A Framework for Size-dependent Structural Analysis of Smart Micro/nanoplates

This age has witnessed a proliferation of technological advancements that affected all facets of civilisation. Driven by the joint force of the evolution of sophisticated design tools, tailored material characteristics, and robust mechanics-based analyses, smart composite materials are widely used in high-performance engineering applications. Meanwhile, there is a growing interest in micro/nanoscopic structures in academia and industry due to the overwhelming trend toward portability, miniaturisation and integration in engineering. Therefore, the theoretical, computational, and experimental research communities have developed various effective methodologies to understand the structural behaviour of smart small-scale structures comprehensively. This dissertation introduces two size-dependent continuum theories, modified strain gradient and nonlocal strain gradient theories, to build the analytical framework for exploring application-driven micro/nanoplates made of smart composite materials. As examples of promising candidates for power supply and nano/microelectromechanical systems, organic solar cells and thermo-magneto-elastic sandwich nanoplates are studied. Size-dependent continuum models combined with various shear deformation plate theories are adopted to derive the governing equations. The size-sensitive static and dynamic mechanical responses, including bending, buckling, and free vibration behaviours of these ultra-fine-size structures, are predicted by capturing the size effect with material length scale or nonlocal parameters. The numerical results underlying size-dependent theories pose a new insight into the structural analysis of functional micro/nanoscopic plate-like structures. Some typical size-involving mechanical characteristics are revealed by comparing the present estimation with those from size-independent models. Moreover, the simulation outcomes thoroughly investigate several practical factors, such as boundary conditions, geometric configuration, and elastic foundation modelling parameters. In this endeavour, taking advantage of the computational efficiency and accessible operation of nonclassical continuum-based theories, the current analytical framework is suitable for exploring the size-tendency of the smart micro-/nanosized structures. The present work may serve as a benchmark for following numerical simulations and as a guide for evolving new engineering tools for modelling relevant responses by designers and manufacturers

Recent Advances in Theoretical and Computational Modeling of Composite Materials and Structures

The advancement in manufacturing technology and scientific research has improved the development of enhanced composite materials with tailored properties depending on their design requirements in many engineering fields, as well as in thermal and energy management. Some representative examples of advanced materials in many smart applications and complex structures rely on laminated composites, functionally graded materials (FGMs), and carbon-based constituents, primarily carbon nanotubes (CNTs), and graphene sheets or nanoplatelets, because of their remarkable mechanical properties, electrical conductivity and high permeability. For such materials, experimental tests usually require a large economical effort because of the complex nature of each constituent, together with many environmental, geometrical and or mechanical uncertainties of non-conventional specimens. At the same time, the theoretical and/or computational approaches represent a valid alternative for designing complex manufacts with more flexibility. In such a context, the development of advanced theoretical and computational models for composite materials and structures is a subject of active research, as explored here for a large variety of structural members, involving the static, dynamic, buckling, and damage/fracturing problems at different scales

Thermal buckling of functionally graded piezomagnetic micro- and nanobeams presenting the flexomagnetic effect

Galerkin weighted residual method (GWRM) is applied and implemented to address the axial stability and bifurcation point of a functionally graded piezomagnetic structure containing flexomagneticity in a thermal environment. The continuum specimen involves an exponential mass distributed in a heterogeneous media with a constant square cross section. The physical neutral plane is investigated to postulate functionally graded material (FGM) close to reality. Mathematical formulations concern the Timoshenko shear deformation theory. Small scale and atomic interactions are shaped as maintained by the nonlocal strain gradient elasticity approach. Since there is no bifurcation point for FGMs, whenever both boundary conditions are rotational and the neutral surface does not match the mid-plane, the clamp configuration is examined only. The fourth-order ordinary differential stability equations will be converted into the sets of algebraic ones utilizing the GWRM whose accuracy was proved before. After that, by simply solving the achieved polynomial constitutive relation, the parametric study can be started due to various predominant and overriding factors. It was found that the flexomagneticity is further visible if the ferric nanobeam is constructed by FGM technology. In addition to this, shear deformations are also efficacious to make the FM detectable

Nonlinear Dynamic Behaviour of Solar Cells with Advanced Materials

The advanced solar structure (perovskite solar cell) (PSC) has fascinated both the scientific community and contemporary industry due to the high efficiency, low fabrication cost, abundant raw material, and distinguished electro-optic properties. Whereas, along the journey towards real-life implementation of the novel PSC, the mechanical performance and dynamic behaviour, as well as nonlinear stability of the structure are still not examined. Such investigation is tightly pertinent to device operating capacity and safety, and represents a key issue for commercial production. In addition, feasible reinforcement through advanced composite materials for the PSC is still an open problem, which is crucial for guaranteeing product serviceability. Moreover, the manifold practical influences within PSC’s working conditions are yet not fully explored, which can exert a critical impact on structural performance and dynamic attributes. Hence in this dissertation, an analytical framework is developed for analysing the mechanical capacity and nonlinear dynamic behaviour of the advanced solar panel and novel composite structures subjected to various realistic impulses. The innovative graphene platelets reinforced functionally graded porous stiffeners and oblique stiffeners have been involved to enhance the composite stiffness and stability. Moreover, different laminate plate theories have been incorporated to effectively handle thick to ultra-thin structures. The nonlinear motion equations are derived based on the Galerkin method. Then, the fourth-order Runge-Kutta method is leveraged to capture the mechanical performance and nonlinear response. Through comparing with results from finite element software and established benchmarks, the accuracy, effectiveness, and applicability of the developed framework have been verified. In addition, extensive practical effects, such as the damping, temperature alteration, wind load, elastic foundations, initial imperfection, active layer, blast impact, and multiple impulse loadings, on mechanical attributes and structure response under disparate support conditions have been identified systematically. By determining the optimal parameters of novel composite stiffeners, the dynamic performance and impact resistance of the PSC have been intensified. The proposed study will be beneficial to the modern design and practical deployment of energy-harvesting devices with improved mechanical capability, stability, and safety

Advances in Micro- and Nanomechanics

This book focuses on recent advances in both theoretical and experimental studies of material behaviour at the micro- and nano-scales. Special attention is given to experimental studies of nanofilms, nanoparticles and nanocomposites as well as tooth defects. Various experimental techniques were used. Magneto- and thermoelastic coupling were considered, as were nonlocal models of thin structures

Mesh-Free and Finite Element-Based Methods for Structural Mechanics Applications

The problem of solving complex engineering problems has always been a major topic in all industrial fields, such as aerospace, civil and mechanical engineering. The use of numerical methods has increased exponentially in the last few years, due to modern computers in the field of structural mechanics. Moreover, a wide range of numerical methods have been presented in the literature for solving such problems. Structural mechanics problems are dealt with using partial differential systems of equations that might be solved by following the two main classes of methods: Domain-decomposition methods or the so-called finite element methods and mesh-free methods where no decomposition is carried out. Both methodologies discretize a partial differential system into a set of algebraic equations that can be easily solved by computer implementation. The aim of the present Special Issue is to present a collection of recent works on these themes and a comparison of the novel advancements of both worlds in structural mechanics applications

Mechanics of Micro- and Nano-Size Materials and Structures

For this reprint, we intend to cover theoretical as well as experimental works performed on small scale to predict the material properties and characteristics of any advanced and metamaterials. New studies on mechanics of small-scale structures such as MEMS/NEMS, carbon and non-carbon nanotubes (e.g., CNTs, Carbon nitride, and Boron nitride nanotubes), micro/nano-sensors, nanocomposites, macrocomposites reinforced by micro-/nano-fillers (e.g., graphene platelets), etc., are included in this reprint

A new mixed model based on the enhanced-Refined Zigzag Theory for the analysis of thick multilayered composite plates

The Refined Zigzag Theory (RZT) has been widely used in the numerical analysis of multilayered and sandwich plates in the last decay. It has been demonstrated its high accuracy in predicting global quantities, such as maximum displacement, frequencies and buckling loads, and local quantities such as through-the-thickness distribution of displacements and in-plane stresses [1,2]. Moreover, the C0 continuity conditions make this theory appealing to finite element formulations [3]. The standard RZT, due to the derivation of the zigzag functions, cannot be used to investigate the structural behaviour of angle-ply laminated plates. This drawback has been recently solved by introducing a new set of generalized zigzag functions that allow the coupling effect between the local contribution of the zigzag displacements [4]. The newly developed theory has been named enhanced Refined Zigzag Theory (en- RZT) and has been demonstrated to be very accurate in the prediction of displacements, frequencies, buckling loads and stresses. The predictive capabilities of standard RZT for transverse shear stress distributions can be improved using the Reissner’s Mixed Variational Theorem (RMVT). In the mixed RZT, named RZT(m) [5], the assumed transverse shear stresses are derived from the integration of local three-dimensional equilibrium equations. Following the variational statement described by Auricchio and Sacco [6], the purpose of this work is to implement a mixed variational formulation for the en-RZT, in order to improve the accuracy of the predicted transverse stress distributions. The assumed kinematic field is cubic for the in-plane displacements and parabolic for the transverse one. Using an appropriate procedure enforcing the transverse shear stresses null on both the top and bottom surface, a new set of enhanced piecewise cubic zigzag functions are obtained. The transverse normal stress is assumed as a smeared cubic function along the laminate thickness. The assumed transverse shear stresses profile is derived from the integration of local three-dimensional equilibrium equations. The variational functional is the sum of three contributions: (1) one related to the membrane-bending deformation with a full displacement formulation, (2) the Hellinger-Reissner functional for the transverse normal and shear terms and (3) a penalty functional adopted to enforce the compatibility between the strains coming from the displacement field and new “strain” independent variables. The entire formulation is developed and the governing equations are derived for cases with existing analytical solutions. Finally, to assess the proposed model’s predictive capabilities, results are compared with an exact three-dimensional solution, when available, or high-fidelity finite elements 3D models. References: [1] Tessler A, Di Sciuva M, Gherlone M. Refined Zigzag Theory for Laminated Composite and Sandwich Plates. NASA/TP- 2009-215561 2009:1–53. [2] Iurlaro L, Gherlone M, Di Sciuva M, Tessler A. Assessment of the Refined Zigzag Theory for bending, vibration, and buckling of sandwich plates: a comparative study of different theories. Composite Structures 2013;106:777–92. https://doi.org/10.1016/j.compstruct.2013.07.019. [3] Di Sciuva M, Gherlone M, Iurlaro L, Tessler A. A class of higher-order C0 composite and sandwich beam elements based on the Refined Zigzag Theory. Composite Structures 2015;132:784–803. https://doi.org/10.1016/j.compstruct.2015.06.071. [4] Sorrenti M, Di Sciuva M. An enhancement of the warping shear functions of Refined Zigzag Theory. Journal of Applied Mechanics 2021;88:7. https://doi.org/10.1115/1.4050908. [5] Iurlaro L, Gherlone M, Di Sciuva M, Tessler A. A Multi-scale Refined Zigzag Theory for Multilayered Composite and Sandwich Plates with Improved Transverse Shear Stresses, Ibiza, Spain: 2013. [6] Auricchio F, Sacco E. Refined First-Order Shear Deformation Theory Models for Composite Laminates. J Appl Mech 2003;70:381–90. https://doi.org/10.1115/1.1572901