• Journal of the Korean Wood Science and Technology
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• 제48권5호
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• pp.722-731
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• 2020

The purpose of this research is to determine the efficiency of impregnation using phenol formaldehyde resin to enhance Falcataria wood's stability and better mechanical properties. Impregnation process was carried out after moisture content stabilized at 12% on samples with a dimension of 20 mm × 20 mm × 300 mm at various concentrations and pressure time. Dimensional stability was evaluated by thickness swelling (TS) and anti-swelling efficiency (ASE) and the young's modulus was conducted according to BS 573. The mechanical properties and dimensional stability of impregnated wood were evaluated. Dimensional stability and mechanical properties of Falcataria wood were successfully increased after impregnation. PF impregnation can improve the mechanical properties and the density from 0.26 g/㎤ to 0.30 g/㎤ even with only 10% of weight percent grain. Dimensional stability increases with increasing resin concentration and time pressure. The highest increase in mechanical properties was found at a higher concentration of PF. The penetration of PF into the wood's cell darkens the color of impregnated wood.

• Journal of the Korean Wood Science and Technology
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• 제24권4호
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• pp.87-92
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• 1996

When cutting 2.0cm-thick red oak and hard maple with an air-jet-assisted carbon-dioxide laser of 2kW output power, maximum feed speed at the point of full penetration of the beam decreased with increasing the angle between grain and cutting direction. Feed speed averaged 3.75 and 3.38 meters per minute for red oak and hard maple, respectively. Gray-level of laser-cut surfaces were analyzed by image analysis system. The highest gray level of laser-cut surface was obtained when red oak was cut parallel to grain by laser. Surface profiler was used to scan the sawn and laser-cut surfaces. Center line average roughnesses of laser-cut surfaces were higher than those of sawn surfaces. Scanning electron micrographs showed the cell walls which were melted by laser.

• Journal of the Korean Wood Science and Technology
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• 제49권1호
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• pp.57-66
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• 2021

In recent years, the use of cross laminated timber (CLT) has been evolving. In addition, CLT manufactured with various species such as Japanese cedar has been developed to utilize the local resources in each country. However most factories in Japan produce CLT by bonding the laminae in width direction for orthogonal layers, where grain of element is perpendicular to the grain of outer layer, and this process is considered to be one of the factors that reduce productivity. A new wood based material (hereinafter referred to as Ply-lam) using wooden panel such as plywood for the orthogonal layer was developed in order to improve productivity in CLT manufacturing and improve quality. Japanese cypress lamina was used for the parallel layer, where grain of element is parallel to the grain of outer layer, of CLT and Korean larch plywood was used for the orthogonal layer, in order to effectively use Korean larch and expand the utilization of Japanese cypress. The cross-sectional construction of the Ply-lam was 5-layers 5-plies, and the dimensions were 1000 mm (width) × 150 mm (depth) × 4000 mm (length). As a performance evaluation of the manufactured Ply-lam, strength tests such as out-of-plane bending, in-plane bending, out-of-plane shearing and in-plane shearing tests were carried out. As the result of this study, Ply-lam composed of Japanese cypress lamina panels and Korean larch plywood showed very higher out-of-plane bending strength compared to the standard strength of CLT. And the result obtained in other tests seems to show a sufficiently high value.

• Journal of the Korean Wood Science and Technology
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• 제41권5호
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• pp.425-431
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• 2013

Estimation equations of shear modulus in the plane of laminated veneer lumber (LVL) were compared each other through uniaxial tension test results. The equations - basic elastic equation in the dimensional orthotropic case, Hankinson's formula and empirical equation proposed by Salikis and Falk, were applied to determine the elastic constants at various angles to the grain, which were needed for determination of shear modulus. Tensile elastic modulus of LVL predicted from these equations were compared with test data to evaluate the accuracy of the equation. Tensile elastic modulus rapidly decreased at orientations between 0 and 15 degrees and elastic modulus at grain angles of 15, 30, and 45 degrees overestimated in the presented equations. But the proposed equation by Salikis and Falk showed better prediction, especially at 30, and 45 degrees. This proposed formula would be more useful and practical for estimating of shear modulus of wood composites like LVL to minimize the effect of Poisson's ratio term.

• Journal of the Korean Wood Science and Technology
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• 제50권4호
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• pp.237-245
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• 2022

This study examined the structural performance of experimental parallel strand lumber (PSL) from a Larch veneer strand. The prototype of PSL from a Larch veneer strand was manufactured in the experimental laboratory and tested. The bending and dowel bearing strength were determined from the modulus of elasticity (MOE), modulus of rupture (MOR), and dowel bearing strength based on a 5% offset yield load. The test results indicated that the average MOR of PSL was higher than that of 2 × 4 dimension lumber, and the average MOE of PSL was lower than that of 2 × 4 dimension lumber. A linear relationship was observed between the MOR and MOE. The allowable bending stress of PSL was derived as specified in ASTM D2915 and compared with other research. The dowel bearing strength of PSL in parallel to the grain was approximately double that perpendicular to the grain of PSL. A comparison of several theoretical calculations based on each national code for the dowel bearing strength was conducted, and some theoretical equations produced results closer to the experimental results when it was parallel to the grain, but the difference was higher in the case perpendicular to the grain. The test results showed that PSL made with Japanese larch veneer strands appeared to be suitable for a raw material of structural composite lumber (SCL) appeared to be used as a raw material for SCL.

• 농업과학연구
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• 제37권3호
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• pp.465-469
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• 2010

In order to develop effective recycling technologies of disused railway wood ties, wood properties and residual creosote oil of wood ties were investigated. Among the total 50 wood ties, 32 wood ties were identified as tropical hardwood tree, such as, Keruing (Dipterocarpus spp.), Kempas (Koompassia malaccensis), Kapur (Dryobalanops spp.) Naytoh (Palaquium rostratum), and so on. Disused wood ties showed mostly sound structure without degradation of cell walls by decay fungi. Disused wood ties showed high strengths of bending and compressive parallel to grain because degradation of wood properties was hardly occurred in use under exterior condition. Disused railway wood ties had relatively poor depth of penetration and residual of creosote oil because of refractory wood structures. These results suggest that disused railway wood ties may be useful as recycling wood wastes.

• Journal of Forest and Environmental Science
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• 제28권4호
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• pp.268-277
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• 2012

Among the domestic softwoods, technical value of Pinus koraiensis small diameter logs which have comparatively low applicability was evaluated and sensitive characteristics and physical characteristics were investigated and analyzed for examining if it can be utilized as the interior decoration material. For the sensitive characteristics of Pinus koraiensis, wood figure, wood grain, wood color and odor were evaluated and for the physical characteristics, growth-ring width and latewood percentage, abrasion, density, shrinkage, swelling, absorption, roughness and hardness were evaluated. Then, the possibility to be developed as the interior decoration material was found. As the result of evaluating sensitive characteristics and physical characteristics of domestic Pinus koraiensis, wood figure, wood grain, color and scent clearly were judged to have excellent visual factor as the interior decoration material. And, physical characteristics were also judged to be excellent, so it is judged to be developed as the interior decoration material. Therefore, as the result of various forms of design pattern with domestic Pinus koraiensis small diameter logs, several patterns of interior decoration can be developed by characteristics of each side and colors of heartwood and sapwood. And, in the future, it can be applied to furniture design or interior decoration material for the proper use. Especially, it is considered to contribute to wood applying industry through the study on the quality of domestic small diameter logs which have low applicability.

• 한국가구학회지
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• 제21권2호
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• pp.188-195
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• 2010

This study has been focused on the evaluation of domestic softwood timbers to replace imported timbers for woodcrafts and furniture-making. Figures on radial and tangential sections were observed with naked eyes. As the result of study on the figures appeared on the wood surface of 6 species of trees, flat grain and edge grain were clearly found from Taxus cuspidata. Juniperus chinensis and Ginkgo biloba had wavy grain figure and pigment figure, and blister figure was found in Pinus densiflora, Larix kaempferi showed pitch streak and irregular figures on its tangential section due to growth abnormalities. Wavy grain figure appeared weakly on near knot of Pinus koraiensis. The characteristic figures shown from each species of trees are expected to be used for crafts, sculptures, furniture, and interior decoration. They are also considered to have great potential to substitute imported timber sufficiently, which are currently used a lot for wood crafts and furniture-making.

• Journal of the Korean Wood Science and Technology
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• 제25권2호
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• pp.27-32
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• 1997

This study was carried out to find the relationship between anatomical characters and compression strength parallel to grain of Pinus densiflora S. et. Z., the representative conifer species in Korea. The results were as follows ; 1. The compression strength parallel to grain increased with the increase of tracheid length and wall thickness. The strength, however, decreased with the increase of height of uniseriate ray and microfibril angle. 2. The major factors affecting compression strength parallel to grain in heartwood were radial diameter of latewood tracheid and wall thickness of earlywood tracheid but length and tangential diameter of latewood tracheid were the important factors in sapwood.

• Journal of the Korean Wood Science and Technology
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• 제18권2호
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• pp.67-78
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• 1990

This study was performed to determine the characteristics of physical and mechanical properties of domestic wood based materials; plywood, particleboard, medium density fiberboard. Main items of tested properties were panel size, moisture content, water absorption, linear expansion and thickness swelling, glue bond shear strength, bending properties(stress at proportional limit, modulus of rupture. modulus of elasticity), tensile strength, screw holding strength, and internal bond as neccessary. the results were discussed mainly with Korean Standards. The obtained conclusions are as follows; 1. Length and width of 3mm thin plywood(3-ply) and 12mm thick plywood(7-ply) were satished with KS-standard, but thicknesses of these panels were not- passed tolerance limit except one of eight makers. 2. Length and width of particleboard and medium density fiberboard were greater than the tolerance limit value of KS standard, but the thicknesses of these panels were passed this value. 3. Moisture contents of 12mm thick and 3mm thin plywood were satisfied with KS-standard except one mill made 3mm thin plywood. 4. Moisture absortion of plywood was not passed tolerance limit of KS-standard but particleboard was satisfied with this standard value. 5. Dry and wet shear strengths in glue bond of 3mm thin plywood were not reached to KS-standard, but those of 12mm thick plywood were sufficiently satisfied with KS standrad. 6. Modulus of ruptures, parallel to grain and perpendicular to grain of plywood, and particleboard and medium density fiberboard were satisfied with KS-standard. 7. Tensile strengths, parallel to grain and perpendicular to grain of plywood were satisfied with allowance stress of US product standard PS 1-74. 8. Screw holding strength of particleboard was not reached to KS standard, but internal bond was satisfied with KS standard.