설계변수에 대한 샌드위치 보의 파손하중

김종만 ( Jong Man Kim ) 한국복합재료학회 2003 Composites research Vol.16 No.3

샌드위치 구조물들은 적은 무게의 첨가로 높은 강성(stiffness)을 요구하는 조선업에 널리 사용 되어져 왔다. 국부하중 조건 하에서 샌드위치 구조물에 대한 디자인 변수들을 고려하는 것은 중요시되어졌다. 이 연구는 샌드위치 보의 강도에 대한 core층의 밀도, core층의 두께, 그리고 face층의 두께 비율의 영향을 기술하였다. 이차원 탄성이론에 바탕을 둔 파손 하중은 AS4/3501-6 facing과 polyurethane foam core 샌드위치 보의 3점 굴곡 실험 결과와 잘 일치하였다. 또한 그러한 파손 하중들은 face층의 비율의 변화와 함께 비교하였다. 파괴 mode들의 교차점으로 결정되어진 최적조건은 강도(strength)와 강성(stiffness)에 대한 샌드위치 빔의 최적 core 밀도의 값이 결정되었다. 추가적으로 강도에 대한 최적조건과 그렇지 못한 샌드위치 보에 대한 face 두께 비율 효과가 하중 길이에 따라 비교되었으며, 강도와 강성이 core/face 무게 비율과 함께 검토하였다. Sandwich structures have been widely used in the applications of vessel industry, where high structural stiffness is required with small addition of weight. It is so significant to think of the effect of the variables in the design process of the sandwich structure for the concentrated loads. This paper describes the influence of design variables, such as core density, core thickness and face thickness ratio, on the strength of sandwich beam. The theoretical failure loads based on the 2-D elasticity theory agree well with the experimental yield or failure loads, which are measured at the three point bending laboratory test using AS4/3501-6 facing and polyurethane foam core sandwich beam. The comparison of those yield or failure loads was also done with the ratio of the top to bottom face thickness. The theoretical optimum condition is obtained by finding the intersection point of failure modes involved, which gives optimum core density of the sandwich beam for strength and stiffness. In the addition, the effect of unequal face thickness for the optimized and off-optimized sandwich beams for the strength was compared with the ratio of loading length to beam length. and the variations of strength and stiffness were discussed with the relative ratio of core to face mass.

Dynamic response of a MRE sandwich structure under a non-homogenous magnetic field

Poojary Umanath R.,Hegde Sriharsha,Kiran Katari,Gangadharan K. V. 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.9

A viscoelastic layer improves the response of a sandwich structure under dynamic loading. Through integration of a magnetosensitive elastomer core, the adaptability of the structure over a wider frequency can be achieved. The current work focuses on the influence of a non-homogeneous magnetic field on a magnetorheological elastomer (MRE)-based sandwich cantilever beam. The dynamic response of the structure is measured using the impact hammer test as per the ASTM E-756-05 standard. Results revealed that the fundamental natural frequency of the MRE sandwich beam is a function of the intensity and the location of the non-homogenous magnetic field. The fundamental natural frequency is reduced as the magnitude of the magnetic flux density is increased or the magnetized region is shifted towards the fixed end. This unique response of the MRE sandwich beam under a non-homogenous magnetic field is an exception to the usual stiffness-enhancing behavior of a MRE. To study this disparity, we independently investigated the contributions by the localized stiffness enhancement and the deflection due to magnetic pull. The effect of the localized overall stiffness enhancement on the overall stiffness of the sandwich beam is investigated using modal analysis in ANSYS to analyze the variation in the fundamental frequency. The contribution due to magnetic pull is studied by performing an experimental modal analysis on an equivalent ferromagnetic cantilever beam deflected under the influence of a magnetic field. By comparing the experimental results and the corresponding investigation on the influencing factors, we confirmed that magnetic pull induced under non-homogenous magnetic field is an important parameter that significantly contributes to the dynamic response of a MRE sandwich beam.

Theory of thin-walled functionally graded sandwich beams with single and double-cell sections

Kim, N.I.,Lee, J. Applied Science Publishers ; Elsevier 2016 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.157 No.-

In the present work, a computational model has been presented to study the flexural and torsional analyses of thin-walled functionally graded sandwich beams with single and double-cell sections. The analysis model is based on the Euler-Bernoulli beam theory and includes the effects of elastic couplings and constrained warping. The mechanical properties of beam such as Young's and shear moduli are assumed to continuously vary in the thickness direction based on the power law distribution of volume fraction of ceramic or metal. To solve the flexural and torsional problems of functionally graded material (FGM) sandwich box beams, the finite beam element considering Hermite cubic interpolation polynomials is employed with the scope to discretize the governing equations. The theory is validated against the analytical solutions and the finite element analysis results for beams with single and double-cell box sections. Three types of material distribution are considered to investigate the effects of gradient index, thickness ratio of ceramic, material ratio, and width-to-height ratio on the various rigidities of cross-section of FGM sandwich box beams. Numerical results show that the above mentioned effects play important role on the structural responses of FGM sandwich box beams.

Dynamic instability region analysis of sandwich piezoelectric nano-beam with FG-CNTRCs face-sheets based on various high-order shear deformation and nonlocal strain gradient theory

Mohammad Arefi,Mahmoud Pourjamshidian,Ali Ghorbanpour Arani 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.32 No.2

In this research, the dynamic instability region (DIR) of the sandwich nano-beams are investigated based on nonlocal strain gradient elasticity theory (NSGET) and various higher order shear deformation beam theories (HSDBTs). The sandwich piezoelectric nano-beam is including a homogenous core and face-sheets reinforced with functionally graded (FG) carbon nanotubes (CNTs). In present study, three patterns of CNTs are employed in order to reinforce the top and bottom face-sheets of the beam. In addition, different higher-order shear deformation beam theories such as trigonometric shear deformation beam theory (TSDBT), exponential shear deformation beam theory (ESDBT), hyperbolic shear deformation beam theory (HSDBT), and Aydogdu shear deformation beam theory (ASDBT) are considered to extract the governing equations for different boundary conditions. The beam is subjected to thermal and electrical loads while is resting on Visco-Pasternak foundation. Hamilton principle is used to derive the governing equations of motion based on various shear deformation theories. In order to analysis of the dynamic instability behaviors, the linear governing equations of motion are solved using differential quadrature method (DQM). After verification with validated reference, comprehensive numerical results are presented to investigate the influence of important parameters such as various shear deformation theories, nonlocal parameter, strain gradient parameter, the volume fraction of the CNTs, various distributions of the CNTs, different boundary conditions, dimensionless geometric parameters, Visco-Pasternak foundation parameters, applied voltage and temperature change on the dynamic instability characteristics of sandwich piezoelectric nano-beam.

Forced vibration analysis of functionally graded sandwich deep beams

Akbas, Seref D. Techno-Press 2019 Coupled systems mechanics Vol.8 No.3

This paper presents forced vibration analysis of sandwich deep beams made of functionally graded material (FGM) in face layers and a porous material in core layer. The FGM sandwich deep beam is subjected to a harmonic dynamic load. The FGM in the face layer is graded though the layer thickness. In order to get more realistic result for the deep beam problem, the plane solid continua is used in the modeling of The FGM sandwich deep beam. The equations of the problem are derived based the Hamilton procedure and solved by using the finite element method. The novelty in this paper is to investigate the dynamic responses of sandwich deep beams made of FGM and porous material by using the plane solid continua. In the numerical results, the effects of different material distributions, porosity coefficient, geometric and dynamic parameters on the dynamic responses of the FGM sandwich deep beam are investigated and discussed.

Bending and buckling analysis of sandwich Reddy beam considering shape memory alloy wires and porosity resting on Vlasov’s foundation

Mostafa Bamdad,Mehdi Mohammadimehr,Kazem Alambeigi 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.6

The aim of this research is to analyze buckling and bending behavior of a sandwich Reddy beam with porous core and composite face sheets reinforced by boron nitride nanotubes (BNNTs) and shape memory alloy (SMA) wires resting on Vlasov’s foundation. To this end, first, displacement field’s equations are written based on the higher-order shear deformation theory (HSDT). And also, to model the SMA wire properties, constitutive equation of Brinson is used. Then, by utilizing the principle of minimum potential energy, the governing equations are derived and also, Navier’s analytical solution is applied to solve the governing equations of the sandwich beam. The effect of some important parameters such as SMA temperature, the volume fraction of SMA, the coefficient of porosity, different patterns of BNNTs and porous distributions on the behavior of buckling and bending of the sandwich beam are investigated. The obtained results show that when SMA wires are in martensite phase, the maximum deflection of the sandwich beam decreases and the critical buckling load increases significantly. Furthermore, the porosity coefficient plays an important role in the maximum deflection and the critical buckling load. It is concluded that increasing porosity coefficient, regardless of porous distribution, leads to an increase in the critical buckling load and a decrease in the maximum deflection of the sandwich beam.

Buckling and stability analysis of sandwich beams subjected to varying axial loads

Mohamed A. Eltaher,Salwa A Mohamed 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.2

This article presented a comprehensive model to study static buckling stability and associated mode-shapes of higher shear deformation theories of sandwich laminated composite beam under the compression of varying axial load function. Four higher order shear deformation beam theories are considered in formulation and analysis. So, the model can consider the influence of both thick and thin beams without needing to shear correction factor. The compression force can be described through axial direction by uniform constant, linear and parabolic distribution functions. The Hamilton’s principle is exploited to derive equilibrium governing equations of unified sandwich laminated beams. The governing equilibrium differential equations are transformed to algebraic system of equations by using numerical differential quadrature method (DQM). The system of equations is solved as an eigenvalue problem to get critical buckling loads and their corresponding mode-shapes. The stability of DQM in determining of buckling loads of sandwich structure is performed. The validation studies are achieved and the obtained results are matched with those. Parametric studies are presented to figure out effects of in-plane load type, sandwich thickness, fiber orientation and boundary conditions on buckling loads and mode-shapes. The present model is important in designing process of aircraft, naval structural components, and naval structural when non-uniform in-plane compressive loading is dominated.

A high-order closed-form solution for interfacial stresses in externally sandwich FGM plated RC beams

Chedad, Abdebasset,Daouadji, Tahar Hassaine,Abderezak, Rabahi,Belkacem, Adim,Abbes, Boussad,Rabia, Benferhat,Abbes, Fazilay Techno-Press 2017 Advances in materials research Vol.6 No.4

In this paper, an improved theoretical solution for interfacial stress analysis is presented for simply supported concrete beam bonded with a sandwich FGM plate. Interfacial stress analysis is presented for simply supported concrete beam bonded with a sandwich plate. This improved solution is intended for application to beams made of all kinds of materials bonded with a thin plate, while all existing solutions have been developed focusing on the strengthening of reinforced concrete beams, which allowed the omission of certain terms. It is shown that both the normal and shear stresses at the interface are influenced by the material and geometry parameters of the composite beam. A numerical parametric study was performed for different simulated cases to assess the effect of several parameters. Numerical comparisons between the existing solutions and the present new solution enable a clear appreciation of the effects of various parameters. The results of this study indicated that the FGM sandwich panel strengthening systems are effective in enhancing flexural behavior of the strengthened RC beams.

A new higher-order shear and normal deformation theory for functionally graded sandwich beams

Riadh Bennai,Abdelouahed Tounsi,Hassen Ait Atmane 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.3

A new refined hyperbolic shear and normal deformation beam theory is developed to study the free vibration and buckling of functionally graded (FG) sandwich beams under various boundary conditions. The effects of transverse shear strains as well as the transverse normal strain are taken into account. Material properties of the sandwich beam faces are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic material. Equations of motion are derived from Hamilton's principle. Analytical solutions for the bending, free vibration and buckling analyses are obtained for simply supported sandwich beams. Illustrative examples are given to show the effects of varying gradients, thickness stretching, boundary conditions, and thickness to length ratios on the bending, free vibration and buckling of functionally graded sandwich beams.

Bending analysis of power-law sandwich FGM beams under thermal conditions

Garg, Aman,Belarbi, Mohamed-Ouejdi,Li, Li,Tounsi, Abdelouahed Techno-Press 2022 Advances in aircraft and spacecraft science Vol.9 No.3

Broad writing on the examination of sandwich structures mirrors the significance of incorporating thermal loadings during their investigation stage. In the current work, an endeavor has been made to concentrate on sandwich FGM beams' bending behaving under thermal loadings utilizing shear deformation theory. Temperature-dependent material properties are used during the analysis. The formulation includes the transverse displacement field, which helps better predict the behavior of thick FGM beams. Three-different thermal profiles across the thickness of the beam are assumed during the analysis. The study has been carried out on both symmetric and unsymmetric sandwich FGM beams. It has been observed that the bending behavior of sandwich FGM beams is impacted by the temperature profile to which it is subjected. Power-law exponent and thickness of core also affect the behavior of the beam.