TY - JOUR A1 - Bruno, Giovanni A1 - Shyam, A. A1 - Watkins, T. R. A1 - Pandey, A. A1 - Lara-Curzio, E. A1 - Parish, C. M. A1 - Stafford, R. J. T1 - The effect of porosity and microcracking on the thermomechanical properties of cordierite N2 - 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) gradecordierite materials has been investigated. A method to deconvolute the effect of porosity and microc-racking on Young’s modulus is proposed. In addition, the microcrack density and the pore morphologyfactor are calculated by applying a micromechanical differential scheme. The values of the investigatedmechanical properties are shown to decrease with an increase in porosity, but the thermal expansionvalues are insensitive to porosity. The variation in mechanical properties as a function of porosity leadsto distinct porosity dependence of thermal shock resistance for crack initiation and crack propagationfor DPF grade synthetic cordierite. KW - Diesel particulate filter KW - Cordierite KW - Porosity KW - Microcracking KW - Micromechanical differential scheme PY - 2015 DO - https://doi.org/10.1016/j.jeurceramsoc.2015.08.014 VL - 2015/35 IS - 16 SP - 4557 EP - 4566 PB - Elsevier Ltd. AN - OPUS4-37973 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bruno, Giovanni A1 - Onel, Yener A1 - Cooper, R. C. A1 - Lange, A. A1 - Watkins, T. R. A1 - Shyam, A. T1 - Young's modulus and Poisson's ratio changes due to machining in porous microcracked cordierite N2 - Microstructural changes in porous cordierite caused by machining were characterized using microtensile testing, X-ray computed tomography, and scanning electron microscopy. Young's moduli and Poisson's ratios were determined on similar to 215- to 380-mu m-thick machined samples by combining digital image correlation and microtensile loading. The results provide evidence for an increase in microcrack density and decrease of Young's modulus due to machining of the thin samples extracted from diesel particulate filter honeycombs. This result is in contrast to the known effect of machining on the strength distribution of bulk, monolithic ceramics. KW - Stress KW - Beta-Eucryptite KW - Brittle materials KW - Ceramic materials KW - Thermal-Expansion KW - Fracture-Toughness KW - Composite materials KW - Differential scheme KW - Elastic-moduli KW - Representative volume element PY - 2016 DO - https://doi.org/10.1007/s10853-016-0209-9 SN - 0022-2461 VL - 51 IS - 21 SP - 9749 EP - 9760 PB - Springer, NY, USA AN - OPUS4-37867 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cooper, R. A1 - Bruno, Giovanni A1 - Shyam, A. A1 - Watkins, T. A1 - Pandey, A. A1 - Wheeler, M. T1 - Effect of microcracking on the uniaxial tensile response of beta-eucryptite ceramics: Experiments and constitutive model N2 - A constitutive model for the nonlinear or “pseudoplastic” mechanical behavior in a linear-elastic solid with thermally induced microcracks is developed and applied to experimental results. The model is termed strain dependent microcrack density approximation (SDMDA) and is an extension of the modified differential scheme that describes the slope of the stress-strain curves of microcracked solids. SDMDA allows a continuous variation in the microcrack density with tensile loading. Experimental uniaxial tensile response of β-eucryptite glass and ceramics with controlled levels of microcracking is reported. It is demonstrated that SDMDA can well describe the extent of non-linearity in the experimental uniaxial tensile response of β-eucryptite with varying levels of microcracking. The advantages of the SDMDA are discussed in regard to tensile loading. KW - Microcracking KW - β-eucryptite KW - Young's modulus KW - Modeling KW - Tensile behavior PY - 2017 DO - https://doi.org/10.1016/j.actamat.2017.06.033 SN - 1359-6454 SN - 1873-2453 VL - 135 SP - 361 EP - 371 PB - Elsevier Ltd. AN - OPUS4-40859 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -