Wood and Fiber Science (E-Journal)
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Book Review: Wood Science for Promoting Legal Timber, edited by Alex C. Wiedenhoeft and Pieter Baas
No full textLife-Cycle Inventory of Manufacturing Hardwood Lumber in Southeastern US
Get PDFEnvironmental impacts associated with the building industry have become of increasing importance. Materials and energy consumed during manufacture of building materials such as lumber affect a building's environmental performance. This study determined environmental impacts of manufacturing hardwood lumber in the southeastern US using the life-cycle inventory method. Primary data were collected and then weight-averaged on a per-unit basis of 1.0 m3 of planed dry lumber (600 oven-dry kg/m3) to find material flows and energy use. Cumulative allocated energy consumption for manufacturing 1.0 m3 planed dry lumber from 2.44 m3 of incoming logs was 5.86 GJ/m3 with 66% from wood fuel. Emission data produced through modeling estimated total biomass and fossil carbon dioxide production of 424 and 131 kg/m3, respectively, considering all impacts. A cubic meter of planed dry hardwood lumber stores 1.17 Mg CO2 equivalents as a final product. The amount of carbon stored in hardwood lumber exceeds fossil carbon emissions by a factor of nine. Therefore, as long as hardwood lumber and its carbon stay in products held in end uses, carbon stored will exceed fossil carbon emitted in manufacturing
Technical Note: Effect of Epoxy Embedment on Micromechanical Properties of Brown-Rot-Decayed Wood Cell Walls Assessed with Nanoindentation
Get PDFMechanical properties of brown-rot-decayed wood cell walls were evaluated using a nanoindentation technique. Epoxy resin is a typical medium for the sample embedding process in nanoindentation. It is assumed that the embedding process does not affect cell wall properties or that any effects are similar for different samples. As part of an investigation of microscale mechanical effects of brown-rot in wood, we applied nanoindentation to cell walls of decayed and nondecayed pine wood samples. For epoxy-embedded samples, there were no differences in modulus and hardness for control and decayed samples. However, for unembedded samples, significant differences were found between control and decayed samples. These results indicate that the epoxy-embedding process may confound micromechanical testing results. We speculate that in this case, epoxy resin penetrated and reinforced the cell wall of decayed samples
Book Review: Fichas De Propiedades Tecnoló Gicas Y Usos De Maderas Nativas De México E Importadas by Jose Antonio Silva Guzmán, F. J. Fuentes Talavera, R. Rodríguéz Anda, P. A. Torres Andrade, M. G. Lomelí Ramíréz, J. Ramos Quirarte, C. Waitkus, H. G. Richter
No full textEffect of Tenon Geometry, Grain Orientation, and Shoulder on Bending Moment Capacity and Moment Rotation Characteristics of Mortise and Tenon Joints
Get PDFBending moment capacity and moment rotation characteristics of mortise and tenon joints as a function of tenon geometry, grain orientation, length, and shoulder fit were examined. Bending moment capacity of all joints in which tenons were fully inserted in mortises was 54% greater than for joints in which tenons were not fully inserted. Jointswith 25.4-mm-long diamond-shaped tenons had greater moment capacity than either rectangular or round tenon joints, whereas joints with 38- or 51-mm-long rectangular tenons had greater capacities than jointswith diamond or round tenons. Similarly, for joints inwhich tenonswere not fully inserted, rectangular tenons had the greatest moment capacity regardless of grain orientation or length
Tree Ring Characteristics of 30-Year-Old Swietenia Macrophylla Plantation Trees
Get PDFRing characteristics of mahogany (Swietenia macrophylla K.) plantation trees grown in Taiwan were explored. Significant differences in average ring width (RW) and ring density (RD) occurred among three tree-diameter classes and three radial stages of ring numbers. RW in the radial direction decreased from the pith outward to the bark and followed a distinctive three-stage variation pattern (juvenile, transition, and mature zones). RD in the radial direction increased slowly from the pith outward to the bark. Wider tree rings and lower density are associated with juvenile wood close to the pith, whereas narrower tree rings and higher density are typical for mature wood outward toward the bark. RD in overtopped trees was higher than that in dominant trees. However, RW in dominant trees was wider than that in intermediate and overtopped trees. Earlywood density, latewood density, maximum density, and minimum density were the most important factors determining overall RD. There was a weak relationship between RW and RD, indicating that it is unlikely for growth rates of mahogany plantation trees to have a significant impact on wood density
Fracture Toughness of Wood and Wood Composites during Crack Propagation
Get PDFMode I fracture toughness as a function of crack length of medium-density fiberboard (MDF), particleboard (PB), and Douglas-fir (DF) was measured using a new energy-based method. PB and MDF are examples of composites that develop fiber bridging during crack propagation, which causes their toughness to increase with crack length. Longitudinal cracks in DF also displayed fiber-bridging behavior, but only when the crack plane was normal to the tangential direction. MDF and PB experiments were performed for both in-plane and out-of-plane cracks. The toughness of the former was much higher than the latter. The in-plane crack toughness of MDF was higher than PB, but its out-of-plane toughness was lower. PB made using a new soy-based resin had an in-plane toughness similar to commercial PB but an out-of-plane toughness three times higher. Out-of-plane crack propagation is suggested as an improved method for measuring internal bond (IB) properties. When the fracture method was compared with conventional IB tests, both methods showed that the soy PB was better but the fracture method provided a clearer distinction
Lumber Drying Stresses and Mitigation of Cross-Sectional Deformation
Get PDFLumber drying is a time-consuming and energy-intensive operation that is complicated by shrinkage, which occurs when wood moisture content falls below FSP. Differential shrinkage between radial and tangential directions results in cross-sectional strains that cost the wood industry a substantial amount of money. A novel approach that uses the concept of drying stresses has the potential to mitigate this problem. This study investigated the feasibility of applying an impervious coating to lumber surfaces to induce stresses that minimize a drying distortion called cupping. Flatsawn and quartersawn southern red oak (Quercus falcata) lumber samples from 10 trees were analyzed. Specimens from the same lumber were randomly assigned to three treatments: uncoated, pith-side coated, and bark-side coated for flatsawn specimens; and uncoated, upper-side coated, and bottom-side coated for quartersawn specimens. Quartersawn specimens showed very limited distortion for all three treatments. Cupping was minimized in pith-side-coated flatsawn specimens but exacerbated in bark-sidecoated flatsawn specimens. Experimental strains for flatsawn uncoated specimens agreed with those predicted using a numerical model
Investigation of Flexural Creep of Kraft Paper Honeycomb Core Sandwich Panels Using the Finite Element Method
Get PDFFinite element (FE) models for the flexural creep of the sandwich panels with various Kraft paper honeycomb cores and wood composite skins were established. The creep constants of these FE models' core and skin were determined by simulating the experimental results of the flexural creep of the corresponding skin layer and sandwich panels individually. The influence of the core orientation, core shape, core and skin thickness, and core cell size was studied using these established FE models. The results indicated that the panel's flexural creep in the primary stage was smaller when the panel was thinner, longer, and wider as well as when the shelling ratio (thickness ratio between panel's core layer and skin layer) was smaller. The panel that had a higher stiffness skin layer, or the core's ribbon direction was parallel to the panel span, or was loaded at a lower level had a smaller flexural creep. However, there was no observed influence of honeycomb core's cell size on the flexural creep behavior of the sandwich panels