• Steel and Composite Structures
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• 제16권4호
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• pp.389-415
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• 2014

This study deals with dynamic model of composite sandwich panels with functionally graded flexible cores under low velocity impacts of multiple large or small masses using a new improved higher order sandwich panel theory (IHSAPT). In-plane stresses were considered for the functionally graded core and face sheets. The formulation was based on the first order shear deformation theory for the composite face sheets and polynomial description of the displacement fields in the core that was based on the second Frostig's model. Fully dynamic effects of the functionally graded core and face-sheets were considered in this study. Impacts were assumed to occur simultaneously and normally over the top and/or bottom of the face-sheets with arbitrary different masses and initial velocities. The contact forces between the panel and impactors were treated as internal forces of the system. Nonlinear contact stiffness was linearized with a newly presented improved analytical method in this paper. The results were validated by comparing the analytical, numerical and experimental results published in the latest literature.

• 한국공간구조학회논문집
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• 제14권4호
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• pp.65-72
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• 2014

To improve the noise and vibration problems of the existing public parking systems, new floor system was proposed. This system consists of the Sandwich Plate System(SPS), steel beam and post-tensioned steel tendons. To verify the dynamic characteristics such as the natural frequency and damping ratio of the system, the free vibration test was performed. Test results showed that the natural frequency of the SPS composite beam was 23.8Hz and it was increased by 3.8% by installing the post-tensioned tendons. The damping ratio of the specimen with tendons was about 1.64%.

• Steel and Composite Structures
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• 제20권3호
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• pp.513-543
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• 2016

Third order shear deformation theory is used to evaluate electro-elastic solution of a sandwich plate with considering functionally graded (FG) core and composite face sheets made of piezoelectric layers. The plate is resting on the Pasternak foundation and subjected to normal pressure. Short circuited condition is applied on the top and bottom of piezoelectric layers. The governing differential equations of the system can be derived using Hamilton's principle and Maxwell's equation. The Navier's type solution for a sandwich rectangular thick plate with all edges simply supported is used. The numerical results are presented in terms of varying the parameters of the problem such as two elastic foundation parameters, thickness ratio ($h_p/2h$), and power law index on the dimensionless deflection, critical buckling load, electric potential function, and the natural frequency of sandwich rectangular thick plate. The results show that the dimensionless natural frequency and critical buckling load diminish with an increase in the power law index, and vice versa for dimensionless deflection and electrical potential function, because of the sandwich thick plate with considering FG core becomes more flexible; while these results are reverse for thickness ratio.

• Structural Engineering and Mechanics
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• 제68권6호
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• pp.721-733
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• 2018

The modal frequency responses of functionally graded (FG) sandwich doubly curved shell panels are investigated using a higher-order finite element formulation. The system of equations of the panel structure derived using Hamilton's principle for the evaluation of natural frequencies. The present shell panel model is discretised using the isoparametric Lagrangian element (nine nodes and nine degrees of freedom per node). An in-house MATLAB code is prepared using higher-order kinematics in association with the finite element scheme for the calculation of modal values. The stability of the opted numerical vibration frequency solutions for the various shell geometries i.e., single and doubly curved FG sandwich structure are proven via the convergence test. Further, close conformance of the finite element frequency solutions for the FG sandwich structures is found when compared with the published theoretical predictions (numerical, analytical and 3D elasticity solutions). Subsequently, appropriate numerical examples are solved pertaining to various design factors (curvature ratio, core-face thickness ratio, aspect ratio, support conditions, power-law index and sandwich symmetry type) those have the significant influence on the free vibration modal data of the FG sandwich curved structure.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.228-233
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• 2001

Satellite system experiences severe mechanical loads during the launch period. Therefore, positive margin of safety of the satellite system must be demonstrated for every possible mechanical loading condition during the launch period. This paper presents modal and stress analysis result due to quasi-static loads for the satellite antenna system. The failure tendency for the sandwich construction of the satellite antenna system has been studied with various lamination angles of unidirectional prepreg.

• Structural Engineering and Mechanics
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• 제71권2호
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• pp.197-210
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• 2019

Probabilistic buckling behavior of sandwich panel considering random system parameters using a radial basis function (RBF) approach is presented in this paper. The random system properties result in an uncertain response of the sandwich structure. The buckling load of laminated sandwich panel is obtained by employing higher-order-zigzag theory (HOZT) coupled with RBF and probabilistic finite element (FE) model. The in-plane displacement variation of core as well as facesheet is considered to be cubic while transverse displacement is considered to be quadratic within the core and constant in the facesheets. Individual and combined stochasticity in all elemental input parameters (like facesheets thickness, ply-orientation angle, core thickness and properties of material) are considered to know the effect of different degree of stochasticity, ply- orientation angle, boundary conditions, core thickness, number of laminates, and material properties on global response of the structure. In order to achieve the computational efficiency, RBF model is employed as a surrogate to the original finite element model. The stiffness matrix of global response is stored in a single array using skyline technique and simultaneous iteration technique is used to solve the stochastic buckling equations.

• Steel and Composite Structures
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• 제44권1호
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• pp.105-117
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• 2022

Impact resistance efficiency of the newly designed sandwich beam with a laterally arched core as bio-inspired by the woodpecker is numerically investigated. The principal components of the beam comprise a dual-core system sandwiched by the top and bottom laminated CFRP skins. Different materials, including hot melt adhesive, high-density polyethylene (HDPE), acrylonitrile butadiene styrene (ABS), epoxy resin (EPON862), aluminum (Al6061), and mild carbon steel (AISI1018), are considered for the side-arched core layer of the beam for impact efficiency assessment. The aluminum honeycomb takes the role of the second core. Contact force, stress, damage formation, and impact energy for beams equipped with different materials are examined. A diversity in performance superiority is noticed in each of these indicators for different core materials. Therefore, for overall performance appraisal, the impact resistance efficiency index, which covers several chief impact performance parameters, of each sandwich beam is computed and compared. The impact resistance efficiency index of the structure equipped with the AISI1018 core is found to be the highest, about 3-10 times greater than other specimens, thus demonstrating its efficacy as the optimal material for the bio-inspired dual-core sandwich beam system.

• Steel and Composite Structures
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• 제46권2호
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• pp.195-202
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• 2023

Dynamic deflection analysis of sandwich beams with cellular core under thermal and pulse loads has been performed in the present article. The cellular core sandwich beam has two layers fortified by graphene oxide powder (GOP) which are micromechanically modeled by Halpin-Tsai formulation. The pulse load has blast type and is applied on the top side of sandwich beam. The system of equations has been developed based on higher-order beam theory and Ritz method. Then, they are solved in Laplace domain to derive the dynamic deflections. The dependency of beam deflection on temperature variation, GOP content, pulse load duration/location and core relative density has been studied in detail.

• Journal of Microbiology and Biotechnology
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• 제14권2호
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• pp.385-389
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• 2004

The antibody-mix sandwich enzyme-linked immunosorbent assay (Ab-mix sELlS A) system was developed in order to simultaneously detect the extracellular polysaccharide (FPS) of Aspergillus, Penicillium, or Fusarium species using one detection system. The detection limit and detection range of the Ab-mix sELISA towards EPS of Penicilliun citrinum were not changed, and those towards Fusarium moniliforme EPS were changed a little compared to that of individual sandwich ELISA [9, 10]. The fungal culture filtrates of Aspergillus and Penicillium species showed nearly similar reactivity towards Ab-mix sELISA as that of sELISA using the MAb lB8 alone [9]. Also, the fungal culture filtrates of Fusarium species showed nearly the same reactivity towards Ab-mix sELISA as that of sELISA using the MAb lB8 alone [10]. Thus, this ELISA system showed that the three genera of molds, Aspergillus, Penicillium, or Fusarium, which are three major important molds producing mycotoxins in food or agricultural commodities, could be detected at the same time, using one detection system.

• 대한기계학회논문집A
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• 제26권2호
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• pp.225-233
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• 2002

The flexural vibration characteristics of a sandwich beam system with a partially inserted viscoelastic layer have been quantitatively studied using a finite element analysis in combination with a sine-sweep test. Antisymmetric mode shapes of the flexural vibration were visualized by the holographic interferometry and agreed with those calculated by the finite element simulation. Effects of the beam thickness as well as the length and thickness of partial viscoelastic layers on the system loss factor(η$\_$s/) and resonant frequency($\omega$$\_$r/) were significantly large fur the symmetric and antisymmetric modes of the beam system.