Effective Material Characteristics Research Articles

Low-velocity impact behavior analysis on composite double curved-shell reinforced with graphene platelet

ABSTRACT This research investigates the low-velocity impact behavior of a spherical rigid body on a composite shell reinforced with graphene platelets (GPLs), in which GPL have been uniformly dispersed and randomly arranged within each individual layer. The weight proportion of GPL has been altered across the thickness. The modified Halpin Tsai model is employed to analyze the Young's modulus and the effective material characteristics of a composite reinforced with graphene platelets (GPLRC). The mass density and Poisson's ratio of the viscoelastic multilayer composite are determined using the rule of mixture. The material parameters of each layer are defined according to the Kelvin–Voigt model. The governing equations have been derived by applying the first order shear deformation shell theory, Hamilton's principle, and modifying the Hertz contact law. The PDE problems have been transformed into ODE equations through the utilization of the Galerkin method. Subsequently, the ordinary equations have been solved utilizing the Newmark method. A parametric study is conducted to examine the effects of various factors, such as fraction weight, GPL distribution pattern, impactor mass, radius, viscoelastic modulus, and initial velocity, on the low velocity impact response of a composite shell reinforced with GPL.

Clarifying the Impact of Electrode Material Heterogeneity on the Thermal Runaway Characteristics of Lithium‐Ion Batteries

The safety and efficiency of lithium‐ion batteries (LIBs) suggest a promising future for this technology, particularly in the automobile industry. However, thermal runaway—wherein a LIB undergoes an uncontrollable increase in temperature that may result in smoke, fire, or explosion—represents an important and widely studied failure type. Since the electrodes of LIBs are manufactured from porous composite materials, their heterogeneity can significantly influence the effective material characteristics and microscale behaviors of LIBs during operation. Microstructure geometric and electrochemical–thermal models are typically used to investigate these impacts. Herein, a microstructure geometric model is constructed of LIB's electrodes. A virtual multiphysics model is used to simulate the overcharging thermal runaway condition. The model's accuracy is validated through real‐world experiments. The model shows greater accuracy compared to the result from a conventional homogeneous geometric model and better reflects the heterogeneous internal phenomenon. The model is applied to a variable analysis in order to investigate how the varying heterogeneity of the cathode's porosity impacts the cell during overcharging thermal runaway behavior. Our results indicate that decreasing porosity heterogeneity at the cathode may delay thermal runaway, owing to the heterogeneous impact on particle diffusion behaviors and the side reaction rate.

Vibration characteristics of multilayer functionally graded microplates with variable thickness reinforced by graphene platelets resting on the viscoelastic medium under thermal effects

Due to their improved mechanical properties and adaptability, microplates with tailored variable thickness profiles are becoming essential parts of advanced micro- and nanoelectromechanical systems (MEMS and NEMS). This study conducts a thorough analytical analysis of the vibration properties of thermally loaded, multilayer functionally graded graphene platelet-reinforced composite (FG-GPLRC) microplates of linearly or parabolically varying thickness resting on viscoelastic medium under different boundary conditions. The Halpin–Tsai micromechanical model and the law of mixtures are employed to calculate the effective material characteristics for various reinforcement distributions in the microplate. These distributions encompass uniformly symmetric and asymmetric arrangements. The study utilized the first-order shear deformation theory (FSDT) in conjunction with the modified strain gradient theory (MSGT) and Hamilton's principle to generate the dynamic governing equations for the structure, accounting for size-dependent effects. The resulting equations are afterwards solved using the utilization of the Galerkin technique. This enables the evaluation of the proposed solution's correctness and precision. The impact of various factors on vibration behavior is investigated through numerical analysis. These factors encompass length scale parameters, temperature fluctuations, temperature distribution profiles, boundary conditions, the distribution pattern of the GPL, taper constants in both unidirectional and bidirectional scenarios, the weight fraction of the GPL.

Spectro-geometric solutions for random vibration of functionally graded graphene platelet reinforced conical shells

This study delved into the random vibration characteristics of a conical shell constructed from a functionally graded graphene platelet-reinforced composite (FG-GPLRC) under the influence of basic acceleration excitation. The investigation employed a synthesis of two methodologies: the spectro-geometric method (SGM) and the pseudo-excitation method (PEM). Commencing with the application of the Halpin–Tsai micromechanics approach and the law of mixtures, the effective material characteristics of the FG-GPLRC structure were determined. Subsequently, the displacement field vector for the conical shell structure was established with SGM. By employing the framework of the first-order shear deformation theory (FSDT), the energy function of the FG-GPLRC conical shell was derived, with external random excitation energy being incorporated with PEM. To construct a dynamic model for the conical shell structure, the Rayleigh-Ritz method was applied, subjecting the energy function to variational extremization. This approach yielded a comprehensive dynamic representation. The validity of the proposed model was substantiated through comparison with existing literature and finite element method results. Ultimately, this study explored the influence of graphene material properties and geometric parameters of the conical shell on the random vibration characteristics of the FG-GPLRC conical shell.

Dynamic homogenization of heterogeneous piezoelectric media: A polarization approach using infinite-body Green’s function

Dynamic homogenization theories are powerful tools for describing and understanding the behavior of heterogeneous media such as composites and metamaterials. However, a major challenge in the homogenization theory is determining Green’s function of these media, which makes it difficult to predict their effective constitutive relations, particularly for the finite-size and/or non-periodic media in real-world applications. In this paper, we present a formulation for finding the elastodynamic effective constitutive relations for general heterogeneous media, including finite-size and non-periodic ones, via a polarization approach based on the Hashin–Shtrikman principle along with Green’s identities. Our proposed formulation relies on the infinite-body Green’s function of a homogeneous reference medium, making it free from the difficulty of determining Green’s function even for the homogenization of finite-size and/or non-periodic media. Additionally, we demonstrate the universal applicability of this formulation for both random and deterministic heterogeneous media. This work contributes to a better understanding of the homogenization theory and the design of next-generation metamaterials that require the accurate prediction of effective material characteristics for dynamic wave manipulation under desired operating environments.

Size effects in numerical homogenization of polycrystalline silicon

AbstractA current topic in the photovoltaic industry is the analysis and evaluation of possible structural and material properties. This requires the effective material characteristics of polycrystalline silicon, which is an important component for the functional performance of the photovoltaic modules in use. Since this assessment is associated with high costs, it is to be carried out already in the product development process. Due to very thin silicon layers, the effect of the layer thickness on the effective material characteristics has to be investigated (see ). In this work, a procedure to determine these characteristic values is listed to investigate the size effect on different film thicknesses of this material (see ). With the knowledge of the properties of the silicon single crystal with its cubic symmetry on the micro level, a homogenization of the properties to the macro level can be done. The polycrystal structure with a cubic sample geometry forms the macro level. This structure is now cut into thinning layers for investigation. The open‐source software Neper is used to create the crystal structure and the inter‐connectivity for this purpose. With the help of Matlab, this information is passed on to the finite element program Abaqus, where the results are evaluated after an elastic calculation using Python. The focus is on the expected change in material properties as a function of the layer thickness.

Geometrically Nonlinear Study of Functionally Graded Saturated Porous Plates Based on Refined Shear Deformation Plate Theory and Biot’s Theory

This research presents the geometrically nonlinear investigation of functionally graded saturated porous material (FGSPM) plate under undrained conditions. In conjunction with von Karman’s nonlinearity, the refined shear deformation plate theory (RSDPT) is implemented to model the FGSPM plate. The effective material characteristics of the saturated porous plate change constantly in the thickness direction. The pores of the saturated porous plate are examined in fluid-filled conditions. Thus, the constitutive equations are established using Biot’s linear poroelasticity theory. The governing equations are developed by combining a nonlinear finite element technique with Hamilton’s principle. Then, the direct iterative approach is utilized to extract the geometrically nonlinear numerical results. The emphasis is placed on exploring the effects of numerous parameters such as Skempton coefficient, volume fraction grading index, porosity volume index, porosity distributions, and boundary conditions during the extensive numerical analyses on the linear frequency, large amplitude frequencies, and nonlinear central deflections of the FGSPM plate. It is evident from the investigation that saturated fluid in the pores substantially impacts the nonlinear deflection and vibration behavior of the FGSPM plate.

The free vibration analysis of carbon nanotubes-reinforced deep conical shells with an intermediate ring support under various boundary conditions

This article explores the free vibration characteristics of a conical shell strengthened with intermediate ring. The system is thought to be made up of a linearly elastic nanocomposite that is reinforced with carbon nanotubes (CNTs). To get the effective material characteristics, the modified rule of mixtures is employed. To account for shear deformations and rotational inertias occurring across the depth of the shell, the first-order model of shells is combined with Donnell’s classical kinematic constraints. Hamilton’s principle is applied to construct the generic motion equations and their related boundary and compatibility constraints. The resulting set of equations is solved analytically in the structure’s circumferential direction. Additionally, the generalized differential quadrature element (GDQE) algorithm is performed to discretize the radial motion equations. An eigenvalue issue is constructed with various edge conditions for the structure boundaries and compatibility conditions to investigate the vibration frequencies. After demonstrating the efficacy and accuracy of the current approach for applying functionally graded (FG) CNT reinforced composite (RC) cylindrical shells with intermediate circle support, several parametric investigations are conducted to determine the effect of the geometric and ingredient properties of FG-CNTRC conical shells.

Comprehensive numerical characterization of a piezoelectric composite with hollow metallic inclusions using an adaptable random representative volume

This paper investigates a piezoelectric composite made up of a piezoceramic matrix with irregularly scattered random-sized hollow metal inclusions. This composite can be produced using a combination of porous ceramic fabrication methods and microcapsule transfer techniques that were previously utilized to deliver nanoparticle medicines in biomedical applications. The effective material characteristics were computed using a numerical homogenization methodology that included finite element analysis, random representative volume element, perfect contact between distinct phases, special linear boundary conditions, and the Hill–Mandel principle. To imitate the random distribution of inclusions inside a particle-filled composite, the relationship describing the inclusion’s volume fraction was adjusted by adding a regularity coefficient. Thus, a new representative volume was designed to study the effect of the non-uniform distribution of randomly sized inclusions on the effective coefficients of the composite. An analysis of the effective properties of this new composite system with metalized pores surfaces (SMPS) revealed the following features. Due to the presence of metallic impurities, the resulting electric induction field or mechanical stress field inside the piezoelectric phase is scattered, which raises the transverse piezoelectric moduli with the increase of the inclusion’s volume fraction. Also, the electrical permittivity coefficients increase steadily with the increase in the portion of the metallic impurities. According to the findings, the volume fraction of the inclusion can be considered the most critical parameter to modify the electromechanical characteristics of the SMPS. The effects of the regularity coefficient on the equivalent properties increase as the inclusion’s volume fraction increases. The effective dielectric constants decrease as the degree of regularity of the composite structure grows, increasing the effectiveness of the piezoelectric transducer in transverse energy harvesting and motor applications. The findings of the newly constructed representative volume were verified using a basic periodic unit-cell and a random representative volume based on the random sequential adsorption (RSA) method. The developed structure of the representative volume can be applied to simulate a wide range of composites in the form of solid particles. Piezoelectric transducers constructed from the proposed piezocomposite are predicted to function well in piezoelectric motors and transverse piezoelectric sensors.

Micro-macro modelling of laminated composite rectangular reservoir

This article has a multidisciplinary character. It combines the scientific field of micro-macro modelling of reinforced polymer composite laminates applied in the seismic response area of a rectangular composite tank filled with liquid. The calculation of the seismic response of the laminate composite rectangular tank is carried out at three levels. Within the micro-level, the material characteristics are calculated using a fictitious periodic microstructure model. A classical theory of laminates is used to obtain effective material characteristics by using a representative laminate volume element at the meso-level. At the macro level, a seismic response of a laminate composite rectangular tank filled with liquid is solved for the region of Slovakia.

Development of a macroscale constitutive model for porous magneto‐ active polymers using a computational homogenization approach

AbstractOver the last years there has been a growing interest in the study of the behavior of field‐responsive or so called smart materials. Porous magnetoactive polymers (MAPs) are a special class of these materials, where micron‐sized ferromagnetic particles are embedded into a porous crosslinked polymer matrix. Due to the mutual interaction of the particles upon magnetic stimulation, MAPs are able to deform and alter their effective material characteristics reversibly if subjected to a magnetic field. This strong magneto‐mechanical coupling makes them attractive for engineering applications e.g. in the field of sensors and actuators. The magneto‐mechanical behavior of porous MAPs is a complex phenomenon that spans over multiple length‐scales and essentially depends on (i) the constitutive behavior of the individual components, (ii) their morphology and microstructural arrangement and (iii) the macroscopic shape of the specimen. The strong shape effects pose a crucial challenge in the precise parameter identification of macroscopic models for MAPs based on experiments, see Keip & Rambausek [6] and Gebhart et al. [2, 3]. In order to circumvent these inherent problem, we propose a microscopic continuum‐based framework embedded into a suitable computational homogenization scheme to bridge between the micro‐ and macroscale, see Chatzigeorgiou et al. [1]. This modeling approach allows us to use much simpler constitutive models on the microscopic scale for which detailed and precise material parameters are available, see Kalina et al. [4, 5]. The proposed framework is then used to predict the effective macroscopic behavior of porous MAPs with random monodisperse microstructures. Based on the generated data set a thermodynamically consistent macroscale model for isotropic porous MAPs in an energy‐based constitutive setting is developed.

Dynamic Stability Analysis in Hybrid Nanocomposite Polymer Beams Reinforced by Carbon Fibers and Carbon Nanotubes.

The objective of this innovative research is assessment of dynamic stability for a hybrid nanocomposite polymer beam. The considered beam formed by multiphase nanocomposite, including polymer–carbon nanotubes (CNTs)–carbon fibers (CFs). Hence, as to compute the effective material characteristics related to multiphase nanocomposite layers, the Halpin–Tsai model, as well as micromechanics equations are employed. To model the structure realistically, exponential shear deformation beam theory (ESDBT) is applied and using energy methods, governing equations are achieved. Moreover, differential quadrature method (DQM) as well as Bolotin procedures are used for solving the obtained governing equations and the dynamic instability region (DIR) relative to the beam is determined. To extend this novel research, various parameters pinpointing the influences of CNT volume fraction, CFs volume percent, boundary edges as well as the structure’s geometric variables on the dynamic behavior of the beam are presented. The results were validated with the theoretical and experimental results of other published papers. The outcomes reveal that increment of volume fraction of CNT is able to shift DIR to more amounts of frequency. Further, rise of carbon fibers volume percent leads to increase the excitation frequency of this structure.

Multiphysics modeling and simulation of fluid‐saturated porous ferrogels at finite strains

AbstractOver the last years there has been a growing interest in the study of the behavior of field‐responsive or so called smart materials. Porous ferrogels are a class of these materials consisting of a porous polymeric matrix with dispersed micro‐ or nano‐sized ferromagnetic particles [1–3]. Due to their ability to exhibit large deformations and alter their effective material characteristics upon external magnetic stimulation, these materials are interesting for a wide range of applications in biomedical engineering, microfluidics and other innovative fields of research. The magneto‐poro‐mechanical response of porous ferrogels is a complex phenomenon that spans over multiple length‐scales and essentially depends on (i) the constitutive behavior of the individual components, (ii) their morphology and microstructural arrangement and (iii) the macroscopic shape of the specimen. In this contribution a theoretical and computational framework for the modeling of isotropic porous ferrogels at the macroscale is presented. Within this modeling approach the porous ferrogel is treated as a homogeneous continuum, whereat its complex microstructure is not resolved explicitly. A prototypical isotropic constitutive model is formulated in a conventional enthalpy‐based setting. Numerical examples show the the crucial impact of the macroscopic specimen shape on the macroscopic deformation response in an uniform external magnetic field.

Micro-stiffener surface characteristics with belt polishing processing for titanium alloys

Titanium alloys with effective material characteristics are widely applied to the design of significant components of aero-engines, such as the blisk, blade, and commutator, and it is very important to create under requirement surface integrity to improve fatigue life by using advanced manufacturing technology, under the requirements of surface integrity for titanium alloy parts. In this paper, the method of micro-stiffener belt polishing (MSBP) is presented to realize anti-fatigue surface, which is based on the influence rule of the thin-plate stiffener on the bending life and the micro-crack principle. Thereafter, the surface characteristics and formation of titanium alloy MSBP are revealed by comparing analyses of the different polishing processes, using numerical simulation and advanced measuring. The belt polishing processes of reciprocating and high-speed rotation are used to form the micro-stiffener and smooth surface, respectively, while the different surface characteristics are obtained by adjusting the feeding speed and pressure. The formation rules of the surface characteristics are analyzed according to material removal under flexible contact conditions. The surface topography is expressed by the wavelet transform and polishing moving model, following which the surface topography is analyzed by means of comparison with the electron microscope test results. The workpiece surface residual stress is tested by an X-ray projector, and the distribution of different depth residual stresses is predicted by finite element analysis. The surface profile is obtained by a contour-graph, based on which the surface roughness distribution is obtained. The experimental results demonstrate that the surface characteristics, surface topography, surface roughness, and residual stress all meet the requirements. Furthermore, the micro-stiffener surface characteristics are superior to those of the smooth surface, particularly in terms of consistency. Therefore, the new method can be used to improve the surface integrity characteristics using the micro-stiffener for titanium alloy materials.

Identification of Effective Material Characteristics in Semilinear Equations of Heat and Mass Transfer

Utilization of advanced materials in civil engineering motivates research in both experimental and computational methods of reliable identification of their material characteristics, as e.g. the thermal conductivity and diffusivity in semilinear evolutionary equations of heat conduction, coming from the energy balance in classical thermodynamics, or the capillary transfer coefficient in similar equations, coming from the mass balance. The paper presents mathematical preliminaries of such inverse analysis and an overview of computational approaches with references to practical applications.

Generalized self‐consistent like method for mechanical degradation of fibrous composites

AbstractThis paper deals with homogenization of heterogeneous, fibre‐reinforced material. One of the main points of the work consists in taking into account the breakage of the fibres, to compute the effective behaviour of the damaged composite. Furthermore, the possible yielding of the matrix material is considered. The problem is solved for the coupled thermo‐mechanical field, that is all material characteristics can be temperature dependent and thermal loads can be simulated. The method is based on a self consistent type scheme, suitably extended for the case at hand. The effective behaviour is obtained by considering isotropic elastic‐brittle cylindrical inclusions surrounded by a shell of elasto‐plastic matrix material immersed in an infinite medium endowed with the effective properties. Usually in the framework of the self consistent scheme, the homogenised material behaviour is obtained with a symbolic approach. On the contrary, in this work the solution is found in a non‐classical way, as we use the finite element method to find the solution of the thermo‐mechanical problem as a function of the effective material characteristics.