Mechanical Properties of Granular Metamaterials – MICROGRAM

The aim of this project is to predict the mechanical properties of granular metamaterials. Granular packings consist of unbound macroscopic, solid particles. They have been widely studied when composed of spherical or slightly non-spherical but convex particles. Their mechanical properties are, however, mainly defined by the local interactions between the individual particles and, thus, by the shape of the particles. Therefore, significant deviations from spherical and convex particle shapes can induce so far unexplored properties of the granular packings and suggests a new family of granular material whose mechanical properties can be tuned by tailoring the shape of the constituting particles: granular metamaterials. Recently, such granular packings of complex shaped particles have been investigated e.g. as construction material. Due to the complexity introduced by the particle shape, general constitutive relations between the shape of the individual particles and the macro-mechanical properties of the packing is not feasible. We therefore plan to approach the problem by means of extensive numerical simulations which will be validated by model experiments. The required particle based simulations will be optimized such that the resulting contact networks coincide with experiments. These experiments will be performed for defined model particles and loading geometries (shear and compression). To calibrate the simulation methods, we will capture the granular packings by means of X-ray computed tomography and subsequently obtain the structure, the topology and the contact network of the packing by segmenting the individual, complex shaped particles from the CT-data. Once reliable, the simulations will be used for the mass production of data for a wide range of particle shapes. This data will permit to train an artificial neural network that will output the mechanical properties of a granular metamaterial as a function of the shape of the constituting particles.