Structural Metamaterials with Saint-Venant Edge Effect Reversal for Static Load Pattern Modification and Recognition

University Of Illinois At Chicago, Chicago IL

Investigators

Abstract

This award supports fundamental research leading to a new class of mechanical metamaterials that, unlike the traditional materials, respond stronger to finer spatial fluctuations in loads than to coarser ones. The notion of metamaterials refers to an exciting class of material systems with engineered internal structure. Specially designed interactions among individual elements of the internal structure lead to a reversal of certain basic properties observed in natural materials. These new properties unveil practical opportunities that can be highly beneficial to the society. For example, photonic metamaterials may be used to fabricate ultrathin lenses for medical applications, and acoustic metamaterials can provide highly efficient sound insulation and earthquake hazard mitigation systems. They will also potentially enable in-situ identification of unsafe loading conditions in structures and building foundations. The paradigm changing aspects of this work will help to inspire undergraduate students and underrepresented groups to participate in the research activities through undergraduate research experiences and the submission of manuscripts in the ASEE Journal of Engineering Education. This research will create a sufficient base of knowledge to enable design and fabrication of these novel metamaterials. The concept of deformation decay spectrum will be introduced on the basis of transfer matrix eigenanalysis of a discrete nonlocal elastic medium in the Fourier domain. Based on the decay spectrum and density of states analyses, phase diagrams will be constructed in the design space of interesting candidate structures to show what combinations of structural parameters are suitable for an actual metamaterial. Availability of asymptotic bandgaps in the decay spectrum will indicate that the metamaterial behavior is achievable for a given nonlocal medium. Mathematically, these bandgaps will require complex-valued decay parameters, as a nonlinear function of the Fourier mode index in a fundamental solution to the governing equation of equilibrium of the nonlocal medium. A complex decay parameter will point out on certain anomalies in the behavior of static Fourier modes in the material, including phase shift and inversion, and mode blockage at surfaces accompanied by the Saint-Venant edge effect reversal. These basic phenomena will be shown to create opportunities for static deformation cloaking, filtering and inversion. More broadly, they will lead to functional metamaterials for qualitative modification and recognition of surface load patterns.