Wood and Fiber Science (E-Journal)
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Biomass and Wood Properties of Young Silver Maple Clones
Get PDFBiomass properties were determined to characterize the differences between young silver maple clones as an energy source or fiber source feedstock. Size varied significantly among 25 maple sources evaluated, but larger trees generally had the better survival, which is highly important in clonal comparisons. Characteristics of the wood were similar to those of soft hardwoods; the mean value of gross heat of combustion was 19.6 kJ/g; the fiber length was relatively short (0.74 mm); the ash content was 0.291; and the specific gravity was 0.43. Clonal differences were significant
Fire-Retardant-Treated Strandboard: Properties and Fire Performance
Get PDFThis study evaluated a series of single-layer, randomly oriented strandboard panels made with one resin type, a single resin loading level, and four fire-retardant-treatment levels. The fire retardant (FR) evaluated was a pH-buffered combination of boric acid and organic phosphate. Siberian larch strands were separated into five batches. One batch of strands served as the untreated control group and was not treated with water or FR; the four other batches were individually treated using a vacuum-pressure-soak process of the strands in water or three progressively higher concentrations of FR solutions. Targeted water- or FR-loading levels were no FR (0% FR-weight gain, water-treated control), 32 kg/m3 FR (~5% weight gain), 64 kg/m3 FR (~10% weight gain), and 96 kg/m3 FR (~15% weight gain). All water- or FR-treated strands were redried to less than 8% moisture content prior to diphenylmethane diisocyanate (MDI) resin application in rotary blenders using an aerosol sprayer. Three replicate specimens for each treatment level of 12.5-mm-thick, randomly oriented strandboard at a density of 650 kg/m3 were evaluated. FR-treated strandboard had higher dry- and wet-internal bond strength and lower flexural strength than matched untreated strandboard. A Class B flame-spread rating was achieved near 10% FR-loading. These results suggest that better ratings seem possible at higher loadings
Effect of Cyclic Long-Term Temperature Exposure on The Bending Strength of Lumber
Get PDFThis research evaluated the historical assumption that repeated exposure to elevated temperatures has a cumulative effect on wood properties. This recommendation was given in a paper by J. D. MacLean in 1951 and is a critical assumption when estimating the permanent effect of temperature on wood properties. No experimental results to support the recommendation were presented by MacLean. Approximately 670 southern pine and Douglas-fir solid-sawn 2x4's of two mechanical grades and one visual grade were subjected to cyclic and continuous exposure at 82°C and 30% RH for periods up to 30 mo. They were then tested after equilibration to room temperature and 20% RH. The cyclic exposure specimens alternated between 1 mo at 82°C and 1 mo at room temperature. The results show that there is no significant difference between the residual modulus of rupture (MOR) of the cyclic and continuously-exposed specimens for equivalent exposure periods. Trends in residual arabinose also supported this conclusion. Plotting the residual MOR of the cyclic specimens as the summation of the time they were exposed to the higher temperature provided a conservative estimate of the permanent effect of temperature. The results discussed in this paper are a small subset of a larger study and are not intended for use in general engineering design
Wood Shrinkage Prediction Using NIR Spectroscopy
Get PDFThe ability to predict wood shrinkage could help manufacturers avoid lumber with abnormal dimensional stability or match pieces with similar properties in glued assemblies. Near infrared (NIR) spectroscopy is a rapid, nondestructive technique that has been used to predict various wood properties, including extractive content and density. Fifty-seven mahogany (Swietenia macrophylla) blocks were scanned using an NIR spectrometer, and were measured for specific gravity, extractives content, and total volumetric swelling. Models were created to predict the wood properties using the NIR data. These models could provide reasonable predictions of shrinkage, density, and extractives content. The use of nonlinear kernel and wavelet statistical techniques improved model performance. It may be possible to use NIR spectroscopy for the on-line sorting of wood according to dimensional stability
Reaction Rates of Lignin and Hexenuronic Acids with Chlorine Dioxide, Ozone, and Sulfuric Acid
Get PDFThe reaction rates of lignin and hexenuronic acids (HexA) with chlorine dioxide, ozone, and sulfuric acid were investigated. In unbleached and oxygen-delignified eucalyptus kraft pulps containing both lignin and HexA, only HexA, or only lignin reacted with chlorine dioxide, ozone, and sulfuric acid under typical bleaching conditions. The maximum reaction rates of chlorine dioxide with lignin and HexA were 57.2 and 26 mmol/kg/min, respectively, for unbleached pulp, and 26.7 and 13 mmol/kg/min, respectively, for oxygen-delignified pulp. The maximum reaction rates of ozone with lignin and HexA were 58.6 and 132 mmol/kg/min, respectively, for unbleached pulp, and 56.8 and 134 mmol/kg/min, respectively, for oxygen-delignified pulp. The maximum reaction rates of sulfuric acid with lignin, and HexA were 1.11 and 0.93 mmol/kg/min, respectively, for unbleached pulp, and 1.95 and 0.80 mmol/kg/min, respectively, for oxygen-delignified pulp. Chlorine dioxide reacts faster with HexA in the presence of the residual lignin. The kinetic results suggest that pulp treatment with ozone, when justifiable, should follow but not precede chlorine dioxide oxidation. Unbleached pulp residual lignin and HexA react twice as fast with chlorine dioxide than the lignin and HexA present in oxygen-delignified pulp, while the pulp type has no significant effect on lignin and HexA reactivity toward ozone. HexA reactions with sulfuric acid and ozone can be described by two-phase pseudo first-order reaction rates
Sorption and Thermodynamic Properties of Old and New Pinus Sylvestris Wood
Get PDFThe 35° and 50°C isotherms of juvenile Pinus sylvestris L. wood from recently cut trees were compared with those of juvenile wood of the same species previously forming part of an 18th century wooden building in order to determine the thermodynamic properties of the two types of wood through the isotherms. The isotherms were plotted using the gravimetric method of saturated salts in the water activity range of 0.11 to 0.97 for the 35°C isotherm and 0.11 to 0.96 for the 50°C isotherm. The sorption curves were fitted using the GAB method, and the isosteric heat of sorption was obtained by means of the integration method of the Clausius-Clapeyron equation. In both types of wood, the net isosteric heat decreases as the moisture content of the specimen increases, and the maximum values of isosteric heat in the new wood are greater than in the old wood, both in adsorption and desorption. This indicates that the bond energy in the new wood is greater than in the old wood
The Influence of Cutting-Bill Requirements on Lumber Yield Using a Fractional-Factorial Design Part II. Correlation and Number of Part Sizes
Get PDFCutting-bill requirements, among other factors, influence the yield obtained when cutting lumber into parts. The first part of this 2-part series described how different cutting-bill part sizes, when added to an existing cutting-bill, affect lumber yield, and quantified these observations. To accomplish this, the study employed linear least squares estimation technique. This second paper again looks at the influence of cutting-bill requirements but establishes a measure of how preferable it is to have a given part size required by the cutting-bill. The influence of the number of different part sizes to be cut simultaneously on lumber yield is also investigated.Using rip-first rough mill simulation software and an orthogonal, 220-11 fractional-factorial design of resolution V, the correlation between lengths, widths, and 20 part sizes as defined by the Buehlmann cutting-bill with high yield was established. It was found that, as long as the quantity of small parts is limited, part sizes larger than the smallest size are more positively correlated with high yield. Furthermore, only 4 out of the 20 part sizes tested were identified with having a significant positive correlation with above average yield (65.09%), while 10 were found with a significant negative correlation and above average yield. With respect to the benefit of cutting varying numbers of part sizes simultaneously, this study showed that there is a positive correlation between yield and the number of different part sizes being cut. However, Duncan's test did not detect significant yield gains for instances when more than 11 part sizes are contained in the cutting-bill
Finite Element Modeling of Laminate Wood Composites Hygromechanical Behavior Considering Diffusion Effects in the Adhesive Layers
Get PDFThe performance and quality of appearance layered wood composite products depend largely on their dimensional stability. Layers of various wood species and orientation and the presence of adhesive layers in such products may induce deformation following moisture content changes and reduce product value. In this context, research on the design and hygromechanical behavior of layered wood composites is of primary importance. More specifically, the impact of the adhesive layers on moisture movement and dimensional stability is not known. The main objective of this paper is to demonstrate the impact of the adhesive layer on the dimensional stability of layered wood composites and how it should be modeled by the finite element method. The impacts of mesh density, degree of interpolation of the elements and linear interpolation of the adhesive properties in the wood-adhesive interface of an engineered wood flooring strip were studied to determine the role of an adhesive layer in the cupping process. The results show that when the effective diffusion coefficient of the adhesive layer decreases, the gap between the linear and quadratic interpolation increases. It is however relatively small and when the number of element layers used in the adhesive increases, the gap between the linear and quadratic interpolation increases. The degree of interpolation used for the mechanical component of the model has a minor effect on cupping. Therefore, the choice of a higher degree of interpolation than linear is not necessary. The use of a mesh with a single layer of elements in the adhesive layer can lead to important approximation errors. Therefore, the utilization of more than one layer of elements in the adhesive is necessary
Effect of Axial Load on Torsion Fatigue Behavior of Wood
Get PDFThe torsion fatigue behavior of solid wood under cyclic torsion-axial combined loading was investigated. The test specimens used were air-dried Japanese cypress that were cut into sections of 17.5 mm (tangential) x 17.5 mm (radial), with their major axis lying along the fiber direction of 300 mm (longitudinal). A pulsating torsion with a triangular waveform was applied along the longitudinal axis of the specimens at 1 Hz, while the specimen was also simultaneously subjected to an axial (tension or compression) load at the same phase along the longitudinal direction, at stress levels corresponding to 50-100% of each static strength. The results obtained are summarized as follows: When tension was added to pure torsion, the inclination of the S-N curve tended to decrease as the tensile stress component increased. On the other hand, when compression was added to pure torsion, the S-N curve generally moved to the long-life side. The strength of the wood was different between dynamic and static modes, under not only pure loading but also axial-torsion combined loading. The torsion deformation under compression-torsion combined loading kept its initial value small until the increase before final failure, and this was considered to cause the lengthening of the fatigue life under the stress state, in which shear and compression stress components were almost equal