• Journal of the Korean Wood Science and Technology
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• 제34권2호
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• pp.46-57
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• 2006

To estimate nondestructively strength performances of laminated woods, 3-ply parallel- and cross-laminated wood specimens exposed under atmosphere conditions after bending creep test were prepared for this study. The effects of density of species, arrangement of laminae and lamination types on dynamic MOE obtained by flexural vibration were investigated, and regression analyses were conducted in order to estimate static bending strength and bending creep performances. Dynamic MOE of parallel-laminated woods showed 1.0~1.2 times higher values than static bending MOE, and those of cross-laminated woods showed 1.0~1.4 times higher values than static bending MOE. The degree of anisotropy of dynamic MOE perpendicular to the grain of face laminae versus that parallel to the grain of face laminae was markedly decreased by cross-laminating. There were strong correlations between dynamic MOE by flexural vibration and static bending MOE (correlation coefficient r = 0.919~0.972) or bending MOR (correlation coefficient r = 0.811~0.947) of 3-ply laminated woods, and the correlation coefficient were higher in parallel-laminated woods than in cross-laminated woods. It indicated that static bending strength performances were able to be estimated from dynamic MOE by flexural vibration. Also, close correlations between the reciprocal of dynamic MOE by flexural vibration and initial compliance at 0.008 h of 3-ply laminated woods were found (correlation coefficient r = 0.873~0.991). However, the correlation coefficient between the reciprocal of dynamic MOE and creep compliance at 168 h of 3-ply laminated woods was considerably lower than those between dynamic MOE and initial compliance, and it was hard to estimate creep compliance with a high accuracy from dynamic MOE due to the variation of creep deformation.

• Journal of the Korean Wood Science and Technology
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• 제45권6호
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• pp.689-702
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• 2017

In this study, with the view to using effectively small and medium diameter Korean domestic woods as structural materials, cross-laminated woods were manufactured by using six species of Korean domestic softwoods and hardwoods, and bending creep properties were investigated for each species. The creep curves showed the shape of the exponential function plot, and the creep curves after 1 hour were able to estimate by fitting it to the power law. The initial and creep compliances of cross-laminated woods showed the higher values in wood species with a low density than in that with a high density. And by cross-laminating, the initial and creep compliances perpendicular to the grain considerably decreased, the extent of the decrease was found to be greater in creep deformation than in initial deformation. The creep anisotropies of cross-laminated woods were considerably decreased by cross-laminating. The relative creep of $C_{\bot}$ type composed of perpendicular-direction lamina in the faces decreased 0.59 - 0.64 times compared to that of $P_{\bot}$ type composed of perpendicular-direction laminae in all layers, and that for $C_{\parallel}$ type composed of parallel-direction laminae in the faces increased 1.5 - 1.6 times compared to that of $P_{\parallel}$ type composed of parallel-direction laminae in all layers.

• Journal of the Korean Wood Science and Technology
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• 제37권6호
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• pp.546-555
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• 2009

이 연구에서는 목재의 효율적인 이용의 일환으로 스프루스 직교형적층재의 중층을 중밀도섬유판(medium density fiberboard, MDF), 파티클보드(particle board, PB) 및 배향성스트랜드보드(oriented strand board, OSB)의 3종류의 시판용 목질보드를 복합적층한 3층 목질계 복합적층재(패널)를 제작하여, 중층목질재료라미나의 구성엘리멘트가 복합적층재(패널)의 휨 강도성능에 미치는 영향을 조사하였다. 목질계 복합적층재의 휨 탄성계수는 중층에 배향성스트랜드보드(OSB)를 배열한 복합적층재에서 가장 높은 값을 나타내었고, 중밀도섬유판(MDF)을 중층에 배열한 복합적층재에서 가장 낮은 값을 나타내었다. 이 값은 중층에 섬유직각방향라미나를 배열한 다양한 종류의 직교형적층재 보다 높은 값을 나타내는 것이 확인되었다. 표층이 스프루스 섬유직각방향으로 된 복합적층재의 휨 탄성계수 예측치는 실측치와 비슷한 값을 나타내었으나, 표층이 스프루스 섬유방향으로 된 복합적층재의 휨 탄성계수 예측치는 실측치보다 높은 값을 나타내었다. 복합적층재의 휨 강도는 배향성스트랜드보드(OSB)를 중층에 배열한 타입에서 가장 높은 값을 나타내었고, 파티클보드(PB)를 중층에 배열한 타입에서 가장 낮은 값을 나타내어 휨 탄성계수와 약간 차이를 나타내었다. 복합적층에 의해, 복합적층재의 휨강도 성능의 이방성은 스프루스소재의 그것에 비해 현저히 감소하였고, 보드상호간의 강도성능의 차이도 현저히 감소하는 것이 확인되었다.

• Journal of the Korean Wood Science and Technology
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• 제42권3호
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• pp.290-300
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• 2014

이 연구에서는 가문비나무를 이용하여 직교형적층재를 제작하였고, 섬유직각방향라미나의 연륜경사각이 직교형적층재의 정적 휨 강도성능에 미치는 영향을 조사하였다. 3층 모두가 섬유직각방향라미나로 구성된 평행형적층재($P_{\bot}$ 타입)의 휨 강도성능은 연륜경사각 $90^{\circ}$ > $0^{\circ}$ > $45^{\circ}$의 순이었고, 연륜경사각 $45^{\circ}$에서 휨 탄성계수는 0.0989 GPa, 휨 강도는 3.25 MPa로 가장 적은 값을 나타내었다. $P_{\bot}$ 타입의 중층에 섬유방향라미나를 배열하는 것에 의해 휨 강도성능은 현저히 향상되었다. 표층이 섬유직각방향라미나로 구성된 직교형적층재($C_{\bot}$ 타입)의 경우, 휨 강도성능은 연륜경사각 $90^{\circ}$ > $0^{\circ}$ > $45^{\circ}$의 순이었으나, 연륜경사각에 의한 차이는 평행형적층재에 비해 감소하였다. 중층에 섬유직각방향라미나를 배열한 직교형적층재($C_{\parallel}$ 타입)의 경우, 휨 강도성능은 $P_{\bot}$ 타입 및 $C_{\bot}$ 타입과 다르게 $45^{\circ}$ > $90^{\circ}$ > $0^{\circ}$의 순으로 연륜경사각 $45^{\circ}$에서 휨 탄성계수는 12.0 GPa, 휨 강도는 55.8 MPa로 가장 높은 값을 나타내는 것이 확인되었다.

• Journal of the Korean Wood Science and Technology
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• 제48권5호
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• pp.608-617
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• 2020

For efficient use and expansion of domestic small- and medium-diameter woods, cross-laminated wood panels composed of tropical hardwoods and domestic temperate woods were fabricated, and the bending creep behavior under long-term loading was investigated. The bending creep curve of the cross-laminated wood panels showed an exponential function graph with a sharp increase at the top right side. The wood panel composed of a teak top layer and larch core and bottom layers recorded the highest initial deformation, and that composed of a merbau top layer and tulip core and bottom layers showed the lowest initial deformation. Creep deformation of the cross-laminated wood panels showed the highest value in that composed of a teak top layer and larch core and bottom layers and showed the lowest value in that composed of a merbau top layer and tulip core and bottom layers. The obtained creep deformation is 3.1-4.3 times that of merbau, however, it is remarkably lower than that of tulip and larch. The highest relative creep was recorded by the wood panel composed of merbau top layer and larch core and bottom layers, whereas that composed of the teak top layer and tulip core and bottom layers showed the lowest relative creep.

• Journal of the Korean Wood Science and Technology
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• 제49권5호
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• pp.504-513
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• 2021

In this study, cross-laminated wood panels were manufactured with four softwoods and three hardwoods with the goal of efficiently predicting the static strength performance using dynamic modulus of elasticity (MOE) and simultaneously revealing the dynamic performance of cross-laminated wood panels. The effect of the density of the species on the dynamic MOE of the laminated wood panels was investigated. Moreover, the static bending strength performance was predicted nondestructively through the correlation regression between the dynamic MOE and static bending strength performance. For the dynamic MOE, the parallel- and cross-laminated wood panels composed of oriental oak showed the highest value, whereas the laminated wood panels composed of Japanese cedar showed the lowest value. In all types of parallel- and cross-laminated wood panels, the density dependence was confirmed, and the extent of the density dependence was found to be greater in the P_⊥ and C_⊥ types with perpendicular-direction laminae in the faces than in the P_∥ and C_∥ types with longitudinal-direction laminae in the faces. Our findings confirmed that a high correlation exists at a significance level of 1% between the dynamic modulus and static bending modulus or bending strength in all types of laminated wood panels, and that the static bending strength performance can be predicted through the dynamic MOE.

• Journal of the Korean Wood Science and Technology
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• 제46권6호
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• pp.726-734
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• 2018

In this study, for using effectively domestic (temperate) small and medium diameter logs as a wooden floorboard, cross-laminated wood panels were manufactured using domestic larch and tulip woods as a base material for teak and merbau wood flooring, and static bending strength performances were measured to investigate the applicability as the base materials of wooden flooring in place of plywood. Static bending MOE was much influenced by the strength performances of the top layer lamina than that of the laminae for base materials. Bending MOR showed the higher values in tulip wood that was hardwoods than in larch wood that was softwoods regardless of the strength performances of the top layer laminae, and it was found that the values were much influenced by the strength performances of the base materials used in the core and bottom layers. However these values were 1.4-2.5 times higher values than the bending strength of the wooden floorboards specified in KS, it was found that it can be sufficiently applied to the base materials of wooden floorboards in place of plywood.

• Journal of the Korean Wood Science and Technology
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• 제44권1호
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• pp.48-56
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• 2016

이 연구에서는 환경부하가 적은 산림훼손지 생태복원용 단위격자틀을 개발하기 위하여 콘크리트와 국내산 침엽수 4종과 활엽수 3종을 각각 복합적층한 7종류의 목재-콘크리트 복합적층재를 제작하였고, 정적 휨 강도성능에 미치는 수종의 밀도의 영향을 조사하였다. 목재-콘크리트 복합적층재의 휨 탄성계수는 전반적으로 수종의 밀도에 비례하여 증가하였고, 대부분 콘크리트에 비해 높은 휨 탄성계수를 나타내어 복합적층에 의한 밀도감소와 탄성계수향상의 효과가 나타났다. 휨 탄성계수 실측치는 각 라미나의 탄성계수로부터 등가단면법을 이용하여 계산한 예측치보다 약간 낮은 값을 나타내었고, 그 차이는 10% 미만인 것이 확인되었다. 목재-콘크리트 복합적층재의 휨 비례한도 응력은 콘크리트보다 1.2-1.6배의 높은 값을 나타내었다. 목재-콘크리트 복합적층재의 휨 강도는 전반적으로 수종의 밀도에 비례하여 증가하였고, 복합적층에 의해 콘크리트의 그것보다 현저한 강도향상을 나타내어 목재-콘크리트 복합적층재는 환경부하가 적으면서 내구성을 지닌 생태복원용 재료로 응용가능 할 것으로 판단된다.