• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.32-36
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• 1995

A study was conducted to evaluate the dynamic mechanical properties (modulus of elasticity, resonant frequency and interanal friction) of compression wood in Pinus densiflora. Vibration method was used for estimation of dynamic modulus of elasticity and the values were compared to those of static bending modulus of elasticity. The results obtained are as follows: 1. The dynamic modulus of elasticity of compression wood decreased, whereas that of normal wood increased, with increasing specific gravity. 2. The resonant frequency of compression wood decreased, whereas that of normal wood increased, with increasing specific gravity. 3. The internal friction of compression wood increased with increasing specific gravity. 4. The correlation coefficients between dynamic and static moduli of elasticity in compression and normal woods were high.

• Journal of the Korean Wood Science and Technology
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• v.41 no.5
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• pp.466-473
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• 2013

Nondestructive evaluation (NDE) technique method using a resonance frequency mode was carried out for heat-treated wood under different conditions. The effect of heat treatment on the bending strength and NDE technique using the resonance frequency by impact hammer and force transducer mode 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. There were a close relationship of dynamic modulus of elasticity and static bending modulus of elasticity to MOR. In all conditions, It was found that there were a high correlation at 1% level between dynamic modulus of elasticity and MOR, and static modulus of elasticity and MOR. However, the result indicated that correlation coefficient is higher in dynamic modulus of elasticity to MOR than that in static modulus of elasticity to MOR. Therefore, the dynamic modulus of elasticity using resonance frequency by impact hammer mode is more useful as a nondestructive evaluation method for predicting the MOR of heat-treated wood under different temperature and species conditions.

• Journal of the Korean Wood Science and Technology
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• v.49 no.5
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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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• v.48 no.5
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• pp.696-709
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• 2020

A board was manufactured for each resin and sawdust addition using the chaff made by carbonizing the chaff charcoal, an agricultural by-product that emerge during the rice pounding process, and sawdust. And effects of the additions of resin and sawdust on coefficients of dynamic and static modulus of elasticity, modulus of rupture, as well as the relationship between the dynamic modulus of elasticity, statis modulus of elasticity, and modulus of rupture were investigated. As phenol resin addition of chaff charcoal-sawdust compound board increases to 10~25%, the bending performance has increased. This suggests that resin addition largely effects the bending performance. Although the bending performance was gradually increased with the increase in sawdust addition, since the coefficients of determination (R²) between the sawdust addition with the coefficients of dynamic, static modulus of elasticity, and modulus of rupture were 0.4012, 0.0809, and 0.1971, respectively. Thus, it showed a relatively lower correlation, and the effect of sawdust on bending performance was small. Since a high correlation was confirmed between dynamic and static modulus of elasticity, and modulus of rupture of chaff charcoal-sawdust compound board, it was confirmed that prediction of static modulus of elasticity and modulus of rupture can be made in a nondestructive way from the dynamic modulus of elasticity.

• Journal of the Korean Wood Science and Technology
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• v.28 no.3
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• pp.1-8
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• 2000

To develop the technology of producing structural board from low grade materials, an attempt was made to produce strand/particle composites from split wood strand(S) and particle(P) of (Cryptomeria japonica D. Don), which changed the layer construction and the ratio of S/P. The influence of layer construction on board properties was determined, focusing on the number and alignment of the S layers. The effect of weight ratio of S/P (3:7, 1:1, 7:3) on mechanical properties was also discussed on seven layered panel. Mechanical properties were determined from static bending tests to give parallel and perpendicular modulus of rupture (MOR) and modulus of elasticity (MOE), and the internal bond (IB) strength. In general, the surface strand layers contributed to the MOR and MOE. The parallel MOR and MOE values were the largest for the single layered S panel (only Slayers: S1), but the perpendicular MOR and MOE was the smallest. Perpendicular MOR and MOE were the largest for seven layered composite that had two cross oriented strand layers (SPSPSPS: SP7). Specimens retained more than half of their MOE and MOR after two hours in boiling water and one hour soaking. IB was the largest for the panel having only P layers, however, differences in IB strength were not identified among the other multi-layered composite panels thus the effect of layer construction on IB strength was small. Thickness swelling (TS) and surface roughness were smaller for the composite having P layers on the surface than for those having S layers. The addition of strands did not enhance the mechanical properties (MOR, MOE, IB). TS values for the panels, with which the S/P ratio was over than 1:1, was the similar to the value for the single layered S panels.

• Journal of the Korea Furniture Society
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• v.11 no.2
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• pp.1-6
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• 2000

This study was carried out to investigate the effect of steaming on mechanical properties of heat-compressed wood specimens. The specimens for this mechanical strength tests were prepared to super-heated steam treatment after compression to the radial direction of sonamu (Pinus densiflora). The specimen's size is $50(L)mm{\times}20(R)mm{\times}17(T)mm$. Steaming temperature and treatment time is $120^{\circ}C$ and 20, 40, 60, 80, 100 minutes, respectively. Modulus of elasticity(MOE) in compressive test is directly proportional to steaming time. On the other hand, modulus of elasticity in bending test between steaming and not steaming after heat-compressed wood is similar irrespective of steaming time. The reason for this phenomenon is not clear yet.

• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.70-76
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• 1995

Research was conducted at the Wood Materials and Engineering Laboratory, Washington State University, Pullman, WA to evaluate the effects of the sequence of wax addition, wax level, and wax type on mechanical properties and water resistance performance of isocyanate-bonded particleboard. Mechanical properties and water resistance performance were not influenced significantly by the sequence of wax addition. Internal bond and wet modulus of rupture in bending strength were decreased significantly by increasing the wax emulsion level, but dry modulus of rupture and modulus of elasticity in bending strength were not decreased significantly by increasing the wax emulsion level. Dry internal bond, dry and wet moduli of rupture, and modulus of elasticity were not decreased by increasing the solid wax level except for wet internal bond. The addition of 1.0 and 1.5% wax level did not produce any significant additional water resistance effect when compared to the addition of 0.5% wax level. Internal bond values of boards with solid wax addition showed significantly better results than boards with just a wax emulsion added. Modulus of rupture, modulus of elasticity, and water resistance performance did not show significant difference between solid wax and wax emulsion.

• International Journal of Reliability and Applications
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• v.8 no.2
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• pp.153-173
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• 2007

Wood-plastic composites (WPC) are gaining market share in the building industry because of durability/maintenance advantages of WPC over traditional wood products and because of the removal of chromated copper arsenate (CCA) pressure-treated wood from the market. In order to ensure continued market share growth, WPC manufacturers need greater focus on reliability, quality, and cost. The reliability methods outlined in this paper can be used to improve the quality of WPC and lower manufacturing costs by reducing raw material inputs and minimizing WPC waste. Statistical methods are described for analyzing stiffness (tangent modulus of elasticity: MOE) and flexural strength (modulus of rupture: MOR) test results on sampled WPC panels. Descriptive statistics, graphs, and reliability plots from these test data are presented and interpreted. Sources of variability in the MOE and MOR of WPC are suggested. The methods outlined may directly benefit WPC manufacturers through a better understanding of strength and stiffness measures, which can lead to process improvements and, ultimately, a superior WPC product with improved reliability, thereby creating greater customer satisfaction.

• Journal of the Korean Wood Science and Technology
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• v.25 no.1
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• pp.42-49
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• 1997

The purpose of this study was to investigate the relationships among density, moisture content, and modulus of elasticity in which are important characteristics in physical and mechanical properties of woods. In this study, the dynamic MOE was calculated through the combination with resonance frequency of transverse vibration method and density, and the estimated moisture contents were calculated with two different equations (1, 2) in order to compare with experimental moisture contents. The following results from this study were obtained: 1. According to the regression analysis with two different parameters (E and density), the two regression lines appeared to be straight intersecting at 0.6 density. As another factor, moisture contents in wood also influenced on the analysing regression at the below F.S.P. 2. When considering the relationship between moisture contents and E, the tendency of each moisture content and E showed very similar pattern suggesting that moisture contents in addition to density are very important parameter. 3. When together with moisture contents and density as parameters for multiple regression analysis, coefficiences of determinations are dramatically improved. Interestingly, the coefficiences of determinations are further increased when analysing at the below point of F.S.P. and when analysing higher and lower density separately. In summary, more correct estimation of the dynamic MOE of woods can be possible with only transverse vibration and density in wood. Therefore, with this indirect method, the calculation of MOE in all kinds of woods including timber, live tree and wood products can be feasible resulting in accelerating the efficiency of time and labor.

• Journal of the Korean Wood Science and Technology
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• v.12 no.2
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• pp.3-9
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• 1984

This study was carried out to examine the practicality of DAP[$(NH_4)_2HPO_4$] as fire retardant for plywood by static bending test the redried plywoods which had been soaked in 20% $(NH_4)_2HPO_4$ solution. Being hot/cold soaked in the solution for 3/3, 6/3, 9/3 and 12/3 hours and redried by cyclic press-drying method at the platen temp. of 130, 145, 100 and $175^{\circ}C$, the treated plywoods were tested to offer the mechanical data, that is, $S_{pl}$(stress at proportional limit), MOE(modulus of elasticity), MOR(modulus of rupture) and $W_{pl}$(work per unit volume to proportional limit ) in flexure. The results obtained were summarized as follows. 1. $S_{pl}$ of fire retardant treated plywoods ("FRP" would be used hereinafter) decreased as the platen temperature increased, but it was superior to that of non-treated plywoods(Control) at $160^{\circ}C$ or higher. 2. MOE of FRP decreased roughly with the increase of temperature, hut this tendency was not constant. And the value of FRP was higher than that of Control even at $175^{\circ}C$. 3. MOR of FRP showed same temperature-dependent tendency as MOE, but it was influenced more sensitively at the higher temperature. 4. $W_{pl}$ of FRP also decreased gradually with the increase of platen temperature and the value in DAP 9/3 treatment was Jess than 70% of control plywoods. 5. In view of redrying time and mechanical properties, the most reasonable platen temperature for DAP treated FRP was $160^{\circ}C$ in this study.