DEFORMATION AND FAILURE OF MICROSCALE MECHANICAL METAMATERIALS

摘要

The combination of high strength, high stiffness and low mass density requires new approaches in the field of material development. Metamaterials, whose properties are defined rather by their topology than the constituting material, represent a promising strategy for that purpose. A combination of nano- and microarchitecture and mechanical size effects results in metamaterials with a very high strength-to-density ratio. These open up new possibilities and development potential in the field of lightweight construction due to previously unattainable mechanical properties. [1] New additive manufacturing methods such as 3D direct laser writing currently enable the fabrication of different micro- and nanoscale structures with highest resolution. Additional processes such as heat treatments or coatings of the structures allow a variation and improvement in the mechanical properties. Besides high strength at low density, these include, for example, good damping properties and elastic recovery. [2] For optimized mechanical properties a detailed understanding of the deformation and failure behaviour is crucial. Therefore, microlattices of different architectures and sizes were created by 3D direct laser writing from polymers, while coatings, annealing and pyrolysis to glassy carbon were applied to expand the limits of material-property space [3]. The mechanical properties were determined by ex situ and in situ nanoindentation. The post-compression imaging was performed with a helium ion microscope to investigate the damage characteristics of the structures. Understanding the failure behaviour of different architectures are critical to meet the current challenges of scaling-up and entering the field of technological applications.[3]