Material with Tunable Constitution for Elastodynamic Deformation

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Structural composites are materials consisting of two or more constituent materials with different properties, that when combined, exhibit unique mechanical properties. The individual constituents can be chosen and arranged to achieve desirable properties, such as high stiffness and low density. In a conventional composite, however, these properties are constant and cannot be changed without permanently changing the structure or composition of the material. This award supports fundamental research to enable the analysis and design of a new class of composite materials that are tunable on-demand and on-the-fly. These tunable materials will feature internal networks of flow channels that allow active tuning of the density, elastic constants, and damping properties. The tunable composites enable fundamentally new strategies for the control of vibration and acoustics across a wide range of applications. This research combines several disciplines including elastodynamics, constitutive modeling, dynamic homogenization, fluid-structure interaction, band structure calculations, and design optimization. The multi-disciplinary nature of the research will provide a stimulating setting for students who will participate in this project and broaden participation of underrepresented groups in research. Outreach activities will attract K-12 students to the design of engineered materials with tunable properties and the underlying concepts pertaining to wave motion and mechanics of materials.The specific objectives of this project are to establish a rigorous dynamic homogenization theory for the tunable composites. The theory will account for the effects of dissipation on the composite properties. This theory will be used towards the analysis and design of fluidic metamaterials consisting of periodic arrays of resonators intertwined with a built-in network of flow channels with varying fluid composition and flow conditions. A topology optimization scheme will be established to maximize the real-time performance of the emerging fluid-structure material system. Building upon Bloch theory for harmonic wave propagation, the research on dynamic homogenization will establish a methodology for obtaining frequency-dependent effective properties for the density, damping, and elasticity tensors. A computational framework based on a finite-element time-domain scheme will be created for computing the band structure of the coupled fluid-structure system. A gradient-driven topology optimization methodology using level sets and the extended finite element method will be explored to optimally arrange fluid and solid phases. The resulting tunable metamaterial represents a major transformation to what constitutes a multi-functional composite that is intrinsically dynamic, adaptive, and energy absorbing, providing unprecedented new opportunities for sound and vibration control.