Wood and Fiber Science (E-Journal)
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Bending Moment Resistance of L-Shaped Two-Gusset-Plate Furniture Joints in Oriented Strandboard
Get PDFBending moment resistances of L-shaped joints connected with two gusset plates stapled on one side of joint members in oriented strandboard (OSB) were investigated. Factors were joint member material type, rail width, and number of staples. Experimental results showed that ultimate moment resistances of L-shaped, gusset-plate joints ranged from 429 to 842 N-m. Ultimate moment resistance loads of joints connected with 12 staples were 43% higher than those with 8 staples. Ultimate moment resistance loads increased as rail width increased from 152 to 203 mm with an increment of 25.4 mm, but the significance was affected by material type and number of staples. The increase in ultimate moment resistance loads of L-shaped, gusset-plate joints was not sensitive to material density profile change and density increase when 178-mm-wide or less rails were used, but the increase in moment resistances was sensitive to density increase when 203-mm-wide rails were used. Moment load-displacement curves of gusset-plate joints indicated that moment resistance loads at the ultimate point were two times their corresponding moment resistance loads at a proportional limit. The mechanical model was verified experimentally as a valid means for deriving estimation equations of moment resistances of L-shaped, gusset-plate joints in OSB
Accelerated Weathering Test of Kenaf Fiber Unsaturated Polyester Sheet Molding Compounds
No full textNatural fiber is an excellent renewable resource for making composite materials that are more lightweight than those made with fiberglass. However, the major issue for composites made with natural fibers as reinforcement is their hydrophilic nature. In this study, laminated composites were prepared using nanoparticle-impregnated kenaf fibers and a modified polyester resin containing multiwalled carbon nanotubes. These were compared with composites made from retted fibers, fiberglass, and unmodified polyester resin. After being subjected to accelerated weathering in a weatherometer, modified composites exhibited significantly less water sorption and minimal decrease in flexural modulus compared with unmodified composites
Kiln Schedule Certification for Industrial Drying of Radiata Pine
No full textThis is a summary of a study carried out in Chile to certify industrial kiln drying of radiata pine to comply with the international phytosanitary standard ISPM 15. The drying tests were performed in 100-m3 industrial kilns located at four different sawmills of the VIII region in Chile. The objective was to develop a standard protocol to certify industrial drying of radiata pine depending on the drying schedule and wood thickness. In part, the results were used to develop a multiple regression equation that permits sawmills to select their drying schedules in such a way that the lumber can be officially stamped as both kiln-dried and heat-treated for international trade
Prediction of Wood Quality in Small-Diameter Douglas-Fir Using Site and Stand Characteristics
No full textStanding stress wave measurements were taken on 274 small-diameter Douglas-fir trees in western Montana. Stand, site, and soil measurements collected in the field and remotely through geographical information system (GIS) data layers were used to model dynamic modulus of elasticity (DMOE) in those trees. The best fit linear model developed resulted in an adjusted R2 = 0.52 for predictions of individual tree DMOE and an R2 = 0.85 for predictions averaged on a stand basis. The linear model used was mean annual increment-1, total tree height, and a GIS-based estimate of soil bulk density. Logical models were also developed to predict membership in dichotomous DMOE categories with 71-82% selected trees meeting their respective DMOE criteria. The inverse relationship between soil bulk density and DMOE could be explained by the soil-tree moisture interactions know as least limiting water range
Technical Note: Static Versus Cyclic Load Capacity of Side Chairs Constructed with Mortise and Tenon Joints
No full textThe effect of cross-sectional tenon geometry on static and cyclic load capacity of side chairs constructed with round-, rectangular-, and diamond-shaped mortise and tenon joints was investigated. Cyclic load capacity averaged about two-thirds of static load capacity for the joint configurations tested. For the configurations included in the test, chairs with mortise and tenon joints constructed with round-, rectangular-, and diamond-shaped tenons had static load to cyclic passing load ratios of 56.5, 66.8, and 69.2% for rectangular-, round-, and diamond-shaped tenons, respectively. These results indicate that useful relationships existed between static and cyclic performance of round mortise and tenon joints, which may simplify the design process for chairs that must pass cyclic performance tests
Mechanical Properties of Moso Bamboo Treated with Chemical Agents
No full textBamboo is a type of biomass material and has great potential as a bioenergy resource for the future in China. Surface chemical and thermal-mechanical behavior play an important role in the manufacturing process of bamboo composites and pellets. In this study, moso bamboo was treated by sodium hydrate solution and acetic acid solution. Surface chemical and dynamic mechanical properties of bamboo were determined using Fourier transform infrared spectroscopy and dynamic mechanical thermal analysis, respectively. Results showed that the main polar chemical groups of the outer layer of bamboo (OB) included hydroxyl group (O-H) and ester carbonyl (C=O). Some new polar chemical groups appeared on the inner layer of the bamboo surface (MB) such as aromatic ethers (C-O-C) and phenolic hydroxyl (C-O). The chemical group difference of OB and MB confirms that there was a waxy layer on the OB surface. Nonpolar chemical groups decreased and polar chemical groups increased on the OB surface when it was treated by acetic acid solution. The waxy layer of the OB surface was removed and the lignin structure was also destroyed by sodium hydrate solution. The general feature of thermal-mechanical properties with temperature was similar to cellulosic materials for OB, OB-NaOH (OB treated by sodium hydrate solution), and OB-acetic (OB treated by acetic acid solution). A lower storage modulus of OB-NaOH and OB-acetic was helpful to improve physical properties of bamboo pellets. There was an α transition (α1) peaking at about 65°C for OB. The second major relaxation (α2) occurred at 35°C. The α1 and α2 transition temperature of OB changed when it was treated by chemical agents. This information is very important for using bamboo to manufacture composites and pellets
Technical Note: Plasma Pretreatment Enhances Field Performance of Exterior Wood Coatings
No full textPlasma pretreatment of wood modifies surface properties and can lead to increased wettability or hydrophobicity. These modified properties can lead to improved coatings adhesion. The present work examines the performance of selected coatings on wood pretreated with plasmas in a field test. After 31 mo of exposure in coastal British Columbia, a semitransparent film-forming finish was less degraded and exhibited lower levels of mold or blue stain on plasma-pretreated samples than on untreated controls. This suggests that plasma treatment of wood prior to coating could lead to improved coatings performance and resistance to mold or blue stain
Moisture and Temperature Changes of Wood during Adsorption and Desorption Processes
Get PDFSitka spruce (Picea sitchensis Carr.) specimens, 10 mm along the grain and 20 mm in radial and tangential directions, were exposed to three different RH conditions of 22, 47, and 75% for adsorption and desorption at 30°C controlled by a self-designed temperature conditioning chamber. Specimen weight was measured and thermal images were taken at certain time intervals during the processes to investigate their moisture and temperature changes. Results showed that at the beginning of the sorption process, moisture content of the specimens changed significantly and their average temperature increased about 2-7°C for adsorption and decreased about 1-6°C for desorption. During adsorption, the temperature for the center section along the longitudinal direction of the specimens was lower than that for the surface section, whereas the opposite was true for specimens under desorption. Along with the adsorption and desorption processes, moisture content and average temperature of the specimens were gradually approaching equilibrium state
Ring Width Variation and Heartwood Development in Quercus Faginea
Get PDFHigh-value exploitation of endogenous forest species may help in fighting the threat to their sustainability, as is the case for Quercus faginea Lam. (Portuguese oak) for which research is underway to determine the wood potential for high-quality products. Ring widths were measured in 20 trees in two sites in Portugal and within-tree heartwood and sapwood development was determined. The wood shows distinct ring porosity. The mean annual radial growth at dbh was 2.3 and 1.0 mm for the two sites, respectively. Ring width decreased with cambial age, ie 3.1 ± 1.2 mm in the first 10 rings to 1.3 ± 0.8 mm at around 40 yr (site 1). Ring width decreased axially from the tree base upward but the variation was small. The trees showed a relatively high proportion of heartwood, ie 60-70% heartwood for 20-25 cm wood diameters that decreased with height, and followed the stem profile. Heartwood diameter was modeled as a function of stem diameter, to be used for heartwood estimation in standing trees. Sapwood width was relatively constant. Overall the stem quality was found to be good for production of solid wood products regarding ring and heartwood features
Properties and Wood Bonding Capacity of Nanoclay-Modified Urea and Melamine Formaldehyde Resins
Get PDFUrea formaldehyde (UF) and melamine formaldehyde (MF) thermosetting resins were substituted with up to 6% nanoclay (organic modified Cloisite®30B and unmodified Nanofil® 116; Southern Clay Ltd, Austin, TX) and assessed for mixing and curing compatibility using X-ray diffraction, differential scanning calorimetry, wood lap-shear tests, and particleboard strength tests. Cloisite® 30B exfoliated fully in both resin types, whereas Nanofil® 116 showed increased spacing between platelets (intercalation) but not exfoliation. Nanoclays improved bonding strength of MF more than UF resin, and 2% nanoclay with a coupling agent in MF significantly enhanced particleboard bonding strength. Also, thickness swelling of particleboard in water decreased with up to 6% nanoclay. To decrease costs, MF resin could potentially be substituted by up to 6% nanoclay with no detrimental effect on properties