Wood and Fiber Science (E-Journal)
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Assessing Wood Quality of Borer-Infested Red Oak Logs with a Resonance Acoustic Technique
Get PDFLarge numbers of black oak (Quercus velutina Lam.) and scarlet oak (Quercus coccinea Muenchh.) trees are declining and dying in the Missouri Ozark forest as a result of oak decline. Red oak borer-infested trees produce low-grade logs that become extremely difficult to merchandize as the level of insect attack increases. The objective of this study was to investigate the use of a resonance-based acoustic technique to evaluate the wood quality of infested red oak logs before processing as measured by grade, type and location of defects, and mechanical properties of the resulting boards. Principal component and canonical correlation analyses revealed that relationships do exist between log acoustic measurement and board grade yield, and between a linear combination of log acoustic velocity and diameter at breast height and a linear combination of board defect measurements. Although the acoustic technique was found capable of assessing wood quality at a stand level, the major advantage of the technique lies in segregating logs within the stand
Feasibility of Using Saltcedar as a Filler in Injection-Molded Polyethylene Composites
Get PDFSaltcedar (Tamarix ramosissima) was investigated for use as a filler in wood-plastic composites (WPCs). The mineral content, water-soluble extractive content, and thermal stability of saltcedar flour were compared with those of a commercial pine wood flour. The wood flours were compounded with plastic, and the viscosities of the composite melts containing the two species were compared. Injection-molded composites produced from the compounded material were evaluated for mechanical performance and weatherability. Saltcedar flour had more minerals and water-soluble extractives than pine flour, which resulted in lower thermal stability, but also lower melt viscosity when compounded with high-density polyethylene. Injection-molded WPCs made from unextracted saltcedar performed similarly to those made from pine in accelerated weathering tests, but their mechanical properties were generally lower. The flexural modulus of elasticity increased when extracted wood flour was used, especially for the saltcedar composites. However, color stability and flexural strength changed little. Producing WPCs from these composites is possible, although economically feasible applications that use the advantageous properties of these species and that can tolerate or address the less desirable ones need to be identified and demonstrated
Improvement of Prediction Accuracy of Glulam Modulus of Elasticity by Considering Neutral Axis Shift in Bending
Get PDFThere is a discrepancy between the estimated modulus of elasticity (MOE) of glulam based on the dynamic MOE of laminates and measured MOE. The discrepancy is greater for glulam manufactured with mixed species. This study was undertaken to reduce the discrepancy between those MOE values. The error rate of predicting MOE of glulam by the transformed section method, without considering tension and compression modulus differences, was about 30%. To estimate the MOE of glulam more accurately, the differences between compression and tension modulus should be taken into account in the transformed section method. The measured tensile and compressive strain at the center of glulam under a bending load showed the movement of neutral axis toward the tension side of glulam. Therefore, the compression and tension modulus differences for each species should be identified before estimating the MOE of glulam. The prediction of glulam MOE was improved significantly by reflecting the ratio of compression and tension modulus vs dynamic MOE of laminates. The outermost of laminates in the compression side under bending load experienced plastic behavior and failure. This caused the neutral axis to move to the tension side and increased tension stress to cause the glulam to fail abruptly in tension. To improve the bending performance of glulam, reinforcing compression laminates need to be considered
Seismic Performance Testing of Partially and Fully Anchored Wood-Frame Shear Walls
Get PDFEarthquake performance of wood-frame shear walls was evaluated by comparing fully and partially anchored walls under monotonic, cyclic, and earthquake loads and comparing with code measures. Suitability of monotonic and cyclic testing to predict seismic performance was examined. Earthquake tests were conducted on 2440-mm-square walls with Douglas-fir studs. Two oriented strandboard panels were fastened to the frame with two gypsum wallboard panels on the opposite side. Partially anchored walls had two anchor bolts on the sill plate. Fully anchored walls had hold-downs at the ends. Four time histories were tested: three subduction zone ground motions and a strike-slip fault, all scaled to the Seattle design level. For fully anchored walls, subduction zone tests had capacities, energy dissipation, and failure modes most similar to cyclic tests. Wall displacement at maximum load was under-estimated by cyclic and overestimated by monotonic tests. For partially anchored walls, subduction zone and strike-slip earthquake tests had capacity, displacement at maximum load, initial stiffness, and ductility most similar to cyclic tests. Energy dissipation was most similar to monotonic tests, and failure modes were consistent with monotonic and cyclic tests. Partially anchored walls had lower capacity, displacement at maximum load, energy dissipation, and stiffness as compared with fully anchored walls
Surface Characterization of Red Maple Strands After Hot Water Extraction
Get PDFThe conversion of carbohydrates from wood to make biofuels such as ethanol is a topic of widespread interest. A promising approach is the removal of the hemicellulosic wood component by extraction with subsequent conversion to biofuels while continuing to produce forest products. The impact of extraction on wood strands for use in strand-based composites was investigated. One tree of red maple (Acer rubrum L.) was used to create strands 10.2 cm long with a thickness of 0.9 mm. Three hot water extraction procedures at 160°C, corresponding to severity factors (SF) of 2.71, 3.54, and 3.81, were used resulting in an average weight loss of 5.7, 16.9 and 18.1%, respectively. Scanning electron microscopic imaging of selected wood strands showed that pores in the cell wall increased as SF increased. The distribution and size of the cell-wall pore structure showed up to a 22.2% increase. The sessile drop method, using distilled water, diiodomethane, and ethylene glycol, indicated more pronounced liquid wetting and penetration as SF increased. Inverse gas chromatography led to the finding that dispersive surface-free energy and acid-base characteristics increase with SF. The extraction procedures should be kept below a SF of 3.54 to minimize changes in adhesion performance
Determining Hybridization in Jack Pine and Lodgepole Pine from British Columbia
Get PDFThis study was conducted to find wood quality evidence of hybridization between jack pine (Pinus banksiana) and lodgepole pine (Pinus contorta var. latifolia) in northeast British Columbia (BC). To determine if wood and fiber traits could be used as distinguishing features among jack pine, lodgepole pine, and their hybrids, differences in morphology and wood and fiber traits were related to the genetic identity of each sample. Thirty samples each of pure lodgepole pine, pure jack pine, and potential hybrids were collected from the Prince George area of BC, the Smoky Lake area of Alberta, and the Fort Nelson region of BC, respectively. Two 10-mm cores (bark to bark) were taken from each tree and analyzed for fiber length and coarseness, microfibril angle (MFA), basic density, earlywood:latewood ratios, and cell dimensions. Needle and cone morphology was used to distinguish among species groups in the field. Based on genetically identified samples, the fiber traits that best differentiated among pure jack pine, lodgepole pine, and hybrids were MFA and cell area
The Effects of Copper-Based Preservative Technologies on the Resistance of Aspen Strandboards to Biological Degradation
Get PDFMold and decay resistance of aspen strandboards treated with various copper-based preservative systems were evaluated in laboratory tests. Five copper-based chemicals or zinc borate were blended into the aspen furnish at three retention levels. Tebuconazole or 4,5-dichloro-2-N-octyl-4-isothiazolin-3-one (DCOI) were added as cobiocides to selected copper-based treatments. Panels were inoculated with four common molds and subjected to high temperature and humidity for 8 wk according to AWPA Standard E24. Most panels experienced extensive mold growth, but panels treated with DCOI had marked resistance to attack as did combinations of copper-based preservatives and DCOI. Panels were also assessed for decay resistance in a laboratory soil-block test against the brown-rot fungus Gloeophyllum trabeum or the white-rot fungus, Trametes versicolor, according to AWPA Standard E10. All preservatives reduced weight losses caused by G. trabeum or T. versicolor below 10%, except for micronized copper hydroxide or DCOI alone. The four other copper-based preservatives performed well independently and with the addition of DCOI or tebuconazole. The results suggest that incorporating combinations of copper-based preservative systems with organic cobiocides improved decay and mold resistance of aspen-oriented strandboard
Nailed Mortised-Plate Connections for Small-Diameter Round Timber
Get PDFIn an effort to encourage the development of value-added engineered applications for smalldiameter round timber, research is being conducted at the US Forest Products Laboratory to develop and verify design guidelines for connections with specific application to round timbers. The objective of this study is to provide potential users with a number of viable connection options applicable to the fabrication of engineered, round-timber structural components and systems. Target uses include trusses, built-up flange beams, and space frames. This article presents information on a mortised steel-plate connection fabricated using power-driven nails in 150-mm-dia ponderosa pine. The article discusses methods used to determine per nail load capacity and to develop design procedures that incorporate that value in the determination of a multinail connection design value. These connections offer the advantage of low labor and material cost, ductile failure modes, and strengths in the range of 4.7 kN/nail. The failure of the connections was mode III nail failure and wood block shear failure. Joints that failed in block shear appeared to have roughly the same strength as those that failed from nail yield. The National Design Specification yield model for nails provides accurate predictions of joint capacity for nail yield-type failures and overestimates strength of joints that exhibit wood failure. Block shear capacity can be estimated on the basis of clear-wood strength and effective tensile and shear area of the connection
Effect of Extractives on Water Sorption and Durability of Wood-Plastic Composites
Get PDFWood—plastic composites (WPCs) were made from isotactic polypropylene and extracted and unextracted flours of one of four different wood species. WPCs made with extracted wood flour had lower mechanical properties than unextracted WPCs with the exception of pine WPCs. For all of the species except pine, WPCs made with extracted wood flours showed higher moisture sorption and thickness swelling characteristics. Higher levels of fungal decay were observed for the WPCs made with extracted wood, except for the pine WPCs, in which there was lower fungal decay from brown rot in the extracted wood samples. These results demonstrate that wood extractives affect the mechanical properties, water sorption, and fungal decay resistance of WPCs