Das Team TU Vision 2025+ lud zu Vortrag und Diskussion mit Roberto Ballinari, Department of Civil and Environmental Engineering, University of Houston, zum Semesterthema Exzellenz
Wann? Montag, 2.5.2016 um 18:00 Uhr
Wo? Kontaktraum, Gußhausstraße 27-29, 6. Stock, 1040 Wien
Natural composite materials are renowned for their mechanical strength and toughness; despite being highly mineralized, with the organic component constituting not more than a few percent of the composite material, the fracture toughness exceeds that of single crystals of the pure mineral by two to three orders of magnitude. The judicious placement of the organic matrix, relative to the mineral phase, and the hierarchical structural architecture extending over several distinct length scales both play crucial roles in the mechanical response of natural composites to external loads. In addition, natural composites are capable of repairing significant levels of damage that they may have experienced during their lifetime.
In this talk experimental and theoretical results are first used to show that the resistance of the shell of the conch Strombus Gigas to catastrophic fracture can be understood quantitatively by invoking two energy-dissipating mechanisms: multiple cracking in the outer layers at low mechanical loads, and crack bridging in the shell's tougher middle layers at higher loads. Both mechanisms are intimately associated with the so-called crossed lamellar microarchitecture of the shell, which provides for tunnel cracking in the outer layers and uncracked structural features that bridge crack surfaces, thereby significantly increasing the work of fracture of the material. Despite a high mineral content of about 99% (by volume) of aragonite, the shell of Strombus Gigas can thus be considered 'ceramic plywood' (albeit plywood fails in a different manner than the shell), and can guide the bioinspired design of tough, lightweight structures.
The second part of the talk illustrates Strombus gigas' ability to repair load-induced damage through biomineralization, of attempts to mimic the microarchitectures of sea shells using nano and micro fabrication techniques, and the development of self-healing paradigms for synthetic structures and materials.
The talk will end with some suggestions of mechanisms that can be created and sustained within an academic environment that will encourage, nurture and enable multi- disciplinary pedagogy and research.