Contact

Franzen, Daniel M.Sc.
Head of Investment Casting
Chair for comprehensive Foundry Science and Foundry Institute

Tel.: +49 (0) 241 80 - 98250
d.franzen@gi.rwth-aachen.de

Bionics

Following natural design principles, "structurally optimized sponges" are also being pursued as a research area at the Foundry Institute, in addition to the microstructured surfaces dealt with in the Cluster of Excellence.

In the interdisciplinary research project "Design and fabrication of graded cellular endoprostheses and lightweight structures", load-optimized sponge-like structures are fabricated that are optimized for density distribution, macro- and microstructure, and design.

Mg-Ca-Zn as biodegradable implant material

The degradation of magnesium in aqueous electrolytes is used to generate implants that dissolve in vivo in a defined period of time with as little residue as possible. Unlike permanent implants, this eliminates the need for follow-up surgery to remove the implant. Magnesium also has similar physical and mechanical properties to those of human bone, is an essential element of human metabolism, and is a correspondingly promising candidate for excellent biocompatibility and integrity. Specific degradation rates can thus be set by targeted alloy design using only non-toxic elements and by appropriate choice of the manufacturing process and thus the generated microstructure.

Bionics - metallic sponges

Cellular open-pored metallic structures represent a composite material with unique properties. The low weight, good thermal conductivity, flow-through and infiltration capability, high porosity of up to 98% and good energy absorption capacity make these structures extremely interesting for lightweight structures. The energy damping properties in particular promise interesting applications as safety elements, for example in the automotive or transportation sectors.  The design of the structures produced in the investment casting process is based on natural models within the framework of SSP1420. In drop tests, the cellular structures of the pomelo fruit skin exhibit superior energy dissipation upon impact of the fruit. As investigations show, it is obvious that this property is realized by a special hierarchical arrangement of the present building substance. For example, the peel of the pomelo fruit has at least seven hierarchical levels. A transfer of individual hierarchical levels or hierarchical combinations to technical open-pored metal foams promises a composite material with excellent energy damping combined with low material input and the associated lightweight construction properties.

Casting micro-structured surfaces

Another interesting area of bionics in terms of casting technology is the transfer of bionic surface structures such as the self-cleaning lotus leaf or shark skin to technical components such as an air volume limiter for racing developed at the Foundry Institute.

Furthermore, a DFG-funded project is currently looking into the casting microstructuring of bioactive glasses. The aim of the interdisciplinary work is the direct preservation of the surface structures without energy-introducing post-processing, which would provoke an undesired recrystallization of the glass.