• Steel and Composite Structures
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• v.19 no.5
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• pp.1221-1236
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• 2015

Since the coefficients of thermal expansion (CTE) between concrete and GFRP, steel and GFRP are quite different, GFRP laminates with different laminas stacking-sequence present different thermal behavior and currently there is no specification on mechanical properties of GFRP laminates, it is necessary to investigate the thermal influence on composite girder with stay-in-place (SIP) bridge deck at different levels and on different scales. This paper experimentally and theoretically investigated the CTE of GFRP at lamina's and laminate's level on micro-mechanics scales. The theoretical CTE values of laminas and laminates agreed well with test results, indicating that designers could obtain thermal properties of GFRP laminates with different lamina stacking-sequence through micro-mechanics methods. On the basis of the CTE tests and theoretical analysis, the thermal behaviors of composite girder with hybrid GFRP-concrete deck were studied numerically and theoretically on macro-mechanics scales. The theoretical results of concrete and steel components of composite girder agreed well with FE results, but the theoretical results of GFRP profiles were slightly larger than FE and tended to be conservative at a safety level.

• Journal of the Korean Society of Safety
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• v.11 no.3
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• pp.154-159
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• 1996

In this thesis, a series of loading tests are conducted in order to investigate the fracture safety of GFRP(Glass Fiber Reinforced Plastics) pipes under fatigue load which are widely used in the developed countries becauses of their natural of anticorrosion and lightweight etc. . Fatigue test is performed by changing number of laminates and loading cycles to examine the flexural strains, the ductility and the fatigue strength for two million repeated loading cycles. From the fatigue test results, it was found that the larger the laminates of GFRP pipes is, the larger the stiffness of GFRP pipes under the fatigue load increases. This phenomenon is true until the fatigue failure. According to the S-N curve drawn by the regression analysis on the fatigue test results, the fatigue strength of percent of the static ultimate strength increases by increasing the laminates of GFRP pipes. The fatigue strength with two million repeated leading cycles in GFRP pipes with the laminates of GFRP pipes varing 15, 25, 35 shows about 75%, 80%, 84% on the static ultimate strength, respectively.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.225-230
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• 2003

Domestic small and medium ship companies have lack of leisure boat technologies and especially they have a problem about its low performance because of the overweight of boat hull. So it is necessary to have alternative manufacturing process to improve the mechanical properties of composite material. In this study, a vacuum curing system was developed as an alternative manufacturing process and then changed the fiber volume fractions of GFRP laminates. The properties of GFRP laminates such as void contents, Young's modulus and fracture toughness were determined for various fiber volume fractions.

• Computers and Concrete
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• v.19 no.1
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• pp.79-85
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• 2017

This paper summarizes the experimental study of the shear behaviour of Hybrid Fibre Reinforced Concrete (HFRC) beams retrofitted by using externally bonded Glass Fibre Reinforced Polymer (GFRP) laminates. To attain the set-out objectives of the present investigation, steel fibre of 1% and polypropylene fibre of 0.30% was used for hybrid steel-polypropylene fibre reinforced concrete: whereas for hybrid glass-polypropylene fibre reinforced concrete, glass fibre by 0.03% and polypropylene fibre of 0.03% by volume of concrete was used. In this study, 9 numbers of beams were cast and tested into three groups (Group I, II & III). Each group containing 3 numbers of beams, out of which one serve as a control beam or a hybrid steel-polypropylene fibre reinforced concrete beam or a hybrid glass - polypropylene fibre reinforced concrete beam and the remaining two beams were preloaded until shear cracks appeared up to 75% of ultimate load and then preloaded beams (damaged beams) were retrofitted with GFRP laminates at shear zone in the form of strips, as one beam in vertical position and another beam in inclined position to restrict the shear cracks. Finally, the retrofitted beams were loaded until failure and test results were compared. The experimental tests have been conducted to investigate various parameters of structural performance, such as load carrying capacity, crack pattern and failure modes, load-deflection responses and ductility relations. The test results revealed that beams retrofitted using GFRP laminates considerably increased the load carrying capacity. In addition, it was found that beams retrofitted with inclined strip offers superior performance than vertical one. Comparing the test results, it was observed that hybrid steel-polypropylene fibre reinforced concrete beam retrofitted with GFRP laminates showed enhanced behaviour as compared to other tested beams.

• Steel and Composite Structures
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• v.17 no.3
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• pp.271-285
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• 2014

This paper aims to examine the behavior of slender reinforced concrete columns confined with external glass fiber reinforced polymers (GFRP) sheets under eccentric loads. The experimental work conducted in this paper is an extension to previous work by the author concerning the behavior of eccentrically loaded short columns strengthened with GFRP wrapping. In this study, nine reinforced concrete columns divided into three groups were casted and tested. Three eccentricity ratios corresponding to e/t = 0, 0.10, and 0.50 in one direction of the column were tested in each group. The first group was the control one without confinement with slenderness ratio equal 20. The second group was the same as the first group but fully wrapped with one layer of GFRP laminates. The third group was also fully wrapped with one layer of GFRP laminates but having slenderness ratio equal 15. The experimental results of another two groups from the previous work were used in this study to investigate the difference between short and slender columns. The first was control one with slenderness ratio equal 10 and the second was fully wrapped and having the same slenderness ratio. All specimens were loaded until failure. The ultimate load, axial deformation, strain in steel bars, and failure mechanisms of each specimen were generated and analyzed. The results show that GFRP laminates confining system is less effective with slender columns compared with short one, but this solution is still applied and it can be efficiently utilized especially for slender columns with low eccentric ratio.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.219-226
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• 1994

In the comparison result of residual strain calculated from the load-strain curve under the repeated loading cycles, it was found that the larger the laminates is, the larger the stiffness of GFRP pipes under fatigue load is. This phenomenon is true until the fatigue failure. According to the S-N curves drawn by the regression analysis on the fatigue test results, the fatigue strength for percentage of the static ultimate strength increases by increasing the laminates of GFRP pipes. The fatigue strength for 2, 000, 000 repeated loading cycles In GFRP pipes with the laminates varing 15, 25, 35 shows 75.2%, 79.5%, 84.2% on the static ultimate strength, respectively.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.150-153
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• 2003

Longitudinal strains({$varepsilon}_x$) of the core and skin layers in glass fiber reinforced plastic(GFRP) cross-ply composite laminates have been studied using the embedded optical fiber sensor of totally-reflected extrinsic Fabry-Perot interferometer(TR-EFPI). Foil-type strain gauges bonded on both the upper and lower surfaces were used for the measurement of the surface strains. Both TR-EFPI sensor and strain gauge bonded on the specimen surface showed excellent agreement within -0.0086 ~ +0.0302% strain. It was shown that values of {$varepsilon}_x$ in the interior of the surface layer and the core layer measured by embedded TR-EFPI sensor was significantly higher than that of the specimen surface measured by strain gauges. The experimental results were ascertained with finite element analysis. Embedded TR-EFPI optical fiber sensor could measure accurately the internal strains which were different from the surface.

• Structural Engineering and Mechanics
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• v.39 no.2
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• pp.207-221
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• 2011

This paper aims to study the behavior of short reinforced concrete columns confined with external glass Fiber Reinforced Polymers (GFRP) sheets under eccentric loads. The experimental part of the study was achieved by testing 9 specimens under eccentric compression. Three eccentricity ratios corresponding to e/t = 0, 0.10, 0.50 in one direction of the column were used. Specimens were divided into three groups. The first group was the control one without confinement. The second group was fully wrapped with GFRP laminates before loading. The third group was wrapped under loading after reaching 75% of failure loads of the control specimens. The third group was investigated in order to represent the practical case of strengthening a loaded column with FRP laminates. All specimens were loaded until failure. The results show that GFRP laminates enhances both failure load and ductility response of eccentrically loaded column. Moreover, the study also illustrates the effect of confinement on the first crack load, lateral deformation, strain in reinforcement and failure pattern. Based on the analysis of the experimental results, a simple model has been proposed to predict the improvement of load carrying capacity under different eccentricity ratios. The predicted equation takes into consideration the eccentricity to cross section depth ratio, the ultimate strength of GFRP, the thickness of wrapping laminate, and the time of wrapping (before loading and under loading). A good correlation was obtained between experimental and analytical results.

• Journal of the Korean Society of Safety
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• v.28 no.4
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• pp.14-18
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• 2013

Blades of horizontal axis are nowadays made of composite materials. Generally, composite materials satisfy design provides lower weight and good stiffness, while laminate composites have often damages as like the delamination and cracks at the interface of laminates. The box spar and tail parts of a blade are composed of the CFRP/GFRP hybrid laminate composites. However, delamination and the interfacial crack often occur in the interface of CFRP/GFRP hybrid laminate composites under the mixed mode fracture condition, especially mode I and mode II. Therefore, there is a need for the evaluation of the mixed mode fracture behavior during the delamination of CFRP/GFRP hybrid laminates. This study shows the experimental results for the delamination fracture toughness in CFRP/GFRP hybrid laminate composites. Fracture toughness experiments and estimation are performed by using DMMB(Dissimilar mixed mode bending) specimen. The materials used in the test are a commercial woven type CFRP(Carbon fiber reinforced plastic) prepreg(CF3327) and UD type GFRP(Glass fiber reinforced plastic) prepreg(HD224A). A CFRP/GFRP hybrid laminate composite is composed by the 10 plies CFRP and GFRP prepreg for DMMB. A thickness of CFRP and GFRP layer is 2.5mm and 3.0mm, respectively. Also the fulcrum location which is a loading parameter is changed from 80 to 100mm on the specimen of length 120mm because it defines the ratio of mode I to mode II. In this study, the effects of the fulcrum location are evaluated in the viewpoint of energy release rate in mode I and mode II contribution. The results show that the delamination crack initiates at higher displacement and lower load according to the increase of the fulcrum location ratio. And the variation of the energy release rate for mode I and II contributions for the mode mixity are shown.

• Journal of Mechanical Science and Technology
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• v.18 no.11
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• pp.1932-1940
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• 2004

Although the previous researches evaluated the fatigue behavior of Al/GFRP laminates using the traditional fracture mechanism, their researches were not sufficient to do it : the damage zone of Al/GFRP laminates was occurred at the delamination zone instead of the crack-metallic damages. Thus, previous researches were not applicable to the fatigue behavior of Al/GFRP laminates. The major purpose of this study was to evaluate delamination behavior using the relationship between crack length (a) and delamination width (b) in Al/GFRP laminate. The details of investigation were as follows: 1) Relationship between the crack length (a) and the delamination width (b), 2) Relationship between the delamination aspect ratio (b/a) and the delamination area rate ((A$\_$D/)/subN// (A$\_$D/)$\_$All/), 3) The effect of delamination aspect ratio (b/a) on the delamination shape factor (f$\_$s/) and the delamination growth rate (dA$\_$D// da). As results, it was known that the delamination aspect ratio (b/a) was decreased and the delamination area rate ((A$\_$D/)$\_$N// (A$\_$D/)$\_$All/) was increased as the normalized crack size (a/W) was increased. And, the delamination shape factors (f$\_$s/) of the ellipse-II(f$\_$s3/) was greater than of the ellipse-I(f$\_$s2/) but that of the triangle (f$\_$s1/) was less than of the ellipse-I(f$\_$s2/).