• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.791-806
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• 2020

In this study, a block shear strength test was conducted to compare and analyze the strength and failure mode on the glued laminated timber, CLT, and Ply-lam CLT, which are mainly used for the construction of wood construction as engineering wood. Through this, the Ply-lam CLT manufacturing conditions for optimum production, such as the type of lamina, plywood, adhesive, and layer composition, were investigated. The results are as follow. Through block shear strength test, it showed high strength in the order of glued laminated timber, Ply-lam CLT and CLT. In particular, the shear strength of Ply-lam CLT, which is made of a composite structure of larch plywood and larch lamina, passed 7.1 N/㎟, which is a Korean industrial standards for block shear strength of structural glued laminated timber. In addition, in this study, there was no different in shear strength according to the adhesive type used for glulam, CLT, and Ply-lam CLT adhesion. However, in the case of Ply-lam CLT, the difference in shear strength of Ply-lam CLT was shown according to the type of lamina and plywood. The results showed high strength in the order of Larix kaempferi > Mixed light hardwood ≒ Pinus densiflora, sieb, et, Zucc plywood. The optimal configuration of Ply-lam CLT is when larch plywood and larch lamina are used, and it is decided that the adhesive can be used by selecting PRF and PUR according to the application. The results of block shear strength failure mode by type of wood based materials were analyzed. The failure mode showed shear parallel-to-grain for glulam, rolling shear for CLT, and shear parallel-to-grain and rolling for ply-lam CLT. This is closely related to shear strength results and is decided to indicate higher shear strength in Ply-lam CLT than in CLT due to rolling shear.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.729-732
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• 2010

본 논문에서는 이산 변수 최적화에 적합한 유전 알고리듬을 이용하여 복합재 적층 패치의 최적강도설계를 수행하였다. 기저판(substrate)와 접착제(adhesive), 그리고 복합재 적층 패치로 이루어진 구조물에서 패치의 강도를 효율적으로 구하기 위해서 응력 함수 기반의 해석적 방법을 도입하였다. 면외 방향의 응력 함수를 가정하여 가상 공액일의 법칙(complementary virtual work principle)에 적용하였으며, 복합재 패치의 자유 경계조건으로부터 면내 방향의 응력함수를 결정하였다. 응력 함수를 통하여 구한 층간 응력 값은 자유 경계 효과를 잘 나타내었고, 이를 이용하여 패치의 강도 해석을 수행하였다. 강도 해석 시, 복합재 패치의 파괴 기준은 면내 응력들에 대해서는 최대 응력 척도를 사용하였으며, 층간 응력들에 대해서는 quadratic delamination 척도를 사용하였다. 유전 알고리듬을 이용한 최적강도설계 과정에서는 임의의 염색체가 주어진 적층 구속 조건을 만족할 수 있게 수정(repairing)하는 과정을 도입하였다. 또한 다수의 전역해(global optima)를 효과적으로 찾기 위해서 multiple elitism 기법을 도입하였다. 응력 함수 기반의 강도 해석방법과 유전 알고리듬과의 연계를 통한 복합재 적층 패치의 강도최적설계 기법은 패치 구조물의 해석 및 설계에 있어서 효율적인 도구로서 사용할 수 있을 것이라 사료된다.

• Composites Research
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• v.33 no.5
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• pp.275-281
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• 2020

The mechanical property related to lap shear strength of the joint structure between carbon fiber reinforced polymer (CFRP) composite and metal (Ni-Cr Alloy) under varying environmental conditions (temperature and humidity) was studied in order to apply to the aircraft fan blade. Room temperature dry (RTD), elevated temperature wet (ETW), and cold temperature dry (CTD) environmental conditions were chosen for investigation based on the flight conditions of aircraft. Lap shear strength tests were conducted according to ASTM Standard D3528 to evaluate the shear strength. The microstructure characteristic of failure zone was analyzed by SEM images to check the adhesive shear strength with the three environmental conditions. In comparison with shear strength for the RTD condition, the shear strength in the ETW condition was reduced by 72.8% while those for the CTD condition increased by 56.5%. The moisture absorption and high temperature in ETW condition strongly had an affect on mechanical property of adhesive, while cold temperature could enhance the adhesive shear strength due to the higher brittleness.

• Analytical Science and Technology
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• v.18 no.6
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• pp.511-519
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• 2005

A method for determination of toluene diisocyanates (TDI) in toluene diisocynate (TDI)-based polyurethane (PUR) packing material was investigated, and also the migration of TDI to food was studied. TDI was extracted using food simulants such as n-haptane and 4% aqueous acetic acid. The determinations were performed using gas chromatography/mass spectrometry (GC/MS). One of major components for polyurethane, toluene diisocyanates, were detected in ten samples among twenty six food contact materials with the concentration range of $0.51{\sim}60.88{\mu}g/ml$. However the highest extracted amount was just 0.7% of $60.88{\mu}g/ml$ if the contact surface of food packing for extracting liquid was limited to the outer layer without exposure of the cutting edge of food packing multi-layers. The result of this study and the analysis method for TDI diisocyanate will be very useful for further study about food contact material, and the monitoring result could be used for evaluating the safety of food contact material before it is to be used for food, preservation.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.4
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• pp.445-452
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• 2010

Recently the effect of CPP-ACP on early caries remineralization and prevention has hashbeen extensively researched. However, there has been a lack of research on micro-shear bond strength of a sealant applied on a CPP-ACP treated surface. Therefore, the purpose of this study was to evaluate the effect of CPP-ACP on the micro-shear bond strength of a sealant bonded with 3 different bonding systems. From the sound human 3rd molars, the 150 specimens were prepared and randomly assigned to six groups. Group I: Immersion in artificial saliva for 2 weeks + 35% phosphoric acid Group II: Immersion in artificial saliva for 2 weeks + 35% phosphoric acid + dentin bonding agent Group III: Immersion in artificial saliva for 2 weeks + self-etching adhesive Group IV: CPP-ACP application for 2 weeks + 35% phosphoric acid Group V: CPP-ACP application for 2 weeks + 35% phosphoric acid + dentin bonding agent Group VI: CPP-ACP application for 2 weeks + self-etching adhesive Sealant was applied and the micro-shear bond strength was measured. From the result of this study, it can be assumed that the CPP-ACP pretreatment can weaken the bond strength of a sealant if the enamel surface is conditioned with self-etch adhesive.

• Composites Research
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• v.24 no.6
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• pp.56-63
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• 2011

The objective of this study is to investigate appropriate bonding methods of solar cells in order to apply solar cells, which have been receiving particular attention as a renewable energy due to fossil energy depletion and environment issues, to composite structures. Back-contact solar cells with approximately 24.2% energy conversion efficiency were used in this study. Since silicon-based solar cells are mechanically fragile, the secondary-bonding methods using adhesive were examined in this study. The experiment was conducted with three kinds of bonding materials such as EVA film, Resin film and elastic adhesive. The performance of solar cells for three types of adhesives under mechanical loading on test specimens is conducted. In addition, the measuring equipment was designed to evaluate the performance of the solar cells under mechanical loading in real time and the fracture characteristics depending on bonding materials were evaluated. The reason decreasing solar cells efficiency were analyzed and considered by Fractography. The results show that the solar cell performance is largely affected by bonding techniques. Moreover, the bonding method using elastic adhesive shows best solar cell efficiency.

• Journal of the Korean Wood Science and Technology
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• v.20 no.1
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• pp.46-50
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• 1992

본 연구는 잣나무 간벌재를 이용한 plywood gusset plate 접합과 toothed metal plate 접합에 대하여 인장력을 가해 조사하였다. plywood gusset plate 접합에 있어서는 합판과 부재 사이를 상온 경화제(초산 비닐 수지)로 접착한 후 6d 못으로 접합한 형태와 단지 합판만을 사용한 형태의 plywood gusset plate 접합 사이의 기계적 특성 차이를 조사했다. toothed metal plate 접합은 plywood gusset plate 접합보다 인장력에서 좋은 behavior를 보였다. 또한 접착제를 가한 plywood gusset plate 접합은 접합제를 가하지 않은 형태보다 큰 하중 지지력을 보였다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.259-260
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• 2000

알데히드류는 실내 가정의 건축물 단열재, 실내가구의 칠, 접착제, 하드보드, 악취 제거제, 제지 등 생활 용품에서 공업용품에 이르기까지 광범위하게 사용되며, 그 사용량도 증가되고 있다. 특히, formaldehyde는 urea-와 Phenol-formaldehyde 수지를 합성하는 주요 화합물질이다. 알데히드류 중 포름알데히드는 1ppm 또는 그 이하의 농도로 노출될 경우, 눈, 코, 목의 자극을 유발하고, 농도에 따라서 피부 알레르기, 두통, 메스꺼움, 흥부 압박감, 기관지염, 폐염 및 폐부종을 야기하며, 동물 실험결과, 미국 환경보호처에서는 인체 발암 가능성 물질로 분류하고 있다(US EPA, 1999). (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.439-440
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• 2000

알데히드류는 실내의 다양한 오염원에서 발생되어 하루의 대부분을 실내에서 보내고 있는 현대인들에게 건강상 영향을 미치는 것으로 알려져 관심의 대상이 되어왔으며, 특히, 포름알데히드는 발암성 물질로 알려진 대표적인 실내 환경 오염 물질이기도 하다(Zhang junfeng et al., 1999). 포름알데히드는 urea 또는 phenol-formaldehyde 수지를 합성하는 주요 물질이며, 건축물 단열재, 가구의 염료 및 광택제, 접착제, 합판, particle board, 악취 제거제, 제지, 가스 스토브, 담배연기, 화장용품, 세제등 생활 용품에서 공업용품에 이르기까지 광범위하게 사용되며, 그 사용량도 증가되고 있다(Thomas J. Kelly et al., 1999). (중략)

• Computational Structural Engineering
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• v.17 no.1
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• pp.39-42
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• 2004

콘크리트 구조물에 대한 보강공법은 1950년도에 개발된 강판보강공법을 위시로 하여 강연선에 의한 외부프리스트레싱 공법으로 발전하고 있으며, 약 10년전부터는 신소재인 FRP(Fiber Reinforced Polymer)에 의한 보강공법이 본격적으로 개발되어 실용화되고 있다. 강판보강공법은 에폭시 등의 접착제를 이용하여 콘크리트 인장측에 강판을 접착함으로써 강도 및 강성을 증가시키는 공법으로 강판을 보강재로 이용함으로써 공법에 대한 인지도가 높은 장점이 있는 반면, 재료의 가공 및 취급이 어려우며 중량이 커 자중이 증가되는 단점이 있다. 또한, 강재의 부식위험이 상존하고 있어 이에 대한 세심한 배려 및 주기적인 유지관리를 필요로 한다.(중략)