• Journal of the Korean Wood Science and Technology
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• v.19 no.3
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• pp.53-61
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• 1991

Mechanical properties of composite panel made with 3mm thick Apitong(Dipterocarpus grandiflorus) veneer on each face of particleboard core of 4 different specific gravity were determined. The results obtained were as follows: 1. Measured MOR and MOE increased with an increased in specific gravity of particleboard core. 2. Test results showed that the difference in bending properties between flatwise bending and edgewise bending was present. The average MOE value of flatwise loading was higer than that of epdgewise loading. But it was shown reverse tendency in MoR and MOE. 3. The delamination between face veneer and core particle was found in flatwise bending but nell in edgewise. 4. These composite panel could be substituted for plywood and other panel materials in furniture making as considered suitable allowable stress and bending strength.

• Journal of the Korean Wood Science and Technology
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• v.31 no.4
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• pp.24-30
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• 2003

In order to develop structural 'bamboo zephyr board', properties of boards produced by various methods making zephyr were estimated. All of boards were tested with KS(Korean Standards) F 3014 Particle board, and results were summarized as follow. The zephyr boards produced by final 1.5 mm roller space had the best properties(MOR, MOE and IB strength) among boards produced by different final roller space. Also, they had the best properties(MOR and MOE) in bending test after 1 hour soaking treatment after 2 hour-boiling in water, which were similar to properties of boards in dry-condition. Thickness swelling(TS) of all boards was less than 12% required to the Korean Standards A 3014. Zephyr boards produced by final 1.5 mm roller space also had the lowest values among all of boards. Boards produced by non-treatment (in green condition) had the better strength than those of boards produced by different pre-treatment methods(boiling in water and in 0.3% NaOH) in bending test.

• Journal of the Korean Wood Science and Technology
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• v.40 no.5
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• pp.303-310
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• 2012

Heat treatment improves dimensional stability and sound absorption properties of wood. However, mechanical properties of wood can be deteriorated during the heat treatment. The effect of heat treatment on the bending strength and hardness of wood for Korean paulownia, Pinus densiflora, Lidiodendron tulipifera and Betula costata were measured. The heat treatment temperature has been investigated at $175^{\circ}C$ and $200^{\circ}C$, respectively. The results showed that the weight and density of wood decreased after heat treatment. It was found that the density by heat treatment was lower at $200^{\circ}C$ than that at $175^{\circ}C$. And, MOE increased with the reduced density. On the contrary, MOR and hardness decreased. In all conditions, It was found that there was a high correlation of 1% level between bending modulus of elasticity and modulus of rupture.

• Journal of the Korea Furniture Society
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• v.19 no.5
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• pp.350-357
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• 2008

This research investigates the bending properties to predict the work-energy to maximum load and impact bending energy from static bending and impact bending test. Specimens were prepared from lumber made of thinning crop-trees. Matched specimens were used for MC 12% and green moisture specimens to measure the effect of moisture content on the absorbed energy from static and impact bending tests. The bending properties such as MOE, MOR, etc. is a good predictor to investigate the work-energy and work-energy per unit volume from static bending and impact bending test. The impact bending energy is increased with increasing moisture content. However, the work to maximum load from static bending test is increasing with increasing the MC only for higher density species.

• Journal of the Korea Furniture Society
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• v.10 no.2
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• pp.73-78
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• 1999

This paper describes the relationship between the bending strength properties of sloped finger-jointed woods and the acoustic emissions(AEs) generated during the test. Rhus verniciflua pieces were cut in sloped-finger types and glued with three kinds of adhesives(polyvinyl acetate, polyvinyl-acryl acetate and oilic urethane resin). The slope ratios of finger joints were 0, 1.0, 1.5, and 2.0. The AE cumulative event count and cumulative count were measured during the bending test. The results were as follows: The lower the bending strength(load) was, the generation time of AE event count got and the higher the increasing rate of AE event count became in the sloped finger-jointed specimens bonded with polyvinyl acetate, polyvinyl-acryl acetate oilic urethane resin adhesives. Therefore, the slope from load-AE cumulative event count was very steep. The patterns of AE event count and count were very similar. The relationship between the MOR and the AE parameter from load and AE cumulatve event count in the early stage of the sloped finger-jointed specimens bonded with polyvinyl acetate, polyvinyl-acryl and oilic urethane resin adhesives was much greater than that between the MOE and the MOR. Therefore, the AE signals obtained during bending test are useful for estimating the strength of sloped finger-jointed Rhus verniciflua specimens.

• Journal of the Korea Furniture Society
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• v.13 no.2
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• pp.11-18
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• 2002

This study was carried out to investigate the strength and technical feasibility of glulam from small diameter Pinus densiflora and Larix kaempferi. Small diameter logs are currently not used in structural laminated beam construction, but it is suggested that its properties may be feasible for this purpose. The glulam combinations were designed with high grade laminae located at outer laminations (face) and low grade laminae located at center laminations. Important problems of finger jointed glulam as a structural beam are the small modulus of rupture (MOR). One solution for this problem Mi to use veneer and solid wood as the face laminae. The MOE values were predicted for each beam from laminae. The results showed that actual beam MOE values exceeded slightly the predicted values. Based on the evaluation and analysis of Pinus and Larix glulam, the maximum load of Larix kaempferi glulam indicated large values. The bending properties of A and E types glulam were superior to others. It is suggested that this small diameter log can be a candidate for structural glulam construction, providing the proper combinations of face laminae.

• Journal of the Korea Furniture Society
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• v.11 no.2
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• pp.7-12
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• 2000

This paper describes the bending strength properties of laminated woods which had three kinds of specimens according to finger length-12, 4.5 mm and butt joint and the acoustic emissions (AEs) generated during the test. 3-ply laminated wood beams were tension side layers (lower layers) composed of one middle lamina and two side-jointed laminae, with one butt joint ($_1BJ$), one finger joint (12mm, $_1FJ_{12}$) or one finger joint (4.5mm, $_1FJ_{4.5}$) in the middle lamina of tension side layer. And 3-ply laminated wood beams were tension side layers (lower layers) also composed of one lamina, with one butt joint (BJ), one finger joint (12mm, $FJ_{12}$) or one finger joint (4.5mm, $FJ_{4.5}$/) in tension side layer. Cryptomelia pieces were cut for butt and two finger types and glued with resorcinol-phenol resin adhesive. The results were as follows It was not effective in the bending modulus of elasicity (MOE) with IFJL type and had no difference from finger length. The bending modulus of rupture (MOR) of laminated wood beams including finger joint was the same values as that including butt feint and had no difference from finger length. It was effective in MOE with FJL type and had no difference from finger length. The effect of finger joint on MOR was much higher than that of butt joint but had no difference from finger length. The AE generation time of IFJL type was earlier than that of the control wood and the number of AE count was much more than that of the control wood. However, the AE generation time of FJL type was earlier than that of the control wood and the number of U count was much fewer than that of the control wood.

• Journal of the Korean Wood Science and Technology
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• v.30 no.2
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• pp.95-101
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• 2002

Physical and mechanical properties of major Korean ash species were examined. For Fraxinus rhynchophylla and Fraxinus sieboldiana, green moisture content of sapwood was almost the same value as heartwood. Heartwood of Fraxinus mandshurica, however, had slightly higher moisture content than sapwood. Green and oven dry densities of F. mandshurica were lower than those of F. rhynchophylla and F. sieboldiana. Swelling and shrinkage of sapwood in F. sieboldiana showed somewhat higher value than those of F. rhynchophylla. Longitudinal compressive strength and modulus of elasticity in F. sieboldiana were lower values than those in the other species. Shearing strength in radial section was higher than that in tangential section of all samples. It could be noted that shearing strength of F. sieboldiana demonstrated higher value than that of the other species. Three species had excellent bending properties in MOR and MOE. Impact bending absorbed energy for F. rhynchophylla and F. mandshurica did not show any significant differences.

• Journal of the Korea Furniture Society
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• v.15 no.2
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• pp.19-27
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• 2004

As glulam is a woody material, it is necessary to be more careful in a gluing process. It takes 6-7 hours at $40-60^{\circ}C$ to harden PRF resin used in making structural glulam, and about 24 hours at room temperature. In the present process which can not use a press continuously, reducing the hardening time is necessary to increase production. The experiment was done to compare the adhesive properties of PRF resin and MUF resin through bending test, block shear strength test and water soaking test. In comparing the bending strength of prediction MOE is 1.2 times higher that actual MOE. PRF and MUF do not show significant difference in MOE and MOR, and in block shear strength test, such as shear strength and wood failure rate. However, in water soaking and boiling water soaking tests PRF and MUF show the significant difference in delamination rate.

• Journal of the Korean Wood Science and Technology
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• v.46 no.5
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• pp.486-496
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• 2018

This study was conducted to confirm an effect of span length on bending properties of larch dimensional lumber in the four point bending test. The size of specimen in this study was 38 (width) ${\times}$ 89 (depth) ${\times}$ 3,600 (length) $mm^3$, and average air-dry density and moisture content of the specimens was $543.5kg/m^3$ and 10.5%, respectively. Visually graded No. 1 dimensional lumbers of 248 were divided by two groups to compare modulus of rupture (MOR) and modulus of elasticity (MOE). One group was tested in the four point bending test with span length of 1,650 mm, and other was tested with span length of 3,000 mm. While MOE was not different according to span length in 5% significance level, MOR was different in accordance with span lengths and was in inverse proportion to change of span length. Fifth percentiles of MOR in span length of 1,650 and 3,000 mm were 28.65 and 25.70 MPa, respectively. It was confirmed that the difference between MORs in each case increased as normalized rank increased. This is because of size effect in Weibull weakest link failure theory. Therefore, KS F 2150, in which there is only regulation about span to depth ratio of 15 or more, is needed to be revised to contain a method considering size effect for MOR. From the method, various results of bending test with different size of lumber could be used to determine design value of lumber.