Dr. Reza Shaebani
Department of Theoretical Physics and Center for Biophysics
Saarland University
Gastgeberin: Prof. Dr. Aránazu del Campo
Abstract:
Meta materials exhibit (physical) properties that are not usually found in ordinary materials. A class of meta materials that has attracted a lot of recent interest is structural meta materials, i.e. those with unusual elastic, mechanical, or rheological properties. Such materials (including rationally engineered or natural fiber composites) have potential technological and industrial applications as inexpensive lightweight stable structures. Another material category of interest is ’smart materials‘, i.e. those that are designed to exhibit significant changes in at least one of their properties in a controllable fashion in response to external stimuli or changes in their environment.
I will first introduce our powerful discrete-element-method simulation tool to study large-scale systems of composite materials. Our simulator handles rigid objects, frictional and inelastic interactions, and geometric constraints such as bond length and angle between neighboring particles, which makes the simulations of composite materials (e.g., chains, rings, and so forth) feasible. This has enabled us to study disordered entangled assemblies of long semiflexible elements, as a major sub-class of structural meta materials ubiquitously observed in nature and daily life. Nonwoven textiles, bird nests, and aegagropila networks are a few examples. Our numerical and experimental results reveal strain stiffening and nonlinear rheology in oscillatory sheared packings of bead chains. We demonstrate how the rheological response is governed by the interplay between evolving entanglements (topological constraints) and increasing contribution of energy dissipation.
Next, I will introduce ‚active smart solids‘ as a new class of smart materials composed of jammed active discrete units (i.e. those consuming energy to move or exert mechanical forces) with controllable stability or mechanical response upon externally changing their properties such as activity. Toward designing real active solids, a core problem has been the absence of physical and material properties— such as friction, deformability, and inelasticity— in the current models. To overcome this problem, we superimpose the activity of the constituent elements onto the properties of real materials. As a promising example, assembling of colloidal particles by magnetic fields to construct structures such as micro-worms and micro-carpets will be discussed.
Kontakt:
Sylvia de Graaf
[email protected]
Tel.: 0681 9300 501