CAREER: Guiding and Confining Nonlinear Elastic Waves in Moiré Metastructures

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This Faculty Early Career Development (CAREER) grant will fund research that enables the application of new architected metamaterials to vibration protection of large-capacity wind turbine blades, as well as the design of surface acoustic wave devices capable of high-precision sensing and signal processing, thereby promoting the progress of science and advancing the national prosperity. A major impediment to scaling up the output from wind energy generation is structural failure due to vibrations of turbine blades induced by unsteady wind loads and extreme weather conditions. Without effective means to guide or isolate vibrational energy in such structures, concerns about damage and safety enforce suboptimal designs and operation. To address this challenge, this project investigates a hitherto unexplored class of engineered materials, called moiré metastructures, that can guide and confine elastic wave energy in ways that are unattainable in conventional materials. An integrated set of education and outreach activities aims to positively impact engineering education and contribute to a diverse and globally competitive STEM workforce. These include metastructure design challenges in an undergraduate course, hands-on activities at workshops for K-12 students, international student exchange with a research group in France, and participation of individuals from underrepresented groups in research.This research aims to develop the foundations for the design of a class of bilayered architected plate metastructures, coupled by nonlinear between-layer springs, that allow independent engineering of dispersion and nonlinearity and, as a result, the possibility of uniquely nonlinear wave phenomena, such as solitons, frequency combs, wave bending, and unidirectional propagation. It achieves this aim by investigating how nontrivial topological properties of moiré metastructures, obtained by stacking two layers of hexagonal, square, and Kagome lattice-based plates, result in almost flat dispersion bands that can be exploited and combined with space-time modulation of stiffness to guide or confine wave energy. The approach relies on theoretical analysis of discrete spring-mass models, finite-element analysis using discontinuous Galerkin basis functions based on Bloch modes, design optimization and fabrication of coupling springs with the desired nonlinear stiffness, and experimental validation using laser-Doppler vibrometry and high-speed imaging.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.