Speaker: Dr. Alexander E. Ehret

Abstract

Fibre network microstructures are an important component in providing soft biological tissues with their specialised functions and mechanical properties, and contribute to achieving tailored mechanical characteristics in man-made materials. At macroscopic length scale, these architectures can induce unusual mechanical behaviours, as will be illustrated by the examples of extreme Poisson’s ratios and outstanding defect tolerance. Discrete computational models of random networks, which account for single fibres within a representative volume, were employed to identify and analyse the network-scale mechanisms responsible for these behaviours. At the same time, continuum mechanical constitutive equationswere successfully used for efficient simulation of the macroscale behaviour, even though in general these models cannot reflect the complex kinematics of fibres in a random network. This discrepancy between matching macro- and mismatching micromechanics becomes relevant when microscale events shall be inferred from macroscale continuum metrics of stress and strain, and as a salient example the transition between tissue-scale biomechanics and cell-scale mechanobiology will be considered. Motivated by this aspect, the currently prevalent scale-bridging constitutive assumptions on fibre kinematics in continuum models will be critically revisited, and an alternative concept will be outlined.

Biography

Alex Ehret is a group leader at Empa, the Swiss Federal Laboratories for Materials Science and Technology, and a lecturer at ETH Zurich. He obtained his doctoral degree from the Faculty for Mechanical Engineering of RWTH Aachen University in 2011. After a postdoctoral position at TU Braunschweig, he was a DAAD postdoctoral fellow at the University of Glasgow. In 2013 he was awarded a Marie Curie Fellowship to conduct research in the Experimental Continuum Mechanics group at ETH Zurich, where he is still a research team leader today. In 2015, he joined the Experimental Continuum Mechanics Laboratory at Empa, where he leads the group for Mechanics of Soft Materials Systems. His research interests include the mechanics of soft deformable materials, particularly biological tissues, elastomers and materials with network microstructure, and focus on constitutive modelling and simulation aspects.