Wood and Fiber Science (E-Journal)
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Determination of Internal Moisture Transport and Surface Emission Coefficients for Eastern White Pine
Get PDFMoisture movement in eastern white pine wood specimens was evaluated during drying at specific temperature and RH conditions. The objective of this work was to build an appropriate numeric analysis model for predicting moisture profile changes in wood and apply this to the kiln-drying of large cross-section eastern white pine timbers. The internal moisture transport coefficients were dependent on the temperature and average moisture content, and the surface emission coefficients on the water vapor pressure in air adjacent to the surface. The internal moisture transport coefficients decreased with decreasing temperature and internal moisture content. Surface emission coefficients increased with increasing temperature and decreasing surface moisture content
Impact of Mountain Pine Beetle (MPB) Attack on Drying Characteristics of Wood
Get PDFMountain pine beetle infested lodgepole pine (Pinus contorta var. latifolia) containing blue stain was used for the determination of permeability and diffusion coefficients. The results were then compared with the permeability and diffusion coefficients of noninfested wood that was free from the blue stain. The comparisons indicated that the blue stain in wood significantly increased the permeability of lodgepole pine, in both tangential and radial directions. Diffusion coefficients for blue-stained sapwood were greater than those observed for nonstained sapwood
Structure and Performance of Spinning Solution Prepared from Liquefied Wood
Get PDFA new spinning solution was synthesized from liquefied wood in phenol by adding hexamethylenetetramine (HMTA) as a synthesis agent, and was easily spun into fibers by melt-spinning. Structure evolution of the spinning solution from liquefied wood (LWS) was investigated by FTIR spectroscopy. Results show the functional groups of LWS were changed from that of liquefied wood by adding HMTA during synthesizing the spinning solution. The effects of various synthesis conditions on the properties of the spun fibers are discussed. Spun fibers with a tensile strength of 90-129 MPa and modulus of elasticity of 8-24 GPa were obtained at a phenol/wood ratio of 6, synthesis agent content of 5%, synthesis temperature of 120°C, and temperature-rising time of 40 min. It was also found that thermal stability of LWS is better than that of liquefied wood, and that the spun fibers from LWS could be a precursor for carbon fibers
A Model of Knot Shape and Volume in Loblolly Pine Trees
Get PDFThe shape and structure of branches attached internally to the stem (knots) for loblolly pine (Pinus taeda L.) trees were modeled. Data on knot shape were obtained from the dissection of branches taken from 34 22-yr-old sample trees growing under ten different initial spacings. A total of 341 branches located below the live crown were dissected in the radial/tangential plane. Afterward, a procedure was implemented to reconstruct the branch diameter perpendicular to the branch pith. This information was used to develop a model for representing knot shape, which assumed that the live portion of a knot can be modeled with a one-parameter equation and the dead portion by assuming a cylindrical shape. To study the variability in shape of individual knots (live portion), the model was fitted to 218 branch profiles using nonlinear mixed-effects modeling techniques. A graphical analysis indicated that the random-effects parameter was related to branch diameter. Thus, branch diameter was included as a predictor variable to reduce between-individual variability in knot shape. Reconstructed knots with smaller diameters were more cylindrical; those with larger diameters were more parabolic or conical in shape. Analytical expressions were derived for estimating the volume of knots (live/dead portions) for three types of branch conditions on simulated trees: 1) live branches; 2) nonoccluded dead branches; and 3) occluded dead branches. The knot model assumes a substantial simplification of branch morphology, but should be useful for representing knots as 3-D entities in the stems of loblolly pine trees
Estimating Biomass Yield for Sub-Merchantable Ponderosa Pine of Northcentral Colorado
Get PDFVolume, mass, and moisture content data were collected for 28 sub-merchantable ponderosa pine trees harvested in northcentral Colorado. The average green bulk density of these trees was 280 kg/m3. The average oven-dry bulk density was 169 kg/m3. Average green moisture content (oven-dry mass basis) was 91%. A multiple regression analysis was conducted using diameter at breast height (DBH), tree height, and crown vigor class to identify which of these variables could be used to predict biomass yield (oven-dry tree mass). Based on an analysis of variance at α = 0.05 level-of-significance, only DBH was a significant predictor of oven-dry tree mass. Therefore, oven-dry mass estimates were calculated based on a regression line fitted to ln(oven-dry mass) vs ln(DBH) data. The R-square value for the regression line was 0.897. Although differences between actual and predicted oven-dry tree mass ranged up to 57.8%, the average difference was 2.9%
Mode II Fracture Behavior of Bonded Viscoelastic Thermal Compressed Wood
Get PDFThe influence of viscoelastic thermal compression (VTC) of wood on bonding performance was studied. Mode-II (shear mode) fracture of the bonded interphase was performed using the over-notched and end-notched flexure methods. The study examined four groups of specimens; a control and VTC specimens with three different degrees of densification (63, 98, and 132%). The specimens were bonded with phenol-formaldehyde (PF) adhesive. Prior to fracture testing, the bonded interphase was examined and the effective penetration (EP) of PF into the capillary structure of wood was measured. The results showed that EP was greatest in the control wood specimens, but in the case of the VTC specimens decreased with increasing degree of densification. The mode-II fracture performance of the VTC wood specimens with PF differed from the control wood specimens. In the control specimens, the mode-II crack propagation occurred in the interphase, while in the VTC specimens the crack diverted away from the interphase into the VTC wood. A hypothesis of relative shear resistance was used to explain the bonding performance of the control and VTC specimens
Assessment of Longitudinal Shrinkage and Swelling Using the APA and ASTM Methods
Get PDFThe APA and ASTM methods of measuring longitudinal shrinkage and swelling were evaluated and compared using radiata pine coupons with a wide range of wood properties and different operators. The two methods gave different measurements of longitudinal shrinkage and swelling as a result of differences in the location of the measurement points, and the ability to correct for out-of-plane distortion. The APA method gave more precise measurements from the use of inserted brass eyelets and the correction of out-of-plane distortion with a vacuum table. The measurements were not affected by wood type or operator. The ASTM method was found to be sensitive to the condition of the transverse surface at the measurement point and to the presence of drying distortion. The measurements varied in response to wood type and operator. The results indicate the APA method is more precise for measuring longitudinal shrinkage and swelling when measurements are made in series along boards and cants
Finite Element Modeling of Small-Scale Tapered Wood-Laminated Composite Poles with Biomimicry Features1
Get PDFTapered composite poles with biomimicry features as in bamboo are a new generation of wood laminated composite poles that may some day be considered as an alternative to solid wood poles that are widely used in the transmission and telecommunication fields. Five finite element models were developed with ANSYS to predict and assess the performance of five types of composites members: a tapered hollow pole with webs (Pole-A), a tapered hollow pole without webs (Pole-B), a tapered solid composite pole (Pole-C), a uniform-diameter hollow pole with webs (Pole-D), and a uniform-diameter hollow pole without webs (Pole-E). The predicted deflection by these models agreed well with those of the experiment, and the predicted normal stress agreed with those calculated. The normal and shear stress distributions inside the members were investigated, and stress distributions in the XY and YZ planes are exhibited. As expected, the webs reduced the local shear stress and improved shear capacity, especially in the top and groundline regions where shear levels were the highest. The webs had little effect on the normal stress. Shear stress increased from the bottom to the top for the members with taper. Large shear stress concentration was predicted in a small region close to the groundlines. The models also predicted that the shear stress of the tapered hollow poles would decrease from the inside to the outside surfaces in XY plane
Estimating Preservative Release From Treated wood Exposed to Precipitation1
Get PDFAccelerated leaching methods are needed to better estimate emissions from treated wood used above ground or above water. In this study, we evaluated leaching methods using continuous immersion, dip immersion, and simulated rainfall approaches. Copper and/or boron emissions were measured for specimens treated with either chromated copper arsenate Type C (CCA-C) or a borax-copper (BC) preservative. The results of these leaching tests were compared with the extent of wetting and drying within the specimens and with the published reports of leaching and MC under natural exposures. Release per unit surface area was generally greatest with the simulated rainfall or constant immersion methods, but the relationship between the methods was dependent on the leaching characteristics of the specific preservative formulation. The lowest emissions were found for small specimens exposed to dip immersions. Comparison of the simulated rainfall results to published values indicates that the rainfall method and dip immersion scenarios underestimate copper release from wood exposed outdoors, and that the methods evaluated do not adequately simulate the wetting and drying conditions encountered in natural exposures. Further research is needed to better characterize the wetting and drying of in-service treated wood and to adapt test methods to more closely simulate these conditions
Synthesis and Evaluation of Aminoborates Derived from Boric Acid and Diols for Protecting Wood Against Fungal and Thermal Degradation
Get PDFN-methyl amino catechol borate (1), N-methyl amino-4-methyl catechol borate (2), N-methyl amino-4-t-butyl catechol borate (3), and N-methyl amino-2, 3-naphthyl borate (4) were synthesized by reflux of boric acid with a diol in solvent N, N-dimethyl formamide. The aminoborates were characterized by proton nuclear magnetic resonance spectroscopy, FTIR spectroscopy and elemental analysis. Wood impregnated with aminoborate 1, 3, or 4 after 2-wk water leaching was able to prevent decay by a brown-and white-rot fungus. Thermogravimetric analysis showed that wood impregnated with aminoborate 1 or 4 had a high char yield. DSC showed that the pyrolysis pathway of wood treated with aminoborates proceeds by depolymerization of cellulose. Chars formed from wood impregnated with aminoborates were more stable to thermal degradation than the control