Wood and Fiber Science (E-Journal)
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Tensile and Bending Moment Resistances of T-Shaped Joints in Rattan Chairs
Get PDFEffects of inner fastener type, wrapping pattern and material type, and member material type on ultimate tensile and bending moment resistances of T-shaped joints in rattan chair construction were investigated based on the L9 (34) orthogonal array experimental design. The range analyses indicated that the order of impact on ultimate tensile loads of four factors was inner fastener type > wrapping pattern > member material type > wrapping material type, whereas the order of impact on ultimate bending moment was inner fastener type > wrapping material type > wrapping pattern > member material type. Analysis of variance indicated that inner fastener type affected ultimate tensile and bending moment the most among the four factors with percentages of contribution of 51.19 and 47.06 to tensile and bending moment, respectively. Optimal combinations of factors and their levels that yielded the highest ultimate tensile and bending moment resistances were identified for T-shaped, end-to-side joints in rattan materials
Technical Note: Potential to Use Shape Memory Alloy in Timber Dowel-Type Connections
No full textThe aim of this article is to demonstrate the potential of using shape memory alloy (SMA) as a dowel in timber connection to provide a recenterable effect and higher energy dissipation capacity. Two dowel-type timber connections were fabricated for double shear tests under cyclic loadings. The results not only showed that the timber connection with SMA dowel has a good recentering effect, but also has a higher energy dissipation capacity that will outperform the steel-doweled connection in the long term and constant vibration in structures. This article also calls for the need to investigate how this system can be used in conjunction with normal steel dowels and to develop a stronger SMA to satisfy the strength and stiffness requirements of timber connections
Effects of pH on Lap-Shear Strength for Aspen Veneer
No full textThis study is one part of a whole project called "Impact of Extreme pH of Structural Adhesives on Bond Durability." The objective of this study was to evaluate effects of pH on wood-adhesive bond strength and chemical change in aspen (Populus tremuloides Michx) wood caused by extreme pH exposures. Aspen veneer lap-shear samples were tested for maximum stress (N/mm2) and wood failure (%) after exposure to soaking in different buffered solutions (pH = 2.0, 2.5, 3.0; water, 10.0, 11.0, 11.5, 12.0, and 12.5) for 1, 4, and 7 mo. One set of samples stored in laboratory conditions was also tested as a control at each test time. Results indicated that bond strength and wood failure decreased after 4- and 7-mo exposures to acidic conditions but did not change significantly under alkaline exposures. However, the buffered acidic solutions (pH = 2.0 and 3.0) did not cause a measurable chemical change in aspen wood, whereas losses in hemicellulose and lignin were found after aspen wood specimens had been exposed to pH > 11.0 buffered solutions
EFfect of Adhesive Type and Tenon Size on Bending Moment Capacity and Rigidity of T-Shaped Furniture Joints Constructed of Turkish Beech and Scots Pine
No full textTests were carried out to determine the effect of wood species, adhesive type, and tenon width and length on static bending moment capacity and rigidity of T-shaped mortise and tenon furniture joints. For this purpose, 320 round-edged mortise and tenon joint specimens were constructed—half of Scots pine (Pinus sylvestris L.) and half of Turkish beech (Fagus orieantalis L.)—and subjected to static bending loads. Tenons varied 30-60 mm wide and 20-45 mm long. Joint specimens were assembled with 65% solid polyvinyl acetate and polyurethane adhesives. Results of the tests indicated that the joints became stronger and stiffer as either tenon width or tenon length increased. Results also indicated that tenon length had a more significant effect on moment capacity of joints than tenon width, whereas tenon width had a more significant effect on joint rigidity than tenon length. Bending moment capacity of the joints ranged from a low of 125 Nm for joints with tenons 30 mm wide x 20 mm long to a maximum of 393 Nm for joints with tenons 60 mm wide x 45 mm long. Rigidity of the joints ranged from a low of 2278 Nm/rad for joints with tenons 30 mm wide x 20 mm long to a maximum of 5733 Nm/rad for joints with tenons 60 mm wide x 40 mm long. An empirically derived expression was developed to predict average ultimate bending moment capacity
Technical Note: Anatomical Variability within a Loblolly Pine Tree under Thinning Management
No full textDensity, ring width, and cell structure were analyzed at different sampling heights and growth ring numbers in a loblolly pine (Pinus taeda) tree under thinning management. Density, latewood percentage, cell length, and latewood cell wall thickness increased with growth ring number. Tracheid length, latewood tangential cell wall thickness, and earlywood radial cell diameter increased with height. Density, ring width, latewood percentage, cell length, and latewood cell wall thickness increased after thinning treatment. With more information on anatomical properties associated with growth ring number, height, and thinning treatment, wood resources can be more efficiently oriented toward end-use products
Acoustic Sorting Models for Improved Log Segregation
Get PDFIn this study, we examined three individual log measures (acoustic velocity, log diameter, and log vertical position in a tree) for their ability to predict average modulus of elasticity (MOE) and grade yield of structural lumber obtained from Douglas-fir (Pseudotsuga menziesii [Mirb. Franco]) logs. We found that log acoustic velocity only had a moderate correlation with average MOE of the lumber produced from the logs (R2 = 0.40). Log diameter had a weak correlation with average lumber MOE (R2 = 0.12). Log vertical position in a tree was found to have a relatively good relationship with lumber MOE (R2 = 0.57). Our analysis also indicated that the combinations of log acoustic velocity and log diameter or log acoustic velocity and log position were better predictors of average lumber MOE and lumber visual grade yield than log acoustic velocity alone. For sorting best quality logs, multivariable models were more effective than the velocity-alone model; however, for sorting poorest quality logs, the velocity-alone model was as effective as multivariable models
Goodness-of-Fit for Mechanical Properties Distribution of Larch
Get PDFSix different probability distributions, Johnson's SB, 2p-lognormal, 3p-lognormal, normal, 2p-Weibull, and 3p-Weibull, were used for testing their relative goodness of fit in describing modulus of rupture (MOR), modulus of elasticity (MOE), ultimate tension strength (UTS), and ultimate compression strength (UCS) of larch (Larix gmelini) dimension lumber. The populations of lumber consisted of 80 data sets with different mechanical properties, sizes, and structural grades. The Kolmogorov-Smirnov test was selected to be the goodness-of-fit criteria in this study. The 5- and 50-percentile values of these four different mechanical properties of larch lumber were estimated using both the inverse function of various distribution functions and the nonparametric method. Results indicated that 3p-lognormal was the optimal function in describing MOE of larch lumber. The 5- and 50-percentile estimations using the inverse function of 3p-lognormal were the closest values derived through the nonparametric method. Johnson's SB was the best one in describing MOR, UTS, and UCS. The 5- and 50-percentile estimations using the inverse function of Johnson's SB were the closest values derived with the nonparametric method. The distributions of these four mechanical properties of larch lumber were independent of the structural grade and size
Surface Free Energy of Blue-Stained Southern Pine Sapwood from Bark Beetle-Attacked Trees
Get PDFBlue-stained wood cut from bark beetle-attacked southern pine has a lower economic value than unstained wood. Wood composite products containing blue-stained wood may offer an opportunity to recover some lost timber value. This study investigated the surface-free energy of blue-stained wood. Southern pine sapwood samples with and without blue stain from both green and kiln-dried sources were obtained. Dynamic contact angle analyses were performed using three probe liquids: ethylene glycol, formamide, and deionized water. Surface-free energy was determined by applying the geometric mean model using two-liquid pairs with deionized water. The polar forces were higher across all wood types and in water-ethylene glycol vs water-formamide. Surface-free energy of air-dried blue-stained sapwood was lower than all other wood types. However, kiln-dried blue-stained sapwood had a higher surface-free energy than all other wood types. These results were indicative of a tree's wound response to bark beetle attack, the volatilization of naturally occurring hydrocarbons in southern pine sapwood, and the resulting increase in wood permeability caused by blue-stained fungal colonization across the sapwood. However, improvements in wetting observed for kiln-dried blue-stained sapwood may lead to cost and quality issues in wood composite manufacturing associated with overdrying and overpenetration of an adhesive
