This thesis addresses the discontinuous modeling of failure in composite materials. Composite materials are characterized by the interaction of two or more individual materials. In the present thesis such composites are analyzed which in large part consist of cohesive materials. Cohesive materials may be found in nature in form of soils or can be manufactured synthetically like concrete and ceramics. The material behavior of cohesive materials is characterized, among other things, by a failure induced anisotropic degradation of the elastic stiffness properties. At the structural level the anisotropic failure of cohesive materials often appears in the evolution of narrow zones in which deformations localize whereas the rest of the structure mostly unloads.
On the basis of an enhanced continuum-mechanical description the behavior in failure of the investigated composites is modeled by the cohesive zone theory. The localization zone is approximated by a singular crack plane which can carry loads due to microscopic mechanisms as long as both crack faces are not completely separated. Since the modeling of the localization zone with a discrete crack implies a discontinuous solution, this kind to model material failure can be named discontinuous. In the present thesis numerical failure analyses of the composites are accomplished on different levels of material observation. Textile-reinforced concrete is analyzed based on a mesoscopic approach, whereas a macroscopic approach is chosen to model steel-reinforced concrete. In the mesoscopic modeling concept of textile-reinforced concrete the interface between both material constituents, the textile fiber and the concrete, has to be considered explicitly. For this reason the discontinuous failure analysis of composite structures on the mesoscopic level demands not only the consideration of discrete cracks but also of material interfaces. A main focus of this thesis is the derivation of a finite element approach to discretize these two discontinuities with different physical meanings. In addition, techniques are discussed to describe the geometry of the discontinuities.
The nonlinear, softening material behavior of concrete and material interfaces is mo\-deled by appropriate traction-separation-laws in the context of the cohesive zone theory. In order to accomplish discontinuous failure analyses of steel-reinforced concrete on the macroscopic level, the material structure is homogenized so that it can be passed on the discrete modeling of the steel-reinforcement. The material behavior is described by special constitutive laws of stress-strain- and traction-separation-type.
The discretization method developed in this thesis for the simulation of composite structures is included in a hierarchical two-scale concept. The resultant two-scale model affords the realization of efficient failure analyses of macroscopic structures under consideration of mesoscopic effects. Since a domain decomposition is part of the two-scale model, side conditions have to be formulated which are discussed and proven in terms of the ability to exactly model discontinuous failure with multiscale character.
%0 Thesis
%1 hettich2007diskontinuierliche
%A Hettich, Thomas M.
%D 2007
%I Doktorarbeit, Bericht Nr. 50, Institut für Baustatik und Baudynamik, Universität Stuttgart
%K MAT XFEM from:maltevonscheven ibb phdthesis
%R 10.18419/opus-269
%T Diskontinuierliche Modellierung zur Versagensanalyse von Verbundmaterialien
%X This thesis addresses the discontinuous modeling of failure in composite materials. Composite materials are characterized by the interaction of two or more individual materials. In the present thesis such composites are analyzed which in large part consist of cohesive materials. Cohesive materials may be found in nature in form of soils or can be manufactured synthetically like concrete and ceramics. The material behavior of cohesive materials is characterized, among other things, by a failure induced anisotropic degradation of the elastic stiffness properties. At the structural level the anisotropic failure of cohesive materials often appears in the evolution of narrow zones in which deformations localize whereas the rest of the structure mostly unloads.
On the basis of an enhanced continuum-mechanical description the behavior in failure of the investigated composites is modeled by the cohesive zone theory. The localization zone is approximated by a singular crack plane which can carry loads due to microscopic mechanisms as long as both crack faces are not completely separated. Since the modeling of the localization zone with a discrete crack implies a discontinuous solution, this kind to model material failure can be named discontinuous. In the present thesis numerical failure analyses of the composites are accomplished on different levels of material observation. Textile-reinforced concrete is analyzed based on a mesoscopic approach, whereas a macroscopic approach is chosen to model steel-reinforced concrete. In the mesoscopic modeling concept of textile-reinforced concrete the interface between both material constituents, the textile fiber and the concrete, has to be considered explicitly. For this reason the discontinuous failure analysis of composite structures on the mesoscopic level demands not only the consideration of discrete cracks but also of material interfaces. A main focus of this thesis is the derivation of a finite element approach to discretize these two discontinuities with different physical meanings. In addition, techniques are discussed to describe the geometry of the discontinuities.
The nonlinear, softening material behavior of concrete and material interfaces is mo\-deled by appropriate traction-separation-laws in the context of the cohesive zone theory. In order to accomplish discontinuous failure analyses of steel-reinforced concrete on the macroscopic level, the material structure is homogenized so that it can be passed on the discrete modeling of the steel-reinforcement. The material behavior is described by special constitutive laws of stress-strain- and traction-separation-type.
The discretization method developed in this thesis for the simulation of composite structures is included in a hierarchical two-scale concept. The resultant two-scale model affords the realization of efficient failure analyses of macroscopic structures under consideration of mesoscopic effects. Since a domain decomposition is part of the two-scale model, side conditions have to be formulated which are discussed and proven in terms of the ability to exactly model discontinuous failure with multiscale character.
@phdthesis{hettich2007diskontinuierliche,
abstract = {This thesis addresses the discontinuous modeling of failure in composite materials. Composite materials are characterized by the interaction of two or more individual materials. In the present thesis such composites are analyzed which in large part consist of cohesive materials. Cohesive materials may be found in nature in form of soils or can be manufactured synthetically like concrete and ceramics. The material behavior of cohesive materials is characterized, among other things, by a failure induced anisotropic degradation of the elastic stiffness properties. At the structural level the anisotropic failure of cohesive materials often appears in the evolution of narrow zones in which deformations localize whereas the rest of the structure mostly unloads.
On the basis of an enhanced continuum-mechanical description the behavior in failure of the investigated composites is modeled by the cohesive zone theory. The localization zone is approximated by a singular crack plane which can carry loads due to microscopic mechanisms as long as both crack faces are not completely separated. Since the modeling of the localization zone with a discrete crack implies a discontinuous solution, this kind to model material failure can be named discontinuous. In the present thesis numerical failure analyses of the composites are accomplished on different levels of material observation. Textile-reinforced concrete is analyzed based on a mesoscopic approach, whereas a macroscopic approach is chosen to model steel-reinforced concrete. In the mesoscopic modeling concept of textile-reinforced concrete the interface between both material constituents, the textile fiber and the concrete, has to be considered explicitly. For this reason the discontinuous failure analysis of composite structures on the mesoscopic level demands not only the consideration of discrete cracks but also of material interfaces. A main focus of this thesis is the derivation of a finite element approach to discretize these two discontinuities with different physical meanings. In addition, techniques are discussed to describe the geometry of the discontinuities.
The nonlinear, softening material behavior of concrete and material interfaces is mo\-deled by appropriate traction-separation-laws in the context of the cohesive zone theory. In order to accomplish discontinuous failure analyses of steel-reinforced concrete on the macroscopic level, the material structure is homogenized so that it can be passed on the discrete modeling of the steel-reinforcement. The material behavior is described by special constitutive laws of stress-strain- and traction-separation-type.
The discretization method developed in this thesis for the simulation of composite structures is included in a hierarchical two-scale concept. The resultant two-scale model affords the realization of efficient failure analyses of macroscopic structures under consideration of mesoscopic effects. Since a domain decomposition is part of the two-scale model, side conditions have to be formulated which are discussed and proven in terms of the ability to exactly model discontinuous failure with multiscale character.},
added-at = {2021-03-09T13:40:58.000+0100},
author = {Hettich, Thomas M.},
biburl = {https://puma.ub.uni-stuttgart.de/bibtex/285ef4a6c9d7ee7ecb7d6a387485de7aa/ibb-publication},
doi = {10.18419/opus-269},
interhash = {b201d638512b60389493073ab4be2dbe},
intrahash = {85ef4a6c9d7ee7ecb7d6a387485de7aa},
keywords = {MAT XFEM from:maltevonscheven ibb phdthesis},
publisher = {Doktorarbeit, Bericht Nr. 50, Institut für Baustatik und Baudynamik, Universität Stuttgart},
timestamp = {2021-03-24T14:38:46.000+0100},
title = {Diskontinuierliche Modellierung zur Versagensanalyse von Verbundmaterialien},
year = 2007
}
