• Journal of the Korean Wood Science and Technology
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• 제31권5호
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• pp.72-79
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• 2003

신뢰성 설계에서 재료강도의 분포 특성은 기본적인 입력 변수로 사용된다. 따라서 강도특성의 분포형태 및 그에 따른 인자들을 정확하게 결정하는 것은 신뢰성 설계를 위한 필수적인 작업이다. 지금까지 강도성능 평가는 주로 무결점 소시편에 대한 실험결과가 사용되어 왔다. 그러나 이러한 방법은 부재가 실재 사용되는 조건을 제대로 반영하지 못함에 따른 오차를 포함하게 된다. 본 연구에서는 구조재로 많이 사용되는 2×6부재(38 mm×140 mm, 길이 3.0 m) 498본에 대하여 육안검사를 통해 등급을 구분하고, 휨시험을 실시하였다. 신뢰성 설계로 전환을 위해 각 등급의 강도특성에 대한 분포형태 및 인자를 결정하였다. 분포형태의 결정을 위해 정규분포, 대수정규분포, 웨이블분포의 세가지 분포형태에 대한 square error를 비교하고, KS test를 통하여 결정된 분포형태의 적합성을 확인하였다. 모든 등급에서 휨강도(MOR)의 가장 적합한 분포형태는 웨이블분포로 나타났으며, 휨탄성계수의 경우는 정규분포가 가장 적합한 것으로 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제40권1호
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• pp.38-43
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• 2012

억새파티클보드의 흡음재로서의 사용가능성을 파악하고자 몇 가지 목표비중의 억새파티클보드를 제작하여 전달함수법(two microphone transfer function method)으로 상용주파수대역에서 흡음성능을 측정하고 휨강도 시험으로 역학적성질을 각각 측정, 비교하여 다음과 같은 결과를 얻었다. 측정주파수범위에서 거대억새보드의 흡음률이 상용석고보드보다 높은 흡음성능을 나타내었다. 탄성계수와 휨강도는 목표비중 증가에 따라 증가하는 경향을 나타내었다. 억새보드의 흡음률은 1~2.5 Khz 범위의 주파수범위에서 50~80%의 수치를 나타내다 이후 주파수에서는 30~50%의 흡음률을 나타내었으며 비중에 따라서는 비중이 증가할수록 흡음률이 낮아지는 경향을 보였다.

• Journal of the Korean Wood Science and Technology
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• 제43권4호
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• pp.429-437
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• 2015

아세틸화처리는 목재의 치수안정성을 높이는 방법으로 알려졌다. 기상처리보다는 액상처리가 중량증가율이 높기 때문에 더 많이 사용된다. 국내산 소나무재와 잣나무재를 액상 아세틸화처리하여 밀도, 휨강도, 치수안정성 등 물리적 성질에 미치는 효과를 조사하였다. 아세틸화처리에 의한 소나무와 잣나무 시편의 중량은 각각 평균 10.4%와 9.2% 증가하였으며, 전건밀도는 각각 평균 6.9%와 4.6% 증가하였다. 소나무와 잣나무 모두 휨파괴계수(MOR)와 휨탄성계수(MOE), 동탄성계수(DMOE)의 변화는 없었다. 아세틸화처리 후 목재시료의 평균 항흡습률(PRH)은 소나무와 잣나무가 각각 20.6%와 13.8% 이었다. 평균 항흡수율(PRA)은 소나무와 잣나무가 각각 20.0%와 8.5%였다. 따라서 아세틸화처리에 의해 소나무의 치수안정성이 향상된 결과를 얻었다.

• Journal of the Korean Wood Science and Technology
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• 제35권5호
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• pp.38-45
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• 2007

Flakeboards made from ring- and drum-cut flakes of Douglas-fir, hemlock, red lauan and kapur using two kinds of resin levels were evaluated for the selected properties according to flake thickness. The pH and buffering capacity of four species were determined. Those of kapur were extremely different from the other three species. These pH and buffering capacity values result in the poor internal bond strength of kapur flakeboard. The internal bond strength was affected significantly by flake thickness, resin content and species. MOR and MOE in bending strength were maximized at medium drum-cut flake thickness. Screw holding strength was not consistent for flake thickness, but it was influenced by species. Thickness swelling and water absorption of Douglas-fir and hemlock flakeboard were minimized at medium drum-cut flake thickness.

• 한국가구학회지
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• 제11권2호
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• pp.67-72
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• 2000

Some physical characteristics as thickness swelling, heat conduction, and bending properties of composite hoards made of waste wood chip and charcoal were measured. Wood-charcoal composite boards of three types and cement board were prepared for this study as shown in Table 1, Keeping duration of strawberries in the boxes($25cm{\times}25cm{\times}25cm$) manufactured with the boards was also examined. Thickness swelling and bending properties(MOR and MOE) of board B and C were lower than those of board A. Among the wood-charcoal composite boards except cement board, there were no differences in heat conduction(mm/sec.). Strawberries in the box with board C were kept longer duration in fresh condition than that with cement board. From the results, it is suggested that wood-charcoal composite boards can be used for eco-material.

• Journal of the Korean Wood Science and Technology
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• 제48권2호
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• pp.245-252
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• 2020

This study was performed to analyze the mechanical properties of tropical hybrid cross-laminated timber (CLT) with bamboo laminated board as the core layer in order to evaluate the possibility of its use as a CLT material. Bamboo board was used as the core layer and the tropical species Acacia mangium willd., from Indonesia, was used as the lamination in the outer layer. The modulus of elasticity (MOE), modulus of rupture (MOR), and shear strength of the hybrid CLT were measured according to APA PRG 320-2018 Standard for Performance-Rated Cross-Laminated Timber. The results show that the bending MOE of the hybrid CLT was found to be 2.76 times higher than SPF (Spruce Pine Fir) CLT. The reason why the high MOE value was shown in bamboo board and hybrid CLT applied bamboo board is because of high elasticity of bamboo fiber. However, the shear strength of the hybrid CLT was 0.8 times lower than shear strength of SPF CLT.

• Journal of the Korean Wood Science and Technology
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• 제19권2호
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• pp.65-71
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• 1991

본 연구는 CCA 처리재의 재건조(再乾燥)시 적용된 건조 스케쥴 (통상(通常) 열기건조(熱氣乾燥)와 고온건조(高溫乾燥) 스케쥴)이 처리재의 휨강도(强度) 성질에 미치는 영향을 고찰하고자 수행되었다. 탄성계수(彈性係數)(MOE), 그리고 비파괴시험(非破壞試驗)에 의해 얻어진 동적(動的) 탄성계수 (Dynamic MOE) 및 대수감쇠율(對數減衰率)(Logarithmic decrement) 은 처리후 재건조에 의해 큰 영향을 받지 않았다. 반면에 적용된 건조 스케쥴에 관계없이 재건조시 심각한 파괴계수(破壞係數)(MOR)의 감소가 파괴계수 분포의 모든 영역에서 초래되었다. 그러나 통상 열기건조(최대 건구온도=$71^{\circ}C$)와 고온건조(건구온도=$110^{\circ}C$) 서로간에는 감소의 정도에 큰 차이가 없었다. 따라서, 처리재의 재건조사 심각한 파괴계수의 감소가 용인(容認)되지 않는다면 CCA로 처리된 Lodgepole pine 각재의 재건조는 미국 연방 임산물 시험장의 Lodgepole pine의 통상 열기건조 스케쥴 (T9-C3) 보다 온화(溫和)한 조건으로 실시되어야 할 것이다.

• Journal of the Korean Wood Science and Technology
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• 제13권4호
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• pp.67-72
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• 1985

To improve the bending strength of sawdustboard, verious resin contents of 10, 13, 16, and 19% were applied to the thin shell (face layer) composed with wire net or not. The shell effect of sawdust and wire net composition formed with core sawdustboard were evaluated. Forcusing on the effects of wire net composition and noncomposition including a comparison with chipboard and veneer complyboard, bending properties (Modulus of rupture (MOR), Modulus of elasticity (MOE), Stress at proportional limit ($S_{pl}$). Work to maximum load ($W_{ml}$))were analyzed and discussed. 1. In modulus of rutpute, veneer comply was the highest (621.5 kg/$cm^2$), and next decreasing order was wire net composition (159.1 kg/$cm^2$), chipboard (81.75 kg/$cm^2$), and wire net noncomposition (76.21 kg/$cm^2$) as in modulus of elasticity, work to maximum load, except for stress at proportional limit. 2. The highly significant effects were shown in both wire net composition and noncomposition, at the same time wire net composition exceeded two times of noncomposition throughout resin contents in bending properties. Chipboard was similar to the mean or 16% resin content in noncomposirion. 3. Every board in wire net composition above 10% resin content was beyond 100 kg/$cm^2$ in MOR, minimum allowable strength for structural use according to KS F 3104. In conclusion, the feasibility for improving the bending strength of weak sawdustboard by wire net composed shell was offered.

• Journal of the Korean Wood Science and Technology
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• 제45권6호
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• pp.787-796
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• 2017

A low dimensional stability and poor bending strength properties were main problems in particleboard manufacturing. The objective of this research was to evaluate the effect of mixed wood species and urea-formaldehyde (UF) or urea-melamine-formaldehyde (UMF) resins on the physical and mechanical properties of three-layer particleboards. The ratio of face/core/back layer was 1 : 2 : 1. The resin content of 12% for both UF resins and UMF resins (UF/MF = 70/30% w/w) was used. The results of this study showed that the utilization of S.mahagony shaving using both UF and UMF resins caused a decrease in the thickness swelling and water absorption of the boards. Thickness swellings of particleboard made of Sengon/Sengon/Sengon (SSS), Mahogany/Mahogany/Mahogany (MMM), Sengon/Mahogany/Sengon (SMS), and Mahogany/Sengon/Mahogany (MSM) were in the range of 23%, 12~16%, 14~16%, and 13~21%, respectively. The board bonded with UMF resin demonstrated better dimensional stability than that bonded with UF resin alone. Modulus of elasticity (MOE) and modulus of rupture (MOR) of particleboards made of S. mahagony shaving in the surface layer in both MMM and MSM boards were better than those of the SSS and SMS. MOE of MMM and MSM board was in the ranges of 24,000 to $26,000kg.cm^{-2}$ and 18,000 to $21,000kg.cm^{-2}$ respectively. Meanwhile, the MOR of board was in the ranges of 200 to $240kg.cm^{-2}$ and 190 to $228kg.cm^{-2}$, respectively.

• Journal of Forest and Environmental Science
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• 제36권3호
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• pp.219-224
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• 2020

Urea formaldehyde resins are widely used in the manufacturing of wood composite and their usage is always combined with release of formaldehyde characterized to be hazardous to health during and after the manufacturing of the products. This study investigates the effectiveness of wood-based adhesive from oil of pyrolysed Triplochiton scleroxylon sawdust for the production of composite board. The wood-derived Pyrolytic Oil (PyO) was blended with Urea Formaldehyde (UF) resin to formed Pyrolytic Oil-Urea Formaldehyde (PyOUF). The obtained PyOUF called Wood-Based Adhesives at four blends and control (UF) viz; 1:1, 1:2, 1:3, 2:1, 1:3 were further employed to prepare the composite board and test for their bonding strength by physical (water absorption-WA and thickness swelling-Th.S) and mechanical properties (modulus of elasticity-MOE, modulus of rupture-MOR, and impact bending-IB). Data obtained was analysed using analysis of variance at α 0.05. The result of analysis of variance conducted on physical properties show significant difference (p≤0.05) between the WA values obtained when testing the different blending proportion of PyOUF and likewise between 2 and 24 h of immersion. PyOUF had significant effect (p≤0.05) on Th. S for 24 h but no significant different (p>0.05) for the 2 h period of soaking. The analysis of variance on mechanical properties of the composite board (MOE, MOR, and IB) show significance differences (p≤0.05) between the strength values obtained when testing the different ratios of PyO with UF. PyO content influenced the properties of the boards and it is evident that PyO can be used in the manufacture of composite board.