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In view of the increasingly prominent noise problem, more and more attention has been paid to the research of sound insulation materials and structures. This paper takes aluminum foam laminated structural plate as the research object. The numerical model of sound insulation was derived using equivalent parameter method, and the sound insulation performance of aluminum foam composite structural plate was tested using a standing wave tube. The experimental results show that the transfer loss of aluminum foam composite structure with 5 mm and 10 mm core layer thickness is increased by 10 dB and 17 dB on average compared with ordinary base aluminum plate. The calculated results of transfer loss in effective range are in good agreement with the experimental results. The error is only 2–5 dB at low frequencies. At the high-frequency stage, although the error increases slightly, the overall trend of the two changes is consistent. The degree of coincidence increases with the increase of frequency. It provides an important theoretical basis for the research direction of sound insulation theoretical model of aluminum foam laminated structure, and also lays a foundation for the optimization of subsequent mathematical model. [ABSTRACT FROM AUTHOR]

Purpose: It is very important to identify the material parameters of composites efficiently and accurately for the dynamic analysis and response prediction of composite structures. In this paper, a high-precision and efficient multi parameter synchronous identification method is proposed for fiber reinforced laminates. Methods: Based on the first-order shear theory and considering the influence of fiber angle, the constitutive model of fiber reinforced laminated composite in any direction is established by using energy method. The model includes four mechanical parameters in a single plane to accurately obtain the anisotropic material parameters. To ensure the accuracy of identification and further accelerate the convergence speed, the Levenberg Marquardt optimization algorithm is innovatively improved, that is, the decision principles of the iterative step and search range are proposed. A detailed parameter identification procedure is proposed, which can identify the four anisotropic parameters once from the modal data of composite plates. Results: Based on experimental tests, the identification method proposed in this paper is used to identify the anisotropic material parameters of laminated composite plates with orthogonal laminated structure and needle structure. Then, the identification process and results of this method are compared with those of the Genetic Algorithm, which verify the accuracy and efficiency of this identification method. Finally, the influences of fiber angle and boundary conditions on the natural frequency are analyzed theoretically. Conclusion: The identification efficiency was doubled that compared with the Genetic Algorithm. The parameter identification method proposed has a good application prospect for other types of composite materials. [ABSTRACT FROM AUTHOR]

Purpose: This work investigates the free vibration response of functionally graded (FG) nanocomposite laminated plates in thermal environments. The nanocomposite plies consist of a polymer matrix strengthened by nano-scale reinforcements, namely a graphene monolayer. This is a case of matrix/graphene mixture or in other words graphene-reinforced nanocomposite (GRNC). Besides the uniform distribution pattern of the graphene reinforcements, four piece-wise FG patterns are also considered to find out the best way to reinforce the nanocomposite plates. The FG distribution patterns are structured by varying the amount of the graphene nano-reinforcements from ply to ply. Methods: Material properties corresponding to the homogenization mixture are carried out using the extended Halpin-Tsai approach. Material properties of the GRNC plies are considered to be either temperature-dependent or temperature-independent. The governing equations of the laminated plate structure are derived based on the first-order shear deformation plate theory (FSDT). The validity of the internal computer program, developed using the finite element method (FEM), is examined by comparing the results obtained in this investigation with those reported in the open literature. Numerical analysis illustrates the effects of a broad range of influencing parameters on the mode shapes and associated natural frequencies of GRNC laminated plates when subjected to varying temperature fields. Results: Numerical results state that the free vibration behavior of the GRNC laminated plates is strongly affected by the variation of the environmental temperature as well as by the geometric parameters. In this context, considering the noteworthy results achieved in this paper, new ideas are proposed to offer innovative insights and novel design models for future real-life applications in polymeric nanocomposite structures. [ABSTRACT FROM AUTHOR]

Purpose: In this paper, the free vibration and dynamic response of laminated composite wave plate in a thermal environment are investigated by means of the mesh-free strong form method. Method: The wave plate is divided into several rectangular and cylindrical segments, and each segment is transformed into a square domain or equivalent cylindrical rectangular domain through a coordinate mapping technique to ensure numerical stability. The theoretical formulation of the individual segment is established using Hamilton's principle in the framework of first-order shear deformation theory (FSDT), and the thermal effects on the wave plate are considered by employing the thermo-elastic theory. The discretized equations are obtained directly from the strong forms of governing equations in which displacement components are approximated by a mes-hfree Tchebychev-radial point interpolation method (TRPIM) shape function. The formulation of the entire wave plate is obtained using coupling conditions between the segments. The harmonic distributed load and stationary/nonstationary stochastic excitation are considered as the external force. Results: Convergence and verification studies are performed to confirm the reliability and accuracy of the present formulation. Satisfactory agreements are achieved between the numerical results of the proposed method and those from the published literature. Finally, the effect of some parameters on the free vibration and dynamic response of laminated composite wave plate is presented. [ABSTRACT FROM AUTHOR]

Purpose: The main purpose of this paper is to detect the damage of interior delamination in composite laminate using a new non-destructive testing method of highly nonlinear solitary waves. We studied the coupling mechanism between highly nonlinear solitary waves and interior delamination composite plate. Methods: The discrete element method is used for the one-dimensional particle chain, based on the residual stiffness model, Hertz's contact law and the composite plate vibration differential equation are used, we obtained the coupled differential equations for one-dimensional particle chain and interior delamination composite plate. We used the fourth-order Runge–Kutta method to solve the differential equations, and obtained the velocity curve and displacement curve of each particle in the particle chain. The influence of the thickness of the damaged composite plate, the average diameter of the interlaminar cracks, and the density of the interlaminar cracks on the reflected solitary waves are analyzed. We used one-dimensional homogeneous particle chain and one-dimensional composite particle chain to detect damaged composite plate with different material properties. Results: The results shows that the reflected waves are sensitive to the thickness of the plate, the average diameter of the interlaminar cracks and the density of the interlaminar cracks. We find that the propagation time of solitary waves in the composite particle chain is shorter and faster, and the detection efficiency can be increased by 23.5% at most. Conclusions: The characteristic information carried by reflected waves can be used for non-destructive testing of damaged composite plate. The research results of this paper enrich and improve the non-destructive testing of composite materials, and accelerate the practical application of one-dimensional particle chain. [ABSTRACT FROM AUTHOR]

Purpose: The vibration energy transmission characteristics of laminated composite plates with straight or variable angle fiber paths subjected to distributed force excitations are explored in this paper. Methods: The dynamic responses as a function of frequency are calculated and evaluated using proposed analytical approach and numerical finite element (FE) method based on the first-order shear deformation theory. The FE model is firstly verified by the analytical method and used for the composite plates with various fiber paths. The FE-based structural intensities analysis is carried out to predict the energy transmission and distribution patterns on the laminated composite plates with various fiber paths. Results: The structural intensity streamlines and vectors representation explicitly offer the information of the energy sources, energy sinks and detailed vibration energy distribution and transmission paths. The fiber paths have significant influences on the dynamic responses and energy transmission paths. The results reveal that tailoring fiber paths could lead to the formation of vortex-type flows with low vibration levels. Conclusion: According to the structural intensity fields at the specific excitation frequencies, the tailorable fibers in the forced area or unforced area and curvilinear fibers could be tuned for vibration mitigation. [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]

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]

Purpose: This paper aims to investigate the free vibration behavior of laminated composite doubly curved shells of revolution with varying thickness employing an efficient numerical method based on the Haar wavelet discretization method (HWDM). Method: The thickness of the shell is changed along the meridional direction. The theoretical analysis model is formulated by applying of the first-order shear deformation theory (FSDT). The displacement and rotating components of any point of the shell are expanded in the form of the Haar wavelet series in the meridional direction and the Fourier series in the circumferential direction. The constants produced from the integration of the Haar wavelet series are satisfied by the boundary condition. Then, the free vibration results of the shell are directly obtained by solving the governing equation. Results: The results of the present method are compared with those of published literature. The comparison results indicate that HWDM has high accuracy and convergence for the free vibration analysis of laminated composite doubly curved shells of revolution with varying thickness. Lastly, taking into account the effects of boundary conditions, material properties, thickness profile and geometric parameters for the laminated composite doubly curved shells with varying thickness, new free vibration results are provided which can be used as reference results for further studies in this field. [ABSTRACT FROM AUTHOR]

Purpose: Although damage's location detection by Wavelet Transforms (WTs) is quantitive, damage's level detection is qualitative. It is a weakness of wavelet transform that cannot detect the level of damages quantitatively. For overcoming this weakness, this paper proposes a novel robust approach for quantifying the damage level of rectangular laminated composite plates using a combination of wavelet transforms and Artificial Neural Networks (WT-ANN). Methods: The finite element method generates two-dimensional signals of vibration amplitudes in the rectangular laminated composite plates. Next, a two-dimensional WTs is applied to the signals to generate wavelet coefficients and wavelet modulus. An artificial neural network is developed to quantify damage's level based on damage locations detected by wavelet transform and fundamental natural frequency. Results: Findings demonstrate that it is possible to quantify damages in rectangular laminated composite plates with high accuracy (R = 0.992). A disturbing phenomenon in damage identification techniques based on wavelet transform is discovered and called "edge noise". Conclusion: Results show that the proposed WT-ANN technique can detect all single-damage scenarios with very high accuracy by eliminating edge noises. [ABSTRACT FROM AUTHOR]

Purpose: Three-dimensional thermal vibration analysis of functionally graded carbon nanotube (FG-CNT) reinforcement composite plates is performed for uniform, linear and sinusoidally temperature distribution. Methods: The reinforcement directions is considered through the thickness according to four reinforcement models as UD, FG-V, FG-O and FG-X are examined. As the components of the composite, the material properties of both the CNT forming the reinforcement phase and the polymer forming the matrix phase change depending on the temperature, and this is the focus of this study. The effective material properties of the FG-CNT reinforced composite are determined by the mixtures rule. The three displacements of the plates are expanded by a series of Chebyshev polynomials multiplied by appropriate functions to satisfy the essential boundary conditions. The natural frequencies are obtained by the Ritz method. Results: It is shown that the numerical results of the current approach are compared with the results of other researchers for validation, the results appear to be in good agreement. The effects of the thickness-to-length ratio and different volume fraction distributions for cantilever (CFFF) boundary conditions in considered thermal environments are investigated. The effect of different boundary conditions such as clamped (CCCC), simply supported (SSSS), simply supported through the x-axis and clamped through the y-axis (SCSC) and simply supported through the x-axis and free through the y-axis (SFSF) is also examined. It is shown that the increase in the amount of temperature and the type of temperature distribution are effective on the decrease of frequencies. [ABSTRACT FROM AUTHOR]

Purpose: In comparison to traditional, constant stiffness laminates, variable stiffness composite laminates (VSCL) with curvilinear fibres represent an extra analysis effort. It is the purpose of this work to present and test a relatively simple optimisation procedure, in order to find the maximum fundamental frequency of vibration in bending and in in-plane vibrations. It is also intended to explain why certain fibre paths lead to higher frequencies. Methods: The optimisation is performed using a genetic algorithm (GA), which is described in detail. The bending and the in-plane plate models are based on the p-version Finite Element Method. Each model requires a small number of degrees of freedom, an important feature because applying the GA involves the solution of a large number of eigenvalue problems. In order to support the physical interpretation of the optimal designs, mode shapes and stress fields corresponding to some optimal solutions are illustrated. Results: Single- and multi-layer plates with different boundary conditions and fibre path types are studied. Fibre paths that lead to maximum fundamental frequencies are found and justified. The consequences that maximising the first frequency has on the higher-order modes of vibration are studied. Conclusion: The proposed optimisation and modelling methods are effective. Curvilinear fibres with the characteristics considered led to the maximum first natural frequency of vibration in a few cases, but not all. Particularly in in-plane vibrations, curvilinear fibres can provide major gains in comparison to straight fibres. The increase in the vibration frequency is accompanied by, overall, larger stresses. [ABSTRACT FROM AUTHOR]

The modal testing and numerical results on free vibration behavior of completely free woven fiber glass/epoxy-laminated composite shallow shell panels are presented in this investigation. The finite element numerical model is established by a doubly curved shell model on the basic of first-order shear deformation theory (FSDT). Vibration study of the composite shell panels is carried out using a quadratic eight-noded isoparametric element. The modal testing experiments are carried out using FFT analyzer with PULSE software to determine natural frequencies of woven fabric glass/epoxy composite cylindrical shell panels under free–free boundary condition. The first four natural frequencies of completely free woven fabric glass/epoxy laminated cylindrical shell panels are obtained for different curvature ratios, sequences of lamination and number of laminate layers. The modal test values illustrate an excellent concurrence with the numerical values and will serve as bench mark for future investigators in the present area. [ABSTRACT FROM AUTHOR]

Purpose: The current analytical study is devoted to examining the nonlinear free vibration behavior of the laminated nanocomposite cylindrical shells containing multi-scale hybrid reinforcements once a nonlinear three-parameter substrate surrounds the structures. The multi-phase material of the structures includes polymeric matrix, nano-scale GOPs, which are uniformly distributed through the thickness of each layer and macro-scale carbon fibers with various orientation angles. Methods: The effective material properties of each multi-phase nanocomposite layer are calculated by implementing the modified Halpin–Tsai micromechanical scheme together with the extended rule of the mixture in a hierarchy. After that, with an incorporation of the improved Donnell's shell theory and Hamilton's principle, the governing equations are derived. Then by adopting a two-step solution technique, these nonlinear equations are transferred to one ordinary differential equation via Galerkins' method, and in the next step, the nonlinear frequencies of the structure are obtained by employing the multiple scale technique. Results: In the framework of various graphical results, a parametric analysis is conducted in detail to reveal the influences of the different parameters such as nonlinear foundation parameters, carbon fibers' orientation angles, GOPs' weight, and carbon fibers' volume fractions and length-to-radius ratios on the nonlinear vibration characteristics of the multi-phase laminated nanocomposite cylindrical shell. Conclusions: The results declare that the addition of the GO nanofillers along with the CFs and also embedding the structure on the nonlinear substrate can significantly enhance the vibrational behavior of the multi-phase laminated nanocomposite cylindrical shell. [ABSTRACT FROM AUTHOR]

Modeling and Methods: This work is devoted to the numerical dynamic bending characterization of delaminated multi-walled carbon nanotubes (MWCNTs) reinforced epoxy/glass fiber-based hybrid composite plate based on finite element method with displacement fields derived from classical laminated plate theory (CLPT). Verification: The accuracy and performance of the developed method were confirmed by a validation study with reference solutions available in the literature. Results: Various parametric studies were carried out to study the influence of MWCNTs content, delamination location, delamination interface, ply orientation, and end condition on the dynamic bending characteristics of the intact and delaminated hybrid laminated composite plate. Conclusion: The weight fraction of MWCNTs, delamination location, and clamping condition significantly influences the natural frequency. The natural frequencies also depended upon the ply configuration and delamination interface irrespective of the MWCNT loadings. However, anomalous trends were observed as far as the influence of end conditions is concerned. [ABSTRACT FROM AUTHOR]

Introduction: Autonomous shape and vibration control of a structure expand its utility, thereby increasing the need for adaptive composites in the field of aerodynamics, civil, space, and mechanical engineering. One way to achieve this is by reinforcing composites with smart materials like shape memory alloy (SMA) wires or ribbons, piezoelectric (PZT) materials, and magnetostrictive materials. Objectives: In this study, the authors optimize the numerically solved bending behavior of SMA fiber-reinforced E-glass fiber-Silicone matrix composite upon thermal actuation. The study is shown for four cases (a) single layer of SMA embedded unimorph, (b) two-layers of SMA embedded bimorph, (c) single layer SMA embedded bimorph with a honeycomb core, and (d) single layer SMA embedded bimorph with an auxetic core. The vibration responses of these cases upon analysis show that the first three eigenmodes of the unimorph and the bimorph SMA composite include bending and torsion modes and the corresponding eigenfrequencies are significantly close in magnitude for the Austenite finish ( A f ) temperature. In other words, the first natural frequency displays complex eigenmodes. A multi-objective optimization approach for SMA hybrid composite plates for de-coupling eigenfrequencies is proposed in this study. Methods: The Non-dominated Sorting Genetic Algorithm (NSGA-II) is used to minimize the eigenfrequency corresponding to the first bending eigenmode and maximize the eigenfrequency corresponding to the first twisting eigenmode, thus increasing the effective difference between the two eigenfrequencies. The authors also simultaneously maximize the deflection of the structures in order to obtain a considerable morphing observation. The present investigations involve determining the best laminate configuration relying on SMA fiber angle orientation and SMA ply thickness as the variables. Results: A complex mode or a combination of two modes at the first eigenfrequency or complex modes can cause failure of the structure, making decoupling an essential requirement. The algorithm proposed can also be used to interchange the eigenmodes of their corresponding eigenfrequencies, thus allowing the first natural frequency to give a twisting or torsional eigenmode and the consecutive natural frequency that of a bending mode. This technique can be used to avoid Phugoid motion-based failure in an aircraft by continuously controlling and interchanging the eigenmodes of its wings. [ABSTRACT FROM AUTHOR]