Wood and Fiber Science (E-Journal)
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Ring Characteristics and Compressive Strength of Japanese Cedar Trees Grown Under Different Silvicultural Treatments
Get PDFThe effects of different plantation spacings and thinning treatments on the ring characteristics, compressive strength, and dynamic modulus of elasticity (DMOE) of Japanese cedar (Cryptomeria japonica) trees were investigated. The results revealed that young trees of more-closely spaced plantations (3000 trees/ha) had higher wood density and compressive strength than those of more-widely spaced plantations (2200 trees/ha). Different (first and second) thinning treatments of the 2 initial spacings had little effect on ring characteristics or compressive strength. Overall, the average ring characteristics, compressive strength, and DMOE of 35-yr-old Japanese cedar at different plantation spacings and thinning treatments showed no statistically significant differences. The results suggest that using these silvicultural treatments with a longer rotation age will have no detrimental effects on the wood density, compressive strength, or DMOE
Wood-Adhesive Interface Characterization And Modeling In Engineered Wood Flooring
Get PDFAdhesive films used in layered wood-based composites have a significant impact on moisture movement and must be considered in models of such products. The objective of this study was to characterize the wood-adhesive interface and determine its impact on the hygromechanical behavior of engineered wood flooring (EWF). The radial water vapor diffusion coefficient and the coefficients of moisture expansion were determined for sugar maple wood, crosslinked polyviny1 acetate adhesive film (XPVAc), and the wood-adhesive interface. Sugar maple wood had the highest diffusion coefficient at 1.66 x 10-11 m2 · s-1 followed by the wood-adhesive interface at 5.73 x 10-12 m2 · s-1, and the free XPVAc film at 4.18 x 10-12 m2 · s-1. The coefficient of tangential moisture expansion of the sugar maple wood-adhesive interface was found to be 4 x 10-3 (%MC)-1 compared with 3 x 10-3 (%MC)-1 for sugar maple wood in the tangential direction, and 3 x 10-3 (%MC)-1 for the XPVAc film. Finite element modeling of EWF hygromechanical cupping did not show significant differences between hygromechanical cupping calculated with and without interface effects
The Immediate Effect of Temperature on the Modulus of Elasticity of Green and Dry Lumber1
Get PDFThis study evaluated the immediate (reversible) effect of temperature on flexural modulus of elasticity (MOE) of green and dry nominal 2x4 (standard 38 by 89 mm) structural lumber from 66 to -26°C. For lumber at 4 and 12% moisture content (MC), a linear relationship was used to relate the increase in MOE to decreases in temperature. For green lumber, MOE also increased with decreasing temperature. A segmented linear regression was developed to describe the change in MOE of green lumber for 66 to -18°C. The slope of this relationship was steeper below 0°C than above. The actual MC of green lumber was not a factor above -18°C. Below this temperature, the increase in MOE with decreasing temperature was a function of both actual green MC and temperature. We discuss factors that cause this behavior in green wood at low temperatures and the use of an empirical model for describing the MOE-temperature relationship as a function of MC for frozen green lumber
Analysis, Design, and Performance Testing of a Gate-Leg Table
Get PDFGate-leg tables behave differently from conventional tables and have not been studied extensively. To determine the distribution of moments in the main and side frames, structural analyses were conducted on a gate-leg table under different loading scenarios. Potential weak construction points were identified. Back-to-front load performance tests of the tables constructed with mortise-and-tenon and dowel joints were performed and compared. Results show that the strength of mortise-and-tenon joints is superior to the strength of dowel joints. The tables constructed with mortise-and-tenon joints would be ranked just below the "medium-duty" performance level, whereas tables constructed with dowel joints would be ranked just above "light-duty." Strength of dowel joints was closely related to the length of the dowels. Finally, ultimate strength tests were conducted on undamaged joints cut from the frames following the performance testing to determine their in-plane, out-of-plane, and torsional moment capacities. Substantially higher values were obtained for the mortise-and-tenon joints
Environmental Impact of Producing Hardwood Lumber Using Life-Cycle Inventory
Get PDFUsing sustainable building materials is gaining a significant presence in the US. This study examined hardwood lumber manufacturing using life-cycle inventory methodology. Material flow and energy use were identified for hardwood sawmills in northeastern US. A hardwood log volume conversion of 43.7% to planed dry lumber was found. Values of 608 MJ/m3 of electrical and 5800 MJ/m3 of thermal energy were determined for the manufacturing of planed dry hardwood lumber where mostly green wood residues were burned on-site for energy. Emission data produced from modeling estimated biomass and fossil CO2 production of 428 and 139 kg/m3, respectively. Increasing wood fuel use, a carbon-neutral process, would lower the environmental impact of hardwood lumber manufacturing and increase its use as a green building material
Experimental Equilibrium Moisture Content of Wood Under Vacuum
Get PDFWood equilibrium moisture content (EMC) was measured under vacuum by an electronic method. A wafer was used to measure EMC using an in-house designed vacuum instrument. EMC at 4 to 100 kPa and temperature from 30 to 90°C were measured. The relationships among temperature, pressure, and EMC were determined, and a diagram of wood EMC was produced. The results showed there are obvious differences between experimental EMC values obtained and theoretical EMC values of other researchers. It is suggested that corrections should be introduced into theoretical models or a new model for the vacuum condition developed
Theoretical Modeling of Bonding Characteristics and Performance of Wood Composites. Part IV. Internal Bond Strength
Get PDFA mechanistic model was developed to predict the internal bond (IB) strength of wood composites. Based on the earlier models reported in this series, the IB model integrates the mechanisms of inter-element contact, resin distribution, and localized bond development and debonding failure. Experimental tests were also conducted, and the results compare favorably with model predictions. It was discovered that a composite product having large horizontal density variations typically realizes less than 50% of the bond strength attainable between its constituent elements. The loss of bonding strength is attributed to the premature debonding of low-density regions, and the subsequent load concentration and failure-acceleration of the higher-density regions. The model predicts IB as a function of product density, wood density, resin content, and element dimensions. The IB improves with an increase of product density, resin content, and element thickness. The relationships are monotonic and nonlinear, resulting from their interactions on the contact development or/and the resin coverage. The relationship between IB and wood density is also nonlinear and dependent upon the product density. Implications of the predictive results on fundamental understanding and optimization of wood composite bonding are discussed
Some Observations of Wood Density and Anatomical Properties in A Douglas-Fir Sample with Suppressed Growth
Get PDFThis study used ring width correlations to examine the effects of tree-growth suppression on within-tree local wood density and tracheid anatomical properties. A wood core sample was taken from a 70-yr-old Douglas-fir that grew under various degrees of suppression in a natural forest setting. SilviScan and an imaging technique were used to obtain wood density and tracheid cross-section dimensions. The results indicated that wood and tracheid properties correlate to annual-ring width very well. The results also reveal that growth suppression may increase the uniformity of wood density and tracheid cell-wall thickness in both radial and tangential directions
The Influence of Cutting-Bill Requirements on Lumber Yield Using a Fractional-Factorial Design Part I. Linearity and Least Squares
Get PDFThe importance of lumber yield on the financial success of secondary solid wood products manufacturers has been known for quite some time. Various efforts have been undertaken to improve yield, such as inclusion of character marks (defects) in parts, "cookie-cutting" of boards, improved optimization algorithms, or improved cut-up technologies. For a variety of reasons, the relationship between cutting-bill requirements and lumber yield has attracted limited attention. This is Part I of a 2-part examination of this relationship.The standardized and simplified Buehlmann cutting bill and the Forest Service's Romi-Rip lumber cut-up simulator were used in this study. An orthogonal, 220-11 fractional-factorial design of resolution V was used to determine the influence of different part sizes on lumber yield. All 20 part sizes contained in the cutting bill and 113 of a total of 190 unique secondary interactions were found to be significant variables in explaining the variability in observed yield. Parameter estimates for the part sizes and the secondary interactions were used to specify the average yield contribution of each variable. Parts 445 mm long and 64 mm wide were found to have the most positive influence on yield. Parts smaller than 445 by 64 mm (such as, for example 254 by 64 mm) had a less pronounced positive yield effect because their quantity requirement is relatively small in an average cutting bill. Thus, the quantity required is obtained quickly during the cut-up process. Parts with size 1842 by 108 mm, on the other hand, had the most negative influence on high yield. However, as further analysis showed, not only the individual parts required by a cutting bill, but also their interaction determines yield. In general, it was found that by adding a sufficiently large number of smaller parts to a cutting bill that required large parts, high levels of yield can be achieved