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This paper presents a data-driven structural health monitoring (SHM) method by the use of so-called reduced-order models relying on an offline training/online use for unidirectional fiber and matrix failure detection in a 3D woven composite plate. During the offline phase (or learning) a dataset of possible damage localization, fiber and matrix failure ratios is generated through high-fidelity simulations (ABAQUS software). Then, a reduced model in a lower-dimensional approximation subspace based on the so-called sparse proper generalized decomposition (sPGD) is constructed. The parametrized approach of the sPGD method reduces the computational burden associated with a high-fidelity solver and allows a faster evaluation of all possible failure configurations. However, during the testing phase, it turns out that classical sPGD fails to capture the influence of the damage localization on the solution. To alleviate the just-referred difficulties, the present work proposes an adaptive sPGD. First, a change of variable is carried out to place all the damage areas on the same reference region, where an adapted interpolation can be done. During the online use, an optimization algorithm is employed with numerical experiments to evaluate the damage localization and damage ratio which allow us to define the health state of the structure. [ABSTRACT FROM AUTHOR]

This study investigates the axisymmetric postbuckling of functionally graded graphene platelets reinforced composite (FG-GPLRC) annular plates resting on nonlinear elastic medium in thermal environment. Five kinds of graphene platelets (GPLs) distribution patterns including U -pattern, X -pattern, O -pattern, A -pattern, and V -pattern have been considered. The nonlinear equilibrium equations and associated boundary conditions are obtained based upon the Mindlin plate theory. The governing equations are solved via the generalized differential quadrature method (GDQM). Afterwards, the direct iterative method is implemented to accomplish postbuckling loads using the buckling mode deflection. In order to confirm the accuracy of the present model, comparisons between our data with those published in the available literature are put forth. Eventually, this paper emphasizes the impact of diverse parameters such as geometrical parameters of the structure, GPLs patterns and their geometric, GPLs weight fraction, boundary conditions, elastic medium's parameters and temperature change on the buckling and postbuckling response of nanocomposite annular plates. It can be found that elastic medium overshadows the applicability of distribution patterns and weight fraction of GPLs. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper deals with the formulation of a novel four-node quadrilateral finite element based on the first-order shear deformation theory and using the strain-based approach for static and free vibration responses of composite plates. The developed element has five degrees of freedom per node and its displacement functions contain higher-order terms that satisfy the rigid body modes and are based on assumed strains satisfying compatibility equations. The efficiency of the present element is demonstrated by applying it to sandwich and symmetric/antisymmetric laminated composite plates with various shapes, boundary conditions, side-to-thickness ratios, stacking sequences, fiber orientation angles, and different types of loads. The obtained results are compared with published analytical and numerical solutions that have proved excellent accuracy and efficiency in predicting bending and free vibration of laminated composite plates and have shown that this element is free of shear locking. [ABSTRACT FROM AUTHOR]

A finite element dynamic model of the sandwich composite plate was developed based on classical laminate theory and Hamilton's principle. A 4-node, 7-degree-of-freedom three-layer plate cell is constructed to simulate the interaction between the substrate, the viscoelastic damping layer, and the piezoelectric material layer. Among them, the viscoelastic layer is referred to as the complex constant shear modulus model, and the equivalent Rayleigh damping is introduced to represent the damping of the substrate. The established dynamics model has too many degrees of freedom, and the obtained dynamics model has good controllability and observability after adopting the joint reduced-order method of dynamic condensation in physical space and equilibrium in state space. The optimal quadratic (LQR) controller is designed for the active control of the sandwich panel, and the parameters of the controller parameters, the thickness of the viscoelastic layer, and the optimal covering position of the sandwich panel are optimized through simulation analysis. The results show that the finite element model established in this paper is still valid under different boundary conditions and different covering methods, and the model can still accurately and reliably represent the dynamic characteristics of the original system after using the joint step-down method. Under different excitation signals and different boundary conditions, the LQR control can effectively suppress the vibration of the sandwich plate. The optimal cover position of the sandwich plate is near the solid support end and far from the free-degree end. The parameters of controller parameters and viscoelastic layer thickness are optimized from several angles, respectively, and a reasonable optimization scheme can be selected according to the actual requirements. [ABSTRACT FROM AUTHOR]

This paper aims to study the influence of key design parameters (e.g., reinforcement ratio, cover thickness, stud spacing, and thickness of the ultra-high-performance concrete (UHPC) layer) on the longitudinal and transverse bending performance, as well as the cracking load and ultimate bearing capacity calculation theory of steel–UHPC lightweight composite deck (LWCD) structure. Four transverse bending tests and four longitudinal bending tests on steel–UHPC composite plates and steel–UHPC composite beams were conducted, respectively. The refined finite element models of components with different key design parameters based on ABAQUS were established. The influences of different key design parameters on the transverse and longitudinal flexural behaviors (e.g., load-mid-span displacement curve, cracking stress, stiffness, elastic limit load, critical slip load, ultimate bearing capacity and ductility) were compared and analyzed in detail. The ultimate bearing capacity can be improved by increasing the thickness of UHPC layer and the reinforcement ratio of longitudinal reinforcement, and reducing the cover thickness and the spacing of studs. According to the longitudinal bending characteristics of the steel–UHPC lightweight composite deck structure, the calculation formulas for the cracking load and the ultimate bearing capacity of the steel–UHPC composite beam are proposed, and the calculated values are in good agreement with test results (the errors are basically within 10%), which is convenient for practical engineering applications. [ABSTRACT FROM AUTHOR]

Without regarding interlayer continuity of transverse shear stresses in the displacement expressions, traditional higher-order plate theories have difficulty in predicting continuous shear stress fields accurately for multilayered functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates with independent CNT distributions in each layer. In this paper, a new higher-order continuous shear stress multilayered plate model is developed for high-accuracy analysis of FG-CNTRC plates. In the theoretical formulation, higher-order interpolation functions and piecewise descriptions are adopted for transverse shear stress fields. By fulfilling the interlayer continuity of shear stresses and displacements, the displacement expressions for FG-CNTRC plates are formulated. The accuracy of the proposed model is determined by two kinds of parameters: the order of assumed transverse shear stress fields and the number of subdivisions. Compared with traditional higher-order theories, the proposed model can accurately predict continuous transverse shear stresses for FG-CNTRC plates with different CNT configurations by constitutive relations directly. Additionally, a four-node rectangular plate element associated with the proposed model is formulated. Results show that the proposed model agrees well with the exact solutions and results from ANSYS. With the same amount of calculation, the proposed higher-order model has higher accuracy than the model with more subdivisions, especially for asymmetric plates with discontinuous CNT ply angle. [ABSTRACT FROM AUTHOR]

This paper presents a coupled thermoelastic finite element formulation for static and dynamic analysis of composite laminated plates with embedded active shape memory alloy (SMA) wires, which accounts for both the phase transformation and the nonlinearity effects of SMA wires. The equations of motion are obtained by using Hamilton's principle and first-order shear deformation theory (FSDT). Furthermore, based on Brinson's one-dimensional phase transformation constitutive law, a novel coupled thermoelastic finite element model that enables analysis of the SMA hybrid composite (SMAHC) plate is developed. The accuracy and efficiency of the developed computational model for analysis of SMAHC plates are reinforced by comparing theoretical predictions with data available from the literature. The results of the numerical examples also show the ability of the proposed model to predict the thermal-mechanical behavior of SMAHC plates in accordance with SMA's hysteresis behavior. In addition, based on the proposed model, the influence of temperature as well as SMA volume fraction, pre-strain value, boundary condition and layup sequence on the static bending and free vibration behavior of the SMAHC plates is investigated in detail. The results of parametric analysis show that the variations of both static deflection and natural frequency of the SMAHC plate over temperature exhibit a nonmonotonic behavior. [ABSTRACT FROM AUTHOR]

Purpose: This paper presents the effect of damage in the composite substrate on the controlled response of a smart composite plate. Further, the effective location of piezo patches to control the vibration of a composite plate has also been studied. Method: Two different bending modes have been considered in the study, namely, longitudinal bending and twisting. A negative velocity feedback algorithm has been employed to obtain the controlled response of the smart plate. Using the linear constitutive relations, a layer-by-layer finite element (FE) formulation has been developed for the dynamic analysis. The validation of the formulation has been carried out by comparing the natural frequencies and vibration control response with the results from the literature. Conclusion: It can be seen from the study that the damage below the sensor is influencing the controlled response of the plate more than that of the damage below the actuator. [ABSTRACT FROM AUTHOR]

This paper covers the modeling and testing of a helicopter tailboom integrated with a fluidic flexible matrix composite (F²MC) damped vibration absorber. In an advance over previous work, the F2MC absorber presented in this paper treats a combination of tailboom lateral, torsional, and vertical vibrations. A finite element structural model of a laboratory-scale tailboom is combined with a model of attached F2MC tubes and a tuned fluidic circuit. Vibration reductions of over 75% in a coupled 26.8-Hz lateral bending/torsion tailboom mode are predicted by the model and measured experimentally. These results demonstrate that F2MC vibration control is viable at higher frequencies and for more complex vibration modes than previous research had explored. A new absorber with a fluidic circuit that targets two tailboom vibration modes is designed and experimentally tested. On the lab-scale tailboom testbed, the absorber with this circuit is shown to provide vibration reductions of over 60% in both a 12.2-Hz vertical mode and a 26.8-Hz lateral bending/torsion mode. Using this new absorber, vertical and lateral/torsion mode damping are achieved with almost no added weight relative to a purely vertical absorber. [ABSTRACT FROM AUTHOR]

In this paper, for the first time, the deep learning technique of the artificial neural network method is used to determine the free vibration parameters of the rectangular bistable composite plates. For this purpose, first, the static and free vibration behaviours of a cross-ply bistable composite plate are studied using analytical, finite element and experimental methods. By comparing them, it is turned out that there is a considerable difference among obtained natural frequencies so that the analytical method is only able to determine the fourth natural frequency and cannot estimate the first three natural frequencies. To solve this problem, the deep neural network is employed to model the modal parameters of the bistable laminate as an explicit mathematical relationship that can be generalized to the other bistable composite plates. This mathematical relation makes it possible to obtain the natural frequencies in each of the stable configurations based on the geometric dimensions of the plate. In the following that, the inverse problem method is considered and the mode management capability is investigated. A fast swarm intelligence algorithm called firefly algorithm is used to optimize the optimization function of the mode management problem. Mode management using the evolutionary algorithm provides the appropriate physical dimensions of the plate according to the scenarios for natural frequencies arrangement. The results are validated by comparing them with those obtained by the finite element method and experiment test, which results show that this method estimates the modal parameters with high accuracy. The method used in this paper can also be applied to determine the modal parameters of other morphing structures. [ABSTRACT FROM AUTHOR]

The paper investigates the normal interaction between the steel striker, carbon fiber and aramid fiber reinforced plastic plates at a speed ranging from 166.6 to 184.2 m/s. A series of physical and numerical experiments with impact load is conducted to design a mathematical model and numerical algorithm for the composite plate. The behavior and fracture of composites are described by the elastic-brittle model accounting for their different compressive and tensile strengths. The numerical simulation utilizes the finite element method in the EFES software developed by the authors. [ABSTRACT FROM AUTHOR]

This paper aims to study the feasibility of implementing a new bio-composite with a sandwich structure made from date palm tree waste. This is done by valuing such waste, often left in palm groves and burned under most circumstances, which can be a vital resource at the lowest cost. This work has developed several sandwich-structured composite plates based on this waste. The skins are composite materials based on an epoxy matrix and palm tree fibers (Epoxy/Rachis fibers); the core was made of raw wood or a composite with petiole wood particles. After three-point mechanical bending tests, macroscopic analysis and SEM micrographs were used to determine what kind of damage the specimen had. Characterization tests on the new bio-composites showed good thermal properties; with a thermal conductivity below 1W/mK is between 0.0148W/mK and 0.0178W/mK. It is also characterized by its low volumetric mass, less than 1.2g/cm³. These properties make it a good thermal insulator, especially in environmentally friendly bio-construction areas making a sandwich-structured composite using palm tree waste is a very effective, environmentally friendly, and economically inexpensive option. [ABSTRACT FROM AUTHOR]

Background: The plate structure is one of the typical components of the mechanical system and its vibration research has attracted full attention. Graphene platelet is a new high-performance nano-reinforced filler and its emergence provides an opportunity to improve the vibration properties of conventional composite plate structures. Purpose: The free vibration characteristics of the three-phase composite thin plate reinforced synergistically by graphene platelets (GPLs) and carbon fibers are studied in this paper, and we also analyze the influences of the content changes of different reinforcements on the natural frequencies and mode shapes of the three-phase composite thin plate. Methods: The effective material properties of the three-phase composite material are calculated according to a combination of the Halpin–Tsai model and the micromechanics approach. The separation method of variables is used to obtain the natural frequencies and mode shapes of the three-phase composite thin plate under different boundary conditions. The accuracy of results from the separation method of variables is verified by comparison with the references. Conclusions: The synergistic effect of GPLs and carbon fibers can increase the natural frequencies of a composite thin plate under different boundary conditions. The mode shape transformation phenomena mostly appear in the higher order vibrations of the three-phase composite thin plate when the GPLs content increases. The appearance of mode shape transformation is accompanied by a change in the rate of frequency growth. These results have important theoretical significance for a widespread engineering application of the three-phase composite structure. [ABSTRACT FROM AUTHOR]

In order to achieve high efficiency and low damage processing of hard and brittle materials, composite ultrasonic vibration-assisted face grinding (CUVAFG) has been proposed by comprehensively combining the high efficiency of axial ultrasonic vibration grinding (UVAG) and the low damage of elliptic ultrasonic vibration grinding (EVAG). However, the three-dimensional ultrasonic vibration brings about a more complicated machining mechanism than the previous ultrasonic vibration-assisted grinding methodology. Hence, in order to explore the grinding mechanism in deep, this paper first developed a new model of undeformed chip thickness for CUVAFG from the perspectives of the kinematic mechanism and elastic-plastic deformation mechanism. Then the influences of different processing parameters on interference rate and undeformed chip thickness were further confirmed. Finally, CUVAFG experiments of silicon carbide (SiC) ceramics were conducted to study the relationship between the undeformed chip thickness and the resultant grinding forces, specific grinding energy, ground surface morphology and roughness, and subsurface damage. It is found from the experimental results that the critical chip thickness of brittle-ductile transition in CUVAFG is between 0.31 and 0.35 μm. As the undeformed chip thickness is less than the critical value, the grinding forces and the specific grinding energy increases with the undeformed chip thickness, but the ground surface roughness decreases with improved surface morphology and shallow subsurface damage. After exceeding the critical value, the grinding force remains unchanged, the specific grinding energy decreases, and ground surface roughness increases with deteriorated surface morphology and deepened subsurface damage. For the purpose of good machining surface integrity, it is essential to guarantee that the undeformed chip thickness is less than the critical value. The computational and experimental results have demonstrated the contribution of the developed undeformed chip thickness model to understanding the grinding performance of hard and brittle material by CUVAFG. • A novel undeformed chip thickness model that considers the elastic-plastic deformation of workpiece material is proposed. • The interference area and rate are proposed to explain the influence of processing parameters on undeformed chip thickness. • The critical undeformed chip thickness of brittle-ductile transition for silicon carbide by CUVAFG is confirmed in the range of 0.31–0.35 μm. • The depth of the subsurface damage layer increases from 2.1 μm to 66.7 μm with the increase of undeformed chip thickness. • The grinding forces, ground surface roughness, and specific grinding energy are reduced by 30 %, 42 %, and 93 %, respectively. [ABSTRACT FROM AUTHOR]

The paper deals with bifurcation and/or non-bifurcation post-buckling curves of composite plates under biaxial compression. For different lay-up sequences, a coupling, i.e. extension-bending (EB) is considered. The current investigations present distinct equilibrium paths describing when they have bifurcation-type and/or non-bifurcation-type responses. The novel parameter (i.e. EB coupling imperfection) is calculated to show the amount of non-bifurcation in the equilibrium path as a quantitative parameter. For the case of non-square plates, a novel mixed-mode analysis is conducted. The effects of different characters in laminated composites such as layer arrangement, loading ratio, aspect ratio, and boundary conditions are investigated. A novel result concluded in the numerical examples where there are some possibilities to have different mode shapes in linear and non-linear buckling analysis. FEM results of ANSYS software verify the results of analytical equations. [ABSTRACT FROM AUTHOR]

The combined influences of initial geometrical imperfection, elasticity of in-plane constraints of edges, elastic foundations and elevated temperature on the nonlinear vibration and dynamical response of carbon nanotube-reinforced composite rectangular plates are investigated in this paper. Carbon nanotubes (CNTs) are reinforced into matrix according to functionally graded distributions. The properties of CNTs and matrix are assumed to be temperature dependent and effective properties of nanocomposite are determined using an extended rule of mixture. Governing equations in terms of deflection and stress function are established within the framework of thin plate theory including von Kármán nonlinearity, geometric imperfection and interactive pressure from elastic foundation. Analytical solutions are assumed for simply supported plates and Galerkin method is applied to result in nonlinear time differential equation. This nonlinear equation is solved using fourth-order Runge–Kutta scheme. Parametric studies are executed to examine numerous influences on the natural frequency, nonlinear to linear frequency ratio and nonlinear dynamical response of CNT-reinforced composite plates. The results reveal that increase in imperfection size results in increase and decrease in natural frequencies and the amplitude of forced vibration, respectively. In contrast, it is found that the elevated temperature reduces the natural frequencies and enhances the amplitude of forced vibration. [ABSTRACT FROM AUTHOR]

In recent years, the focus on reducing the environmental impact of construction has shifted from operational carbon emissions to embodied carbon or materials due to the constant decarbonization of the energy sector. This paper compares the life‐cycle assessment (LCA) of a collective housing building in Portugal, examining four structural solutions: composite steel and concrete, light steel framing, prefabricated reinforced concrete, and cross‐laminated timber load‐bearing walls. This study aims to aid construction professionals in making environmentally informed decisions by comparing design options composed of different materials and highlighting potential improvements in environmental performance. [ABSTRACT FROM AUTHOR]

A static package design of a functionally graded porous plate in microscale which is coated by two polymeric piezoelectric carbon nanotubes reinforced composite (CNTRC) face sheets is provided in this study. The microstructure rests on the Pasternak foundation and is subjected to thermal load. Furthermore, face sheets are subjected to the electric field. With the aid of a quasi-3D hyperbolic shear deformation theory, governing equations of the microplate are derived and then its critical buckling loads are calculated. The properties of all layers alter continuously along with thickness direction due to the CNTs and pores distributions. The size effects are captured by the means of modified couple stress theory (MCST). By conducting the current study, the results emerged in detail to assess the effects of different parameters on buckling of structure. For instance, it is revealed that the highest and lowest critical buckling load and consequently stiffness, is due to the V–A and A–V CNTs dispersion type, respectively. Furthermore, it is revealed that by porosity coefficient enhancement, critical buckling load and consequently, stiffness are reduced dramatically. Current paper outcomes can be used in different fields of sciences such as optimum design of engineering structures or various high-tech industries as aerospace factories. [ABSTRACT FROM AUTHOR]

This study concerns several possible ways of computing the J-integral in the cases of laminated composite plate structures containing delamination. On the one hand, two special types of plate finite element families are provided for advanced fracture mechanical analyses. On the other hand, a numerical algorithm is introduced also that utilizes results derived from solid element models built in commercial finite element software. In order to create plate elements, the first-order (FSDT) and the third-order shear deformation theories (TSDT) are applied with two equivalent single layers. A subparametric element family is created by using the Hermite interpolation with the FSDT that grants the continuity of the derivatives at the element borders. Besides, an isoparametric family is created also with the TSDT employing the Lagrange interpolation scheme. This paper aims to present the compact formulations of calculating the J-integral around the delamination fronts for both plate element families. The calculation of the J-integral is implemented as a matrix multiplication by taking advantage of the properties of plate transition elements. The models yield improved fracture mechanical analyses for delaminated composite plates with linear elastic material behaviour. In addition, computing the J-integral is not available in most commercial finite element software for laminated orthotropic materials, therefore, an appropriate algorithm is presented here for this purpose. To conclude, the models and algorithms are applied to two case studies and subjected to a comprehensive comparison with analytical and formerly used finite element solutions. • A subparametric FSDT plate element family with granted continuity of the derivatives for delaminated plates. • An isoparametric TSDT plate element family that is appropriate for modelling curved delamination fronts. • A robust algorithm for computing the J-integral numerically in solid element models. [ABSTRACT FROM AUTHOR]

This paper develops a new homogenization method for free vibration problems of periodic composite plates. In this new method, three-dimensional (3D) periodic plates are equivalent to Reissner–Mindlin plates with both effective stiffnesses and effective inertia coefficients. The effective stiffnesses for the dynamic problems are the same as those for the static problems, and they can be achieved by the equivalence principle of macro- and microscopic internal virtual work. To fully take the inertia effects into account, the effective inertia coefficients including the effective translational, translational–rotational and rotational inertias are determined by the two-scale equivalence principle of kinetic energies under three rigid modes. In addition, cell size effects in the thickness direction of composite plates are investigated by using the proposed method and the asymptotic homogenization method (AHM). Numerical experiments validate the effectiveness of the proposed equivalent method for different scale factors, and show that the rotational inertia cannot be ignored for out-of-plane deformations, especially for higher-order modes. Besides, numerical comparisons show that the cell size effects are not negligible when using the AHM to analyze the out-of-plane deformations, and three or more repeated unit cells in the thickness direction are required to ensure accuracy. [ABSTRACT FROM AUTHOR]

Numerical and experimental research programs have been carried out to investigate the effect of scaling on the tensile strength of notched composites. This paper presents a computational study of scaled open-hole tensile tests using the Discrete Ply Model (DPM) method. This finite element model is discrete, and only a small number of parameters are required from experimental characterization tests. Experimental and numerical strength values are compared here, and reveal that DPM simulations tend to slightly overestimate strength values, with an average discrepancy of 9.7%. However, DPM Results show that such modeling simulates both the reduction in strength when specimen size is increased for sublaminate level scaled specimens, where failure is fiber dominated, and the increase in strength when specimen size is increased for ply level scaled specimens, where failure is delamination dominated. In all cases, increasing the total thickness of the specimen leads to a decrease in strength and this effect is dominant over the effect of increasing hole diameter. As well as the variation in strength, three distinct failure mechanisms are observed: fiber failure with extensive matrix damage (pull-out failure), fiber failure with little or no matrix damage (brittle failure) and delamination failure. Comparisons with experiments demonstrate that tensile strengths, damage propagation scenarios and failure patterns are predicted with acceptable accuracy. [ABSTRACT FROM AUTHOR]

Contact delamination damage easily occurs inside the composite. The extension and accumulation of the damage occupy most of the time from damage appearance to failure. However, the anisotropy of materials and the small size of early damage make accurate detection difficult. In this paper, a non-elliptical probability imaging (NEPI) method based on nonlinear ultrasonic guided waves is proposed for the delamination damage detection in anisotropic composites. Firstly, the anisotropic characteristics of the composite are analyzed theoretically, and the velocity in all directions is obtained by numerical simulation. Secondly, the arrival time is obtained by the intersection of the upper and lower envelope fitting lines, and nonlinear coefficient is calculated based on the smooth pseudo Wigner–Ville distribution (SPWVD). Then, the time coefficient (C T) and nonlinear damage index (NDI) are defined and applied in the NEPI. By comparison with a reference point, the problem that the damage location of anisotropic composite cannot be solved analytically is avoided skillfully. Finally, the NEPI method is used to present the damage. The experiment results show that the NEPI method can accurately display the damage location. The sensitivity and reliability of NDI based on SPWVD are further verified by comparison with damage index of scattered signal and time–frequency analysis methods such as fast Fourier transform, short-time Fourier transform, and S-transform. The proposed NEPI method based on nonlinear ultrasonic guided waves can detect the delamination damage with good location accuracy and high damage sensitivity. [ABSTRACT FROM AUTHOR]

Due to their simplification and efficiency, five-variable higher-order models have been widely developed for static and dynamic analysis of multilayered composite and sandwich plates. Nevertheless, the existing five-variable higher-order models will encounter difficulty to produce accurately natural frequencies of sandwich plates. Thereby, this paper proposes a five-variable sine-type higher-order model, which can predict reasonably natural frequencies of sandwich plates. To broaden the scope of application, the finite element formulation in the light of the proposed model is presented. In order to verify the reliability of the proposed model, experiments including two groups of samples have been carried out to test natural frequencies of sandwich plates with diverse holes. After the proposed model is evaluated by experiments, natural frequencies of sandwich plates with different boundary conditions and cutout shapes have been investigated in detail by utilizing the proposed model, which will be further assessed by employing the three-dimensional finite element method (3D-FEM). In addition, the typical five-variable higher-order models published from 1980s to 2020s have been also selected to assess the proposed model. Numerical results show that the proposed model can yield more accurate results than the previous five-variable models. Furthermore, variation of natural frequencies of sandwich plates is also explored by changing the material properties of face sheets, which can provide a consultation for design of dynamic characteristics of sandwich plates. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Natural Fibers is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the first attempt has been made to investigate the performance of the active constrained layer damping system in the thermal environment. For such investigation, a skew laminated composite sandwich plate with carbon nanotube-reinforced composite core is considered. The nonlinear strain-displacement relations are employed to generate the initial-stress stiffness matrix and the mechanical stiffness matrices using linear strain-displacement relations. The negative velocity feedback control-law is used to control the first few modes of the vibrating sandwich plate. Comprehensive investigation has been carried out to understand influence of geometric and material parameters on the damping performance of the system. [ABSTRACT FROM AUTHOR]

This paper proposed a virtual testing method combining finite element procedure with heterogeneity weak bonding model to analyze the macroscopic responses of composite plates. Results show that weak bonding can induce out-of-plane displacement fluctuation when plates subjected to tension or shearing loads. However, it is less sensitive to transverse load. Further, much more distorted displacement map means more serious weak bonding interface. The fluctuated displacements can be used to measure and evaluate weak bonding under some specified loading modes. Since the computational framework considers the heterogeneity weak bonding, the statistical characteristics of results can be obtained by multiple computations. [ABSTRACT FROM AUTHOR]

In this paper, we present the dispersion relation of Lamb waves propagating along one-dimensional phononic and along nesting Fibonacci superlattices, using the plane wave expansion and stiffness matrix methods. More band gaps of Lamb wave appear in nesting Fibonacci superlattices plates than in phononic composite plates. Effect of substrate on band gap structures of nesting Fibonacci composite model is analyzed. In addition, the influence of widths of the materials' strips on the band structure is discussed. Finds could be relevant to understand the intrinsic physical properties of quasi-periodic composites piezoelectric and provide flexible choices to meet real engineering applications. [ABSTRACT FROM AUTHOR]

In this paper, wave propagation in multi-scale hybrid glass fiber (GF)/carbon nanotube (CNT)/polymer nanocomposite plates is studied for the first time by means of refined higher-order plate theory. The hybrid nanocomposite consists of CNTs and glass fibers (GF) as reinforcing components distributed within a polymeric matrix. A hierarchical micromechanical approach is used to predict the effective mechanical properties of the hybrid nanocomposite, including the three-dimensional (3D) Mori-Tanaka method and the rule of mixture. Moreover, a refined-type higher-order shear deformation theory (HSDT) is implemented to take into account the influence of the shear deformation on the motion equations of the system. Then, the governing equations are achieved on the basis of the energy-based Hamilton's principle. Finally, the derived equations will be solved analytically for the purpose of extracting the natural frequency of the continuous system. A set of numerical examples are provided to cover the effects of various parameters on the wave dispersion characteristics of the plate. It can be declared that the hybrid nanocomposite system can achieve higher wave frequencies compared with other types of composite structures. Additionally, it is found that the selection of the lay-ups and length-to-diameter ratio plays a significant role in the determination of the sandwich plate's acoustic response. [ABSTRACT FROM AUTHOR]

This paper develops a two-scale asymptotic homogenization method for periodic composite Kirchhoff plates. In this method, a three-dimensional (3D) periodic plate problem is simplified as a Kirchhoff plate problem, which is governed by a fourth-order uniformly elliptic partial differential equation (PDE) with periodically oscillating coefficients. Then, a two-scale solution in an asymptotic expansion form is presented for the PDE, and it is found that the first-order perturbed displacement in the asymptotic solution is zero. Additionally, periodic boundary and normalization constraint conditions are proposed to determine the unique solution to unit cell problems. Moreover, standard finite element formulations for calculating the perturbed displacements are derived from the principle of virtual work. Physical interpretations of the influence functions are presented by analyzing the properties of self-balanced quasi-load vectors used for solving the influence functions. Numerical comparisons show that the present method is physically acceptable and highly accurate. [ABSTRACT FROM AUTHOR]

This paper presents an analytical investigation on postbuckling behavior of thin plates reinforced by carbon nanotubes (CNTs) and subjected to nonuniform thermal loads. Unlike many previous works considered ideal case of thermal load is that uniform temperature rise, the present study considers more practical situations of thermal load are that sinusoidal and linear in-plane temperature distributions. CNTs are reinforced into matrix through functionally graded distributions and effective properties of nanocomposite are estimated according to extended rule of mixture. Basic equations are based on classical plate theory taking into account Von Karman nonlinearity, initial geometrical imperfection, interactive pressure from elastic foundations and elasticity of tangential constraints of simply supported boundary edges. Basic equations are solved by using analytical solutions and Galerkin method. From the obtained closed-form relations, thermal buckling and postbuckling behavior of nanocomposite plates are analyzed through numerical examples. [ABSTRACT FROM AUTHOR]

Based on Umansky's second theory, this paper studies the torsional stress of an improved composite box girder with corrugated steel webs and considers the effective elastic modulus of the converted section. The calculation formulas of the torsional stress of a single-box multi-cell-improved composite box girder with corrugated steel webs were derived, the initial parameter solution of the generalized displacement and internal force under the restrained torsion were obtained through a model test and finite element simulation, the correctness of the theoretical formulas were verified, the distribution forms of the torsional stress on the box girder section were analyzed, and the effects of the height/width ratio, the width ratio of the cantilever plate, and the thickness of the bottom steel flange on the torsional stress were studied. The results show that the theoretical values and finite element values are in good agreement with the measured values for the torsional stress at each measuring point, and the errors are within 10%. The torsional normal stress of the bottom steel flange of the box girder is much greater than that of the top concrete flange, and the corrugated steel web hardly bears the torsional normal stress. The total shear stress of the box girder is mainly borne by the corrugated steel web on both sides and the bottom steel flange and less by the top concrete flange. The greater height/width ratio, the greater the difference between the torsional normal stress of the bottom steel flange and the top concrete flange. For a box girder with small height/width ratio, the total shear stress of each plate is significantly greater than that of a box girder with large height/width ratio. [ABSTRACT FROM AUTHOR]

This paper uses ANSYS Workbench platform to simulate the casting and rolling composite process, taking the horizontal type casting and rolling machine as the research object, and conducts the numerical simulation study of copper-aluminum composite solid-liquid casting and rolling heat-flow coupling, mainly to study different walking speed, aluminum pouring temperature, casting and rolling zone length, heat transfer coefficient on the temperature field, liquid phase rate influence law, and use it as a theoretical guide for copper-aluminum solid-liquid casting. The experiments of copper-aluminum solid-liquid casting-rolling composite were carried out to optimize the process parameters and to verify the experiments, so as to prepare a well-bonded copper-aluminum composite plate. The composite mechanism in the preparation of copper-aluminum composite plate was analyzed, and it was clarified that the interfacial layer was formed through four stages: contact between copper and aluminum surfaces, contact surface activation, mutual diffusion of copper and aluminum atoms, and reaction diffusion. [ABSTRACT FROM AUTHOR]

This paper presents a numerical method for simulating the crack propagation in functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates. The numerical method is based on 2-D natural element method (NEM) which can overcome the inherent demerits of FEM and conventional meshfree methods. The 3-D displacement field of cracked orthotropic plate is formulated using the (1, 1, 0)* hierarchical model and approximated by 2-D NEM. The thickness-wise mixed-mode stress intensity factors (SIFs) are computed using the modified interaction integral I(1,2) and the 2-D complex-valued crack-tip singular fields. The crack propagation angle is determined by the modified maximum circumferential stress (MCS) criterion, and the crack trajectories are predicted by an incremental crack propagation simulation scheme. The present numerical method is verified from the comparison of predicted crack trajectories with the published reference solutions. Moreover, using the developed numerical method, the crack trajectory characteristics of FG-CNTRC plates are parametrically investigated with respect to the major parameters. From the parametric investigation, it is found that the crack trajectories of FG-CNTRC are significantly influenced by the material orientation angle and the stiffness ratio. But, the effects of the initial crack angle and the volume fraction and volume fraction pattern of CNTs are not remarkable. [ABSTRACT FROM AUTHOR]

Metallic glasses (MGs) have excellent properties, such as high strength and low elastic modulus, can be used as reinforcement in metal matrix composites. In this paper, aluminum matrix composites reinforced with Fe80Si9B11 MG strips with different weight contents (5, 10, 15, 20 and 25%) were produced by roll-bonding at an initial temperature of 450 °C and 80% deformation. Tensile mechanical tests showed that the tensile strength of the composite sheets containing 10% MG strips showed the highest tensile strength of 166 MPa. Further studies on the sandwich structured samples were conducted using high-pressure torsion (HPT) technology with various pressures of 0.55 GPa, 1.10 GPa, 1.65 GPa, and 2.20 GPa. X-ray diffractometry (XRD), scanning electron microscopy (SEM), TriboIndenter nanomechanical testing, and transmission electron microscopy (TEM) were used to study the microstructures, mechanical properties and the bonding interface of the material. The results show that the hardness near the interface presented a transition area. High-resolution TEM observation showed that physical metallurgical bonding can be achieved between MG and aluminum alloy. A preliminary fitting of metallurgical bonding conditions was carried out according to the experimental parameters of HPT and the interface bonding condition in this study. [ABSTRACT FROM AUTHOR]

Based on Gurtin–Murdoch's theory, a new mechanistic laminated nanoplate model composed of nanocomposites under various boundary conditions is proposed, where the top and bottom surfaces of the laminated nanoplate are regarded as two-dimensional films which have independent surface elastic parameters. The influence of surface Lamé constants and residual stress on static bending and vibration properties for the laminated nanoplate is studied. In order to get approximate solutions of bending deflections and first-order frequencies for the laminated nanoplate with complex boundary conditions, the variational method is employed in this paper. The effectiveness of the presented variational method is verified by comparison with available results. Numerical results indicate that the effective bending stiffness of the laminated nanoplate considering surface effects is obviously different from the classical result. Moreover, the influences of surface effects on bending deflections and first-order frequencies are related to the surface elastic parameters and boundary conditions. The presented method and results provide a theoretical benchmark for other numerical and experimental methods to study nano laminates. [ABSTRACT FROM AUTHOR]

The RAPID (reconstruction algorithm for probabilistic inspection of defect) method based on Lamb wave detection is an effective method to give the position information of a defect in composite plate. In this paper, an improved RAPID imaging method based on machine learning (ML) is proposed to precisely visualize the location and features of defects in composite plate. First, the specific feature information of the defect, such as type, size and direction, can be identified by analyzing the detection signals through multiple machine learning models. Then, according to the obtained defect features, the scaling parameter β of the RAPID method which controls the size of the elliptical area is revised, and weights are set to the important detection paths which are related to defect features to realize precise defect imaging. The simulation results show that the proposed method can intuitively characterize the location and related feature information of the defect, and effectively improve the accuracy of defect imaging. [ABSTRACT FROM AUTHOR]

This paper introduced the triangulation method using the relations of the signal magnitudes and distances between each sensor and impact location. In order to extract the useful feature having good correlation with these distances, the time of arrival (TOA) data of sensor signal was applied. Using the signal magnitudes and TOA data, the effective features could be derived for estimating the distances between each sensor and impact location. For investigating this suggested algorithm, low-velocity impact experiments were carried out on the composite stiffened plate as a target structure. The acoustic emission signals were captured by the commercial high-speed optical fiber sensing system. From the impact signals on the baseline locations (30 points), the regression model was constructed for estimating the distances of impact location from each sensor on the target area. Then, through the non-baseline signals (20 points), the validations of constructed regression model were performed. As a result, this regression model is able to accurately predict the AE source locations on the non-baseline cases. [ABSTRACT FROM AUTHOR]

In this paper, free and forced vibration analysis of multi-layered functionally graded composite cylindrical panels reinforced by single wall carbon nanotubes is presented. The panel is composed of different layers which are reinforced using carbon nanotubes arranged in arbitrary directions. Reddy's third-order shear deformation theory is used which makes results more accurate especially for thick panels. The set of governing equations and boundary conditions is derived using Hamilton's principle and is solved numerically using generalized differential quadrature method and Newmark beta method. Convergence and accuracy of the presented solution are confirmed and effect of volume fraction, distribution and orientation of carbon nanotubes and geometrical parameters on the natural frequencies of the panel are investigated for different boundary conditions. Also, effect of volume fraction and orientation of carbon nanotubes on the dynamic response of the panel are investigated. Result of this paper can be considered as a useful tool in dynamic analysis of multilayer carbon nanotube-reinforced structures. [ABSTRACT FROM AUTHOR]

This paper presents a novel methodology to minimize the weight of a composite plate, taking into account both its structural integrity and its manufacturing constraints. This optimization problem has been abstracted, and reduced to, a graph problem where finding the optimum is equivalent to finding the shortest path in the graph. This graph is an implicit ternary decision tree and path finding is accomplished with a parallelized breadth-first search procedure. As a result of this search, the procedure is able to provide both a global optimum and a Pareto front. The implementation of an implicit decision tree as a way to optimize a laminate stacking sequence is a novel idea, in spite that both issues have been tackled in numerous publications separately. Its benefits are clearly stated in this work. [ABSTRACT FROM AUTHOR]

Summary: Composite plate shear walls‐concrete encased (C‐PSW/CE), consisting of the steel plates and concrete encasements on one or both sides of the plate, are an excellent lateral force resisting system. This paper theoretically and numerically reveals the shear resisting mechanism of C‐PSW/CE under cyclic loading. The steel web resists the lateral force through in‐plane shear before buckling, and the concrete encasements resist lateral force by diagonal compression field action. As the displacement increases, the shear force ratio of the steel web plate increases before yielding in shear and that of concrete encasements reduces. The shear force ratios of the steel web plate and concrete encasements remain essentially constant after yielding of the steel web. Considering the shear contribution of the concrete encasements, the formula is proposed to evaluate the shear capacity of C‐PSW/CE. Based on the principle of virtual work, the equation is proposed to predict the lateral stiffness of C‐PSW/CE under cyclic loading, accounting for the concrete deterioration due to cyclic effect. [ABSTRACT FROM AUTHOR]