• Journal of the Korean Wood Science and Technology
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• v.41 no.2
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• pp.141-148
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• 2013

The goal of this study was to find the optimum lamina size from red pine (Pinus densiflora) and Japanese cedar (Cryptomeria japonica) logs for the cross laminated timber (CLT) production. From visual inspection of the logs from two species, red pine log showed a larger knot and warp compared to the Japanese cedar. Different cross-sectional sizes of lamina ($110mm{\times}30mm$, $110mm{\times}40mm$, $110mm{\times}50mm$, $50mm{\times}30mm$, $30mm{\times}30mm$) from two species were analyzed for yield and grade. Regardless of the species, the optimized cross sectional size for maximizing the yield was $110mm{\times}30mm$. In grading for the different size laminas from Japanese cedar and red pine, a higher percentage of the first and second grade was found from the $110mm{\times}30mm$ lamina cut.

• Journal of the Korean Wood Science and Technology
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• v.50 no.3
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• pp.167-178
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• 2022

To investigate the influence of manufacturing environment on bonding performance of mixed cross laminated wood (CLT) using polyurethane (PUR) adhesive, a boiling water soak delamination test according to the temperature and relative humidity was conducted. The 5-ply mixed CLT consisted of Japanese Larch for external and middle layer and yellow poplar for internal layer. The PUR adhesives with different opening times of 10 and 30 minutes were used. The mixed CLT was manufactured according to pressing times of PUR and manufacturing environments of summer and winter. In case of summer environment, the delamination rate of the mixed CLT with pressing time of 4 hours using a PUR adhesive with open time of 10 minutes met the requirements of KS F 2081. In case of winter environment, the delamination rate of the mixed CLT didn't meet the requirements of KS standard. However, it was possible to confirm the effect of improving the adhesive performance by adjusting the pressing time according to the open time of the adhesive under the manufacturing conditions. The delamination rate of CLT with open time 30 minutes PUR, manufactured by indirect moisture supply methods was 11.2% better than direct moisture supply methods. As a result of delamination test in the same condition of relative humidity and adhesive, it was found that the temperature of manufacturing environment influences the adhesive performance.

• Journal of the Korean Wood Science and Technology
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• v.24 no.4
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• pp.32-39
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• 1996

The overall purpose of this study was to investigate the dimensional changes of melamine sheet laminated medium density fiberboard(MDF) floorings by sub-heating system(Ondol). This study was also conducted to improve the properties of melamine sheet laminated MDF floorings. The effects of density, resin content, manufacturing speed of MDF and types of melamine sheet on dimensional and weight changes of floorings were investigated. The results were as followings. 1. Dimensional and weight change of melamine sheet laminated MDF flooring by heating decreased with decreasing the density of MDF. 2. Dimensional and weight change of melamine sheet laminated MDF flooring by heating decreased with increasing the resin content of MDF. 3. Dimensional and weight change of melamine sheet laminated MDF flooring by heating decreased with decreasing the manufacturing speed of MDF. 4. Dimensional change of melamine sheet laminated MDF flooring in width direction by heating was doubled than that in machine direction. 5. Dimensional change and curling of high pressure melamine laminate(HPM) laminated MDF flooring by heating was less than those of low pressure melamine laminate(LPL) flooring. 6. Weight loss of melamine sheet laminated MDF flooring by heating has linear relationship with shrinkage.

• Journal of the Korean Wood Science and Technology
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• v.44 no.4
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• pp.607-615
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• 2016

The delamination along the annual ring on the cross-section of laminae and the bonding strength according to the tangential angle between laminae were evaluated for the production of 3-ply cross-laminated timber (CLT) using domestic larch. Since there is no standard for CLT in Korea, the production and test of specimens for bonding strength followed the standard procedure of "Structural glued laminated timber" (KS F 3021). The standard specifies to exclude any measurement from the cracks of timbers resulted from drying or knots during delamination test of the glued laminated timbers. However, the failure of cross-sectional tissues along the annual rings was observed near the glue-line of all specimens during the delamination test. Because this phenomenon can generate defects in the CLT that may be exposed to various temperatures and relative humidities after the actual construction, the delamination percentage was measured by including this wood failure. As a result, the delamination percentage of the CLT which had been combined in such a way that the annual rings of outer lamina were directed inward was the lowest, which was around 13%, regardless of the annual ring direction of the middle lamina. On the other hand, the delamination percentage of the CLT which had been combined in such a way that the annual rings of outer lamina were directed outward was the highest, which was around 26%. Furthermore, end-split occurred in the outer lamina during the drying process of the boiling delamination test, which affected the delamination percentage. Therefore, the soaking delamination test was found to be more appropriate for evaluating the delamination strength of CLT. The block shear strength of larch CLT was $3.9{\pm}0.9$ MPa on average, which was 46% lower than the block shear strength requirement (7.1 MPa) of the standard, but satisfied the criteria of the block shear strength (3.5 MPa) of the European Standard (prEN 16351: 2013).

• Journal of the Korea Furniture Society
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• v.20 no.1
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• pp.82-94
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• 2009

In this study, I suggest dyed-Glued laminated woods by using birch woods which are relatively cheaper than others. Since the dyed-Glued laminated woods which have the various colors to satisfy people's tastes and the dignified grains in the old woods enable us to product freely, these can provide us with stability of supply through replacing rare materials. The making wooden furniture designed with dyed-Glued laminated woods has these following characteristics. (1) This method which uses various colored woods can fulfill consumers' tastes through dyeing wooden plates, instead of using domestic woods which have limited colors-white, yellow and black. (2) Gathering wooden plates made by setting them into various frames enables us to get in large quantities of the materials with good grains, which we can only take from old woods. (3) Producing culture products using various colors and grains has enabled us to satisfy consumers and to create pro-environmental pieces. In conclusion, this study can be an alternative idea to forest resources which have been decreasing, and be an application method of using cheaper birch woods as well. Gathering and dyeing wooden plates might bring about the economic effect and be of much help to the expansion as furniture materials as well as interior ones.

• Journal of the Korean Wood Science and Technology
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• v.49 no.1
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• pp.93-102
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• 2021

In this article, withdrawal resistances of axially loaded self-tapping screws on wood products made by Korean Larch were predicted with existing estimation equation, and compared with experimental test data. The research was required because no design methodology for the withdrawal resistance of self-tapping screw is present in Korean building code (KBC). First, the withdrawal resistance of wood screw was predicted to use the withdrawal design value estimation equation in National Design Specification for Wood Construction (NDS). Second, three types of wood products, solid wood, cross-laminated timber (CLT) and plywood, were utilized for withdrawal test. For decades, various engineered wood products have been developed, especially cross-laminated timber (CLT) and hybrid timber composites such as timber composites of solid wood and plywood. Therefore, CLT and plywood were also investigated in this study as well as solid wood. Finally, the predicted values were compared with experimentally tested values. As the results, the tested values of solid wood and CLT were higher than the predicted values. In contrast, it is inaccurate to predict withdrawal resistance of plywood since prediction was higher than tested values.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.57-66
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• 2016

In order to develop materials with a low environmental load for restoring the destroyed forest, seven types of wood-concrete hybrid laminated materials were manufactured with four softwoods, three hardwoods and concrete, and the effect of wood density on bending creep property was investigated. The bending creep curves showed a shape to considerably increase at the upper right side, and the curves were found to show a linear behavior beyond about 30 min - 1 hour, as behaviors of solid woods and wood-based materials. The initial compliances of wood-concrete hybrid-laminated materials decreased with an increase in the wood density, and those values showed 0.9 - 1.2 times of the concrete one. The creep compliances of hybrid laminated materials showed very low values, which were 0.4 - 0.8 times of the concrete ones. The relative creep were very low with a range from 8.2% to 17.0% range, which were 0.3 - 0.7 times of the concrete ones. These results indicate that these materials can be applied for restoring the destroyed forest to reduce creep deformation of the conventional concrete materials by hybrid-laminating concrete and woods.

• Journal of the Korean Wood Science and Technology
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• v.43 no.1
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• pp.86-95
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• 2015

This study was performed to study physical and mechanical properties of hybrid cross laminated timber (HCLT) with plywood as core layer in order to improve its mechanical properties for wooden housing. MOE, MOR, and dimensional stability of the HCLT were determined, depending on plywood composition and lamination direction. MOR value of the HCLT was improved as much as that of the glued laminated timber, which was 59.6% stronger than that of the cross laminated timber (CLT) control group. All MOE values of the HCLT were similar to glued laminated timber structure control group regardless of plywood composition and lamination directions. The dimensional stability of the HCLT was better than those of the glued laminated timber and CLT control group, owing to the use of plywood in the core.

• Journal of the Korean Wood Science and Technology
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• v.45 no.6
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• pp.846-856
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• 2017

The aim of this study was to develop the details of cross-laminated timber (CLT) envelops for satisfying the design standard for energy saving (DSEA) and passive standard in South Korea. When the same thickness of 180 mm concrete or CLT was used and the same materials for other layers were used for the roof, wall, and interlayer floor, the required insulation thickness for the different building envelopes in central, southern, and Jeju island was evaluated. As a result, compared to the concrete envelop, about 43 mm of insulation thickness was reduced for wall and roof with the CLT envelope. When the CLT envelopes were modified to protect the CLT from moisture based on FPInnovations (2011), the insulation thickness was further reduced by 12 mm. When the modified CLT building envelops satisfied with a passive standard are used for 10-story building, the required insulation was decreased by $40.89m^3$ for a floor ($105.27m^2{\times}2.3m$ in height) compared to concrete building. As the number of floors increases, about 3.58 m3 of insulation per floor was additionally saved.

• Journal of the Korean Wood Science and Technology
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• v.18 no.4
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• pp.9-17
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• 1990

When manufacturing beam by laminating particleboards, the mechanical properties of particleboad-laminated beam would be also improved if the properties, especially mechanical properties of particleboad be reinforced. In this study, steel wires were used to reinforce particleboard. This study was carried out to obtain the basic mechanical properties of the board composed of wood particle and steel wires, focusing on bending strength which is the important factors in laminated beam and it was tried to estimate the relationship between the properties of the particleboard-laminated beam. and the proportion of steel wires to wood particles in particleboards. The result obtained can be summarized as follows: 1. The more steel wires used in boards, the higher value of modulus of rupture in bending was obtained, For example. the density 5 board composed of 14 numbers of steel wires showing 55% improved value than control board. 2. The board with lower density was also made better in higher value of elasticity, the density 0.5 board with 14 numbers of steel wires improved by 170%, the density 0.6 board by 86%, the 0.7 board by 37% and the 0.8 board by 26%. 3. The work to maximum load was improved with more steel wires. for example, the density 0.8 board with 14 numbers of steel wires improved by 31%.