• International Journal of Safety
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• 제1권1호
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• pp.7-12
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• 2002

This paper demonstrates the impact stresses and wave propagation characteristics of glass/epoxy laminates subjected to the low-velocity impact by a steel ball theoretically and experimentally. A plate finite element model in conjunction with experimental contact laws is used for the theoretical investigation. The specimens for statical indentation and impact test are composed of $[0/45/0/-45/0]_28 and [90/45/90/-45/90]_28$ stacking sequences and have clamped-simply supported boundary conditions. Finally, these two results are compared and then the impulsive stress and wave propagation characteristics of this laminated composite are studied.

• 한국정밀공학회지
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• 제21권2호
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• pp.195-202
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• 2004

This paper presents the fabrication and evaluation of mechanical behavior for a peristaltic micropump by flow simulation. The valve-less micropump using the diffuser/nozzle is consists of the lower plate, the middle plate, the upper plate and the tube that connects inlet and outlet of the pump. The lower plate includes the channel and the chamber, and the plain middle plate are made of glass and actuated by the piezoelectric translator. Channels and a chamber on the lower plate are fabricated on high processability silicon wafer by the DRIE(Deep Reactive Ion Etching) process. The upper plate does the roll of a pump cover and has inlet/outlet/electric holes. Three plates are laminated by the aligner and bonded by the anodic bonding process. Flow simulation is performed using error-reduced finite volume method (FVM). As results of the flow simulation and experiments, the single chamber pump has severe flow problems, such as a backflow and large fluctuation of a flow rate. It is proved that the double-chamber micropump proposed in this paper can reduce the drawback of the single-chamber one.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1186-1190
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• 2003

In this paper, a valveless bubble-actuated fluid micropump was has been developed and its performance was tested. The valveless micropump consists of the lower plate, the middle plate, the upper plate and a resistive heater. The lower plate includes the nozzle-diffuser elements and the double-chamber. Nozzle-diffuser elements and a double-chamber are fabricated on the silicon wafer by the DRIE(Deep Reactive Ion Etching) process. The lower plate also has inlet/outlet channels for fluid flow. The middle plate is made of glass and plays the role of the diaphragm. The chamber in the upper plate is filled with deionized water, and which contacts with the resistive heater. The resistive heater is patterned on a silicon substrate by Ti/Pt sputtering. Three plates and the resister heater are laminated by the aligner and bonded in the anodic bonder. Since the bubble is evaporated and condensed periodically in the chamber, the fluid flows from inlet to outlet with respect to the diffusion effect. In order to avoid backflow, the double chamber system is introduced. Analytical and experimental results show the validity of the developed double-chamber micropump.

• Journal of the Korean Wood Science and Technology
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• 제44권1호
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• pp.30-39
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• 2016

구조용 집성재 라멘 접합부에 일반적으로 사용되는 접합철물을 대신하여 단판과 Glass Fiber Reinforced Plastic (GFRP)를 복합시킨 GFRP 보강적층판과 삽입 접착형 GFRP rod를 접합물로 사용하여 낙엽송 집성재 문형라멘 구조의 수평가력 성능평가를 실시하였다. 실험결과 GFRP rod와 에폭시 접착제를 이용한 삽입 접착형 접합부는 기존의 접합철물을 이용한 실험체와 비교하여 항복내력, 종국내력, 초기강성이 각각 49%, 52%, 61% 낮게 측정되었다. 이러한 접합부는 GFRP rod와 집성재 간의 접착력이 중요한 내력 기구로 현장적용 시 문제가 발생할 수 있는 가능성이 크다고 판단된다. 반면, GFRP 보강적층판과 목재(Eucalyptus marginata)핀을 이용한 실험체는 집성재 슬릿 접합부의 단면적 손실이 큼에도 불구하고 항복내력, 종국내력, 초기강성, 소성률이 전부 3% 이내로 측정되었다. 게다가 사이클에 대한 강성변화율도 35%로 가장 낮게 측정되며 접합철물을 이용한 실험체와 거의 동등한 성능을 발휘한 것을 확인하였다.

• Journal of the Korean Wood Science and Technology
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• 제43권6호
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• pp.868-875
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• 2015

목구조물 접합부에 기존의 슬릿(slit)형 강판을 대체하기 위해서 FRP (Fiber Reinforced Plastic) 보강적층판을 제작하였다. 보강재, 접착제 종류에 따라 총 4가지 타입의 FRP 보강적층판을 제작하였으며, 접합부 적용 전 KSF 3021과 KSF 2160에 의거한 박리실험과 ASTM D5045-99에서 제안한 Compact Tension (CT)형 파괴인성 시험을 실시하였다. 접착성능 시험결과 GFRP textile, GFRP sheet, GFRP Textile-Sheet 타입의 FRP 보강적층판은 침지 및 내수침지박리 시험에서 모두 KS 기준인 박리율 5% 이하를 만족하였다. 그러나 Aramid 타입의 시험편은 침지박리율 4.8%로 기준을 만족하였으나 내수침지박리율 70%로 합격기준을 만족하지 못하였다. 파괴인성 시험결과 단판만을 교차적층 시킨 대조군시험편보다 목재 대비 보강재 체적비를 23%로 함으로서 FRP 보강적층판의 내력이 2~4배 증가하였다. 그중에서도 GFRP Textile-Sheet 타입의 시험편이 하중 평행방향의 유리섬유 배열로 인해 할렬파단을 억제하면서 대조군 대비 응력확대계수 비가 61% 증가되어 파괴를 가장 크게 억제하는 것으로 확인되었다. FRP 보강적층판과 비금속 dowels을 사용한 접합부의 인장형 전단내력은 금속접합에 비해 약 12% 낮은 내력이 측정되었다.

• Composites Research
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• 제35권1호
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• pp.42-46
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• 2022

탄소섬유 복합재를 제작하였을 때, 함께 적층되는 유리섬유 부직포 개수 및 적층 순서에 따른 기공률과 기계적 물성 간의 상관관계를 확인하였다. 탄소섬유 복합재는 고 투과성 물질인 유리섬유 부직포를 함께 적층 하여 진공 수지 이송 성형 법(vacuum assisted resin transfer molding, VARTM)을 통해 제작하였다. 기공률은 시편의 단면을 광학현미경으로 촬영 후 MATLAB의 기공률 계산 코드를 통해 측정하였고, 기계적 물성은 인장시험을 통해 인장 강도 및 인장 강성, 굽힘 강도, 굽힘 강성을 측정하였다. 또한, 기공률과 기계적 물성 간의 상관관계를 확인하기 위해 두 변수간 피어슨 상관계수를 계산하였다. 결과적으로 유리섬유 부직포의 개수가 증가할수록, 적층 시 중심에서 멀어질수록 기공률이 증가하는 것을 확인할 수 있었다. 또한, 인장 강도 및 인장 강성은 기공률과 약한 양의 상관관계를 보였다. 또한, 인장 강도 및 강성에 기공률만이 미치는 영향을 확인하기 위해 고전 적층 판 이론으로 계산한 기계적 물성과 실험값을 비교하였으며, 인장 강도의 차이는 기공률에 강한 양의 상관관계를 인장 강성은 약한 양의 상관관계를 보였다.

• Structural Engineering and Mechanics
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• 제71권3호
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• pp.283-290
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• 2019

In global competition manufacturing companies have to produce modern, new constructions from advanced materials in order to increase competitiveness. The aim of my research was to develop a new composite cellular plate structure, which can be primarily used for structural elements of road, rail, water and air transport vehicles (e.g. vehicle bodies, ship floors). The new structure is novel and innovative, because all materials of the components of the newly developed structure are composites (laminated Carbon Fiber Reinforced Plastic (CFRP) deck plates with pultruded Glass Fiber Reinforced Plastic (GFRP) stiffeners), furthermore combines the characteristics of sandwich and cellular plate structures. The material of the structure is much more advantageous than traditional steel materials, due mainly to its low density, resulting in weight savings, causing lower fuel consumption and less environmental damage. In the study the optimal construction of a given geometry of a structural element of a road truck trailer body was defined by single- and multi-objective optimization (minimal cost and weight). During the single-objective optimization the Flexible Tolerance Optimization method, while during the multi-objective optimization the Particle Swarm Optimization method were used. Seven design constraints were considered: maximum deflection of the structure, buckling of the composite plates, buckling of the stiffeners, stress in the composite plates, stress in the stiffeners, eigenfrequency of the structure, size constraint for design variables. It was confirmed that the developed structure can be used principally as structural elements of transport vehicles and unit load devices (containers) and can be applied also in building construction.

• 한국안전학회지
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• 제27권1호
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• pp.55-62
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• 2012

Steel plate or FRP materials have been typically used for the seismic retrofit of civil infrastructures. In order to overcome the limitation of each retrofitting material, a composite material, which takes advantages from both metal and fiber polymer materials, has been developed. In the study herein, the composite retrofitting material consists of metal part(steel or aluminum) and FRP sheet part(glass or carbon fiber). The metal part can enhance the ductility and the FRP part the ultimate strength. As a preliminary study to investigate the fundamental mechanical characteristics of the metal-FRP laminated composite material this study performed the flexural fracture test with various experimental variables including the number, the angle and the combination of FRP laminates. From the aluminum-FRP composite tests no great increase in flexural strength and flexural toughness were observed. However, flexural toughness of steel-FRP laminate composite was increased so that its behavior can be considered in the retrofit design. In addition, the angle and the kind of fibers should be carefully considered in conjunction with the expected loading conditions.

• 한국안전학회지
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• 제26권6호
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• pp.54-63
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• 2011

Steel plate or FRP materials have been typically used for the seismic retrofit of civil infrastructures. In order to overcome the limitation of each retrofitting material, a composite material, which takes advantages from both metal and fiber polymer materials, has been developed. In the study herein, the composite retrofitting material consists of metal part(steel or aluminum) and FRP sheet part(glass or carbon fiber). The metal part can enhance the ductility and the FRP part the ultimate strength. As a preliminary study to investigate the fundamental mechanical characteristics of the metal-FRP laminated composite material this study performed the tensile test with various experimental variables including the number, the angle and the combination of FRP laminates. From the test results, both aluminum and steel-FRP laminate composite material showed increased fracture toughness. However, the angle and the kind of fibers should be carefully considered in conjunction with the expected loading conditions. In general, steel-FRP laminate composite showed better tensile performance in regards to the seismic retrofit purposes.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.191-204
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• 2015

Control of the mechanical behavior of composite materials and structures under monotonic and dynamic loads for cracks and damage is a vast and complex area of research. The modeling of the different physical phenomena and behavior characteristics of a composite material during deformation play an important role in the structural design. Our study aims to analyze numerically the energy release rate parameter G of a composite laminated plate (glass or boron / epoxy) cross-ply [$+{\alpha}$, $-{\alpha}$] in the presence of a crack between two circular notches under the effect of several parameters such as fiber orientation ${\alpha}$, the crack orientation ${\beta}$, the orientation ${\gamma}$ of the two considered circular notches and the effect of mechanical properties. Our results show clearly that both notches orientation has more effect on G than the cracks and fibers orientations.