Active multi-physical modulation of Poisson's ratios in composite piezoelectric lattices: On-demand sign reversal. (15th January 2022) - Singh, A.
Abstract: A large number of studies have been reported in literature to analyse various parameters that influence the Poisson's ratios of multi-functional lattice materials. However, the major limitation in such lattices is that once the lattice is manufactured, the Poisson's ratios and other elastic properties become fixed corresponding to the particular lattice configuration. This limits the application of such lattices in many advanced multi-functional structures and systems, where on-demand active property modulations are warranted. This paper proposes composite lattices comprising a substrate and piezoelectric materials, wherein it is possible to actively modulate the Poisson's ratios and other elastic properties as a function of voltage. Considering both axial and transverse deformations of the cell walls along with a unit cell based approach, the exact closed-form expressions of Poisson's ratios and equivalent Young's modulus are derived in an expanded design space for the unimorph and bimorph configurations. The study reveals that a sign reversal of the Poisson's ratios and Young's modulus can be achieved for specific combinations of cell angle and applied voltage. Contrary to the conventional wisdom, such active sign reversal implies that re-entrant honeycomb lattices can exhibit positive Poisson's ratios and vice versa. Graphical abstract: Highlights: Hybrid composite lattices comprising a substrate and piezoelectric materials are proposed, wherein it is possible to actively modulate the Poisson's ratios and other elastic properties as a function of voltage. Considering both axial and transverse deformations of the cell walls along with a unit cell based approach, the exact closed-form expressions of Poisson's ratios and equivalent Young's modulus are derived for the unimorph and bimorph configurations. The major limitation in conventional lattice materials is that on-demand active property modulation is not feasible once the lattice is manufactured, limiting the applications in many advanced multi-functional structures and systems. The current proposition presents a panacea for the active structural demands of modern systems. The study reveals that a sign reversal of the Poisson's ratios and Young's modulus can be achieved for specific combinations of cell angle and applied voltage. Contrary to the conventional wisdom, such active sign reversal implies that re-entrant honeycomb lattices can exhibit positive Poisson's ratios and vice versa. This investigation provides necessary physical insights and generic background for potential practical applications in various futuristic multi-functional structural systems and devices across different length scales, concerning the active modulation and control of elastic moduli and shapes.