Wood and Fiber Science (E-Journal)
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Comparison of Accelerated Methods for Evaluating Leaching from Preservative Treated Wood
Get PDFCurrent standardized methods are not well-suited for estimating in-service preservative leaching from treated wood products. This study compared several alternative leaching methods to a commonly used standard method, and to leaching under natural exposure conditions. Small blocks or lumber specimens were pressure treated with a wood preservative containing borax and copper hydroxide. The specimens were leached using scenarios involving short periods of immersion, simulated rainfall, or to a longer period of outdoor exposure to natural precipitation. When compared with lumber specimens exposed to natural precipitation, leaching from immersed small blocks overestimated losses of both copper and of boron, whereas immersion of lumber specimens underestimated losses of copper. Stirring during immersion, which is required by some standard methods, did not affect leaching. Simulated rainfall most closely simulated leaching during outdoor exposure, but is relatively complex and may be difficult to standardize. Leaching appeared to be directly related to the time that specimens had sufficient moisture to allow diffusion to occur. Further research is needed to better characterize moisture contents of wood products outdoors and develop methods that simulate those moisture conditions.
WOOD DENSITY AND EXTRACTIVE CONTENT VARIATION AMONG JAPANESE LARCH (LARIX KAEMPFERI, [LAMB.]CARR.) PROGENIES/PROVENANCES TRIALS IN EASTERN CANADA
Get PDFTwelve years old Japanese larch (Larix kaempferi, [Lamb.]Carr.) stems of 20 different progenies and/or provenances were obtained. Two disks of 5 cm thickness were cut at approximately 0.25 m and 2.7 m from the ground. Two wedges were cut from each disk to determine basic density at these two heights. The remaining log was used to obtain standard samples for the determination of basic and oven-dry densities closest to the bark. The adjacent material of standard samples was used to produce sawdust for the determination of hot-water extractive content. Basic and oven-dry densities were then corrected by the mass of extractives. Wedge basic density showed a significant variation along the stem. Density was higher at 0.4 m than at 2.75 m in height. However, no significant effect of progeny/provenance was found, nor for basic and oven-dry densities. Once these densities were corrected, the progeny/provenance showed a significant effect which allowed a progeny grouping by density. Hot-water extractive content was also significantly affected by the progeny/provenance and it varied between 2.9 to 6.9%. Progeny 7280 would have an interesting potential among progeny/provenance for lumber and pulping uses as it showed the lowest extractive content, the highest corrected densities and high growth rate. In general, corrected densities and extractive content would be more appropriate for a preliminary selection of the progenies/provenances according to the final utilization. Further studies of other wood properties would be necessary to confirm these results
LATERAL LOAD RESISTANCE OF PARALLEL BAMBOO STRAND PANEL-TO-METAL SINGLE-BOLT CONNECTIONS – PART I: YIELD MODEL
Get PDFThe lateral load resistance behavior of single-shear unconstrained metal-to-parellel bamboo strand panel (PBSP) single-bolt connections was investigated. The connection consisted of a PSBP main member fastened to a metal plate as a side member using a 6-mm diameter bolt without a nut or washer used. The mechanics-based approach waas used to evaluate critical factors on the lateral load resistance performance of metal-to-PBSP single-bolt connections. Experimental results indicated that the lateral resistance loads of the metal-to-PBSP single-botl connections were significantly affected by its shear strength parallel to bamboo strand orientation, tensile strength perpendicular to bamboo strand orientation and bolt-bearing strenth in PBSPs. Lower tensile strength perpendicular to bamboo strand orientation of PBSPs can limit its usage as connection members resisting lateral loads. The proposed mechanical model was verified experimentally as a valid means for deriving estimation equations of lateral resistance loads of unconstrained metal-to-PBSP single-bolt connections evaluated in this study.
INVESTIGATING GASEOUS CARBON, NITROGEN, AND SULFUR COMPOUNDS OF BAMBOO, WOOD, AND COAL DURING PYROLYSIS PROCESS
Get PDFBamboo, wood, and coal were pyrolyzed by a thermogravimetric analyzer coupled with Fourier transform infrared spectrometry to investigate gaseous carbon, nitrogen, and sulfur compounds from fuels. It was found that the main gas compounds of fuels included carbon dioxide, carbon monoxide, methane, sulfur dioxide, hydrogen sulfide, ammonia gas, and hydrogen cyanide. Compared with masson pine, bamboo had a higher gas release and more mass loss due to its lower pyrolysis temperatures when temperature was lower than 350°C. Coal had the lowest gas release and the least mass loss due to the higher pyrolysis temperature during the whole pyrolysis process. The char-C, N, and S contents of all fuels increased with increase in pyrolysis temperature. The results from this research will be helpful to utilize the wastes of masson pine and bamboo for energy products.
CHARACTERISTICS OF SCREWDRIVING TORQUES IN WOOD-PLASTIC COMPOSITES
Get PDFThe characteristics of torque magnitudes for driving screws into wood-plastic composites (WPCs) were investigated through evaluating effects of different factors on seating torque (SET) and stripping torque (STT) commonly used to characterize the process of driving screws into amaterial. The factors were embedded screw orientation in WPCs, pilot-hole diameter, screw penetration depth, and screwdriver air pressure. Recorded torque-time curves of driving screws into WPCs evaluated in this study indicated that the complete screw driving process can be described as a three-phase process of thread forming and screw seating, clamping, and screw stripping WPCs. Mean SET values for driving screws into WPCs can range from 0.47 to 1.83 N-m, STT values from 1.54 to 4.87 N-m, and their corresponding STT-to-SET ratios from 1.0 to 4.4. Statistical analyses indicated that mean SET and STT values of driving screws into WPCs increased as screw penetration depth increased from 12.7 to 25.4 in increments of 6.35mm. The significance of pilot-hole diameter effects on mean SET and STT values is influenced by screw penetration depth. Mean SET values at 0.45 MPa air pressure level were higher than those at 0.62MPa, whereas the significance of screwdriver air pressure effects on mean STT values is influenced by pilot-hole diameter and also screw penetration depth. The significance of embedded screw orientation effects on mean SET values is influenced by screw penetration depth and pilot-hole diameter and on mean STT values by screw penetration depth, pilot-hole diameter, and screwdriver air pressure
Comparison of Nondestructive Testing Methods for Evaluating No. 2 Southern Pine Lumber: Part B, Modulus of Rupture
Get PDFThe identification of strength-reducing characteristics that impact modulus of rupture (MOR) is a key differentiation between lumber grades. Because global design values for MOR are at the fifth percentile level and in-grade lumber can be highly variable, it is important that nondestructive evaluation technology be used to better discern the potential wood strength. In that manner, higher-performance pieces could potentially be identified and their value captured accordingly. In this study, laboratory tests of three nondestructive testing (NDT) technologies and destructive four-point static bending were applied to 343 pieces of visually graded No. 2 southern pine lumber in the 38140 mm2 (n . 86), 38186 mm2 (n . 112), 38236 mm2 (n . 91), and 38 287 mm2 (n . 54) sizes collected across the southeast region of the United States. The NDT tests included continuous lumber test in continuous proof bending (MetriguardModel 7200 High Capacity Lumber Tester), transverse vibration (Metriguard E-Computer), and two longitudinal stress wave tools (Falcon A-Grader and Fiber-gen Director HM200). Following nondestructive tests, the specimens were destructively tested in four-point static bending. Single-predictor linear correlations were observed between static bending MOE and MOR value; and NDT outputs and bending MOR value. The regression results showed that the average NDT outputs (r2 . 0.23-0.28) had lower performance than static bending MOE (r2 . 0.39), for predicting the bending MOR of sawn lumber.
Thermal and acoustic characteristics of innovative foam core particleboards
Get PDFInnovative foam core particleboards have potential to be used for the thermal and sound insulation applications. The insulation properties of novel foam core particleboard panels (19 mm) produced with various production process parameters were analyzed in this study. It was revealed that both surface layer thickness thicknesses of panels and press temperature were the two major parameters influencing the thermal performance of novel foam core particleboards. The lower the surface layer thickness, the better the thermal insulation. A higher thermal resistance was also obtained for panels produced with higher press temperature (160˚C), due to their better structure for thermal resistance (less compaction of surface layers and higher foam cell density). Sound insulation characteristics of foam core particleboards revealed that the sound transmission loss (TL) and sound transmission class (TC) were enhanced by increasing the surface layer thickness from 3 to 5 mm. Changing press temperature, pressing and foaming times had no influence on the sound TL and TC. In general, the foam core panels having lower density (30-50% lower) than those of conventional panels showed promising thermal and sound insulation properties, while still, further modifications would be necessary.
BIOMASS GASIFICATION AND PHYSICAL ANALYSIS OF PLANT BIOMASS AND AGRICULTURAL WASTE PRODUCTS IN LOUISIANA
Get PDFThere are many properties that can affect the quality of syngas generated from biomass gasification. Among the most critical are ash, heating value, moisture, and density of the feedstock. The focus of this study is to analyze the characteristics of different woody biomass materials and agricultural wastes typically found in Louisiana or similar regions. The energy content of combustible gases produced by gasification is also quantified. The feedstocks analyzed are pine, hardwood pellets, alfalfa, switchgrass, sugarcane bagasse, corn, cypress mulch, chipped bark nuggets, dairy manure, and poultry litter. Analyzing and comparing the different feedstock characteristics indicates that the differences in physical properties are largely responsible for varying energy generation capabilities from gas produced through gasification. Ultimately, it is determined that pine and hardwood are the best candidates for energy production through gasification, based on their high density, relatively low MC, and low ash content. Producer gas generated from pine gasification had the highest concentration of hydrogen, carbon monoxide, and methane and resulted in the greatest energy output when combusted.
HUMAN AND TEST BAG IMPACT LOADS ON STATIONARY SEATING
Get PDFHuman subjects were hired to sit on an instrumented chair to measure impact loading as a function of time. These loads were compared with testing loads that are used in the ANSI/BIFMA X5.4 and X5.1 Seat drop and seat durability loading test regimens. Factors that were investigated experimentally on impact loading were standing-to-sitting ingress1 motion, seat foundation type, seat height, as well as sandbag weight and drop height. Center of seat deflection, caused by human subjects and sandbags, were recorded as a function of time. Experimental results from human subjects’ sitting tests concluded that maximum sitting forces averaged 100% and 247% with respect to a participant’s body weight for normal and maximum sitting impact forces. The seat deflection speeds for normal sitting was 16.3 cm/s and varied from 71 to 84 cm/s for hard sitting. Sandbag free drop experimental results indicated that drop height had a significant effect on maximum impact forces on the seat foundations. Maximum impact drop forces increased as sandbag weight increased, but the significance was dependent on the seat foundation type. The panel-foam seat foundation had the lowest impact force among three seat foundations evaluated. The spring-foam seat foundation resulted in significantly higher impact forces than the panel-only seat foundation if the sandbag drop height was less than 13 mm, but as the drop height increased to 30 mm, the significance became less. The impact force on a panel-only seat foundation became significantly higher than the spring-foam foundation as the drop height increased to 50 mm.