• Title, Summary, Keyword: 접착 조인트

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A Study on the Strength Evaluation and Defect Detection Capability of Adhesive Joint with CNTs (CNT를 첨가한 접착조인트의 결함탐지능 및 강도 평가에 관한 연구)

  • Kim, Tae-Hyeong;Kim, Cheol-Hwan;Choi, Jin-Ho
    • Composites Research
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    • v.31 no.4
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    • pp.151-155
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    • 2018
  • Mechanical joint and adhesive joint are two typical joining methods for structures. The adhesive joints distribute the load over a larger area than mechanical joints and have excellent fatigue properties. However, the strength of adhesive joint greatly depends on the environmental conditions and the skill of the operator. Therefore, there is a need for techniques to evaluate the quality of the adhesive joints. The electric resistance method is a very promising technique for detecting defects by measuring the electrical resistance of an adhesive joint in which CNTs are dispersed in an adhesive. In this study, Aluminium-Aluminium adhesive single lap joint specimens were fabricated by using the adhesive dispersing CNTs using a sonicator and a 3-roll mill, and the static strengths and defect detection capabilities of the joints using the electrical resistance method were evaluated according to the CNTs content.

Fracture Mechanical Characterization of Bi-material Interface for the Prediction of Load Bearing Capacity of Composite-Steel Bonded Joints (복합재료-탄소강 접착제 결합 조인트의 하중지지 능력 예측을 위한 이종 재료 접합 계면의 파괴 역학적 분석)

  • Kim, Won-Seok;Shin, Kum-Chel;Lee, Jung-Ju
    • Composites Research
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    • v.19 no.4
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    • pp.15-22
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    • 2006
  • One of the primary factors limiting the application of composite-metal adhesively bonded joints in structural design is the lack of a good evaluation tool for the interfacial strength to predict the load bearing capacity of boned joints. In this paper composite-steel adhesion strength is evaluated in terms of stress intensity factor and fracture toughness of the interface corner. The load bearing capacity of double lap joints, fabricated by co-cured bonding of composite-steel adherends has been determined using fracture mechanical analysis. Bi-material interface comer stress singularity and its order are presented. Finally stress intensities and fracture toughness of the wedge shape bi-material interface corner are determined. Double lap joint failure locus and its mixed mode crack propagation criterion on $K_1-K_{11}$ plane have been developed by tension tests with different bond lengths.

On-line Cure Monitoring of Adhesive Joints by Dielectrometry (유전기법을 이용한 접착 조인트의 실시간 경화 모니터링)

  • 권재욱;진우석;이대길
    • Composites Research
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    • v.16 no.4
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    • pp.51-58
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    • 2003
  • Since the reliability of adhesively bonded joints is much dependent on the curing status of thermosetting adhesive, the on-line cure monitoring during the cure of adhesively joints could improve the quality of adhesively bonded joints. In this work, the dielectric method which measures the dissipation factor of the adhesive during the cure of joints and converts it into the degree of cure of the adhesive was devised. The relation between the dissipation factor and the degree of cure of adhesive was investigated, which could eliminate the temperature effect on the dissipation factor that is a strong function of the degree of cure and temperature of adhesive. From the investigation, it was found that the dissipation factor showed a trend similar to the cure rate of the adhesive.

A study on the bonding strength of co-cured T800/epoxy composite-aluminum single lap joint according to the forming and additional pressures (동시 경화법으로 제조된 T800/에폭시 복합재료-알루미늄 단면겹치기조인트의 성형압력 및 부가압력에 따른 접착강도에 관한 연구)

  • Son, Dae-Sung;Bae, Ji-Hun;Chang, Seung-Hwan
    • Composites Research
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    • v.24 no.5
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    • pp.23-28
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    • 2011
  • In this paper, the bonding strengths of co-cured T800 carbon/epoxy composite-aluminum single lap joints with and without additional pressures were investigated using the pressure information induced by the fiber tension during a filament winding process. The specimens of all the tests were fabricated by an autoclave vacuum bag de-gassing molding being controlled forming pressures (absolute pressures of 0.1MPa, 0.3MPa and 0.7MPa including vacuum). A special device which can act uniform additional pressures on the joining part of the single lap joint specimen was designed to measure the bonding strengths of composite-aluminum liners of type III hydrogen pressure vessel fabricated by a filament winding process. After the three different additional pressures (absolute pressures of 0.1MPa, 0.3MPa and 0.7MPa) were applied to the specimens the effect of the additional pressures on the bonding strengths of the co-cured single-lap joints were evaluated.

A Study on Failure Strength of Single Lap Adhesive Joint with Thick Adherend (후판 단일 겹침 접착 조인트의 파손강도에 관한 연구)

  • Park, Jae-Hyun;Choi, Jin-Ho;Kweon, Jin-Hwe
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.2
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    • pp.111-118
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    • 2010
  • The joints are often the weakest areas in composite structures. In this paper, the thick aluminum-aluminum joint specimens and thick composite-aluminum single lap adhesive joint specimens were manufactured and the tensile tests were performed. The fracture mode of each specimen was investigated and the modified damage zone theory based on the yield strain was proposed and compared with experimental failure load of each mode. The failure loads of the thick aluminum-aluminum joint and composite-aluminum joint were predicted by the same failure criterion and they could be predicted to within 19.3% using the damage zone ratio method for all 14 cases investigated.

End-Shape Effect for Stress Concentration Reduction of Composite Single-Lap Bonded Joint (끝단형상에 따른 복합소재 단일겹치기 체결부의 응력집중 저감에 관한 연구)

  • Kim, Jung-Seok;Hwang, Jae-Yeon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.3
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    • pp.333-340
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    • 2011
  • We evaluated the stress-reduction effect for different shapes of a composite adherend with or without a spew fillet. Six different single-lap joint specimens were modeled and assessed using nonlinear finite element analysis. Moreover, we investigated the effect of the stiffness ratio of the adherend and adhesive. The single-lap joint with normal tapering had the highest stress values, and the single-lap joint with reverse tapering and a spew fillet had the lowest stress values. The composite adherends with higher stiffness had lower stress values, and the adhesives with lower stiffness had lower stress values.

An Analytic Study for the Adhesively Bonded Tubular Double Lap Joint (원형 이중겹치기 접착조인트의 해석해에 관한 연구)

  • 이수정;이대길
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.6
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    • pp.1412-1420
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    • 1994
  • The adhesively bonded tubular double lap joint has better torque transmission capability and reliability in bonding operation than the single lap joint. In this paper, an analytic solution for the torque transmission capabilities and stress distributions of the adhesively bonded tubular double lap joint was derived assuming the linear properties of the adhesive and adherends. From the calculation, it was found that the torque transmission capabilities of the double lap joint was more than 40% larger compared to that of the single lap joint.

Interfacial Fracture Toughness Measurement of Composite/metal Bonding (복합재료/금속 접착 계면의 파괴인성치 측정)

  • Kim, Won-Seock;Lee, Jung-Ju
    • Composites Research
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    • v.21 no.4
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    • pp.7-14
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    • 2008
  • Prediction of the load-bearing capacity of an adhesive-bonded Joint is of practical importance for engineers. This paper introduces interface fracture mechanics approach to predict the load-bearing capacity of composite metal bonded joints. The adhesion strength of composite/steel bonding is evaluated in terms of the energy release rate of an interfacial crack and the fracture toughness of the interface. Virtual track closure technique (VCCT) is used to calculate energy release rates, and hi-material end-notched flexure (ENF) specimens are devised to measure the interfacial fracture toughness. Bi-material ENF specimens gave consistent mode II fracture toughness $(G_{IIc})$ values of the composite/steel interface regardless of the thickness of specimens. The critical energy release rates of double-lap joints showed a good agreement with the measured fracture toughness. Therefore. the energy-based interfacial fracture characterization can be a practical engineering tool for predicting the load-bearing capacity of bonded joints.

Effect of Micro-bolt Reinforcement for Composite Scarf Joint (복합재 스카프 조인트에서의 마이크로 볼트 보강에 대한 타당성 연구)

  • Lee, Gwang-Eun;Sung, Jung-Won;Kweon, Jin-Hwe
    • Composites Research
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    • v.32 no.1
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    • pp.37-44
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    • 2019
  • The reinforcement effect of micro-bolt for a bonded scarf joint was investigated. Three scarf ratios of 1/10, 1/20, and 1/30 were considered to examine the effect of scarf patch configuration on joint strength. To maintain the same density of micro-bolt, 16, 32, and 48 bolts were installed in the scarf joint specimens with scarf ratios of 1/10, 1/20, and 1/30, respectively. Tests were also carried out on the joints that are bonded with only adhesive and that are fastened with only micro-bolts to obtain reference values. The average failure loads of the adhesive joints with scarf ratios of 1/10, 1/20, and 1/30 were 29.7, 39.6, and 44.8 kN, respectively. In case of micro-bolt reinforcement, the failure loads at the same scarf ratios were 28.4, 37.2, and 40.1 kN, respectively, which corresponds to 96, 94, and 90% of the pure adhesive joint failure loads. In the case of using only micro-bolts, the failure loads were only 13-25% of the average failure loads of pure adhesive joints. Fatigue test was also conducted for the joints with scarf ratio of 1/10. The results show that the fatigue strength of hybrid joints using both adhesive and microbolts together slightly increased compared to the fatigue strength of adhesive joint, but the rate of increase was small to 2-3%. Through this study, it was confirmed that the reinforcement effect of micro-bolt is negligible in the scarf joints where shear stress is dominating the failure, unlike in the structure where peel stress is dominant.

Evaluation of Dispersivity and Resistance of the Adhesive Joint According to Dispersion Methods of CNT (CNT 분산 방법에 따른 접착조인트의 저항 및 분산성 평가)

  • Lee, Bong-Nam;Kim, Cheol-Hwan;Kweon, Jin-Hwe;Choi, Jin-Ho
    • Composites Research
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    • v.28 no.6
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    • pp.348-355
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    • 2015
  • NDT (Non Destructive Test) of the adhesive joints is very important because their strengths have greatly affected by the worker's skill and environmental condition. Recently, the electric impedance method in which 1-2 wt% CNT was dispersed in the adhesive and the electric resistance of the adhesive joint was measured was suggested for the defect detection of the adhesive joint. The uniform dispersion of CNT in the electric impedance method is very important to make a constant electric resistance of the adhesive joint and the accuracy of defect detection depends on the uniform dispersion. In this paper, the adhesive joints in which CNT was dispersed in the adhesive by the four dispersion methods were made and their electric resistance were measured. The pre-process and evaporation process of CNT using the ultrasonic method and agitation method was used and the effective dispersion method was suggested. Also, the criteria to evaluate the dispersivity was proposed.