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This paper investigates the performance of several meta-heuristic algorithms, including Particle Swarm Optimisation (PSO), different variants of Differential Evolution (DE), Biogeography-Based Optimisation (BBO), Cultural Algorithm (CA), Optics-Inspired Optimisation (OIO), and League Championship Algorithm (LCA), for optimum layup of laminated composite plates. The study provides detailed Pseudo codes for different algorithms. The buckling capacity maximisation of a 64-layer laminated composite plate under various load scenarios has been considered as the benchmark problem, in which the design variables are the stacking sequences of layers. A Deep Statistical Comparison (DSC) method is employed to rank the performance of different algorithms. The DSC uses a nonparametric two-sample Kolmogorov-Smirnov test to conduct the performance comparisons between the algorithms. The overall performance rankings obtained from the DSC suggest that the LCA, OIO, and PSO algorithms perform remarkably better in comparison to other algorithms. The comparisons provide some interesting conclusions on the performance of different algorithms. [ABSTRACT FROM AUTHOR]

Aiming at the problem about misjudging sheet fracture in hydroforming process, the different mechanisms between drawing and hydraulic bulging are analyzed. In this paper, a method to test the forming limit diagram (FLD) based on uniform load in thickness direction is adopted by using laminated plate hydroforming, and the quality of hydroforming process is judged more accurately. By the numerical simulation analysis, the shape of the specimen on five different linear paths is preliminarily determined, and the forming limit diagram of the sheet is obtained under the stretch-compression condition. At the same time, the influence of method of lubrication such as non-lubrication, oil, grease, and thin film on FLD is analyzed. The results show that the first principal strain and the second principal strain increase, and the bulging height decreases with the decrease of friction factor. Among them, the friction factor of thin film is reduced to the lowest. In the process of laminated sheet hydroforming, the thin film lubrication between pieces is more relatively accord with the experimental condition of stretch-compression bulging, and the FLD is more reliable to judge the quality of component formed by hydroforming. [ABSTRACT FROM AUTHOR]

The location optimization of sensors is a essential problem in structural health monitoring systems. Taking the cost of sensors into account, it is uneconomical to install sensors on every part of a structure and moreover in aeronautical industry, the weight is a crucial factor. In this paper, a optimal placement optimization of sensor locations for structural health monitoring systems is studied. Several techniques of optimization of sensors are approached and applied in a shell structure. The structure, a laminate of carbon fiber, was modeled by the finite element method (FEM) and then subject to free vibration. Genetic algorithms (GAs) are then employed to locate the best sensor distribution to cover a specific number of low frequency modes. Numerical results have demonstrated the overall efficiency of sensor delivery methods. Specific problems occurred, especially regarding the method of effective independence, being less efficient and discrepant in relation to the other methods employed. In summary, the results obtained in this paper provide an optimal position for sensors in real SHM systems and experiments. [ABSTRACT FROM AUTHOR]

How to improve the bonding ability and quality performance of heterogeneous plates has always been one of the difficult problems in the field of high-performance heterogeneous composite sheet forming and manufacturing. In this paper, a new manufacturing method of heterogeneous clad plate, hard plate rolling clad plate, is proposed. The hot rolling process of Al/Mg/Al composite slab with or without hard plate was studied. The results show that the shear stress in the rolling direction (RD) can be transformed into the compressive stress in the normal direction (ND), and then the welding pressure between different composite layers can be increased. This method can suppress the bending and edge crack defects and significantly improve the shape quality and forming ability. At the same time, through the study of the interface structure of the composite plate, it can be known that the metallurgical bonding can be achieved with a small reduction after adding the hard plate. Two clear layers of Al3Mg2 and Al17Mg12 intermetallic compounds appear at the Al/Mg interface. The thickness of the diffusion layer is significantly larger than that of the traditional hot-rolled clad plate, and the thickness of the diffusion layer can reach 38 μm when the reduction is 60%. The yield strength is 172.3 MPa and the elongation is 21.5%. To sum up, the hot rolling of hard-plate provides a new idea for the forming and manufacturing of high performance heterogeneous composite plate. [ABSTRACT FROM AUTHOR]

Applications of skew plates in the practical civil engineering are well-established. A look into the papers about the failure of laminated composite structural elements revealed that composite skew plates have not been studied for failure in detail. The first-ply failure load and frequency reduction due to such a failure are reported considering practical parametric variations of composite skew plates. Different well-established failure criteria, including the most recent Puck failure criterion, are used to investigate the first-ply failure response by the finite-element method. The results obtained are postprocessed to formulate specific recommendations regarding the relative behavior of different skew plate combinations in terms of the first-ply failure. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical procedure is elaborated based on large deformation, finite element and perturbation methods for thermo-large amplitude analysis of anisotropic laminated and sandwich FGM plates with temperature-dependent properties. Nonlinear thermal dependence distribution following a power law is adapted. Various types of multilayered composite plates with position and temperature-dependent material properties are considered. Mathematical formulations and explicit relationships are presented in the frame of finite element methods. The structure is subjected to linear and uniform temperature variations. The temperature and the displacement are expanded in power series with unknown terms, and the numerical solution is obtained by the finite element method. The homotopy method is used for nonlinear thermal buckling, and a continuation procedure is elaborated for nonlinear thermal–displacement responses. The nonlinear thermal critical buckling load is first computed and the postbuckling equilibrium path of FGM and laminated plates under thermal loading is investigated. Temperature-dependent properties and geometry effects as well as boundary conditions on the nonlinear thermal buckling and postbuckling behaviors are analyzed. [ABSTRACT FROM AUTHOR]

The finite element method is used to develop a computational algorithm for solving a limited class of problems on the bending of composite plates reinforced with systems of unidirectional high-strength fibers. It is assumed that a neutral plane exists in the region of the plate and behaves similarly to a flexible nondeformable membrane. The displacements of the plate in the longitudinal direction are linear in thickness. In the case of fiber composites with different elastic moduli in tension and compression, the neutral plane, generally speaking, does not coincide with the median plane. The problem of minimizing the elastic energy functional in accordance with the Lagrange variational principle yields a fourth-order elliptic differential equation for the deflection. The bending stiffnesses of the plate included in the coefficients of the equation are calculated with account for the fact that the elastic characteristics of the reinforcing fibers under tension and compression are significantly different. The numerical solution of the equation is obtained via the finite element method with the help of a Bell triangular element. The paper presents computational results for the bending of rectangular laminated plates in which the fibers are laid in different directions. [ABSTRACT FROM AUTHOR]

The rock plate (RP) method can be used to identify the size and location of potentially dangerous bed separation space (BSS) in coal mines. The RP method is performed in three steps: (1) The rock strata above the coal seam is simplified as a composite plate calculation model; (2) The deflection of rock strata is expressed as a double trigonometric series and obtained using the energy method; (3) The internal-forces and deformation of the RP are solved to determine the size and location of the BSS based on elasticity and a BSS identification process. This requires that the BSS be unbroken, and the BSS upper rock stratum be an aquifer. In this study, the Yuanzigou coal mine was taken as a study case and the RP method was used to determine the size and location of BSS water (BSS-W) above the coal goaf of working face 1,012,001. BSS usually occurs at the contact surface between hard and soft rock strata; at this mine, BSS-W exists between the Yijun conglomerate and the Anding mudstone formations. The results predicted that when the working face advanced 350 m, the third BSS will break, allowing BSS-W to flood into the goaf. These results were verified by borehole video observation. Therefore, two control methods were used: inclined drainage holes drilled from the roadway and spaced holes drilled from the surface in areas with abundant water. This paper thus provides a way to locate the BSS-W and prevent an inrush hazard. [ABSTRACT FROM AUTHOR]

The NM500/Q345/NM500 composite plates were subjected to different hot rolling and heat treatment processes in this paper. The influence of hot rolling and heat treatment on the microstructure, element distribution and defect composition of the bonding interface of the as-rolled clad plates was studied by using optical microscope, scanning electron microscope, electron backscattered diffraction and transmission electron microscope. Meanwhile, the mechanical properties of wear-resistant steel were analyzed by microhardness and tensile tests. It was revealed that the increase in rolling reduction promoted the metallurgical bonding between NM500 and Q345 steels. The composite texture components of {112} ~ {113} < 110 > , {332} < 113 > , {223} < 110 > , {554} < 225 > and < 110 > ∥RD were formed in the tissue when the reduction rate was 70%. γ/α phase transformation reinforced the texture components and thus increased {332} < 113 > and {554} < 225 > after quenching treatment. Typical lath martensites were present in the structure, and there were high-density dislocations and substructures between the laths. Tempering treatment at 200 °C facilitated the deposition of some needle-like or rod-like ε precipitates in the martensite. The best tensile strength (1432.28 MPa) and elongation (22.68%) in the composite plate could be achieved by post-rolling treatment of quenching at 900 °C and tempering at 200 °C. [ABSTRACT FROM AUTHOR]

The paper presents the results from a study of the interaction of Lamb waves with inhomogeneities in composite plates. It was found that waves of this type are diffracted by inhomogeneities, such as hole and localized mass load of the surface. A method for detecting and localizing inhomogeneities by comparing the distribution of the wave field amplitudes over the plate surface before and after the appearance of inhomogeneities is proposed and tested experimentally. The article was prepared based on materials in a report at the Third All-Russian Acoustics Conference (September 21–25, 2020, St. Petersburg). [ABSTRACT FROM AUTHOR]

In this paper, the influence of oxidation of automatic transmission fluids (ATFs) and sliding distance on the friction coefficients of a wet clutch in approached running-in conditions was investigated. The ATFs were oxidized by a laboratory process approaching oxidation occurred in actual ATFs. Oxidation was evaluated by means of increase in carbonyl compounds and depletion of zinc dialkyldithiophosphates (ZDDPs) additives. Also, the changes in kinematic viscosity and viscosity index were evaluated. Pin-on-disk tests were conducted to replicate the actual sliding contact in a wet clutch. The pin specimens were cut from friction material composite plates and the disks were actual steel separators both from an automotive wet clutch. Friction coefficient, μ, was measured at progressive sliding velocity, ν, to obtain μ-ν curves at 26 and 100 ΰC. Three μ-ν tests were consecutively run using the same pair of specimens and oil. The cumulative sliding distance for each μ-ν test generated surface flattening using the oils. The friction coefficients of the wet clutch increased due to the ATFs oxidation meanwhile the dμ/dυ values decreased in most cases. It suggests that ATF oxidation can enhance torque capacity of the wet clutch, but it could reduce anti-shudder property. Progressive sliding distance improved the slopes in the μ-ν results using fresh ATFs meanwhile it generated a slope decrease by using aged ATFs. [ABSTRACT FROM AUTHOR]

This paper aims to conduct the free vibration analysis of single-layer and laminated composite plates with multiple cutouts based on the scaled boundary finite element method (SBFEM) incorporated with the precise integration method (PIM) and the technique of the degree of freedom transform. It is applicable to a variety of shaped plates containing cordiform, circular and other complicated cutouts. The key equations are formulated built on the two-dimensional model, and the discretization is carried out in terms of only three translational displacement components as the basic unknowns. The high-order spectral elements are applied in the proposed technique to accurately simulate the arc boundaries of cutouts. Characterized by the important semi-analytical feature of the SBFEM, responses of the transverse free vibration are accurately explored. The derivation of governing equations strictly follows the 3D theory of elasticity without introducing any assumptions. The general solution of the SBFEM key equation is in the form of the matrix exponent, which is calculated by the PIM. As a type of highly precise approach, the PIM is introduced to create the global stiffness matrix from the analytical exponential matrix, which can make sure the eigensolutions with enough accuracy. Aided by the methodology of the kinetic energy formula, the global mass matrix of the perforated plate structure is constructed. According to the thin plates, the degree of freedom transform is employed to lower the dimensions of eigenvalue equation and thus improve the computational efficiency. Numerical examples of flexible square and circular plates with various cutouts reveal that excellent agreement is achieved between the natural frequencies predicted by the developed method and those from other methods and exact solutions. Furthermore, the effect of boundary conditions, skew angles, thickness-to-length ratios and sizes of cutouts on distributions of vibration frequencies is discussed. [ABSTRACT FROM AUTHOR]

It has been a vital issue to ensure both the accuracy and efficiency of computational models for analyzing the ballistic impact response of fiber-reinforced composite plates (FRCP). In this paper, a machine learning (ML) model is established in an effort to bridge the ballistic impact protective performance and the characteristics of microstructure for unidirectional FRCP (UD-FRCP), where the microstructure of the UD-FRCP is characterized by the two-point correlation function. The results showed that the ML model, after trained by 175 cases, could reasonably predict the ballistic impact energy absorption of the UD-FRCP with a maximum error of 13%, indicating that the model can ensure both computational accuracy and efficiency. Besides, the model's critical parameter sensitivities are investigated, and three typical ML algorithms are analyzed, showing that the gradient boosting regression algorithm has the highest accuracy among these algorithms for the ballistic impact problem of UD-FRCP. The study proposes an effective solution for the traditional difficulty of the ballistic impact simulation of composites with both high efficiency and accuracy. [ABSTRACT FROM AUTHOR]

In this paper, a new three-node triangular plate element is proposed to analyze laminated composite plates based on the higher-order shear deformation theory (HSDT). Originating from the MITC3+ shell finite elements, the displacement fields of the HSDT are interpolated by usual linear functions of the three-node triangular element and a cubic supplemented function associated with a node located at the centroid of the element. The transverse shear strain fields are separately approximated according to the MITC3+ shear-locking removal technique. The edge-based smoothed (ES) strain method is employed to improve the in-plane strain fields. Applying the divergence theorem, the surface integration of the in-plane stiffness matrices is transformed into the line integration on the boundary of the smoothing domains. The performance of the so-called ES-MITC3+ plate elements is validated through several numerical examples. The numerical results of the static, frequency and buckling analyses when this new element is used converge to the exact solutions and agree well with those given in other references. [ABSTRACT FROM AUTHOR]

In this paper, the low velocity impact analysis of carbon nanotube (CNT)/carbon fiber (CF)-reinforced hybrid nanocomposite plates is presented using variational differential quadrature (VDQ) method due to its numerical essence and the framework of implementation. The hybrid nanocomposite plate deformation is formulated based on classical plate theory and the contact force between the plate and projectile is estimated using Hertzian contact law. Also, a new micromechanics approach is presented to calculate the effective mechanical properties of the CNT/CF polymer hybrid nanocomposites. Five important factors including, random orientation and random distribution of CNTs, CNT/polymer interphase region, waviness and transversely isotropic behavior of CNT are incorporated in the micromechanical analysis. The accuracy of the present approach is verified with the available open literature results showing a clear agreement. The effects of various factors such as volume fraction and non-straight shape of CNT, CNT/polymer interphase region, CF volume fraction, random and regular arrangement of CFs, plate geometrical parameters and impactor velocity on the low velocity impact behavior of the CNT/CF-reinforced hybrid nanocomposite plates are studied. [ABSTRACT FROM AUTHOR]

Variable stiffness (VS) composites made by fiber steering have received intensive attention due to the tailorability of the stiffness and strength properties. However, a significantly larger number of elements are required to converge for VS composites, which results in much longer runtime and makes the design and optimization more complicated. In this paper, an efficient design optimization method assisted by multi-fidelity surrogate models is presented for the buckling design of VS composites. To reduce the computational burden, a multi-fidelity surrogate model called hierarchical Kriging is constructed through a few expensive high-fidelity samples and many cheap low-fidelity samples. Fine and coarse finite element (FE) analysis is performed respectively to calculate the structural responses for corresponding datasets. The efficient global optimization based on a modified expected improvement criterion is employed and used to adaptively add new samples of variable-fidelity. Two case studies, a composite plate subjected to uniform uniaxial compression and a composite cylinder under pure bending, are investigated. The effects of different number of design variables and coarse FE model mesh density on the optimum configuration are studied to demonstrate the effectiveness and robustness of the method. The results indicate that the present method can remarkably reduce the number of high-fidelity FE evaluations and improve the optimization efficiency when compared with available methods in the literature. Additionally, the investigation in the mechanism of loading carrying capacity improvement shows that the increase is mainly due to the load redistribution. [ABSTRACT FROM AUTHOR]

This paper studies the free vibration behavior of hybrid laminated plates using a layer-wise formulation. The laminated structures are made of graphite fiber-reinforced composite (GFRC) and multilayer functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plies. The internal single-walled carbon nanotubes (SWCNTs) are distributed in layer-wise form along the ply thickness direction either uniformly or functionally graded according to four separate patterns. Both the linear and nonlinear of the CNTs distributions form are considered. Theatrical formulations are based on the first-order shear deformation theory (FSDT), and finite element method is employed to obtain the nondimensional natural frequency. The elastic modulus of both GFRC and CNTRC plies composed the hybrid laminated plate is obtained by a micromechanics model. Initially, the provided results are validated by comparing it with the literature; thereafter, a parametric study is carried out the influences of laminates configuration, number of CNTRC plies layers, CNT volume fraction, CNT distribution patterns, linear and nonlinear distribution of CNTs, plate width-to-thickness ratio, plate aspect ratio, boundary conditions, stacking sequences, and number of plies on the free vibration behavior of hybrid laminated plates. Some final remarks considering the laminated plate configuration and the distribution form of the CNT fillers are presented in order to provide a useful observation on the design criteria of the laminated composite plate structures. [ABSTRACT FROM AUTHOR]

The semi-analytical finite element (SAFE) method is widely used for studying properties of guided waves along composite waveguides. However, evaluating the modes associated to high wave numbers requires important mesh refinements and may significantly increase the computational cost. This paper presents a semi-analytical isogeometric analysis (SAIGA) to calculate the dispersion relation of functionally graded or multilayer plates coupling with fluids. High-order elements based on non-uniform B-splines (NURBS) basis functions are used. Several numerical examples are then studied for different problems in order to assess the efficiency of proposed method: (i) homogeneous plates; (ii) functionally graded plates; (iii) composite plates (with strong contrast of rigidity between layers); (iv) fluid-immersed plates. The results obtained are compared with the ones derived from analytical approaches and by the conventional SAFE method using Lagrange polynomials. For all cases, the dispersion curves evaluated by using enriched-NURBS basis functions achieve a significant better precision than using conventional Lagrangian functions (for the same number of degrees of freedom or the same order of shape functions), especially for the higher modes. The continuity of the stress shape modes at the interfaces is also shown to be much improved by using SAIGA. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic stiffness method (DSM) is developed for the vibration analysis of laminated cylindrical and conical shells, which are partially filled or surrounded by quiescent fluid. The Reissner and Naghdi's thin shell theory and incompressible fluid equations are employed on the structures and fluid, respectively, so as to characterize the fluid–structure coupling model. Shell elements with/without fluid loadings are derived and assembled by using the dynamic stiffness method. Numerical examples of the free vibration analysis for both empty and fluid-filled shells are validated against previous studies. Remarkable advantages regarding computational efficiency and accuracy of the DSM, especially in high-frequency domain, are presented through response curves compared with finite element calculations. As for partially fluid-filled or fluid-surrounded laminated shells, parametric studies are made to find the effects of material properties, fluid heights and semi-vertex angles on the dynamic characteristics. [ABSTRACT FROM AUTHOR]

Background: Experimental modelling techniques are still rare for composite structures under complex thermal environments. Objective: In this paper, by taking a fibre-reinforced composite plate (FRCP) as an example, a lumped parameter model of the FRCP with temperature dependence is developed from an experimental perspective. Methods: Initially, a series of thermal vibration measurements are performed under different temperatures to characterize the temperature-dependent vibration behaviours of the FRCP, in which the natural frequencies and modal damping ratios are identified via the variational mode decomposition method. Then, according to the degree of freedom division criterion of the half-wave number, a mass-spring-damper lumped parameter model of this type of composite plate considering additional thermal stiffness is established. Finally, a novel method of determining the lumped stiffness and damping parameters in this model is proposed based on the above experimental data. Results: The developed model is verified by comparing the theoretical natural frequencies, modal shapes and resonant responses with the test results at 40, 120, 220 and 300 °C, for which the calculation errors are within an acceptable range. Conclusions: It has been found that the accuracy of this lumped parameter model can be further improved by applying a larger number of modes to inversely calculate the lumped stiffness and damping parameters. Meanwhile, the efficiency can also be increased by adopting an appropriate step size in the iterative calculation of the additional thermal stiffness. [ABSTRACT FROM AUTHOR]

The effect of geometrical nonlinearities due to pressure load on the thermal buckling and dynamic characteristics of composite plates are investigated in this paper, which is the main contribution of this research work. The mechanical behavior of the plate is described with the first-order shear deformation theory. The geometrical nonlinearity due to both thermal effect and pressure load is introduced in the finite element model of the plate via additional stiffness matrices. Thermal buckling and modal analysis of a four-sided simply supported rectangular composite plate under different pressure fields are conducted. Numerical results show that both the mode frequencies and critical buckling temperature of the plate rise with the increase of the pressure. The vibrational mode shapes change with the gradient pressure load field. The maximum buckled deflection point moves from the center to the place where is easier to reach compressive stress state under uniform thermal load. The pressure distribution has a significant effect on the buckling mode shapes of the plate. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the free and forced vibration behavior of a sandwich beam with functionally graded porous core and composite face layers embedded with shape memory alloy (SMA). Three different porosity patterns are assumed through the thickness direction of the core, and composite face layers are reinforced with carbon nanotubes (CNT). The sandwich beam is resting on an elastic foundation which is simulated by Vlasov's model. By using Hamilton's principle and first-order shear deformation theory, the governing equations of motion are derived. The analytical solution is presented to solve the equations of motion using Navier's solution. Results are verified with corresponding literatures. Finally, the effects of important parameters such as temperature, volume fraction of SMA, porosity distribution, weight fraction of CNT, and geometric parameters are explored in detail. [ABSTRACT FROM AUTHOR]

In the present paper, a flexible framework is developed for the optimization of composite laminate plates. In this framework, an optimization algorithm is employed to find the optimal stacking sequence design of the FE models by interfacing the Abaqus solver with MATLAB through a Python script. The Python script submits dimension, orientation, and diameter of the cutout combinations to Abaqus/CAE. The performance of the codes is validated by applying them to several problems of previous research. Three distinct types of boundary conditions, namely CCCC, SCSC, and SSSS, with different geometries comprising a square and rectangular plates with and without cutouts, are considered as optimal design problems. Besides that, analyses are performed on new symmetrical composites with 16 and 80 plies. The framework is equipped with the GA for optimizing the fiber orientations and maximizing the buckling capacities. The results are comprehensively discussed, showing a reasonable agreement with the literature. This code can easily be used by scientists and industry professionals as an automated tool for optimizing different finite element models and using any arbitrary optimization algorithm. [ABSTRACT FROM AUTHOR]

Acoustic emission (AE) source localization is a powerful detection method. Time Difference Mapping (TDM) method is an effective method for detecting defects in complex structures. The core of this method is to search for a point with the minimum distance away from the verification point in the time difference database. In Traditional Time Difference Mapping (T-TDM) method and Improved Time Difference Mapping (I-TDM) method, the larger database and denser grids allow the higher localization accuracy. If the location points are not included in the database, the localization accuracy of the T-TDM and I-TDM methods will be greatly affected. To solve the above problems, a new AE source localization method, Generalized Regression Neural Network Based on Time Difference Mapping (GRNN-TDM), is proposed to improve the localization accuracy in the study. In the proposed method, the time difference data of the sensor path on all nodes in the time difference mapping are used as the training input data and the coordinates of grid nodes are used as the training output data. After continuous learning and training, the neural network model predicts its possible source location with the time difference data collected from the verification point. In this paper, the localization of AE sources with T-TDM, I-TDM and GRNN-TDM methods was studied in four composite plates with different fiber layers and an aluminum plate with holes. The localization results showed that the localization accuracy of the GRNN-TDM method was higher than that of T-TDM and I-TDM methods. [ABSTRACT FROM AUTHOR]

The premature failure analysis of laminated composite structures through damage inspections at initial level has gained considerable importance in recent years. Delamination is one of the major failure mechanisms which occur due to low inter-laminar fracture toughness of the matrix in composite structures. Detection of delamination is crucial to ensure safety and reliable use of composites. In the paper, the modal curvature and flexibility methods have been applied for delamination detection in composite leaf spring through analytical and finite element approaches. First, finite element models of healthy and delaminated leaf spring are formulated to evaluate the Eigen value and Eigen vectors. Next, the absolute curvature difference and change in flexibility in both springs are determined after mass normalization. The presence, location and severity of delamination in a spring are found through change in absolute modal curvature and difference in local flexibilities. The modal curvature method precisely identifies the delamination location and its severity than the modal flexibility method. [ABSTRACT FROM AUTHOR]

Many attempts have been conducted for green synthesis of biofunctional scaffolds and implant coatings. Hydroxyapatite Ca5(OH)(PO4)3 (HA), is an excellent material for these purposes. HA is a major mineral component of vertebrate bones and teeth; it constitutes 70 wt% of human bones. This paper reports on the sustainable fabrication of HA particles in different morphologies including nanoplates (400 nm L and 150 nm W), and nanorods (10 nm D and 500 nm L). XRD diffractogram revealed highly crystalline structure. HA nanoplates were surface modified with poly(ethylene-co-AA) polymeric surfactant; organic modified HA nanoplates demonstrated complete change in surface properties from hydrophilic to hydrophobic. It demonstrated effective phase transfer from aqueous phase to organic phase, with decrease in nanoplate size to 100 nm L, 50 nm W. Layered HA plates were further developed via surface modification with dodecanedioic acid; this approach can offer laminated or exfoliated plates for effective integration into bio-compatible polymers. This manuscript shaded the light on facile green synthesis of HA nanoparticles with controlled morphology and surface properties. [ABSTRACT FROM AUTHOR]

Buckling analysis of isotropic and orthotropic plates resting on two-parameter Pasternak's foundations using the four-variable refined plate theory is presented in this paper. The theory takes account of transverse shear effects and parabolic distribution of the transverse shear strains through the thickness of the plate; hence, it is unnecessary to use shear correction factors. Governing equations are derived from the principle of virtual displacements. The nonlinear strain–displacement of Von Karman relations is also taken into consideration. The closed-form solution of a simply supported rectangular plate subjected to in-plane loading has been obtained by using the Navier method. Numerical results obtained by the present theory are compared with classical plate theory solutions, first-order shear deformable theory solutions, higher-order shear deformation theory and available exact solutions in the literature. The effects of the foundation parameters, side-to-thickness ratio and modulus ratio, the isotropic and orthotropic square plates are considered in this analysis. It can be concluded that the present theory, which does not require shear correction factor, is not only simple but also comparable to the first-order shear deformable theory. [ABSTRACT FROM AUTHOR]

In the present study, nonlinear flutter and post-flutter behavior of a variable stiffness composite wing-like plate is investigated. The variable stiffness is obtained by varying fiber angles continuously according to a selected curvilinear fiber path function in the composite laminates. Flutter speed, limit cycle oscillations and bifurcation diagrams of the composite plate are explored for three different fiber path functions using the nonlinear structural model obtained based on the virtual work principle. The paper aims to exploit the ideal fiber paths with enhanced aeroelastic flutter and post-flutter properties for a composite plate in supersonic flow speed. First-order linear piston theory is applied to model the aerodynamics, and generalized differential quadrature is employed to solve the governing equations. Von Karman nonlinear strain theory is used to account for the geometric nonlinearities, and first-order shear deformation theory is employed to consider the transverse shear effects in the structural model. Time integration of the equation of motion is carried out using the Newmark average acceleration method. Different curvilinear fiber paths are introduced to enhance flutter instabilities and post-flutter behavior of the composite plate. Results demonstrate that the fiber orientation has a significant effect on the dynamic behavior of the plate and the asymmetric properties as well as the behavior of the limit cycle oscillation. [ABSTRACT FROM AUTHOR]

The newly developed penta-graphene is a two-dimensional (2D) carbon allotrope with promising mechanical properties. This paper investigates the nonlinear post-buckling and vibration of imperfect three-dimensional penta-graphene composite plates resting on elastic foundations and subjected to uniform external pressure and axial compressive load. The elastic constants of the single-layer penta-graphene are fully determined by the density functional theory by fitting the equation of strain energy to the density functional theory energy. Specifically, the elastic constant C 66 which has not been considered by other authors is also determined. The motion and compatibility equations are derived based on the classical plate theory taking into account von Karman geometrical nonlinearity, initial geometrical imperfection and Pasternak type elastic foundations. For nonlinear post-buckling, the Bubnov–Galerkin method is applied to obtain the load–deflection amplitude curves while the Runge–Kutta method and harmonic balance method are used to obtain the deflection amplitude–time curves and the amplitude–frequency curves for nonlinear vibration. Numerical results show the effects of geometrical parameters, initial imperfection and elastic foundations on the nonlinear post-buckling and vibration of the imperfect 2D penta-graphene plates. The present results are also compared to others to validate the accuracy of the applied method and approach. [ABSTRACT FROM AUTHOR]

Highly porous metal oxide nanostructures are attractive candidates for many applications because of their rich pores. In this paper, some highly porous metal oxide nanosheets, including, but not limited to, Co3O4, and α-Fe2O3 have been successfully synthesized by a simple and scalable route with the aid of konjac glucomannan (KGM). The Co-KGM and Fe-KGM composite plates as precursors that were fabricated by the impregnation of KGM template in respective metal nitrate solution. After that, these composites were calcined in an air environment to form the highly porous metal oxide nanosheets because the KGM nanofibrils as sacrificial template that was combusted at high temperature. The route would offer an efficient solution to fabricate metal oxide nanosheets with highly porous textures. Furthermore, the highly porous hematite nanostructures showed excellent catalytic activity for benzylation benzene by benzyl chloride with fast conversion and high selectivity indicated promising aspects of these materials. [ABSTRACT FROM AUTHOR]

In the present paper, for the first time the vibration behavior of hybrid composite conical shells reinforced with shape memory alloy (SMA) fibers is investigated. The temperature-dependent properties of SMA fibers and composite are accurately considered. Using the one-dimensional constitutive law of Brinson, thermo-mechanical properties such as recovery stresses, elasticity modulus and shear modulus with uniform temperature change are calculated for SMA fibers. Love's first approximation classical shell theory with von-Kármán type of geometrical nonlinearity is used in conjunction with Hamilton's principle for deriving the equations of motion. A semi-analytical solution is presented so that trigonometric functions are applied in the circumferential direction, and the generalized differential quadrature method is used to discretize the equations of motion along the longitudinal direction. Finally, parametric studies are done to investigate the effects of volume fraction, pre-strain, location of SMA fibers, boundary conditions, semi-vertex angle of the cone, and temperature on the vibration characteristics of the SMA hybrid composite conical shells. It is shown that a proper utilization of SMA fibers significantly increases the fundamental frequency and vibration control of the SMA hybrid composite conical shells. [ABSTRACT FROM AUTHOR]

Purpose: The main objective of this paper is to develop a model that will combine economic and environmental assessment tools to support the composite material selection of aircraft structures in the early phases of design and application of the tool for an aircraft elevator. Methods: An integrated life cycle cost (LCC) and life cycle assessment (LCA) methodology was used as part of the sustainable design approach for the laminate stacking sequence design. The model considered is the aircraft structure made of carbon fiber reinforce plastic prepreg and processed via hand layup-autoclave process which is the preferred method for the aircraft industry. The model was applied to a cargo aircraft elevator case study by comparing six different laminate configurations and two different carbon fiber prepreg materials across aircraft's entire life cycle. Results and discussion: The results show, in line with other studies using different methodologies (e.g., life cycle engineering, or LCE), that the combination of LCA with LCC is a worthwhile approach for comparing the different laminate configurations in terms of cost and environmental impact to support composite laminate stacking design by providing the best trade-off between cost and environment. Elevator LCC reduces 19% by changing the material type and applying different ply orientations. Elevator LCA score reduces 53% by selecting the optimum instead of best technical solution that minimizes the displacement. Improving the structural performance does not always lead to an increase in the cost. [ABSTRACT FROM AUTHOR]

In this paper, the free vibration of laminated composited cylindrical shells with two kinds of non-continuous supported boundary condition are investigated. The artificial springs are used to simulate the arcs supported and points supported boundary condition. The equations of motion are derived by using the Chebyshev polynomials and the Lagrange equation, and Donnell's shell theory is employed in this process. The accuracy of the present method compared with that of literature, and convergence analysis is carried out at the same time. Then, the influences of spring stiffness, the number of supported point, and the lamination schemes of non-continuous supported laminated composite cylindrical shells on frequency parameter are studied. The results show that the method can accurately deal with the free vibration of laminated shells with arbitrary non-continuous boundary and arbitrary lamination schemes. [ABSTRACT FROM AUTHOR]

In this paper, the 2219 aluminum alloy / T2 copper composite plate with good properties and almost no metallurgical defects was obtained by the explosive welding method. Meanwhile, its microstructure and mechanical properties were systematically studied. In terms of microstructure, two typical morphologies of local melting zone and vortex structure around the interface of the composite plate can be observed and both morphologies represented brittle-hard Al-Cu intermetallic compound regions. The interface of the composite plate mainly included Al2Cu and Al4Cu9 intermetallic compound layers. The Al4Cu9 layer had a typical {001} texture with the smaller grain size, the lower dislocation density and the lower energy. In terms of mechanical properties, the tensile strength of the composite plate reached 55% of the aluminum alloy cladding material and 70% of the copper substrate material, respectively. The composite plate fractured in the order of aluminum alloy, interface, copper and showed brittle fracture characteristics in the crack initiation region. The brittle-hard second phases in the aluminum alloy matrix were extremely unfavorable to the mechanical properties of the composite plate. [ABSTRACT FROM AUTHOR]

Particle-reinforced composites (PRCs) are usually studied by some averaging or homogenization techniques. In this, the effective properties are derived by assuming that particles are dispersed within composites according to some given (probabilistic) distribution. Such approaches restrain the possibilities of studying the contribution of exact location and parameters of individual particles to the overall behavior of composites. In this paper, we attempt to fill this gap by deriving the mesoscopic model of such composites corresponding to a continuum with point inhomogeneities. We start from a fully microscopic model where the composite is regarded as a continuum with spherical inclusions. Letting the diameter of inclusions decrease to zero, material parameters of the composite are represented in terms of the Dirac distribution. The Mindlin–Reissner–von Kármán thick plate theory is considered as a particular case, and closed-form formulas are obtained for the plate stiffness coefficients. Numerical analysis of a thick composite plate reinforced over its mid-surface justifies the theoretical derivations. [ABSTRACT FROM AUTHOR]

In this research, nonlinear dynamic behaviors of multiscale composites doubly curved shells have been investigated by employing multiple scales Perturbation Method. Three-phase composites shells with polymer/Carbon nanotube/fiber (PCF) according to Halpin–Tsai model have been assumed. The displacement- strain of nonlinear vibration of multiscale laminated doubly curved shells via higher order shear deformation (HSDT) theory and using Green–Lagrange nonlinear shell theory is obtained. The governing equations of composite doubly curved shell have been derived by implementing Hamilton's principle and shell considered to be simply supported. For investigating correctness and accuracy, this paper is validated by other previous researches. Finally, bifurcation diagram, phase portraits and Poincare maps are investigated. The results indicate different dimensionless force; curvature ratio and kind of distribution pattern have strong influence on nonlinear vibration control of the composite multiscale doubly curved shell. [ABSTRACT FROM AUTHOR]

The present paper deals with a new holistic closed-form analytical model for the local buckling load of thin-walled composite beams with I-, Z-, C-, L- and T-cross sections under axial compressive load. The beam is simply supported at both ends (Euler case II), and the plate behaviour of web and flanges is described by the Classical Laminated Plate Theory. Furthermore, symmetric and orthotropic laminates are considered. In previous investigations on composite beams under compression, the web and flange plates are considered as separate composite plates. The present analysis is performed using the Ritz method in which an approach for the entire cross section is realized. The individual webs and flanges of the beam are assembled by suitable continuity conditions into one system. In order to achieve that, new displacement shape functions for web and flange that fulfil all boundary conditions have been developed. The present closed-form analytical method enables the explicit representation of the buckling load for the entire composite beam under axial compression. The comparison between the present approach and comparative finite element simulations shows a very satisfactory agreement. The present method is ideal for pre-designing such structures, highly efficient in terms of computational effort and very suitable for practical engineering work. [ABSTRACT FROM AUTHOR]

This paper deals with an efficient optimization method of combining fiber orientation and topology for constant-stiffness composite laminated plates. The optimal topology and fiber orientation can be simultaneously obtained, using the proposed method. To overcome the non-monotonous behaviors derived from directly optimizing fiber orientation, the lamination parameters are selected as design variable. The proposed method mainly includes two steps. Initially, lamination parameters and density are taken as the design variables for determining the fiber orientation and topology shape. A combined optimization model is built based on the penalization theory. The optimal lamination parameter and topology shape can be achieved simultaneously in this step. Then, solving nonlinear equations is transformed into a least squares optimization problem. The optimal fiber orientation is obtained and matched with the optimal lamination parameter. Finally, numerical examples of designing short cantilever beam and compliant inverter are performed to illustrate the validity of this method. [ABSTRACT FROM AUTHOR]

This research paper presents an isogeometric plate finite element formulation for analysis of thick composite plates. Isogeometric finite element method which is based on non-uniform rational B-splines (NURBS) basis functions, is a novel numerical procedure developed to bridge the gap between CAD and FEM modeling of structures. In order to investigate the behavior of isogeometric plate elements under static loading, plate kinematics is based on third order shear deformation theory (TSDT) of Reddy, which is free from transverse shear locking. This paper discusses accurate transverse stress recovery procedures for TSDT isogeometric finite elements. Numerical experiments with quadratic, cubic and quartic elements are presented and obtained results are compared to other available ones. [ABSTRACT FROM AUTHOR]

A Lagrange parameterization of lamination parameters which are used for optimization of variable stiffness laminates is presented. The advantages of the approach are: a) the design variables become independent of the finite element mesh and, b) the smoothness of the solution is inherently guaranteed. Due to independency of design variables of the finite element mesh, the reduction in the number of design variables is drastic, once variable stiffness laminates usually demand a fine mesh. The lamination parameters formulation allows a more precise and concise approach to laminate design, removing difficulties related to fiber direction and stacking sequence, increasing the chances to find a global optimal solution. In this paper, the Lagrange parameterization is used for the maximization of the buckling load of a variable stiffness composite plate. [ABSTRACT FROM AUTHOR]

The study of vibrational energy harvesting using piezoelectric patch integrated on isotropic beam-like or plate-like thin structures has received significant attention over the past decade. Multilayer orthotropic composite plates are widely used in aerospace, automotive and marine applications, where they can be considered as host structures for vibration-based energy harvesting. In this paper, an exact analytical solution and numerical validation of a piezoelectric energy harvester structurally integrated to a thin multilayer orthotropic plate are presented. Electroelastic model of the thin multilayer composite plate with the piezoelectric patch harvester is developed based on a distributed parameter modeling approach with classical laminate plate theory assumptions for all-four-edge-clamped (CCCC) boundary condition. Closed-form steady-state expressions for coupled electrical outputs and structural vibration response are derived under harmonic transverse force excitation in the presence of a resistive load. Analytical electroelastic FRFs related to the voltage output as well as vibration response to force input are derived and generalized for different boundary conditions of host plate. The results of numerical and analytical models from multiple vibration modes are compared first for validating the analytical model with a case study employing a thin PZT-5A piezoceramic patch attached on the surface of a multilayer orthotropic composite CCCC plate. For this purpose, finite-element analysis is carried out by using ANSYS mechanical APDL software. Then, it is important to specify parameters in energy harvesting model, so positioning of piezoceramic patch harvester and excitation point force on the voltage output FRFs is discussed through an analysis of dynamic strain distribution on the overall plate surface. In addition, the effects of various composite laminate plates with different stacking sequences as host structures on generated power are discussed in details as well. [ABSTRACT FROM AUTHOR]

Composite plates are susceptible to various damages in complex conditions and working environments, which may reduce the reliability of the structure and threaten equipment and personal safety. Thus, the implementation of a robust online Structural health monitoring (SHM) system for these composite structures becomes imperative. To enhance reliability and safety, we introduce a robust online SHM system anchored by our newly developed damage detection Bayesian neural network (DD-BNN). The main contribution of this study lies in the DD-BNN to perform precise and reliable damage detection and localization in composite plates using only one actuator-receiver pair without any signal/feature pre-processing and human intervention. The proposed DD-BNN model innovatively combines probabilistic modeling with deep learning to address uncertainty in Lamb wave-based damage detection and model performance for composite plates, featuring a specialized probabilistic layer trained through Bayesian inference to efficiently encapsulate and manage uncertainty in model weights and activation. Notably, our method significantly simplifies the SHM system design and manual operation requirements. In addition, this approach not only reduces overfitting but also enhances robustness to noise, as confirmed by experiments on perturbation analysis of Gaussian and Poisson noise. [ABSTRACT FROM AUTHOR]

The lay-up optimization problems of composite plates against buckling are studied. The plate has symmetric lay-up and is loaded by an in-plane loading. The Classical Lamination Plate Theory is used. The necessary optimality conditions for the plate orthotropy/anisotropy optimization problems are considered, with special attention to bending-twisting coupling. The purpose of the optimization is to maximize the (lowest) buckling eigen value. The varied lay-up/layer orientation angles are considered both as smooth functions of the location coordinates and as having the same values at every point. It is shown that the twisting moment (calculated in the principal curvature axes) plays an important role in the conditions. Two example problems for a thin composite plate, loaded by shear, are considered. The first one corresponds to the case of one shear loading direction. The details of some known numerical solutions are studied. The obtained numerical results are in agreement with the theoretical results. The maximal lowest eigen values are 2-folded ones. A schematic model for treatment of the known optimal numerical solution (60° unidirectional lay-up for a long plate loaded by shear) is proposed. The second example problem corresponds to the case of shear loading acting in two opposite directions. The ways of equalizing the lowest buckling values corresponding to both loading directions are proposed. Numerical results for various aspect ratio and plate thickness values are presented. The potential of weight saving is demonstrated. [ABSTRACT FROM AUTHOR]

This paper is a continuation of Survey I [], where the historical background and general remarks on the problem formulation and solution methods were outlined and results related to plane-strain problems were reviewed. In the present paper, a review of axisymmetric and 3D buckling delamination problems is presented. [ABSTRACT FROM AUTHOR]

The paper illustrates the application of the particle swarm optimization (PSO) algorithm to the lay-up design of symmetrically laminated composite plates for maximization of fundamental frequency. The design variables are the fiber orientation angles, edge conditions and plate length/width ratios. The formulation is based on the classical laminated plate theory (CLPT), and the method of analysis is the semi-analytical finite strip approach which has been developed on the basis of full energy methods. The performance of the PSO is also compared with the simple genetic algorithm and shows the good efficiency of the PSO algorithm. To check the validity, the obtained results are compared with those available in the literature and some other stacking sequences, wherever possible. [ABSTRACT FROM AUTHOR]

This paper proposes a new Deep Feed-forward Neural Network (DFNN) approach for damage detection in functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates. In the proposed approach, the DFNN model is developed based on a data set containing 20 000 samples of damage scenarios, obtained via finite element (FE) simulation, of the FG-CNTRC plates. The elemental modal kinetic energy (MKE) values, calculated from natural frequencies and translational nodal displacements of the structures, are utilized as input of the DFNN model while the damage locations and corresponding severities are considered as output. The state-of-the art Exponential Linear Units (ELU) activation function and the Adamax algorithm are employed to train the DFNN model. Additionally, in order to enhance the performance of the DFNN model, the mini-batch and early-stopping techniques are applied to the training process. A trial-and-error procedure is implemented to determine suitable parameters of the network such as the number of hidden layers and the number of neurons in each layer. The accuracy and capability of the proposed DFNN model are illustrated through two distinct configurations of the CNT-fibers constituting the FG-CNTRC plates including uniform distribution (UD) and functionally graded-V distribution (FG-VD). Furthermore, the performance and stability of the DFNN model with the consideration of noise effects on the input data are also investigated. Obtained results indicate that the proposed DFNN model is able to give sufficiently accurate damage detection outcomes for the FG-CNTRC plates for both cases of noise-free and noise-influenced data. [ABSTRACT FROM AUTHOR]

The magnetoelectric (ME) laminated composite is an important multifunctional material for developing novel electronic devices that provide many applications in sensing, energy conversion, filtering, etc. Following the previous investigations, this paper proposes theoretical modeling to study the relationship between a bar-shaped ME laminated composite's enhancement effects and material properties. This composite has a breakthrough idea that produces two operating modes (sensing and transducing) in the same working process. Our analyses are based on the magneto-elastic-electric equivalent circuit and mechanical connections between an ME laminated composite and a piezoelectric plate. Our works not only predicted the ME outputs against magnetic field bias change but also studied the relationship of the length ratio between the ME laminated composite and the piezoelectric plate. The results showed that the ME outputs of the transduction mode are much bigger than the sensing mode at resonance, which strongly depended on the dimension and the physical properties of the sample. These findings provided a promising gate for the researchers to develop a single electronic device that combined sensing and power conversion. [ABSTRACT FROM AUTHOR]

This paper models the effect of material parameter randomness on the initial buckling load of rectangular, specially orthotropic, composite laminates. The basic formulation for stability analysis is based on classical laminate theory. A perturbation technique is used to obtain the solution of the governing equation. The effects of aspect ratio and change in standard deviation of the input parameters have been investigated for several laminate configurations. The solution has also been checked with the help of Monte Carlo simulation. [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]

The ice formation over the aerofoil structure of the aircraft wing has been an obstruction as they abrupt the airflow, acting as drag. The investigation will intend to determine ice accumulation on carbon fiber-reinforced polymer (CFRP), approximated as ice build-up on aircraft wings. The observation is carried out over quasi-isotropic composite laminates using ultrasonic-guided waves with a central working frequency regime of 100 kHz. The three-dimensional (3D) finite element (FE) simulations are performed to observe the scattering effect to explore the reflection site in the far field. This effect was quite prominent for different thicknesses of Glaze ice (G-Ice) and was found to be strongly linked with the wave propagation and dispersion effect. The scattering results for the reflection of Lamb mode, when it interacted with the G-Ice interface, were quite noteworthy along the angular region rather than on the center line, indicating that the scattering was more prominent due to the presence of a 45° or (− 45)-degree fiber orientation in that laminate. A similar but complex scattering phenomenon was observed for different stacking sequences where the wave propagation angle and its amplitude at the receiver nodes are found to be closely bound with the exponential decay in group/phase velocity for the ice thicknesses studied. The FE approach is verified, and the results are validated analytically. Analytically, we have investigated a much-closed approximation with the detectability obtained from three-dimensional studies. Where the dispersion study performed has also contributed to verifying the present investigation in the long wavelength limits. This study can reveal the various optimized locations for placing the sensor for ice detection and quantification, which can be further helpful for practical guided wave inspection in ice detection and its removal. [ABSTRACT FROM AUTHOR]