Layers Of Dissimilar Materials Research Articles

New analytical model for multi-layered composite plates with imperfect interfaces under thermomechanical loading

A new analytical model for thermoelastic responses of a multi-layered composite plate with imperfect interfaces is developed. The composite plate contains an arbitrary number of layers of dissimilar materials and is subjected to general mechanical loads (both distributed internally and applied on edges for each layer) and temperature changes, which can vary from layer to layer and along two in-plane directions. Each layer is regarded as a Kirchhoff plate, and each imperfect interface is described using a spring-layer interface model, which can capture discontinuities in the displacement and stress fields across the interface. Unlike existing models, the governing equations and boundary conditions are simultaneously derived for each layer by using a variational procedure based on the first and second laws of thermodynamics, which are then combined to obtain the global equilibrium equations and boundary conditions for the multi-layered composite plate. A general analytical solution is developed for a symmetrically loaded composite square plate with an arbitrary number of layers and imperfect interfaces by using a new approach that first determines the interfacial normal and shear stress components on one interface. Closed-form solutions for two- and three-layer composite square plates are obtained as examples by directly applying the general analytical solution. Numerical results for two-, three- and five-layer composite plates under different loading and boundary conditions predicted by the current model are provided, which compare well with those obtained from finite element simulations using COMSOL, thereby validating the newly developed analytical model.

Biomedical Device Surface Treatment by Laser-Driven Hydroxyapatite Penetration-Synthesis Technique for Gapless PEEK-to-Bone Integration.

Polyetheretherketone (PEEK), a bioinert polymer known for its mechanical properties similar to bone, is capable of averting stress shielding. Due to these attributes, it finds applications in diverse fields like orthopedics, encompassing cervical disc replacement for the neck and spine, along with dentistry and plastic surgery. However, due to insufficient bonding with bone, various methods such as hydroxyapatite (HA) coating on the surface are attempted. Nonetheless, the interface between the polymer and ceramic, two different materials, tended to delaminate after transplantation, posing challenges in preventing implant escape or dislodgement. This research delves into the laser-driven hydroxyapatite penetration-synthesis technique. Differing from conventional coating methods that bond layers of dissimilar materials like HA and PEEK, this technology focuses on synthesizing and infiltrating ionized HA within the PEEK substrate resulting in an interface-free HA-PEEK surface. Conversely, HA-PEEK with this technology applied achieves complete, gap-free direct bone-implant integration. Our research involved the analysis of various aspects. By means of these, we quantitatively assesed the enhanced bone bonding characteristics of HA-PEEK surfaces treated with this approach and offered and explanation for the mechanism responsible for direct bone integration.

Critical velocities of a three-layer composite tube incorporating the rotary inertia and material anisotropy

Critical velocities of a three-layer composite tube subjected to a uniform internal pressure moving at a constant velocity are obtained in closed-form expressions. A Love–Kirchhoff thin shell model including the rotary inertia and material anisotropy effects is used in the formulation. The composite tube is made of three perfectly bonded cylindrical layers of dissimilar materials, each of which can be orthotropic, transversely isotropic, cubic or isotropic. Closed-form formulas for the critical velocities are first derived for the general case by incorporating the effects of material anisotropy, rotary inertia and radial stress. Specific formulas are then obtained for composite tubes without the rotary inertia effect and/or the radial stress effect and with various types of material symmetry for each layer as special cases. It is also shown that the current model for three-layer tubes can be reduced to those for single- and two-layer tubes. To illustrate the newly derived formulas, an example is provided for a composite tube consisting of an isotropic inner layer, an orthotropic core, and an isotropic outer layer. All four critical velocities of the composite tube are computed using the new closed-form formulas. Three values of the lowest critical velocity of the three-layer composite tube are analytically obtained from three sets of the new formulas, which agree well with the value computationally determined by others.

Attaching organic fibers to mineral: The case of the avian eggshell

Bird eggs possess a mineralized eggshell with a soft underlying fibrous membrane. These dissimilar material layers successfully evolved a structural attachment to each other as a conserved avian reproduction strategy essential to avian embryonic development, growth, and hatching of the chick. To understand how organic membrane fibers attach to shell mineral (calcite), 3D multiscale imaging including X-ray and electron tomography coupled with deep learning-based feature segmentation was used to show how membrane fibers are organized and anchored into shell mineral. Whole fibers embed into mineral across the microscale, while fine mineral projections (granules/spikes) insert into fiber surfaces at the nanoscale, all of which provides considerable surface area and multiscale anchorage at the organic-inorganic interface between the fibrous membrane and the shell. Such a reciprocal anchorage system occurring at two different length scales between organic fibers and inorganic mineral provides a secure attachment mechanism for avian eggshell integrity across two dissimilar materials.

Critical velocities of a two-layer composite tube incorporating the effects of transverse shear, rotary inertia and material anisotropy

Critical velocities of a two-layer composite tube subjected to a uniform internal pressure moving at a constant velocity are analytically derived by using a first-order shear deformation shell theory incorporating the transverse shear, rotary inertia and material anisotropy. The composite tube consists of two perfectly bonded axisymmetric circular cylindrical layers of dissimilar materials, which can be orthotropic, transversely isotropic, cubic or isotropic. Closed-form expressions for four critical velocities are first derived for the general case by including the effects of transverse shear, rotary inertia, material orthotropy and radial stress. The formulas for composite tubes without the transverse shear, rotary inertia or radial stress effect and with simpler anisotropy are then obtained as special cases. In addition, it is shown that the model for a single-layer, homogeneous tube is included in the current model as a special case. To illustrate the newly derived closed-form formulas, a composite tube with an isotropic inner layer and an orthotropic outer layer is analyzed as an example. The numerical values of the lowest critical velocity of the two-layer composite tube predicted by the new formulas compare well with existing data.

Critical velocities of a two-layer composite tube under a moving internal pressure

Critical velocities of a two-layer composite tube under a uniform internal pressure moving at a constant velocity are analytically determined. The formulation is based on a Love–Kirchhoff thin shell theory that incorporates the rotary inertia and material anisotropy. The composite tube consists of two perfectly bonded axisymmetric circular cylindrical layers of dissimilar materials, which can be orthotropic, transversely isotropic, cubic or isotropic. Closed-form expressions for the critical velocities and radial displacement of the two-layer composite tube are first derived for the general case by including the effects of material anisotropy, rotary inertia and radial stress. The formulas for composite tubes without the rotary inertia effect and/or the radial stress effect and with various types of material symmetry for each layer are then obtained as special cases. In addition, it is shown that the model for single-layer, homogeneous tubes can be recovered from the current model as a special case. To illustrate the new model, a composite tube with an isotropic inner layer and an orthotropic outer layer is analyzed as an example. All four critical velocities of the composite tube are calculated using the newly derived closed-form formulas. Six values of the lowest critical velocity of the two-layer composite tube are computed using three sets of the new formulas, which compare fairly well with existing results.

Effects of lap configuration on mechanical properties and composition distribution of three-layer overlapped laser weldments on Al/Cu dissimilar materials

Battery cells are connected via bus-bars to meet performance requirements, such as power and capacity, and multiple layers of dissimilar materials functioning as anodes, cathodes, or bus-bars are overlapped and welded together. In laser welding, the formation of brittle intermetallic phases in the weld joint is inevitable and, in turn, deteriorates the mechanical properties. To obtain the desirable joint performance, appropriate welding parameters to avoid intermetallic phase formations and joint designs to release stress concentrations must be obtained. This study investigates the effects of lap configurations and process parameters on the tensile-shear load, T-peel load, and composition distribution when multi-layered joints of dissimilar materials are produced by laser welding. Two layers of 0.4 mm Al sheets were welded with a single 0.2 mm Cu sheet, which was emulated using electric vehicle battery interconnects. The results show that the penetration depth varied in accordance with the lap configuration even under the same heat input condition. The lap configuration and welding parameters influenced the composition distribution of the welds, as they altered the solidification rate, number of Cu/Al contact interfaces, and location of the high-density material. The failure load of the T-peel specimens was lower than that of the tensile-shear specimens except for the Cu − Al − Al lap configuration. The T-peel load of the Cu − Al − Al lap configuration was similar to that of the tensile-shear load. When the stress-concentrated joint was homogeneous, it was more robust.

Metal Oxide-Induced Instability and Its Mitigation in Halide Perovskite Solar Cells.

Halide perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology for sustainable energy solutions because of their impressive power conversion efficiency and a path to be manufactured by low-cost, high-throughput methods. To reach PSCs' full potential for practical implementation, it is crucial to solve the issues related to long-term operational stability. Given that PSCs consist of many layers of dissimilar materials which form multiple internal interfaces, it is prudent to examine whether there exist interfacial interactions, most importantly between transport layers and perovskite absorbers, that can trigger instability and affect device performance. In this Perspective, we bring to the attention of the PSC research community the lesser-known interfacial degradation of halide perovskites promoted by contact with metal oxide transport layers and highlight the deleterious effects on the PSCs' performance and stability. We also discuss various mitigation strategies that have shown promise for achieving high-performing and stable PSCs.

Interface Quality Indices of Al–10Si–Mg Aluminum Alloy and Cr18–Ni10–Ti Stainless-Steel Bimetal Fabricated via Selective Laser Melting

Bimetallic materials are important in many industries (aerospace, medicine, etc.) since they allow the creation of constructions that combine specific functional properties, for example, low density (aluminum alloy) and high corrosion resistance (stainless steel), due to layering fabrication of the bimetallic joint. On the other hand, the difference in thermophysical properties of the dissimilar material layers leads to residual stresses, which cause deformation and destruction of such a bimetallic joint produced via the methods of surfacing or additive technologies. This article discusses the methods based on the gray relational analysis and generalized desirability function for the quality assessment of Al–10Si–Mg aluminum alloy and Cr18–Ni10–Ti stainless-steel bimetal fabricated via selective laser melting (SLM). There are four main parameters (quality indices) of the quality generalized assessment, which determine the degree of Al penetration into the steel substrate and Fe into the deposited layer, the difference in microhardness values on both sides of the interface boundary, and the resistance to mechanical destruction of the bimetallic joint. According to the results obtained, the best set of quality indices corresponds to the SLM technological modes with an energy density of 105 and 147 J/mm3. The greatest functionality of the bimetals is determined by the quality index associated with its strength. Therefore, methods of gray relational analysis and desirability function make it possible to form a generalized assessment for the bimetallic joint quality and, consequently, to select the best technological mode.

Application of a sound-conducting polymer foil for calibration of hydrophones by optical interferometry

Modern calibration of hydrophones at megahertz frequencies is based on the method of optical interferometry, in which the vibrational velocity of an acoustic wave is measured using a thin sound-transparent polymer foil (membrane), metallized on one side to improve light reflection and installed in an ultrasonic field, followed by its replacement with a hydrophone to be calibrated. The main problem of implementing this calibration method is to assess the adequacy of tracking vibrations of the metallized side of the foil to vibrational displacements of water particles under the action of a sound wave incident on the opposite side of the foil. On the basis of the simplified theory of acoustic plane waves passing through layers of dissimilar materials, methods for measuring the speed of sound in the applied foil and an algorithm for calculating the frequency dependence of the sound wave transmission coefficient (in terms of vibrational velocity) from water through the foil to water or air, introduced as a correction to the results of hydrophone calibration, were developed. The uncertainty of the introduction of this correction is estimated.

Finite element analysis and simulation study of CFRP/Ti stacks using ultrasonic additive manufacturing

The hybrid laminar composite stack of carbon fiber reinforced polymer (CFRP) and titanium (Ti) are widely used in several critical engineering applications, including aerospace and automobile sectors. The joining of CFRP and Ti through conventional methods has several limitations such as weight additional, material damage, and lower fatigue life. Ultrasonic additive manufacturing (UAM) is a solid-state manufacturing process capable of joining layers of dissimilar materials. Experimental studies have successfully demonstrated the welding of CFRP and Ti through UAM process. However, there is a lack of understanding of the exact bonding process and influence of process parameter on weld quality during UAM. The present study investigates the bonding process and the effects of critical parameters in the UAM process of CFRP and Ti layers using finite element analysis and simulation technique. The simulation study reveals that the CFRP/titanium stacks encounter interfacial cyclic shear stresses and shear strains. The study found that the vibrational amplitude and surface roughness of the substrates play a critical role in achieving a proper weld. The simulation results are validated using experimentation. The finding of this study can help advance the commercialization of UAM process for welding dissimilar materials and composites.

Effect of process parameters on the joint strength in ultrasonic welding of Cu and Ni foils

ABSTRACTManufacturing of battery packs for electric vehicles requires joining at different levels such as cell level, unit level, and module level, which include the joining of highly conductive and dissimilar layers of thin metal foils. Conventional welding techniques such as fusion welding, resistance spot welding, and laser beam welding are not appropriate for the joining of multiple layers of metal foils with a comparatively thicker tab because they face difficulties in producing large weld nuggets and generate weld defects such as brittle phases. Ultrasonic welding, a solid-state technique, has been found to be the most successful joining process for battery pack manufacturing. Several studies focused on the joining of two layers of dissimilar materials while very few have successfully characterized the welding performance of multi-layer ultrasonic metal welding. In this study, a set of weld attributes was introduced, and weld parameters have been optimized for sound quality joints using optical microscopy and nanoindentation based on those attributes. Different failure types were associated with weld quality based on microscopic images of fractured specimens. A correlation between weld parameters and weld attributes (i.e., bond density and post weld thickness) was developed to provide some insights into their interdependencies.

Finite element investigation on mode I crack tip characteristics in residually stressed glare

PurposeBehavior of mode I crack tip in fiber metal laminate (FML) differs from that in homogeneous or plain specimen made of metal used in the laminate due to the load transfer effect in the laminate caused by property mismatch between dissimilar material layers. The purpose of this paper is to present a finite element investigation on the characteristics of crack tip in monotonically loaded and residually stressed FML.Design/methodology/approachCrack tip characteristics are assessed by: the sizes of various zones that form at the tip; and crack tip energy release rates. The same are found by modeling two types of Glare laminates under monotonic tension with different crack orientations in SSY regime – Type I and Type II. Residual stresses are externally introduced in the models. Delaminations are modeled by cohesive elements. Crack tip zone sizes are measured from finite element solutions. Values of J integrals are computed over cyclic paths near the crack tips. Identically cracked and loaded plain aluminum alloy specimens are also modeled for comparison.FindingsThe sizes of crack tip zones in Glare laminates are found to be different than those in plain specimens. Process zone is observed to form at crack tip in Type I laminate whereas it does not develop in Type II laminate, the reverse being true in plain specimens. Values of J integrals near crack tips are also found to deviate from those in plain specimens, higher in Type I laminate due to crack tip stress amplification and lower in Type II laminate due to stress reduction. Crack orientation decides the amplification or shielding effect in the laminate.Research limitations/implicationsThere is scope for validating the numerical results reported in the paper by theoretical models.Practical implicationsThe method to quantify crack tip shielding and amplification is presented that shall be useful in checking the structural integrity/safety of the laminate during actual service conditions.Originality/valueShielding and amplification effects are explicitly described and illustrated in the paper. Suitability of using J integrals over paths crossing non-homogeneous and property mismatched material layers is tested. Use of cohesive zone method that is readily applicable in finite element procedures and is relatively simple, fast and reasonably accurate is also demonstrated.

Analysis of Weld Formation in Multilayer Ultrasonic Metal Welding Using High-Speed Images

One of the major challenges in manufacturing automotive lithium-ion batteries and battery packs is to achieve consistent weld quality in joining multiple layers of dissimilar materials. While most fusion welding processes face difficulties in such joining, ultrasonic welding stands out as the ideal method. However, inconsistency of weld quality still exists because of limited knowledge on the weld formation through the multiple interfaces. This study aims to establish real-time phenomenological observation on the multilayer ultrasonic welding process by analyzing the vibration behavior of metal layers. Such behavior is characterized by a direct measurement of the lateral displacement of each metal layer using high-speed images. Two different weld tools are used in order to investigate the effect of tool geometry on the weld formation mechanism and the overall joint quality. A series of microscopies and bond density measurements is carried out to validate the observations and hypotheses of those phenomena in multilayer ultrasonic welding. The results of this study enhance the understanding of the ultrasonic welding process of multiple metal sheets and provide insights for optimum tool design to improve the quality of multilayer joints.

Note: Accurate determination of thickness of multiple layers of thin film deposited on a piezoelectric quartz crystal

Modern day piezoelectric quartz crystal microbalances for thin film deposition control are based on Z-match equation, which is mathematically valid for deposition of a single material on a given quartz crystal. When multiple layers are deposited, thickness and deposition rate errors accumulate due to mismatch of acoustic impedance of different materials. Here we present a novel method, based on the acoustic transfer matrix formalism, for accurate determination of thickness of an arbitrary number of layers of dissimilar materials deposited on a quartz crystal. Laboratory data show excellent accuracy of the method compared to conventional Z-match equation.

Fatigue crack growth simulations of interfacial cracks in bi-layered FGMs using XFEM

An investigation of fatigue crack growth of interfacial cracks in bi-layered materials using the extended finite element method is presented. The bi-material consists of two layers of dissimilar materials. The bottom layer is made of aluminium alloy while the upper one is made of functionally graded material (FGM). The FGM layer consists of 100 % aluminium alloy on the left side and 100 % ceramic (alumina) on the right side. The gradation in material property of the FGM layer is assumed to be exponential from the alloy side to the ceramic side. The domain based interaction integral approach is extended to obtain the stress intensity factors for an interfacial crack under thermo-mechanical load. The edge and centre cracks are taken at the interface of bi-layered material. The fatigue life of the interface crack plate is obtained using the Paris law of fatigue crack growth under cyclic mode-I, mixed-mode and thermal loads. This study reveals that the crack propagates into the FGM layer under all types of loads.

Process robustness of single lap ultrasonic welding of thin, dissimilar materials

Fusion welding processes, such as resistance welding and laser welding, face difficulties in welding thin layers of dissimilar materials. Ultrasonic welding overcomes many of these difficulties by using high frequency vibration and pressure to input energy into the affected area to create a solid state weld. This paper presents a process robustness study of ultrasonic welding of thin metal sheets. Quality of the welded joints is evaluated based on mechanical tests and the quality criterion is then applied to evaluate the weldability. These results were used to determine both the optimal weld parameters and the robust operating range.

DEM simulations and experiments for projectile impacting two-dimensional particle packings including dissimilar material layers

The dynamic response of a two-dimensional ordered particle packing composed of nylon-66 spheres 6.35 mm in diameter impacted by a spherical projectile was investigated both experimentally and numerically using the discrete element method (DEM). First, the influence of the number of layers in the particle packing on wave propa- gation and post-impact movement were examined. As the number of layers increased, the contact forces reaching the base plate decreased together with the rebound velocity of the projectiles. Next, the effects of dissimilar material lay- ers were examined. The spheres in one or two layers of the particle packing were replaced with spheres made of dissim- ilar materials, that is, alumina ceramic (Al2O3) or steel, and it was found that the scattering of the nylon spheres above the dissimilar material layers increased. The experimental results obtained using force sensors at the base plate showed that the dissimilar material layers reduced the contact forces at the base plate. Furthermore, as the mass of the dissimi- lar material spheres increased, the magnitude of the contact forces at the base plate decreased, and the rebound velocity of the projectile increased.

Comparative Characteristics of Zone Spectra in Periodic Structures Formed by Layers of Dissimilar Materials in the External Magnetic Field

Comparative Characteristics of Zone Spectra in Periodic Structures Formed by Layers of Dissimilar Materials in the External Magnetic Field

Impact of Projectile on Two-Dimensional Ordered Particle Packing (Effect of Layer Number and Dissimilar Material Layers)

Impact of Projectile on Two-Dimensional Ordered Particle Packing (Effect of Layer Number and Dissimilar Material Layers)