Wood and Fiber Science (E-Journal)
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Assessment of Forest Products Undergraduate Education in the United States
Get PDFTraditional Forest Products/Wood Science programs have been curtailed and/or merged into other programs at many universities during the last 10 yr. Current economic challenges throughout the nation are continuing this trend. This trend is somewhat alarming when one considers the implications for education and development of the next generation of scientists in this very critically important field. If proper training programs and adequate professionals are not available, the conservative, wise, and perpetual utilization of renewable natural resources could be compromised for future generations
Wood Machining Properties of Poplar Hybrid Clones from Different Sites Following Various Drying Treatments
Get PDFPlaning, sanding, turning, and routing properties of seven hybrid poplar clones from three growing sites were evaluated on kiln-dried specimens following three types of drying schedules, high temperature, elevated temperature, and conventional. Machining tests were performed at 8 and 12% MC according to ASTM D 1666-87. Surface quality was evaluated with qualitative and quantitative methods. Poplar clones performed well for planing, sanding, and routing and poor for turning. In general, machining performance was affected in decreasing order by machining, clones, kiln-drying treatments, and growing sites. The best planing was obtained at a 20° rake angle and at 24 knife marks per 25.4 mm. Better conditions should be obtained at a 17° rake angle and lower feed rates. Conventional drying positively affected planing performance compared with the other two drying processes. Sanding using 180-grit sandpaper performed excellently. Turning was better at 12% MC than at 8% MC. For routing, down-milling mode provided generally better surface quality than up-milling mode. Three clones were selected as more suitable for machining. Generally, denser wood behaved better than light wood for all machining processes. However, correlations between wood density and machining properties were weak. Although selection of best clones for wood density could indirectly help improve wood machining, direct measurement of these properties is preferable. Finally, only a few weak effects of drying and sites were observed on specific conditions of machining, and they were thus considered negligible
Comparison of Elastic Constants of Wood Determined by Ultrasonic Wave Propagation and Static Compression Testing
Get PDFIn Brazil, most reports on the elastic properties of wood include only the elastic modulus in the longitudinal direction. This is because of the difficulty in determining other properties through static testing. The purpose of this study was to evaluate the methodology for determining the three Young's moduli (EL, ER, ET), the three shear moduli (GLR, GLT, GRT), and the six Poisson ratios (VLR, VLT, VRL, VRT, VTL, VTR) using ultrasonic technology. For testing, we used specimens in the form of cubic prisms from the following species: Garapeira (Apuleia leiocarpa), Cupiuba (Goupia glabra), and Sydney Blue gum (Eucalyptus saligna). The ultrasonic tests were performed with plane transducers of longitudinal and transverse waves, both with a 1-MHz frequency. For comparison, the same specimens were tested by static compression. Based on the confidence intervals of the means, the results of the ultrasonic test produced values of longitudinal elasticity moduli (EL, ER, and ET) and shear moduli (GTR, GTL, and GLR) statistically equivalent to those obtained with static compression. In the case of the Poisson ratio, the results, using the confidence intervals, indicated that VRL, VLR, and VLT were not statistically equivalent to those obtained in static tests for any of the species. Conversely, VTL, VTR, VRT, were statistically equivalent to those obtained in static tests for all the species. In conclusion, the ultrasonic test for determining the Young's and shear moduli of wood was found to be simpler and less expensive than the static compression test, and the results are equally useful
Life-Cycle Inventory of Particleboard in Terms of Resources, Emissions, Energy and Carbon
Get PDFLife-cycle inventory (LCI) data are needed to scientifically document the environmental performance of materials for applications as governed by the many new green building standards, purchasing guidelines, and energy and climate change policy issues. This study develops the LCI data for particleboard, a composite wood panel product comprised of wood particles, urea-formaldehyde resin, wax, and other additives. Data are given for both gate-to-gate (particleboard manufacture) and cradle-to-gate (from the product upstream to in-ground resources) that, in addition to gate-to-gate impacts, include those to produce and deliver input fuels, electricity, water, wood residue, resin, wax, catalyst, and scavenger. LCI output data are given per 1.0 m3 of particleboard in terms of raw materials use and emissions to air, water, and land. Data are also presented on embodied energy, carbon flux, store, and footprint. Particleboard has favorable characteristics in terms of energy use and carbon store. Of significance for the LCI of particleboard is the large component of embodied energy because of the use of wood fuel, a renewable resource, and its small carbon footprint, which lessens its impact on climate change
The Impact Behavior of Ecofriendly Cellulosic Fiber-Based Packaging Composites
Get PDFWood-fiber composites with densities of 80, 90, and 100 kg·m-3 were created using a single-component polyurethane that was foamed by steam injection. The impact behavior of the composite was studied by static and dynamic tests. The dynamic impact curves of the composites were concave and upward. Decreasing densities or increasing resin content resulted in better dynamic cushioning properties. The minimum static cushioning coefficients were much lower and increased more slowly than the minimum dynamic cushioning coefficients with increases of density. Mathematical relations for minimum static and dynamic cushioning coefficients and densities were established. With the increase of initial dynamic shock stress the residual thickness-peak acceleration curve shifted to reduced residual thickness and higher peak acceleration. Dynamic maximum stresses were much higher and increased more sharply than static maximum stresses. These results can be used to optimize the structure and properties of the composites and evaluate the potential of applications in the packaging industry
Transverse Compression Behavior of Wood in Saturated Steam at 150-170°C
Get PDFThe transverse compression behavior of wood in high temperature (150, 160, and 170°C) and saturated steam conditions was studied. The effect of the temperature on the stress-strain response, nonlinear strain function, and relative density change was examined by a modified Hooke's law based on the load-compression behavior of flexible foams. The influence of environmental conditions during compression on the set recovery of the compression deformation was determined. It was found that temperature and moisture content affected the compression behavior of wood in saturated steam conditions. A small difference in moisture content of specimens compressed at 160 and 170°C caused approximately the same stress-strain and relative density curves with minimum temperature affect on the compression behavior. The compressive modulus of the wood and cell wall modulus were found to decrease with increasing temperature from 150 to 160°C with no change when increased to 170°C. The densification region was entered at notably lower stress levels at 160 and 170°C when compared with 150°C. The results established that temperature and moisture content did not affect the nonlinear strain function at strain levels lower than 0.63. Furthermore, it was found that the set recovery of compressive deformation decreased with increasing temperature of compression from 150 to 160°C. In addition, the results showed that compression at 160 and 170°C significantly lowered the equilibrium moisture content
Modeling Differently Oriented Loblolly Pine Strands Incorporating Variation of Intraring Properties Using a Stochastic Finite Element Method
Get PDFWood strands are a biological material with variations in material properties because of the presence of earlywood and latewood, juvenile wood and mature wood as well as the sectional cut used to generate strands. This variation should be accounted for to produce reliable modeling results. This study used both a deterministic finite element method (FEM) and a stochastic finite element method (SFEM) to model the stiffness of wood strands from three different orientations (radial, tangential, and angled) incorporating intraring property variation from two growth ring positions. In addition, a homogeneous model was used as a control to compare the results from both deterministic FEM and SFEM. The homogeneous model predicted the stiffness well for radial and tangential orientation strands but provided unrealistic physical strain distributions. Assumptions of strand homogeneity oversimplified the strain distribution present in the strand, eliminating local maximum and minimum values. Cumulative probability curves comparing previous experimental results and SFEM results showed general agreement. Average differences in the effective tensile modulus of elasticity ranged 0.96-22.31%. Based on the modeling results, the earlywood tensile modulus of elasticity was the input parameter that had the greatest influence on the strand stiffness. The order of correlation of the earlywood and latewood Poisson ratios changed based on strand orientation. SFEM techniques provided accurate results and material property distributions as compared with the experimental results
Effects of Wood Mixtures on Deterioration By a Filamentous Brown-Rot Fungus
Get PDFWood-degrading fungi import elements to meet physiological demands in wood, but little is known about interactions with different wood types. This is despite increased use of wood composites, in which durability can be tested but not well predicted. Blocks of nondurable aspen and spruce and moderately durable eastern white pine were degraded using the brown-rot fungus Gloeophyllum trabeum in soil- and agar-block microcosms for 16 wk. Block configurations were either a single species (monosubstrate) or mixed (polysubstrate). At 8 and 16 wk, total wood weight losses were the same in monosubstrate and polysubstrate microcosms; however, white pine degradation was consistently less in polysubstrates than in monosubstrates with decay in aspen and spruce compensating to achieve equal overall weight loss. Nondegraded pine had higher extractives and lower nitrogen levels as compared with the other woods. Carbon fractions and cation contents in degraded pine were typical of brown rot, suggesting the fungus reallocated resources to less durable aspen and spruce when given the option. Data demonstrate that wood durability can be influenced significantly by other wood types. Although this could influence the spatial pattern of decay in mixed materials, overall durability in small-particle size wood composites may also be predictable based on single-species performance
Numerical Modeling of the Load-Deformation Behavior of Doweled Softwood and Hardwood Joints
Get PDFThis article presents a nonlinear finite element model developed to simulate the load-deformation behavior of wood joints when loaded by a dowel-type fastener. Particular attention was paid to the initial load-deformation behavior that had a significant influence on the joint stiffness, a joint property with a large influence on the mechanical behavior of wood-based composite structures connected with semirigid joints. To obtain accurate predictions of joint deformation, the material models available in the literature were adapted and nonlinear deformations were taken into consideration during very early loading. The proposed model precisely describes the embedding behavior of different wood species and densities. Numerical results compared very well with those obtained in experiments. Based on this analysis, the recommendation is to obtain the material model inputs based on design values available in the literature
Life-Cycle Inventory of Medium Density Fiberboard in Terms of Resources, Emissions, Energy and Carbon
Get PDFLife-cycle inventory (LCI) data are needed to scientifically document the environmental performance of materials for applications as governed by the many new green building standards, purchasing guidelines, and energy and climate change policy issues. This study develops the LCI data for medium-density fiberboard (MDF), a composite wood panel product comprised of wood fibers, urea-formaldehyde resin, wax, and other additives. Data are given for both on-site (MDF manufacture) and cradle-to-product gate (from the MDF upstream to in-ground resources) that includes those environmental impacts to produce and deliver input fuels, electricity, water, wood residue, resin, wax, and scavenger. LCI output data are given for raw materials use and emissions to air, water, and land. Data are also presented on embodied energy, carbon flux, store, and footprint. MDF has favorable characteristics in terms of energy use and carbon store. Of significance is the large component of embodied energy from wood fuel use, a renewable resource, and its small carbon footprint that lessens its impact on climate change