Dynamic properties of heterogeneous materials with uncertain microstructures and local damage
|Bearbeitung:||Prof. Dr.-Ing. Udo Nackenhorst, M.Sc. Andre Hürkamp|
The goal of this research project is the development of novel predictive techniques for damage monitoring in heterogenous materials. Multi-scale modeling techniques are combined with related statistical methods for scale bridging. Exemplarily, investigations on the Ultra-High-Pressure-Concrete (UHPC) regarding microcracks and random distributed short fibres within a concrete matrix are made. The microstructure consists of the concrete matrix with its fine aggregate and inclusions of short fibers of e.g. steel. Also microcracks are taken into account. The microstructure is assumed to be random. Based on these heterogenous structures, progressive damage will be described, where not only a certain harmonic load defines the fatigue of material, but the history of the dynamic load and amplitudes. Using multiscale stochastic finite element approaches, the probability distribution of global mechanical properties for microheterogeneous materials and material fatigue will be evaluated. On the macroscale a homogenized structure with uncertain constitutive properties is available, where the dynamic behavior (eigenfrequencies, damping, changes in eigenmotions) as well as a fatigue of the material will be described.
In a first oder approach, analytical homogenization procedures for microcracks and short fiber reinforced composites based on the Eshelby solution are used. In doing so, the volume fraction of the fibres and the crack density are assumed to be randomly distributed. To cover the stochastic homogenization, advanced Monte-Carlo Simulations using Latin Hypercube Sampling are carried out.