• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.4
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• pp.402-410
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• 1996

Recently carbon fiber reinforced plastic(CFRP) has been used structural materials in corrosive environment such as for water, chemical tank and chemical pipes. However, mechanical properties of such materials may change when CFRP are exposed to corrosive environment for long periods of time. Therefore, it is important to understand the effect of moisture absorption on mechanical properties of the CFRP. In this study, degradation behavior of immersed carbon fiber/epoxy resin composite material was investigated using acoustic emission(AE) technique. Fracture toughness test are performed on the compact tension(CT) test specimens that are pilled by two types of laminates $[0^{\circ}_2$/$90^{\circ}_2]_3s$ and $[0^{\circ}_2$/$90^{\circ}_2]_6s$During the fracture toughness test, AE test was carried out to monitor the damage of CFRP by moisture absorption. In spite of the change of moisture absorption rate, the fracture toughness of CFRP was not change. As immersion time increased, AE event count numbers decreased in low amplitude range of AE for amplitude distribution histogram. The event in low amplitude range was known to be generated by debonding of matrix-fiber interface. Therefore, decrease of AE event count numbers in low amplitude range represents that debonding of matrix-fiber interface which was probably generated by moisture absorption.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.737-742
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• 1994

The fracture energy of glass fiber/carbon fiber/epoxy resin hybrid composite system was investigated in the aspect of fracture mechanism. Epoxy resin matrix was DGEBA-MDA-SN-HQ system. On the interface of glass fiber and matrix, post debone friction energy provided a major contribution to the fracture energy, and debonding energy and pull-out energy were of the similar value. In the case of fracture on the interface of carbon fiber and matrix, pull-out energy was the major contributor.

• Journal of Adhesion and Interface
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• v.5 no.4
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• pp.9-16
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• 2004

Silk fibers were subjected to argon and ethylene plasma treatments in order to improve the interfacial adhesion with polylactic acid (PLA). After the plasma surface treatment, the surface morphology and surface adhesion of silk fibers to the PLA resin were largely changed. Various plasma treatment conditions were used in this work: 10, 25, 50, 100 and 150 W of electric power, 1, 3, 5, 7 and 10 minutes of treatment time, and 10 and 50 sccm of a gas flow rate. The interfacial shear strength of plasma-treated Silk/PLA biocomposites was measured by a single fiber micro-droplet debonding test method. The result provided an optimal plasma treatment condition to obtain the improved interfacial adhesion in the Silk/PLA biocomposites.

• Steel and Composite Structures
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• v.26 no.3
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• pp.347-360
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• 2018

The aim of this paper is to evaluate the accuracy and reliability of the available bond-slip laws which are being used for the numerical modeling of Fiber Reinforced Polymer (FRP)/concrete interfaces. For this purpose, a set of Reinforced Concrete (RC) beams retrofitted with external FRP were modeled using the 3D nonlinear Finite Element (FE) approach. All considered RC beams have been previously tested and the corresponding experimental data are available in the literature. The failure modes of these beams are concrete crushing, steel yielding and FRP debonding. Through comparison of the numerical and experimental results, the effectiveness of each FRP/concrete bond-slip model for the prediction of the structural behavior of externally retrofitted RC beams is assessed. The sensitivity of the numerical results against different modeling considerations of the concrete constitutive behavior and bond-slip laws has also been evaluated. The results show that the maximum allowable stress of FRP/concrete interface has an important role in the accurate prediction of the FRP debonding failure.

• Korean Journal of Materials Research
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• v.6 no.9
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• pp.963-971
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• 1996

세라믹 강화 복합 재료의 모재로서 사용되는 무정형 PEEK가 보여주는 self-bonding 현상의 주 기구인 PEEK체인들의 확산(interdiffusion)과 뒤엉킴(entanglement)이 일어나기 위하여 PEEK의 접합 면에서 반드시 선행되어 일어나야 하는 젖음성의 정도에 미치는 접합 공정 변수의 영향을 C-mode acoustic microscopy를 이용하여 고찰하였다. 또한 self-bonding 된 PEEK시편들의 전단 변형시 전단 하중의 증가에 따라 일어나는 접합 면에서의 debonding 정도를 측정함으로써 접합 면에서 일어나는 파괴 거동을 관찰하였다. 각각의 접합 조건에서의 젖음성의 정도는 시간과 압력의 증가에 따라 다소 증가함을 보여 주었으나, 접합 온도와는 거의 무관함을 보여 주었다. 또한 전단 파괴 시험시 각각의 접합 조건 하에서 개발된 self-bonding강도의 80%-90%이상의 전단 하중이 가해진 후부터 debonding이 시작되어, 이 후 하중이 증가함에 따라 급속도로 진행되어 파괴가 일어남을 알 수 있었다.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.267-270
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• 2005

Recently, the damaged concrete structures are often strengthened or repaired using the polymer concrete or the polymer cement mortar. In the repaired concrete structures at early ages, internal stresses could be developed due to the differential drying shrinkage of the repair material. Due to the difference of the thermal coefficients of the repair material and existing concrete, additional stresses also could be developed as the structures are subjected to the ambient temperature changes. Theses environmentally-induced stresses can sometimes be large enough to cause damage to the structures, such as debonding of the interface between the two materials. In this study, a rational procedure was developed where anchors can be designed and installed to prevent damages in such structures by thermally-induced stresses. Finally, through the experimental and numerical study, the effects of the repair method using anchors with debonding was investigated and discussed the results.

• Structural Engineering and Mechanics
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• v.86 no.5
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• pp.663-671
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• 2023

Freeze-thaw cycles induce strength loss at the frozen soil-concrete interface and deterioration of bonding, which causes construction engineering problems. To clarify the deterioration characteristics of the interface under the freeze-thaw cycle, a frozen soil-concrete sample was used as the research object, an interface scanning electron microscope test under the freeze-thaw cycle was carried out to identify the micro index information, and an interface shear test was carried out to explore the loss law of interface shear strength under the freeze-thaw cycle. The results showed that the integrity of the interface was destroyed, and the pore number and pore size of the interface increased significantly with the number of freeze-thaw cycles. The connection form gradually deteriorates from surface-to-surface contact to point-to-surface contact and point-to-point contact, and the interfacial shear strength decreases the most at 0-3 freeze-thaw cycles, with small decreases from to 3-8 cycles. After 12 freeze-thaw cycles, the interfacial shear strength tends to be stable, and shear the failure occurs internally in the soil.

• Journal of Adhesion and Interface
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• v.14 no.3
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• pp.117-120
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• 2013

The prepreg material is a sheet of the reinforcement pre-impregnated with a resin. In this study, two types of prepreg were prepared with a general phenolic resin and the polyvinyl butyral (PVB) modified phenolic resin, respectively, with resin content of 40 wt%. After resin impregnation, the prepregs were heat treated in an oven to make them the B-stage. Surface morphology of the prepreg was observed by using a scanning electron microscope (SEM). Tack property of the prepreg is one of the major properties that govern the ability of prepreg to be laid up. In this study, the tack of prepreg was measured under various test parameters by a probe tact test. Test parameters were contact time, contact force and debonding rate. Most of the tack properties of the prepreg increased with the test parameters. Then tack properties exhibited a linear behavior with test parameters before a saturation point. Also, the tack of prepreg was investigated in relation with the fibrillation phenomena involved in the prepreg surface with the debonding rate.

• Computational Structural Engineering
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• v.9 no.4
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• pp.181-187
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• 1996

This paper concerns the singular thermal stresses at the interface corner between the elastic fiber and the viscoelastic matrix of a two-dimensional unidirectional laminate model induced during cooling from cure temperature down to room temperature. Time-domain boundary element method is employed to investigate the nature of residual thermal stresses at the interface. Numerical results show that very large stress gradients are present at the interface corner and such stress singularity might lead to local yielding or fiber-matrix debonding.

• Computers and Concrete
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• v.20 no.3
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• pp.291-295
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• 2017

Tests on the fracture behavior of CFRP-concrete composite bonded interfaces have been extensively carried out. In this study, a progressive damage model is employed to simulate the fracture behaviors. The crack nucleation, propagation and more other details can be captured by these models. The numerical results indicate the fracture patterns seem to depend on the relative magnitudes of the interface cohesive strength and concrete tensile strength. The fracture pattern transits from the predominated adhesive-concrete interface debonding to the dominated concrete cohesive cracking as the interface cohesive strength changes from lower than concrete tensile strength to higher than that. The numerical results have an agreement with the experimental results.