• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.169-172
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• 2003

Time dependent deflections of double composite box girders are investigated based on the on going laboratory experiments scheduled for 3months long. Two of 2-span double composite box girders with 2.5m each span length are cast and time dependent behaviors are measured using 30 strain gages and 2 LVDTs after 5 days' curing. The measured experimental results are compared with the numerical predictions performed based on the one dimensional finite element method adopting beam element. The FEM formulation adopts the time dependent concrete constitutive model which is derived in an incremental format by expanding the total form of stress-strain relation by the first order Taylor series with respect to the reference time. A good agreement between the measured and predicted results are observed and the effects of the bottom concrete placed at the negative moment region of the bridge girder are discussed.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.180-183
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• 2003

In this work. a potential inexpensive epoxy resin. epoxidized soybean oil (ESO) was synthesized and applied as a toughening agent for 4.4'-tetradiglycidyl diaminodiphenyl methane (TGDDM). The chemical structure of ESO was characterized by FT-IR, $^1H NMR, and ^{13}C NMR$ spectroscopy. The curing behaviors. thermal stabilities. fracture toughness. and flexural strength of TGDDM/ESO blend systems were investigated by using the dynamic DSC. thermogravimetric analysis (TGA). and flexural tests. The thermal stabilities of TGDDM/ESO blend systems were decreased with increasing ESO contents. whereas the critical stress intensity factor ($K_{IC}$) and flexural strength ($\sigma_f$) were increased with ESO contents up to 10 wt% ESO.

• 한국인쇄학회지
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• 제18권2호
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• pp.113-124
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• 2000

It is well known that the characteristics of liquid crystal polymer composite(LCPC) films are possessed of large-area and flexible display, polarizer free, high contrast, wide angle of visual filed and high responsiveness. In this study, we have investigated to the best optimal mixing rates chiral nematic liquid crystals and UV-curable resins having different properties acrylate moleculars. The purpose of this study has been the development of new functional application with liquid crystal polymer composite films. For example the films were applied a new thermal sensor. In results, best phase separation behaviors turned out liquid crystal/monomer/oilgomer mixture system.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.127-128
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• 2005

UV-curable pressure sensitive adhesives were prepared by blending acrylic copolymer, copolymerized with butyl acrylate (BA), acrylic acid (AA) and vinyl acetate (VAc) by solution polymerization, triethyl amine (TEA) and trimethylolpropane triacrylate (TMPTA). The PSAs were evaluated by peel strength with varying contents of TMPTA and UV dose, and also glass transition temperature($T_g$) of PSAs were measured. When exposed on UV irradiation, the PSAs showed the decreased peel strength and increased $T_g$. And following UV irradiation, the PSAs did not leave any residue on wafer after peel off PSA.

• 한국구조물진단유지관리공학회 논문집
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• 제23권6호
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• pp.9-17
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• 2019

콘크리트의 수화물 및 이와 관련된 특성치들은 재령에 따라 변화하며 이는 염화물 확산성과 큰 관련이 있다. 본 연구에서는 세 가지 수준의 물-결합재 비와 플라이 애시 및 고로슬래그 미분말을 30% 혼입한 콘크리트 대하여 2년간 장기 양생을 수행하였다. 5번의 측정 시점(28일, 56일, 180일, 365일, 730일)에 대하여 촉진실험을 통하여 촉진 염화물 확산계수를 평가하였으며, DUCOM을 통하여 도출된 공극률, 염화물 구속능, 투수계수의 변화와 비교하였다. 염화물 확산성과 투수성의 변화 패턴이 가장 유사하였는데, 이는 투수성이 공극률의 제곱에 비례하기 때문이다. 또한, 각 재령 기간 동안 변화하는 비율을 분석하였는데, 초기 재령(재령 28일~56일)에서 공극률, 투수성 및 염화물 확산성의 변화가 지배적이었고, 낮은 물-결합재 비를 가진 OPC 콘크리트에서는 180일까지 확산성의 변화가 지속적으로 크게 평가되었다.

• 한국염색가공학회지
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• 제29권1호
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• pp.37-44
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• 2017

An issue of major concern in the utilization of laminated composites based epoxy resin is associated with the occurrence of delaminations or interlaminar cracks, which may be related to manufacturing defects or are induced in service by low-velocity impacts. A strong interfacial filament/brittle epoxy resin bonding can, however, be combined with the high fracture toughness of weak interfacial bonding, when the filaments are arranged to have alternate sections of shear stress. To improve this drawback of the epoxy resin, UV-thermal dual curable resin were developed. This paper presents UV-thermal dual curable resin which were prepared using epoxy acrylate oligomer, photoinitiators, a thermal-curing agent and thermoset epoxy resin. The UV curing behaviors and characteristics of UV-thermal dual curable epoxy resin were investigated using Photo-DSC, DMA and FTIR-ATR spectroscopy. The mechanical properties of UV-thermal dual curable epoxy resin impregnated CF prepreg by UV curable resin content were measured with Tensile, Flextural, ILSS and Sharpy impact test. The obtained results showed that UV curable resin content improves the epoxy toughness.

• 한국도로학회논문집
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• 제17권6호
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• pp.47-54
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• 2015

PURPOSES : The objective of this study is to evaluate the early adhesive characteristic of asphalt emulsions, including polymer-modified emulsions, for chip seals using the surface energy concept, the bitumen bond strength (BBS) test, and the Vialit test. METHODS : Two general methods, the BBS test and Vialit test, were applied to investigate the bond strength and the aggregate loss, respectively. A new theory, the surface free energy (SFE) theory, was used to evaluate the adhesive characteristic between the emulsion and the aggregate. Based on the theory, the contact angles were measured, and then the surface energy components were calculated. Using those components, the work of adhesion (Wa) was calculated for each emulsion. To ensure reliable results, all the tests were performed under the same conditions, i.e., at $25^{\circ}C$ for 240 minutes of curing time. For the materials, three emulsions (CRS-2, CRS-2L, and CRS-2P) and one aggregate type (granite) were employed. RESULTS AND CONCLUSIONS : Under the same conditions, the modified emulsions showed better adhesive characteristics and curing behaviors than the unmodified emulsions. In addition, there was no significant difference between the various modified emulsions. One of the important findings is that the analysis by Wa presents more sensitive results than other methods. The results of the Wa showed that the CRS-2P emulsion has the best adhesive characteristics. Consequently, the use of modified emulsions for chip seals could prevent aggregate loss and allow open traffic earlier.

• Geomechanics and Engineering
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• 제28권3호
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• pp.255-263
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• 2022

Lime stabilization has conventionally been listed amid the key techniques of chemical stabilization. Replacing lime with sustainable agro-based by-products have gained prominence in recent decades. Bagasse ash (BA) is one such potential alternatives, an industrial waste with abundance in production, and industries exploring sustainable solutions for its safe disposal. Supplementing BA with lime could be an ideal approach to reduce lime consumption. However, suitability of BA and lime for the stabilization of expansive clays, such as black cotton (BC) soil is yet to be explored. This paper therefore aims to investigate the suitability of BA-lime mixtures to stabilize BC soil with emphasis to compaction behaviors and unconfined compressive strength (UCS) using standard laboratory procedures. Suitability of BA-lime mixture is then assessed against addition of calcium sulphate which, from previous experience, is detrimental with lime stabilization. Experimental outcomes nominate 15% BA as the optimum value observed from both compaction and UCS data, while addition of 4% lime to 15% BA showed the best results. Mineralogical and microstructural analysis show the presence of cementitious compounds with addition of lime and calcium sulphate with curing periods. While, formation of Ettringite needles were noted with the addition of calcium sulphate in BA-lime mixtures (at optimum values) after 90-day curing, and UCS results showed a decrease at this point. To this end, addition of BA in lime stabilization showed encouraging results as assessed from the compaction and UCS results. Nonetheless usage of calcium salts, with utmost emphasis on calcium sulphate and equivalent should be avoided.

• 한국지반공학회논문집
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• 제22권11호
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• pp.25-35
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• 2006

본 연구에서는 폐어망을 이용한 보강 경량토의 역학적 특성을 고찰하였다. 본 실험에서 사용된 보강 경량토는 부산 신항 건설현장에서 채취한 준설토와 시멘트, 기포 및 폐어망으로 구성되어졌다. 다양한 함유율의 폐어망이 혼합된 보강 경량토의 보강효과를 고찰하고, 무보강 경량토와 보강 경량토의 거동 특성을 비교하기 위하여 다양한 실내실험이 수행되어졌다. 보강 경량토에 대한 실험결과 응력-변형 관계와 일축압축강도는 폐어망에 의해 큰 영향을 받는다는 것이 나타났다. 보강 경량토의 압축강도는 양생기간이 증가할수록 증가하며, 폐어망을 첨가함으로써 일반적으로 증가하지만, 압축강도 증가량은 폐어망 함유율에 비례하지는 않는다. 본 실험의 경우 폐어망 함유율이 0.25%일 때 최대 압축강도가 발현되는 것을 알 수 있었다. 한편, 보강 경량토의 함수비 변화는 양생기간 7일까지 급격하게 감소한 후 일정한 값에 수렴하였다.

• 접착 및 계면
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• 제10권4호
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• pp.191-198
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• 2009

지방족 에폭시 수지인 glycerol diglycidyl ether (GDE)에 단관능성 아크릴 수지인 2-carboxyethyl acrylate (2-CEA) 또는 2-hydroxyethyl acrylate (2-HEA)를 반응시켜 지방족 에폭시 아크릴레이트를 제조하였다. FT-IR, $^1H$-NMR, 그리고 $^{13}C$-NMR를 사용하여 생성물을 확인하였고, 수율은 prep-LC를 사용하여 얻었다. 생성물의 자외선 경화거동은 photo-DSC를 사용하였고, 열경화 반응성은 DSC를 사용하여 얻었다. 2-CEA의 반응성이 2-HEA보다 월등히 높음을 알 수 있었고, 2-CEA로부터 제조한 지방족 에폭시 아크릴레이트(GEA-C)의 수율은 약 83%이었다. 촉매를 제거한 GEA-C 생성물의 자외선 경화반응($T_{max}$)은 약 10 s로 빠르게 진행되었다. GEA-C는 투명하고, 내열성이 우수하며 저점도를 갖고 있음을 확인할 수 있었다. ${\Delta}E^*$는 2.51, 점도는 192 cps, 5% 중량감소 때의 온도는 $299^{\circ}C$이었다. Kissinger와 Ozawa-Flynn-Wall 식으로 얻은 GEA-C의 열경화 반응의 활성화에너지($E_a$)는 91~92 kJ/mol이었다.