In the present thesis, a material model is developed to describe the crosslinking progress and the associated phenomena of photopolymers in additive manufacturing processes. The model equations therein are motivated by experimental investigations conducted on a commercial photopolymer and formulated by means of the methods of continuum mechanics. The material model can represent the viscoelastic and viscoplastic properties of the photopolymer depending on the degree of cure and temperature. First, established additive manufacturing processes for photopolymers are presented, and their benefits and limitations are discussed. Digital Light Processing™ is selected for the fabrication of the specimens due to its simple design and increased printing speed compared to other processes. The subsequent experiments investigate the transition of the photopolymer from the liquid to the solid state and the associated change in the material properties. For this purpose, existing experimental setups (DSC, rheometer) are modified with a light source enabling the irradiation necessary to start the crosslinking reaction in the photopolymer. The decisive parameters in Digital Light Processing™ can be variably adjusted with the modified measurement setup. Dynamic mechanical analyses are performed to characterize the temperature-dependent viscoelastic properties of printed specimens with different degrees of cure, whereas the viscoplastic properties are investigated using tensile tests with different temperatures, degrees of cure, and strain rates. The material model is numerically discretized for the implementation into the finite element program LS-DYNA® to perform three-dimensional simulations. The parameters of the material model are identified using innovative optimization algorithms, and provide, in combination with the model, a good agreement with the experimental data. The validation of the developed model equations and identified parameter sets is performed using simulated tensile tests subjected to cyclic loading and unloading in order to demonstrate the predictive quality of the material model.    «

In the present thesis, a material model is developed to describe the crosslinking progress and the associated phenomena of photopolymers in additive manufacturing processes. The model equations therein are motivated by experimental investigations conducted on a commercial photopolymer and formulated by means of the methods of continuum mechanics. The material model can represent the viscoelastic and viscoplastic properties of the photopolymer depending on the degree of cure and temperature. Firs...    »