• 한국자동차공학회논문집
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• 제14권2호
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• pp.57-66
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• 2006

AA5182-polypropylene sandwich sheet was manufactured, and the mechanical properties evaluation was executed in order to identify $L{\ddot{u}}ders$ band that causes fabrication process problem and especially surface roughness. To identify formability, deformation behavior, plastic strain ratio (R-value) and pole figure were measured, and texture analysis was performed. In the case of sandwich sheet, the unstable deformation behavior has decreased. As well, for sandwich sheet, A1 skin could manage the most of load, and the elongation has improved about 45% more than that of A1 skin. The plastic strain ratio of A1 skin and sandwich panel, which indicates serration behavior, was obtained from instantaneous plastic strain ratio evaluation. Also, the planar anisotropy of sandwich sheet has decreased more than that of A1 skin. According to these results, the sandwich sheet produced lightening effect and could control unstable deformation characteristic, that is, surface roughness caused by $L{\ddot{u}}ders$ band. Furthermore, it was proved that the texture control of the rolling attachment of A1 skin is necessary to improve the formability of the sandwich panel.

• Steel and Composite Structures
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• 제25권3호
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• pp.327-335
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• 2017

To gain more knowledge of aluminum foam sandwich structure and promote the engineering application, aluminum foam sandwich consisting of 7050 matrix aluminum foam core and 304 stainless steel face-sheets was studied under three-point bending by WDW-T100 electronic universal tensile testing machine in this work. Results showed that when aluminum foam core was reinforced by 304 steel face-sheets, its load carrying capacity improved dramatically. The maximum load of AFS in three-point bending increased with the foam core density or face-sheet thickness monotonically. And also when foam core was reinforced by 304 steel panels, the energy absorption ability of foam came into play effectively. There was a clear plastic platform in the load-displacement curve of AFS in three-point bending. No crack of 304 steel happened in the present tests. Two collapse modes appeared, mode A comprised plastic hinge formation at the mid-span of the sandwich beam, with shear yielding of the core. Mode B consisted of plastic hinge formation both at mid-span and at the outer supports.

• Composites Research
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• 제13권2호
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• pp.81-90
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• 2000

자동차의 경량화를 위해서 AA5182/Polypropylene/AA5182 형태의 알루미늄 합금과 폴리프로필렌으로 구성된 샌드위치 판재가 개발되었다. 샌드위치 판재의 성형성을 평가하기 위해서 0.2mm 두께의 AA5182 판재와 1.2mm 두께의 샌드위치 판재의 성형한계도를 수정된 Marciniak-Kuczynski(M-K) 이론에 의해서 구하였다. 판재의 이방성을 표현하기 위해서 Hill의 1948년 항복곡선 표현 식을 사용하였다. 그 결과 샌드위치 판재의 성형한계도가 AA5182판재보다 더 우수하게 평가되었으며 이것은 실험값과 잘 일치하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.1089-1096
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• 2005

This study was experimental test of edgewise compression properties for aluminum(type-50XX) sandwich panel with thermal environment and surface treatment using adhesive film. There was decreasing $10\%-peel$ strength after thermal environment. Through compressive. buckling mode know to seen of properties of adhesive, sheet and core strength. First case of Chromate to aluminum sheet, know low shear strength of adhesive through buckling mode but case of Beomite to aluminum sheet, know than thin sheet and core low strength through buckling mode.

• 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.

• 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.

• 소성∙가공
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• 제11권6호
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• pp.482-486
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• 2002

Sandwich sheets composed of stainless steel/aluminum/stainless steel were produced by roll cladding. In order to investigate the effect of the friction between roll and cladding sample, the lubrication condition of the roll surface was varied. Clad rolling without lubrication gave rise to a small increment of the normal strain of aluminum in the rolling direction. This experimental result was confirmed by FEM modeling. Through-thickness hardness gradients in the mid aluminum layer was successfully explained by variations of the strain state through thickness layers. FEM modeling implied that cladding without lubrication led to a large shear strain variation at the surface of aluminum layer.

• Computers and Concrete
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• 제27권4호
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• pp.369-383
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• 2021

This article deals with the frequency analysis of viscoelastic sandwich disk with graphene nano-platelets (GPLs) reinforced viscoelastic concrete (GPLRVC) face sheets and honeycomb core. The honeycomb core is made of aluminum due to its low weight and high stiffness. The rule of the mixture and modified Halpin-Tsai model are engaged to provide the effective material constant of the concrete. By employing Hamilton's principle, the governing equations of the structure are derived and solved with the aid of the Generalize Differential Quadrature Method (GDQM). In this paper, viscoelastic properties are modeled according to Kelvin-Voigt viscoelasticity. The deflection as the function of time can be solved by the fourth-order Runge-Kutta numerical method. Afterward, a parametric study is carried out to investigate the effects of the outer to inner radius ratio, hexagonal core angle, thickness to length ratio of the concrete, the weight fraction of GPLs into concrete, and the thickness of honeycomb core to inner radius ratio on the frequency of the viscoelastic sandwich disk with honeycomb core and FG-GPLRVC face sheet.

• 한국재료학회지
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• 제29권6호
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• pp.392-397
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• 2019

A cold roll-bonding process is applied to fabricate an AA6061/AA5052/AA6061 three-layer clad sheet. Two AA6061 and one AA5052 sheets of 2 mm thickness, 40 mm width, and 300 mm length are stacked, with the AA5052 sheet located in the center. After surface treatment such as degreasing and wire brushing, sample is reduced to a thickness of 1.5 mm by multi-pass cold rolling. The rolling is performed at ambient temperature without lubricant using a 2-high mill with a roll diameter of 400 mm at rolling speed of 6.0 m/sec. The roll bonded AA6061/AA5052/AA6061 complex sheet is then hardened by natural aging(T4) and artificial aging(T6) treatments. The microstructures of the as-roll bonded and age-hardened Al complex sheets are revealed by optical microscopy; the mechanical properties are investigated by tensile testing and hardness testing. After rolling, the roll-bonded AA6061/AA5052/AA6061 sheets show a typical deformation structure in which grains are elongated in the rolling direction. However, after T4 and T6 aging treatment, there is a recrystallization structure consisting of coarse equiaxed grains in both AA5052 and AA6061 sheets. The as roll-bonded specimen shows a sandwich structure in which an AA5052 sheet is inserted into two AA6061 sheets with higher hardness. However, after T4 and T6 aging treatment, there is a different sandwich structure in which the hardness of the upper and lower layers of the AA6061 sheets is higher than that of the center of the AA5052 sheet. The strength values of the T4 and T6 age-treated specimens are found to increase by 1.3 and 1.4 times, respectively, compared to that value of the starting material.

• 한국기계가공학회지
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• 제14권2호
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• pp.81-86
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• 2015

This study investigated electromagnetic interference (EMI) shielding effectiveness (SE) of hybrid conductive fabrics. The coaxial transmission line method was used to measure the EMI Shielding effectiveness of the conductive fabrics. We designed and constructed a measuring system, consisting of a network analyzer and a device that serves as a sample holder and at the same time as a transmission medium of incident electromagnetic waves. The measurements of SE were carried out in a frequency range from 100 MHz to 2 GHz. The results of the EMI shielding experiments showed that the maximum electromagnetic shielding effectiveness (EMSE) values of sandwich type C/A/C (carbon fiber sheet/aluminum foil tape/carbon fiber sheet) and C/Ni/C (carbon fiber sheet/magnetic shielding foil/carbon fiber sheet) samples were 55 dB and 113 dB, respectively, at a frequency of 1.9 GHz.