Place: Kleiner Physik-Hörsaal, Geschwister-Scholl-Platz
Date: 19.11.10, Time: 15:30 h
Ab-initio Based Multiscale Modeling for Biological Composite Materials: Example of the Exoskeleton of the Lobster Homerus Americanus
Prof. Dierk Raabe
Dept. Microstructurephysics and Metal Forming, MPI für Eisenforschung, Düsseldorf
The lecture is about experiments and a hierarchical model for the elastic properties of mineralized lobster cuticle using i) ab initio calculations for the chitin properties and ii) hierarchical homogenization performed in a bottom-up order through all length scales. It has been found that the cuticle possesses nearly extremal, excellent mechanical properties in terms of stiffness that strongly depend on the overall mineral content and the specific microstructure of the mineral-protein matrix. In this lecture it is discussed how the overall cuticle properties change when there are significant variations in the properties of the constituents (chitin, amorphous calcium carbonate (ACC), proteins), and the volume fractions of key structural elements such as chitin-protein fibers. It is found that the cuticle performance is very robust with respect to variations in the elastic properties of chitin and fiber proteins at a lower hierarchy level. At higher structural levels, variations of design parameters such as the volume fraction of the chitin-protein fibers have significant influence on the cuticle performance. Furthermore, it is observed that among the possible variations in the cuticle ingredients and volume fractions, the experimental data reflect an optimal use of the structural variations regarding the best possible performance for a given composition due to the smart hierarchical organization of the cuticle design.