The effect of porosity and microcracking on the thermomechanical properties of cordierite

Abstract

The effect of porosity and microcracking on the mechanical properties (strength, fracture toughness, Young's modulus, and fracture energy) and thermal expansion of diesel particulate filter (DPF) grade cordierite materials has been investigated. A method to deconvolute the effect of porosity and microcracking on Young's modulus is proposed. In addition, the microcrack density and the pore morphology factor are calculated by applying a micromechanical differential scheme. The values of the investigated mechanical properties are shown to decrease with an increase in porosity, but the thermal expansion values are insensitive to porosity. The variation in mechanical properties as a function of porosity leads to distinct porosity dependence of thermal shock resistance for crack initiation and crack propagation for DPF grade synthetic cordierite.

Adaptation of the chevron‐notch beam fracture toughness method to specimens harvested from diesel particulate filters

“…The measured K Ic‐app values in Table were about one‐third larger than those measured by Shyam et al. ; these can be compared because porous cordierite was characterized in all studies. The tortuosity of the produced fracture with the herein study's specimens is evident in Figure .…”

“…The tortuosity of the produced fracture with the herein study's specimens is evident in Figure . Such tortuosity is not a response that can be captured using the miniature cell‐wall specimens of Shyam et al . and it could be a contributor to why the measured K Ic‐app values in this study were higher.…”

“…The authors cannot dismiss the possibility (likelihood) that the K Ic‐app values in Table are only relevant to the herein explored “test system”. However, it is asserted that the “ K Ic ” values measured with the double torsion and SENB methods and reported by others are not strictly K Ic values but K Ic‐app values in their own right. In the strict sense, the K Ic of a dense cordierite ceramic (such as that reported in Ref …”

“…The K Ic of DPF‐porous‐ceramics have been reported. Shyam et al . performed double‐torsion testing of delicately harvested and elegant DPF‐cell‐wall specimens and estimated K Ic ~0.4‐0.5 MPa√m for porous cordierites.…”

Optimal design on the high-temperature mechanical properties of porous alumina ceramics based on fractal dimension analysis

“…As for the porosity, Shyam et al [8] found high porosity shows great benefits on enhancement of thermal shock resistance of porous ceramics since both crack propagation and thermal stress in ceramics are generally absorbed by porosity. It was reported by Jin et al [9] that the increase of porosity and decrease of pore size also result in superior thermal shock resistance.…”