• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.207-208
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• 2006

Sandwich structures, which are composed of a thick core between two faces, are commonly used in many engineering applications because they combine high stiffness and strength with low weight. In this paper, we have investigated the buckling protection of an inner structure plate and the useful corrugated configuration for contact, and the fabrication method of the inner structure plate for large area using the continuous molding process. Also, we have guaranteed the accuracy of the molding process through the micro corrugated mold fabrication and analyzed aspect properties of the inner structure plate fabricated for a large area using the partial mold process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.389-392
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• 2005

Sandwich structures, which are composed of a thick core between two thin faces, are commonly used in many engineering applications because they combine high stiffness and strength with low weight. In this paper, through the FLD analysis according to the pattern changes, we have confirmed the deformed shape and formability distribution. Also, we have fabricated the dimple press mold according to the pattern changes, and obtained the dimple inner structure the forming experiments.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.4
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• pp.149-158
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• 2008

This article provides strength estimation of T-joint area which made of composite material. Inner and outer structures of medium range surveillance radar are all made of sandwich structure which is made with composite material(CFRP) and aluminum honeycomb core. Since the radar is voluminous and has very complex inner structure, the whole structure cannot be made as one piece. Therefore, usage of T-joints is inevitable. Since some of stress concentration areas were located around T-joint area, series of strength estimations were conducted. Three different configurations were tested to improve mechanical properties(primarily on strength). The results show an improvement on strength to meet calculated strength on stress concentrated T-joint area.

• Steel and Composite Structures
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• v.38 no.3
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• pp.305-317
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• 2021

The mechanical behavior of the outer square inner circular concrete-filled dual steel tubular (SCCFT) stub columns under axial compression is investigated by means of experimental research, numerical analysis and theoretical investigation. Parameters such as diameter ratio, concrete strength and steel ratio were discussed to identify their influence on the mechanical properties of SCCFT short columns on the basis of the experimental investigation of seven SCCFT short columns. By establishing a finite element model, nonlinear analysis was performed to discuss the longitudinal and transverse stress of the dual steel tubes. The longitudinal stress characteristics of the core and sandwich concrete were also analyzed. Furthermore, the failure sequence was illustrated and the reasonable cross-section composition of SCCFT stub column was proposed. A formula to predict the axial load capacity of SCCFT stub column was advanced and verified by the results from experiment and the finite element.

• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.2
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• pp.91-98
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• 2017

Recently, composite materials have been mainly used in the main wings, ailerons, and fuselages of aircraft and rotor blades of helicopters. Composite materials used in rapid moving structures are subject to impact by hail, lightning, and bird strike. Such an impact can destroy fiber tissues in the composite materials as well as deform the composite materials, resulting in various problems such as weakened rigidity of the composite structure and penetration of water into tiny cracks. In this study, experiments were conducted using a 2 kW halogen lamp which is most frequently used as a light source, a 2 kW near-infrared lamp, which is used for heating to a high temperature, and a 6 kW xenon flash lamp which emits a large amount of energy for a moment. CFRP composite sandwich panels using Nomex honeycomb core were used as the specimens. Experiments were carried out under impact damages of 1, 4 and 8 J. It was found that the detection of defects was fast when the xenon flash lamp was used. The detection of damaged regions was excellent when the halogen lamp was used. Furthermore, the near-infrared lamp is an effective technology for showing the surface of a test object.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.586-594
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• 2009

This paper is the study on random, sinusoidal and shock vibration responses for the STSAT-3(science and technology satellite-3) proto-model which is the first small size all-composite satellite in Korea. The structure system of the STSAT-3 forms box type structure by joining several hybrid sandwich panels comprised of honeycomb core and carbon fiber reinforced laminated composite skins on both side. Mode shape, stress, displacement and acceleration responses are obtained on both the frequency domain and time domain by means of a commercial FEA software MSC/NASTRAN. From these analysis results, failure, safety factor and design validity are assessed. These results can be successfully applicable as reference data when a new satellite is developed as well as giving out an excellent criteria in satellite vibration treatment design.

• Advances in nano research
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• v.12 no.1
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• pp.81-99
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• 2022

The aim of current work is to evaluate thermo-electrical characteristics of graphene nanoplatelets Reinforced Composite (GNPRC) coupled with magneto-electro-elastic (MEE) face sheet. In this regard, a cylindrical smart nanocomposite made of GNPRC with an external MEE layer is considered. The bonding between the layers are assumed to be perfect. Because of the layer nature of the structure, the material characteristics of the whole structure is regarded as graded. Both mechanical and thermal boundary conditions are applied to this structure. The main objective of this work is to determine critical temperature and critical voltage as a function of thermal condition, support type, GNP weight fraction, and MEE thickness. The governing equation of the multilayer nanocomposites cylindrical shell is derived. The generalized differential quadrature method (GDQM) is employed to numerically solve the differential equations. This method is integrated with Deep Learning Network (DNN) with ADADELTA optimizer to determine the critical conditions of the current sandwich structure. This the first time that effects of several conditions including surrounding temperature, MEE layer thickness, and pattern of the layers of the GNPRC is investigated on two main parameters critical temperature and critical voltage of the nanostructure. Furthermore, Maxwell equation is derived for modeling of the MEE. The outcome reveals that MEE layer, temperature change, GNP weight function, and GNP distribution patterns GNP weight function have significant influence on the critical temperature and voltage of cylindrical shell made from GNP nanocomposites core with MEE face sheet on outer of the shell.

• Journal of the Korea Convergence Society
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• v.10 no.4
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• pp.139-145
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• 2019

This paper investigated the strength and stiffness of composite truss unit structures. The model used is a core-filled model combining the Kagome model and the cube truss model. The material properties used for the analysis are 304 stainless steel with elastic modulus of 193 GPa and yield stress of 215 MPa. The theoretical equation is derived from the relative elasticity relation of Gibson - Ashby ratio, the analysis was performed using Deform 3D, a commercial tool. In conclusion, the relative elasticity for this unit model correlates with 1.25 times the relative density and constant coefficient, elasticity is inversely proportional to pore size. The relative compressive strength has a correlation with relative density of 1.25 times. Proof of this is a real experiment, the derived theoretical relationship should further consider mechanical behavior such as bending and buckling. In the future, it is hoped that the research on the elasticity and the stress according to the structure of the three-dimensional space will be continued.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.55-60
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• 2010

The honeycomb composite joint structure designed for application to a tilting KTX railroad car body is subjected to bending loads of a cantilever type. Honeycomb sandwich composite panel-joint attached in the real tilting car body was fabricated and sectioned as several beam-joint specimens for the bending test. The fracture behaviors of these specimens under static loads were different from those under cyclic loads. Static bending loads caused shear deformation and fracture in the honeycomb core region, while fatigue cyclic bend loading caused delamination along the interface between the composite skin and the honeycomb core, and/or caused a fracture in the welded part jointed with the steel under-frame. These fracture behaviors could occur in other industrial honeycomb composite joints with similar sub-structures, and be used for improving design parameters of a honeycomb composite joint structure.

• Steel and Composite Structures
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• v.42 no.2
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• pp.277-288
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• 2022

A novel flat steel plate-concrete-corrugated steel plate (FS-C-CS) sandwich panel was proposed for resisting impact load. The failure mode, impact force and displacement response of the FS-C-CS panel under impact loading were studied via drop-weight impact tests. The combined global flexure and local indentation deformation mode of the FS-C-CS panel was observed, and three stages of impact process were identified. Moreover, the effects of corrugated plate height and steel plate thickness on the impact responses of the FS-C-CS panels were quantitatively analysed, and the impact resistant performance of the FS-C-CS panel was found to be generally improved on increasing corrugated plate height and thickness in terms of smaller deformation as well as larger impact force and post-peak mean force. The Finite Element (FE) model of the FS-C-CS panel under impact loading was established to predict its dynamic response and further reveal its failure mode and impact energy dissipation mechanism. The numerical results indicated that the concrete core and corrugated steel plate dissipated the majority of impact energy. In addition, employing end plates and high strength bolts as shear connectors could prevent the slip between steel plates and concrete core and assure the full composite action of the FS-C-CS panel.