Woodruff School of Mechanical Engineering
Mechanical Engineering Seminar
Nano to macro: multi-scale modelling of spider silk
Prof. Bernd Markert
Institute of General Mechanics, RWTH Aachen University
Monday, November 13, 2017 at 3:00:00 PM
Love Building, Room 210
Molecular dynamics (MD) simulations allow us to study dynamic events on an atomic level. This technique is based on the numerical solution of Newton's equations of motion, and it can be effectively used for studying mechanical properties of macromolecules  as well as to describe mechanical phenomena occurring at larger scales such as damage and fracture [2, 3]. However, the time (femtosecond) and size limitations (atom level) are the biggest drawback of MD simulations. The versatility of Phase-field Models (PFM) has caught the attention of the scientific community regarding phase transition problems. Their inherent simplicity to model multi-physics and multi-field applications have spread their use into physics, chemistry, medicine, material science and engineering applications. Lately, much attention has been paid to model damage and fracture with PFM [4, 5] and a possible multi-scaling through the combination of both tools has been also proved to be possible [2, 3]. The combination of MD with continuum approaches, could lead up to a scale bridge, enabling the use of information obtained at atom level into larger scales. In order to illustrate this methodology, I introduce two exemplifying applications. On the one hand, the bottom-up modelling of brittle fracture by means of MD and PFM. On the other hand, I present to you a novel approach to model the behaviour of biological materials, namely spider silk, at the nano- and microscales, and the possibility to conceptualize bio-inspired material based on the bottom-up modelling into a structural level. A potential application of such materials in the fabrication of Air-Bags, is presented through a numerical example.
 S. P. Patil, B. Markert, F. Gräter, Rate-dependent behavior of the amorphous phase of spider dragline silk, Biophys J, vol. 106 (11) 2511–2518, (2014).
 S. P. Patil, Y. Heider, C. A. Hernandez-Padilla, E. Cruz-Chu, B. Markert, A combined molecular dynamics-phase-field modeling approach to fracture, Comput Methods Appl MechEng, vol. 312 117-129, (2016)
 C. A. Hernandez-Padilla, S. P. Patil, Y. Heider, B. Markert, 3D Modeliling of brittle fracture using a joint all-atom and phase-field approach, GAMM Mitteilungen, vol. 40, issue 2, 7-17, (2017)
 C. A. Hernandez Padilla & B.Markert, A coupled ductile fracture phase-field model for crystal plasticity, Continuum Mechanics and Thermodynamics, On-linefirst, DOI: 10.1007/s00161-015-0471-0, 2015
 B. Markert, Y. Heider, Coupled multi-field continuum methods for porous media fracture, Recent Trends in Computational Engineering – CE2014 Lecture Notes, Comput. Sci. Eng. vol. 105 167-180, (2015).
Bernd Markert is Director of the Institute of General Mechanics in the Department of Mechanical Engineering at RWTH Aachen University in Germany.