• 센서학회지
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• 제16권6호
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• pp.441-448
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• 2007

In this study, the fiber-optic fluoro-immunosensor was designed to detect foodborne pathogens. The fabricated system is composed of the multimode optical fiber on which antibodies are immobilized. Then, a sandwich immunoassay is applied to the fabricated the fiber-optic fluoro-immunosensor. In the "sandwich" binding format, a primary or "capture" antibody is immobilized on the core surface of the multimode optical fiber and a secondary or named as "tracer" antibody is added to the bulk solution. A tracer is labeled FITC (fluorescein isothiocyanate; ${\lambda}ex$=492 nm, ${\lambda}em$= 520 nm). Different concentrations of antigens are tested in different fibers. The detection limit of the fabricated system is 5.08×103 cfu/ml for Vibrio antigen and $0.1{\mu}g/ml$, $0.05{\mu}g/ml$ in non-labeled monolayer phosphate buffered saline (NMP), non-labeled monolayer carbonate bicarbonate buffer (NMC), respectively.

• Composites Research
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• 제21권1호
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• pp.22-29
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• 2008

본 논문은 유리섬유 에폭시 면재에 알루미늄 하니컴 샌드위치 복합재가 적용된 저상버스 차체에 대한 정면충돌과 전복에 대한 특성에 대해 연구하였다. 이때 충돌과 전복 해석은 외연유한요소 해석 프로그램인 LS-DYNA3D를 이용하였다. 차체 구조물에 적용되는 적층 복합재 면재에 대해 기계적 특성시험을 통하여 물성을 획득하였고, 직교이방성 특성을 갖는 하니컴 심재의 물성은 유효등가손상 모델을 적용하였다. 저상버스의 충돌 해석은 60km/h의 속도로 정면충돌 사고를 모사하여 해석을 수행하였고, 전복해석은 유럽 안전법규 ECE-R66의 시험 방법을 고려하여 해석하였다. 저상버스의 정면충돌과 전복에 대해 운전자와 승객의 생존 공간 안전성에 관한 결과를 보여준다. 또한, 수정된 Chang-Chang 파손기준식은 충돌과 전복해석에 대한 복합재 구조물의 파손 모드 예측에 추천된다.

• Steel and Composite Structures
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• 제44권4호
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• pp.503-517
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• 2022

This paper presents the mechanical buckling of bi-directional functionally graded sandwich beams (BFGSW) with various boundary conditions employing a quasi-3D beam theory, including an integral term in the displacement field, which reduces the number of unknowns and governing equations. The beams are composed of three layers. The core is made from two constituents and varies across the thickness; however, the covering layers of the beams are made of bidirectional functionally graded material (BFGSW) and vary smoothly along the beam length and thickness directions. The power gradation model is considered to estimate the variation of material properties. The used formulation reflects the transverse shear effect and uses only three variables without including the correction factor used in the first shear deformation theory (FSDT) proposed by Timoshenko. The principle of virtual forces is used to obtain stability equations. Moreover, the impacts of the control of the power-law index, layer thickness ratio, length-to-depth ratio, and boundary conditions on buckling response are demonstrated. Our contribution in the present work is applying an analytical solution to investigate the stability behavior of bidirectional FG sandwich beams under various boundary conditions.

• 한국항공우주학회지
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• 제38권1호
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• pp.29-34
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• 2010

본 연구에서는 새롭게 개발된 "강도 향상 인써트"에 대해 조인트 시편을 제작하여 Pull-out 및 전단시험을 수행하여 보통 인써트의 조인트 강도와 비교하고 그 파손 특성을 조사하였다. 이를 통해 새로운 인써트에 대한 성능을 확인하였다. 시험 결과, 새로운 "강도 향상 인써트"는 기존의 보통 인써트에 비해 Pull-out 강도는 2.1배, 전단강도는 2.04배 향상되는 것을 확인하였다. 따라서 향후 높은 인써트 강도를 요구하는 구조에 유용하게 사용될 수 있을 것이다.

• Steel and Composite Structures
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• 제24권1호
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• pp.23-35
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• 2017

Current form of Corrugated-strip connectors are not popular due to the fact that the two ends of this form need to be welded to steel face plates. To overcome this difficulty, a new system is proposed in this work. In this system, bi-directional corrugated-strip connectors are used in pairs, and only one of their ends is welded to the steel face plates on each side. The other end is embedded in the concrete core. To assemble the system, common welding devices are required, and welding process can be performed in the construction sites. By performing the Push-out test under static loading, the authors experimentally assess the effects of geometric parameters on ductility, failure modes and the ultimate shear strength of the aforesaid connectors. For this purpose, sixteen experimental samples are prepared and investigated. For fifteen of these samples, one end of the shear connectors is welded to steel face plates, and the other end is embedded in the concrete. Another experimental sample is prepared in which both ends are welded to the steel face plates. According to the achieved results, several relations are proposed for predicting the ultimate shear strength and load vs. interlayer slip (load-slip) behavior of corrugated-strip connectors. Moreover, these formulas are compared with those of the well-known codes and standards. Accordingly, it is concluded that the authors' relations are more reliable.

• 한국정밀공학회지
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• 제23권9호
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• pp.61-67
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• 2006

Sandwich structures, which are composed of a thick core between two faces, are commonly used in many engineering applications because they combine high stiffness and strength with low weight. Accordingly, the usage of sandwich structure is very widely applied to the aircraft, the automobile and marine industry, etc., because of these advantages. In this paper, we have investigated the buckling protection of an inner structure plate and the useful corrugated configuration for contact, and the fabrication method of the inner structure plate for large area using the continuous molding process. Also, we have guaranteed the accuracy of the molding process through the micro corrugated mold fabrication and secured the accuracy and analyzed aspect properties of the inner structure plate fabricated for a large area using the partial mold process. We have compared molding simulation according to the aspect thickness of the corrugated configuration with the molding experiment results.

• 한국항공우주학회지
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• 제40권9호
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• pp.771-780
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• 2012

나로호(KSLV-1)의 3차 발사에 탑재될 나로과학위성(Naro-Science Satellite)의 개발이 성공적으로 완료되었다. 나로과학위성은 100kg급의 소형 과학위성이며 전형적인 알루미늄 골격 구조에 경량 고강도의 알루미늄 허니컴 샌드위치 패널이 부착된 구조이다. 본 연구에서는 나로과학위성의 설계 요구조건에 대한 동적거동을 시험 및 전산구조 유한요소 수치해석적 방법으로 검증하였다. 연구를 통하여 발사체로부터 인가되는 각종 진동 및 외란으로 인한 파괴와 안전율(safety factor) 확보에 대한 위성 구조체 핵심 설계 및 분석기술을 확보하였다. 이러한 시험 및 수치해석 결과를 바탕으로 위성 구조설계의 신뢰성을 확보하고, 첨단 위성설계 기술의 축적을 통하여 차후 개발될 위성의 중요한 자료로 활용한다.

• Smart Structures and Systems
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• 제12권5호
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• pp.483-499
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• 2013

A new piezoceramic $d_{15}$ shear-induced torsion actuation mechanism representative benchmark is proposed and its experimentations and corresponding 3D finite element (FE) simulations are conducted. For this purpose, a long and thin smart sandwich cantilever beam is dimensioned and built so that it can be used later for either validating analytical Saint Venant-type solutions or for analyzing arm or blade-based smart structures and systems applications. The sandwich beam core is formed by two adjacent rows of 8 oppositely axially polarized d15 shear piezoceramic patches, and its faces are dimensionally identical and made of the same glass fiber reinforced polymer composite material. Quasi-static and static experimentations were made using a point laser sensor and a scanning laser vibrometer, while the 3D FE simulations were conducted using the commercial software $ABAQUS^{(R)}$. The measured transverse deflection by both sensors showed strong nonlinear and hysteretic (static only) variation with the actuation voltage, which cannot be caught by the linear 3D FE simulations.

• Advances in nano research
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• 제15권2호
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• pp.175-189
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• 2023

The under-evaluation structure includes a functionally graded porous (FGP) core which is confined by two piezoelectric carbon nanotubes reinforced composite (CNTRC) layers. The whole structure rests on the Pasternak foundation. Using quasi-3D hyperbolic shear deformation theory, governing equations of a sandwich plate are driven. Moreover, face sheets are subjected to the electric field and the whole model is under thermal loading. The properties of all layers alter continuously along with thickness direction due to the CNTs and pores distributions. By conducting the current study, the results emerged in detail to assess the effects of different parameters on buckling of structure. As instance, it is revealed that highest and lowest critical buckling load and consequently stiffness, is due to the V-A and A-V CNTs dispersion type, respectively. Furthermore, it is revealed that by porosity coefficient enhancement, critical buckling load and consequently, stiffness reduces dramatically. Current paper results can be used in various high-tech industries as aerospace factories.

• Steel and Composite Structures
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• 제50권1호
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• pp.63-75
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• 2024

In this paper, the modified couple stress theory (MCST) and first order shear deformation theory (FSDT) are employed to investigate the free vibration and bending analyses of a three-layered micro-shell sandwiched by piezoelectric layers subjected to an applied voltage and reinforced graphene nanoplatelets (GPLs) under external and internal pressure. The micro-shell is resting on an elastic foundation modeled as Pasternak model. The mixture's rule and Halpin-Tsai model are utilized to compute the effective mechanical properties. By applying Hamilton's principle, the motion equations and associated boundary conditions are derived. Static/ dynamic results are obtained using Navier's method. The results are validated with the previously published works. The numerical results are presented to study and discuss the influences of various parameters on the natural frequencies and deflection of the micro-shell, such as applied voltage, thickness of the piezoelectric layer to radius, length to radius ratio, volume fraction and various distribution pattern of the GPLs, thickness-to-length scale parameter, and foundation coefficients for the both external and internal pressure. The main novelty of this work is simultaneous effect of graphene nanoplatelets as reinforcement and piezoelectric layers on the bending and vibration characteristics of the sandwich micro shell.