Porosity Volume Fraction Research Articles

Impact response analysis of stiffened sandwich functionally graded porous materials doubly-curved shell with re-entrant honeycomb auxetic core

Owing to unique deformation behavior and high capacity of energy absorption, auxetic structures have garnered significant research attention. To reveal the energy-absorbing properties of the auxetic structure, the impact response of stiffened sandwich functionally graded porous materials (FGPM) doubly-curved shell with re-entrant honeycomb auxetic core is studied by the established analytical model in the present work. The material properties in the thickness direction of FGPM face sheets are adjusted according to the volume fraction of constituents by power law and exponential law, while the core layer is made of the re-entrant honeycomb auxetic core with negative Poisson's ratio. On the basis of the Hertz theory for elastic impacts and the first-order shear deformation theory (FSDT), an analytical model is developed to study its impact phenomenon. Equations of motion are derived using Hamilton's principle, which are further solved analytically using Navier's technique of assuming unknown variables in the double trigonometric series. The time-dependent contact force is obtained by applying the spring-mass (SM) model consisting two-degrees-of freedom. Afterward, the transverse central displacements of the stiffened sandwich FGPM doubly-curved shell are calculated by adopting the Duhamel integration. The impact force and transverse displacements are compared with the previously published results, indicating that the theoretical results agree with the previously published results.Parametric analyses have been carried out to investigate the effect of variation of various parameters such as volume fraction exponents, radii of principal curvatures, porosity volume fraction, core layer inclined angle on the impact response of the sandwich shell. Additionally, the results show that compared with the traditional hexagonal honeycomb core type, the stiffened sandwich FGPM doubly-curved shell with re-entrant honeycomb core type has significant advantages in impact energy absorption. This work may provide an extensive reference and valuable guidance in the impact design and application of auxetic sandwich shell structures.

Thermal Vibration Analysis of Sandwich Cylindrical Shells with Porous FGM Surface Layers

This study aims at investigating the thermal vibration characteristics of sandwich cylindrical shells consisting of two surface layers crafted from functionally graded materials (FGMs) and a central metal core layer. The sandwich cylindrical shells with FGMs surface layers, with and without porosity, are modelled by using the Kirchhoff–Love shell theory. A porosity function composed of three distinct parts is introduced, including the core-to-thickness ratio, porosity volume fraction, and porosity distribution function. Through the function, the significant effects of porosity that varies with the mixing degree of constituent materials can be analyzed. The material properties are assumed to be temperature-dependent and they show continuous graded variation along the thickness direction. A theoretical approach for analyzing thermal strain energy in the cylindrical shells subjected to thermal environments is established by incorporating Green’s nonlinear strains. The governing equations are derived by applying Hamilton’s principle. Subsequently, analytical solutions for the system’s natural frequencies are determined. Further, to validate the analytical results, a comparative analysis is conducted, drawing upon numerical simulations and other data available in the open literature. Additionally, the thermal vibration characteristics of the composite shell structures are examined in a comprehensive study with respect to various parameters such as porosity type, porosity volume fraction, core-to-thickness ratio, power-law exponent, and temperature changes.

Analyzing the buckling of FGCNT-reinforced sandwich microshells in heart pacemakers: The impact of thickness stretching on third-order shear deformation

This study focuses on the buckling behavior of composite microshells inside pacemakers to select the most durable material. Due to the strong electromagnetic forces encountered by pacemaker microshells, comprehensive research is needed to identify suitable materials. This study analyzes the buckling behavior of a porous sandwich cylindrical microshell attached to electrodes, which is supported by an elastic foundation and reinforced with functionally graded carbon nanotubes. Three porosity models are considered for the core material, and the equilibrium equations are derived using Hamilton’s principle based on third order shear deformation theory. This study compares the critical buckling loads with those from the literature and examines the effects of various parameters, such as thickness stretching and non-stretching. The findings indicate that the thickness stretching effect has a significant influence on the critical buckling load. In addition, a lower functionally graded power index and higher porosity volume fraction result in higher critical buckling loads. These results are relevant for micro-electromechanical systems and can aid in the selection of appropriate materials for pacemaker microshells to improve their durability and performance.

Thermomechanical Response of Functionally Graded Ti-6Al-4V and Zirconia Biomaterial Plates

This article studies the free vibration responses of functionally graded material (FGM) porous nanoplates exposed to thermal load. The developed mathematical model includes a shear deformation, size-scale, and microstructure influence by a high-order shear deformation (HSDT) and nonlocal strain gradient (NGST) theories. The study considers four different porosity patterns across the thickness: uniform, symmetrical, asymmetric bottom, and asymmetric top distributions. The equation of motion of the FGM porous nanoplate, including the effects of thermal load, is derived with Hamilton's principle, and then solved analytically by employing the Navier method. For the free vibration responses of the nanoplate, the effects of nonlocal and strain gradient elasticities, temperature rise, porosity volume fraction and its distribution are analyzed.

Static behavior of elastically supported transversely inhomogeneous porous functionally graded plate with different thickness variations under a variety of external loadings

The static behavior of a porous functionally graded material plate (FGMP) with variable thickness placed on two parametric elastic foundations exposed to various boundary conditions is investigated in this study. Thickness variation in the plate is assumed to vary in uni-direction/bi-direction with linear and parabolic variations. The properties of the constituent of FGMs are expected to change in the direction of thickness following the power law. The plate is subjected to three types of external loadings: uniformly distributed load (UDL), linearly increasing load (LIL), and linearly increasing decreasing load (LIDL). To explore the static behavior, numerical parameters (NP) linked with the bending and normal stresses of the plate have been determined. Classical plate theory is used to derive the governing equation using the energy principle. The transverse displacement functions are indigenously developed in the form of simple algebraic polynomials (using Pascal’s triangle) to handle any set of mixed- boundary conditions. The Rayleigh–Ritz method along with the algebraic polynomial is employed in the numerical simulation for getting NP. This method is straightforward, precise, and computationally efficient as it can handle any set of boundary conditions and the solution converges with very few iterations. Following the convergence and validation analyses, new findings are presented. The influence of aspect ratios, power-law exponents, porosity volume fraction, taper ratios, and the Winkler and Pasternak modulus on the NP of the plate has been thoroughly examined. The effect of various types of external loading and boundary conditions on deformed shapes and co-ordinate of maximum deflection of elastically supported porous FGMP with different thickness variations have also been reported. One of the important findings is that the effect of homogeneous porosity distribution on NP is more pronounced than in situations with non-homogeneous distributions. Also, the change in thickness of the plate and the distribution of various types of porosity has a substantial effect on the deformed shape of the plate. One of the interesting observations of this study is that the deformation in the plate is more significant in the case of bi-linear thickness variation compared to the uni-linear case. The results reported in this article are accurate enough to consider for further research and experimentation.

Use of Nano-Encapsulated phase change material mixed with water for natural convection cooling in combination with nickel foam

This study investigated the potential benefits of using free convection mechanisms to cool parts, as opposed to forced convection mechanisms that require energy to transfer heat and mass. The research team cooled a hot plate, which had a uniform heat flux, by utilizing the free convection flow inside a square cavity. They also installed a partial nickel porous media with different porosities on the hot plate and injected nano-encapsulated phase change material (NEPCM) particles into water to form a cooling fluid mixture. For the NEPCM particles, the researchers selected n-docosane with a melting temperature of 317.65 K for the core and polyurethane for the shell. The researchers used computational fluid dynamics (CFD) to simulate the cooling process with varying parameters, including porosity, deflection angles, and NEPCM volume fraction. The results showed that the cooling performance of nickel foam was significantly better than that of NEPCM. For example, when the porosity of the nickel foam decreased from 0.98 to 0.93, the average Nusselt number increased by 142 %, indicating a considerable improvement in cooling efficiency. In comparison, increasing the NEPCM volume fraction from 0 to 6 % only resulted in a modest 5.6 % increase in the average Nusselt number.

Numerical Investigation on the Impact of Linear Variation of Positive Electrode Porosity upon the Performance of Lithium-Ion Batteries

The diffusion process of lithium-ions in the positive electrode solid phase as within the liquid phase is one of the pivotal factors in determining the battery performance. The effective conductivity and diffusion coefficient of the solid and liquid phases can be regulated by changing the distribution of the volume fraction of active material and porosity on the positive electrode. These crucial parameters can affect the transfer of lithium-ions in the solid and liquid phases and ultimately affect the battery’s performance. In this paper, a pseudo-three-dimensional (P3D) electrochemical-thermal-mechanical (ETM) coupling model is employed to study the non-uniform porosity of the positive electrode, especially the effect of porosity variation on the battery temperature and stress during the discharge process. Through numerical results, we find that reasonable porosity distribution can make the electrode lithiation more uniform and reduce the battery surface temperature by decreasing ionic ohmic heat. In addition, we display the stress distribution on the electrode and inside the active particles after adopting the linear porosity. The results are helpful for an in-depth understanding of the effect of the non-uniform porosity of the positive electrode on the lithium transport mechanism, the stress mechanism, and the thermal mechanism during the operation of lithium-ion batteries (LIBs).

Development of Three-Dimensional (3D) Biodegradable Polyglycolic Acid Fiber (PGA) Preforms for Scaffold Applications: Experimental Patterning and Fiber Volume Fraction-Porosity Modeling Study.

Three-dimensional (3D) biodegradable polyglycolic acid fiber (PGA) preforms were developed as temporary scaffolds for three-dimensional tissue regeneration applications. Three-dimensional biodegradable polyglycolic acid fiber (PGA) preforms including various degrees of interlaced structures called 3D plain, semi-interlaced, and orthogonal woven preforms were designed. Analytical relations and finite element model-based software (TexGen) on fiber volume fraction and porosity fraction were proposed to predict scaffolds' stiffness and strength properties considering micromechanics relations. It was revealed that yarn-to-yarn space, density, and angles of all 3D PGA fiber preforms were heterogeneous and demonstrated direction-dependent features (anisotropy). Total fiber volume fractions (Vfp) and porosity fraction (Vtpr) predicted by analytic and numerical modelling of all 3D scaffolds showed some deviations compared to the measured values. This was because yarn cross-sections in the scaffolds were changed from ideal circular yarn (fiber TOW) geometry to high-order ellipse (lenticular) due to inter-fiber pressure generated under a tensile-based macrostress environment during preform formation. Z-yarn modulus (Ez-yarn) and strength (σz-yarn) were probably critical values due to strong stiffness and strength in the through-the-thickness direction where hydrogel modulus and strengths were negligibly small. Morphology of the scaffold showed that PGA fiber sets in the preform were locally distorted, and they appeared as inconsistent and inhomogeneous continuous fiber forms. Additionally, various porosity shapes in the preform based on the virtual model featured complex shapes from nearly trapezoidal beams to partial or concave rectangular beams and ellipsoid rectangular cylinders. It was concluded that 3D polyglycolic acid fiber preforms could be a temporary supportive substrate for 3D tissue regeneration because cells in the scaffold's thickness can grow via through-the-thickness fiber (z-yarn), including various possible mechanobiology mechanisms.

A C0-HSDT free vibration of magneto-electro-elastic functionally graded porous plates using a moving Kriging meshfree method

This research examines the natural vibration analysis of magneto-electro-elastic functionally graded porous (MEE-FGP) plates. The study employs a moving Kriging (MK) meshfree method to analyze the MEE-FGP plates composed of piezoelectric and piezomagnetic materials with both even and uneven distributions of porosity. The electric and magnetic potentials in the three-dimension are assumed to follow a combination of cosine and linear variations in the thickness direction to satisfy the Maxwell equations in the two-dimension. The displacement field, electric potential and magnetic potential are approximated by the MK interpolation shape function, which satisfies the Kronecker's delta property. This property allows to impose directly essential boundary conditions as those in the finite element method. The governing equilibrium equations are derived using a C0-type higher-order shear deformation plate theory (C0-HSDT) in conjunction with the virtual work principle and then solved using the MK meshfree method. Various geometries are performed to determine the natural frequency of MEE-FGP plates. The impact of the porosity distribution, porosity volume fraction, volume fraction index, initial external electric voltage, initial magnetic potential and geometry on the natural frequency of the MEE-FGP plates is fully investigated. Numerical results provide an effective approach to analyze and calculate the natural vibration of MEE-FGP plates.

The relationship between electric processing condition and microstructure in the solidification of multicomponent oxides

Systematic characterization for the relationship between the electropulse processing conditions and microstructure has been carried out in the present work. It is found that electropulse can refine porosity and alter grain morphology considerably. A processing with optimum electropulsing parameters can reduce over 75% volume fraction of porosity and more than 70% average pore diameter in comparison with that of reference sample without electric treatment. Electric current treatment promotes the growth of dendrites with smaller thickness of primary arms dendrite and prevents the liquid entrapping between the growing solid grains. The former is caused by the effect of electricity-enhanced kinetic mobility on the radius of curvature at the tip of dendrite. The latter is attributed to the effects of electric thermodynamics on the microstructural formation such as the enhanced connectivity of conductive phase. The microstructures obtained by electropulsing treatment are favourable for heat conduction, structural strength and crack prohibition. However, the excess pulse frequency and pulse width can generate unwanted heat to counteract electric effect. The research reveals the relationship between electric processing conditions and microstructure in a perfectly controversial solidification condition in oxide materials to that of the metals and alloys. The results confirm from the opposite side the validity of the pulsated solidification.

Bending-bending coupled static analysis of functionally graded and porous pretwisted cantilever beams using initial values method

In this study, the bending-bending coupled static behavior of functionally graded and porous pretwisted cantilever Timoshenko beams is reported. Symmetric power-law distribution is employed as the material profile and it is assumed that porosity can disperse over the cross-section in two forms namely, even and uneven distributions. Two different yet equivalent forms of governing equations are obtained by formulating the problem in the fixed and curvilinear coordinate systems, respectively. The initial values method is adopted as the solution methodology. While the fundamental matrix is computed numerically by using the multiplicative integral of Volterra to obtain the solution in the fixed coordinate formulation, the matrix exponential which allows for obtaining exact expressions is utilized in the curvilinear coordinate formulation. Exact analytical deflection expressions are presented for space-fixed vertical tip force and body-fixed uniform distributed force cases. It is shown that both formulation approaches yield consistent results with each other and those obtained from the finite element analyses. In addition, several parametric studies that investigate the effects of the volume fraction index, porosity coefficient, and porosity distribution on the tip deflections are presented.

Study of effective elastic properties of heterogeneous materials with an artificial neural network model

This paper is devoted to the estimation of macroscopic elastic properties of composites containing inclusions and pores. Some representative analytical homogenization models are first recalled and their weaknesses are highlighted by comparisons with the reference numerical results obtained from direct simulations by a Fast Fourier Transform (FFT) method. A large data set is then constructed also based on numerical results obtained from FFT simulations for different types of micro-structures and for a large range of elastic properties of constituents. An artificial neural network (ANN)-based model containing two hidden layers is constructed and trained by using this data set. Different types of validation tests of the ANN model are presented. It is found that the ANN-based model can estimate the macroscopic elastic properties of strongly heterogeneous materials with a very good accuracy, for different types of micro-structures and a large range of porosity and inclusion volume fraction.

Numerical Computation of Ag/Al2O3 Nanofluid over a Riga Plate with Heat Sink/Source and Non-Fourier Heat Flux Model

The main goal of the current research is to investigate the numerical computation of Ag/Al2O3 nanofluid over a Riga plate with injection/suction. The energy equation is formulated using the Cattaneo–Christov heat flux, non-linear thermal radiation, and heat sink/source. The leading equations are non-dimensionalized by employing the suitable transformations, and the numerical results are achieved by using the MATLAB bvp4c technique. The fluctuations of fluid flow and heat transfer on porosity, Forchheimer number, radiation, suction/injection, velocity slip, and nanoparticle volume fraction are investigated. Furthermore, the local skin friction coefficient (SFC), and local Nusselt number (LNN) are also addressed. Compared to previously reported studies, our computational results exactly coincided with the outcomes of the previous reports. We noticed that the Forchheimer number, suction/injection, slip, and nanoparticle volume fraction factors slow the velocity profile. We also noted that with improving rates of thermal radiation and convective heating, the heat transfer gradient decreases. The 40% presence of the Hartmann number leads to improved drag force by 14% and heat transfer gradient by 0.5%. The 20% presence of nanoparticle volume fraction leads to a decrement in heat transfer gradient for 21% of Ag nanoparticles and 18% of Al2O3 nanoparticles.

Effect of Manufacture-Induced Interfaces on the Tensile Properties of 3D Printed Polyamide and Short Carbon Fibre-Reinforced Polyamide Composites.

This study aims to elucidate the structure-property-process relationship of 3D printed polyamide and short carbon fibre-reinforced polyamide composites. The macroscopic properties (tensile modulus) of the 3D printed samples are quantitatively correlated to the printing process-induced intrinsic microstructure with multiple interfaces. The samples were printed with different layer thicknesses (0.1, 0.125 and 0.2 mm) to obtain the varied number of interface densities (number of interfaces per unit sample thickness). The result shows that the printed short carbon fibre-reinforced polyamide composites had inferior partially bonded interfaces compared to the printed polyamide, and consequently exhibited interface-dependent elastic performance. The tensile modulus of 3 mm thick composites decreased up to 18% as a function of interface density, whilst the other influencing aspects including porosity, crystallinity and fibre volume fraction (9%) were the same. Injection moulding was also employed to fabricate samples without induced interfaces, and their tensile properties were used as a benchmark. Predictions based on the shear-lag model were in close agreement (<5%) with the experimental data for the injection-moulded composites, whereas the tensile modulus of the printed composites was up to 38% lower than the predicted modulus due to the partial bonded interfaces.

진공백법으로 제조된 아라미드/에폭시 복합체의 개발 및 물리적 특성 분석

The manufacturing process of composite materials is crucial in determining their final quality and mechanical and physical properties. Although manufacturing defects affecting mechanical properties cannot be entirely eliminated, some process parameters can be improved to reduce them, and solutions without increasing manufacturing costs are sought. Currently, research on aramid fibers and epoxy resin is booming; thus, this study aims to apply the vacuum bag process with epoxy matrix and aramid fiber reinforcement, focusing on the manufacturing process parameters. Herein, a procedure for the hand lay-up of aramid impregnated with resin and the vacuum bag method for a composite laminate is described. Some variations and improvements in the vacuum bag technique were applied, improving the breathable layers in the mold to enhance the extraction of gases and promote a homogenous pressure distribution. ASTM procedures were performed to obtain the density and constituent content of the composite material, resulting in a fiber volume fraction of 0.606, a resin volume fraction of 0.294, and a porosity volume fraction of 0.098.

Limit angular speed analysis of porous functionally graded rotating disk under thermo-mechanical loading

PurposeIn this work, the effect of porosity volume fraction, porosity types, material grading index, variable disk profiles and aspect ratio on disk performance was studied by performing limit elastic speed analysis of functionally graded porous rotating disks (PFGM) under thermo-mechanical loading.Design/methodology/approachThe composition change was varied by employing the power law function. The thermo-mechanical properties of PFGM such as Young's modulus and yield strength were estimated using modified rule of mixture, for density and coefficient of thermal expansion rule of mixture was used. The even and uneven distribution of porosity in a disk was taken as uniform, symmetrical, inner maximum and outer maximum. The problem was then solved with the help of the variational principle and Galerkin's error minimization theory.FindingsThe research reveals that the grading parameter, disk geometry and porosity distribution have a significant impact on the limit elastic speed in comparison to the aspect ratio.Practical implicationsThe study determines a range of operable speeds for porous and non-porous disk profiles that the industry can utilize to estimate structural performance.Originality/valueA finite element investigation was conducted to validate the findings of the present study. Limit elastic analysis of porous FG disks under thermo-mechanical loading has not been studied before.

Dynamic Instability of Hybrid Functionally Graded Porous Plate Under Arbitrary Pulsating Loads

In this paper, the dynamic instability of hybrid functionally graded porous (FGP) plates under arbitrary periodic load is studied. The FGP plate composes of ceramic, functionally graded material (FGM) and metal. Four FGM core layers discussed include a non-pore perfect FGM layer and three imperfect FGM layers with different porosity distribution patterns. FGM layer properties are described by constituent volume fraction, porosity volume fraction and porosity distribution pattern. The Galerkin method and eigenfunctions transforms are used to establish the Mathieu-type governing equations. The influences of the load parameter, layer thickness ratio, constituent volume fraction, porosity distribution pattern and porosity volume fraction on the dynamic instability of hybrid FGP plates are investigated and discussed.

Estimation of Mineral Accessible Surface Area from Mineral Abundance and Clay Content

The mineral reactive surface area is often quantified through a wide range of approaches (e.g., Brunauer–Emmett–Teller adsorption, geometry approximation, and imaging techniques). As such, values vary 1–5 orders of magnitude which can result in large discrepancies when used in reactive transport models to simulate geochemical reaction rates. Simulations carried out using mineral accessible surface areas (ASAs) determined from a coupled 2D and 3D imaging approach have shown better match with reaction rates measured in core-flood experiments. However, such image processing requires large amounts of time and resources. In this work, the possibility of estimating mineral ASAs from easily measured properties like mineral abundance and porosity is explored. Six sandstone samples of varying compositions were studied along with data from three additional samples from the previous literature. Mineral ASAs were quantified using a combined 2D scanning electron microscopy and 3D X-ray nano-computed tomography imaging approach. Sample properties like mineral accessibility, mineral ASAs, connected porosity, and clay content were compared to explore potential correlations between properties. Overall, it was observed that mineral accessibility can be predicted where feldspar mineral accessibility generally increases with increasing abundance and quartz accessibility decreases with increasing clay content. Mineral ASAs vary between samples, depending on the relative abundance of minerals and overall pore connectivity. While the ASA of quartz decreases with abundance, albite and carbonate mineral ASAs increase with abundance. Quantitative observations, including predictive relationships for ASAs from porosity and mineral volume fraction, are developed. Estimations of ASAs and mineral accessibility from more easily quantifiable properties can largely reduce the required extent of image analysis.

Analysis of buoyancy assisting and opposing flows of colloidal mixture of titanium oxide, silver, and aluminium oxide nanoparticles with water due to exponentially stretchable surface

Energy is essential for a nation's economic growth. Energy is recognized in contemporary society as being crucial to the development of quality of life and sustainability. The environment transforms/absorbs heat and sunlight in a variety of ways. Some of these transitions lead to the flow of renewable energy sources like wind and biomass. Solar energy has become one of the promising alternative energy sources in the future because to the improvements made to enhance its performance. In this context, the impact of solar radiation on modified nanofluid flowover an exponential stretching sheet is examined. Using the proper similarity transformations, the governing equations for the flow assumptions are reduced to ordinary differential equations. The numerical simulation of these simplified equations is then performed using the Runge-Kutta Fehlberg method and the shooting methodology. With the aid of graphs and tables, the effects of numerous parameters on the involved fields are described. Results reveal that the modified nano liquid shows increased heat transport for opposing flow situation than the assisting flow situation for incremented values of porosity parameter and volume fraction. The modified nanoliquid shows increased heat transport for opposing flow situation with respect to augmented values of radiation parameter.

Numerical Modeling Based on Finite Element Analysis of 3D-Printed Wood-Polylactic Acid Composites: A Comparison with Experimental Data

Wood-polymer composites are increasingly produced through fused deposition modeling (FDM)—an additive manufacturing technique. The versatility of this technology has attracted several industries to print complex shapes and structures. This underscores the importance of studying the mechanical properties of the FDM parts, specifically, their elastic properties. A numerical homogenization methodology is introduced in the present study, focusing on the fundamental aspect of the elastic properties. Investigations were carried out on the influence of various parameters like wood volume fraction, aspect ratio, and internal porosity. The numerical results were validated using analytical models and experimental data. The comparison showed a satisfactory agreement with experimental data, where the relative error did not exceed 10%, leading to a strong conclusion about the validity and effectiveness of the proposed approach.