Abstract
Engineering analyses of structures and devices call for efficient numerical methods that accurately
capture the behavior of the constituting materials. For highly heterogeneous materials,
homogenization methods substitute the heterogeneous microstructure by an effective continuum
that can be solved at the engineering level. Among the plethora of homogenization methods,
computational homogenization constitutes a powerful tool to establish a two-scale coupling of
complex nonlinear materials. Whereas the method has been used for a variety of problems, a new
challenge arises when metamaterials are considered. Metamaterials reveal microstructures that
induce a pronounced emergent effect at the macro-scale. This lecture focuses on the advanced
homogenization of dynamical and mechanical metamaterials.
Dynamical metamaterials are for instance used for inhibiting sound and vibration transmission in a
wide frequency range. First, a computational homogenization scheme applicable to resonant
acoustic metamaterials will be outlined [1]. Exploiting linearity, a closed form micromorphic
continuum homogenization approach for this class of materials is obtained. The corresponding
dispersion spectra are accurately captured, and the solution of initial boundary value problems is
thereby at reach. As a special case of dynamical metamaterials, metafoams will be presented [2].
Metafoams are a special class of foams combining thermo-viscous dissipation with local resonance.
Direct numerical simulations and the homogenization of these metafoams (extracting relations
between microstructure and effective properties) are demonstrated.
Spatial micro-scale fluctuation fields also emerge in mechanical metamaterials, driven by elastic
instabilities. Mechanical metamaterials do not trivially satisfy the classical scale separation principle
that underlies conventional homogenization strategies. Upon loading, these microstructures develop
fine scale fluctuation patterns that directly influence the coarse scale behaviour. Exploiting a
kinematical ansatz that incorporates the microstructural patterns, a micromorphic continuum is
recovered [3]. The two-scale predictive capabilities of the emerging micromorphic continuum are
illustrated, along with several demonstrative examples.
For both classes of metamaterials, the key aspects of the developed different homogenization
methods and the resulting (emergent) continua will be highlighted.
About the Speaker
Marc Geers is full professor in Mechanics of Materials at the Eindhoven University of
Technology in the Netherlands since 2000. His research interests are in the field of
micromechanics, multi-scale mechanics, damage mechanics and mechanical
metamaterials. He published more than 250 journal papers, with a significant citation
impact (Google scholar h-index=73). In the past 10 years, he presented more than 15
plenary lectures at international conferences and over 50 keynote and invited lectures.
At present, he is Editor-in-Chief of the European Journal of Mechanics A/Solids and serves
on the Editorial Boards of more than 15 international journals. He serves the Dutch
scientific community and organizations in various responsible roles. He is a Fellow of the
European Mechanics Society and a Fellow of the International Association for
Computational Mechanics. He received an Advanced Grant of the European Research
Council in 2013. He is the President of the European Mechanics Society EUROMECH.
Host: Professor Taher Saif
