Search

This paper outlines an experimental investigation into the durability of large-scale adhesively bonded joints with a thick layer of methyl methacrylate adhesive (MMA). Ageing has been performed by immersion in a 3.5 wt% NaCl solution for 10 weeks at 50°C. Two aged and one unaged specimen were subjected to tensile testing, and three aged and one unaged specimen were loaded up to ~ 3.5 million fatigue cycles followed by a residual tensile test. The ductility of the adhesive is affected by ageing and fatigue testing. Despite a decrease in ductility, the plastic zone development was adequate for the required strain redistribution without compromising the joint performance (strength and stiffness) demonstrating the fatigue tolerance of the joint. The shear, longitudinal, and peel strain values in the adhesive bulk are evaluated by digital image correlation. The shear strength values are significantly higher than the requirements following from the design. All specimens failed by sudden delamination of the composite plate. Post-mortem analysis showed no corrosion travel at the interface of steel and adhesive. [ABSTRACT FROM AUTHOR]

In the present work, the general stiffness matrix method is extended in the case of a functionally graded magneto-electro-elastic plate to analyze the free vibration response of a functionally graded composite plate. The material properties are assumed to be continuously graded in the thickness direction. The novelty of this paper is to utilize this efficient method to the dynamic analysis of a wide range of composite (multilayer) plates, with linear or non-linear thickness profiles, and functionally graded in the thickness, without any limitation. The convergence of this method is thoroughly discussed. Here, the converged results are obtained when the number of sub-layer is $ N \le 11 $ N ≤ 11. A parametric study was also conducted to show the effect of gradation of mechanical properties of the composite on the phase velocity and the modal shape. The dynamic model developed here can be used in the graded material design of the functionally graded piezoelectric-piezomagnetic (noted FGPPM) composite plate for achieving specified dynamic characteristics. [ABSTRACT FROM AUTHOR]

This paper presents the time-domain viscoelastic formulation based on the Carrera unified formulation (CUF) to obtain the response of composite structures submitted to bending loads. The governing equations are obtained through a modified form of the principle of virtual displacement (PVD) for a viscoelastic analysis. The problem is solved using the Laplace transform instead of direct integration to reduce the computational cost. The results demonstrate the strong capability of the time-domain viscoelastic formulation. Overall, the proposed methodology allows the direct implementation of new optimized high order deformation theories including the thickness stretching effect that may be implemented in futures works. [ABSTRACT FROM AUTHOR]

In this paper large deformation of the skew microplate made of laminated composite enhanced with graphene nanosheets is investigated using first shear deformation theory (FSDT) when the plate undergoes combination of mechanical and thermal loads. Halpin-Tsai model is utilised to model mechanical properties while for thermal properties Schapery model is considered. First, shear deformation of the plate was obtained while using Green-Lagrange tensor the non-linear strain of the microplate is extracted using the von-Karman assumptions. Then, by Modified Coupled Stress Theory (MCSD), the components of Cauchy and Couple stress tensors are specified. Finally, using Hamilton Principle the governing equation of the microplate and boundary conditions are computed. After deriving analytical governmental equation results are presented for the simple support boundary condition and the proposed model is validated by previously reported data and it proves to be promising. Primary results showed that with raising skew angle deflection and bending moment decreases which means microplate becomes more rigid in higher skew angles. Higher mechanical loads lead to higher deflections and bending moments. Four different configurations of the layers were analysed from which angle-ply configuration possessed highest deflection and bending while UD configuration revealed the lowest values of deflection and bending moment. [ABSTRACT FROM AUTHOR]

In this paper, for reducing the number of independent generalized displacements of the traditional piecewise model to decrease the number of vibration equations, a refined piecewise shear deformation model considering the effect of rotary inertias and shear deformation for vibration analysis of laminated composite and sandwich plates is presented. Unlike the conventional piecewise model, the significant novelty of the proposed theory is that the new proposed piecewise theory reduces the number of independent generalized displacements from 9 to 8. Some relevant assumptions, dividing the transverse displacement into bending and shear parts, are introduced into the traditional piecewise model, and the displacement fields of the refined piecewise shear deformation theory are obtained. Next, the governing equations are derived by employing Hamilton's principle and solved by the closed-form Navier method. Then, the present solutions are compared with those available in the previous literature for confirming their validity. Finally, the variations of frequencies and loss factors with system parameters are evaluated and presented graphically. [ABSTRACT FROM AUTHOR]

In this paper, minimization of delamination effect on laminated composite plates using smart (piezoelectric and magnetostrictive) materials has been investigated. The static and dynamic responses of the smart composite plates with/without delamination have been obtained using the finite element method. The validation and comparison studies of the laminated composite plate have also been performed to show the level of accuracy of the presently adopted model by solving a few examples related to static and frequency cases. For control and minimization of delamination effect, smart materials have been introduced at the various layers of the laminated panel. Further, the influence of delamination size, location, orientation scheme, aspect ratio, modular ratio and different boundary conditions on the dynamic response of the smart delaminated composite plate has been analyzed. Finally, optimization study has been carried out to find the optimal value of these parameters by minimizing the difference between the frequency responses. Here, two optimization algorithms TLBO and PSO have been considered to carry out the optimization study and results obtained from both techniques are validated and compared. [ABSTRACT FROM AUTHOR]

This paper investigates the free vibration analysis of cutout laminated composite plates resting on an elastic foundation of the Winkler and Pasternak type. An efficient isoparametric 9-noded Lagrangean C0 finite element method is developed based on five degrees of freedom (d.o.f) first-order shear deformation theory (FSDT), which has the benefit of the requirement of only one variable along the thickness to model the plate equations to obtain the numerical results from the formulation. The equation of motion of the plate is derived using the virtual work principle. The accuracy and efficiency of the current formulation are validated with established results concerning free vibration analysis of laminated composite plates on elastic foundations and plates containing cutouts. It is found that the results obtained using the present formulation have variation within ±1.5% of the established results. After sufficient validation of the present formulation, new parametric results are given for cutout laminated composite plates resting on elastic foundations with varying elastic foundation stiffness parameters, boundary conditions, cutouts, side-to-thickness ratios, and the aspect ratio of plate and fiber angle orientations. The impact of cutouts on the dynamic behavior of laminated composite plates is investigated, and interestingly, it is observed that cutouts alter the frequency response of plates when introduced to plates without elastic foundations or plates resting on elastic foundations having low stiffness parameters; however, when cutouts are introduced to plates with high elastic foundation stiffness, the cutouts have very negligible impact on the dynamic behavior of plates. It is observed that the layout and the pattern of the cutout in the laminated composite plate affect the dynamic behavior of plates at all elastic foundation stiffnesses. [ABSTRACT FROM AUTHOR]

Debonding regions can occur at the interface of aluminium/rigid polyurethane foam composite plates (ARCP) during manufacturing. To help improve the technological process of manufacture, it is essential to precisely locate these debonding regions. This paper proposed a method to image the debonding regions in the ARCP based on the A0 mode Lamb waves. To study the influence of overlap between the debonding region and the coil of the electromagnetic acoustic transducer (EMAT) on Lamb wave propagation, a three-dimensional finite element simulation model was developed. A positive linear relationship was obtained between the amplitude of the A0 mode and the overlap rate between the debonding region and the coil of the EMAT, which was verified through experiments. Based on such relationship, an imaging method was proposed. The imaging method consisted a horizontal scanning for the entire sample and vertical scanning for possible debonding regions determined from the horizontal scanning. The result of the imaging experiments can precisely reveal the size and position of the debonding regions, the maximum relative error of the centre position of the defect is 7.5% and the maximum relative deviation of the dimensions is 16.0%. This imaging method can serve as a reference for debonding imaging in composite plates. [ABSTRACT FROM AUTHOR]

Although various simplified models can capture size effects of composite laminated micro beam and plate by combining new modified couple stress theory, there is no benchmark to access the accuracy of predicting size effects in those models. Therefore this paper develops a quasi-3D model based on new modified couple stress as a benchmark for analyzing thermal size effects of composite laminated micro plate, and also proposes two simplified quasi-3D models with assumptions out of computational cost at the same time. By a classical example of simply-supported micro laminated square plate, several conclusions can be got from numerical results. For the present quasi-3D model under non-uniform temperature loading, (i): the model is capable to capture size effects of composite laminated micro plate, (ii): discovering a law to define the boundary size between micro and macro laminated plate, which is important for the engineering applications; For the simplified quasi-3D models under uniform temperature loading, (i): As the material length parameter l decreases, the accuracy of both of models is rising gradually, (ii): The first simplified quasi-3D model may substitute the present quasi-3D model to predict thermal size-dependent behaviors of composite laminated micro plate, whereas the second simplified quasi-3D model is suitable to laminated micro plate for which span-to-thickness ratio is no less than 14. [ABSTRACT FROM AUTHOR]

AbstractThis paper presents an analytical model for the free vibration of composite laminated plates with arbitrary biaxial symmetric geometry under elastic boundary conditions, applicable to cross-ply fiber-reinforced composites. In this model, the domain segmentation integral method proposed by the authors is extended to the first-order shear deformation theory (FSDT) and the laminated plate theory. The energy integrals pertaining to the FSDT are analytically simplified by segmenting the integration domains and synthesizing orthogonal polynomial displacement functions over the plate domain coordinate intervals. This synthesis is achieved through the amalgamation of the penalty function method and the Gram-Schmidt orthogonalization process. Then, using the Rayleigh-Ritz procedure, a series solution for the free vibration problem of cross-ply fiber-reinforced composite laminated plates is obtained. The model provides an analytical mathematical relationship between the profile curve of composite laminated plates with arbitrary biaxial symmetric geometry and the strain energy, kinetic energy, and boundary potential energy during vibrational processes. The correctness and applicability of the method are validated by comparing the obtained results with those from the literatures. New results for laminated plates, such as hexagonal and astroid-shaped plates, were presented as references for future research. Taking a track shaped plate as an example, the effect of the number of layers on the vibration characteristics of cross-ply fiber-reinforced composite laminated plates with a certain thickness is studied. [ABSTRACT FROM AUTHOR]

As one of the high-strength structures of the aerospace composite panels, the bonding of the stiffened skins affects the mechanical properties of the overall structure. A nonlinear detection method based on subharmonic modulation is proposed in order to detect the debonding damage of composite stiffened structures in the present paper. The debonding damage interface is simplified to a two-degree-of-freedom nonlinear model using interface contact theory. The multi-scale method is employed to analyse the generation mechanism of subharmonic modulation. The experiment is performed on the composite stiffened plate. Then based on the frequency response function characteristics of in-situ piezoelectric actuator/sensor, both high- and low-frequency excitation signals are applied to the composite stiffened plate, and the debonding damage of stiffeners is identified by the subharmonic modulation component in the response signal spectrum. It is shown, both theoretically and experimentally, that the subharmonic modulation method can effectively detect the interfacial debonding damage of composite stiffened structures and is insusceptible to the interference of environmental noise and the inherent nonlinearity of materials. [ABSTRACT FROM AUTHOR]

AbstractThis paper studies the free vibration and harmonic response of Functionally Graded Graphene/Epoxy composite plates, considering the First Order Shear Deformation Plate Theory. The weight fraction of graphene variation along the thickness direction with graphene homogeneous dispersed in a polymer matrix. The effective Young Modulus of the plate is predicted by a new micro-mechanical model. The model includes the aspect ratio and weight fraction of nanoplatelets embedded into the matrix. The modal and harmonic of Graphene/Epoxy plates are obtained by the Boundary Element Method formulation for composite plates. The Young modulus calculated from the proposed micro-mechanical model highly agrees with those obtained from experimental results reported in the literature. Results demonstrate a high correlation of the micromechanical model with experimental results and other analytical models. Graphene weight fraction and ratio aspect increase the effective Young modulus of the composite. Boundary Element results show high agreement with Finite Element solutions. Numerical results for modal and harmonic analysis show concentrating graphene near the top and bottom surfaces of the plate is the most effective way to reinforce the plate for increased natural frequencies. The results demonstrate the BEM formulation and micromechanical model can be used as reliable engineering tools for the vibrational analysis of functionally grade graphene composite plates. [ABSTRACT FROM AUTHOR]

In recent years, the use of hybrid composites, in which natural fibers combine with synthetic fibers, in place of composite structures consisting only of synthetic fibers has become increasingly popular due to growing environmental concerns and the need to develop sustainable, more lightweight, recyclable materials required for engineering applications. In this regard, the present paper is an attempt to show the usage of sitka spruce as an alternative to synthetic E-glass fiber and natural flax fiber in design of interply hybrid composite structures in terms of fundamental frequency, buckling resistance and weight. The single-objective and multi-objective approaches are considered to acquire optimum design for non-hybrid and hybrid structures. The modified versions of the optimization methods Differential Evolution (MDE), Nelder Mead (MNM) and Simulated Annealing (MSA) algorithms are considered to solve problems. The results show that the optimum design of the hybrid graphite/epoxy-sitka spruce laminated plate to obtain the structure having a more lightweight (e.g., 53%), higher frequency (e.g., 65%) and buckling resistance (e.g., 90%) was computed and compared with those of the hybrid graphite-flax/epoxy, neat sitka spruce, neat flax/epoxy and neat glass/epoxy laminated composite plates. [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]

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]

The aim of this paper is to use the smoothed particle hydrodynamics (SPH) technique (in Ansys Autodyn), to create a more physically realistic 2 D numerical model for the simulation of explosive welding of Titanium with Aluminum alloy Al7075-T6. The flyer plate was made of titanium, while the base plate was made of Al7075-T6. The Al7075-T6 plate served as the foundation for the majority of the jet's components. The majority of the jet's components were built on top of the Al7075-T6 plate. The jet flew at a speed of 1100 m/s, as anticipated by the model. In addition, the pressure at the explosion site was insufficient to bind the two plates. As a result, a unique tiny region of plastic strain formed at the impact zone. Despite the fact that the two plates were facing opposite directions, there were no signs of shear forces between them. Due to severe plastic deformation and localised melting of the parent plates, the interface shape changed from straight to wavelike as the detonation wave moved across it during the simulation. Both alloys behave like fluids, resulting in the formation of a wavy morphology with vortices, which is in good agreement with the previous studies. [ABSTRACT FROM AUTHOR]

Here, the basic formulation of nonlocal strain gradient theory (SGT) and sinusoidal shear deformation theory (SSDT) are used to analyze the free vibration behavior of functionally graded graphene nanoplatelets reinforced piezoelectric composite (FG-GPLRPC) microplate. To provide a realistic model based on the Kelvin Voigt model, the material properties of the structure are assumed to be viscoelastic. The viscoelastic FG-GPLRPC microplate is resting on the orthotropic visco Pasternak foundation and is exposed to the electromagnetic field. Four different patterns of functionally graded distributions of GPLs, uniform distribution, and non-uniform distributions such as FG-A, FG-O, and FG-X are considered. The effective Young's modulus, density, and Poisson's ratio of FG-GPLRPC microplate are determined based on the Halpin–Tsai micromechanics model and the mixture rule, respectively. Finally, Hamilton's principle is applied to obtain the equations of motion. The simply supported plate is assumed to study the dimensionless eigenfrequency with the analytical approach. The results are compared with other published papers to show the validity of the proposed approach. It is seen that growing the aspect ratio leads to about 33% increase and decrease in the system frequency for high and low damping coefficient values, respectively. [ABSTRACT FROM AUTHOR]

The paper aims to develop a finite element methodology to deal with vibrations and buckling of laminated thin plates subjected to thermal and hygroscopic effects, once a second-order strain gradient theory is included to overcome the limitations of conventional elasticity and to capture nonlocal phenomena. The numerical scheme takes advantage of Hermite approximation for both membrane and bending primary variables, since the strain gradient introduces higher-order derivatives of the nodal displacements. Its versatility is proven by dealing with general lamination schemes and arbitrary boundary conditions. The analyzed configurations cannot be solved analytically. [ABSTRACT FROM AUTHOR]

This paper addresses the effects of uncertainties on the optimal design of trusses and laminated composite plates. Uncertainties are considered in the design variables and material properties. Structural optimization is performed using the failure theory as a constraint, coupled with particle swarm optimization (PSO). Three different optimization approaches are utilized: (i) Deterministic optimization (ii) Reliability-based design optimization and (iii) Robust design optimization. A comparison is conducted between the aforementioned approaches based on the probability of failure. Monte Carlo simulation is performed to obtain the probability of failure. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the wave propagation analysis of multi-scale hybrid nanocomposite plates by considering the influences of the aggregation of the nanoparticles. For the constituent materials of the plate, a polymeric matrix is supposed to have macro- and nano-reinforcements dispersed in it. The well-known micromechanical methods, such as Eshelby-Mori-Tanaka model and the rule of the mixture, are exerted to compute the effective material properties of the nanocomposite plate. Also, a refined higher-order shear deformation theory is implemented to obtain the motion relations. Besides, the governing equations are derived by employing the principle of Hamilton. Then, the analytic method is used to solve the obtained governing equations of structure and finally wave frequency and phase velocity are calculated. The effects of the various parameters on the variation of phase velocity and wave frequency of the multi-scale nanocomposite plates are examined. The presented results demonstrate that the mechanical response of the system can be decreased, while the nanotubes are covered by clusters. [ABSTRACT FROM AUTHOR]

This paper addresses the influence of material and fabrication uncertainties on natural frequencies of curvilinear fiber laminate. Material properties and fiber orientation are considered uncertain. The sensitivity of input parameters to natural frequencies is obtained using high-dimensional model representation tool, and the results are compared with Monte Carlo simulation. This sensitivity pattern is established through various parametric studies. Highly sensitive parameters are identified and analyzed. Further stochastic analysis of natural frequencies of curvilinear fiber laminate is performed using polynomial neural network. The accuracy and efficiency of polynomial neural network are compared and conclusions are drawn. [ABSTRACT FROM AUTHOR]

An analytical approach is developed in this paper to investigate the wave propagating in graphene oxide powder (GOP) reinforced nanocomposite plates under thermal loading. The plate is embedded on a two parameter elastic substrate to make this research more realistic. The structure is exposed to thermal loadings with various temperature rises such as sinusoidal temperature rise (STR), linear temperature rise (LTR) and uniform temperature rise (UTR). The governing differential equations are derived via incorporation of the Hamilton's principle and refined higher order plate theory then solved analytically to obtain the wave frequency and phase velocity of the GOP reinforced nanocomposite plate. The GOPs are dispersed in a polymeric matrix through the thickness of the plate by considering different functionally graded (FG) patterns. Moreover, the effective material properties of the structure are predicted on the basis of Halpin–Tsai micromechanical scheme. Furthermore, the accuracy of the present model is verified with previous works and also the influences of various parameters on the wave propagation behavior of the structure are covered too. The graphical results declare that wave propagation in GOP reinforced nanocomposite plates dramatically depends on these parameters. [ABSTRACT FROM AUTHOR]

Understanding the progressive failure of laminated composite plays an important role in the structural integrity analysis of a structure. Continuum damage mechanics-based approach is one of the powerful tools to analyze the failure of laminated composite structures. The present paper investigates the damage evolution and progression in laminated composites with a hole under flexural loading. The presence of high-stress concentrations along with the free edge stresses at the vicinity of the hole in laminated composite leads to complex failure mechanisms. The influence of the change in thickness and lamina configuration on the strength characteristics is presented. [ABSTRACT FROM AUTHOR]

This paper investigates the thermo-electro-mechanical effects in the nonlinear response of piezoelectric laminated plates exposed to thermal and/or mechanical fields. The mechanics incorporate a) the direct piezoelectric effect through the coupling between electric-mechanical fields, b) the pyroelectric effect through the coupling between electric-thermal fields, and c) the geometric nonlinear effects due to large rotations and initial stresses. Building upon the nonlinear multifield mechanics an eight-node plate finite element is developed to discretize the generalized coupled nonlinear equations, which are subsequently linearized and iteratively solved, using the Newton-Raphson technique. Numerical evaluations demonstrate the capability of the present model to capture both of direct piezoelectric and pyroelectric effects in the nonlinear electromechanical response of piezoelectric composite plates, exposed to thermal and/or mechanical fields. The influence of direct piezoelectric and pyroelectric effects on thermal buckling and postbuckling response of various piezocomposite plates, is investigated. The possibility of pyroelectric effect to promote thermal buckling of piezocomposite plates with attached sensor patches is also quantified. The influence of thermo-electro-mechanical effects on the nonlinear response of smart composite plates, subject to either uniform or gradient temperature variations is finally illustrated. [ABSTRACT FROM AUTHOR]

In this paper, a sandwich composite plate with tunable magneto-rheological (MR) fluid core is utilized for analyzing the wave propagation. Sandwich composite plate is made of three layers consisting of the base layer, MR layer and the limiter layer. MR layer is embedded within the base and the limiter layers. Moreover, the upper and the lower layers are made of the elastic materials. This structure is also located on a viscoelastic substrate. At first, for achieving the governing equations of motion, Hamilton's principle and classical plate theory (CLPT) are utilized. Then, exerting an analytical solution, the wave frequency and phase velocity of the propagated waves can be gained by solving eigenvalue problem. By investigating the effect of the magnetic field, the results emphasize that the magnetic field intensity is most important factor for changing the value of the wave dispersion characteristic. Besides, results indicate by enhancing the core-to-top layer thickness ratio, the wave frequency decreases because MR fluid core is softer in comparison to the elastic layers, Hence, MR fluid core operates similar damper. At the end, the effect of the other parameters such as thickness of MR layer, Winkler, Pasternak and damping coefficients are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, local damping behaviour of S0 ultrasonic Lamb mode is investigated to determine the reason of amplitude reduction of signals come from a rich resin defect in a composite plate. A four-layer woven glass fibre-epoxy (WGF/epoxy) composite plate, containing a predefined rich resin area as the damage, has been manufactured and inspected with S0 Lamb mode via through transmission and pulse-echo method. Results have shown that there is a considerable amplitude reduction in the transmitted wave while a negligible damage reflected wave has been captured in the related receiver. An experimental based method has been employed in order to extract Rayleigh damping coefficients for the healthy composite plate, followed by a novel methodology to evaluate the damping coefficients at the defected area. Having calculated Rayleigh damping coefficients for both damaged and undamaged areas of the composite plate, several finite element simulations have been carried out, in order to quantify the wave amplitude reduction due to attenuation at the damage. The Amplitude Reduction Ratio (%ARR), obtained from numerical simulation matches closely with experimental ARR, represents that the proposed method for Rayleigh damping coefficients evaluation at the rich resin area can be used for further rich resin defect investigations. [ABSTRACT FROM AUTHOR]

The paper proposes a multi-scale uncertainty quantification framework of composite laminated plates. The micro and macro uncertainty parameters are represented by random and interval variables according to available uncertainty information. The data-driven Polynomial Chaos Expansion model is constructed, where polynomial coefficients of random variables are determined based on their high-dimensional statistical information, and coefficients of interval variables are calculated using sampling analysis method. The proposed framework is applied for multi-scale buckling analysis, natural frequency calculation and reliability estimation. The comparison results with Monte Carlo Sampling method demonstrate the computational superiority of the proposed algorithm to achieve high accuracy in multiple conditions. [ABSTRACT FROM AUTHOR]

This paper defines in-plane displacement functions of a composite lattice rectangular plate, which is assumed to be a Kirchhoff-Love plate. It presents an approximate method based on the continuous model of conducting a progressive failure analysis for predicting material failure and post-failure behavior of the composite lattice rectangular plate with various boundary and load conditions. To define the approximate method, we use the Ritz method and Hashin's failure criteria. The validity of the present method is verified by comparing the results of the finite element analysis. Finally, we perform parametric and sensitivity analyses to investigate the effects of the design parameters on the failure characteristics of the composite lattice rectangular plates based on the present method. The results allow a database to be obtained on the structural characteristics of composite lattice rectangular plates. Consequently, it is concluded that the present method is well suited to progressive failure analysis of composite lattice rectangular plates due to their relative simplicity and computational efficiency. [ABSTRACT FROM AUTHOR]

A composite sandwich structure can improve flexural rigidity and can decrease the weight of a composite laminated plate by 30%. However, it implies significant uncertainty within the construction process of its material properties when compared to other regular metals. Therefore, it is necessary to consider a probabilistic design method based on reliability. This paper calculated the probabilistic margin of safety of a simplified composite sandwich fuselage in order to examine that the classic design method utilizing the safety factor does not ensure the safety of the structure. Reliability-based design optimization (RBDO) was conducted for efficient calculation by using proposed RBDO by moving probability density function (RBDO-MPDF) method in this paper. Crude Monte-Carlo Simulation was used to calculate the probability density function. The results of this paper will be applicable to the improved design methods that ensure the structural reliability and maximized efficiency within the RBDO process. [ABSTRACT FROM AUTHOR]

This paper proposes a new zig-zag function to develop the refined sinusoidal theory. A refined sinusoidal shear deformation theory can be obtained by including the proposed zig-zag function and meeting the traction-free boundary conditions on the top and the bottom surfaces. Governing equations and boundary conditions are obtained by using the principle of virtual displacement. Using Navier's method, analytical solutions are presented by solving the boundary value problem. By investigating the typical bending problems of laminated composite and sandwich plates, the effect of various parameters like aspect ratio, thickness ratio and material properties on the bending response of plate is studied in detail. Comparison of the present results with the three-dimensional elasticity solutions and the results calculated using other models published recently in the literature shows that the proposed theory can yield accurately the displacements and stresses of multilayered composite and sandwich plates. Moreover, the accuracy of the displacement and stresses are not impacted by the number of layers and the material properties. [ABSTRACT FROM AUTHOR]

This paper reports an improved analytical solution for analysis the problem of interface stresses in functionally graded beam (FGB) strengthened with bonded hygrothermal aged composite plates. The material properties of the functionally graded beam are supposed to vary according to power law distribution of the volume fraction of the constituents through the beam thickness. The obtained results are compared with the existing solutions in the literature to verify the validity of the new analytical approach. It is found that the inhomogeneities play an important role in reducing the stress concentrations along bi-material interfaces. Finally, a parametric study was carried out to show the effects of the fiber volume fraction, the hygrothermal effect, and some design variables, e.g. thickness of adhesive layer and FRP plate on the magnitude of maximum shear and normal stress. [ABSTRACT FROM PUBLISHER]

This paper presents the free vibration analysis of a variable stiffness laminated composite sandwich plates. The fiber orientation angle of the face sheets (Skin) is assumed to vary linearly with the x-axis. The problem formulation is based on the higher-order shear deformation plate theory HDST C0 coupled with p-version of finite element method. The elements of the stiffness and mass matrices are calculated analytically. The sandwich plate is presented with a uniform mesh of four p-elements and the convergence properties are achieved by increasing the degree p of the hierarchical shape functions. A calculation program is developed to determine the fundamental frequencies for different physical and mechanical parameters such as plate thickness, core to face sheets thickness ratio, orientation angle of curvilinear fibers and boundary conditions. The results obtained show a good agreement with the available solutions in the literature. New comparison study of vibration response of laminated sandwich plate between the straight and curvilinear fibers is presented. [ABSTRACT FROM AUTHOR]

The second-order statistics of critical stress intensity factor (SIF) of single edge notched fiber reinforced composite plates with random system properties and subjected to uniaxial tensile loadings is investigated. This paper is an extension of reference (Lal and Kapania, 2013) by the present authors by considering more number of input random system parameters for higher accuracy. A C0 finite element method based on a higher-order shear deformation plate theory using displacement correlation method via isoparametric quarter point element is proposed for basic formulation. A stochastic finite element method using first-order perturbation technique and Monte Carlo simulation (MCS) is employed to examine the mean, coefficient of variance, and probability density faction of critical first mode SIF. The effect of different fiber orientations, crack length, plate thickness, a number of layers, and the lamination schemes with random system properties on the statistics of SIF of single edge crack laminated composite plate is evaluated. The tensile failure load is predicted using Hashin's failure criteria. The present approach is validated with results available in literature and by employing independent MCS. [ABSTRACT FROM AUTHOR]

This paper presents the free vibration analysis of a composite laminated square plate with complicated cutout. The problem formulation is based on the higher order shear deformation plate theory HDST C0 coupled with a curved quadrilateral p-element. The elements of the stiffness and mass matrices are calculated analytically. The curved edges are accurately represented using the blending function method. A calculation program is developed to determine the fundamental frequencies for different physical and mechanical parameters such as the cutout shape, plate thickness, fiber orientation angle, and boundary conditions. The results obtained show a good agreement with the available solutions in the literature. New results for the fundamentals frequencies of a composite laminated plate with complicated cutout are presented. [ABSTRACT FROM AUTHOR]

This paper presents the free vibration analysis of a variable stiffness composite laminate (VSCL) square plate with circular cutout. Although the h-version of the finite element method is quite attractive, it could not be used in the VSCL plate. This is due to the difficulties associated with the inter-element continuity for the curvilinear fibre and the fact that the circular cutout cannot be represented accurately. To overcome this problem, a new C0 enriched curved quadrilateral p-element is developed based on the first-order shear deformation theory, in which the transformed reduced stiffness elements are computed exactly within the stiffness matrix, and the curved edges are represented accurately using the blending function method. The convergence properties of the proposed p-version and the results of the numbers of test problems are in good agreement with the results of the literature. The natural frequencies are examined by considering the parabolic fibre orientation, radius of the circular cutout, the plate thickness and the boundaries conditions. It is found that the variation of the fibre orientation have significant effect on natural frequencies, especially for plates with large circular cutout. [ABSTRACT FROM AUTHOR]

In this paper, finite element method is employed to study the free vibration response of the rotating pretwisted carbon nanotube-reinforced composite cylindrical shell in thermal environment. The shells are reinforced by single walled carbon nanotubes (SWCNTs) and the material properties of SWCNTs are considered to be temperature dependent. The dynamic equilibrium equation is derived from Lagrange's equation for moderate rotational speeds for which the Coriolis effect is neglected. Parametric study is performed to investigate the effects of pretwist angles, temperature rise, rotational speed, and volume fraction of CNTs. In addition to this, the representative mode shapes are also presented. [ABSTRACT FROM AUTHOR]

Shape memory alloys as a kind of smart materials, have two unique characteristics entitled shape memory and pseudoelastic effects. In this paper, a nonlinear dynamic analysis of multilayered composite plate embedded with pre-strained SMA wires under thermal condition is implemented considering both effects of SMAs simultaneously, for the first time. The constitutive equation proposed by Brinson is used for modelling the behaviors of SMA wires. In this work, equations of motion are derived in the framework of Carrera's Unified Formulation, for robust analysis of the problem. In this regard, the nonlinear strains are employed for modelling the thermal effects and also the effect of recovery stresses in the SMA wires. In this study not only the material properties are instantaneous variable with respect to the time and location, but they are also unknown, which make the problem more complicated. For this aim, a transient nonlinear finite element in conjunction with incremental iterative algorithm proposed by the author is employed, in order to solve the equations. Results show that upon the thermal condition, the recovery stress is generated in the SMA wires and therefore reduce the amplitude of a damped response of the plate. One conclusion from this study is that, in contrast with many studies reported before, it cannot be always say that the stress recovery in SMA wires is increased with increasing the pre-strain of SMA wires. In other words, for a specified increasing in temperature, only a limit amount of pre-strain comes back to its original shape and not more. Also, several numerical examples upon effect of different thermal condition, different volume fraction of SMA wires and different boundary conditions have been analyzed. [ABSTRACT FROM AUTHOR]

PHOTO (COLOR) This Special Issue in the Mechanics of Advanced Materials and Structures (MAMS) presents a collection of 12 original journal articles and 1 review article to honor our dear colleague and friend, Dr. Junuthula N. Reddy of Texas A & M University for receiving the 2019 ASME Timoshenko Medal. The review article of Romanoff et al. ( I A review on non-classical continuum mechanics with applications in marine engineering i ) discusses representative problems from different length scales of ship structural design from a non-classical continuum mechanics approach. [Extracted from the article]

The paper deals with the effect of manufacturing imperfections in fiber orientations on the optimum design of laminate plates exposed to compression load. It is assumed that each dimensional imperfection cannot exceed one of two accepted values, called tolerances. In general, these are the largest allowed deviations of the design variable from its nominal value. The incorporation of tolerances is achieved by diminishing the limit values of state variables by the product of assumed tolerances and appropriate sensitivities. Therefore, the given method allows the introduction of tolerances into design in a relatively simple way and ensures safe results. The presented approach is a deterministic approximation of an exact stochastic solution of the problem. The paper is illustrated with two examples of the rectangular laminated plate design. The first one is maximization of buckling load for a given plate thickness. The second one is minimum weight (thickness) design for a given load. Numerical results show the reliability-based design to be important for structural safety when compared to the approach where tolerances are not considered [ABSTRACT FROM AUTHOR]

The electromechanical impedance damage detection method for composite plates is presented in this paper using piezoelectric materials. The structural damage is characterised by the admittance signals obtained from the piezoelectric materials. The results obtained in this study show that the resonance frequency will change if the damage occurs. The maximum amplitude value of the conductance without damage is larger than that with damage. The amplitude value increases as the radius of the damage holes increases. Furthermore, according to the admittance signals of the two PZT patches, the PZT is more sensitive to the damage when it is closer to the damage. The root mean square deviation damage index based on the admittance signals can also effectively reflect the damage information in the composite plate. [ABSTRACT FROM AUTHOR]

A new model of microplate is used to evaluate the vibrational response of a size-dependent three-layered sandwich structure, including functionally graded (FG) composite core by sinusoidal shear deformation plate theory. Also, this FG core is reinforced by graphene nanoplatelets (GPLs) and embedded between piezo-electromagnetic (PEM) face sheets. The matrix of the core is made of Epoxy and the extended rule of mixture (ERM) besides Halpin–Tsai model is chosen to predict the mechanical properties of the nanocomposite core. Moreover, BaTiO3-CoFe2O4 composition is considered as constituting material of PEM face sheets. Furthermore, the visco-Pasternak substrate is used to carry the whole structure. The aforementioned theories are employed efficiently to obtain motion equations. Finally, the vibrational response of the described model due to the different parameters' variations is presented in tables and figures. Based on the results, temperature difference leads the structure to become stiffer and accordingly reduces the frequency. Moreover, using a square basis for a sandwich structure makes the lowest frequency and consequently stiffness. [ABSTRACT FROM AUTHOR]

Carbon friction linings are increasingly being used for clutches in industrial applications because of their excellent properties in terms of friction behavior, temperature resistance, and wear. Due to safety-relevant use of these clutches, their failure must be avoided and thus the damage behavior must be investigated. In this article, the spontaneous damage behavior of two multi-plate clutches (FS1, FS2) with different carbon friction linings (a woven and a composite carbon friction lining) is investigated experimentally. For this purpose, the mechanical load was increased step by step in step tests with brake shifting and the damage progression was documented by regular dismounting of the clutch. For the FS1 friction system with a composite carbon friction lining, the initial damage was local discoloration of the steel plates due to oil cracking products. The failure of the system occurred in friction system 1 due to shrinkage of the steel plates on the inner carrier. For the FS2 friction system with a woven carbon friction lining, the initial damage was also discoloration of the steel plate. With increasing load there was displacement of the friction lining pads. The failure of the system was caused by the detachment of the friction lining from the carrier plate. The research results highlight the potential for improvement of the multi-plate clutch in terms of a more temperature-resistant adhesive layer between the carrier plate and the friction lining. In addition, the steel plates must be heated evenly in the radial direction, which can be achieved by optimizing the geometry. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the SH wave propagation in a layered piezoelectric (PE) and piezomagnetic (PM) plate with an imperfect magnetoelectroelastic interface. A linear magnetoelectroelastic spring model is used to describe the weakness of the imperfect interface. On the basis of this model, dispersion curves and mode shapes of the SH waves are computed. In particular, a PZT-5A/CoFe2O4 composite plate is considered in the numerical examples to calculate the dispersion curves and the mode shapes for different combinations of the magnetic, electrical and elastic spring constants. The effects of the layer thickness ratio and the electric-magnetic boundary conditions on the dispersion curves are discussed in details. Our results show that for a general weak bonding case, the high modes of the dispersion curves are not monotonous in the range of small wave numbers. With the layer thickness ratio increasing, the wave velocities of the SH waves increase. The electric boundary conditions mainly determine the dispersion curves of the SH waves in the case of a small layer thickness ratio, i.e. a large thickness of the PE layer. The present results have relevant applications in the nondestructive testing and evaluation of the layered PE/PM plate-like wave devices. [ABSTRACT FROM AUTHOR]

Buckling and postbuckling behaviors of two models of sandwich plate reinforced by carbon nanotubes (CNTs) resting on elastic foundations and subjected to uniaxial compressive and thermomechanical loads are investigated in this paper. Material properties of all constituents are assumed to be temperature dependent and effective properties of CNT-reinforced composite layer are determined according to extended rule of mixture. Governing equations are established within the framework of first-order shear deformation theory taking into account von Kármán nonlinearity, initial geometrical imperfection, plate-foundation interaction and tangential elastic constraints of unloaded edges. Three types of loading are considered including uniaxial compression, preexisting thermal load combined with uniaxial compression and preexisting mechanical load combined with thermal load. Approximate analytical solutions are assumed to satisfy simply supported boundary conditions and the Galerkin method is used to derive nonlinear load-deflection relations from which buckling loads and postbuckling equilibrium paths are determined. The most important findings are that tangential constraints of unloaded edges significantly lowers buckling loads and postbuckling load capacity of sandwich plates and, in contrast, buckling loads and postbuckling strength are considerably enhanced as sandwich plate is constructed from CNT-reinforced composite core layer and homogeneous face sheets. [ABSTRACT FROM AUTHOR]

In this paper, a new analytical model for behavior of carbon nanotubes reinforced composite plates under low velocity impact has been presented. Nanotubes aligned, straight and randomly oriented are distributed on rectangular simply supported composite plate. The Mori–Tanaka model is used to obtain effective mechanical properties of composites reinforced with nanotubes consisting of aligned, straight and randomly oriented carbon nanotubes embedded in a polymer matrix. The analytical model based on the first-order shear deformation theory and spring-mass model. The results of analytical model are compared with the results of low velocity impact on fiber-reinforced polymer composites. The results show that the deflection and energy absorption of plate in a randomly oriented distribution is more than aligned straight of carbon nanotubes in the composite layers. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear analysis for large amplitude free vibration of laminated composite plates is developed using higher-order shear deformation theory. The effect of all higher-order terms arising from nonlinear strain-displacement relations are included in the formulation and present plate theory exhibits traction-free surface of the laminated plate in von-Karman sense. A finite element procedure considering a C° continuous isoparametric nine-node rectangular element is implemented for nonlinear model. The accuracy of the theory is validated with some available theory for different aspect ratio, modular ratio, number of layers, ply orientations, etc. through some numerical examples. [ABSTRACT FROM AUTHOR]