• Composites Research
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• 제28권1호
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• pp.15-21
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• 2015

본 논문에서는 해양레저분야에서의 현재 복합재 적용 현황과 33피트급 아메리카스컵 훈련용 세일링 요트 개발에 대해 기술한다. 항공분야와 달리 해양레저 분야에서의 복합재료는 최근에서야 적용 및 사용이 되기 시작했다. 다양한 해양레저 구조물 중에서도 특히, 아메리카스컵 세일링 경주 요트는 빠른 속도를 내야 하기 때문에 경량화 및 높은 기계적 성능이 요구되고 이에 따라 경주용 요트를 건조함에 있어 탄소섬유의 사용은 필수적이다. 탄소섬유강화 플라스틱 경주용 요트 제작 과정을 정립하기 위해 탄소 돛대와 탄소 요트 선체에 대한 최적화 설계와 생산 공법에 대해 논의되었다. 최종적으로 이렇게 제작된 탄소섬유강화복합재 세일링 요트는 운항시험을 통해 경주용 요트로써의 높은 성능을 보여주었다.

• Advances in nano research
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• 제9권1호
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• pp.1-13
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• 2020

In this work, the electrical potential (EP) technique with an artificial neural networks (ANNs) for monitoring of nanostructures are used for the first time. This study employs an expert system to identify size and localize hidden nano-delamination (N.Del) inside layers of nano-pipe (N.P) manufactured from Basalt Fiber Reinforced Polymer (BFRP) laminate composite by using low-cost monitoring method of electrical potential (EP) technique with an artificial neural networks (ANNs), which are combined to decrease detection effort to discern N.Del location/size inside the N.P layers, with high accuracy, simple and low-cost. The dielectric properties of the N.P material are measured before and after N.Del introduced using arrays of electrical contacts and the variation in capacitance values, capacitance change and node potential distribution are analyzed. Using these changes in electrical potential due to N.Del, a finite element (FE) simulation model for N.Del location/size detection is generated by ANSYS and MATLAB, which are combined to simulate sensor characteristic, therefore, FE analyses are employed to make sets of data for the learning of the ANNs. The method is applied for the N.Del monitoring, to minimize the number of FE analysis in order to keep the cost and save the time of the assessment to a minimum. The FE results are in excellent agreement with an ANN and the experimental results available in the literature, thus validating the accuracy and reliability of the proposed technique.

• International Journal of Concrete Structures and Materials
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• 제7권1호
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• pp.35-50
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• 2013

Rapid and effective repair methods are desired to enable quick reopening of damaged bridges after an earthquake occurs, especially for those bridges that are critical for emergency response and other essential functions. This paper presents results of tests conducted as a proof-of-concept in the effectiveness of a proposed method using externally bonded carbon fiber reinforced polymer (CFRP) composites to rapidly repair severely damaged RC columns with different damage conditions. The experimental work included five large-scale severely damaged square RC columns with the same geometry and material properties but with different damage conditions due to different loading combinations of bending, shear, and torsion in the previous tests. Over a three-day period, each column was repaired and retested under the same loading combination as the corresponding original column. Quickset repair mortar was used to replace the removed loose concrete. Without any treatment to damaged reinforcing bars, longitudinal and transverse CFRP sheets were externally bonded to the prepared surface to restore the column strength. Measured data were analyzed to investigate the performance of the repaired columns compared to the corresponding original column responses. It was concluded that the technique can be successful for severely damaged columns with damage to the concrete and transverse reinforcement. For severely damaged columns with damaged longitudinal reinforcement, the technique was found to be successful if the damaged longitudinal reinforcement is able to provide tensile resistance, or if the damage is located at a section where longitudinal CFRP strength can be developed.

• 한국공간구조학회논문집
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• 제11권1호
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• pp.97-104
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• 2011

본 연구에서는 막구조 건축물의 유지관리를 위한 막재의 표면 및 코팅층의 열화진단을 수행하였다. 막재는 내화학성능 및 내부식 성능을 포함하는 내구성능이 가장 중요시 되는 재료이다. 일반적으로 대공간 건축물의 지붕재료로 사용되는 막재의 유지관리 진단항목은 막재의 표면 열화진단, 막재의 코팅층 열화진단, 막재의 코팅층 및 섬유포 사이의 열화진단, 막재 전면에 걸친 열화진단, 로프의 열화진단, 보강벨트의 열화진단, 커버고무 등의 열화진단 등으로 대별된다. 본 연구는 대공간 건축물의 지붕재료로 많이 사용되는 PVDF계 막재를 대상으로 표면 및 코팅층의 열화도 진단 결과를 보고한다.

• 한국기계가공학회지
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• 제15권3호
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• pp.130-134
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• 2016

Due to the need for advanced technologies in the automotive industry, the demand for lighter and safer vehicles has increased. Even though various nonferrous metals, like Aluminum, Magnesium and also Carbon Fiber Reinforced Plastic (CFRP), have been implemented in the automotive industry, a lot of technical research and development is still focused on ferrous metals. In particular, the market volume of High Strength Steel (HSS) parts and Ultra High Strength Steel (UHSS) by hot press forming parts has expanded significantly in all countries' automotive industries. A new tool steel, High Thermal-Conductivity Tool Steel (HTCS), for stamping punches and dies has been developed and introduced by Rovalma Company (Spain), and it is able to support better productivity and quality during hot press forming. The HTCS punches and dies could help to reduce cycle time due to their high thermal conductivity, one of the major factors in hot press forming operation. In this study, test dies were manufactured in order to verify the high thermal conductivity of HTCS material compared to SKD6. In addition, thermal deformation was inspected after the heating and cooling process of hot press forming. After heating and cooling, the test dies were measured by a 3D scanner and compared with the original geometry. The results showed that the thermal deformation and distortion were very small even though the cooling time was reduced by 2 seconds.

• 한국항공우주학회지
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• 제36권12호
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• pp.1201-1206
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• 2008

본 연구는 과학기술위성3호 개발을 위한 proto 모델의 진동모드 특성 규명에 관한 것이다. 과학기술위성3호(STSAT-3)의 구조체는 탄소섬유강화복합재료 면재(skin)를 가진 허니컴 샌드위치패널로 설계되었으며, 고유진동수 설계 요구조건을 만족하면서 최적의 복합재 구조체를 결정하기 위하여 다수의 예비형상 모델이 개발되었다. 유한요소해석을 통하여 각 예비 형상 모델에 대한 모드특성이 해석되었고 그 결과들이 서로 비교 검토 되었다. 본 연구를 통하여 내부 지지 패널을 가진 직육면체 박스구조 형태가 타 모델에 비하여 상대적으로 높은 첫 번째 고유진동수를 가지고 강성이 높다는 결과를 얻었다. 또한 해석된 모델 모두 첫 번째 모드는 횡방향의 굽힘모드인 것으로 나타났다.

• 비파괴검사학회지
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• 제29권4호
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• pp.293-298
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• 2009

본 연구에서는 나노 표면층의 특성 평가를 위해 원자현미경에 초음파 특성을 결합하여 초음파 원자 현미경을 개발하였다. 초음파 원자 현미경은 기존의 나노 표면층에 대한 토포그래프 이미지뿐만 아니라 국부적인 이종부분으로 이루어진 표면에서의 물리적 특성차이에 의한 표면의 탄성 특성 이미지를 얻을 수 있다. 본 연구에서는 프로토타입의 UAFM 장치를 구성하고 이를 몇몇 응용분야에 적용하였다. 구축한 프로토타입의 UAFM 시스템을 이용하여 증착 실리콘 박막층과 냉간 압조용 강의 구상화 그리고 탄소 섬유 강화 복합재료의 표면에 대한 탄성 이미지를 성공적으로 얻을 수 있었다.

• 한국강구조학회 논문집
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• 제16권4호통권71호
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• pp.493-500
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• 2004

본 논문에서는 복합재료로 이루어진 원통형 쉘 구조물을 해석모델로 설정하였으며, 좌굴의 링 보강재 보강효과에 대해서 연구하였다. 유한요소법으로 해석을 수행하였으며, 보강재의 요소는 3차원 보요소를 사용하였고, 쉘 요소는 적용성이 뛰어난 평면쉘요소를 사용하였으며, 대체 전단 변형률장을 도입하여 잠김현상을 극복하였다. 본 연구에서 링 보강재는 횡리브(Rib)의 형태이다. 이러한 보강재가 원통형 쉘의 좌굴에 미치는 영향을 고찰하였다. 즉, 보강재의 위치 변화, 보강재의 크기 변화, 쉘의 변장비 변화, 쉘의 지점조건의 변화, 복합재료의 화이버 보강각도 변화 등 다양한 파라미터 연구를 통해서 쉘의 좌굴거동을 분석하였다. 여러가지 설계변수에 대한 보강된 쉘의 거동에 대한 정확한 이해로부터 효율적인 보강설계를 제시하고자 하였으며, 원통형 쉘의 좌굴해석시 좋은 참고자료로 활용할 수 있으리라 기대된다.

• 복합신소재구조학회 논문집
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• 제5권1호
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• pp.1-8
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• 2014

Pultruded glass fiber reinforced polymeric plastic (PFRP) and FRP member manufactured by sheet molding compound (SMC) have superior mechanical and physical properties compared with those of conventional structural materials. Since FRP has an excellent corrosion-resistance and high specific strength and stiffness, the FRP material may be highly appreciated for the development of floating-type photovoltaic (PV) power generation system. In this paper, advanced floating PV generation system made of PFRP and SMC is designed. In the design, it includes tracking solar altitude by tilting photovoltaic arrays and tracking solar azimuth by spinning structures. Moreover, the results of the finite element analysis (FEA) are presented to confirm stability of entire structure under the external loads. Additionally, installation procedure and mooring systems in the Hap-Cheon Dam are discussed and the measurement of strain under the actual circumstances is conducted for assuring stability of actually installed structures. Finally, by comparison with allowable stress, appropriate safety of structure is confirmed to operate the system.

• 한국도로학회논문집
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• 제17권6호
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• pp.1-9
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• 2015

PURPOSES : The objective of this study is to propose a quality control and quality assurance method for use during asphalt pavement construction using non-destructive methods, such as ground penetrating radar (GPR) and an infrared (IR) camera. METHODS : A 1.0 GHz air-coupled GPR system was used to measure the thickness and in situ density of asphalt concrete overlay during the placement and compaction of the asphalt layer in two test construction sections. The in situ density of the asphalt layer was estimated based on the dielectric constant of the asphalt concrete, which was measured as the ratio of the amplitude of the surface reflection of the asphalt mat to that of a metal plate. In addition, an IR camera was used to monitor the surface temperature of the asphalt mat to ensure its uniformity, for both conventional asphalt concrete and fiber-reinforced asphalt (FRA) concrete. RESULTS : From the GPR test, the measured in situ air void of the asphalt concrete overlay gradually decreased from 12.6% at placement to 8.1% after five roller passes for conventional asphalt concrete, and from 10.7% to 5.9% for the FRA concrete. The thickness of the asphalt concrete overlay was reduced from 7.0 cm to 6.0 cm for the conventional material, and from 9.2 cm to 6.4 cm for the FRA concrete. From the IR camera measurements, the temperature differences in the asphalt mat ranged from $10^{\circ}C$ to $30^{\circ}C$ in the two test sections. CONCLUSIONS : During asphalt concrete construction, GPR and IR tests can be applicable for monitoring the changes in in situ density, thickness, and temperature differences of the overlay, which are the most important factors for quality control. For easier and more reliable quality control of asphalt overlay construction, it is better to use the thickness measurement from the GPR.