Wood and Fiber Science (E-Journal)
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Performance Evaluation of Phenol Formaldehyde Resin-impregnated Veneers and Laminated Veneer Lumber
Get PDFFor the past decade, mountain pine beetle infestation in British Columbia, Canada, has substantially changed wood characteristics of vast amounts of the lodgepole pine (Pinus contorta) resource. Resin impregnation is one method that could improve the properties of the beetle-affected wood. The key objective of this study was to examine the impact of resin impregnation on dynamic MOE of lodgepole pine veneers and properties of laminated veneer lumber (LVL) made with these treated veneers. A new phenol formaldehyde resin was formulated to treat these veneers using dipping and vacuum-pressure methods. Five-ply LVL billets were made with treated and untreated veneers. Their color, dimensional stability, surface hardness, flatwise bending modulus and strength, and shear strength were evaluated. Good correlation existed between veneer MOE enhancement and resin solids uptake. With the same treatment, stained veneers had higher resin retention and in turn greater MOE enhancement than nonstained (clear) veneers. A 5-min dipping was sufficient for veneers to achieve approximately 7 and 10% resin solids uptake and in turn 5 and 8% enhancement in veneer MOE for nonstained and stained veneers, respectively. LVL made with treated veneers had a harder surface with no discoloration concerns compared with the control. Also, evidence suggested that use of resin impregnation can improve dimensional stability, shear strength, and flatwise bending MOE of LVL
Evaluation of Mold and Termite Resistance of Included Sapwood in Eastern Redcedar
Get PDFThe heartwood of eastern redcedar (Juniperus virginiana) frequently contains areas of light-colored wood. This "included sapwood" is considered to be a defect by some manufacturers. In this study, sapwood, included sapwood, and heartwood samples from five eastern redcedar trees were exposed to mold fungi or subterranean termites in a no-choice feeding test. Specific gravity, extractives content, and total volumetric shrinkage were also measured. The extractive content, specific gravity, and volumetric shrinkage values of sapwood and included sapwood were equivalent. Greater extractive content in heartwood blocks was associated with less volumetric shrinkage and greater specific gravity. Included sapwood showed the same resistance to mold growth as heartwood, which was more mold-resistant that the sapwood. Included sapwood, heartwood, and sapwood of redcedar all exhibited resistance to termite attack compared with pine wood controls
Modeling Hygroelastic Properties of Genetically Modified Aspen
Get PDFNumerical and three-dimensional finite element models were developed to improve understanding of major factors affecting hygroelastic wood properties. Effects of chemical composition, microfibril angle, crystallinity, structure of microfibrils, moisture content, and hydrophilicity of the cell wall were included in the model. Wood from wild-type and decreased-lignin transgenic aspen (Populus tremuloides Michx.) was used for experimental validation of the computer model. The model was able to predict longitudinal elastic modulus of microfibrils and woody cell walls. The difference in longitudinal elastic properties between wild-type and genetically modified aspen wood was predicted well only when additional softening of hemicelluloses and amorphous cellulose of transgenic aspen was included in the model
Properties of Wood/recycled Textile Composite Panels
Get PDFThis study evaluated the potential to use recycled cotton textiles as filler and possibly reinforcement in the core of oriented strandboard (OSB) panels. Nominal 11.1-mm-thick, 686 x 686-mm OSB/textile fiber composite panels (50% surface and 50% core layers) were fabricated. Recycled textile material (0, 5, 15, 25, and 50% of the total weight percentage in the panel) was blended with mixed hardwood core strands. For each combination of wood and textile material, 10 panels were produced for a total of 50 panels. Internal bond strength, static bending strength and stiffness, water absorption, thickness swell, and nail withdrawal strength properties were evaluated. The major finding of the study indicated that compared with controls (ie panels with 0% textile material), panels with 5% recycled textiles did not have a statistically significant difference in bending strength (modulus of rupture) and elasticity (modulus of elasticity) or nail withdrawal strength. Additionally, although the controls had the greatest average thickness swell, none of the groups tested showed a statistically significant difference (p = 0.064). The study indicated that there is potential for adding 5% recycled textiles to the core of OSB panels without significantly decreasing physical or mechanical properties
Effect of pH on Chemical Components and Mechanical Properties of Thermally Modified Wood
Get PDFTo investigate the correlation between acidity and degradation during thermal treatment of wood, Cathay poplar (Populus cathayana Rehd.) wood samples were impregnated with solutions of different pH values, which included disodium octoborate tetrahydrate (DOT, pH = 8.3), monoethanolamine (MEA, pH = 12), and four buffering solutions composed of boric acid and sodium hydroxide (BA/NaOH, pH = 6, 7, 8, 9). Samples were then heated for 4 h at 180, 200, and 2208deg;C, respectively. Bending MOR and MOE, mass losses, pH values, and percentages of lignin and hemicelluloses were subsequently determined in thermally modified samples and compared with control samples without pretreatment and/or thermal treatment. Results of the experiments indicated that DOT and buffering solutions decreased mass loss of thermally treated wood and increased bending MOR and MOE, whereas MEA pretreatment increased mass loss and showed comparable or even lower bending MOR and MOE than the untreated control with or without thermal treatments. Chemical analyses suggested that degradation of hemicelluloses was inhibited by DOT and BA/NaOH pretreatments within the temperature range 180-200°C, which may explain the mechanical property improvement
Wood Use in Nonresidential Construction: An Exploratory Research of the Roles of Media and Content in Direct Marketing
Get PDFThe purposes of this research were to explore the role of selected marketing communications on the perceived identity of wood among architects and to define informational needs left unaddressed by those communications. The research was based on an experimental design implemented among architects designing nonresidential structures in the United States. The perceived identity of wood used structurally, using concepts from the branding literature, was not altered by any of the three stimuli (brochures categorized as Advertising, Case Study, and Technical Data). The case study was deemed more influential than the technical brochure with the advertisement ranking in between. Important informational needs identified related to design possibilities, regulations and standards, environmental footprints, and sustainable design. However, it must be noted that the experiment was limited temporally. It covered only one type of communications, although this type is the most common. Research results imply that the development of the nonresidential market should involve a long-term strategic commitment as opposed to a "quick fix" in the form of an advertising campaign
Effect of Geometric Parameters of Finger Joint Profile on Ultimate Tensile Strength of Single Finger-Joined Boards
Get PDFThe feasibility of adopting a short finger profile for structural finger-joined lumber was studied by investigating the effect of geometric parameters of a finger joint profile on ultimate tensile strength (UTS) of single finger-joined boards. Six finger joint profiles were designed with three finger lengths (28.27, 15.88, and 12.70 mm). A commonly used finger profile was included as a control. Eastern white pine (Pinus strobus) lumber was used to fabricate single finger-joined boards that were joined using a polyvinyl acetate adhesive. Analysis of variance showed that the finger joint profile had a statistically significant influence on UTS of single finger-joined boards. Finger profile P2 showed the highest UTS value and had the shortest finger length among seven groups. With decreasing profile slope, UTS increased. Slope of 1:12 appeared to be the optimized value for finger jointing. UTS decreased with increasing tip width. It can be concluded that with the proper design of finger profile, a finger joint with short finger lengths can be used to fabricate finger-joined structural lumber without any loss of tensile strength compared with the finger length commonly used by the wood industry
Characterization of Wood Strands From Young, Small-Diameter Douglas-Fir and Western Hemlock Trees
Get PDFTensile properties of strands processed from small-diameter Douglas-fir and western hemlock trees grown on the Washington coast were analyzed and effects of location within the tree on properties was examined. Reduction factors for strand properties relative to small, clear solid wood specimen properties were determined by correlating strand properties to previously examined small, clear solid wood specimen properties from the same set of trees. These reductions can be assumed to be damage reduction factors that could help in understanding the expected reduction in tensile or flexure property values from testing solid wood specimens to estimate strand tensile properties. The reduction factors ranged between 0.62 and 0.70 for Douglas-fir and 0.79 and 0.82 for western hemlock for the modulus and were approximately 0.46 for both Douglas-fir and western hemlock for strand tensile strength properties. Measured and calculated strand properties, based on transformation equations, will provide needed values for constructing constitutive relationships when modeling strand-based composites. These properties can also be estimated based on solid wood test specimens if necessary
