Failure and stiffness analysis of ceramic from a 25-mm diameter diesel particulate filter

Three established mechanical test specimen geometries and test methods used to evaluate mechanical properties of brittle materials are adapted to the diesel particulate filter (DPF) architecture to evaluate failure initiation stress and apparent elastic modulus of the ceramics comprising DPFs. The three custom-designed test coupons are harvested out of 25-mm diameter DPFs to promote a particular combination of orientation of crack initiation and crack plane. The testing of the DPF biaxial flexure disk produces a radial tensile stress and a crack plane parallel with the DPF's longitudinal axis. The testing of the DPF sectored flexural specimen produces axial tension at the DPF's OD (outer diameter) and a crack plane perpendicular to the DPF's longitudinal axis. The testing of the DPF o-ring specimen produces hoop tension at the DPF's original OD and at the inner diameter of the test coupon, and a crack plane parallel to the DPF's longitudinal axis. The testing of these mechanical test coupons also enables the determination of a secant elastic modulus of the DPF ceramic material. Results consistently show that the secant elastic modulus of the DPF ceramics at tensile failure strain is approximately 1-2 GPa; this is approximately one order of magnitude less than the apparent elastic modulus estimated using sonic- or resonance-based test methods. However, the estimated tensile failure stresses are equivalent to those reported in other studies. The lower elastic modulus estimated in this work means that predicted tensile stresses in DPFs will be lower and that lifetime should be higher compared to when misleadingly high, sonic-based modulus values are used in those analyses.