• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.234-237
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• 2001

In this study, efforts were made to understand the propagation of electromagnetic wave through the foam core sandwich structure by the analytical model. Foam core sandwich structure is composed of glass/epoxy composite skins and foam core. Transmittance and reflectance of the arbitrary linearly polarized incident TEM waves through the unidirectional composites, foam and foam core sandwich structures were determined as functions of thickness, fiber orientation of composites, incident angle and polarization angle by the analytical model. From the results of the analysis, the general tendency of transmittance and reflectance of electromagnetic wave through composites, foam and foam core sandwich structures was obtained.

• 한국구조물진단유지관리공학회 논문집
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• 제25권5호
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• pp.157-164
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• 2021

최근 미세먼지와 관련된 환경문제를 개선하기 위해 유해물질을 제거할 수 있는 광촉매와 흡착제에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 전체 공극량이 일반 건설재료에 비해 상당히 큰 폼 콘크리트에 다량의 마이크로 공극를 갖는 야자계 활성탄소를 이용해서 다공성 폼 복합체를 제작하였다. 미세먼지 흡착 가능성을 평가하기 위해 제작된 폼 복합체에 대해 공극 구조를 분석하였다. 폼 복합체의 공극구조 분석은 측정된 질소 흡착등온선으로부터 BET와 Harkins-jura이론을 적용하였다. 분석결과 활성탄소를 혼입한 폼 복합체의 비표면적과 마이크로 공극 부피가 Plain보다 크게 증가하였다. 활성탄소 혼입율이 증가할수록 폼 복합체의 비표면적과 마이크로 공극 부피가 증가하는 경향을 나타냈다. 이는 폼 복합체가 가스상의 미세먼지 전구물질 NO_X에 대한 흡착성능이 높을 것으로 보인다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.183-186
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• 2001

In this paper, the analytical model to understand the propagation of electromagnetic waves in the foam core sandwich structures was proposed. Using the analytical model, efforts were made to find the optimal stacking sequence of composite skins for maximum transmittance of electromagnetic wave. Numerical analyses of unidirectional composites and foam as a function of incident angle were performed. From the results of analysis, the general tendencies of transmittance of electromagnetic wave through composites and foam were obtained. Based on the general tendencies, optimal stacking sequences of composite skins for the maximum transmittance of electromagnetic wave were found with certain ranges of incident angle using genetic algorithm(GA).

• Steel and Composite Structures
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• 제17권2호
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• pp.159-172
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• 2014

A finite element model with the consideration of damage initiation and evolution has been developed for the analysis of the dynamic response of a composite sandwich panel subject to low velocity impact. Typical damage modes including fiber breakage, matrix crushing and cracking, delamination and core crushing are considered in this model. Strain-based Hashin failure criteria with stiffness degradation mechanism are used in predicting the initiation and evolution of intra-laminar damage modes by self-developed VUMAT subroutine. Zero-thickness cohesive elements are adopted along the interface regions between the facesheets and the foam core to simulate the initiation and propagation of delamination. A crushable foam core model with volumetric hardening rule is used to simulate the mechanical behavior of foam core material at the plastic state. The time history curves of contact force and the core collapse area are obtained. They all show a good correlation with the experimental data.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.381-382
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• 2006

The mechanical behaviors of multi-layered foam core sandwich composite were investigated through a 3-point bending test. The sandwich specimens were obtained from sandwich panel consisting of aluminum faces and urethane foam core. Three types of sandwich specimens such as a single structure, a double structure and a triple structure were considered. The span of sandwich specimens were varied from 170mm to 350mm. According to the results, the flexural and shear properties of multi-layered sandwich composite were found to be higher than those of single-layered sandwich composite.

• 대한금속재료학회지
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• 제48권2호
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• pp.109-115
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• 2010

In the present study, a Zr-based amorphous alloy matrix composite reinforced with tungsten porous foam was fabricated without pores or defects by liquid pressing process, and its microstructures and mechanical properties were investigated. About 69 vol.% of tungsten foam was homogeneously distributed inside the amorphous matrix, although the matrix of the composite contained a small amount of crystalline phases. The compressive test results indicate that the composite was not fractured at one time after reaching the maximum compressive strength, but showed considerable plastic strain as the compressive load was sustained by tungsten foam. The tungsten foam greatly improved the strength (2764 MPa) and ductility (39.4%) of the composite by homogeneously dispersing the stress applied to the matrix. This was because the tungsten foam and matrix were simultaneously deformed without showing anisotropic deformation due to the excellent bonding of tungsten/matrix interfaces. These findings suggest that the liquid pressing process is useful for the development of amorphous matrix composites with improved strength and ductility.

• 마이크로전자및패키징학회지
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• 제30권1호
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• pp.55-62
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• 2023

본 연구에서는 서로 다른 Pore per inch (PPI, 1 inch 당 pore의 수)를 갖는 Ni-foam 사이에 Sn-3.0Ag-0.5Cu(wt.%, SAC305) 솔더 침지 공정을 수행하여 Ni-foam/SAC305 복합 솔더를 제조한 후, 이를 천이액상 확산 접합(Transient liquid Phase bonding, TLP bonding) 공정에 적용하여 형성된 접합부의 미세구조 분석 및 기계적 특성 평가가 수행되었다. 제조된 Ni-foam/SAC305 복합 솔더 프리폼 (Solder preform)은 Ni-foam 및 SAC305로 구성되었으며, Ni-foam 계면에는 (Ni,Cu)₃Sn₄ 조성의 금속간 화합물이 형성되었다. TLP 접합 공정 수행 시, Ni-foam 계면의 금속간 화합물은 (Ni,Cu)₃Sn₄+Au로 변환 되었으며, 접합 시간이 증가할수록 Ni-foam과 SAC305가 지속적으로 반응하면서 접합부는 금속간 화합물로 변환되었다. 130 PPI Ni-foam/SAC305 복합 솔더 접합부가 가장 빠른 속도로 금속간 화합물로 변화되는 것을 확인하였다. 기계적 특성에 미치는 Ni-foam의 영향을 확인하기 위해 전단 시험 수행 결과, TLP 접합 초기에 모든 조건의 솔더 접합부는 50 MPa 이상의 우수한 기계적 특성을 나타내었으며, 접합 시간이 증가할수록 전단 강도는 증가하는 경향을 나타내었다.

• 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.

• Structural Engineering and Mechanics
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• 제12권2호
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• pp.169-188
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• 2001

This note presents the main results of an experimental investigation into the mechanical behaviour of a composite sandwich conceived as a lightweight material for naval engineering applications. The sandwich structure is formed by a three-dimensional glass fibre/polymer matrix fabric with transverse piles interconnecting the skins; the core is filled with a polymer matrix/glass microspheres syntactic foam; additional Glass Fibre Reinforced Plastics extra-skins are laminated on the external facings of the filled fabric. The main features of the experimental tests on syntactic foam, skins and sandwich panels are presented and discussed, with focus on both in-plane and out-of-plane responses. This work is part of a broader research investigation aimed at a complete characterisation, both experimental and numerical, of the complex mechanical behaviour of this composite sandwich.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.407-414
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• 2002

The knowledge of interaction of electromagnetic waves in composite structures is important for designing the shielding structure for antenna such as radome. Recently, radomes are constructed in the form of foam core sandwich structures that have many mechanical advantages such as high strength, long fatigue life, low density and adaptability to the intended function of structure. However, the propagation of electromagnetic waves is affected by high anisotropic permeability and loss tangent of the composite skin. In this study, the analytical model to understand the propagation of electromagnetic waves in the anisotropic composites and foam core sandwich structures with composite skins was proposed. Numerical analyses of unidirectional composites and foam core sandwich structure as a function of incident angle were performed. From the results of analysis, the general tendencies of transmittance of electromagnetic wave through composites and foam core sandwich structure were obtained.