STRENGTH SIZE EFFECTS IN CELLULAR CERAMIC STRUCTURES

Strength size effects were studied in two cordierite cellular ceramic structures with two different cell densities, namely Corning Incorporated's Duratrap(R) CO 100/17 and CO 200/12 diesel particulate filter products. Strength tests in bending were conducted on bars with sizes that ranged from 2 x 4 cells to 15 x 30 cells for the 100/17 product and from 3 x 6 cells to 21 x 42 cells for the 200/12 product. Contrary to the Weibull strength size effect relationship, no significant strength size effect was observed for either of these two materials in this experiment. This size independent strength is thought to be linked to the structural features of these extruded cordierite materials such as porosity and microcracking. Calculation of the moment of inertia term, capturing the cellular structure, shows that the assumption of a homogeneous continuum in the strength calculations results in an overestimate of reported bend strength. This overestimate becomes large for coarse structures where the bar dimensions approach the scale of the cellular dimensions.