• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.609-616
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• 2010

FRP-concrete composite deck, an innovative system, is composed of concrete in the top and FRP panel in the bottom. Bottom FRP panel can reduce self weight and improve workability. This system requires strong connection between FRP and concrete. Therefore coarse sand coating was previously applied on FRP to improve the bonding. In this study, concrete wedge method is newly introduced to enhance both vertical bond and fatigue performance. Three FRP-concrete composite deck specimens with the concrete wedges were manufactured, and static and fatigue tests were carried out. The results showed that the new FRP-concrete composite deck satisfied deflection and crack width limits set by the design codes. And the fatigue test showed that the composite deck was capable of two million load cycles under 50% of its static strength. Based on the results, it can be concluded that that this new system has outstanding mechanical and durability performance, and therefore, satisfactorily be used in designing FRP-concrete composite deck.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.10
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• pp.928-935
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• 2015

This paper presents low temperature structural tests of a UAV wing which has room temperature-curing adhesive bond. The wing structure is made of carbon fiber reinforced composites, and the skins are bonded to the inner structures (such as ribs and spars) using room temperature-curing adhesive bond. Also, to verify damage tolerance design of the wing structure, barely visible impact damages are intentionally created in the critical areas. The attachment fittings of the wing are fixed in a specially designed chamber which can simulate the low temperature environments of the operating altitudes. The test load is applied by hydraulic actuators which are placed outside the chamber. The structural tests consist of strain survey tests and a durability test for 1-life fatigue load spectrum. During the tests, strains of major parts are measured by strain gauges and FBG sensors. The change of the initial impact damages is also monitored using piezoelectric sensors. The 1-life damage tolerance of the composite structure is verified by the structural tests under the simulated environments.

• Journal of the Korean Wood Science and Technology
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• v.37 no.3
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• pp.184-191
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• 2009

In the southern part of the Korean Peninsula including Jeju-island, the production amount of domestic cedar has increased gradually. However, their low qualities, expected to be caused by the low density and frequent knots, have restricted their practical utilization as the high value-added products. In this study, it is aimed to look for the new uses of domestic cedar and to examine the applicability for lamination lumbers of structural glued laminated timber (glulam). Above all, machine stress ratings for individual sawn lumbers confirmed that modulus of elasticity (MOE) of cedar lumber was lower than that of other common softwood species in Korea. On the other hand, cedar lumbers have enough stiffness to manufacture the structural glulam in accordance with Korean Industrial Standard (KS). The bonding strength and durability also met the KS limitation. Nevertheless, from the result of bending tests for cedar glulam, it was shown that the modulus of elasticity (MOE) did not meet the KS limitation. Therefore, it was concluded that additional researches were needed for reinforcing the stiffness of cedar glulam.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.489-498
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• 2005

Recently, the deterioration of concrete structures have been increased by the damage from salt, carbonization, freezing & thawing and the others. Therefore, the measures for the deterioration of concretes have been taken. Among them, it has been often used that surface treatment which cut off the deterioration factors of durability by protecting the surface of concrete. The water proof and repair materials for concrete mainly use organic materials such as epoxy, these materials excel in intial bonding force and resistance to chemical agents. But they cause difference in the modulus of elasticity and the rate of shrinkage and expansion of concrete, and thus result in such problems as scaling and spatting in the progress of time. Therefore in this study it develop the performance Improving agent of concrete surface that can block a deterioration cause such as $CO_2$ gas, chloride ion and water from the outside and enhance waterproofing ability by reinforcing the concrete surface when applying it to concrete structures.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.613-620
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• 2005

There are some problems in utilizing recycled concrete aggregate go structural use because of the difficulties concerning about quality control and durability. It seems to be possible to utilize recycled concrete aggregate for making concrete products because quality control of concrete products is easier than ready-mixed concrete, but there are little studies about the properties of the steam-cured recycled aggregate concrete. In this study, various tests were performed such as compressive strength, flexural strength, splitting tensile strength, bonding strength and chloride ion penetration test to evaluate the effect of substitution of recycled concrete aggregate. The results of strength test showed that the concrete strength decreased with the increase of the substitution ratio of recycled concrete aggregate, but it was in the reasonable range and almost equal to that of normal concrete below the substitution ratio of $50\%$. On the other hand, strength test of furnace slag cement concrete shows that the strength of recycled concrete with furnace slag cement under curing condition lower than that of recycled concrete with ordinary portland cement under same condition. From the result of this study, it can be concluded that recycled concrete aggregate is able to be utilized for structural use but substitution ratio should be decided with care in each case. The result of this study could be used as the basic data for the structural use of recycled concrete aggregate.

• Clean Technology
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• v.28 no.1
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• pp.24-31
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• 2022

Petroleum-based plastics are used for various purposes and pose a significant threat to the earth's environment and ecosystem. Many efforts have been taken globally in different areas to find alternatives. As part of these efforts, this study manufactured alginate-based polyvinyl alcohol (PVA) blended films by casting from an aqueous solution prepared by mixing 10 wt% petroleum-based PVA with biodegradable, marine biomass-derived alginate. Glutaraldehyde was used as a cross-linking agent, and cardanol, an alkyl phenol-based bio-oil extracted from cashew nut shell, was added in the range of 0.1 to 2.0 wt% to grant antibacterial activity to the films. FTIR and TGA were performed to characterize the manufactured blended films, and the tensile strength, degree of swelling, and antibacterial activity were measured. Results obtained from the FTIR, TGA, and tensile strength test showed that alginate, the main component, was well distributed in the PVA by forming a matrix phase. The brittleness of alginate, a known weakness as a single component, and the low thermal durability of PVA were improved by cross-linking and hydrogen bonding of the functional groups between alginate and PVA. Addition of cardanol to the alginate-based PVA blend significantly improved the antibacterial activity against S. aureus and E. coli. The antibacterial performance was excellent with a death rate of 98% or higher for S. aureus and about 70% for E. coli at a contact time of 60 minutes. The optimal antibacterial activity of the alginate-PVA blended films was found with a cardanol content range between 0.1 to 0.5 wt%. These results show that cardanol-containing alginate-PVA blended films are suitable for use as various antibacterial materials, including as food packaging.