• Geomechanics and Engineering
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• v.28 no.4
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• pp.375-384
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• 2022

The glacial tills and shales in Midwestern states of the USA often show strength degradation after construction. They are often in need of applying soil modification techniques to remediate their strength degradation with weathering process. This study investigated the weathering durability of these natural soils and biopolymer treated soils by comparing direct shear test results for wet-dry and wet-freeze-thaw-dry cycled specimens. The tests showed that untreated glacial tills maintained only 62% and 50% initial shear strength after eight wet-dry cycles and eight wet-freeze-thaw-dry cycles, respectively. These untreated soils could not withstand by themselves after 16 weathering cycles. The same soils treated with 1.5% (by dry weight) food-grade Xanthan gum maintained 140% and 88% initial shear strength of untreated soils after 16 weathering cycles for wet-dry cycles and wet-freeze-thaw-dry cycles, respectively. The same soils treated with 1.5% (by dry weight) Gellan gum maintained 82% and 60% initial shear strength of untreated ones after 16 weathering cycles, respectively. Similar results were obtained for crushed shales, manifesting that the biopolymerization method may be adopted as a new eco-friendly method to enhance the weathering durability of these problematic soils of glacial tills and shales.

• Journal of the Korean Wood Science and Technology
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• v.12 no.2
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• pp.35-43
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• 1984

This study was carried out to investigate the block shear strength of the 2ply laminated wood composed of Pinus thunbergii with ureaformaldehyde resin as adhesives according to pressure (6, 9, 12, 15kg/$cm^2$), pressing time(5, 10, 20, 30 hrs.), amount of spread(54, 108, 217, 324g/$cm^2$), hardener(10, 20, 30, 40% of 10% $NH_4CL$ on resin) and extender(0, 5, 10, 15% wheat flour on resin), and the bending strength and bending young's modulus of laminated beam according to the number of ply. The results were summarized as follows; 1. According to pressing pressure with amount of spread 217g/$cm^2$ both dry and wet shear strength of laminated wood showed the highest in 15kg/$cm^2$, and hot-cold soaking treatment showed the highest in 9kg/$cm^2$, while all shear strength of dry, wet and hot-cold soaked laminated wood have been reduced with the increasing of pressing time. 2. According to amount of spread, adhesion strength with the dry, wet and hot-cold soaking treatments revealed the highest in 217g/$cm^2$ and have been reduced under or over 217g/$cm^2$ of spread. 3. According to addition of hardener and extender, all shear strength of laminated block with the dry, wet and hot-cold soaking treatments have been reduced in increasing of addition amount of hardener and extender. The bending strength of beam according to the number of ply showed the highest in 2ply laminated wood and horizontal loading beam to glue line had the higher in strength than the vertical loading.

• Journal of the Korean Wood Science and Technology
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• v.38 no.5
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• pp.414-420
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• 2010

The effect of polymeric diphenyl methane-4,4-diisocyanate (pMDI) or 1,6-hexamethylene diisocyanate (HDI) in the UMF resin was discussed for improvement of the dry and wet shear strengths of plywood manufactured from high moisture content veneers. The curing behavior of UMF resin by pMDI or HDI content was examined by DSC and TGA, and its adhesion performance was evaluated by dry and wet shear strength tests of plywood. With the increase of pMDI content in the UMF resin, the curing temperature, reaction enthalpy (${\Delta}H$), and thermal stability consistently increased. With the increase of HDI content in the UMF resin, however, the curing temperature and reaction enthalpy (${\Delta}H$) decreased consistently and the thermal stability slightly increased in the range of 200 to $400^{\circ}C$ but decreased beyond $400^{\circ}C$. Also, the dry tensile shear strength increased up to the pMDI content of 5% and then decreased with its further addition but the wet tensile shear strength showed slight tendency to increase with the increase of pMDI content in the UMF resin. As the HDI content increased, however, the dry and wet tensile shear strengths of plywood consistently increased.

• Journal of the Korean Wood Science and Technology
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• v.1 no.2
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• pp.11-15
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• 1973

This study was carried out to utilize sweet potato, and jerusalem artichoke flour as an extender of urea formaldehyde resin for plywood manufacture. The results obtained are summarized as follows: 1) In dry and wet test of plywood, sweet potato flour extended in urea formaldehyde resin was shown better strength than those of wheat flour. 2) Sweet potato flour was shown good results up to 200 percent extension in the dry test, and there was not shown significant difference between 100 percent and 150 percent extension in the wet test. 3) In the case of 100 percent extension, potato flour was shown best dry shear strength(400 psi) and sweet potato flour was shown best wet shear strength (212 psi).

• Composites Research
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• v.33 no.5
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• pp.275-281
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• 2020

The mechanical property related to lap shear strength of the joint structure between carbon fiber reinforced polymer (CFRP) composite and metal (Ni-Cr Alloy) under varying environmental conditions (temperature and humidity) was studied in order to apply to the aircraft fan blade. Room temperature dry (RTD), elevated temperature wet (ETW), and cold temperature dry (CTD) environmental conditions were chosen for investigation based on the flight conditions of aircraft. Lap shear strength tests were conducted according to ASTM Standard D3528 to evaluate the shear strength. The microstructure characteristic of failure zone was analyzed by SEM images to check the adhesive shear strength with the three environmental conditions. In comparison with shear strength for the RTD condition, the shear strength in the ETW condition was reduced by 72.8% while those for the CTD condition increased by 56.5%. The moisture absorption and high temperature in ETW condition strongly had an affect on mechanical property of adhesive, while cold temperature could enhance the adhesive shear strength due to the higher brittleness.

• Journal of the Korean Wood Science and Technology
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• v.4 no.1
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• pp.38-47
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• 1976

This study was carried out to exploit and utilize American sycamore (Platanus occidentalis) and poplar grown in Korea as veneer species for plywood manufacture. At this study to save the imported lauan logs and dollars, the effects affecting to the properties of plywood constructed by sycamore, poplar and lauan veneers were studied. Important items dealt with this study were dry and wet shear strength, moisture content, and specific gravities By the results and discussion it may be summarized as followings. 1) Sycamore core lauan plywood (A-II type) was shown best dry shear strength, and the next were all lauan veneer plywood (A-I type), poplar core lauan plywood (B-I type), lauan core sycamore plywood (A-III type) in order. There are no differences between dry shear strength of A-II type and A-I type, A-II type and B-I type plywood. 2) Wet shear strength showed the same order with dry shear strength. A-II type plywood showed best wet shear strength and it showed more difference than other plwoods. A-I type, B-I type and A-III type plywood were all very good without significant difference in wet shear strength. 3) B-I type plywood showed highest moisture content of all type plywood and the next were all sycamore(A-IV type) all poplar plywood (B-III type), A-III type, B-II type, A-II type pllywood in order. Generally high moisture content showed when two or three veneers were same species in the three layer plywood. 4) A-III type plywood showed highest specific gravity of all and the next was A-IV type plywood without a difference to A-I type plywood on the whole. plywoods constructed by lauan and sycamore were shown high specific gravities and the next was lauan, sycamore and poplar, lauan and poplar. It seemed to be that connected wi th the specific gravity of veneer itself in different species. 5) The plywood manufactured by extension of potato flour is not only superior but also profitable in the price aspect than the plywood manufactured by extension of wheat flour.

• Journal of the Korean Wood Science and Technology
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• v.4 no.1
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• pp.28-32
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• 1976

This study was carried out to know the adaptability of barley flour, potato flour and white ash as extender and filler of urea-formaldehyde resin for plywood as a substitute material of wheat flour. The extenders and filler used at this study were extended by several groups of percentages. Shear strength, moisture contents, and specific gravities were compared among tested groups. The results obtained are summarized as follows. 1) Wet and dry shear strength of plywoods extended by 10% barley flour, 30% potato flour, and wheat flours were shown better results than non extended plywoods. 2) There was no significant difference between plywoods extended until 50% barley flours and non extended plywoods. 3) Shear strength of plywoods extended by 50% potato and 100% barley flours were shown worse result than non extended. 4) Dry and wet shear strength of plywoods extended by white ash were shown worst result. 5) The plywoods extended by potato flours were shown not only better shear strength, but also considered more profitable cost for extending.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.69-84
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• 2017

This paper presents results of an experimental investigation on the behaviour of bond between external glass fibre reinforced polymer reinforcement and concrete exposed to three different environmental conditions, namely, temperature cycles, wet-dry cycles and outdoor environment separately for extended durations. Single shear tests (pull-out test) were conducted to investigate bond strengths (pull-out strengths) of control (unexposed) and exposed specimens. Effect of the exposure conditions on the compressive strength of concrete were also investigated separately to understand the effect of changing concrete compressive strength on the pull-out strength. Based on the comparison of experimental results of exposed specimens to control specimens in terms of bond strengths, failure modes and strain profiles, the most significant degradation of pull-out strength was observed in specimens exposed to outdoor environment, whereas temperature cycles did not cause any deterioration of strength.

• Journal of Korean Society of Forest Science
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• v.57 no.1
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• pp.32-38
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• 1982

This study was carried out to examine the possibility to replace imported wheat flour with taro. Taro and wheat flour were used for the extenders after oven drying($100{\pm}3^{\circ}C$)and pulverized into 80-100mesh minute powder by laboratory willey mill. Urea- and phenol-formaldehyde resin adhesives were used for plywood manufacture, and the extending materials mixed with the extension at the ratio of 10, 20, 30, and 50% to each resin solution. The results obtained at this study were summarized as follows; 1) In dry and wet shear strength of urea-formaldehyde resin adhesive, taro showed very excellent bonding strength compared with wheat flour in all extending ratio. Therefore taro showed the possibility that be usable to taro in place of wheat flour. 2) In dry and wet shear strength of phenol-formaldehyde resin adhesive, in general, wheat flour showed higher bonding strength than taro. But in dry shear strength, taro showed higher shear strength than wheat flour in 30 and 50% extension.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.813-816
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• 2004

This study was performed to investigate bonding performance of epoxy resins for repairing of cracks in concrete, as a part of project to establish quality control standard for epoxy resins. In the slant shear strength test for hard and soft type epoxy, hard type was higher about 3 times than soft one. From the results, it is thought that hard type is suitable for load carrying. Injection of epoxy resin in the notch made flexural strength increase about $47\%$ over the specimen that epoxy resin is not injected. There were no differences in bonding performances with viscosity. Application of epoxy resin on the wet concrete surface made slant shear strength decrease about $46\%$, but similar performance to the case of application on the dry surface appeared by using epoxy resin for wet condition.