Browsing by Author "Méndez Diez, Joel"
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Item Open Access Thermoviscoplasticity of glassy polymers : experimental characterization, parameter identification and model validation(2010) Méndez Diez, Joel; Miehe, Christian (Prof. Dr.)This work is concerned with the experimental characterization of the mechanical response of glassy polymers under various deformation modes, strain rates and temperatures together with the application of a framework of thermo-elasto-visco-plasticity in the logarithmic strain space recently developed in our group. The presented experiments are mainly classified based on the type of deformation in homogeneous and inhomogeneous and based on the applied strain rate in isothermal and thermomechanical. Homogeneous tests are understood to be uniaxial compression and plane strain compression experiments where the temperature does not rise due to deformation. Inhomogeneous experiments performed under tension are carried out together with unconventional equipment that allows a deeper insight into the necking phenomenon in glassy polymers. Discussions on the preprocessing, acquisition and post-processing of the experimental data are included. In the computational part of this work the plastic flow is approximated by means of two different micromechanically motivated constitutive theories for glassy polymers. The identification of the necessary material parameters and the simulations obtained therefrom give the foundation for a critical review of the capabilities of the employed constitutive laws. Additionally, thermomechanical experiments are simulated by one of the presented constitutive models to evaluate the capacity of the model at higher strain rates.