Wood and Fiber Science (E-Journal)
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Modifying Wood Surfaces with Atmospheric Diffuse Coplanar Surface Barrier Discharge Plasma
Get PDFThis study presents possibilities of influencing the surface properties of Sessile Oak (Quercus petraea), European Ash (Fraxinus Excelsior), Norway spruce (Picea Abies), and European Larch (Larix decidua) by a low-temperature atmospheric plasma treatment (diffuse coplanar surface barrier discharge [DCSBD]) in various conditions of the plasma treatment. Effect of mutual distance from the surface of the electrode to a plasma-treated wood surface (from 0-1.2 mm), effect of plasma treatment duration (3, 5, and 10 s) usable on industry lines as well as the effect of the atmosphere used during the plasma treatment (air, N2, and CO2) were studied. Effects of plasma treatment on the wood surface were evaluated by measurement of water droplet contact angle, which expressed changes in the surface polarity. Mutual distance from the surface of the DCSBD planar electrode to the surface of a treated wood sample plays a crucial role in the final change of the surface polarity. If the mutual distance is set in the range from 0 to 0.4 mm, the hydrophilization effect is reflected on the surface of treated wood. Increased polarity can be expressed by measuring the contact angle of water droplets. In this case, this is reflected by lower values of contact angles than those of the reference plasma-untreated wood samples. Conversely, by setting mutual distance within a range of 0.5-1.2 mm, the hydrophobization effect was observed, as demonstrated by the increase in the contact angle values of plasma-treated wood samples compared with the reference sample, which in this case was wood hydrophobization. Hygrophobization of the wood surface was unlike many other published experiments and was achieved without the addition of other specialty chemicals only by setting the appropriate mutual distance. Conditions for possible industrial use of the plasma modification for all tested wood samples were found
Ohio Hardwood Sawlog Price Trends
No full textWe examined the 52-yr sawlog price trends for the 10 commercial hardwood tree species in Ohio. Data were compiled from the Ohio Timber Price Report for four log grades (Prime, #1, #2, Blocking) covering the years 1960-2011, and average annual percentage rates of change in both nominal and real sawlog prices were determined. We further compared real log grade price movements within each species. Nominal prices for all log grades of all species increased at significant annual rates. However, real price change rates varied with approximately two-thirds of the species-grade combinations not significantly differing from zero. Real Blocking log prices declined at significant annual rates for seven species. Only white oak contained log grades (Prime and #1 only) with significantly increasing real prices. Four groups were identified based on differences observed, or not observed, when comparing initial price levels of log grades and rates of change within each species. Initial price differences generally occurred between the higher (Prime and #1) and lower (#2 and Blocking) grade logs. Rate of price change differences were more a result of declining Blocking log prices than increasing high-grade log prices with the exception of white oak
Bending Fatigue of Wood: Strain Energy-Based Failure Criterion and Fatigue Life Prediction
Get PDFIn this study, bending fatigue behavior of Japanese cedar and Selangan batu was examined. A nonreversible triangular waveform with loading frequencies of 0.5 and 5 Hz was used as load. Applied loads were about 110-70% of the static strength. The fatigue life of Japanese cedar was found to be longer at 5 Hz, especially at low stress level. For Selangan batu, however, loading frequency did not affect fatigue life. When fatigue life exceeded about 40,000 cycles, a crack formed on the compressive sides of the specimens regardless of the loading frequency and species. Cumulative strain energy at failure was found to be the failure criterion regardless of the loading frequency. This criterion could be estimated using the strain energy through the static test. A fatigue life prediction method based on the strain energy of the second loading cycle was proposed. This prediction method provided a good prediction of fatigue life
Fungal Populations in Air and Materials in a Flood Simulation Study
Get PDFAir quality was measured in a building subjected to flooding conditions analogous to that which occurred during Hurricane Katrina. This building was flooded to a depth of 0.61 m above the floor with pond water and maintained at that level for 3 wk. After the floodwater was drained, the building remained closed for an additional 3 wk. Immediately on opening, air samples were obtained and analyzed for fungal spores. Dry and wet material components of the building wall were analyzed for the presence of mold fungi by both culture and molecular techniques. Additional air samples were taken after a 30-da drying period and then after remediation of the building. The air measurements demonstrated the presence of high concentrations of indoor mold spores when the building was initially entered. Aspergillus/Penicillium were the dominate air molds. Fiberglass batt insulation supported the greatest concentration of culturable fungi, compared with other wall materials, followed by the paper facings of gypsum board and plywood sheathing. The solid wood stud, vinyl siding, and house wrap all supported low concentrations of culturable mold. After drying, the spore air contamination diminished more than 10-fold and the species of fungi on the materials drastically changed. After remediation, the spores inside the structure nearly matched those outside with respect to type and concentration
Physical and Mechanical Properties of Veneer-Polyurethane Foam Composites
Get PDFThe purpose of this study was to develop core composite materials using veneer residues combined with appropriate matrix material. This study describes the evaluation processes of physical and mechanical properties of a recently developed polyurethane-veneer composite. In the layered construction of the product, the veneers provide strength and stiffness, whereas the polyurethane foam has a lateral supporting effect and sets the final dimensions in thickness of the slabs. Two key properties were studied. First, the density in relation to the wood constituent's moisture content and ambient RH was analyzed by three-level, two-factor, robust parametric design (3II RPD). Also, a two-level, three-factor + center point experimental design (2III + Cp) helped to evaluate the effects of the selected parameters on compression strength. Standard test results confirmed the improved compression force resistance compared with foams without reinforcement, whereas the density of the new composite remained way below the densities of core materials currently on the market. The intended use of the developed composite includes carrier substrates for countertops, interior door leaves, indoor heat insulating, and acoustic insulation panels as well as structural insulated panels
Laboratory and Field Exposures of Fire Retardant-Treated Plywood: Part 3—Modeling Exposure Relationships
Get PDFOur understanding of how to relate laboratory-induced degradation data to real-world in-service performance of fire-retardant (FR) systems is currently limited because we are unable to correlate laboratory steady-state experiments with actual in-service field performance. Current studies have generally been limited to isothermal rate studies with selected model FR chemicals. Currently, no known direct comparison exists of matched sets of samples with one set exposed to high-temperature laboratory conditions and the other exposed for an extended period of time as traditionally used in North American light-framed construction. The objective of this study was to determine the relationship for FR model compounds between laboratory and field results based on strength-temperature-RH (moisture content)-FR chemical interactions. Two previous studies evaluated the effects of various exposures on bending strength properties and directly compared matched laboratory- and field-exposure samples. This study presents an empirical model to relate the differential effects of laboratory and field exposures on changes in mechanical properties for matched samples
Calculations of Shear Moduli of Three-Ply Cross-Laminated Wood Panels from Shear Moduli of Individual Laminae
No full textTo study in detail the effect of deflection caused by shear force of cross-laminated panels, shear modulus, apparent modulus of elasticity (MOE), and deflection caused by shear force of cross-laminated panels with different component ratios of laminae thicknesses were investigated using the equation derived for calculating shear modulus of a three-ply laminated beam from the shear moduli of individual lamina. The calculated shear modulus for C⊥ type increased markedly with increasing core laminae thickness, and that for C∥ type decreased markedly with increasing core laminae thickness. Also, the calculated shear modulus for C⊥ (45) type was higher than that for C⊥ (90) type at every core laminae thickness, whereas the calculated shear modulus for C∥ (45) was higher than that for C∥ (90) type at every core laminae thickness. The calculated value of the apparent MOE showed good agreement with measured value, and it was found that the apparent MOE can be calculated from true MOE and shear moduli of lamina. The percentage of deflection caused by shear force (Ysc) calculated from the calculated apparent MOE was close to that (Ys) calculated from the measured apparent MOE. From these results, the validity of the derived equation for calculating shear moduli of laminated panels from individual lamina was proven once more
