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The bending behavior of COMPOSITEs SANDWICH PLATES with multi-layered laminated face sheets has been investigated, using a new four-nodded rectangular finite element formulation based on a layer-wise theory. Both, first order and higher-order shear deformation, theories are used in order to model the face sheets and the core, respectively. Unlike any other layer-wise theory, the number of degrees of freedom in this present model is independent of the number of layers. The compatibility conditions as well as the displacement continuity at the interface ‘face sheets–core’ are satisfied. In the proposed model, the three translation components are common for the all SANDWICH layers, and are located at the mid-plane of the SANDWICH plate. The obtained results show that the developed model is able to give accurate transverse shear stresses directly from the constitutive equations. Moreover, a parametric study was also conducted to investigate the effect of certain characteristic parameters (core thickness to total thickness ratio, side-to-thickness ratio, boundary conditions, plate aspect ratio, core-to-face sheet anisotropy ratio, core shear modulus to the flexural modulus ratio and degree of orthotropy of the face sheet) on the transverse displacement variation. The numerical results obtained by our model are compared favorably with those obtained via analytical solution and numerical/experimental, results obtained by other models. The results obtained from this investigation will be useful for a more comprehensive understanding of the behavior of SANDWICH laminates.

In the present article, a global-local theory with three-dimensional elasticity corrections is employed to trace the local and instantaneous variations of various displacement and stress components of SANDWICH and COMPOSITE PLATES. The governing equations are extracted based on Hamilton principle. One of the key features of the proposed theory is incorporation of the transverse flexibility of the core; a fact that is crucial when studying behaviors of thick or soft core SANDWICH PLATES. Since the transverse shear stresses are extracted based on the 3D elasticity theory, the interlaminar continuity condition of the transverse shear stresses is met. The verification results show that the presented finite element formulation is efficient and leads to accurate results, even for thick or soft core SANDWICH PLATES. A comprehensive parametric study is accomplished to evaluate effects of different parameters such as stiffness of the core material and boundary conditions. Finally, the obtained results verified by the available results existed in the literature.

In this paper the generalized differential quadrature method (GDQM) is presented for easy and effective bending analysis of COMPOSITE SANDWICH PLATES with symmetric angle-ply face sheets under static loading based on the first order shear deformation theory (FSDT). The bending behavior of COMPOSITE SANDWICH PLATES with various combinations of boundary conditions is studied. The effects of fiber orientation, ratio of thickness to length of the plate, the ratio of thickness of core to thickness of the face sheet are studied on the transverse displacement rotation about mid-plane and moment resultants. Comparisons are made with the existing solutions. The obtained graphs give very good results due to optimum design of SANDWICH PLATES. It has been found that a fast convergent rate can be achieved by the GDQM with non-uniform grids and very accurate results are obtained.

One of the common ways to reduce vibration in the structures is to add a thin viscoelastic material layer to the structure. By appropriate use of viscoelastic materials one may increase modal loss factor of the structure and reduce unfavorable structural vibration which is a main cause of fatigue and failure in the structures. In this paper, low velocity impact response of SANDWICH plate with magnetorheological fluid core is investigated. Hamilton principal is used to obtain the governing equation of motion for SANDWICH plate. Free vibration problem of the SANDWICH plate is solved using the Navier solution method.Classical lamination theory is used to analyze the mechanical behavior of the COMPOSITE laminate in the facesheet. Only shear strain energy of the core is considered and viscoelastic behavior of the MR material was described by complex shear modulus approach as a function of magnetic field intensity.Furthermore, analytical solution for impact force is obtained by a two degree of freedom spring mass model. For three different stacking sequence of face layers, contact for history and variation of maximum impact force and its corresponding time by magnetic field intensity is investigated. The results show considerable effect of variation in magnetic field intensity on maximum impact force and its corresponding time.

A new computational procedure based on two Spring-Mass-Damper-Dashpot (SMDD) and Spring-Mass- Damper (SMD) models representing contact behavior between the impactor and the plate are presented to study the low velocity impact phenomenon of SANDWICH PLATES comprising of a transversely flexible core and laminated COMPOSITE face-sheets. The interaction between the impactor and the plate is modeled with the help of a new system having three-degree of-freedom, consisting of spring-mass-damper-dashpot or spring mass- damper. The plate may be subjected to initial in-plane biaxial normal and shear stresses along the edges of the plate. Impact is assumed to occur normally over the top or the bottom face-sheets, at arbitrary location. The boundary conditions of the top and the bottom face-sheets are independent. The effects of transverse flexibility of the core and structural damping of the plate are considered in the proposed models. Based on these models, the analytic functions describing the contact force, the transverse deflections of the impactor and the plate are derived. The effects of some parameters such as plate aspect ratio, boundary conditions, initial in-plane biaxial stresses, and impact location are examined in details.

In this paper, natural frequencies of the SANDWICH PLATES with soft flexible core and COMPOSITE face sheets are obtained. Three-Dimensional (3D) finite element method (FEM) is used for constructing and analyzing of the SANDWICH PLATES to obtain their natural frequencies. Continuity conditions for transverse shear stresses at the interfaces as well as transverse flexibility and transverse normal strain and stress of the core are considered. The effects of plate dimensions such as aspect ratio and thickness ratio are studied. Also, different boundary conditions such as all edges clamped (CCCC), all edges simply supported (SSSS) and combined boundary conditions including (CFCF) are applied to the SANDWICH PLATES. Comparison of the present results in special case with those of the accurate plate theories confirms the accuracy of the proposed model.

Currently, COMPOSITE structures have many applications in various industries including aerospace, automotive, marine, and petrochemicals. In most of these applications, the structure is under dynamic and static loads and it can cause buckling, vibration, and fatigue. Therefore, the static and dynamic analysis of these structures is essential in order to understand their characteristics, including buckling, natural frequency, and the shape of vibrating modes. One of the most important non-destructive methods for predicting the buckling load of the structure is the vibrational correlation technique (VCT), which is based on frequency variations with the axial load. In this study, an experimental study of the buckling load of COMPOSITE SANDWICH PLATES with lozenge core has been investigated. The hand lay-up method has been used for fabrication of the COMPOSITE SANDWICH PLATES. One of the specimens was used for the modal test. In order to verify the results of the VCT, the buckling load of four specimens was calculated by the experimental buckling test. The error of VCT was 2. 1 %. Hence, the efficiency of the VCT for COMPOSITE SANDWICH PLATES with lattice core was confirmed. Also, by investigating the effect of applied load percentage on the accuracy of the VCT, it was found that for the applied load of more than 63% of the buckling load, the accuracy of prediction of the vibrational correlation technique is acceptable.

SANDWICH structures are COMPOSITEs comprising a core layer SANDWICHed between two face layers; each layer has a distinctive characteristic, and the structure can also include COMPOSITE layers. This study presents an investigation of the free vibration behavior of a cored hybrid SANDWICH plate. The research demonstrates an analytical and numerical analysis. SANDWICH plate models made of aluminum face sheets with reinforced cores are used in this study. The analytical analysis used in this study of a three-layer SANDWICH plate is based on Kirchhoff's theorem. An additional mathematical model is constructed by dividing the core layer into two parts to form four layers with a hybrid structure. The governing equations to obtain the mechanical properties and natural frequency of the foam COMPOSITE, as well as open structural and hybrid cores, were used in this study. The numerical analysis of the various COMPOSITE structures using the modal analysis was performed through ANSYS version 2021-R1. Analytical outcomes reveal that replacing the foam core with an open-cell structure reduces the natural frequency by 25%. However, the hybrid core structure reduces the natural frequency by 27.6%. Also, the ultimate flexural load in the hybrid structure is increased by 127.7% compared to the open-cell structure core. Finally, numerical results are highly consistent with those obtained analytically.