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Owing to the architected void-filled low-density configurations, metamaterials are prone to defects during the complex manufacturing process, or damages under operational conditions. Recently mechanical cloaking has been proposed to shield the effect of such disorders in terms of homogenized mechanical responses. The major drawback in these studies are that the damage location should be known a priori, and the cloak is designed around that damaged zone before manufacturing. Such postulation does not allow unsupervised damage resilience during the manufacturing and service life of metamaterials by active reconfiguration of the stress field depending on the random and unpredictable evolution of damage. Here, we propose a radically different approach by introducing piezoelectric lattices where the effect of random appearance of any single or multiple disorders and damages with complex shapes, sizes and distributions can be shielded through active multi-physically controlled cloaks by voltage-dependent modulation of the stress fields within the cloaking region. Notably, this can be achieved without breaking periodicity and any additional material in the cloaking region unlike earlier studies concerning mechanical cloaks. The proposed active class of elastic metamaterials will bring a step-change in the on-demand mechanical performance of critically important structural components and unsupervised damage resilience for enhanced durability and sustainability. This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'. [ABSTRACT FROM AUTHOR]

AbstractTo automate the approach of assessing the health and efficacy of large structural systems globally through structural health monitoring systems, a vast network of sensors that must be mounted throughout the entire structure and connected to a continuous power supply is necessary. Clusters of wires need to be placed throughout the structures to support the network, or batteries must be changed frequently, adding to the network’s high maintenance expenses. The present study investigates the scope of powering such low-energy devices with a localized renewable energy source based on smart piezoelectric components such as PZT-patched energy harvesting systems. This paper analyses the performance of the PZT patch mounted on different structures that are predominantly activated in d31 mode. A vibration testing rig is manufactured to perform experiments for investigating the effect of material properties, natural frequencies, vibrating structural mass, and their interaction with the output power of a PZT transducer. Optimal mass, material, and structural configurations are attempted to be identified experimentally. The hypothesis, predictions, and results are evaluated further based on a converged finite element model. Subsequently, we introduce a novel concept of chiral fractal substrates in piezoelectric energy harvesters, wherein a significant improvement is noticed in the energy output along with increased frequency-band programmability. The power output of such architected and optimized energy harvesters holds the potential to serve as a reliable and sustainable alternative to conventional batteries, effectively providing a renewable source of power to energize and sustain low-power micro-electro-mechanical systems (MEMS) and devices. [ABSTRACT FROM AUTHOR]

The electromechanical responses of single and multi-layered piezoelectric functionally graded graphene-reinforced composite (FG-GRC) plates are studied based on an accurate higher-order shear deformation theory (HSDT) involving quasi-3D sinusoidal plate theory and linear piezoelectricity. These FG-GRC plates are composed of randomly oriented graphene nanoplatelets (GPLs) reinforcing fillers and the piezoelectric PVDF matrix considering two different distribution patterns such as linear- and uniform- distribution (LD and UD) of GPLs across the thickness. The modified Halpin-Tsai (HT) and Rule of mixture (ROM) models are utilized to determine the effective material properties of FG-GRCs. The analytical model of FG-GRCs is extended further to analyze the time-dependent linear viscoelastic electromechanical behavior of the system based on Biot model of viscoelasticity in the framework of inverse Fourier algorithm. The viscoelastic electromechanical responses include the static deformation and electric responses of simply supported FG-GRC plates which are investigated by considering transverse mechanical and external electrical loading, as well as other critical parameters like aspect ratio and weight fraction of GPLs. The numerical results reveal that the electromechanical response of FG-GRC plates can be enriched due to the addition of a small weight fraction of GPLs. The coupled multiphysics-based computational framework proposed here for predicting the viscoelastic electromechanical behavior of laminated composites can be exploited for stimulating and developing a wide range of micro-electro-mechanical systems (MEMS) and devices incorporating time-dependent programming features. [ABSTRACT FROM AUTHOR]