The Relationship Between Microstructure and Fracture Toughness for Fibrous Materials for Diesel Particulate Filters

Abstract

The Mode I fracture toughness of fibrous SiC and mullite materials with 60%–70% porosity was determined under ambient conditions using the double‐torsion test method. The fracture toughness values obtained were 0.27 and 0.34 MPa·m1/2 for fibrous SiC and mullite, respectively. These fibrous ceramics exhibit greater fracture resistance than porous monolithic ceramics with similar levels of porosity. A higher degree of cross‐linking between the fibers led to further improvement in the fracture characteristics of the fibrous material. The differences in fracture behavior can be explained by the microstructural differences between these two classes of materials. The combination of high porosity and high fracture toughness for fibrous materials makes them ideal candidates for applications in diesel particulate filtration.

Microstructure and mechanical properties of acicular mullite

“…At 62.7% porosity it has a fracture toughness of 0.34 MPa m 1/2 , as measured by the double torsion test. 34 ACM of comparable porosity has a fracture toughness of 0.54 MPa m 1/2 . It should be noted that the double torsion test produces fracture toughness values that are comparable to or slightly less than those determined by the single-edge notched beam test.…”

Effects of regenerative mechanical vibration on the mechanical integrity of ceramic diesel particulate filters

“…The micro-cracks www.springer.com/journal/40145 J Adv Ceram 2018, 7(1): 5-16 9 are suggested to develop in cordierite during high temperature processing [22]. The level of porosity and the presence of micro-cracks can have impact on the mechanical properties of a cordierite [23,24].…”

“…The level of porosity and the presence of these micro-cracks will influence the mechanical properties of cordierite. Gordon et al [23] reported the fracture toughness of monolithic cordierite to be about 0.242 MPa·m 1/2 , while the cordierite investigated by Shyam et al [24] was determined to have fracture toughness that varies between 0.38 and 0.45 MPa·m 1/2 , depending on notch orientation. Fracture toughness of cordierite has been reported to decrease with increase in porosity [23].…”

“…Gordon et al [23] reported the fracture toughness of monolithic cordierite to be about 0.242 MPa·m 1/2 , while the cordierite investigated by Shyam et al [24] was determined to have fracture toughness that varies between 0.38 and 0.45 MPa·m 1/2 , depending on notch orientation. Fracture toughness of cordierite has been reported to decrease with increase in porosity [23]. Depending on the sintering temperature, Suzuki et al [25] determined the fracture toughness of dense cordierite to range between 2 and 3 MPa·m 1/2 .…”

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

“…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. Gordon et al . estimated K Ic ~0.3 MPa√m for fibrous porous ceramics using the same test method.…”