• 한국가구학회지
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• 제10권1호
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• pp.23-32
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• 1999

The ultrastructural characteristics of shear fracture surfaces of laminated wood prepared from major four Korea wood specimens were examined. Commercial urea and urethan resin were used as adhesives for laminated woods of both homospecies and heterospecies. The morphology of fracture surface was observed using an optical microscopy and scanning electron microscopy. Three anatomical failure types were recognized : intercell failure, intrawall failure and transwall failure. In dry specimen, failure occurred mainly in woods. Laminated woods of softwoods showed mostly intrawall failure and transwall failure of tracheids, and them of hardwoods indicated mainly intrawall failure and interwall failure. Laminated woods prepared with urethan resin showed coarse fracture surface, on the other hand, those prepared with an urea formaldehyde resin had clean surface. In wet specimen, failure occurred dominantly in glue line. Intrawall failure and flags were characterized in laminated wood prepared with urethan resin. In heterospecies laminated woods, failure was occurred mainly in softwood. Consequently, fracture morphology of laminated wood may be influenced by adhesives, moisture content, species and anatomical characteristics.

• 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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• 제39권6호
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• pp.505-511
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• 2011

본 연구는 응력적층재의 압체력 경시변화에 대한 분석을 위해 수행되었다. 실내 외에 설치한 응력적층재의 압체력은 시간에 따라 감소하였으며, 응력적층재의 재압체 후 압체력 감소의 속도는 현저히 느려졌다. 하지만 응력적층재의 실사용을 위해서는 정확한 압체력의 예측이 필요한 것으로 사료된다. 기존의 압체력 예측 모델을 적용하여 압체력의 경시변화를 예측한 결과와 실제 압체력 변화는 상이한 양상을 나타내었으며, 이에 따라 시간과 외부환경에 따른 응력적층재의 압체력 예측 모델의 개발이 필요할 것으로 사료된다.

• 한국건축시공학회지
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• 제12권5호
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• pp.539-547
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• 2012

To manufacture laminated wood with improved mechanical properties by providing uniform adhesiveness, the adhesive was applied and the plate adhesive was laminated on the wood surface. Then, after laminating the wood on the top part of the adhesivebond, it was heated and dried while the adhesive was stiffened using microwaves, and the test piece was manufactured by compressing it with the press machine for thirty minutes. The temperature and the water content were examined according to the heating time of the wood heated with the microwave, and testing was conducted on the shear strength and flexural strength of the wood. In addition, the microstructure of the adhesive bond between the wood was recorded to confirm the penetrabilityinto the wood structure for the adhesive. After the test was conducted, it was found that the test piece manufactured with wood that has its water content leveled with the microwave heating showed improved shear strength and bending strength compared to the standard test piece. With regard to adhesives, liquefied polyvinyl acetate resin and plate's PVB resin were found to have superior adhesive strength. Also, after filming the cellular microstructure, it was found that when the laminated wood is heated with microwaves, the infiltration of the adhesive into the inside of the wood becomes easy, which makes it effective for improving adhesiveness.

• Journal of the Korean Wood Science and Technology
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• 제12권2호
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• pp.35-43
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• 1984

This study was carried out to investigate the block shear strength of the 2ply laminated wood composed of Pinus thunbergii with ureaformaldehyde resin as adhesives according to pressure (6, 9, 12, 15kg/$cm^2$), pressing time(5, 10, 20, 30 hrs.), amount of spread(54, 108, 217, 324g/$cm^2$), hardener(10, 20, 30, 40% of 10% $NH_4CL$ on resin) and extender(0, 5, 10, 15% wheat flour on resin), and the bending strength and bending young's modulus of laminated beam according to the number of ply. The results were summarized as follows; 1. According to pressing pressure with amount of spread 217g/$cm^2$ both dry and wet shear strength of laminated wood showed the highest in 15kg/$cm^2$, and hot-cold soaking treatment showed the highest in 9kg/$cm^2$, while all shear strength of dry, wet and hot-cold soaked laminated wood have been reduced with the increasing of pressing time. 2. According to amount of spread, adhesion strength with the dry, wet and hot-cold soaking treatments revealed the highest in 217g/$cm^2$ and have been reduced under or over 217g/$cm^2$ of spread. 3. According to addition of hardener and extender, all shear strength of laminated block with the dry, wet and hot-cold soaking treatments have been reduced in increasing of addition amount of hardener and extender. The bending strength of beam according to the number of ply showed the highest in 2ply laminated wood and horizontal loading beam to glue line had the higher in strength than the vertical loading.

• Journal of the Korean Wood Science and Technology
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• 제51권1호
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• pp.14-22
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• 2023

Economical use of larix (larch) boards (grade 3) in industries is lower than that of imported hardwood; thus, studies have been conducted toward performance improvement of larix boards. Herein, flexural modulus of larix board samples laminated with wood adhesives polyurethane resins, poly (vinyl acetate) resins, phenol-resorcinol-formaldehyde resins, melamine-formaldehyde resins, and urea-formaldehyde resins was compared with that of the samples bonded with adhesives reinforced with mesh-type basalt fibers. Moreover, the flexural moduli of the laminated samples bonded by mesh-type basalt fibers were compared with those of reinforced samples. The results showed that boards laminated with polyurethane and urea-formaldehyde resin adhesives had higher flexural modulus than those without the lamination. In particular, the increase in the flexural modulus was relatively significant for the 2- and 3-ply board structures laminated with polyurethane adhesives compared to those with reinforcement. The 3-ply board structure without reinforcement had the highest flexural modulus when the urea-formaldehyde resin adhesive was used.

• Journal of the Korean Wood Science and Technology
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• 제43권6호
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• pp.861-867
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• 2015

유리섬유 보강적층재의 파괴인성을 평가하기 위하여 Compact tension (CT)형 시험을 실시하였다. 보강재는 직물형 유리섬유와 시트형 유리섬유강화플라스틱을 사용하였으며, 보강적층재는 층재사이에 보강재를 삽입 적층하였다. ASTM D5045에 의거하여 CT형 시험편을 제작하였다. 시험편의 길이는 끝면거리를 고려하여 선정하였으며, 인위적인 노치 끝에 볼트구멍(12 mm, 16 mm, 20 mm)을 선공하였다. 시트형 유리섬유강화플라스틱 보강적층재의 파괴인성하중은 보강하지 않은 적층재보다 최대 33% 증가하였으며, 직물형 유리섬유 보강적층재는 최대 152% 증가하였다. 이중외팔보(Double Cantilever Beam)이론에 의한 응력확대계수는 시트형 유리섬유강화플라스틱 보강적층재의 경우 1.08~1.38이었으며, 직물형 유리섬유 보강적층재는 1.38~1.86이었다. 이는 직물형 유리섬유 보강적층재의 경우 유리섬유와 층재의 섬유배열방향이 직교하여 파괴하중으로 인한 목재의 할렬진행을 억제시켰기 때문이다.

• 한국가구학회지
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• 제23권1호
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• pp.68-74
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• 2012

In this study domestic thinning and small diameter woods of Giant dogwood (Cornus controversa Hemsl) was used. To increase the utilizability of wood, the utilizability was proposed after manufacturing laminated wood by pressing and heating. The physical and mechanical characteristics of Laminated wood were investigated and the color change was measured, using a Chromaticity coordinates, after being pressed at 10% (45 mm), 20% (40 mm), 30% (35 mm) for 5 minutes, using Stopper, and then heated at $180^{\circ}C$ for 6, 12, 24 and 48 hours. The results were as follows. Wood density, compressive strength, MOR, MOE are increased with increasing pressing rate but decreased as heating time is increased after pressing. However, Color change is clear, dimensional stability is improved after pressing and heating.

• Journal of the Korean Wood Science and Technology
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• 제45권6호
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• pp.746-752
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• 2017

Cross-laminated timber (CLT) is a relatively new engineered wood for timber construction. It is a great shear wall material. It was known that the shear performance of the CLT wall depends on the performance of connections. In connection, nail or screw has to be installed with a certain distance from the end of the timber. Current building code specifies the distance on the name of end distance. The end distance was decided as a minimum distance not to make splitting or tearing out in lumber or glued laminated timber. As a relatively new engineered wood, the end distance of CLT connection need to be identified because CLT is cross-wisely glued lumber products like plywood. Different from glued laminated timber or lumber, cross layer of CLT may prevent wood from splitting or tearing-out. As a result, the end distance of CLT was expected to be reduced than glued laminated timber. The shorter end distance may let more versatile connector design possible. In this study, prior to developing novel connection for CLT, the end distance of CLT connection was experimentally investigated to identify the end distance limitation. The experiments showed that the end distance can be reduced from 7D to 6D, in case of the tested CLT combination and screw in this study.

• 한국가구학회지
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• 제18권1호
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• pp.20-30
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• 2007

This experiment was carried out to investigate the effects of number and location of finger joints on the bending strength of glue-laminated lumbers. Urea resin adhesives were used in this experiment and the resin content was 70% for cold pressing. The lamina were edge-jointed and end-jointed. The specimen were composed of one or three layers. The obtained results are summarized as follows; The effects of finger joints on the decrease of bending strength of glue laminated woods were different according to the number and location of finger joints. The decrease of MOR was highest on the middle position of laminated woods. The effects of several arrangements of finger joints on the bending strength of glue laminated woods showed on Figure 7 and 8. The variance of thickness-laminating on the bending strength of glue laminated woods were larger than those of width-laminating.