Imperfect Interface Research Articles

Multiple Conformal-Contact Transfer of Large-Area Crack-Free Transition Metal Dichalcogenide Stacks

Abstract Atomically-thin two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as an ideal platform for both physics investigation and device applications. By stacking different layers into homo- or hetero-structures, an extra degree of freedom is involved in further tuning their properties, thereby boosting scenarios in twistronics, moiré photonics and optoelectronics. However, interfacial imperfections such as contaminations and cracks, frequently occur during the layer stacking sequence and accumulate layer by layer, greatly degenerating the interface quality. In this study, we developed a multiple conformal-contact transfer method to construct TMD stacks with crack-free intrinsic interfaces. The design of a deformable buffer layer is crucial to guarantee the conformal contact and intact transfer of each layer, contributing to the successful construction of centimetre-scale TMD stacks up to 8 layers. Precise control over spatial location and interlayer twist angle is also feasibly achieved, evidenced by the stacking-dependent interlayer exciton effects in WS2-WSe2 heterostructures. This work provides a facile and precise approach for architecting 2D stacks with perfect interfaces, which will further accelerate the customized design for their device functionalization.

Love wave propagation on nano-sized layered piezoelectric plate clamped on micropolar substrate

This research paper investigates the complex dynamics of Love wave propagation on a piezoelectric plate situated atop a micropolar elastic half-space having imperfect interface. The study delves into the multifaceted effects of flexoelectricity, micro-inertia, guiding layer thickness, and interfacial imperfection on the characteristics of Love waves. The electromechanical coupling factor which is significant in analyzing SAW device performances is also studied. Variable separable method is used to solve the governing equations and desired solution is obtained analytically. The findings contribute to a deeper understanding of Love wave propagation in complex elastic structures and development of advanced sensors and communication technologies.

Accounting of imperfect interfaces in multilayer modeling

Multilayer systems are widely used in industry for their performances as compared with homogeneous materials. The layers are usually glued together but the bonding may be imperfect (air bubble, detachment). The interfaces are generally modeled as sliding or bonded. These two behaviors can be significantly different and the actual behavior is generally somewhere in between. The vibroacoustic behavior of the structure is thus modified by the imperfect interface. Several models have been implemented to describe the dynamic behavior of multilayer systems with imperfect interfaces. In this paper, we propose an analytical model of imperfect interfaces based on the Transfer Matrix Method (TMM). Two computations are performed in parallel (one with a perfectly bonded interface and the other with a sliding interface). Instead of mixing impedances or admittances matrices, a mixing law on the state variables is applied, resulting in an equivalent global matrix which can be coupled in any multi-layer. The model is compared in terms of the sound absorption or sound transmission loss with the existing ones and is applied on different classical multilayer systems with multi-layered solid plates and a multilayer composed of a porous layer with a heavy layer which is widely used in the automotive industry.

Determination of the effective thermal conductivity of composites under the influence of an imperfect interface using a variational asymptotic-based method

Determination of the effective thermal conductivity of composites under the influence of an imperfect interface using a variational asymptotic-based method

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

AbstractA 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.

Thermal response of TBC systems subjected to non-uniform thermal shocks and periodic thermal load: Effect of Biot number and interface imperfection

This study analytically examines the temperature variations within thermal barrier coating (TBC) systems under diverse kinds of thermal loadings, such as concentrated/distributed convective thermal shocks and oscillating thermal loads. In this study, the TBC system comprises ceramic top coat (TC) and NiCrAlY alloy bond coat (BC). The transient behavior of the TBC system facing various kinds of non-uniform convective thermal shocks is elaborated via the dual-phase-lag (DPL) heat conduction model. The effect of imperfect bonding of the TC/BC interface on transient responses of the regions in the neighborhood of the TC/BC interface is studied by considering impermeable, partially permeable and completely permeable heat flux flows. Laplace and Fourier integral transforms are employed to derive the exact solutions of time-dependent temperature fields governing equations. The prominent effects of sudden thermal impulse and steady alternating thermal loading on the variations of temperature within the TC, BC and substrate are inspected. The analysis reveals that the kind of thermal load, loading parameters, thermal properties and thickness of ceramic TC directly affect the transient/periodic temperature fields inside the TBC constituents. Meanwhile, the interface imperfection and the Biot number of convective thermal load play an impressive role in the severity of thermal response of the TBC constituents.

A coupled Legendre-Laguerre polynomial method with analytical integration for the Rayleigh waves in a quasicrystal layered half-space with an imperfect interface

A coupled Legendre-Laguerre polynomial method with analytical integration for the Rayleigh waves in a quasicrystal layered half-space with an imperfect interface

Exploring the influence of coupled interfacial imperfections on SH wave propagation in layered structures with sliding interaction

Exploring the influence of coupled interfacial imperfections on SH wave propagation in layered structures with sliding interaction

Nonlocal analysis of Rayleigh-type wave propagating in a gradient layered structure with distinct interfacial imperfections

Nonlocal analysis of Rayleigh-type wave propagating in a gradient layered structure with distinct interfacial imperfections

Exploring buried interface in all-vapor-deposited perovskite photovoltaics

All-vapor-deposited perovskite solar cells (PSCs) offer promising potential for maintaining high efficiency across large-area solar modules. However, a comprehensive understanding of device stability, particularly the crucial photodegradation mechanism under sunlight exposure, remains scarce in the existing literature. In this study, we investigate thermally co-evaporated perovskite polycrystals grown on two typical organic hole-transporting layers (HTLs), macrocyclic copper (Ⅱ) phthalocyanine (CuPc) and the arylamine derivative of N4,N4,N4′,N4′-tetra([1,1′-biphenyl]-4-yl)-[1,1′:4′,1′-terphenyl]-4,4′-diamine (TaTm). Surprisingly, the robust CuPc limits the device performance with substantial non-radiative recombination loss and accelerates device degradation under light exposure. When built upon TaTm, the PSCs demonstrate a 47 times prolonged T80 lifetime (the efficiency drops to 80 % of the initial efficiency) of 1128 h by regulating the surface crystallography. By reducing the perovskite thickness to approach the buried heterojunction interface, we unravel the loss mechanism by directly observing crystallization dynamics. Our investigation reveals that surface polarity significantly influences the precursor adhesion, grain growth, and recombination dynamics at the HTL-perovskite interface. These findings underscore the critical role of the underlying surface in vapor-deposited PSCs, highlighting the potential for improved photostability through the regulation of interface imperfections.

Theoretical investigation of SH wave transmission in magneto-electro-elastic structure having imperfect interface using approximating method

Theoretical investigation of SH wave transmission in magneto-electro-elastic structure having imperfect interface using approximating method

Dynamic responses of transversely isotropic and layered elastic media with imperfect interfaces under moving loads

Flexible pavement is widely used in engineering practice but is often subjected to the moving traffic loads, with imperfect contact behavior at the interfaces between adjacent layers. This study investigates transversely isotropic and layered elastic media with imperfect interfaces under moving vertical and horizontal loads using a semi-analytical method. The governing equation for moving loads is established within a Cartesian coordinate system and by virtue of the Galilean transformation, which is further decoupled into two ordinary differential equations in terms of the powerful Cartesian system of vector functions. General solutions for any layer are obtained, and the dual-variable position method is applied to derive the semi-analytical solutions for the layered pavement in the vector function domain. The lately introduced refined conversion algorithm, originally from the discrete convolution-fast Fourier transform (DC-FFT) algorithm, is applied to obtain the solution in the physical domain, which can efficiently remove the Gibbs effect near the source. The solutions are validated by comparison with existing solutions and numerical examples are presented to study the effect of interface modulus, moving load velocity, Young’s modulus of asphalt concrete and horizontal/vertical loading ratio on the surface dynamic response of the flexible pavement. Finally, the fatigue and rutting life of the pavement structures corresponding to different imperfect interface moduli are analyzed. The present solution provides practical guidance for the design of flexible pavement.

SH waves in orthotropic piezomaterials considered surface effects

Nowadays, orthotropic piezomaterials have enormous potential in producing electronic devices owing to their inherent merits, e.g., intrinsically robust piezoelectricity. Nevertheless, the previous theoretical studies merely report surface effects on the physical properties of SH waves in a layered transversely isotropic piezoelectric structure. Filling such a blank is a special necessity for optimizing Surface Acoustic Wave (SAW) sensors. Thus, the present paper aims to determine how surface effects and interfacial imperfection affect the attributes of SH waves in a layered orthotropic piezoelectric semi-space by means of surface piezoelectricity theory and a linear spring model. The structure mainly consists of the piezoelectric film's bottom and top surface layers and the imperfect bonding between the piezoelectric film and elastic half-space. To explicitly figure out surface and imperfect interface effects on the mechanical behavior of SH waves in a layered piezoelectric half-space, we extensively derive the phase velocity equations of SH waves in an orthotropic piezoelectric plate and an orthotropic piezoelectric half-space. Then, a comparison study among SH waves in a layered piezoelectric semi-space, a piezoelectric plate, and a piezoelectric half-space is conducted. As a result, it is revealed that the attributes of SH waves dramatically vary as the piezoelectric films’ thickness changes from microscale to nanoscale. In addition, phase velocity increases or decreases with an increasing surface elastic constant or surface density due to the enhancement of stiffness or density of the whole structure. When the ratio of piezoelectric film thickness to wavelength is small, imperfect parameters substantially reduce the phase velocity owing to a decreasing interface elastic stiffness. The comparison study shows that the imperfect parameter does not influence the waves’ velocity, while the ratio of film thickness to wavelength is relatively considerable. Anisotropic piezoelectric constant essentially weakens surface effects on the waves’ velocity. Intriguingly, a linear function is acquired and is used to measure surface density via the slope of the linear function. The summaries supply unique guidelines and instructions to open an avenue for designing and manipulating surface acoustic wave nanosensors in the future.

The effect of interfacial imperfection on the nonlinear dynamic behavior of composite laminates under low-velocity impact

The effect of interfacial imperfection on the nonlinear dynamic behavior of composite laminates under low-velocity impact

Bg waves in a piezo–flexo-magnetic layered model with impedance boundary and imperfect interface

Bg waves in a piezo–flexo-magnetic layered model with impedance boundary and imperfect interface

Propagation of SH Wave in a Rotating Functionally Graded Magneto-Electro-Elastic Structure with Imperfect Interface

Propagation of SH Wave in a Rotating Functionally Graded Magneto-Electro-Elastic Structure with Imperfect Interface

A new peridynamic interface model for fracture analysis of imperfect interface

In this study, a new peridynamic interface model is proposed for the imperfect interface fracture analysis. The peridynamic interface bonds are defined for the imperfect interface modeling, and formations of bond normal and tangential interface forces are given. An extended critical bond energy density-based criterion is proposed for interface bonds failure analysis, and mixed-mode fracture mode is considered. Three specimens bonded with the imperfect interface are analyzed to verify the peridynamic interface model. The bonded deformation and fracture behaviors of imperfect interface are predicted with the proposed model, and compared to those from the theoretical and FEM results. The comparisons demonstrate that the proposed peridynamic interface model can well capture the deformation and fracture behaviors of the imperfect interface.

Response of stiffness and viscosity on the energy ratios at piezo-visco-thermo-elastic medium

This article presents a mathematical framework that characterizes a transversely isotropic piezo-visco-thermo-elastic medium within the context of the dual-phase lags heat transfer law (PVID) applied to an elastic medium (ES). Specifically, the study investigates the propagation of plane waves within the elastic medium and their interaction with the imperfect interface of the ES/PVID media. This interaction results in two waves reflecting back into the elastic medium and four waves propagating through the piezo-visco-thermo-elastic medium. The research explores the distribution of energy between the reflected and transmitted waves by analyzing amplitude ratios at the boundary interfaces, considering factors such as phase delays, viscosity effects, and wave frequency. The study illustrates the influence of boundary stiffness and viscosity parameters on these energy ratios through graphical representations. The study's findings are consistent with the principles of the energy balance law, and the research also delves into specific cases of interest. Overall, this investigation provides insights into wave behavior within complex media and offers potential applications across various fields.

Effects of physical parameters on shear wave in a porous piezoelectric model with imperfect interface

This study investigates the impact of interfacial imperfection on shear horizontal wave propagation in a microstructural coupled stress half-space beneath a porous piezoelectric layer adjacent to air. The validity of dispersion relations is shown by deriving special cases and comparing them with the classical dispersion relation of Love wave. Furthermore, a comparative analysis has been conducted to analyze the effect of various parameters on the phase velocity of shear wave by considering perfect and imperfect interfaces under electrically open and short conditions. The findings provide a theoretical framework for developing and designing underwater acoustic devices for sensing and nondestructive testing.

Cavity growth – or lack thereof – in imperfectly roll bonded sheet metal

Roll bonding is a well-established solid-state joining method that has also found commercial use. In current industrial practice, a near-perfectly bonded interface is commonly aimed for, achieved by optimizing surface preparation and rolling parameters. On the other hand, an intriguing recent study has shown that roll bonding scrap metal has the potential to provide significant environmental benefits while not jeopardizing performance, despite the resulting imperfect interface with a distribution of cavities. This present work focuses on the mechanical aspects of this observation, aiming to provide a deeper understanding of the influence (or lack thereof) of the cavity content on the mechanical behavior of a roll bonded stainless steel, and a roll bonded mild steel. Imperfectly bonded samples of both steels are studied using mechanical tests and microstructure characterization, which both revealed that the interface cavities exhibit limited growth and no crack nucleation or propagation into the interface. A numerical finite element model of the imperfectly bonded sheet confirmed a tendency for low cavity growth by showing that opening stresses on the interface cavity remain low for various geometries and loading conditions, in line with linear elastic fracture mechanics calculations. Overall, this experimental-numerical study provides insights regarding the unexpected formability (and thus the wide applicability) of imperfectly roll bonded sheets.