• Advances in nano research
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• v.15 no.5
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• pp.423-439
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• 2023

The aim of this paper is to investigate the free vibration behavior of the micro sandwich beam composing of five layers such as functionally graded (FG) porous core, nanocomposite reinforced by carbon nanotubes (CNTs) and piezomagnetic/piezoelectric layers subjected to magneto electrical potential resting on silica aerogel foundation. The effect of foundation has been taken into account using Vlasov model in addition to rigid base assumption. For this purpose, an iterative technique is applied. The material properties of the FG porous core and FG nanocomposite layers are considered to vary throughout the thickness direction of the beams. Based on the Timoshenko beam theory and Hamilton's principle, the governing equations of motion for the micro sandwich beam are obtained. The Navier's type solution is utilized to obtain analytical solutions to simply supported micro sandwich beam. Results are verified with corresponding literatures. In the following, a study is carried out to find the effects of the porosity coefficient, porous distribution, volume fraction of CNT, the thickness of silica aerogel foundation, temperature and moisture, geometric parameters, electric and magnetic potentials on the vibration of the micro sandwich beam. The results are helpful for the design and applications of micro magneto electro mechanical systems.

• Structural Engineering and Mechanics
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• v.48 no.1
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• pp.93-102
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• 2013

An optimization work was developed in this work to provide design information for sandwich beam in civil engineering applications. This research is motivated by the wide-range applications of sandwich structures such as; slab, beam, girder, and railway sleeper. The design of a sandwich beam was conducted by using analytical and numerical optimization. Both analytical and numerical procedures consider the optimum design with structure mass objective minimization. Allowable deflection was considered as design constraints. It was found that the optimized core to the skins mass ratio is affected by the skin to core density and elastic modulus ratios. Finally, the optimum core to skin mass ratio cannot be constant for different skin and core materials.

• Steel and Composite Structures
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• v.46 no.2
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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 KSNVE
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• v.7 no.3
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• pp.511-519
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• 1997

For a number of years it has been known that flexural vibration in a beam and plate can be damped by the application of layer of damping (viscoelastic) material that is in turn constrained by a backing layer or foil. In this study, a quantitative analysis of damping of the sandwich beam has been performed by using impact test. The damping is characterized by the loss factor .etha. in which the damping is normalized by imaginary part of the complex bending stiffiness of the beam. Results show that the relative thickness of the sandwich beam gives more effect on the riatural-frequencies and loss factor than the variation of width does. It is also shown that the Ross-Kerwin-Ungar equation and impact test can be effectively used to identify the damping characteristic of the sandwich beam and viscoelastic material.

• Composites Research
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• v.16 no.3
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• pp.18-24
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• 2003

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.

• Steel and Composite Structures
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• v.21 no.1
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• pp.1-36
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• 2016

In the present study, the nonlinear magneto-electro-mechanical free vibration behavior of rectangular double-bonded sandwich microbeams based on the modified strain gradient theory (MSGT) is investigated. It is noted that the top and bottom sandwich microbeams are considered with boron nitride nanotube reinforced composite face sheets (BNNTRC-SB) with electrical properties and carbon nanotube reinforced composite face sheets (CNTRC-SB) with magnetic fields, respectively, and also the homogenous core is used for both sandwich beams. The connections of every sandwich beam with its surrounding medium and also between them have been carried out by considering Pasternak foundations. To take size effect into account, the MSGT is introduced into the classical Timoshenko beam theory (CT) to develop a size-dependent beam model containing three additional material length scale parameters. For the CNTRC and BNNTRC face sheets of sandwich microbeams, uniform distribution (UD) and functionally graded (FG) distribution patterns of CNTs or BNNTs in four cases FG-X, FG-O, FG-A, and FG-V are employed. It is assumed that the material properties of face sheets for both sandwich beams are varied in the thickness direction and estimated through the extended rule of mixture. On the basis of the Hamilton's principle, the size-dependent nonlinear governing differential equations of motion and associated boundary conditions are derived and then discretized by using generalized differential quadrature method (GDQM). A detailed parametric study is presented to indicate the influences of electric and magnetic fields, slenderness ratio, thickness ratio of both sandwich microbeams, thickness ratio of every sandwich microbeam, dimensionless three material length scale parameters, Winkler spring modulus and various distribution types of face sheets on the first two natural frequencies of double-bonded sandwich microbeams. Furthermore, a comparison between the various beam models on the basis of the CT, modified couple stress theory (MCST), and MSGT is performed. It is illustrated that the thickness ratio of sandwich microbeams plays an important role in the vibrational behavior of the double-bonded sandwich microstructures. Meanwhile, it is concluded that by increasing H/lm, the values of first two natural frequencies tend to decrease for all amounts of the Winkler spring modulus.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.978-981
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• 2005

The vibration analysis of damped sandwich beam is conducted using finite element method. The equation of motion presented by Mead and Markus is used to formulate FEM. Also as the thickness of the core in the damped sandwich beam goes to zero, conventional beam theory based on the transformed-section method and the equation of Mead and Markus are compared. According to the change of thickness and loss factor of the core, the forced frequency response of beam is calculated and discussed. And then using the half-power band width method, the damping ratio of each mode is calculated and discussed about each case.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.608-611
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• 2005

In this paper the general equation of motion of damped sandwich beam including arbitrary viscoelastic material layer was derived based on the equation presented by Mead and Markus. The equation of motion of n-layered sandwich beam was represented by (n+3)th order ordinary differential equation. It was verified that the general equation of motion derived in this paper could represent the equations of motions for single-layered, three-layered, five-layered and multi-layered damped beam. Finite element method for the arbitrary-layered damped beam was formulated and programmed using higher order shape functions. Several numerical examples were implemented to show the effects of damped material.

• Advances in materials Research
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• v.11 no.4
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• pp.279-298
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• 2022

In this paper, the important novelty and the defining a physical phenomenon of the resent research is the development of nonlocal stress and strain parameters on the porous sandwich beam with functionally graded materials in the top and bottom face sheets.Also, various beam models including Euler-Bernoulli, Reddy and the generalized formulation of two-variable beam theories are obtained in this research. According to a nonlocal strain elasticity theory, the strain at a reference point in the body is dependent not only on the stress state at that point, but also on the stress state at all of the points throughout the body. Thus, the nonlocal stress-strain elasticity theory is defined that can be actual at micro/nano scales. It can be seen that the critical buckling load and transverse deflection of sandwich beam by considering both nonlocal stress-strain parameters is higher than the nonlocal stress parameter. On the other hands, it is noted that by considering the nonlocal stress-strain parameters simultaneously becomes the actual case.

• Steel and Composite Structures
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• v.44 no.1
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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.