• 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.

• 해양환경안전학회지
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• 제26권3호
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• pp.286-296
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• 2020

Sandwich structures are general-purpose structures that can reduce the structural weight of composite ships. Core materials are essential for these structures, with polyvinyl chloride (PVC) foams being the most popular. These foam core materials are subjected to various tests in the development process, and must satisfy the performance requirements of several ISO and ASTM standards. Therefore, a procedure for evaluating the performance of foam core materials was proposed in this paper. In addition, prototypes were fabricated using a commercial PVC foam core product in accordance with the structural design of an 11 m fiber-reinforced plastic yacht. Then, a case study was conducted on the proposed evaluation procedure. The proposed procedure facilitates the understanding of the performance requirements and evaluation of core materials used in composite ships and is expected to be utilized in developing core materials for marine structures.

• International Journal of Aerospace System Engineering
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• 제10권2호
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• pp.1-4
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• 2023

Even though the recent development trend of wind turbine systems has been focused on larger MW Classes, the small-scale wind turbine system has been continuously developed because it has some advantages due to easy personnel establishment and use with low cost and energy saving effect. This work is to propose a specific structural design and analysis procedure for development of a low noise 500W class small wind turbine system which will be applicable to relatively low wind speed region like Korea. The proposed structural feature has a skin-spar-foam sandwich composite structure with the E-glass/Epoxy face sheets and the Urethane foam core for lightness, structural stability, low manufacturing cost and easy manufacturing process. Moreover this type of structure has good behaviors for reduction of vibration and noise. Structural analysis including load cases, stress, deformation, buckling and vibration was performed using the Finite Element Method. In order to evaluate the designed blade structure the structural tests were done, and their test results were compared with the estimated results.

• Steel and Composite Structures
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• 제28권4호
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• pp.461-470
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• 2018

In this study, the effect of polyurethane foam filler, in addition to surface layer thickness and core material thickness, on vibration characteristics of sandwich structures was investigated. The manufacturing process was carried out according to the Taguchi method. The natural frequencies and damping ratios of the produced samples were determined experimentally for fixed-free boundary conditions. In addition, solid models were developed for test samples and their finite element analyses were performed with $ANSYS^{(R)}$ to obtain their natural frequencies and mode shapes. An acceptably good agreement was found with the comparison of experimental results with the numerically obtained ones. The most effective parameters on the vibration characteristics of the sandwich structure were determined by the Taguchi method.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.429-434
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• 2005

In this paper sandwich structures like beams and plates are optimised by using parametric study. The structures are composed of fibre reinforced composites for facial material and resin concrete and PVC foam for core materials. The stacking sequences and thickness of the composites are controlled as major parameters to find out the optimal condition for machine tool components. For the plate structure for machine tool bed composites-skined sandwich structure which has several ribs are proposed to enhance both directional bending stiffnesses at the same time. From the results optimal configuration and materials for high precesion machine tools are proposed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1367-1368
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• 2013

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.194-197
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• 2004

In this paper, compressive characteristics of carbon fabric skin with polymeric foam core sandwich structure were investigated by FE analyses and compressive tests of polyurethane foam were also conducted with respect to temperature changes, which were determined by curing processes of epoxy or polyester resin to obtain mechanical behaviour of polyurethane foam. FE analyses indicated variation of parameters with respect to manufacturing pressure, which have comparatively massive effect upon mechanical properties of sandwich structures, i.e. wavelength as well as crimp angle of carbon fabric

• 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.

• 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.

• Composites Research
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• 제12권6호
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• pp.74-82
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• 1999

폴리 우레탄 폼 코아 샌드위치 복합재료의 정적 및 피로 특성에 대하여 연구하였다. 유리 섬유강화 스킨과 중합의 폼 코아를 갖는 비스티칭, 스티칭, 스티프너의 세 종류 시편이 사용되었다. 특히 스티칭 샌드위치 구조는 두께 방향에 대하여 폴리에스터와 유리섬유를 꼬아서 부가적인 구조 보강이 코아의 상하 표면을 통하여 꿰멘 구조로 층간분리를 최소화하기 위해 샌드위치 구조 패널을 스티칭하여 만들고 수지는 수지의 유동 온도에서 수지의 낮은 점도 특성을 이용하여 스티칭 섬유에 침투시켜 함께 경화하였다. 스티칭 섬유가 $50{\times}50{\;}mm$의 간격으로 스티칭된 시편 및 스티프너 시편의 굽힘강도는 비스티칭 시편과 비교하여 각각 50%및 10배 이상으로 향상되었다. 최대 하중의 20%크기로 $10^6$ 피로 사이클을 받은 후, 비스티칭 시편의 굽힘 피로강도는 정적 굽힘강도와 비교하여 27%까지 감소되었고, 스티칭된 시편은 39%,그리고 스티프너에 의하여 보강된 시편은 20%정도 감소되었다. 폴리우레탄 폼 코아의 에이징 효과를 입증하기 위해, 피로 시험 후 샌드위치 시편의 표면 적층의 손상은 초음파 C-scan장비를 사용하여 검출하였다. 초음파 C-scan결과로부터 피로 시험동안 손상 받은 어떤 결함도 없었다 이는 피로 사이클동안 폼 코아 샌드위치 구조에 대한 굽힘강도의 감소는 폴리우레탄 폼이 에이징되어 발생하는 것을 의미한다.