• Steel and Composite Structures
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• 제29권3호
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• pp.301-308
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• 2018

Properties of AFS vary with the changes in the face-sheet materials. Hence, the performance of AFS can be optimized by selecting face-sheet materials. In this work, three types of face-sheet materials representing elastic-perfectly plastic, elastic-plastic strain hardening and purely elastic materials were employed to study their effects on the flexural behavior and failure mechanism of AFS systematically. Result showed face-sheet materials affected the failure mechanism and energy absorption ability of AFS significantly. When the foam cores were sandwiched by aluminum alloy 6061, the AFS failed by face-sheet yielding and crack without collapse of the foam core, there was no clear plastic platform in the Load-Displacement curve. When the foam cores were sandwiched by stainless steel 304 and carbon fiber fabric, there were no face-sheet crack and the sandwich structure failed by core shear and collapse, plastic platform appeared. Energy absorption abilities of steel and carbon fiber reinforced AFS were much higher than aluminum alloy reinforced one. Carbon fiber was suggested as the best choice for AFS for its light weight and high performance. The versus strength ratio of face sheet to core was suggested to be a significant value for AFS structure design which may determine the failure mechanism of a certain AFS structure.

• Journal of Welding and Joining
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• 제23권6호
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• pp.49-54
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• 2005

Inner Structured and Bonded(ISB) panel, a kind of metallic sandwich panel, consists of two thin skin plates bonded to a micro-patterned inner structure. Its overall thickness is $1\~3mm$and it has attractive properties such as ultra-lightweight, high efficiency in stiffness-to-weight and strength-to-weight ratio. In many previous studies, resistance welding, brazing and adhesive bonding are studied for joining the panel. However these methods did not consider productivity, but focused on structural characteristics of joined panels, so that the joining process is very complicated and expensive. In this paper, a new joining process with resistance welding is developed. Curved surface electrodes are used to consider the productivity and the stopper is used between electrodes during welding time to maintain the shape of inner structure. Welding time, gap of electrodes and distance between welding points are selected as the process parameters. By measuring the tensile load with respect to the variation of welding time and gap of electrodes, proper welding conditions are studied. Welding time is proper between 1.5-2.5cycle. If welding time is too long, then inner structures are damaged by overheating. Gap of electrode should be shorter than threshold value fur joint strength, when total thickness of inner structure and skin plate is 3.3mm, the threshold distance is 3.0mm.

• 한국항공우주학회지
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• 제38권8호
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• pp.798-805
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• 2010

전구조 소형 복합재 위성인 과학기술위성 3호가 국내 최초로 개발되었다. 과학기술위성 3호는 기존의 위성과 달리 알루미늄 프레임이 없는 구조로 되어있으며 알루미늄 코어에 적층복합재 스킨을 가진 샌드위치 패널의 조합으로 구성되었다. 이 복합재 패널의 결합으로 구성된 격자형태의 공간에 다수의 전장박스와 탑재체 및 장치들이 장착된다. 본 연구는 과학기술위성 3호의 랜덤진동 응답에 관한 연구이며 이를 위하여 FEA 해석과 시험이 수행 되었다. 진동시험 결과와 전산해석결과를 서로 상호 비교 검토함으로써 위성의 진동 특성을 규명하고 결과의 신뢰성을 검증하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.266-267
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• 2007

Sandwich sheet with inner structure is expected to find many applications because of high stiffness to mass ratio. In order to simulate forming of sandwich sheet with pyramid core, an effective simulation method is required. Compared to the expensive model using solid elements, cost effective model using simplified elements such as shells and beams is developed. By comparing two models in terms of the cost and accuracy for unit cell deformation, a developed model shows some advantages over the model using solid elements. Evolution of two kind of forming limits, face buckling and core buckling are successfully expressed by developed model. Developed model is also applied in the simulation of square cup drawing and L-type bending. The corresponding experiments are carried out. Deformation shape and wrinkling behavior are compared and discussed. It is found that simulation results using a developed model are in good agreement with experiments.

• 산업기술연구
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• 제37권1호
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• pp.1-4
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• 2017

Speeding up of railway vehicles requires weight reduction of the vehicle body. However, when the vehicle body is lighter, the sound insulation performance for blocking the noise from the outside is reduced. Aluminum is an important material used in the bodywork of transportation vehicles such as railway vehicles, aircraft, and automobiles. In this study, the bending stiffness and sound insulation performance of foamed aluminum with sandwich structure are investigated experimentally. The transmission loss is measured in accordance with the international standard ASTM E 2249-02. The mass-law deviation is used to evaluate the sound insulation performance per weight. In order to examine the applicability of the foamed aluminum sandwich panel to railway vehicles, the analysis of bending stiffness and an experimental review are carried out at the same time.

• 복합신소재구조학회 논문집
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• 제3권3호
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• pp.22-30
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• 2012

This study deals with an enhanced assumed strain (EAS) three-dimensional element for free vibration analysis of laminated composite and sandwich structures. The three-dimensional finite element (FE) formulation based on the EAS method for composite structures shows excellence from the standpoints of computational efficiency, especially for distorted element shapes. Using the EAS FE formulation developed for this study, the effects of side-to-thickness ratios, aspect ratios and ply orientations on the natural frequency are studied and compared with the available elasticity solutions and other plate theories. The numerical results obtained are in good agreement with those reported by other investigators. The new approach works well for the numerical experiments tested, especially for complex structures such as sandwich plates with laminated composite faces.

• Steel and Composite Structures
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• 제16권3호
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• pp.325-337
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• 2014

The strength and buckling problem of a five layer sandwich beam under axial compression or bending is presented. Two faces of the beam are thin aluminium sheets and the core is made of aluminium foam. Between the faces and the core there are two thin binding glue layers. In the paper a mathematical model of the field of displacements, which includes a share effect and a bending moment, is presented. The system of partial differential equations of equilibrium for the five layer sandwich beam is derived on the basis of the principle of stationary total potential energy. The equations are analytically solved and the critical load is obtained. For comparison reasons a finite element model of the beam is formulated. For the case of bended beam the static analysis has been performed to obtain the stress distribution across the height of the beam. For the axially compressed beam the buckling analysis was carried out to determine the buckling load and buckling shape. Moreover, experimental investigations are carried out for two beams. The comparison of the results obtained in the analytical and numerical (FEM) analysis is shown in graphs and figures. The main aim of the paper is to present an analytical model of the five layer beam and to compare the results of the theoretical, numerical and experimental analyses.

• Advanced Composite Materials
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• 제17권1호
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• pp.41-56
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• 2008

In this research, optical fiber sensors and shape memory alloys (SMA) were incorporated into sandwich panels for development of a smart honeycomb sandwich structure with damage detection and shape recovery functions. First, small-diameter fiber Bragg grating (FBG) sensors were embedded in the adhesive layer between a CFRP face-sheet and an aluminum honeycomb core. From the change in the reflection spectrum of the FBG sensors, the debonding between the face-sheet and the core and the deformation of the face-sheet due to impact loading could be well detected. Then, the authors developed the SMA honeycomb core and bonded CFRP face-sheets to the core. When an impact load was applied to the panel, the cell walls of the core were buckled and the face-sheet was bent. However, after the panel was heated over the reverse transformation finish temperature of the SMA, the core buckling disappeared and the deflection of the face-sheet was relieved. Hence the bending stiffness of the panel could be recovered.

• Advances in nano research
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• 제12권6호
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• pp.593-603
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• 2022

The critical buckling temperature rise of a newly proposed piezoelectrically active sandwich plate (ASP) has been investigated in this work. This structure includes a porous polymeric layer integrated between two piezoelectric nanocomposite layers. The piezoelectric material is made of a passive polymeric material that is activated by lead-free nanowires (NWs) of zinc oxide (ZnO) embedded inside the matrix. In both nanocomposite layers and porous core, functional graded (FG) patterns have been considered for the distributions of ZnO NWs and voids, respectively. By adopting a higher-order theory of plates, the governing equations of thermal buckling are obtained. This set of equations is then treated using an extended mesh-free solution. The effects of plate dimensions, porosity states, and the nanowire parameters have been investigated on the critical buckling temperature rises of the proposed lightweight ASPs with different boundary conditions. The results disclose that the use of porosities in the core and/or mixing ZnO NWs in the face sheets substantially arise the critical buckling temperatures of the newly proposed active sandwich plates.

• 한국철도학회논문집
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• 제12권4호
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• pp.518-525
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• 2009

논문은 샌드위치 복합재가 적용된 바이모달 트램의 설계검증을 위한 구조 성능 시험과 유한요소 해석에 대해 기술하였다. 차체 구조물에 적용된 샌드위치 복합재는 알루미늄 하니컴 심재와 WR580/NF4000 유리섬유/애폭시 면재로 구성되었다. 이때, 차체 구조물의 구조 시험은 JIS E 7105 규정에 따라 수직하중, 압축하중, 비틀림 및 고유진동수 시험이 각각 수행되었다. 그리고 다이얼게이지, 스트레인게이지, 가속도 센서를 통해 얻어진 처짐, 응력, 고유전동수 결과에 따른 구조 안전성을 평가하였다. 그리고 Ansys v11.0을 이용하여 유한요소해석을 수행하였고, 구조 시험 결과와 비교하였다. 구조 시험 결과는 제안된 유한요소 모델을 사용한 구조 해석 결과와 처침, 응력, 고유진동수가 비교적 잘 일치함을 확인하였다.