The research objective of this grant is to elucidate the fundamental deformation mechanisms that govern the overall mechanical properties of material systems with competing material- and structure-induced size effects. Crystalline solids have been shown to exhibit both intrinsic/material size effects, such as the grain-size dependent strength of polycrystals, as well as extrinsic/structure-induced size effects, such as the size-dependent strength of single-crystalline micro- and nano-pillars. While both types of size effects have been studied independently, the mechanical response of material systems in which macro-structural feature size and characteristic size of the microstructure merge is a key open question for two reasons. First, experimental techniques for fabricating and testing micro- and particularly nano-scale structures are intricate and often require specialized facilities. Second, most computational models fail to describe physical phenomena, which require both a discrete atomistic description and realistic (i.e. experimentally accessible) temporal and spatial resolution. This research project will combine advanced computational models for coarse-graining atomistic simulations with novel fabrication and in situ experimental methods to synthesize and test hollow metallic nano-trusses, which will give insight into the governing deformation mechanisms and the resulting mechanical properties of nano-structural materials.
If successful, the outcome of this interdisciplinary collaborative research will be transformative in the synthesis of new materials with highly desirable properties, which have been historically coupled in limiting combinations (e.g. stiffness and weight). The gained knowledge promises to be essential for the development and improvement of structural materials, and it makes a prime example to illustrate the importance of structure-property relations in solids, which will be included in classroom and high school education. This project will train undergraduate students from both engineering and physics backgrounds through interdisciplinary research projects with special emphasis on recruiting students from underrepresented groups and women. Broad outreach activities geared towards K-12 students will offer opportunities to become involved, including a summer program for high school students who are invited to spend three to six weeks working in the labs. The PIs will provide training and career development for graduate students in an exciting interdisciplinary field to combine materials phenomena with theory and experiments. Finally, the integrated and iterative computational and experimental tasks will make a prime example for successful interdisciplinary research to close a knowledge gap across scientific disciplines.