TY  - JOUR
A1  - Buljak, Vladimir
A1  - Bruno, Giovanni
T1  - Numerical modeling of thermally induced microcracking in porous ceramics
BT  - an approach using cohesive elements
JF  - Journal of the European Ceramic Society
N2  - A numerical framework is developed to study the hysteresis of elastic properties of porous ceramics as a function of temperature. The developed numerical model is capable of employing experimentally measured crystallographic orientation distribution and coefficient of thermal expansion values. For realistic modeling of the microstructure, Voronoi polygons are used to generate polycrystalline grains. Some grains are considered as voids, to simulate the material porosity. To model intercrystalline cracking, cohesive elements are inserted along grain boundaries. Crack healing (recovery of the initial properties) upon closure is taken into account with special cohesive elements implemented in the commercial code ABAQUS. The numerical model can be used to estimate fracture properties governing the cohesive behavior through inverse analysis procedure. The model is applied to a porous cordierite ceramic. The obtained fracture properties are further used to successfully simulate general non-linear macroscopic stress-strain curves of cordierite, thereby validating the model.
KW  - analysis
KW  - Cohesive finite elements
KW  - Interfacial strength
Y1  - 2018
U6  - https://doi.org/10.1016/j.jeurceramsoc.2018.03.041
SN  - 0955-2219
SN  - 1873-619X
VL  - 38
IS  - 11
SP  - 4099
EP  - 4108
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Buljak, Vladimir
A1  - Oesch, Tyler
A1  - Bruno, Giovanni
T1  - Simulating Fiber-Reinforced Concrete Mechanical Performance Using CT-Based Fiber Orientation Data
JF  - Materials
N2  - The main hindrance to realistic models of fiber-reinforced concrete (FRC) is the local materials property variation, which does not yet reliably allow simulations at the structural level. The idea presented in this paper makes use of an existing constitutive model, but resolves the problem of localized material variation through X-ray computed tomography (CT)-based pre-processing. First, a three-point bending test of a notched beam is considered, where pre-test fiber orientations are measured using CT. A numerical model is then built with the zone subjected to progressive damage, modeled using an orthotropic damage model. To each of the finite elements within this zone, a local coordinate system is assigned, with its longitudinal direction defined by local fiber orientations. Second, the parameters of the constitutive damage model are determined through inverse analysis using load-displacement data obtained from the test. These parameters are considered to clearly explain the material behavior for any arbitrary external action and fiber orientation, for the same geometrical properties and volumetric ratio of fibers. Third, the effectiveness of the resulting model is demonstrated using a second, control experiment. The results of the control experiment analyzed in this research compare well with the model results. The ultimate strength was predicted with an error of about 6%, while the work-of-load was predicted within 4%. It demonstrates the potential of this method for accurately predicting the mechanical performance of FRC components.
KW  - Fiber-reinforced concrete
KW  - X-ray computed tomography (CT)
KW  - anisotropic fiber orientation
KW  - inverse analysis
Y1  - 2019
U6  - https://doi.org/10.3390/ma12050717
SN  - 1996-1944
VL  - 12
IS  - 5
PB  - MDPI
CY  - Basel
ER  -