• International Journal of Aeronautical and Space Sciences
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• v.14 no.4
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• pp.350-355
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• 2013

Electrical resistance change measurements were performed, to detect fatigue damage of a quasi-isotropic CFRP and cross-ply CFRP laminates. A four-probe method was used to measure the exact electrical resistance change. A three-probe method was used to measure the electrical contact resistance change, during long cyclic loading. The specimen side surface was observed using a video-microscope to detect damage. The measured electrical resistance changes were compared with the observed damage. The results of this study show that the electrical resistance increase of the quasi-isotropic laminate was caused by a delamination crack between ${\pm}45^{\circ}$ plies. Matrix cracking caused a small electrical resistance increase of the cross-ply laminate, but the decreased electrical resistance caused by the shear-plastic deformation impedes matrix-cracking detection.

• Journal of the Korean Ceramic Society
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• v.43 no.4 s.287
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• pp.253-258
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• 2006

In the lamination process of multi-layer ceramic modules, the occurrence of delamination comes into repeatedly. To completely improve the lamination process of LTCC sheets, a binder film was introduced between the layers. The binder film did not originate the delamination until the thickness under $40{\mu}m$. After lamination, the thickness of the binder film was determined by the infilteraion of binder by the pressure, and after the bake-out, was dependent on the decomposition of binder resin. Any detectable defect was not observed in the multilayer structure with Ag inner electrodes.

• Journal of Applied Reliability
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• v.7 no.1
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• pp.1-11
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• 2007

This paper presents a derating design approach for reliability improvement of a regulator IC. The IC is usually used in SMPS. The main failure mechanism of interest is voltage drop due to the package delamination mainly caused by two stresses, i.e. temperature and current. The lifetime under stresses is modeled as a function of stresses and time using accelerating life testings. Quantitative and qualitative variation in lifetime according to stress variations are investigated using the modeled lifetime. Stress levels would be determined to achieve required reliability levels in the aspect of derating design for reliability.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.121-121
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• 2013

수소로 희석된 벤젠 가스를 반응 가스로 이용하여 합성된 DLC 박막의 마찰 마모 특성을 평가하기 위하여, 일반 대기 환경 및 수중 환경에서 마모 실험을 수행하였다. 일반 대기 환경에서는 박막의 기계적 특성, 마찰 계수 및 마모 거동이 거의 변화하지 않았다. 반면, 수중 환경에서는 마찰 계수가 대기 환경에서보다 안정적으로 평가되었다. 이는 DI-water가 윤활제(lubricant) 역할을 하기 때문으로 예측된다. 또, 수중 환경에서의 마모 실험 결과, 수소가 희석되지 않은 반응 가스를 이용하여 증착 된 DLC 박막의 경우, delamination wear가 상대적으로 많이 관찰되었다. 하지만, 반응 가스에 희석 된 수소량이 증가함에 따라서, 이런 delamination wear가 현저하게 억제됨을 관찰하였다.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.698-703
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• 2004

In this study, mode I interlaminar fracture phenomena of carbon fabric/epoxy composite for tilting train were investigated. Specimens were 25mm $\times$ 180mm $\times$ 4.7mm with an initial artificial delamination of 65mm at one end. This delamination with the thickness of 12.5$\mu$m and 25$\mu$m (teflon film) was used. Mode I interlaminar fracture toughness was measured using the double cantilever beam and the fractured surfaces were examined through a scanning electron microscope. The experimental results obtained in this study would be applicable in the design and structural analysis of the composite structures.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.809-814
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• 1998

Recently many cases that using strengthening method with a steel plate or carbon-fiber sheet in a construction field are increasing. In this reason, it is demanded that developing a plan of preventing delamination of strengthening material. So in this research, for the case of strengthening method of steel plate, it is made use of notch and anchor bolt and for the case of carbon fiber sheet, it is made use of notch, anchor bolt, line anchor and shear strengthening. After all the cases were applied, we made 15 specimen beams. The beams was measured and analyzed about the behavior property of strengthened beams, the ability strengthening method, the relation between load and the shape of failure, the crack load, the yield load, the shape of crack pattern, the increasing rate from yield load and maximum load and the strain of rebar. All the strengthening methods results in almost same value until the yield load, and it wasn't quite different from the theoretical value. But for the case of increasing rate from the yield load and maximum load, comparing with the existing method, the new strengthening methods are proved to be profitable about the safety.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.243-246
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• 2005

This paper focuses on the flexural behavior of RC beams externally reinforced using Carbon Fiber Reinforced Plastics plates (CFRP). A non-linear finite element (FE) analysis is proposed in order to complete the experimental analysis of the flexural behaviour of the beams. This paper is a part of a complete program aiming to set up design formulate to predict the strength of CFRP strengthened beams, particularly when premature failure through plates-end shear or concrete cover delamination occurs. An elasto-plastic behaviour is assumed for reinforced concrete and interface elements are used to model the bond and slip.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.161-164
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• 2004

In these days, composite materials are applied to the military field like parts of air crafts, rockets, ammunitions and so on. As high pressure is loaded on the composite body, however, cracks or delamination phenomena can be occurred between layers of laminate. These cracks or delamination usually cause a deterioration of mechanical properties under the complicated loads. In this study, methods for improvement of the inter-laminar bonding strength of thick carbon/epoxy composite structures are suggested and discussed in terms of segment bending test.

• Structural Engineering and Mechanics
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• v.63 no.5
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• pp.597-605
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• 2017

Our work aims to analyze using the finite element method the evolution of the stress intensity factor (SIF) parameter K of three laminated folded plates stacks [$+{\alpha}$, $-{\alpha}$], made of the same epoxy matrix and different reinforcement fibers (boron, graphite and glass). Our results show that the angle of orientation of the boron/epoxy composite has no great influence on the variation of the parameter KI. Compared to composite graphite/epoxy and glass/epoxy, the laminated composite boron/epoxy reduces more the SIF KI in the middle of the plate for angles $0^{\circ}{\leq}{\alpha}{\leq}30^{\circ}$.

• Steel and Composite Structures
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• v.28 no.1
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• pp.25-37
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• 2018

For the first time, the parametric instability characteristics of tow-steered variable stiffness composite laminated (VSCL) cylindrical panels is investigated using B-spline finite strip method (FSM). The panel is considered containing geometrical defects including cutout and delamination. The material properties are assumed to vary along the panel axial length of any lamina according to a linear fiber-orientation variation. A uniformly distributed inplane longitudinal loading varies harmoni-cally with time is considered. The instability load frequency regions corresponding to the assumed in-plane parametric load-ing is derived using the Bolotin's first order approximation through an energy approach. In order to demonstrate the capabili-ties of the developed formulation in predicting stability behavior of the thin-walled VSCL structures, some representative results are obtained and compared with those in the literature wherever available. It is shown that the B-spline FSM is a proper tool for extracting the stability boundaries of perforated delaminated VSCL panels.