Micro- and meso-scale modeling of dental composite materials
Produktform: Buch
In spite of the vast application of dental composite materials in dentistry rather than traditional
tooth fillings, durability of these composites is still of great concern. This dissertation
provides a micromechanical modeling of dental composites to investigate the failure mechanisms
and proposes some ideas to improve and optimize the mechanical properties of such
materials.
Lumpy appearance of the fracture surfaces of dental composite fillings indicates the microscopic
matrix cracking along the material interfaces. Zero-thickness cohesive interface
elements governed by the traction-separation law are utilized in this work to model the interface
debonding as well as the breakdown of the matrix zone. The constitutive equations of
the cohesive zone model contains suitable criteria for the initiation and evolution of damage
under mixed mode loading conditions. A viscous regularization approach is employed to
suppress the convergence difficulties of the implicit finite element analysis, while the time
dependent explicit solution scheme is utilized for three dimensional problems.
Direct numerical homogenization together with the necessarily statistical computations are
applied to investigate the influences of morphology and distribution of fillers on the effective
elastic properties of the composites. The numerical results are in a good agreement
with the experimental data available at the medical school of Hannover and institute of inorganic
chemistry. A parametric study on the effects of various properties of the filler and
interface zones on the stress-strain responses of the damaged microstructure is carried out as
well. Furthermore, a nested two-scale FE2 method is presented in this work to predict the
macroscopic behavior of dental composites during interface degradation.
In order to model the microcrack propagation within the matrix phase along the interfaces
of different filler shapes, a suitable strategy for automatically generation of interface
elements is developed. The main challenge is how to deal with the alteration of elemental
connectivities. The simulation results of nucleation and progression of cracks are validated
by the benchmark tests. It is hypothesized that the application of high aspect ratio fibers
at the microstructure of dental composites can improve the fracture resistance of them.
Hence, complex fracture mechanisms of crack deflection and crack bridging induced by the
incorporation of such fillers are simulated and also analyzed. The crack growth results are
illustrated in both two and three dimensional spaces.weiterlesen