Material Properties Of Layers Research Articles

Enhancing the photovoltaic performance of Cd-free Cu2ZnSnS4 heterojunction solar cells using SnS HTL and TiO2 ETL

Cu2ZnSnS4 chalcogenide semiconductor is a very promising absorber material for solar cells and no longer fulfilled its realistic goals due to the possible challenge of defect-free fabrication, non-optimized buffer layer alignment and device configuration. In this article, we proposed a new planner structure defined as (SnS/CZTS/TiO2/ITO) using Ni and Al as a back and front contact materials, respectively, and simulated its photovoltaic (PV) performance using SCAPS-1D. In the simulation, defect densities were added to each layer and the interface between the buffer layer and the absorber layer. This work demonstrated the promising role of SnS HTL and TiO2 ETL in reducing the Voc deficit of CZTS-based solar cells by forming more favourable band alignment with the absorber layer, reducing non-radiative recombination at the interfaces. In response to changes in the material properties of different layers (such as thickness, carrier concentration, defect density), working temperature, and back contact metal work function, the PV performance of the new architecture for CZTS solar cells was investigated and optimized. The study of PV performance optimization revealed that a relatively thicker absorber layer with low carrier concentration showed better PV performances, while ETL and HTL with a thinner and higher carrier concentration are required to enhance PV performances. Power conversion efficiency of >30%, Voc of >1.09 V, Jsc of >32 mA/cm2 and FF of >87% was predicted for CZTS solar cells with the new architecture. The findings of this study suggest that SnS and TiO2 are expected to become HTL and ETL, respectively, for fabricating low cost, high efficiency, and Cd-free CZTS-based heterojunction solar cell.

Dynamic responses analysis of P and S-FGM sandwich cylindrical shell panels using a new layerwise method

This research work presents a comparison of the dynamic response of the functionally graded sandwich cylindrical shell panels (FGSCS) using a new layerwise method. The layerwise method developed assumes a first-order shear deformation theory (FSDT) for top and bottom facesheets and a third-order shear deformation theory for the core. The strain-displacement relation for FGSCS panels is obtained using Sander's first approximation. Two different sandwich configurations are considered, one having a pure metallic core with top and bottom facesheets made of functionally graded material (FGM) and the other one having an FGM core with top and bottom facesheets made of pure ceramic and pure metal, respectively. Material properties of the FGM layers for the two configurations are varied along the thickness direction according to the power-law (P-FGM) and the sigmoid models (S-FGM) respectively. The newly developed layerwise finite element model in conjunction with Hamilton's principle is employed to obtain the governing differential equation. Subsequently, the Newmark-Beta time integration scheme is used to obtain the dynamic response of P and S functionally graded sandwich cylindrical shell (P and S-FGSCS) panels for two configurations. The results obtained are first compared with the exact analytical results available in the literature. Numerical results are presented to investigate the effect of volume fraction index, loading conditions, core-to-facesheet thickness ratio, curvature ratio and boundary conditions on the transient response of P and S-FGSCS panels. The analysis reveals by selecting optimum parameters and gradation model, the amplitude and frequency of dynamic response of P and S-FGSCS panels can be controlled substantially.

Mechanics of adhesives under annular confinement: internal pressure, force, and interfacial area.

Closed annular adhesive interfaces are commonly found in nature as well as in many existing and developing technologies. Such contacts provide enhanced control of interfacial history by prescribing whether interfacial separation occurs at the outer or inner edge, and whether internal pressure affects the required force for separation. To facilitate the development of technologies involving annular contacts, we have experimentally measured the relationship between applied displacement, resulting force and internal pressure, and annular interface dimensions for the contact between a rigid annular probe and an adhesive layer with finite thickness. Experiments were validated by finite element analysis models, which were used to develop semi-empirical analytical relationships for the changes in contact compliance as a function of material properties and geometric constraints. Additionally, the change in internal pressure was modeled as a function of annular contact dimensions and adhesive layer material properties. This model predicts the critical volume where internal pressure changes alters critical force for separating an annular contact interface. The results discussed here provide a foundation for new experimental protocols for characterizing soft materials, including pressure-sensitive adhesives, as well as guidelines for designing annular interfacial materials with controlled separation histories.

Predicted responses of fatigue cracking and rutting on Roller Compacted Concrete base composite pavements

This study evaluated the effects of pavement design variables (type and thickness of asphalt concrete layer, base layer material properties, sub-base layer, and traffic volume) on fatigue cracking and rutting resistance of asphalt pavements using Roller Compacted Concrete (RCC) with Recycled Concrete Aggregate (RCA) and employing it as a base layer. The RCC mixtures were developed by partially replacing natural coarse aggregate with RCA in ratios of 0%, 5%, 15%, and 30%. The 25 Design of Experiments (DoE) was adopted as a screening experiment to identify the variables of pavement design that were vital to reducing the fatigue cracking and rutting on pavement sections. It was observed that the surface thickness, type of RCC-base, and volume of traffic were the most important variables to reduce damages. It was performed a 33 DoE with these variables to identify the best combination on the design of RCC-base pavements. It is evident from Response Surface Methodology that 10 cm surface thickness is recommended for preventing over 30% of fatigue cracking for RCC-base composed with RCC mixed with RCA ratios ranging from 10% to 30%. Rutting isn’t the significant damage on an RCC-base composite pavements. The RCC mixed with RCA could be considered as a good material for the base layer submitted to the high traffic volume of vehicles.

Three-dimensional free vibration analysis of rotating sandwich functionally graded truncated conical shells under various boundary conditions

In this work, the authors develop a Reissner’s mixed variational theorem (RMVT)-based weak formulation for the three-dimensional (3 D) free vibration analysis of sandwich functionally graded (FG) truncated conical shells under various boundary conditions rotating with a constant angular velocity with respect to the central axis of the shells. The material properties of the FG layers constituting the truncated conical shell are assumed to obey a power-law distribution of the volume fractions of the constituents through their thickness direction, for which the effective material properties are estimated using the rule of mixtures. Based on the weak formulation, a semi-analytical finite annular prism (FAP) method is developed for the current issue, where the effects of the initial hoop stress due to rotation and the centrifugal and Coriolis accelerations are considered. Implementation of the current FAP method indicates that its solutions converge rapidly, and the convergent solutions closely agree with accurate solutions available in the literature. The obtained 3 D frequency parameter solutions for rotating and non-rotating sandwich FG truncated conical shells can provide a standard by which to assess those obtained using assorted two-dimensional classical, advanced, and refined shell theories.

A Comparison of Nonlinear Bending and Vibration of Hybrid Metal/CNTRC Laminated Beams with Positive and Negative Poisson’s Ratios

Carbon nanotube reinforced composite (CNTRC) is one of the novel classes of advanced composite materials. This paper investigates the nonlinear bending and nonlinear vibration responses of hybrid laminated beams made of CNTRC layers bonded with metal layers on the top and bottom surfaces. We proposed a hybrid metal/CNTRC laminated beam for which out-of-plane Poisson’s ratio is negative. The effective material properties of CNTRC layers are graded in a piece-wise pattern across the thickness of the beam. The material properties of both CNTRC layer and metal layer are temperature dependent. The beams are rested on an elastic foundation and are located in thermal environments. Reddy’s higher-order beam model is used to establish the motion equations of the hybrid metal/CNTRC laminated beam. The motion equations include the von Kármán geometric nonlinearity, the thermal effects and the beam-foundation interaction. By employing a two-step perturbation approach, the bending and nonlinear vibration solutions are obtained. A comparison of nonlinear responses of hybrid metal/CNTRCl laminated beams with positive and negative Poisson’s ratios (NPRs) under different thermal environmental conditions is carried out and discussed in detail.

Influence of Al2O3, SiC and B4C covalent multilayer PVD coating on surface properties of HSS rod

Abstract The physical vapour deposition (PVD) coating technology is realized as the best advance coating methods which improves many multifunctional properties in the tool and also supports metastability and allows multilayer coating arrangements. This paper investigates the effect of Al2O3, SiC and B4C covalent multilayer PVD coating on wear, micro hardness, corrosion and friction properties of HSS rod. A structural design for different material layer properties were defined and coated. Aluminum oxide (Al2O3), Silicon carbide (SiC) and Boron carbide (B4C) particles were coated over the HSS rod up to 1.9 μm as an intermediate layers using layer formation methods. The wear rate, friction loss and stress developed were tested and compared between PVD coated and uncoated HSS material under different coating layer thickness and tested upon a machined stainless steel disc. Scanning electron microscope (SEM) test was conducted on the sample to study the influence of PVD process on the even dispersion of the coating particles and layer formation characteristics. The results reveal that the wear resistance, microhardness, compressive and thermal stresses were improved by PVD coating of Al2O3, SiC and B4C over HSS rod from 1.1 to 1.9 μm.

Free Vibration Analysis of Sandwich Beams with Functionally-Graded-Cores by Complementary Functions Method

A plane vibration study of a sandwich thermal protection system insulation panel with a functionally graded core is conducted. The panel is assumed to be under plane-stress conditions and subjected to simply supported boundary conditions. The two-dimensional elasticity formulations are used to derive the equations of motion for each layer. The effects of the in-plane normal stresses as well as the shear stress are taken into consideration for all layers. Material properties of layers may vary through the transverse coordinate resulting in a pair of second-order coupled variable- coefficient governing differential equations. The governing equations are reduced to an uncoupled fourth-order differential equation, which is solved by the complementary functions method (CFM). The novelty of the present study includes the vibration analysis of functionally graded core sandwich beam using plane elasticity and implementation of CFM as the solution procedure. The influences of face sheets and core materials and the grading model on the free vibration behavior are studied. The solutions are compared with results available in the literature and those obtained from finite element software (ANSYS) for a three-layered isotropic panel to display the accuracy and efficiency of the presented method. The mode shapes dominated by vertical and horizontal displacements are also depicted. The method that is applicable for both symmetric and unsymmetric beams is shown to be accurate and efficient in the analysis of sandwich panels with a core graded in the thickness direction.

Development of an equivalent shell finite element for modelling damped multi-layered composite structures

A new equivalent shell finite element (FE) for modelling damped multi-layered structures is presented in this study. The method used for developing the new FE for such structures is based on the idea that the strain energy of the equivalent single-layer FE must be equal to the sum of the strain energies of individual layers. The so-called energy coefficients are defined for this purpose for the extensional, bending and shear deformations of the composite structure. These coefficients are then determined and used as correction multipliers during stacking the elemental matrices of individual layers. Two approaches, based on second-order strain or stress distribution assumption through the composite thickness, are investigated for deriving the shear energy coefficients. The damping capability of the FE developed here originates from using complex Young’s modulus to define the material properties of individual layers. The resulting equivalent single-layer shell element with four nodes has six degrees-of-freedom per node. The accuracy, advantages and limitations of the composite FE developed in this work are investigated using experimental as well as theoretical results. In the light of the finding of these investigations, further enhancement in the formulation is made by also utilising a new shear correction factor for the individual layers in the equivalent shell element. Final results for free- and constrained-layered structures confirm that the equivalent shell FE developed here can be used effectively for the prediction of the modal properties of damped multi-layered structures.

Prediction and Measurement of the Damping Ratios of Laminated Polymer Composite Plates.

Laminated composites materials are mostly used in dynamically loaded structures. The design of these structures with finite element packages is focused on vibrations, elastic deformations and failure control. Damping is often neglected because of its assumed secondary importance and also because of dearth of information on relevant material properties. This trend is prone to change as it is now realised that damping plays an increasingly important role in vibration comfort, noise radiation and crash simulations. This paper shows in a first step how to identify the orthotropic elastic and damping properties of single layer fibre-reinforced composite material sheets using a new extended version of the Resonalyser procedure. The procedure is based on the elastic-viscoelastic correspondence principle and uses a mixed numerical experimental method. In a subsequent step, the complex laminate stiffness values are computed using the identified single layer material properties. To validate this approach, the modal damping ratios of arbitrary laminated plates of different materials at several resonance frequencies are predicted and experimentally verified.

Insights of Hysteresis Behaviors in Perovskite Solar Cells from a Mixed Drift-Diffusion Model Coupled with Recombination

Hysteresis in perovskite solar cells is a notorious issue limiting its development in stability, reproducibility and efficiency. Ions’ migration coupled with charges’ recombination are indispensable factors to generate the hysteretic curves on the basis of experimental and theoretical calculation studies, however, the underlying physical characteristics are rarely clarified. Here, a mixed electronic-ionic drift-diffusion model combined with bulk and interfacial recombination is investigated. Positive and negative ion species could drift to and accumulate at interfaces between the perovskite/transport layers, influencing internal electric potential profiles and delaying the charges’ ejection to the transport layers. The charges might recombine spontaneously or trap-assisted, reducing the total amount of electrons and holes collected in the external circuit, leading to a diminished photocurrent. Moreover, our calculations indicate that an appropriate measurement protocol is really essential to evaluate the device performance precisely and to suppress J–V hysteresis. Meanwhile, a negligible hysteretic loop could be obtained by balancing the material properties of the transport layers and restraining the ions mobility in the perovskite layer.

Novel Framework for the Quantification of Pavement Damages in the Overload Corridors

Recent traffic trends and permit issuance show significant mobility demands in the energy sectors across the nation. The increase in the axle loads and frequency of operations of over-weight (OW) trucks resulted in severe damage to transportation infrastructures. Traditionally, the damage imparted by OW vehicles has been quantified by means of the equivalent axle load factors (EALFs) concept. However, because of the nature of assumptions in the development of damage equivalency factors, the field distresses substantially deviate from the prediction models. Therefore, this study aimed to bridge this gap by developing a mechanistic framework to determine damage equivalency factors tailored toward the specific characteristics of OW vehicles operating in the OW corridors, while considering the environmental conditions and the unique features of transportation facilities in the network. To achieve this objective, initially, the authors devised a plan to collect traffic information using portable weigh-in-motion devices at two intervals for 10 representative sites in the energy corridors of Eagle Ford Shale region. Subsequently, a series of nondestructive tests were conducted in the field to determine the material properties of the pavement layers for further numerical simulations. This information was further incorporated into a 3D finite element system to calculate critical input parameters in the modified damage factor models. The proposed mechanistic approach confirmed that the modified damage factors were substantially higher compared with traditional industry-standard values. Further investigation of environmental factors and pavement profiles in this study underscored the significance of these components for accurate assessment of the damage equivalency factors.

Bending of Functionally Graded Sandwich Nanoplates Resting on Pasternak Foundation under Different Boundary Conditions

This article proposes a refined higher order nonlocal strain gradient theory for stresses and deflections of new model of functionally graded (FG) sandwich nanoplates resting on Pasternak elastic foundation. Material properties of the FG layers are supposed to vary continuously through-the-thickness according to a power function or a sigmoid function in terms of the volume fractions of the constituents. The face layers are made of FG material while the core layer is homogeneous and made of ceramic. In this study, an analytical approach is proposed using the higher-order shear deformation plate theory and nonlocal strain gradient theory with combination of various boundary conditions. Numerical outcomes are reported to display the impact of the material distribution, boundary conditions, elastic foundation parameters and the sandwich nanoplate geometry on the deflections and stresses of FG sandwich nanoplates. The exactness of this theory is determined by comparing it to other published outcomes.

Static Analysis of Functionally Graded Coated Plate on Elastic Foundation Based on Levy Method

Levy method for bending analysis of composite plate resting on a Winkler elastic foundation hypothesis is presented based on classical plate theory. Two models were considered for a composite coated plate. These two models were named conventional composite model and functionally graded coated model. The conventional composite model was consisting of a ceramic Homogeneous Coated (HC) layer and metal layer. The Functionally Graded Coated (FGC) model was consisting of Functionally Graded Material (FGM) as a composition of ceramic and metal on a metal layer. The material properties of FGM composite are assumed varying exponentially along the thickness direction. Also, the material properties of the nan-FGM layers are assumed homogeneous. Finally, the effect of the FGC layer, as well as, the elastic stiffness of the foundation is presented and compared with the results of the HC model.

Two-Dimensional Free Vibration Analysis of Axially Functionally Graded Beams Integrated with Piezoelectric Layers: An Piezoelasticity Approach

For the first time, a two-dimensional (2D) piezoelasticity-based analytical solution is developed for free vibration analysis of axially functionally graded (AFG) beams integrated with piezoelectric layers and subjected to arbitrary supported boundary conditions. The material properties of the elastic layers are considered to vary linearly along the axial ([Formula: see text]) direction of the beam. Modified Hamiltons principle is applied to derive the weak form of coupled governing equations in which, stresses, displacements and electric field variables acting as primary variables. Further, the extended Kantorovich method is employed to reduce the governing equation into sets of ordinary differential equations (ODEs) along the axial ([Formula: see text]) and thickness ([Formula: see text]) directions. The ODEs along the [Formula: see text]-direction have constant coefficients, where the ODEs along [Formula: see text]-direction have variable coefficients. These sets of ODEs are solved analytically, which ensures the same order of accuracy for all the variables by satisfying the boundary and continuity conditions in exact pointwise manner. New benchmark numerical results are presented for a single layer AFG beam and AFG beams integrated with piezoelectric layers. The influence of the axial gradation, aspect ratio and boundary conditions on the natural frequencies of the beam are also investigated. These numerical results can be used for assessing 1D beam theories and numerical techniques.

Free vibration of FG sandwich plates partially supported by elastic foundation using a quasi-3D finite element formulation

Free vibration of functionally graded (FG) sandwich plates partially supported by a Pasternak elastic foundation is studied. The plates consist of three layers, namely a pure ceramic hardcore and two functionally graded skin layers. The effective material properties of the skin layers are considered to vary in the plate thickness by a power gradation law, and they are estimated by Mori--Tanaka scheme. The quasi-3D shear deformation theory, which takes the thickness stretching effect into account, is adopted to formulate a finite element formulation for computing vibration characteristics. The accuracy of the derived formulation is confirmed through a comparison study. The numerical result reveals that the foundation supporting area plays an important role on the vibration behavior of the plates, and the effect of the layer thickness ratio on the frequencies is governed by the supporting area. A parametric study is carried out to highlight the effects of material distribution, layer thickness ratio, foundation stiffness and area of the foundation support on the frequencies and mode shapes of the plates. The influence of the side-to-thickness ratio on the frequencies of the plates is also examined and discussed.

Damped dynamic behavior of an advanced piezoelectric sandwich plate

In this paper, damped dynamic deflections of an advanced piezoelectric sandwich plate (APSP) subjected to thermo-electro-mechanical loads have been studied using a meshless method. In the considered APSP, two active piezoelectric layers are attached on to the faces of a passive advanced structure consisting of two thin graphene reinforced nanocomposite (GRNC) layers and a thick porous polymeric core. In GRNC layers, graphene content is assumed to be varied according to functional distribution profiles. Using modified Halpin-Tsai’ equations, temperature dependent material properties of nanocomposite layers have been determined. Reddy’s third order theory of plates (called TSDT) is utilized to obtain the coupled governing equations, and MLS shape functions are adopted in the meshless solution. The influences of graphene content, porosity, temperature, electro-mechanical loading and structural damping on dynamic deflection behavior have been investigated. The results reveal that adding graphene volume fraction from 3% to 7% significantly affects the damping ratio, settling time and dynamic response of APSPs. However, further addition of graphene content has little effect on those responses. Moreover, embedding more pores in the core layer remarkably changes the damped dynamic behavior of APSPs due to a significant reduction in structural weight and a slight decrease in structural stiffness.

Nonlinear Vibration of Temperature-Dependent FG-CNTRC Laminated Beams with Negative Poisson’s Ratio

Laminated beams made of nanocomposite materials have been used in many industrial sectors. This paper reports a study on the vibration behavior of laminated beams when experiencing the large amplitude vibration. The beams are made of perfectly bonded carbon nanotube-reinforced composite (CNTRC) layers. The novel constructions of CNTRC laminated beams with out-of-plane maximum negative Poisson’s ratio (NPR) are proposed. The volume fraction of CNT may change across the beam thickness which results in a piece-wise pattern. The material properties of the CNTRC layers are temperature-dependent and can be estimated by the extended rule of mixture model. The beams are considered to rest on a two-parameter elastic foundation and under differential thermal environmental conditions. The higher order shear deformation beam theory is applied to derive the motion equations of the nonlinear vibration of FG-CNTRC laminated beams. These equations include the influencing factors such as the geometrical nonlinearity in the von Kármán sense, the thermal effects and the beam–foundation interaction. The nonlinear vibration solutions can be obtained by employing a two-step perturbation approach. The nonlinear vibration characteristics of FG-CNTRC laminated beams under different sets of loading conditions and thermal environmental conditions are discussed in detail through a series of parametric studies. Numerical results show that the NPR has a significant effect on the large amplitude vibration characteristics of CNTRC laminated beams.

On vibration of functionally graded sandwich nanoplates in the thermal environment

This paper deals with the free vibration response of rectangular functionally graded material sandwich nanoplates with simply supported boundary conditions. The material properties of the FGM layers are temperature-dependent and supposed to be graded continuously along the thickness direction. A simple power-law distribution in terms of the volume fractions of the material constituents is employed to obtained the effective material properties. Eringen’s nonlocal elasticity model is incorporated in order to take into account the small size effects. Two types of functionally graded material sandwich nanoplates are considered: a sandwich with functionally graded material face layers and homogeneous core, and a sandwich with homogeneous face layers and functionally graded material core. The equations of motion of the functionally graded material sandwich nanoplates are derived by using the higher shear deformation theory and the Hamilton’s variational principle, and solved using the Navier’s solutions. Several numerical results indicate the influence of the power–law index, the nonlocal parameter, the geometrical parameters of the nanoplate, and the temperature variation on the free vibration response are presented.

Material properties of the skull layers of the primate parietal bone: A single-subject study.

The outer cortical table of the parietal bone has been commonly used as a calvarial bone graft site for the craniofacial reconstruction. However, little is known about how removing the outer table may affect the function and structure of the inner table, and how the knowledge of the biomechanics and material properties of cortical bones will help the calvarial graft to better integrate into the biological and mechanical functions of its surrounding native tissues. In this study, it was hypothesized that there were significant differences in both density and material properties between inner and outer cortical plates in cranial bones. Twelve cylindrical specimens, including inner-outer layers, of cortical parietal bone of a female baboon were collected. Cortical thicknesses and densities were measured, and elastic properties were assessed using an ultrasonic technique. Results demonstrated remarkable difference in both thickness (t = 8.248, p ≤0.05) and density (t = 4.926, p≤0.05) between inner and outer cortical paired samples. Orthotropic characteristics of the cortical plates were detected as well, these findings suggest that there are differences in biomechanical properties between two surfaces of cranial bones at both tissue and organ levels. How these differences are linked to the stress environments of the inner and outer cranial cortical layers awaits further studies. Further study will greatly enhance our ability to address questions derived from both morphological and craniofacial medicine fields about the development and biomechanics of craniofacial skeletons.