• Journal of the Korean Wood Science and Technology
• /
• v.33 no.5 s.133
• /
• pp.13-20
• /
• 2005

This paper deals with flexural vibration techniques as a means of predicting bending strength properties for quarter-sawn and flat-sawn planes of red pine containing knots. Dynamic modulus of elasticity $(MOE_d)$ was calculated from resonance frequency obtained from the flexural vibration induced by a magnetic driver in quarter-sawn and flat-sawn planes of red pine containing knots. The dynamic MOE were well correlated to bending strength properties. Their correlation coefficients ranged from 0.866 to 0.800 for the regression between dynamic MOE and static bending MOE or MOR. The difference of the values between quarter-sawn and flat-sawn was very small. These values were higher than correlation between percentage of total knot diameter to total width of red pine specimen $(K_T(%))$ as well as $K_O(%)$ base upon ASTM D 3737 and static bending strength properties (correlation coefficient r = 0.448~0.704), and were similar to those between static bending MOE and bending MOR (r = 0.850). These results indicate that dynamic MOE obtained from resonance frequency induced by flexural vibration of magnetic driver is able to effectively use for predicting of static bending strength of red pine containing knots as well as static MOE.

• Archives of design research
• /
• v.18 no.4 s.62
• /
• pp.155-164
• /
• 2005

In contrast with product design field, some designers who work in furniture field tend to do their own studio works as well as typical designing part. Especially in the small furniture studios for the limited quantity batch production, custom made or handmade craft furniture which is finished with high quality, the propensity for their own production is more obvious than in the big furniture companies in this case. In this kind of small-scale furniture studios, they have more chance to create the various formative works and 'curved shape' is one of the most important elements to form creative pieces. Except by caning, it is very difficult to make curved wooden shape because of own characteristic of wood. Therefore, the special techniques of bending wood are essential to formative furniture production and vacuum press system is introduced as a main subject for the bending wood method in this study. Especially for the designers who work as makers as well at the small furniture studios, the value of vacuum press system on efficiency and productivity of work was sought by testing and improving the method of wood bending techniques. According to this practical searching, ideally sufficient condition on vacuum pressing work was founded as a result on this study.

• Journal of the Korean Wood Science and Technology
• /
• v.38 no.6
• /
• pp.457-462
• /
• 2010

Sound absorption capability and bending strength of laminated ship-building plywood waste of maple and melanti wood were estimated. Sound absorption coefficients of wood had been measured by the two microphone transfer function method and bending strength examined by three point loading. The maximum strength in bending of laminated ship-building plywood waste of maple and melanti wood were 534 and 414 kgf/$cm^2$, respectively. The sound absorption coefficients of laminated ship-building plywood waste were higher than mongolian oak and fiber board, well used construction material. Especially, in the case of laminated ship-building plywood waste of melanti wood, average sound absorption coefficient was about 0.25. It was surmised that the laminated ship-building plywood waste can be used as interior materials because of its good mechanical and sound absorption properties.

• Journal of the Korean Wood Science and Technology
• /
• v.31 no.5
• /
• pp.23-34
• /
• 2003

This study was carried out to investigate the mechanical properties of fabric E-glass fiber reinforced laminated timber. Specimens used to Korean red pine(Pinus densiflora) and Japanese larch(Larix kaemferi). Fabric E-glass fiber was inserted in the solid wood with aqueous polymer-isocyanate resin(MPU-500). The results were as follows: 1. Aqueous polymer-isocyanate resin(MPU-500) was good resin to manufacture laminated timber. specially, it was satisfied to property standard of construction laminated timber(KS F 3021) except for two ply glass fiber. 2. Bending and shear strengths of solid wood inserted with fabric glass fibers were not different from control solid wood. But, proportional limit bending stress was increased following the number of fabric glass fibers. Therefore, it was considered that to improve the bending and shear strength of fabric glass fiber reinforced laminated timber, the glass fiber thickness and its mesh should be modified to fitness following working conditions.

• Journal of the Korea Furniture Society
• /
• v.15 no.2
• /
• pp.19-27
• /
• 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
• /
• v.26 no.4
• /
• pp.13-19
• /
• 1998

Stress relaxation tests have been performed under five different tensile strain levels and five different bending strain levels. Three different theoretical models have been developed based on four-element Burger's model, viscoelastic theory and viscous-viscoelastic theory. Experimental data were used to obtain parameters of the models and to verify accuracy of the models. Among the three theoretical models developed in this study, three-integral model (Model 3) based on viscous-viscoelastic theory showed the most exact estimations of stress relaxation under both tensile and bending strains and their correlation coefficients were greater than 0.99 for all the strain levels. Model 1 showed little initial stress relaxation. Model 2 showed excessive initial relaxation and, then, no relaxation after about 20 minute of strain application. Stress retention under strain decreased as strain increased, which means increased stress relaxation as strain increases. When the strain level was less than proportional limit, the effect of strain level on stress relaxation was not clearly shown. However, this effect was increased as strain level increased when strain level was greater than proportional limit.

• Journal of the Korea Furniture Society
• /
• v.11 no.2
• /
• pp.67-72
• /
• 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.

• Steel and Composite Structures
• /
• v.19 no.3
• /
• pp.585-599
• /
• 2015

This paper presents the experimental work on fatigue life and specific fatigue strength of circular hollow sectioned steel tube and wood filled circular hollow section steel tube. Burning effect was observed in the case of circular hollow sectioned steel tube when it is subjected to Maximum bending moment of 19613.30 N-mm at 4200 rpm, but this did not happen in the case of wood filled hollow section. Statistical analysis was done based on the experimental data and relations have been built to predict the number of cycles for the applied stress or vice versa. The relations built in this paper can safely be applied for design of the fatigue life or fatigue strength of circular hollow sections and wood filled hollow sections. Results were validated by static specific bending strengths determined by ANSYS using a known applied load.

• Journal of the Korean Wood Science and Technology
• /
• v.25 no.4
• /
• pp.29-38
• /
• 1997

The effect and control of wood property of reconstituted composite panels for improved board properties by wood-waste materials and development of combination method for heterogeneous materials have been of interest to the wood science researchers. The purpose of this study is to consider the properties in relation to hot pressing conditions and to develope the optimum hot pressing condition with waste wood and waste tire for the manufacturing of composite boards. The study of composite boards for recycling of wood and waste tire is nothing up to the present. Physical and mechanical properties such as specific gravity, moisture content, swelling coefficient, modulus of rupture and modulus of elasticity in bending test were studied. The condition of 3-stage press time for the lowest moisture content of composite board was $4{\rightarrow}3{\rightarrow}3$ minutes. Specific gravity of composite panels was affected mainly by the amount of rubber chip. Because of the low rigidity and high elasticity in rubber chip, it is considered the composite panel was adequate material in the place of compression load, but not bending load. Therefore, it was concluded that a use of rubber-based wood composite panel is proper to the interior materials such as floor a room than exterior materials. From the test results, the most optimum hot pressing conditions were $4{\rightarrow}3{\rightarrow}3$ minutes for 3-stage press time and $45{\rightarrow}20{\rightarrow}5kg/cm^2$ for 3-stage press pressure. The rubber-based wood composite panel was very excellent in elasticity by combination of rubber chip in comparison with existing other wood-based materials. Therefore, it was considered that rubber-based wood composites can be applicable to every interior materials such as floor a room and will be expected to effective reuse and recycle of waste tires and wood-waste materials, and will be contribute to protection of environment pollution in earth.

• Journal of the Korean Wood Science and Technology
• /
• v.29 no.3
• /
• pp.47-58
• /
• 2001

For finding both ways of recycling the wood and plastic wastes and solving the problem of free formaldehyde gas emission through manufacturing wood particle-polypropylene fiber composite board without addition of formaldehyde-based thermosetting resin adhesive, control particleboards and nonwoven web composite boards from wood particle and polypropylene fiber formulation of 50 : 50, 60 : 40, and 70 : 30 were manufactured at density levels of 0.5, 0.6, 0.7, and 0.8 g/$cm^3$, and were tested both in the physical and mechanical properties according to ASTM D 1037-93. In the physical properties, control particleboard had significantly higher moisture content than composite board. In composite board, moisture content decreased with the increase of target density only in the board with higher content of polypropylene fiber and also appeared to increase with the increase of wood particle content at a given target density. Control particleboard showed significantly greater water absorption than composite board and its water absorption decreased with the increase of target density. In composite board, water absorption decreased with the increase of target density at a given formulation but increased with the increase of wood particle content at a given target density. After 2 and 24 hours immersion, control particleboard was significantly higher in thickness swelling than composite board and its thickness swelling increased with the increase of target density. In composite board, thickness swelling did not vary significantly with the target density at a given formulation but its thickness swelling increased as wood particle content increased at a given target density. Static bending MOR and MOE under dry and wet conditions increased with the increase of target density at a given formulation of wood particle and polypropylene fiber. Especially, the MOR and MOE under wet condition were considerably larger in composite board than in control particleboard. In general, composite board showed superior bending strength properties to control particleboard, And the composite board made from wood particle and polypropylene fiber formulation of 50 : 50 at target density of 0.8 g/$cm^3$ exhibited the greatest bending strength properties. Though problems in uniform mixing and strong binding of wood particle with polypropylene fiber are unavoidable due to their extremely different shape and polarity, wood particle-polypropylene fiber composite boards with higher performance, as a potential substitute for the commercial particleboards, could be made just by controlling processing variables.