• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.76-79
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• 2000

Polymeric composites exhibit highly nonlinear and rate dependent behavior during loading and unloading in off-axis directions. The equilibrium state of stress during loading is lower than the state of stress produced at finite strain rates. The amount of stress relaxation during loading decreases. Interestingly, however, the stress goes up to reach to the equilibrium state of stress for a fixed displacement during unloading. The unloading behavior is quite similar to the loading behavior. The stress relaxation patterns during loading and unloading is also similar, and those depend on the fiber orientation angles and the loading and unloading rates. The AS4/PEEK thermoplastic composite is used to characterize the relaxation behavior for different off-axis angles and loading rates. There exists a transient loading region at the beginning of unloading. The effective stress and effective plastic strain concept is used to establish a master curve of stress recovery pattern for different off-axis angles and unloading rates.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.20-23
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• 2002

In this paper, various tow parameters such as equivalent tow thickness, amplitude of longitudinal tow and tow intervals were investigated and compared with each other by using microscopic observation to find out the exact deformation patterns between both directions of the fabric structure (Longitudinal and Transverse Directions). Specimens for the observation were taken from draped helmet which is made of fabric composite (Five Harness Satin Weave). From the observation results, it was found that there are different deformation pattern between tow directions and effect of geometric condition on the deformation of the fabric materials during draping process was verified.

• 대한기계학회논문집A
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• 제26권1호
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• pp.160-170
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• 2002

Many of aged and damaged concrete structure have been revitalized with composite reinforcement. Flexural behaviors of composite-patched concrete specimens are characterized by high-sensitivity moire interferometry. The three-mirror, four-beam interferometry system and a compact loading system are used for obtaining singe patterns representing whole-field contour maps of in-plane displacements. It is seen from the calibration test for the loading system that the measured bending displacement is in excellent agreement with the displacement calculated by the beam theory. The crack opening displacement as well as the bending and the horizontal displacement fur the notched and unnotched specimen are investigated. The results also show that the notched specimen reinforced by a composite sheet has sufficient stiffness and strength compared to the original concrete specimen.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 추계 학술논문 발표대회
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• pp.87-88
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• 2018

In this study, the tensile properties of single and hybrid fiber reinforced cement composite according to strain rate was evaluated. Experimental results, in the strain rate 10^-6/s, fiber reinforced cement composite showed improved of tensile strength and decrease of strain at peak stress as SSF volume content increased. In the strain rate 101/s, the single and hybrid reinforced cement composite's tensile properties are improved, because of the improved bond strength between the fiber and matrix. And hybrid fiber reinforced cement composite showed high energy absorption capacity, because the SSF prevented the cracking and fracture of the surrounding matrix when during the HSF pull-out.

• Steel and Composite Structures
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• 제32권6호
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• pp.821-832
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• 2019

An analysis on thermal buckling and postbuckling of composite laminated plates reinforced with a low amount of graphene platelets is performed in the current investigation. It is assumed that graphaene platelets are randomly oriented and uniformly dispersed in each layer of the composite media. Elastic properties of the nanocomposite media are obtained by means of the modified Halpin-Tsai approach which takes into account the size effects of the graphene reinforcements. By means of the von $K{\acute{a}}rm{\acute{a}}n$ type of geometrical nonlinearity, third order shear deformation theory and nonuniform rational B-spline (NURBS) based isogeometric finite element method, the governing equations for the thermal postbuckling of nanocomposite plates in rectangular shape are established. These equations are solved by means of a direct displacement control strategy. Numerical examples are given to study the effects of boundary conditions, weight fraction of graphene platelets and distribution pattern of graphene platelets. It is shown that, with introduction of a small amount of graphene platelets into the matrix of the composite media, the critical buckling temperature of the plate may be enhanced and thermal postbuckling deflection may be alleviated.

• Restorative Dentistry and Endodontics
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• 제14권1호
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• pp.179-188
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• 1989

The purpose of this study was to measure Micro vicker's hardness of 4 kinds of anterior Composite resins (Pyrofil light bond anterior, Lite-fil anterior, Photo clear fil anterior, Silux) and 6 kinds of posterior Composite resin (Pyrofil light bond posterior. Lite-fil posterior, Photo clear fil posterior, Occlusin posterior, Palfique light posterior, P-30, posterior) according to deference of depth and distance of light tip from surface of composite resin. Each composite resin was filled into Teflon tube of 5mm in diameter and 5mm in depth, celluloid matrix was covered and the light in accordance with each composite resin was irradiated in distance of zero millimeter and 1 cm from light tip to surface of composite resin for 30 seconds. Specimens were sectioned longitudinally with cutting device. Microvicker's hardness measurements ware made at the depth of surface, 1mm, 2mm, 3mm, 4mm and 5mm from the surface to deep portion. Vicker's hardness numbers were taken on each depth under 200gm load for 30 seconds with MVK-E. The following results were: 1. The highest hardness value was measured at 1 mm depth. Then the deeper the depth, the lesser the hardness was observed. 2. The hardness value of anterior composite resins is lower than one of posterior composite resins. 3. Hardness number of composite resin irradiated in distance of zero millimeter from surface of composite resin was higher than one of 1 cm from surface of composite resin. 4. The pattern of hardness change at varying depth was similar to all the experimental material with no relation to distance of light from specimen.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.42-45
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• 2001

The characteristics of smart skin for wireless LAN system under compression load are investigated. The smart skin structure is composed of 3 layers of face material and 2 layers of core material. Theoretical formula for determining buckling load is derived by Rayleigh-Ritz method and compared with experimental result. The maximum length of specimen that buckling does not occur is determined by only face material. In the experiment, if load supporting capability and the antenna property such as radiation pattern and reflection coefficient were examined.

• Journal of information and communication convergence engineering
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• 제8권1호
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• pp.13-18
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• 2010

The composite stock cutting problem is defined as allocating rectangular and irregular patterns onto a large composite stock sheet of finite dimensions in such a way that the resulting scrap will be minimized. In this paper, we introduce a novel approach to hybrid optimization algorithm called MGA in MPI (Message Passing Interface) environments. The proposed MGA combines the benefit of rapid convergence property of Mean Field Annealing and the effective genetic operations. This paper also proposes the efficient data structures for pattern related information.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.79-82
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• 2003

In case of performing resin transfer molding (RTM), race track effects and non-uniform fiber volume fraction may cause undesirable resin flow pattern and thus result in dry spots, which affect the mechanical properties of the finished parts. In this study, a real time RTM control strategy to reduce these unfavorable effects is proposed. Through numerical simulations and experiments, the validity of the proposed scheme is demonstrated.

• 실천공학교육논문지
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• 제14권2호
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• pp.351-359
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• 2022

본 논문에서는 학습자들의 효율적인 학습을 돕는 온라인 학습 도구 애플리케이션을 웹사이트로 제공하고자 한다. 인출, 체계화, 메타인지, 이 세 가지 측면에서 학습자들의 학습 효율을 어떻게 향상시킬 수 있는지에 대해 논의하고자 하며, 본 웹 서비스를 통해 학습자는 플래시 카드 기반의 인출 학습법으로 학습을 진행할 수 있다. 이때, 합성 패턴(Composite Pattern)을 사용하여 플래시 카드를 Directory-File System과 유사한 형태로 관리하는 방법에 대해 서술한다. 학습자는 플래시 카드를 마인드맵으로 변환하여 지식을 체계적으로 정리할 수 있다. 학습자의 학습진행도에 따라 마인드맵의 색상이 달라지며, 학습자는 자신이 무엇을 알고 무엇을 모르는 지 색상을 통해 쉽게 인지할 수 있다. 이때, 학습진행도를 판단하고 예측하는 알고리즘의 정확도를 향상시키기 위한 딥 러닝 모델 구축을 제안한다.