the geometries required are unlikely to be encountered in practical application. In the context of filter life assessment, failure in flexure occurs at much lower stresses for systems that rely on microcracking to accommodate thermal strains, so flexure is better suited as an estimate of filter strength.