Multilayer Panels Research Articles

A Multi-Layer Micro-Perforated Panel Structure Based on Curled Space for Broadband Sound Absorption at Low Frequencies

A Multi-Layer Micro-Perforated Panel Structure Based on Curled Space for Broadband Sound Absorption at Low Frequencies

Mechanical characteristics determination of aircraft wing carbon plastic panel

The paper presents the method of calculating the mechanical characteristics of multilayer composite panels. The optimal sequence of laying out monolayers was selected. The mechanical behavior of the composition is determined by the ratio of the properties of the reinforcing elements and the matrix, as well as the strength of the connection between them. Among the most important requirements for the designs of modern aircraft, we can mention the minimum weight, the maximum stiffness and strength of the nodes, the maximum service life of the structures in operational conditions, and high reliability. With the help of the developed methodology, the elastic properties of the composite material with different angles of laying layers were determined. Calculations of the mechanical characteristics of carbon-plastic panels made of carbon tape and carbon fabric are given.

Sound transmission loss analysis of double-walled sandwich functionally graded carbon nanotube-reinforced composite magneto-electro-elastic plates under thermal environment

Sandwich structures with functionally graded (FG) cores have gained interest in vibroacoustic applications. This article considers the vibroacoustic properties of double-walled sandwich magneto-electro-elastic (MEE) plates with a functionally graded carbon nanotube-reinforced composite (FG-CNTRC) core layer in a thermal environment. A coupled multiphysics model is developed based on third-order shear deformation theory (TSDT) and acoustic-structure interaction. Special attention is paid to the transmission loss of this arrangement for simply supported and clamped boundaries for four different kinds of CNT distributions, namely, UD, FG-V, FG-O, and FG-X. Sound velocity potential, normal velocity continuity conditions, and Hamilton's principle are used to generate the coupled vibroacoustic equations, which are then solved using the Galerkin method. The effects of boundary conditions, CNT distributions, cavity depth, multiphysics coupling fields, and temperature on the STL are comprehensively studied. The results provide guidelines for tailoring the dynamic response of these materials to achieve enhanced acoustic insulation performance. It enhances fundamental understanding and enables the engineering design of multilayered composite panels with optimized vibration and noise control capabilities.

Numerical vibroacoustic analysis of multi-layered composite structure under hygrothermal loading using coupled FEM-IBEM micromechanical model

The vibroacoustic responses of multi-layer composite shallow shell panels subjected to harmonic mechanical excitation in hygrothermal environment is numerically investigated. A homogenized micromechanical finite element (FE) based on the higher-order mid-plane kinematics replicating quadratic function as well as the through the thickness stretching effect together with the indirect boundary element (IBE) scheme has been first time employed. The isoparametric Lagrangian element with zero-order Hermitian interpolation function (10 degrees of freedom per node) is used for structural model discretization to attain the hygro-thermo-elastic natural frequencies via Hamilton’s principle. The uniqueness of the model is the incorporation of the effective material properties under combined hygrothermal loading via a micromechanics approach. An IBE method is then implemented to attain structure-surrounding coupling and the Helmholtz wave equation is solved to compute the sound radiation responses. The effectiveness of the model is tested by converging it with the similar analytical/numerical results as well as the experimentally acquired data for vibrational as well as acoustic responses. The present scheme is further hold out for solving diverse numerical illustrations. The geometrical parameters, volume fraction of fiber, layup, and support conditions alongside the hygrothermal load is found to have significant influence on the hygro-thermo-acoustic characteristics. The functional inferences will assist in designing the imminent multi-layered structures that serve under the influence of severe hygrothermal loading during high-performance engineering applications.

Theoretical evaluation of nonlinear thermomechanical deflection characteristics of damaged (cracked) layered composite structural panel bonded with shape memory alloy (SMA) fibre and experimental verification

Thermomechanical deflections of the cracked multi-layered composite panels were investigated numerically using full-scale geometrical nonlinearity and higher-order deformation kinematics. The panel is embedded with shape memory alloy (SMA) fiber to improve the structural strength and integrity under thermomechanical loadings. The theoretical model for the SMA-reinforced cracked laminated composite shell panel is derived considering the material and geometrical nonlinearity. The numerical and experimental cases were performed for the intact and damaged cylindrical panels by varying the environmental conditions. Additional examples of structural and geometrical parameters have been conducted, including SMA-related data.

Nonlinear forced response of doubly-curved laminated panels composed of cnt patterned layers within first order shear deformation theory

In this study, the solution of the nonlinear forced vibration (NFV) problem of double curvature panels consisting of inhomogeneous (INH) nanocomposite (NC) layers is discussed within first order shear deformation theory (FSDT), taking into account the viscous damping effect. First, the mechanical properties of laminated double curvature panels composed of carbon nanotube patterned layers are modeled mathematically. Then, based on FSDT with a von Kármán-type nonlinearity derived the nonlinear basic relationships and partial differential equations (PDEs). The expression for the NFV frequency of multilayer panels made of inhomogeneous nanocomposite layers (INHNCLs) is obtained within FSDT, using the multi-scale method to the nonlinear PDEs for the first time. Finally, the influences of the external excitation, nonlinearity, transverse shear strains, number and arrangement of layers and CNT-models on the forced vibration frequencies are studied in detail.

Investigating the disparities between experimental and computational analyses of thermal performance in prefabricated wall panels

Prefabricated buildings are increasingly popular worldwide, driven by technological advancements and the demand for sustainable and energy-efficient construction. However, the thermal performance of typical multi-layered and compacted prefabricated wall panels remains uncertain, leading to overdesigned HVAC and building envelope systems. This results in higher utility bills, unnecessary expenses, and increased material, labor, and transportation costs. While experimental analysis and computational simulations have proven effective for measuring the thermal performance of on-site wall panels (e.g., precast concrete, masonry), their effectiveness for exterior insulation finishing system (EIFS) prefab wall panels is unclear. This study aims to test the hypothesis that both experimental and computational analyses accurately measure the thermal performance of EIFS prefab wall panels under various climate conditions and yield to similar results. To achieve this, (1) experimental test analysis was conducted in an environmental chamber based on ASTM C1363 and ISO 8990 standards, and (2) computational simulation was conducted by employing THERM® at hot (65 °C) and cold (−16 °C) climates. The results showed that the experimental thermal resistance exceeded the computational thermal resistance by about 17% across hot and cold climates. These thermal resistances were then incorporated into a typical hospital building prototype in the U.S. modeled by U.S. Department of Energy in EnergyPlus™, resulting in substantial cost savings of approximately $396,000 over a 20-year lifespan due to the thermal resistance variations between experimental and computational analyses. The savings were achieved through a reduction in construction costs, accurate HVAC system selection, and lower utility bills. This study contributes to the improvement of prefabricated building design and energy performance analysis, leading to potential cost reductions in HVAC and building envelope system overdesign.

Ballistic performance of multi-layer fabric panels considering fabric structure and inter-yarn friction

The importance of inter-yarn friction to ballistic fabric has been widely investigated. However, the couple effects of inter-yarn friction, fabric structure and number of layers have not been explored. Therefore, this paper put forward to investigate the ballistic performance of multi-layer fabric panels with different weave structure and inter-yarn friction. Three different structures (plain, sateen and UD-like), various number of layer (1-layer, 4-layer, 8-layer and 12-layer) and three levels of coefficients of friction were considered and their effects on the ballistic performance will be discussed through finite element (FE) method. The impact velocity is set as 475 m/s and the projectile is a 1 g steel flat cylinder with both the diameter and height of 5.5 mm. It has been found that the sateen fabric structure with 12-layer and higher coefficients of friction firstly reduces the projectile velocity to zero, while the corresponding plain structure and the UD-like structure reduce the projectile velocity to 125 m/s and 200 m/s individually, which indicates that when the number of layer and coefficients of friction are both much larger, the sateen fabric shows the best ballistic performance among the three structures. The reasons behind are as following. As far as the structure concerned, sateen structure has more interlacements than UD-like fabric and more straight sections than plain fabric. In addition, at higher coefficients of friction, this structure enables higher stress distribute in more layers and in larger areas than plain fabric and UD-like fabric and give rise to a layer-by-layer fracture but not fracture simultaneously.

Validation of Bayesian design for broadband microslit panel absorbers using causal inference.

This paper discusses experimental validations of multilayer microslit panels (MSPs) designed via Bayesian inference to obtain both high sound absorption and wide bandwidth simultaneously. Microslit perforation in thin panels is similar to microperforated panels [Xiang, Fackler, Hou, and Schmitt (2022). J. Acoust. Soc. Am. 151(5), 3094-3103]. MSP absorbers in single-layer configurations are functioning in a limited frequency range. By stacking the MSPs in multiple layered structures, absorbing performance may be widened in frequency ranges while retaining high absorption coefficients. Besides design challenges of multiple MSPs in layered structures to fulfill a practical requirement and minimize fabrication complexity, this paper further discusses challenges in experimental validations when experimental results undesirably deviate from the initial Bayesian design. Causation analysis is applied to the validation efforts where a causal model-based inference effectively provides causal reasoning of fabrication inaccuracies. Along with the causal inference, a causal reasoning conducted in this work can guide corrections due to fabrication inaccuracies during the iterative validation process.

Delamination Localization in Multilayered CFRP Panel Based on Reconstruction of Guided Wave Modes

Multi-layered composite materials are being used in various engineering fields, such as aerospace, automobile, and wind energy, because of their superior material properties. Due to various impact loads during the service life of composite structures, different types of defects can occur, such as matrix cracking, fiber breakage, delaminations, etc. In this research, a novel SHM technique for delamination detection and localization using a minimum number of sensors is proposed. The analytical, numerical, and experimental analysis of GW was performed to increase the probability of detection and localization of delaminations in CFRP material. A new analytical model was developed, which enables identifying converted and transmitted modes in the presence of multiple GW modes. A 2D FFT-based spatial filtering was used to filter the GW modes. The dominant A0 mode was separated to inspect the delamination. Phase velocity is one of the important features in GW inspection to localize the delamination. A phase spectrum approach was developed to reconstruct the phase velocity dispersion of the GW modes in case material properties are unknown.

Free Vibration Analyses of Stiffened Functionally Graded Graphene-Reinforced Composite Multilayer Cylindrical Panel

In this paper, the free vibration response of a stiffened functionally graded graphene nanoplatelet (GPL)-reinforced composite multilayer cylindrical shell panel is studied for the first time. The shell is stiffened by both stringers and rings. Additionally, the effect of reinforcing the shell panel, ring and stinger with GPLs is independently studied. Halpin–Tsai relations are employed to evaluate the mechanical properties of the shell panel, rings and stringers. The first-order shear deformation shell theory, accompanied by the Lekhnitsky smeared stiffener model, using the numerical finite element method and Hamilton principle, is employed to develop the governing motion equations of the shell panel. Four different types of GPL patterns, including FG-A, FG-X, FG-O and UD, are assumed across the thickness of the shell panel, rings and stringers. The effects of different factors, including various weight fractions and patterns of GPLs nanofillers, the geometry of the shell panel and stiffeners and two displacement boundary conditions, on the natural frequencies of the shell panel, have been studied.

On the Buckling of Simply Supported Anisotropic Sandwich Plates

Here, the elastic stability behavior of simply supported anisotropic sandwich flat panels subjected to mechanical in-plane loads is investigated using analytical approach. The formulation is based on first-order shear deformation theory and the shear correction factors employed are based on energy consideration that depends on the lay-up as well as material properties. The governing equations are obtained using the Raleigh-Ritz method assuming a combination of sine and cosine functions in the form of double Fourier series for the displacement fields. The effectiveness of the integrated formulation is tested for global characteristics considering examples related to multi-layered laminates and sandwich panels for which solutions are available.

Influence of core topology on blast mitigation application of multi-layered honeycomb core sandwich panel

In the past years, the aluminium honeycomb core sandwich panel has emerged as a promising blast mitigation solution owing to its high energy absorbing capacity under impulsive loading. To enhance its performance against the blast load, it is important to understand the mechanical behaviour of honeycomb core sandwich panel with varying core configurations. The present study investigates the difference in load mitigation behaviour of sandwich panel under blast loading with different honeycomb core topologies. Three types of honeycomb core topology i.e., square, circular, and hexagonal are considered in the present study. The performance of the sandwich panels under blast loading is compared for two criteria i.e., constant mass (or aerial density) and constant cell size. The influence of a multi-layered core along with the intermediate sheets on the blast resistance of sandwich panel is further examined under blast load. It is observed that the multi-layered core and intermediate sheets not only strengthen the sandwich panel but also make it significantly stronger under the blast loading in comparison to the single layer sandwich panel. The role of intermediate sheets in energy dissipation is observed to be insignificant in multi-layered sandwich panel for the parameters considered in this investigation. Further, it is observed that the difference in energy dissipated by front face sheet and back face sheet is increased with increase in the number of layers of cores.

Modeling of thermo-elastic properties of composite material in stability problems of multilayered shells

Thin-walled structures, the elements of which are plates and shells made of composite materials, are increasingly used in various industries. The growing needs of practice and the introduction of new composite materials require further improvement of the calculation methods of shell structures of inhomogeneous structure. Therefore, the problem of developing an adequate method of analyzing the behavior of shells made of composite materials with a multilayer structure is relevant. The work is devoted to the application of the developed method of finite elements for the analysis of geometrically nonlinear deformation and stability of elastic shells to the problem of the study of shells, the layer materials of which are composites of a fibrous structure. The method of structuring materials through the shell thickness and plan by using a universal 3D finite element is applied to model the thermoelastic properties of a ingomogeneous material. Determination of the effective characteristics of the composite material is realized by the structural micromechanical parameters of its components based on known methods of predicting elastic constants for this model of the composite material. The multilayer finite element, created within the framework of the developed approach, can be exploited to the problems of calculating thin elastic shells from both traditional and composite materials. The results of investigation of a multilayer composite panel using various micromechanical techniques are presented. The results of the study of a multilayer composite panel obtained by various micromechanical methods are given. These results are consistent with those obtained using the NASTRAN software. The new modification of the developed finite element makes it possible to analyze the stress-strain state and stability of multi-layer shells made of fibrous composite materials reliably, with accuracy acceptable for engineering calculations.

Flutter of carbon-based nanohybrid composite panels

Recently, carbon-based composite aerospace and mechanical structures have considerable attention due to their great material and mechanical properties. Carbon nanotubes (CNTs) or graphene platelets (GPLs) reinforcements for different matrices are common for the design of modern multilayer structures. In the present paper, the supersonic flutter of nanohybrid composite multilayer panels is examined and discussed. The nanohybrid multilayer panel is made of different technologically justified configurations of polymer layers reinforced by CNTs and GPLs The effective material properties of each CNTs and GPLs layer are determined according to two well-established homogenization techniques: the Mori–Tanaka scheme and the modified Halpin–Tsai model, respectively. Reddy’s third-order shear deformation theory is applied to avoid determining shear correction factors for different distributions of material properties. Hamilton’s principle and the first-order piston theory are applied to formulate aeroelastic coupled equations of motion of the panel. The numerical meshless method is employed to discretize dynamic equations and find generalized multi-parametric characteristic equations functionally dependent on the parameters of the structure with different boundary conditions. The accuracy of the obtained solution and results is examined by comparing the determined natural frequency and critical aerodynamic pressure with those obtained in previous studies. Then, a comprehensive parametric study is carried out to show the effects of hybridization of different distribution patterns of CNTs and GPLs, weight fractions, total layer number, and aspect ratio of hybrid composite panels on the flutter bounds. Results show that the present method provides a highly effective general numerical model for flutter analysis of hybrid nanocomposite panels with different boundary conditions for all thickness categories including thick plates. Moreover, an optimization nanoparticles distribution for the flutter of the nanohybrid composite panel has been obtained.

Multi-objective optimization of multi-core composite aluminum honeycomb sandwich panels for improved crashworthiness

This article presents the low-velocity impact response of the multi-core aluminum honeycomb sandwich panel with composite face sheets using LS-DYNA-based finite element simulation. The effect of geometric parameters like cell size, cell height, cell thickness, and facesheet thickness, on structural response, is explored. The interaction effect of these geometric parameters, effect of number of layers/cores and characteristic force-time and energy-time curves for multilayer composite sandwich panels are also studied. Finally, these geometric parameters are optimized for better crashworthiness designs, followed by crashworthiness design recommendations.

Higher-order model with interlaminar stress continuity for multi-directional FG-GRC porous multilayer panels resting on elastic foundation

In this paper, the bending behaviors of multilayer panels composed of multi-directional functionally graded porous graphene reinforced composites (GRCs) resting on a two-parameter Winkler-Pasternak elastic foundation are investigated for the first time based on a higher-order layerwise model with interlaminar stress continuity. Since the material properties are discontinuously distributed through the thickness of specific multilayer structure and multi-directional graded in each layer of the panels caused by the distribution of both graphene and porosities, traditional higher-order plate theories have difficulty in predicting continuous stress fields efficiently. For this reason, the proposed model adopts higher-order interpolation functions and piecewise descriptions for transverse shear-stress fields to obtain accurate results satisfying continuity of interlaminar stresses, accounting for the distribution of material properties along the thickness direction and multilayer structure of the panel. Furthermore, to perform efficient numerical results for multi-directional functionally graded materials, the proposed higher-order layerwise model is combined with graded finite element method (GFEM) by sampling material properties directly at the Gaussian points within each element. Lastly, numerical examples are presented to verify the accuracy and efficiency of the proposed model, and the effects of porosity and graphene distribution patterns, graphene weight fraction, porosity coefficient, and elastic foundation parameters are investigated.

Optimization of the transmission loss of a multilayer panels using the genetic algorithm

AbstractAn optimization method of the acoustic absorption of multilayer panels composed of porous, elastic, and viscoelastic materials is presented in this paper. The used objective functions consist on the maximizing of the sound Transmission Loss (TL) and the minimization of the mass of the configuration. For this, the genetic algorithm was used coupled with an analytical computation of transfer matrix of the studied panel. This study aimed to found the optimal values of the thicknesses of each layer with a total thickness which should not exceed 30 mm. The others parameters are keeping constant. The developed method was applied to a two‐layer panel. The obtained results are analyzed giving sources to choose between the studied configurations.

Research on the comparison effect of urban residents' consumption

As an important component of gross domestic product, expanded consumer spending is essential for promoting economic growth. To provide a realistic basis to support effective policy formulation to meet diversified consumption needs and enhance the fundamental role of consumption in economic development, this study constructs a multi-layer panel extended linear expenditure system (ELES) model that includes external habit formation (comparison effect). The study empirically analyses the comparison effect and causes using nested consumption data of urban residents from 31 provinces in China from 2002 to 2019. The results show that the comparison effect is relatively large for urban residents’ subsistence consumption expenditure. In contrast, the comparison effect in development and enjoyment consumption expenditure is smaller overall. Second, a widening income gap increases food and clothing comparison effects. Increased educational attainment reduces comparison effects on housing, health care and transport. Significant geographical differences in the comparison effect on various types of consumer spending are evident based on the degree of regional economic development. Finally, the study proposes policy recommendations of increasing residents’ income, raising educational levels and promoting balanced regional development. The most significant contribution of this study is the innovative multi-layer panel ELES statistical model which incorporates external habit formation theory to systematically analyse comparison effects and causes.

Reinforcement of cellular concrete with composite materials

Cellular concrete, such as gas silicate or foam concrete, has good thermal performance and is widely used in modern construction. Possessing acceptable parameters for compression, cellular concrete has low tensile and shear characteristics. This leads to the appearance of cracks in building structures made of cellular concrete, such as partitions, interior walls, etc. Therefore, solving the problems of increasing the bearing capacity of cellular concrete is important and relevant. The purpose of this study is to study the increase in the bearing capacity of cellular concrete reinforced with composite materials under the action of temperature and bending moments. The problem is solved by the finite element method and analytical methods. As a result of the work carried out, the characteristics of wall panels reinforced with composite rods were obtained under the action of temperature and bending moments in structure. Composite materials in the form of canvases are widely used to enhance the bearing capacity of aged reinforced concrete structures or those that have received defects due to man-made impacts. Consideration of methods for determining the given characteristics of a multilayer composite canvas is necessary for conducting a study of the bearing capacity of reinforced concrete structures reinforced with composite canvases or canvases. In this paper, methods are presented for determining the given characteristics of multilayer composite canvases and panels with different arrangements of the base layers. The analysis of the obtained results showed that reinforcement of the composite materials can significantly increase the tensile strength and shear of the gas silicate of the building.