• Advances in materials Research
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• 제12권1호
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• pp.1-13
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• 2023

The combination of cobalt ferrite and natural rubber has a potential to enhance the functional properties of rubber ferrite composites available on the market. In this study, cobalt ferrite was synthesized by the sol-gel method with tapioca starch as a cheating agent and then incorporated into natural rubber using an internal mixer. The curing characteristics, magnetic hysteresis, complex permeability, and permittivity of the rubber ferrite composites were studied as a function of the loading from 0 to 25 phr. The cure time and scorch time tended to reduce with the addition of non-reinforced cobalt ferrite fillers. The remanent and saturation magnetizations were linearly proportional to the cobalt ferrite loading, consistent with the rule of mixture. On the other hand, the increase in cobalt ferrite loading from 5 to 25 phr slightly affected the coercive field and the complex permeability. Using the maximum loading of 25 phr, both real and imaginary parts of the permittivity were significantly raised and reduced with the frequency in the 10-300 MHz range.

• Elastomers and Composites
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• 제57권4호
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• pp.175-180
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• 2022

To produce a co-poly-para-aramid fiber (AF, Technora^®)-reinforced neoprene rubber composite, dispersion of AF in a neoprene matrix is investigated. The AF is then surface-modified by mercerization and acetone, plasma, and silane treatments to improve dispersibility. Finally, an internal mixer process is used to disperse the surface-modified fibers in the neoprene rubber matrix.

• Earthquakes and Structures
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• 제23권4호
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• pp.329-338
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• 2022

This work addresses the optimization controller design problem combining the AI evolution bat (EB) optimization algorithm with a fuzzy controller in the practical application of a reinforced concrete frame structure. This article explores the use of an intelligent EB strategy to reduce the dynamic response of Lead Rubber Bearing (LRB) composite reinforced concrete frame structures. Recently developed control units for plant structures, such as hybrid systems and semi-active systems, have inherently non-linear properties. Therefore, it is necessary to develop non-linear control methods. Based on the relaxation method, the nonlinear structural system can be stabilized by properly adjusting the parameters. Therefore, the behavior of a closed-loop system can be accurately predicted by determining the behavior of a closed-loop system. The performance and durability of the proposed control method are demonstrated by numerical simulations. The simulation results show that the proposed method is a viable and feasible control strategy for seismically tuned composite reinforced concrete frame structures.

• 폴리머
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• 제25권1호
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• pp.122-132
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• 2001

본 연구에서는 온도의 상승에 의하여 팽창하는 열팽창 기능을 가지고 있으면서 부피의 감소에 의하여 발생하는 압력의 손실을 상쇄시킬 수 있는 고무 치공구를 열가소성 고분자의 필름 함침공정에 적용하였다. 일반적인 압축성형공정에서는 온도의 상승에 의하여 수지가 용융되고 이에 수지가 함침됨에 따라 압력이 감소하지만, 고무 치공구를 사용한 경우에는 수지의 함침을 보상한 고무 치공구가 팽창하여 감소된 압력을 보상하기 때문에 급격한 압력의 강하를 억제할 수 있었다. 이렇게 수지의 함침에 따른 고무 치공구의 부피 팽창 그리고 이에 따른 수지 함침속도의 변화를 고려하여 고무 치공구를 이용한 필름 함침공정 모델을 제안하였다. 또한 고무 치공구를 사용하지 않는 일반적인 압축공정에 있어서 수지의 함침에 따른 섬유층 탄성력의 변화를 실험적으로 측정하여 단계적인 압축공정에 있어서 수지의 함침속도를 예측할 수 있는 모델을 제안하였다.

• Elastomers and Composites
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• 제42권3호
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• pp.168-176
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• 2007

카본블랙이나 실리카 등으로 보강된 고무 가황체는 순수한 초기상태에서 하중(부하)를 가하고 제거하는 반복과정에서 응력은 점점 연화되어 초기상태에서 얻어진 응력보다 작게 나타난다. 이러한 응력 연화 현상을 Mullins 효과라고 부른다. 이러한 응력 연화 거동을 이론적으로 표현하기 위하여 Ogden-Roxburgh 등이 손상 파라미터를 이용하여 제안한 pseudo-elastic 개념을 적용하여 보강제가 함유된 고무 가황체의 변형률 에너지 함수를 구하였다. 카본블랙으로 보강된 NR 가황체를 이용하여 준정적 반복 부하 시험을 실시하였으며, pseudo-elastic 모델에서의 손상 파라미터가 제하 및 재 부하 시 응력-변형률 곡선에 어떠한 영향을 주는가와 더불어 손상 파라미터의 두 가지 변수인 r과 m의 물리적 의미를 파악하였다. 또한 보강제 함량을 달리하여 제작한 고무 가황체의 응력연화 변형률 에너지 함수를 결정하고 비교하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.350.2-350
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• 2002

The purpose of this study was to present the possible use of a new standard impactor, the rubber ball (so-called, impact ball), and to assess its evaluation method as fur heavy-weight impact in multi-story residential buildings. Several experiments were carried out to investigate the effect of the impactor on noise propagation in reinforced concrete buildings. Then, the noise from the impact ball was psychoacoustically evaluated. (omitted)

• Elastomers and Composites
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• 제53권2호
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• pp.57-66
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• 2018

Styrene-butadiene rubber (SBR), reinforced with different contents of silica (with or without modification using silane coupling agents), was prepared by a modified sol-gel method involving hydrolyzation of tetraethoxysilane over an acid catalyst. The structures of the as-prepared samples were characterized using various techniques, such as scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The mechanical properties of the as-prepared samples were discussed in detail. The results revealed an increasing of the storage modulus (G') with increase in the silica content without modification. In contrast, G' decreased after modification using silane coupling agents, indicating a reduction in the silica-silica interaction and improved dispersion of silica in the SBR matrix. Both tensile stress and hardness increased with increase in the silica content (with modification) in the SBR matrix, albeit with low values compared to the samples with un-modified silica, except for the case of silica modified using (3-glycidyloxypropyl) trimethoxysilane (GPTS). The latter observation can be attributed to the special structure of GPTS and the effort of oxygen atom lone-pair.

• Composites Research
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• 제17권3호
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• pp.45-50
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• 2004

계면상 조건과 섬유 함유량 변화에 따른 단섬유 강화 CR의 동적특성에 대해 주파수, 진폭 그리고 온도를 함수로 실험적 고찰을 하였다. 진폭 변형률 증가에 따라 LF는 1.33% 이상에서 약간 증가하였고, DR은 크게 감소하였다. 주파수 증가에 따라 LF는 특히 50Hz 이후 크게 감소하였고, DR은 기지고무보다 낮은 값을 보였다. 온도 증가에 따라 LF는 $65^{\circ}$에서 최대 값을 나타내고 이후 크게 감소세를 보였다. DR은 온도가 증가에 따라 기지고무 보다 낮은 값을 보였다. 일반적으로 동일한 시험 조건에서 계면상이 우수할수록 LF와 DR이 낮은 값을 보였다. 따라서 단섬유 강화고무는 진동 수비가 $\sqrt{2}$ 이하보다는 $\sqrt{2}$ 이상에서 더 큰 진동절연 효과가 있다고 할 수 있다.

• Structural Engineering and Mechanics
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• 제87권5호
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• pp.405-418
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• 2023

This study focused on the effectiveness of seismic isolation technique in case of a reinforced concrete structure with soft story defined as the stiffness irregularity between adjacent stories. In this context, a seismically isolated 3-story reinforced concrete structure was analyzed by gradually increasing the first story height (3.0, 4.5, and 6.0 m). The seismic isolation system of the structure is assumed to be composed of lead rubber bearings (LRB). In the analyses, isolators were modeled by both deteriorating (temperature-dependent analyses) and non-deteriorating (bounding analyses) hysteretic representations. The deterioration in strength of isolator is due to temperature rise in the lead core during cyclic motion. The ground motion pairs used in bi-directional nonlinear dynamic analyses were selected and scaled according to codified procedures. In the analyses, different isolation periods (Tiso) and characteristic strength to weight ratios (Q/W) were considered in order to determine the sensitivity of structural response to the isolator properties. Response quantities under consideration are floor accelerations, and interstory drift ratios. Analyses results are compared for both hysteretic representations of LRBs. Results are also used to assess the significance of the ratio between the horizontal stiffnesses of soft story and isolation system. It is revealed that seismic isolation is a viable method to reduce structural damage in structures with soft story.

• Elastomers and Composites
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• 제53권3호
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• pp.109-123
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• 2018

The effect of the silica content on the state and properties of silica-filled styrene-butadiene rubber/butadiene rubber (SBR/BR) compounds containing coupling and dispersion agents was evaluated by varying the content of silica from 50 to 120 phr. Bis-[(triethoxysilyl)propyl] tetrasulfide (TESPT) and zinc 2-ethylhexanoate (ZEH) were used as the coupling and dispersion agents, respectively. The maximum silica content in the pristine material was 80 phr, which increased to 120 phr upon the addition of TESPT and ZEH. The incorporation of TESPT considerably improved most of the rubber properties due to its coupling action and the suppression of silica flocculation, while further addition of ZEH resulted in additional improvements. The properties of the rubber compounds with different silica contents can be fully explained either by an enhancement of the rubber-silica interactions or by their deterioration due to an excessive amount of silica aggregates.