• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.742-745
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• 2004

The FRP-concrete composite deck system has advantages of corrosion free and easy construction. The system is, however, comprised of two brittle materials, so that it suffers from inherent disadvantage of lack of ductility. In this study, some conceptual design is presented for preventing the brittle failure of FRP-concrete composite deck at ultimate load level. 4-point bending tests are performed for FRP-concrete composite beams using FRC(Fiber Reinforced Concrete). The specimens use the box-shape FRP member in the lower portion. Four types of concrete with different compressive strengths and ductilities including normal mortar and 3 FRCs are placed in the upper portion. Typical failure mode in the test is identified; Concrete compressive failure occurs first at the maximum moment region, and the interfacial debonding between FRP and concrete member proceeds. Finally, the tensile rupture of FRP member occurs. The specimen using FRC with the high compressive ductility of concrete fails with less brittle manner than other specimens. The reason is that the ductility from the concrete in compression prevents the sudden loss of load-carrying capacity after compressive concrete failure.

• Steel and Composite Structures
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• v.25 no.1
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• pp.35-43
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• 2017

This paper presents the findings of experimental and numerical investigations on failure analysis and structural behavior of notched steel I-beams reinforced by bonded Carbon Fiber Reinforced Polymer (CFRP) plates under static load. To find solutions for preventing or delaying the failures, understanding the CFRP failure modes is beneficial. One non-strengthened control beam and four specimens with different deficiencies (one side and two sides) on flexural flanges in both experimental test and simulation were studied. Two additional notched beams were investigated just numerically. In the experimental test, four-point bending method with static gradual loading was employed. To simulate the specimens, ABAQUS software in full three dimensional (3D) case and non-linear analysis method was applied. The results show that the CFRP failure modes in strengthening of deficient steel I-beams include end-debonding, below point load debonding, splitting and delamination. Strengthening schedule is important to the occurrences and sequences of CFRP failure modes. Additionally, application of CFRP plates in the deficiency region prevents crack propagation and brittle failure.

• Structural Monitoring and Maintenance
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• v.1 no.1
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• pp.111-130
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• 2014

The increased use of carbon fiber reinforced polymer (CFRP) in retrofitting reinforced concrete (RC) members has led to the need to develop non-destructive techniques that can monitor and characterize the unique damage mechanisms exhibited by such structural systems. This paper presented the damage characterization results of six CFRP retrofitted RC beam specimens tested in the laboratory and monitored using acoustic emission (AE). The focus of this study was to continuously monitor the change in AE parameters and analyze them both qualitatively and quantitatively, when brittle failure modes such as debonding occur in these beams. Although deterioration of structural integrity was traceable and can be quantified by monitoring the AE data, individual failure mode characteristics could not be identified due to the complexity of the system failure modes. In all, AE was an effective non-destructive monitoring tool that can trace the failure progression in RC beams retrofitted with CFRP. It would be advantageous to isolate signals originating from the CFRP and concrete, leading to a more clear understanding of the progression of the brittle damage mechanism involved in such a structural system. For practical applications, future studies should focus on spectral analysis of AE data from broadband sensors and automated pattern recognition tools to classify and better correlate AE parameters to failure modes observed.

• Journal of Mechanical Science and Technology
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• v.15 no.6
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• pp.727-734
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• 2001

The Tribological evaluation of commercial dental composite resins containing prepolymerized particle fillers was investigated. Composite resins such as Metafil, Silux Plus, Heliomolar, and Palfique Estelite were selected as specimens. In the wear tests, a ball-on-flat wear test method was used. The friction coefficient of Metafil was quite high. The wear resistance of Silux Plus and Palfique Estelite was better than that of Metafil and Heliomolar under the same experimental conditions. The main wear mechanism of the composite resins containing prepolymerized particle fillers was abrasive wear caused by the brittle fracture of the prepolymerized particles and the debonding of the filler and the matrix.

• Journal of the Korean Ceramic Society
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• v.30 no.6
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• pp.457-468
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• 1993

In oxide matrix-SiC(W) composites, instability and glassy phase formation due to oxidation at the high temperature and the diffusion of Si, respectively, cause brittle fracture and low reliability for ceramic materials. The mode of contribution in each mechanisms induced by matrix-whisker debonding, varies with the morphology of matrix-whisker interfaces. This work has described the dispersion behaviours and stabilization mechanisms in slip systems, and multiple toughening mechanisms by dint of two second phase different from each other when spherical ZrO2 and chemically stable Al2O3(W) is respectively added in Al2O3 matrix. To obtain complexshaped components, slip casted bodies were sintered at 1$600^{\circ}C$, 2hrs up to 98~99% R.D.. Multiple toughening mechanisms in comparison with theories reported until now will be discussed as a result of the phase analysis of ZrO2 by athermal behaviours and microstructural characterizations as well as measured mechanical properties.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2078-2086
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• 1999

Fracture behaviors of an interface crack in a ductile layer sandwiched by rigid substrates are analyzed by finite element method. Several fracture mechanisms and the corresponding criteria are examined. And the crack growth behavior and fracture toughness are predicted. As the results, various crack growth procedures such as the crack jump to the other interface on the opposite side, the creation of a new crack far from the initial crack front, and the asymmetric relation of fracture toughness vs. mode mixity ($J_c$-$\Phi$) can be successfully explained.

• 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.

• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.94-98
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• 2001

fatigue life and nondestructive evaluation were examined experimentally using surface crack specimen and compact tension specimen of 5083 aluminium alloy. Acoustic emission signals emanated during failure of aluminum alloys has been the subject of numerous investigations. Possible sources of AE during deformation have been suggested as the dislocations, fracture of brittle particles and debonding of these particles from the alloy matrix. Fatigue life and penetration behavior of long surface crack can be evaluated quantitatively using K values proposed by authors. The influence of stress ratio on the frequency characteristics of AE signals were investigated.

• Journal of the Society of Disaster Information
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• v.13 no.1
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• pp.81-88
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• 2017

In this paper, the behaviour of composite steel-CFRP members is studied experimentally and using FE-analysis. The use of advance composite materials in construction for repair and rehabilitation has become a frequent used method in the last decade. FRP composites have many advantages over the traditional technique of steel bonding for a number of reasons: 1. Composites add little or no additional weight to a building, eliminating the need for costly foundation strengthening. 2. FRP composites are very thin (1.2mm to 1.4mm). So there is no loss of floor space and negligible effect over the architectural aspect. 3. FRP composites do not corrode, this makes it long lasting. However, the method is yet to become a mainstream application due to a number of economical and design related issues. Brittle debonding failure, aging effect on bonding, broad based awareness and proper design guidelines are the main concern for future research works. This paper is focused on the ultimate load carrying capacity of the CFRP-strengthened beams and their effect on the deflection and failures modes by varying the amount of CFRP content.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.171-180
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• 2008

The aim of this paper is to clarify the structural performance of RC beams strengthened with Carbon Fibre Reinforced Polymer(CFRP) plates using channel-type anchorage system. Twelve RC beams were specifically designed without and with a channel-type anchorage system, which was carefully detailed to enhance the benefits of the strengthening plates. All the twelve beams were identical in terms of their geometry but varied in their internal reinforcement, concrete strength. All the beams were tested under four point bending and extensively instrumented to monitor strains, cracking, load capacity and failure modes. The structural response of all the twelve beams is then critically analyzed in terms of deformability, strength and failure processes. It is shown that with a channel-type anchorage system, a brittle debonding failure of a strengthened beam can be transformed to an almost ductile failure with well-defined enhancement of structural performance in terms of both deformation and strength.