• Title/Summary/Keyword: interfacial debonding

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Multi-scale Progressive Fatigue Damage Model for Unidirectional Laminates with the Effect of Interfacial Debonding (경계면 손상을 고려한 적층복합재료에 대한 멀티스케일 피로 손상 모델)

  • Dongwon Ha;Jeong Hwan Kim;Taeri Kim;Young Sik Joo;Gun Jin Yun
    • Composites Research
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    • v.36 no.1
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    • pp.16-24
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    • 2023
  • This paper presents a multi-scale progressive fatigue damage model incorporating the model for interfacial debonding between fibers and matrix. The micromechanics model for the progressive interface debonding was adopted, which defined the four different interface phases: (1) perfectly bonded fibers; (2) mild imperfect interface; (3) severe imperfect interface; and (4) completely debonded fibers. As the number of cycles increases, the progressive transition from the perfectly bonded state to the completely debonded fiber state occurs. Eshelby's tensor for each imperfect state is calculated by the linear spring model for a damaged interface, and effective elastic properties are obtained using the multi-phase homogenization method. The fatigue damage evolution formulas for fiber, matrix and interface were proposed to demonstrate the fatigue behavior of CFRP laminates under cyclic loading. The material parameters for the fiber/matrix fatigue damage were characterized using the chaotic firefly algorithm. The model was implemented into the UMAT subroutine of ABAQUS, and successfully validated with flat-bar UD laminate specimens ([0]8,[90]8, [30]16) of AS4/3501-6 graphite/epoxy composite.

Development of Numerical Tool considering Interfacial Fracture Behavior in Repaired RC Structure (보수.보강된 RC 구조물의 경계면 파괴를 고려한 수치해석 기법 개발)

  • 임윤묵;김문겸;신승교;고태호
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.04a
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    • pp.553-558
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    • 2000
  • In this study, a numerical simulation that can effectively predict the interfacial fracture behavior in repaired structures is developed using the axial deformation link elements. In repaired structures, concrete and interface are considered as quais-brittle materials, and steel plate as a repair material and reinforcement are modeled as elasto-plastic materials. The behavior of repaired reinforced concrete structures under flexural loading conditions is numerically simulated, and compaired with experimental results. The strengthening effect according to the length and thickness of the repair material is studied and rip-off, debonding and rupture failure mechanism of interface between substrate and repair materials are detected. It is shown that the interface properties affect on the mechanical behavior of repaired structures. Therefore, the developed numerical method using axial deformation link elements can be used for determining the strengthening effects and failure mechanism of repaired structures.

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Experimental Study on the Bond[ Behavior with Concrete Surface Preparation. and Anchorage Type of CFRP (콘크리트 표면처리와 CFRP 단부정착 방법에 따른 부착특성실험)

  • 유영준;조정래;정우태;박종섭;박영환
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.05a
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    • pp.579-584
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    • 2003
  • For strengthening deteriorated concrete structures, externally bonded FRP sheets or plates using epoxy resins are widely used. For the external FRP composites to be effective in improving the performance of the structure, bond between FRP composites and concrete is required. In general, the most frequently observed failure mode in FRP strengthened concrete structures is debonding failure at the interfacial section between FRP and concrete. Therefore, it is very important to find out the interfacial behavior properties. This paper presents experimental results of the relationship of concrete and FRP sheet for some conditions including concrete compressive strength, concrete surface preparation to observe the bond behavior between concrete and FRP sheet and various anchorage types to increase the bond capacity of FRP sheet.

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Analysis of Interfacial Shear Strength of Fiber/Epoxy Composites by Microbond Test and Finite Element Method (미소접합시험과 유한요소법을 통한 섬유/에폭시 복합재의 계면 전단강도 해석)

  • Kang, Soo-Keun;Lee, Deok-Bo;Choi, Nak-Sam
    • Composites Research
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    • v.19 no.4
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    • pp.7-14
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    • 2006
  • Interfacial shear strength between epoxy and carbon fiber has been analyzed utilizing the microbond specimen with an epoxy micro-droplet adhered onto single carbon fiber. The interfacial shear stress distributions along the fiber/matrix interface were calculated by finite element analysis using three kinds of finite element models such as droplet model, circular-crosssection model and pull-out model. Conclusions were obtained as follows. (1) Interfacial shear stress distribution showed that larger stresses were concentrated in the fiber/matrix interface for microbond test than for pull-out test. Thus, debonding at the fiber/matrix interface during microbond test was liable to occur at low load level. (2) Microbond test showed higher interfacial strength which was caused by various effects of micro-droplet geometry and size as well as stress concentration in the region contacting with the micro-vise tip.

Numerical Analysis of Fracture Behavior in Aged RC Structures (보강된 노후 구조물 파괴거동 예측을 위한 수치해석기법 개발)

  • 신승교;고태호;김문겸;임윤묵
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.10b
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    • pp.1031-1036
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    • 2000
  • In this study, a numerical simulation that can effectively predict the strengthening effect of repaired aged RC structures is developed using the axial deformation link elements. In repaired structures, concrete and interface are modeled as quasi-brittle materials. An elastic-perfectly plastic constitutive relationship is introduced for reinforcing bars. Also, a linear-elastic relationship for repair materials such as FRP or CFS. Structural deterioration in terms of corrosion of steel rebar is considered. The interfacial property between steel and concrete which is reduced by corrosion of steel rebar is obtained by comparing numerical results with experimental results of pull out tests. Obtained values are used in repaired reinforced concrete structures under flexural loading conditions. To investigate strengthening effect of the structures repaired with carbon fiber sheet(CFS), repaired and unrepaired RC structures are analyzed numerically. From analysis, rip-off, debonding and rupture failure mechanisms of interface between substrate and CFS can be determined. Finally, strengthening effect according to the variation of interfacial material properties is investigated, and it is shown that interfacial material properties have influence on the mechanical behavior of repaired structure systems Therefore, the developed numerical method using axial deformation link elements can use for determining the strengthening effects and failure mechanism of repaired aged RC structure.

Elastoplastic Behavior and Progressive Damage of Circular Fiber-Reinforced Composites (원형섬유강화 복합재료의 탄소성거동 및 점진적 손상)

  • Lee, Haeng Ki;Kim, Bong Rae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.1A
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    • pp.115-123
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    • 2008
  • The performance prediction of fiber-reinforced composites has attracted engineer's attention in many fields, and the various theoretical and numerical methods have been proposed to predict the behavior of the fiber-reinforced composites. An evolutionary damage model for progressive interfacial debonding between circular fibers and the matrix is newly incorporated into the micromechanics-based elastoplastic model proposed by Ju and Zhang (2001) in this framework. Using the proposed model, a series of numerical simulations are conducted to illustrate the elastoplastic behavior and evolutionary damage of the framework. Furthermore, the influence of the evolutionary interfacial debonding on the behavior of the composites is investigated by comparing it with the result of a stationary damage model.

Curing Behavior and Interfacial Properties of Electrodeposited Carbon Fiber/Epoxy Composites by Electrical Resistivity Measurement under Tensile/Compressive Tests (전기증착된 탄소섬유/에폭시 복합재료의 인장/압축 하중하에서의 전기저항 측정법을 이용한 경화 및 계면특성)

  • Park, Joung-Man;Lee, Sang-Il;Kim, Jin-Won
    • Journal of Adhesion and Interface
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    • v.2 no.1
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    • pp.9-17
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    • 2001
  • Curing behavior and interfacial properties were evaluated using electrical resistance measurement and tensile/compressive fragmentation test. Electrical resistivity difference (${\Delta}R$) during curing process was not observed in a bare carbon fiber. On the other hand, ${\Delta}R$ appeared due to the matrix contraction in single-carbon fiber/epoxy composite. Logarithmic electrical resistivity of the untreated single-carbon fiber composite increased suddenly to the infinity when the fiber fracture occurred under tensile loading, whereas that of the ED composite reached relatively broadly up to the infinity. Comparing to the untreated case, interfacial shear strength (IFSS) of the ED treated composite increased significantly in both tensile fragmentation and compressive Broutman test. Microfailure modes of the untreated and the ED treated fiber composite showed the debonding and the cone shapes in tensile test, respectively. For compressive test, fractures of diagonal slippage were observed in both untreated and the ED treated composite. Sharp-end shape fractures exhibited in the untreated composite, whereas relatively dull fractures showed in the ED Heated composite. It is proved that ED treatments affected differently on the interfacial adhesion and microfailure mechanism under tensile/compressive tests.

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Interfacial Adhesion Properties of Oxygen Plasma Treated Polyketone Fiber with Natural Rubber (폴리케톤 섬유의 산소 플라즈마 처리에 따른 천연고무와의 계면접착 특성)

  • Won, Jong Sung;Choi, Hae Young;Yoo, Jae Jung;Choi, Han Na;Yong, Da Kyung;Lee, Seung Goo
    • Journal of Adhesion and Interface
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    • v.13 no.1
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    • pp.45-50
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    • 2012
  • Recently developed polyketone fiber has various applications in the mechanical rubber goods as reinforcement because of its good mechanical properties. However, its surface is not suitable for good adhesion with the rubber matrix. Thus, a surface modification is essential to obtain the good interfacial adhesion. Plasma treatment, in this study, has been conducted to modify the surface of the polyketone fiber. The morphological changes of the fibers by oxygen plasma treatment were observed by using SEM and AFM. The chemical composition changes of PK fiber surface treated with oxygen plasma were investigated using an XPS (X-ray photoelectron spectroscopy). Finally, the effect of these changes on the interfacial adhesion between fiber and rubber was analyzed by using a microdroplet debonding test. By the plasma treatment, oxygen moieties on the fiber surface increased with processing time and power. The surface RMS roughness increases until the proper processing condition, but a long plasma processing time resulted in a rather reduced roughness because of surface degradation. When the treatment time and power were 60 s and 80 W, respectively, the highest interfacial shear strength (IFSS) was obtained between the PK fiber and natural rubber. However, as the treatment time and power were higher than 60 s and 80 W, respectively, the IFSS decreased because of degradation of the PK fiber surface by severe plasma treatment.

Interfacial Damage Sensing and Evaluation of Carbon and SiC Fibers/Epoxy Composites with Fiber-Embedded Angle using Electro-Micromechanical Technique (Electro-Micromechanical시험법을 이용한 섬유 함침 각에 따른 탄소와 SiC 섬유강화 에폭시 복합재료의 계면 손상 감지능 및 평가)

  • Joung-Man Park;Sang-Il Lee;Jin-Woo Kong;Tae-Wook Kim
    • Composites Research
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    • v.16 no.2
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    • pp.68-73
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    • 2003
  • Interfacial properties and electrical sensing fer fiber fracture in carbon and SiC fibers/epoxy composites were investigated by the electrical resistance measurement and fragmentation test. As fiber-embedded angle increased, the interfacial shear strength (IFSS) of two-type fiber composites decreased, and the elapsed time takes long until the infinity in electrical resistivity. The initial slope of electrical resistivity increased rapidly to the infinity at higher angle, whereas electrical resistivity increased gradually at small angle. Furthermore, both fiber composites with small embedded angle showed a fully-developed stress whitening pattern, whereas both composites with higher embedded angle exhibited a less developed stress whitening pattern. As embedded angle decreased, the gap between the fragments increased and the debonded length was wider for both fiber composites. Electro-micromechanical technique could be a feasible nondestructive evaluation to measure interfacial sensing properties depending on the fiber-embedded angle in conductive fiber reinforced composites.

The Interfacial Stresses in Concrete Beam Strengthened with Carbon Fiber Sheets due to Temperature Rising (온도상승에 따른 탄소섬유시트 보강 콘크리트보의 계면응력)

  • Choi, Hyoung-Suk;Kim, Seong-Do;Cheung, Jin-Whan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.6
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    • pp.109-118
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    • 2008
  • Carbon fiber reinforced polymer(CFRP) can be bonded to the soffit of a concrete beam as a means of repairing and strengthening the beam. In such beams, materials, concrete and carbon fiber sheets, are different in coefficient of thermal expansion. Consequently, interfacial shear stresses can be increased and debonding failure may occur at the plate ends due to temperature rising. This paper presents a method of approximate closed-form solutions for the interfacial shear stresses and conducts a beam test to compare the numerical results. In case of temperature rising over $30^{\circ}C$, interfacial stress of 0.91MPa is occurred at the end of sheet. Therefore, using carbon fiber sheet for strengthening the concrete beam, it is necessary to consider the thermal effects and to evaluate the long time behavior of the concrete beam by temperature change.