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On the characterization of mechanical properties of porous and heterogeneous bio- and bioinspired materials
Klaus G Nickel
Last modified: 2009-06-25
Abstract
Klaus G. Nickel1, Willi Pabst2, Christoph Berthold1, Stefanie Schultheiss1, Christian Kohler1 & Volker Presser1
1University of Tuebingen, Faculty of Geosciences, Applied Mineralogy, Wilhelmstr. 56, 72074 Tuebingen, Germany, Klaus.nickel@uni-tuebingen.de
2Institute of Chemical Technology, Prague (ICT Prague), Department of Glass and Ceramics, Technick'a 5, 16628 Prague, Czech Republic
The mechanical characterization of partially or completely mineralized biological or bioinspired materials, for example, in terms of strength or physical parameters like elastic moduli, is often an important piece in the evaluation of the applicability of a construction inspired by natural principles. However, the interpretation of data obtained from conventional engineering practice can be misleading, because machine, measuring devices and material properties need to be understood to obtain significant and relevant numbers.
We will firstly discuss the pitfalls of such investigations, concentrating on the example of Young's modulus (E-modulus) from technical, biological and bioinspired materials. Examples of well defined dense inorganic materials and porous materials will be used to illustrate measurement problems, methods and theoretical aspects.
Biological materials from plants and marine animals often contain or consist of of mineral phases, which provide further complications. Both silica and calcium carbonates are auxetic, that is, their crystals can expand perpendicular to a tensile loading, when properly oriented. And orientated growth of such crystals is common in nature.
Further complications arise from the extreme heterogeneity of biomaterials, which often combine pores and soft organic matter with stiff mineral materials ("hetero-modulus-composites"). Thus, anisotropy, periodicities, gradients and structural hierarchy all contribute to the mechanical properties and it requires appropriate characterization techniques and suitable data interpretation to elucidate the natural material at hand and the artificial bioinspired material developed from it. This will be shown using examples from sea urchin spines and biomimetic ceramics made inspired by those. Conclusions for the measuring of plants and plant-inspired materials will be presented.
1University of Tuebingen, Faculty of Geosciences, Applied Mineralogy, Wilhelmstr. 56, 72074 Tuebingen, Germany, Klaus.nickel@uni-tuebingen.de
2Institute of Chemical Technology, Prague (ICT Prague), Department of Glass and Ceramics, Technick'a 5, 16628 Prague, Czech Republic
The mechanical characterization of partially or completely mineralized biological or bioinspired materials, for example, in terms of strength or physical parameters like elastic moduli, is often an important piece in the evaluation of the applicability of a construction inspired by natural principles. However, the interpretation of data obtained from conventional engineering practice can be misleading, because machine, measuring devices and material properties need to be understood to obtain significant and relevant numbers.
We will firstly discuss the pitfalls of such investigations, concentrating on the example of Young's modulus (E-modulus) from technical, biological and bioinspired materials. Examples of well defined dense inorganic materials and porous materials will be used to illustrate measurement problems, methods and theoretical aspects.
Biological materials from plants and marine animals often contain or consist of of mineral phases, which provide further complications. Both silica and calcium carbonates are auxetic, that is, their crystals can expand perpendicular to a tensile loading, when properly oriented. And orientated growth of such crystals is common in nature.
Further complications arise from the extreme heterogeneity of biomaterials, which often combine pores and soft organic matter with stiff mineral materials ("hetero-modulus-composites"). Thus, anisotropy, periodicities, gradients and structural hierarchy all contribute to the mechanical properties and it requires appropriate characterization techniques and suitable data interpretation to elucidate the natural material at hand and the artificial bioinspired material developed from it. This will be shown using examples from sea urchin spines and biomimetic ceramics made inspired by those. Conclusions for the measuring of plants and plant-inspired materials will be presented.