Composite Face Layers Research Articles

Aeroelastic Stability and Design of Laminated Composite Sandwich MRE Plates Using Surrogate Metaheuristics Optimization

Sandwich composite materials with elastomeric cores and high-strength face layers have widespread applications in various engineering sectors as passive damping structural materials. This study examines the dynamic properties of sandwich plate with laminated composite face layers and smart magnetorheological elastomer (MRE) core under the action of the aerodynamic and hygrothermal loads. The dynamic model based on Kirchhoff’s plate theory is employed and the equations of motion are derived using Hamilton’s principle. The flow conditions are assumed supersonic and modeled by the first-order piston theory. The natural frequencies and aerodynamic pressure distributions are obtained from finite element model. Upon validating the model, the effects of various factors such as moisture, temperature and plate geometry on the critical aerodynamic pressure for different boundary conditions and magnetic fields are studied. Using these parametric data, a regression model is developed using Back-Propagation Neural Network to predict the critical aerodynamic pressure as a function of effective geometrical parameters. In order to enhance the aerodynamic stability, the critical aerodynamic pressure is maximized by the optimal selection of plate aspect ratio, face layer ply orientation sequence and core layer thickness ratio via the modified teaching–learning-based optimization (MTLBO) technique employing the trained neural network-based surrogate model. The approach is very convenient and it has been found that nondimensional aerodynamic pressure along with loss factor has improved almost twice. In the sensitivity analysis study, it is noticed that changes in aspect ratio around the optimal point have a relatively drastic effect on the critical aerodynamic pressure at all the face layer ply configurations.

Vibration assessment of dual core sandwich beam with a biomimetic lamellar honeycomb core and MWCNT reinforced facesheets

The usage of sandwich structures has been increasing in the field of defense, transportation, and aerospace applications due to the many advantages like, thickness to mass ratio, high bending stiffness, and strength. In this present work, the vibration assessment of the dual-core sandwich beam with biomimetic core and multiwalled carbon nanotube (MWCNT) reinforced composite face layers has been performed. The lamellar honeycomb (LHC) core is a biomimetic design developed here from the pistachio shell structure and manufactured by 3D printing process. The mechanical characteristics of biomimetic core are measured using an alternative dynamic technique and impulse excitation test was used to assess the material properties of MWCNT composite laminates. Using finite element software, a numerical model is created for a composite dual-core sandwich beam containing MWCNTs and a biomimetic core. The developed numerical model is validated with experimental and available literature results in terms of natural frequencies and it shows good agreements. Additionally, parametric studies are performed to investigate the natural frequencies of MWCNT composite dual-core sandwich beam with biomimetic cores for ply orientation angles, aspect ratio, and support conditions. The MWCNT reinforcement in the facesheets and LHC core enhances the structural performance and stiffness of the laminated composite dual-core sandwich beam. This research will provide the valuable insights to engineers and scientists for the construction of large capacity ships and race boat structures.

Vibrational behavior of a 3D printed biomimetic dual‐core composite sandwich beam: An experimental and numerical study

AbstractComposite sandwich structures have been used in various applications like aerospace, automotive, and maritime sectors. The process of identifying the core design and the selection of a prominent core is crucially important in sandwich structures. In this study, biomimetic core development and vibration responses of composite sandwich beams with a dual biomimetic honeycomb core are investigated. The composite face layers are fabricated by the hand lay‐up method, and the fused deposition modeling is used to 3D print the PLA honeycomb cores. Based on ASTM‐E1876 and the alternative dynamic approach, the face layer elastic properties and rigidity modulus of the cores are evaluated, respectively. The numerical simulation is used to predict the sandwich panels' natural frequencies and mode shapes and verified with experimental results. There was an excellent agreement between the calculated and experimental natural frequencies. Due to the presence of the core and enhanced rigidity modulus, the dual lamellar honeycomb core sandwich beam produces the highest natural frequencies among all‐composite sandwich beams, followed by the dual regular honeycomb, single lamellar honeycomb, and single regular honeycomb cores. The geometric parametric studies, including core thickness, length‐to‐breadth ratio, lamination schemes, support conditions, and transverse vibration responses were also analyzed for different sandwich patterns. As a result of this work, thick composite sandwich panels in aeronautical and marine structures can be replaced with dual biomimetic core structures. The study highlights the fact that the dual‐core sandwich beam provided greater modal frequency than the single‐core beam with the same weight proportions.Highlights Pistachio nut shell‐based biomimetic honeycomb core has been developed. Alternative dynamic approach is used to find sandwich‐core shear properties. Lamellar‐infused biomimetic model yields higher shear modulus and stiffness. Dual‐core beam having high flexural stiffness enhances the natural frequency. Various parametric studies were analyzed for different sandwich patterns.

Bending and eigenfrequency analysis of glass fiber reinforced honeycomb sandwich shell panels containing graphene-decorated with graphene quantum dots

The present study employs a finite element (FE) formulation to examine the free vibration and bending analyses of sandwich shells made of a glass fiber reinforced polymer (GFRP) composite honeycomb core and graphene decorated with graphene quantum dots (GDGQD) reinforced by GFRP composite face layers. The mechanical characteristics of the GFRP composites with GDGQD reinforcement were evaluated using experimental tests. The FE formulation was developed to compute the vibration and bending responses of the sandwich shells via MATLAB software. The Lagrange method is used for dynamic analysis, whereas the principle of potential energy is used for static analysis. The FE model's validity is compared to numerical data reported in the literature in terms of frequencies and deflection, and the results demonstrate excellent agreement. The impacts of the end conditions, core-to-facesheet thickness ratio, curvature ratios, and weight percent of GDGQD are studied further in relation to the bending and dynamic properties of GFRP sandwich shells.

Application of point interpolation mesh-free method for magneto/electro rheological vibrations of sandwich conical panels

Magneto-rheological or electro-rheological materials, due to many possible control-based applications have acquired lots of attention. So, in the present work, as the first attempt, a point interpolation method is exploited to evaluate vibrations of the sandwich conical panel with magneto-rheological or electro-rheological core, and composite face sheets. Through the linear viscoelastic hypothesis, and in the pre/post-yield zones, the correlation of shear stress-strain for magneto-rheological fluid is applied. The equilibrium equations are governed by the principle of Hamilton in addition to the first-shear deformation (FSD) hypothesis. By satisfying the compatibility equations, the interfaces of the core along with composite face layers are simulated. Upon polynomial basic function, shape functions together with the approximate form of the displacement field are constructed. The correctness of the computational approach is certified through the analogical investigation. The results show that number of face layers, thickness, the pattern of composite layers, weight fraction, and electric/magnetic field, together with the geometry of the conical panel have an imperative impact on the system's natural frequency in addition to the loss factor index.

Prediction of nth-order derivatives for vibration responses of a sandwich shell composed of a magnetorheological core and composite face layers

Since their mechanical qualities may be adjusted by an applied magnetic field, designers have shown considerable interest in Magneto-Rheological (MR) materials, a recently discovered class of smart materials. For the first time, this research details the vibration stability related to a sandwich shell composed of an MR core and graphene nanoplatelets (GPLs) reinforced composite (GPLRC) face layers. Residual stresses under in-plane loading contribute to the geometric stiffness considered here. This paper uses a mixed and improved Halpin-Tsai hypothesis to characterize the effective material features of GPLRC face layers. Based on the linear viscoelastic scheme and Hamilton's principle, the governing equations related to the present assembly are established. As an added bonus, compatibility equations are included to aid in providing an accurate model of the sandwich. The linked structure's governing equations under a variety of boundary conditions are solved using the wave propagation technique (WPA). Here, the authors focus on validating a Deep Neural Network (DNN) strategy for different kinds of Mean Squared Error (MSE). In conclusion, the outputs illustrate that the GPL weight fraction, viscoelastic foundation, and form of the structure are crucial in establishing the vibration stability and loss parameter factor related to the sandwich shells.

Dynamic behaviors of composite leaf springs with viscoelastic cores

A leaf spring is a simple form of spring commonly used for the suspension in wheeled vehicles. Due to their high strength to weight ratio, high stiffness, and high impact energy absorption, fiber-reinforced composite leaf springs gain considerable interest recently as a potential alternative to conventional leaf springs with relatively high weight. In the present study, a novel composite leaf spring consists of two composite face layers, and a soft and flexible viscoelastic core is proposed. Employing viscoelastic materials in structures reduces undesirable vibrations leading to fatigue and damage of structures. A numerical method is used to design and analyze composite leaf springs with a viscoelastic core using the Abaqus software package. Results are compared with those from well-known analytical methods, finite element methods, and experiments. Results show that the proposed novel composite leaf spring can withstand the stresses caused by static and impact forces, reduce post-impact vibrations, and prevent undesirable system vibrations. The viscoelastic layer increases the strain energy capacity of proposed composite leaf springs compared to conventional composite leaf springs and enhances the composite leaf spring performance against bump impact.

Vibration characteristics and optimal design of composite sandwich beam with partially configured hybrid MR-Elastomers

The free and forced vibration characteristics of a sandwich beam with composite face layers and partially configured carbon nanotubes reinforced magnetorheological elastomer (hybrid MR elastomer) core is presented in this article. Higher order shear deformation theory (HSDT) based on finite element (FE) formulation is employed to derive the governing equations of motion of the partially configured hybrid MR elastomer sandwich beam. The efficacy of the present FE method is evaluated by comparing its numerical solutions with those reported in the literature. The effects of partial configurations, magnetic fields, and support conditions on the vibration characteristics of partially configured hybrid MR elastomer sandwich beams are discussed. Further, the structural optimization problem is formulated to identify the optimal positions for the hybrid MR elastomers and optimal face sheet ply orientations to maximize the vibration characteristics of the composite structures. The solution of the optimization problem, attained using the genetic algorithm (GA) coupled with FE formulations. The numerical results show that the location of the hybrid MR elastomer and optimal ply orientation have significant influences on the vibration and damping performances of the partially configured hybrid MR elastomer sandwich structures.

Free and forced vibration analysis of a sandwich beam considering porous core and SMA hybrid composite face layers on Vlasov’s foundation

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.

Dynamic and instability analyses of FG graphene-reinforced sandwich deep curved nanobeams with viscoelastic core under magnetic field effect

Based on the nonlocal strain gradient theory, the effect of an axial magnetic field on the free vibration and mechanical buckling responses of an FG graphene-reinforced sandwich deep curved nanobeam with viscoelastic core embedded in a viscoelastic medium is elucidated in this paper. The curved beam is also assumed to be exposed to axial external compressions. The volume fraction of the constituents of the composite face layers are presumed to be functionally graded through the thickness according to a layer-wise law. The material properties are calculated in the framework of Halpin-Tsai micromechanical scheme. Lorentz magnetic force is deduced employing electro-dynamic Maxwell's relations for a conducting body. According to a refined shear and normal deformations curved beam theory, the motion equations are introduced in the polar coordinates. Analytical solutions are obtained for the natural frequencies and critical buckling load of the viscoelastic sandwich curved nanobeams. By comparing the present results with the available data in the literature, the developed formulations are validated. Furthermore, other several numerical examples are performed to show the effects of different parameters including viscoelastic core thickness, magnetic field, structural and foundation damping factor, opening angle and graphene concentration on the frequency and buckling load of the viscoelastic sandwich curved beams.

Vibration and Damping Analysis of Sandwich Cylindrical Shells by the GDQM

This paper focuses on the vibration and damping analysis of three-layered sandwich cylindrical shells with stiff composite face layers and a viscoelastic core. The equations of motion and boundary conditions governing the free vibration are derived by using the Hamilton’s principle. Then, generalized differential quadrature method is used to solve these equations to obtain the natural frequencies and modal loss factors. Results are validated against the ones that already exist in the literature and performed finite element method analyses of current study. In addition, a parametric study is performed for a sandwich shell with carbon fiber–reinforced plastic face layers and a frequency-dependent viscoelastic core. A 10-parameter fractional derivative model is used to represent the viscoelastic behavior of the core layer. The effects of system parameters, that is, layer thicknesses, the orientation angle of the face layers, and the subtended angle on the vibration and damping characteristics of open cylindrical shells, are investigated in detail. The vibration and damping analyzes of sandwich shells with frequency-dependent viscoelastic core are performed for the first time to the best of the authors’ knowledge.

Structural optimization of tapered composite sandwich plates partially treated with magnetorheological elastomers

This study investigates the optimal locations of magnetorheological elastomer (MRE) segments in partially treated tapered composite MRE sandwich plates to maximize the natural frequencies and the loss factors. Various partially treated tapered composite MRE sandwich plate configurations are developed by dropping-off the plies longitudinally in top and bottom orthotropic (composite) layers with uniform core layer thickness. The core layer is made of natural rubber and MRE. The classical laminated plate theory is used to derive the governing differential equations of motion of the various partially treated MRE tapered composite sandwich plate configurations. The equations of motion are solved by using finite element formulation. Various cases of optimization problems are formulated and solved using genetic algorithm (GA) in order to obtain optimal locations to yield maximum natural frequencies and loss factors corresponding to the first five modes. The proposed methodology is validated by comparing the results evaluated in identifying optimal locations of MR fluid pockets filled in between uniform composite face layers, available in literature. It is observed that according to the user/designer requirements on achieving the optimal functions and their maximum value, the optimal locations of MRE pockets vary. It has also been demonstrated that the end conditions of the sandwich plate could play an important role in identifying the optimal locations of the MRE pockets. Further, it is observed that the optimal locations of MRE pockets are influenced by the ply drop off and resin locations. Hence it is concluded that the efficient design layout of a partially treated tapered composite MRE sandwich plate configurations would provide the guidelines for the designer to control the vibration effectively.

Application of linear vibration modeling of cross-ply composite plates with viscoelastic core

PurposeThe purpose of this study is to facilitate the engineering technical personnel to easily choose the appropriate vibration analysis model in the design of symmetry composite sandwich structure with composite face layers and viscoelastic core. Therefore, the applicable condition of two linear vibration models was obtained by considering the vibration analysis of three-layered sandwich structures.Design/methodology/approachEquilibrium equations of three kinds of vibration models were deduced using Hamilton’s principle and were solved using the closed-form Navier solution. Then, numerical results were compared with those reported in the literature to verify the accuracy of the deduced calculating formulas.FindingsThe applicable conditions of two linear vibration models are obtained by examining the influence of the ratio of length to total thickness (q) and that of viscoelastic thickness to total thickness (c) on the solutions. Two cases are considered about the applicable conditions of two linear vibration models based on the error analysis.Originality/valueThe paper obtains the application conditions of two linear vibration models by using error analysis for the first time and provides the reference for engineering staff to easily choose a suitable vibration model to design a symmetry composite sandwich plate.

Vibration analysis of curved composite sandwich beams with viscoelastic core by using differential quadrature method

This paper focuses on the vibration analysis of three-layered curved sandwich beams with elastic face layers and viscoelastic core. First, the equations of motion that govern the free vibrations of the curved beams together with the boundary conditions are derived by using the principle of virtual work, in the most general form. Then, these equations are solved by using the generalized differential quadrature method in the frequency domain, for the first time to the best of the authors’ knowledge. Verification of the proposed beam model and the generalized differential quadrature solution is carried out via comparison with the results that already exist in literature and the ANSYS finite element solution combined with the modal strain energy method. The effect of system parameters, i.e. layer thicknesses, the lamination angle of layers and the curvature on the vibration and damping characteristics of a curved sandwich beam with laminated composite face layers and a frequency dependent viscoelastic core is investigated in detail.

Dynamic characterization of tapered laminated composite sandwich plates partially treated with magnetorheological elastomer

This study investigates the dynamic performance of the partially treated magnetorheological elastomer tapered composite sandwich plates. Various partially treated tapered magnetorheological elastomer laminated composite sandwich plate models are formulated by dropping-off the plies longitudinally in top and bottom composite face layers to yield tapered plates as the face layers. The uniform rubber and magnetorheological elastomer materials are considered as the core layer. The governing differential equations of motion of the various partially treated magnetorheological elastomer tapered composite sandwich plate configurations are derived using classical laminated plate theory and solved numerically. Further, silicon-based magnetorheological elastomer and natural rubber are being fabricated and tested to identify the various mechanical properties. The effectiveness of the developed finite element formulation is demonstrated by comparing the results obtained with experimental tests and available literature. Also, various partially treated magnetorheological elastomer tapered laminated composite sandwich plates are considered to the study the effect of location and size of magnetorheological elastomer segment on various dynamic properties under various boundary conditions. The effects of magnetic field on the variation of natural frequencies and loss factors of the various partially treated magnetorheological elastomer tapered laminated composite sandwich plate configurations are analysed at different boundary conditions. Also, the effect of taper angle of top and bottom layers, aspect ratio, ply orientations on the natural frequencies of different configurations are analysed. Further, the transverse vibration responses of three different partially treated magnetorheological elastomer tapered laminated composite sandwich plate configurations under harmonic excitation are analysed at various magnetic fields. This analysis suggests that the location and size of the magnetorheological elastomer segments strongly influence the natural frequency, loss factor and transverse displacements of the partially treated magnetorheological elastomer tapered laminated composite sandwich plates apart from the intensities of the applied magnetic field. This shows the applicability of partial treatment to critical components of a large structure to achieve a more efficient and compact vibration control mechanism with variable damping.

Dynamic characterization of a laminated composite magnetorheological fluid sandwich plate

This study investigates the dynamic properties of a laminated composite magnetorheological (MR) fluid sandwich plate. The governing differential equations of motion of a sandwich plate embedding a MR fluid layer as the core layer and laminated composite plates as the face layers are presented in a finite element formulation. The validity of the developed finite element formulation is demonstrated by comparing the results in terms of the natural frequencies derived from the present finite element formulation with those in the available literature. Various parametric studies are also performed to investigate the effect of a magnetic field on the variation of the natural frequencies and loss factors of the MR fluid composite sandwich plate under various boundary conditions. Furthermore, the effect of the thickness of the MR fluid layer and the ply orientation of the composite face layers on the variation of the natural frequencies and loss factors are studied. The free vibration mode shapes under various boundary conditions of a MR fluid laminated composite sandwich plate are also presented. The forced vibration response of a MR fluid composite plate is investigated to study the dynamic response of the sandwich plate under harmonic force excitations in various magnetic fields. The study suggests that the natural frequency increases with increasing magnetic field, irrespective of the boundary conditions. The reduction in peak deflection at each mode under a harmonic excitation force with variation of the applied magnetic field shows the effectiveness of the MR fluid layer in reducing the vibration amplitude of the composite sandwich plate.

Buckling in Thin Walled Micro and Meso Structures of Lightweight Materials and Material Compounds

Modern materials and material compounds for application in lightweight structures exhibit, in addition to the use of constituents of high specific stiffness and strength, very special micro- and meso-structures. Typical representatives of such material compounds are sandwiches with thin homogeneous or composite face layers and structured core materials (for instance honeycombs and closed or open cell foams). The load carrying capacity of lightweight structures made of such materials and material compounds, respectively, is limited by a considerable number of rather different but interconnected instability modes occurring at length scales which are several orders of magnitude smaller than the size of the structural part. These non-global instabilities are the subject of the presented key-note paper.

Optimal design of sandwich and laminated composite plates based on the planning of experiments

Optimal design problems of sandwich plates with soft core and laminated composite face layers, and multilayered composite plates are investigated. The optimal design problems are solved by using the method of the planning of experiments. The optimization procedure is divided into the following stages: choice of control parameters and establishment of the domain of search, elaboration of plans of experiment for the chosen number of reference points, execution of the experiment, determination of simple mathematical models from the experimental data, design of the structure on the basis of the mathematical models discovered, and finally verification experiments at the point of the optimal solution. Vibration and damping analysis is performed by using a sandwich plate finite elements based on a broken line model. Damping properties of the core and face layers of the plate are taken into account in the optimal design. Modal loss factors are computed using the method of complex eigenvalues or the energy method. Frequencies and modal loss factors of the plate are constraints in the optimal design problem. There are also constraints on geometrical parameters and the bending stiffness of the plate. The mass of the plate is the objective function. Design parameters are the thickness of the plate layers. In the points of experiments computer simulation using FEM is carried out. Using this information, simple mathematical models for frequencies and modal loss factors for the plate are determined. These simple mathematical functions are used as constraints in the nonlinear programming problem, which is solved by random search and the penalty function method. Numerical examples of the optimal design of clamped sandwich and simply supported laminated composite plates are presented. A significant improvement of damping properties of a sandwich plate is observed in comparison with a simple plate of equal natural frequencies.

Vibration and damping analysis of a three-layered composite plate with a viscoelastic mid-layer

The natural frequencies and loss factors of a rectangular three-layered plate with a viscoelastic core layer and laminated face layers are considered. The equations of free vibration of the plate together with the corresponding boundary conditions are derived for a non-symmetric plate with general anisotropy of the face layers. A first order shear deformation theory is used to describe the deformation of the faces. Simplified forms of these equations, for a symmetric plate or for specially orthotropic face layers, are then discussed. Equations are also given for a model with no shear deformation in the face layers and all but transverse inertia terms neglected (simplified model). Results of numerical examples are presented for simply supported plates with specially orthotropic face layers. Complex eigenvalues are found numerically, and from these, both frequencies and loss factors are extracted. Comparison is made between the shear deformation and the simplified models, in the case of high modulus composite face layers.