Britsh StandardBS 7991)에 명시된 DCB 시험편을 본 연구에 맞게 수정 후 두께 25mm, 35mm, 45mm, 55mm, 그리고 65mm의 DCB시험편을 제작하였다. 이 후 시험편을 Single-lap 방식으로 접착한 후 정적실험에서 도출된 최대 전단력을 각 시험편에 10Hz로 피로하중을 가하였다. 실험 결과값에 대한 수치해석적 검증을 하고자 상용 해석 프로그램인 ANSYS를 통해 실험과 동일한 시험편과 조건 하에 해석을 수행하였다. 접착력 해석을 하기 위해서 Mesh의 절점(node)들의 관계가 매우 중요하기 때문에 접착된 부분의 모든 절점들은 동일 선상에 있게 Mesh를 형성하였다. 실험 결과와 해석 결과를 비교해 본 결과 피로하중이 약 200cycle 반복되었을 때 최대 등가응력이 발생 하였고, 이때 전단방향으로 변위가 약 11mm 진전 된 것을 볼 수 있었다. 이후 4000cycle가량 피로하중이 반복 될 동안 변위는 일정하게 점점 증가한 후 피로하중이 약 4800cycle 반복 되었을 때 실험과 해석 데이터 모두 접착계면에서 완전한 전단 파괴가 일어난 것을 볼 수 있었다. 이때 변위는 약 20mm 진행 되었다. 해석을 통해 실험 데이터를 검증해 본 결과 두 결과 값은 완전 하게 같지는 않지만 유한요소법 해석 결과에 대한 신뢰를 확보 할 수 있었다. 이는 실제 구조물에 실험 없이 간단한 재료 물성치만으로도 해석을 통하여 구조적 안전성을 알아 볼 수 있는 한 방법이 될 수 있을 것이라고 사료된다.

Adhesive joint method has been used instead of welding, reveted joint, bolt and nut in various industry fields recently. Aluminum foam has hole or crack on adhesive interface which is different from common composite material. To investigate shear characteristic of adhesive interface between aluminum foams, double cantilever beams(DCB) with thicknesses of 25mm, 45mm and 65mm bonded with single-lab joints are designed. The relation between nodes at finite element model is important to investigate adhesive strength in this study. All meshes are generated and some nodes are located on adhesive zone along collinear axis. As reaction force obtained by static experiment is applied, fatigue analysis is carried with 10Hz. In advance, adhesive property is obtained by preliminary experiment for applying adhesive strength to input into simulation analysis. With these conditions, the analysis results show that 2.97MPa, 3.10MPa and 4.2MPa of maximum equivalent stresses are shown respectively in case model thicknesses are 25mm, 45mm and 65mm. By use of the simulation result at this study, it is possible to find adhesive behavior of aluminum foam and be applied to real adhesive joint structure without experiment by sparing experimental cost and time

Tapered double cantilever beam (TDCB) specimens are the most commonly used test configurations to measure the fracture toughness of composites and adhesive joints. The material used in this study is aluminum alloy. For the impact analysis, load and displacement applied from pin onto end block as well as the crack energy release rate are calculated and compared with the finite element analysis results. The energy release rate increases with the velocity increases. As TDCB model with the same condition as experiment is simulated and analyzed, the fracture behavior can be estimated with the analysis result similar to experiment. The simulation results can be agreed with experimental graph and all experimental data at this study can be verified. These experimental results can be applied into real field effectively. It is found that the energy release rates measured from impact tests on the specimens can be predicted by the finite element model suggested in this study.

국내의 경우 콘크리트 포장의 내구연한이 가까워짐에 따라 많은 구간에서 유지보수의 수요가 증가하고 있다. 최근 들어 적용사례가 증가하고 있는 접착식 콘크리트 덧씌우기(BCO, Bonded Concrete Overlay) 는 기존 콘크리트 포장의 상태가 비교적 양호한 구간에 실시하는 공법으로 완전부착을 통한 일체화 거동으로 높은 구조적 안정성을 확보하는 특징이 있다. 그러나 현행 덧씌우기 설계법의 경우 다양한 설계조건을 고려하지 못하고 경험적인 방법에 근거하고 있으므로 설계의 입력변수 설정부터 설계과정에 이르기까지의 원리에 대한 체계적인 정립이 되어 있지 않은 실정이다. 접착식 콘크리트 덧씌우기가 적용된 국외 사례를 살펴보면, 미국의 경우 일반적으로 덧씌우기 두께 설계를 통하여 8~16cm로 시공하고 있으나 국내의 경우 경험적으로 기존 포장층을 5cm절삭한 후 5cm의 덧씌우기 두께로 시공하는 것이 일반적이다. 따라서 국내의 경우에도 공용수명의 증가 및 유지보수 비용 감소를 위해 교통량과 지역적 특성을 고려한 포장 두께설계의 기준이 필요한 것으로 판단된다. 덧씌우기 설계 기준정립을 위해 각 구간의 접착식 콘크리트 덧씌우기의 기본 이력 및 공용 중 발생하는 포장파손에 대한 체계적인 data 구축이 필요하다. 본 연구에서는 국내 고속도로 BCO구간의 포장 파손 및 파손양을 수집한 후 MicroPaver 프로그램을 이용하여 PCI(Pavement Condition Index)를 산정 하였으며 이를 미국의 LTPP data의 구간별 PCI와 비교하여 덧씌우기 두께에 따른 공용수명과 PCI의 상관관계를 분석하였다. 이를 통해 국내 BCO구간의 공용성을 분 석하여 장기적인 BCO의 공용성을 평가하고자 하였다. 접착식 콘크리트 덧씌우기에 대하여 LTPP data의 덧씌우기 두께를 8~10cm, 11~13cm 및 14~16cm으로 구분하여 누적교통량 증가에 따른 PCI의 감소율을 확인한 결과 각 덧씌우기 두께별로 1×106 ESAL 증가시 PCI의 감소율을 확인할 수 있었으며 덧씌우기 두께가 두꺼울수록 PCI 감소율이 줄어드는 경향이 나타났다. 5cm 덧씌우기 두께의 국내 현장계측 구간과 LTPP data를 비교할 경우 두께별 약 2배∼5배의 공용수명 차이를 확인할 수 있었다. 이처럼 현행 덧씌우기 두께를 키울 경우 공용수명의 증진효과를 나타낼 수 있으므로 최소두께 기준의 상향으로 BCO의 장기공용성을 확보해야 할 것으로 판단된다.

PURPOSES: The performance of tack coat, commonly used for layer interface bonding, is affected by application rate and curing time. In this study, bonding strength tests were performed according to the application rate and curing time of asphalt emulsion. Based on finding from this study, optimum application rates and curing times are proposed. METHODS: In order to investigate bonding characteristic of asphalt emulsion, tests were performed on both asphalt concrete pavement and portland concrete pavement. Also, asphalt emulsions were tested at the application rate of 0, 0.2, 0.4, 0.6, and 0.8l/m2 and at the curing time of 0, 0.5, 1, 2, and 24 hours. Pull-off test and shear bonding strength test, which commonly used for bonding strength measurement of asphalt emulsion, were adopted for this study. To assess field performance under different testing condition, asphalt emulsions were applied to in-service pavement. Throughout coefficient of determination analysis between material index properties from asphalt emulsion and mechanical response from bonding strength tests, performance correlativity was analyzed. RESULTS: Test results show that optimum application rate for asphalt overlay on asphalt concrete pavement (AOA) and asphalt overlay on concrete pavement (AOC) was 0.4~0.5l/m2 and 0.3~0.5l/m2, respectively. According to the curing time increment, tensile strength and shear strength of AOC were increased to 22~44% and 20~39%, respectively. AOA case also show strength increment in tensile strength (42%) and shear strength (9%). We tested the applicability of tack coat materials at the field sites, and our findings demonstrated that the bonding (for D and E) and rapid curing (for B, C, and D, E) performances were superior than others. Among material index properties, there was a high correlation between penetration ratio and bonding strength test result. CONCLUSIONS : Result show that interlayer bonding strength was affected by asphalt emulsion type, application rate and curing time. AOC required slightly higher application (0.1l/m2) than AOA. Both AOA and AOC cases show higher strength at longer curing time. Up to 2hours of curing, rapid strength increments were observed, but strength increment ratio was decreased after 2hours of curing. From the observed correlation between penetration ratio and bonding strength, it is expected that penetration ratio can be used as one of important factors affecting bonding strength analysis.

PURPOSES : Bonded concrete overlay is a favorable maintenance method since the material properties are similar to existing concrete pavements. In addition, bonded concrete overlay has advantage of structural performance since the overlay layer and the existing pavement perform as a monolithic layer. It is important to have suitable bond strength criteria to secure the performance of bonded concrete overlay. This study aimed to investigate the factors influencing bond strength characteristics between existing concrete pavement and overlay material. METHODS: Bond strength between overlay and existing pavement are measured and analyzed for various conditions such as the type of overlay materials, compressive and flexure strength of overlay and existing pavement, and deterioration status of existing pavement. RESULTS: The strength of overlay material does not significantly influence the bond strength. The overlay of ultra-rapid hardening cement generally gives low bond strength. However, ultra rapid hardening polymer modified concrete gives robust bond strength. The deterioration of existing concrete significantly decrease the bond strength. CONCLUSIONS: Bond strength of bonded concrete overlay highly depends on condition of existing concrete pavement rather than overlay material.

알루미늄 폼을 볼트나 너트를 이용하여 체결한다면 경량성이 감소되므로 접착제로 접합하는 것이 가 장 효율적이다. 이런 알루미늄 폼 접착 구조물에 대한 충격 피로 특성과 접착 합면에 대한 파괴인성 연 구는 매우 부족하며 또한 중요하다. 이에 따라 본 연구에서는 알루미늄 폼으로 만들어진 DCB모델을 접 착제로 접합한 후 두께를 변수로 하여 25mm 부터 45mm까지 10mm차이를 두어 실험과 컴퓨터 시뮬레 이션을 통하여 수행하였다. 실험은 MTS사의 인장 시험기를 사용하여 강제 변위 100mm를 주어 변위에 따른 전단력을 알아보았고, 실험과 똑같은 조건하에 ANSYS를 이용하여 유한요소해석을 수행하였다. 실험과 유한요소해석 값을 비교하여 접착제로 접합된 알루미늄 폼 구조물의 접착 합면에 대한 파괴인성을 고찰하였다.

Aluminum foam has many superb properties such as light weight, impact absorption and thermal resistance by comparing with original metallic materials. Composite materials made of aluminum foam have used at various fields as automotive bumper, shock absorption, vessel and aircraft. But it is inefficient to join aluminum foam with bolt and nut because of the property of light weight. In this study, this approach is investigated by joining aluminum foam with adhesive. Impact fatigue and failure toughness at the commissure of adhesive structure are studied by simulation analysis. This study aims to investigate the shear strength evaluation at shear mode of adhesively bonded joint with double cantilever beam(DCB) made of aluminum foam.

four kinds of models designed by the basis of British industrial standard and ISO international standard in this study. Energy release rates at mode 1 are investigated by the fatigue analysis of aluminum foam TDCB model bonded with adhesive. These analysis models are compared each other by classifying four models into m values with 2, 2.5, 3 and 3.5. The value of m as the gradient of model is represented with the function of crack length(a) and height of model(h). Through the correlation relation, the fracture behavior of bonded material is analyzed and these analysis results can be applied to composite structures of various areas. Mechanical property and fracture toughness of composite material are also analyzed in this study.

PURPOSES : This study aimed to evaluate the feasibility of AASHTO86 design method for Bonded Concrete Overlay. METHODS : The Feasibility of AASHTO86 design method for Bonded Concrete Overlay is investigated based on the following study : i) Sensitivity analysis of designed service life of Bonded Concrete Overlay by major design input for AASHTO86 guide. ii) Comparison of actual Bonded Concrete Overlay life and predicted Bonded Concrete Overlay life by AASHTO86. iii) Finding the stress component influence the potential distress of Bonded Concrete Overlay based on 3-d FEM analysis. iv) Exploring the limitation of AASHTO86 in the aspect of design input. RESULTS : Sensitivity analysis showed that the condition of existing pavement significantly on the Bonded Concrete Overlay life. Also the overlay thickness affect the Bonded Concrete Overlay life. The comparison of actual Bonded Concrete Overlay life and predicted Bonded Concrete Overlay life showed relatively good agreement when the early distress sections are excluded in comparison. Bonding stress occurred at the interface may be larger than the bond strength used in the specification of Bonded Concrete Overlay construction. CONCLUSIONS : Bonded Concrete Overlay life predicted by the AASHTO86 may not be reliable. Number of points to improve the reliability in the design of Bonded Concrete Overlay are suggested in this study.

In this paper, the features of fatigue crack growth under ModeⅠ loading are studied. Double cantilever beam specimens were used. The effects of adherend thickness, rubber modification and adhesive thickness on fatigue crack growth were examined. The experimental results show that some of these parameters do apparently affect fatigue crack growth. Resistance to ModeⅠ fatigue crack growth are increased by rubber modification. The effects of adhesive thickness and rubber content on fatigue crack growth were explained by von Mises's equivalent stress using BEM analysis.

PURPOSES: In Korea, rapid maintenance of distressed concrete pavement is required to prevent traffic jam of the highway. Asphalt concrete overlay has been used as a general maintenance method of construction for aged concrete pavement. AC overlay on existing concrete pavements experience various early distresses such as reflection crack, pothole and rutting, due to different physical characteristics between asphalt overlay and existing concrete pavement. Bonded concrete overlay(BCO) is a good alternative since it has advantages that can reduce various distresses during the service life since overlay material has similar properties with existing concrete pavements. Recently, BCO which uses the ultra rapid harding cement has been applied for maintenance of highway. BCO has advantage of structural performance since it does monolithic behave with existing pavement. Therefore, it is important to have a suitable bond strength criteria for securing performance of BCO. Bond strength criteria should be larger than normal tensile stress and horizontal shear stress occurred by traffic and environmental loading at bond interface. Normal tensile stress and horizontal shear stress need to estimated for the establishment of practical bond strength criteria. METHODS: This study aimed to estimate the bond stresses at the interface of BCO using the three dimensional finite element analysis. RESULTS: As a result of this study, major failure mode and maximum bond stress are evaluated through the analysis of normal tensile stress and horizontal shear stress for various traffic and environmental load conditions. CONCLUSIONS: It was known that normal tensile stresses are dominated by environmental loading, and, horizontal shear stresses are dominated by traffic loading. In addition, bond failure occurred by both of normal tensile stresses and horizontal shear stresses; however, normal tensile stresses are predominated over horizontal shear stresses.

Various adhesive materials are used in flip chip packaging for electrical interconnection and structural reinforcement. In cases of COF(chip on film) packages, low temperature bonding adhesive is currently needed for the utilization of low thermal resistance substrate films, such as PEN(polyethylene naphthalate) and PET(polyethylene terephthalate). In this study, the effects of anhydride and dihydrazide hardeners on the low-temperature snap cure behavior of epoxy based non-conductive pastes(NCPs) were investigated to reduce flip chip bonding temperature. Dynamic DSC(differential scanning calorimetry) and isothermal DEA(dielectric analysis) results showed that the curing rate of MHHPA(hexahydro-4-methylphthalic anhydride) at 160˚C was faster than that of ADH(adipic dihydrazide) when considering the onset and peak curing temperatures. In a die shear test performed after flip chip bonding, however, ADH-containing formulations indicated faster trends in reaching saturated bond strength values due to the post curing effect. More enhanced HAST(highly accelerated stress test) reliability could be achieved in an assembly having a higher initial bond strength and, thus, MHHPA is considered to be a more effective hardener than ADH for low temperature snap cure NCPs.

This paper has fabricated insulation gang-form adhering general gang-form to the polyisocyanurate board and analyzed type of members, temperature record by locations and strength development after placing the concrete, in order to ensure efficient concrete quality under cold weather. According to our test, we can see that general gang-form member with curing under the same conditions as the actual field has a trend of constantly decreasing concrete temperature regardless to surface or central area due to rapid outdoor air temperature reduction, while in the case of insulation gang-from I and II, temperature increased up to around 25℃ after 12 hours under rapid outdoor air temperature change and temperature distribution did not appear large separation according to hydration reaction measurement locations. In addition, results of measurement for temperature records on weak insulation area by types of gang-forms showed that the temperature record distribution on the form tie surface and horizontal bar surface of angle bar has generally similar trend as the temperature records on the surface of the insulation gang-form, while corner area of the insulation gang-form did not have large insulation effect. It is determined that it requires additional curing measure for the weak corner area of the insulation gang-form in the future.

Aluminum foam with the property as the excellent impact absorption has been widely used recently. It is necessary to study fracture energy due to fracture toughness by the use of adhesive joint at aluminum foam. This study aims at strength evaluation about adhesive joint on aluminum foam and the fracture of bonded DCB model with this material property is analyzed by simulation. These models are designed by differing in height on the basis of British industrial and ISO standards. As the value of height at model is higher, bonded part is separated to the end. By comparing some analysis results with experimental data, these data could agree with each other. By the verification with experimental results, these all simulation results in this study can be applied on real composite structure with aluminum foam material effectively. The fracture behavior and mechanical property can also be examined by this study.

고속도로에서 재령이 20년이 넘는 노후 콘크리트가 늘어남에 따라 콘크리트 포장의 보수/보강이 중요한 이슈로 대두되고 있다. 노후 콘크리트 포장의 보강 대안으로서 아스팔트 덧씌우기가 많이 사용되고 있으나 반사균열 및 포트홀 등 체류수로 인한 문제가 심각하게 대두되고 있다. 본 연구는 반사균열 및 체류수의 문제를 최소화하기 위해 고안된 접착식 방수층을 소개하였으며 포장가속시험을 통해 일반 택코팅을 적용한 합성단면포장과 비교평가를 실시하였다. 실험은 강우를 모사하기 위해 물을 뿌리면서 진행하였고 덧씌우기 포장체의 거동 및 수분 저항 특성을 분석하였다. 연구결과 접착식 방수층은 아스팔트 포장과 콘크리트 포장이 일체로 거동하는 것을 도와주기 때문에 아스팔트 포장체에 발생하는 거동이 일반 택코팅 구간과 완전히 다른 것으로 나타났다. 또 수분의 유입을 최소화하므로 결과적으로 반사균열의 발생을 약 70% 지연시키는 것으로 나타났으며, 체류수로 인한 손상도 줄여주는 것으로 나타났다.

15년 정도의 짧은 역사를 가지고 있는 중온 아스팔트 포장은 국내·외적으로 현재 가장 관심대상이 되는 에너지 절약과 환경보호를 추구하는 도로건설분야의 그린기술이다. 본 연구는 이러한 중온 아스팔트의 물성평가를 아스팔트 덩어리 전체 거동으로 고려한 기존 침입도, 점도, 그리고 수퍼페이브에 의한 아스팔트 시험방식으로부터 벗어나 아스팔트 피막두께에 따른 물성평가로 시각을 바꾸어 새로운 프로토콜을 제시하고 결과분석에 따른 새로운 평가기준제안을 하는 것이 목적이다. 이를 위해 기존에 개발한 DSR Moisture Damage의 실험 및 분석의 기본틀을 ARES장비를 통해 각 피막두께별 물성을 측정하고 분석하였다. 분석결과를 통해 200μm와 400μm 사이에 물성의 급격한 변화를 볼 수 있는 한계피막두께가 존재하고 또한 가열아스팔트와 중온아스팔트가 가지고 있는 한계피막두께근처에서 발생하는 물성의 급격한 변화가 서로 다르다는 것을 확인할 수 있었다. 이런 결과를 통해 기존 가열 아스팔트와 성질이 다른 중온 아스팔트를 제대로 평가하기 위해서는 200μm와 400μm 사이 피막두께의 물성평가를 고려해야한다는 것을 제안한다.

본 연구에서는 강재가 맞대기 이음으로 연결될 경우 CFRP(Carbon Fiber Reinforced Plastic) 쉬트(sheet)를 맞대기 이 음부에 접착할 경우 강재 및 CFRP 쉬트에 발생하는 응력을 해석하였다. CFRP 쉬트로 보강한 경우 접착제의 두께, 강재와의 접착 길이, CFRP 강도 변화를 매개변수로 사용하여 이 매개변수에 변화에 따른 이음부의 응력분포를 분 석하였다. 또한 CFRP를 여러 층으로 접착할 경우 각 층의 강도를 다르게 변화시켜 맞대기 이음부에 유리한 응력분 포를 나타내는 CFRP의 강도를 제시하였다. 본 연구를 위해 빠른 수렴성을 가지며 왜곡된 요소형상에서도 정확한 응력결과를 보이는 강화변형률장(Enhanced Assumed Strain Field)을 사용한 평면변형률 유한요소에 대한 프로그램을 작성하였다.