Browsing by Author "Göktepe, Serdar"

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Open Access
Micro-macro approaches to rubbery and glassy polymers : predictive micromechanically-based models and simulations
(2007) Göktepe, Serdar; Miehe, Christian (Prof. Dr.-Ing. habil.)
This work is concerned with the development of physically motivated constitutive models for the description of the material behavior of rubbery and glassy polymers. The particular focus of the thesis is placed on elasticity, finite viscoelasticity, deformation-induced Mullins-type damage in rubbery polymers, and finite viscoplasticity of amorphous glassy polymers. The models developed possess the intrinsic character of a micro-macro transition that, in turn, allows us to incorporate the physical mechanisms stemming from a micro-structure of the material through geometrically well defined kinematic measures and in terms of physically motivated material parameters. The proposed approaches make use of a micro-structure that is symbolized by a unit sphere, the so-called micro-sphere. The surface of the micro-sphere represents a continuous distribution of chain orientations in space. A key idea of the proposed constitutive framework may be considered as a two-step procedure that incorporates the set up of micromechanically-based constitutive models for a single chain orientation and the definition of the macroscopic stress response through a directly evaluated homogenization of state variables. The disribution of micro-state variables are defined on the micro-sphere of space orientations in a discrete manner. The proposed models are further furnished with the associated algorithmic procedures that perform the update of internal variables and computation of stresses and tangent moduli in a way consistent with the employed integration scheme. The modeling performance of the models is tested against broad range of homogeneous and inhomogeneous experimental data with particular regard to their predictive simulation capabilities.