Wood and Fiber Science (E-Journal)
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Sorting Lumber by Pith and its Effect on Stiffness and Strength in Southern Pine No. 2 2x4 Lumber
No full textSouthern pine (SP) lumber is visually graded based on knots, slope of grain, and amount of wane. Today, SP lumber contains more juvenile wood than in the past because of decreased rotation ages and the combined effect of mill and forestry practices. The presence or absence of pith is one method to identify lumber that contains a high percentage of low-stiffness and low-strength juvenile wood. However, it is not included in the visual grading system. In this study, we examined the effect that pith had on specific gravity, stiffness (modulus of elasticity [MOE]), modulus of rupture (MOR), and bending strength (Fb) in 744 samples of No. 2 2x4 SP. Lumber without pith had 14% greater specific gravity (15% MC) (0.50 vs 0.44), 35% greater stiffness (11.9 vs 8.8 GPa), and 49% greater MOR (53.4 vs 35.8 MPa) than lumber with pith. Lumber without pith met the 2011 design values for Fb (10.3 MPa) as well as MOE (11.0 GPa), whereas lumber with pith did not. These results show that if the presence of pith was included in the visual grading system, it could improve lumber properties and thus should be considered when grading SP lumber in the No. 2 2x4 grade and size
Bending Moment Capacity of Mortise and Loose-Tenon Joints
No full textThis study was performed to determine the effects of bottom shoulder width (18.5, 15, 10, 5, and 1.5 mm), tenon depth of embedment (15, 20, 25, 30, and 35 mm), tenon width (20, 25, 30, 35, and 40 mm), and tenon wood species on the bending moment capacities of T-shaped mortise and loose-tenon furniture joints constructed with polyvinyl acetate adhesive. Results indicated that bending moment capacity was directly related to depth of embedment of the tenons and strongly related to shoulder width, whereas tenon width had a lesser effect. Bending moment capacities of joints with beech tenons were higher than those of joints with tenons of other wood species. Nonlinear regression analyses were used to develop a predictive expression to estimate the bending moment capacity of the joints
Structural Characteristics and Properties of Windmill Palm Leaf Sheath Fiber
No full textA study was carried out on a special kind of fibrous material—windmill palm leaf sheath fiber (palm fiber)—with the aim of full utilization of the bioresource. Morphological feature and fine structure of palm fiber were investigated using light microscopy, scanning electron microscopy, and transmission electron microscopy (TEM). The results indicate that palm fiber is subcylindrical with a rough surface and large diameter (359.15 mm). Ultrastructure from TEM confirmed that cell wall layers of palm fiber have a structure similar to that of wood cell wall. Individual fibers in the palm fiber are elongated cells (length-diameter ratio is about 100) with lumen, tapering ends, and thick cell walls (about 1 mm). In addition, crystallinity, tensile properties, and moisture regain of palm fiber were studied and compared with flax, ramie, and bamboo fiber. Palm fiber has relatively lower crystallinity and tensile strength compared with the fibers, but it has extremely higher elongation
Effects of Species and Growth Ring Angles on Acoustic Performance of Wood as Resonance Boards
No full textIn this study, effects of wood species and growth ring angles of small wood beams cut from quartersawn boards on vibration efficiency indices were evaluated. Experimental results indicated that growth ring angles (0°, 60°, 90°, and 150°) and wood species (Sitka spruce, Sichuan spruce, Lijiang spruce) had significant effects on vibration efficiency indices. Wood beam samples with 90° growth ring angles showed better acoustical performance than those with 0° growth ring angles followed by samples with growth ring angles of 150° and 60°. Sitka spruce samples had better acoustic performance than Lijiang spruce samples followed by Sichuan spruce. Sitka spruce samples with 90° growth ring angles had the highest mean specific modulus of 33.8 MPa m3 kg-1, relative acoustic vibration efficiency of 5.4 MPa m3 kg-1, and conversion efficiency of 710 m4 kg-1 s-1 and the lowest loss tangent of 6.3 × 10-3. Specific modulus tends to be less sensitive in detecting mean differences among wood samples compared with the other three vibration efficiency indices evaluated in this study. Loss tangent, conversion efficiency, and relative acoustic vibration efficiency yield the same results if they are used as the indices to quantify sound performance of solid wood used as instrument soundboards
Near-Infrared Spectroscopic Analysis for Classification of Water Molecules in Wood by a Theory of Water Mixtures
Get PDFThis study was conducted to analyze the mechanism of moisture adsorption-desorption in wood using near-IR (NIR) spectroscopy. NIR spectra reflected from moist wood were acquired, and spectra in the range from 1800-2100 nm, which were sensitive to water variation, were decomposed into three different components according to the Buijs and Choppin theory. It is assumed that the three components represent three types of bound water: water molecules without -OH groups engaged in hydrogen bonds (S0), water molecules with one -OH group engaged in a hydrogen bond (S1), and water molecules with two -OH groups engaged in hydrogen bonds (S2). Ratios of the decomposed spectra of NIR absorbed by each type of water molecule were analyzed during changes in water adsorption-desorption states. Through this analysis, a sorption model for predicting the structural state of each water component in wood was constructed. This model may be used to explain the effect of each water component on the occurrence of hysteresis as well as the transient state between bound water and free water. Based on the model, it was concluded that the monomolecular water layer in yellow poplar wood formed below approximately 8% MC during adsorption. Additionally, the phenomenon of hysteresis was demonstrated by the difference between the ratios of the S2 components in desorption and adsorption
Technical Note: Melt Dispersion Technique for Preparing Paraffin Wax Microspheres for Cellulose Encapsulation
Get PDFA practical and convenient approach for making paraffin wax microspheres with a melt dispersion technique was reported in this study. Surfactants were melted in water by water bath and then added to a flask after the wax was completely melted with stirring. Paraffin wax microspheres were generated by cooling. The obtained microspheres exhibited uniform diameters in the range of 10-60 μm observed with a scanning electrical microscope and were mainly dependent on the surfactant ratio. Encapsulated microcrystalline cellulose particles with the previously mentioned conditions were also generated and demonstrated the possibility of encapsulating microcrystalline cellulose with some acceptable agglomeration, although some encapsulated individually. Encapsulation of cellulose could be beneficial if agglomeration could be minimized and the encapsulated microcapsules could be dispersed during blending for wood composites manufacture
Methodology for Micromechanical Analysis of Wood Adhesive Bonds Using X-ray Computed Tomography and Numerical Modeling
No full textStructural performance of wood adhesive bonds depends on their ability to transfer stress across an interface of dissimilar materials, namely cell wall substance and cured polymeric adhesive. The interphase region of the bond consists of cell wall substance, voids, and voids filled with adhesive. In this study, an integrated method to numerically model micromechanical behavior of this system is described. The method includes micro-X-ray computed tomography (XCT) to define the three-dimensional (3D) structure of the bond on a micron scale. Tomography data were used as direct input to a micromechanics model. The model provided a 3D representation of equivalent strain and stress of the adhesive bond under load and, furthermore, integrated the microstructure of the interphase region into the solution. The model was validated using lap-shear test results from the same specimens that were scanned for XCT. Optical measurement and digital image correlation techniques provided full-field displacement data of the lap-shear specimen surfaces under load. Model simulation results compared favorably with measured surface displacements with spatial resolution in the micron range. The main advantage of the methodology is the accurate representation of the 3D microstructure of wood and the penetrating adhesive system in the numerical model
Reinforced-Core Particleboard for Improved Screw-Holding Ability
No full textApplications of commodity particleboard are currently restricted by low screw-holding strength and low stiffness. Replacing the core particles with small strands that are used in the core of oriented strandboard (OSB) to produce a "particle-strand-particle" (PSP) hybrid can significantly improve particleboard strength properties. In this study, a set of particleboards was fabricated with standard core particles, randomly arranged OSB core strands, or aligned core strands to assess the effects of particle replacement with strands and their orientation in the core. PSP-random core board was similar to laboratory fabricated OSB with random core in properties such as density profiles, internal bond strength, and edge screw withdrawal resistance, but its strength properties were significantly improved compared with control particleboard. OSB and PSP boards had significantly higher thickness swelling typical of strand-based composites. Particleboard and PSP-oriented core had lower core density and higher surface density, whereas OSB and PSP-random core had higher core density and lower surface density. Core strand orientation methodology was problematic, but further optimization could potentially enhance the utility of M2- and M3-grade particleboard into more load-bearing applications
Effect of Fiber Size Distribution on Medium-Denstiy Fiberboard Properties Caused by Varied Steaming Time and Temperature of Defibration Process
No full textFor wood particle-based composite panels, particle size distribution and morphology are classified as crucial factors for the industrial production process and the resulting product properties. However, fiber quality control for medium-density fiberboard (MDF) production is still just done on a low technical level because adequate measurement systems are not available. Consequently, current fiber characterization approaches appear to be limited in reproducibility and do not fit optimally for process control. It is, therefore, the aim of this study to 1) introduce a recently developed particle analysis system that fulfills the requirements for MDF fiber characterization; and 2) show how defibration conditions, fiber size distribution, and fiberboard properties correlate with each other. Three different fiber types (thermomechanical pulp [TMP]) were produced by varying the steaming time and temperature of a thermomechanical refiner process. Fiber size distribution was determined, and properties of test panels made using these fibers as raw material were investigated. Fiber size decreased with increasing steaming time and temperature. Mechanical properties increased with increasing fiber length, whereas physical properties decreased