• Advances in nano research
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• 제9권4호
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• pp.295-307
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• 2020

The vibrational characteristics of Multi-Phase Nanocomposite (MPC) reinforced annular/circular plate under initially stresses are presented using the state-space formulation based on three-dimensional elasticity theory (3D-elasticity theory) and Differential Quadrature Method (DQM). The MPC reinforced annular/circular plate is under initial lateral stress and composed of multilayers with Carbon Nanotubes (CNTs) uniformly dispersed in each layer, but its properties change layer-by-layer along the thickness direction. The State-Space based Differential Quadrature Method (SS-DQM) is presented to examine the frequency behavior of the current structure. Halpin-Tsai equations and fiber micromechanics are used in the hierarchy to predict the bulk material properties of the multi-scale composite. A singular point is investigated for modeling the circular plate. The CNTs are supposed to be randomly oriented and uniformly distributed through the matrix of epoxy resin. Afterward, a parametric study is done to present the effects of various types of sandwich circular/annular plates on frequency characteristics of the MPC reinforced annular/circular plate using 3D-elasticity theory.

• Parasites, Hosts and Diseases
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• 제37권1호
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• pp.39-46
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• 1999

As a preliminary study for the explanation of pathobiology of Neodiplostomum seoulense infection. a 54 kDa protease was purified from the crude extract of adult worms by sequential chromatographic methods. The crude extract was subjected to DEAE-Sepharose Fast Flow column, and protein was eluted using 25 mM Tris-HC1 (pH 7.4) containing 0.05. 0.1, 0.2 and 0.4 M NaC1 in stepwise elution. The 0.2 M NaCl fraction was further purified by Q-Sepharose chromatography and protein was eluted using 20 mM sodium acetate (pH 6.4) containing 0.05, 0.1. 0.2 and 0.3 M NaCl, respectively. The 0.1M NaCl fraction showed a single protein band on SDS-PAGE carried out on a 7.5-15% gradient gel. The proteolytic activities of the purified enzyme were specifically inhibited by L-trans-epoxy-succinylleucylamide (4-guanidino) butane (E-64) and iodoacetic acid. The enzyme, cysteine protease. showed the maximum proteolytic activity at pH 6.0 in 0.1 M buffer, and degraded extracellular matrix proteins such as collagen and fibronectin with different activities. It is suggested that the cysteine protease may playa role in the nutrient uptake of N. seoulense from the host intestine.

• Advances in Automotive Engineering
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• 제1권1호
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• pp.41-59
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• 2018

In the study, investigation of fiber- reinforced composite materials that can be an alternative to conventional steel was performed by finite element analysis with the help of software. Steel and composite materials have been studied on a four axle truck chassis model. Three-dimensional finite element model was created with software, and then analyzes were performed. The analyses were performed for static and dynamic/fatigue cases. Fatigue cases are formed with the help of design spectra model and fatigue analyses were performed as static analyses with this design spectra. First, analyses were performed for steel and after that optimization analyses were made for the AS4-PEEK carbon fiber composite and Eglass-Epoxy fiber composite materials. Optimization of composite material analyzes include determining the total laminate thickness, thickness of each ply, orientation of each ply and ply stacking sequence. Analyzes were made according to macro mechanical properties of composite, micromechanics case has not been considered. Improvements in weight reduction up to %50 provided at the end of the composite optimization analyzes with satisfying stiffness performance of chassis. Fatigue strength of the composite structure depends on various factors such as, fiber orientation, ply thickness, ply stack sequence, fiber ductility, ductility of the matrix, loading angle. Therefore, the accuracy of theoretical calculations and analyzes should be correlated by testing.

• Composites Research
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• 제12권1호
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• pp.28-36
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• 1999

본 연구에서는 얇은 탄소섬유/에폭시 복합적층판(두께 1mm)의 냉각열응력으로 인한 자유경계단 근처의 파손을 유한요소 수치해석과 초음파 C-scan, 광학 및 전자현미경 관찰을 통하여 검토하였다. 수치해석 결과, 복합적층판의 자유단 근처의 내부층에서 층냄 및 층간응력이 크게 나타났다. 액체질소에 의한 저온담금질 실험결과, 적층강도가 $[0_2/90_2]_s,\;[45_2/-45_0]_s,\;[0_2/60_2]_s$인 적층판의 층간근처의 내부층 쪽에서만 모재 및 계면부에서 진전하는 층내균열이 발생하였다. 이들 결과는 위의 수치해석 결과와 일치했다.

• Tribology and Lubricants
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• 제18권1호
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• pp.61-67
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• 2002

The objective of the present study was to investigate the characteristics of the friction and wear according to the amount of ion-irradiation for the carbon fiber reinforced plastic (CFRP). Unidirectional carbon fiber reinforced composites were fabricated with epoxy resin as a matrix and carbon fiber as a reinforcement, and its surface was modified by the ion-assisted reaction. When the amount of ion-irradiation was $1{\times}10^{16}$ $ions/cm^{2}$. the friction coefficients of composites were about 0.1 and the wear mode was stable. whereas, the friction coefficient of non-treatment composites were about 0.16 and the wear mode was very unstable. But if the amount of ion-irradiation was $5{\times}10^{16}$ $ions/cm^{2}$, the friction coefficients were higher rather than that of $1{\times}10^{16}$ $ions/cm^{2}$ Consequently. the amount of ion-irradiation was not in proportion to the friction coefficients, and it was conformed that the optimal conditions would exist between both of them.

• 폴리머
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• 제24권5호
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• pp.690-700
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• 2000

본 연구에서는 온도의 상승에 의하여 부피가 팽창하는 열팽창 고무 치공구의 팽창 특성을 이용하여 열경화성 복합재료를 경화하고 압축하는 과정을 실험과 모델링을 통하여 해석하였다. 열팽창 고무치공구가 사용되는 닫힌계 (fixed-volume process)와 열린계 (variable-volume process)에서 예상되는 압력을 이론적으로 유도하였고, 경화가 수반되는 과정에 있어서는 실험을 통하여 열팽창 치공구와 프리프레그가 나타내는 압력을 측정하였다. 온도가 상승하고 경화가 수반되는 경우에 등속도 압축실험에 의하여 얻어진 응력-변형율 곡선은 비선형 점탄성 특성을 보여주었는데, 본 연구에서는 Maxwell모델을 KWW (Kohlrausch-Williame-Watts)식으로 변형시킨 모델식을 이용하여 이를 매우 정확하게 표현할 수 있었다. 이 모델을 이용하여 몰드의 부피를 고정시킨 상태에서 경화시키는 닫힌계 공정에서 예상되는 압력을 예측하였으며 따라서 열팽창 치공구를 열경화성 복합재료의 경화압축 공정에 성공적으로 적용하였고 이를 해석하였다.

• Elastomers and Composites
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• 제51권1호
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• pp.24-30
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• 2016

Sole in the footwear usually modified with foaming agent on the polymer resin to improve the lightweightness and crush-cushion effect. In this study, we investigated rheological properties for polymer resin filled with the different type and concentration of foaming agent, capsule type foaming agent and organo-chemical foaming agent, under the time sweep test. Curing times of each polymer resin with different kind of foaming agent are delayed than reference material (epoxy resin with curing agent). In case of adding capsule type foaming agent, however, there is appropriate concentration to reduce the curing time, relatively. When foaming agent is activated, foaming force inflates the sample in contrast to condensation force of curing and then axial normal force develop to the (+) direction. Interestingly, by increase concentration of foaming agent, there is a specific point to break down the axial normal force development. The reason for this phenomenon is that coalescence of foams induce the blocking of axial normal force development.

• 한국세라믹학회지
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• 제43권10호
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• pp.607-612
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• 2006

In VARTM (Vacuum Assisted Resin Transfer Molding) process, the permeability generally controls the filling time of the resin and it also affects the void characteristics of the fiber composite. In this study, carbon and glass fiber inter-layered hybrid composites (carbon fiber centered stack) with an epoxy matrix were fabricated by VARTM process and evaluated the resin flow and macro void characteristics. The permeability of glass fiber was higher than that of carbon fiber used in this study. Using Darcy's equation, the permeability of hybrid composites could be predicted and experimentally confirmed. After curing, the macro void content of hybrid composites was investigated using image analyzer. The calculated filling time was well agreed with experimental result and the void content was significantly changed in hybrid composites.

• Advanced Composite Materials
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• 제17권4호
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• pp.373-407
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• 2008

This paper will examine the possibilities of the virtual tests of composite structures by simulating mechanical behaviors by using supercomputing technologies, which have now become easily available and powerful but relatively inexpensive. We will describe mainly the applications of large-scale finite element analysis using the direct numerical simulation (DNS), which describes composite material properties considering individual constituent properties. DNS approach is based on the full microscopic concepts, which can provide detailed information about the local interaction between the constituents and micro-failure mechanisms by separate modeling of each constituent. Various composite materials such as metal matrix composites (MMCs), active fiber composites (AFCs), boron/epoxy cross-ply laminates and 3-D orthogonal woven composites are selected as verification examples of DNS. The effective elastic moduli and impact structural characteristics of the composites are determined using the DNS models. These DNS models can also give the global and local information about deformations and influences of high local in-plane and interlaminar stresses induced by transverse impact loading at a microscopic level inside the materials. Furthermore, the multi-scale models based on DNS concepts considering microscopic and macroscopic structures simultaneously are also developed and a numerical low-velocity impact simulation is performed using these multi-scale DNS models. Through these various applications of DNS models, it can be shown that the DNS approach can provide insights of various structural behaviors of composite structures.

• 한국해양바이오학회지
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• 제6권2호
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• pp.41-46
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• 2014

Mussel byssus is a bundle of threads used to attach mussels to wet substrates. Recently, a thin cuticle layer on the byssus has attracted public attentions due to its remarkable toughness - stiff as epoxy resin and extensible as rubber. Here, we observed ultrastructure of the cuticle layer in a far eastern mussel (Mytilus coruscus) to understand underlying mechanisms for the mechanical properties. The cuticle layer observed by TEM was composed of submicron-sized granular inclusions in a continuous matrix phase. In addition, ultrastructural study in the presence of tertiary amine (Tetraethylammonium, TEA) showed an evidence that the cuticle is stabilized by cation-${\pi}$ interaction.