Wood and Fiber Science (E-Journal)
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Tensile Properties of Single Rattan Fibers
Get PDFThe longitudinal tensile strength of single fibers of four rattan species, namely C. simplicifolius, C. nambariensis Becc. var. yingjiangensis, C. nambariensis var. xishuangbannaensis, and C. yunnanensis, was studied using a custom-built short vegetable fiber mechanical tester. The stress-strain curves produced by the four different rattans showed two distinct phases: a steep, straight segment in the initial phase followed by a straight line with a lower slope up to the breaking point. The respective average values for tensile elastic modulus, tensile strength, and elongation at breaking point of C. simplicifolius, C. nambariensis.var. xishuangbannaensis, C. yunnanensis, and C. nambariensis var. yingjiangensis canes were 10.61, 10.05, 9.10, and 9.54 GPa; 603, 566, 464, and 539 MPa; and 17.00, 17.24, 16.44, and 21.08%. The length position of the single fibers in the cane had variable effects on the three aforementioned properties for all four sampled rattan species. The tensile properties of C. simplicifolius fibers were highest. Compared with wood and bamboo, modulus of elasticity and tensile strength of the studied rattans were much lower, whereas elongation at breaking point of single rattan fibers was generally higher
Face Lateral Resistance of Oriented Strandboard Joints Connected with Two Rows of 16-gauge Coated Staples
No full textThe ultimate lateral resistance of face-to-face joints connected with two rows of 16-gauge coated staples in three oriented strandboards (OSB) of different densities was investigated. Experimental results indicated that the ultimate lateral resistance of the face-to-face OSB joints increases significantly as the number of staples increases from two to eight in increments of two. Vertical and horizontal staple alignment was found to have no significant effect on the ultimate lateral resistance of the face-to-face OSB joints when the number of staples used was less than eight. The face-to-face OSB joints constructed of a higher density material yielded a higher ultimate lateral resistance, but the significant increase in ultimate lateral resistances due to increase in material density depended on the number of staples used and also staple alignment. The increase in the ultimate lateral resistance became more sensitive to material density increase once the number of staples used was six and higher. The ultimate lateral resistance of face-to-face OSB joints connected with two rows of 16-gauge coated staples can be reasonably estimated using two alternative empirical power equations. One equation requires the ultimate lateral resistance of a face-to-face OSB joint connected with one staple. The other equation requires the density of an OSB material used as the joint main member
Microstructure and Properties of Liquefied Wood-Based Activated Carbon Fibers Prepared from Precursors and Carbon Fibers
No full textLiquefied wood-based activated carbon fibers (LWACF) were prepared from liquefied wood-based precursors (LWP) and liquefied wood-based carbon fibers. Microstructure and properties of LWACF were studied using analysis of X-ray diffraction, nitrogen adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and a microtensile tester. It was found that LWACF prepared from LWP (LWACF1) could form a larger crystal size and denser graphite-like structure than those prepared from LWCF (LWACF2). However, for LWACF2, micropores were more numerous and average micropore width was larger, leading to the conclusion that LWACF2 had smaller diameter and lower mechanical properties than LWACF1 and that the burn-off value of LWACF2 was larger than that of LWACF1. Furthermore, excess amounts of element carbon (C) and C bonded to oxygen-containing functions were found on the surface of LWACF2. In conclusion, postcarbonization could damage the graphite-like structure, resulting in expanded micropores and impaired mechanical properties. Postcarbonization brought about an increase in the amount of element C and in the relative content of C bonded to oxygen-containing functions
Decay Resistance and Extractive Content of Second-Growth Port Orford Cedar (Chamaecyparis Lawsoniana) Wood
Get PDFPort Orford cedar (Chamaecyparis lawsoniana) has a reputation for being resistant to fungal attack, but much of the work to support this premise used older growth material (80-100 yr old). Given the tendency for the heartwood from the second growth of some species to be less durable, we evaluated the decay resistance of Port Orford cedar heartwood from 12 trees in laboratory soil block tests using Postia placenta and Gloeophyllum trabeum as the test fungi. Weight losses ranged from as little as 1.1 to more than 60% with most blocks experiencing weight losses between 11 and 24%. Heartwood was resistant to attack by G. trabeum but proved to be very susceptible to P. placenta and was only moderately resistant to this species. These results suggest that the durability rating of second-growth Port Orford cedar merits a re-evaluation
Lateral Load-Carrying Connection Properties and Withdrawal Capacity of Hybrid Poplar
Get PDFAn experimental study is reported aimed at determining the yield load, withdrawal capacity, and validity of National Design Specification (NDS) yield models on connections between hybrid poplar and common sheathing materials using a dowel-type fastener. Plantation-grown hybrid poplar (Pacific Albus) was procured, and connections with two different thicknesses of oriented strandboard and plywood were constructed using a dowel-type fastener. The NDS does not list connection design values for low-density wood species. Therefore, it was important to validate the NDS yield model equations for applicability toward a low-density species such as hybrid poplar. The results quantify the lateral load-carrying and withdrawal capacities of hybrid poplar. Also, the prediction using NDS yield models consistently matched the observed yield loads and yield modes for all the sheathing types used in this study. The data suggest that the NDS yield model is an adequate tool for connection design even for low-density species, provided knowledge of dowel-bearing capacity of the hybrid poplar is known
Modal Analysis of Upright Piano Soundboards by Combining Finite Element Analysis and Computer-Aided Design
Get PDFThis study presents a visual model for analyzing the vibration modes of piano soundboards by combining the tools of finite element analysis and computer-aided design. Based on the predicted results from the model, changes of natural frequency and maximum displacement of the soundboard as a function of wood properties, structure, and rib size were discussed. Wood grain direction affected the mode shape of the soundboard. Among the 10 property factors investigated, density presented the greatest impact to the vibration mode of the soundboard followed by Young's modulus, shear modulus, and Poisson's ratio. Increasing the thickness of the resonance board and the use of ribs had positive impacts on the natural frequency of the soundboard. However, the amount of natural frequency was decreased for those that were lower than 100 Hz. Natural frequency increased as the intensity, density, and size of ribs increased. Rib height had a greater effect on the variation of natural frequency than the intensity, density, and rib width. In general, increases in rib intensity, density of wood species, and rib width presented negative effects on the maximum displacement
Effects of Outdoor Exposure on Properties of I-Joists
Get PDFWood I-joists are often left uncovered and exposed to the weather during construction, allowing the oriented strandboard and laminated veneer lumber in these systems to be adversely affected by water absorption. Manufacturers typically specify that these materials be protected from wetting, but this can be difficult in wetter climates. There are few studies examining the potential effects of wetting on these building elements. In this study, flexural properties and ultimate tensile strength of I-joists exposed for extended periods of time during the rainy winter months in the Willamette Valley of western Oregon were evaluated. I-joists were removed from the field each month, dried, and then tested in static bending (flexure) using a six-point bending test. I-joist strength decreased as a function of exposure time and rainfall. Twenty-seven da of external exposure was associated with a significant increase in flexural variability. Further exposure was associated with significant decreases in I-joist strength (modulus of rupture). Although most I-joists never experience this degree of wetting, they can when construction is delayed. The results illustrate the detrimental effects of exposure to wetting during construction and support improved efforts to limit wetting
Examination of Water Phase Transitions in Black Spruce by Magnetic Resonance and Magnetic Resonance Imaging
Get PDFThis study examines the phase transitions of water in wood by magnetic resonance and magnetic resonance imaging. The goal was to observe and understand the behavior of water below 0°C in wood. The species studied, black spruce (Picea mariana Mill.), presented one abrupt phase change that occurred at about -3°C, which was attributed to the phase transition of free water. A more diffuse change occurred below -60°C, which was attributed to a phase transition of bound water. A recently developed portable unilateral magnetic resonance instrument is demonstrated as a powerful tool in the study of water in wood. This portable magnet used a bulk spin-spin relaxation time measurement that quantifies observable bound and free water in wood. Imaging was used to verify the unilateral magnetic resonance results and to better understand realistic freeze-thaw behavior of log samples in the field. A ring boundary behavior during the thawing process was observed, and likewise there were differences in the thawing behaviors of heartwood and sapwood samples
Among-Clone Variations of Anatomical Characteristics and Wood Properties in Tectona Grandis Planted in Indonesia
Get PDFAnatomical characteristics (vessel diameter [VD], fiber wall thickness [FWT], fiber diameter [FD], vessel element length [VEL], and fiber length [FL]) and wood properties (basic density [BD] and compressive strength parallel to grain [CS] in the green condition) were determined for 27 12-yr-old teak trees planted in Java Island, Indonesia. The mean values of VD, FWT, FD, VEL, FL, BD, and CS were 188 μm, 2.78 μm, 23.4 μm, 284 μm, 1.42 mm, 510 kg/m3, and 37.5 MPa, respectively. Significant differences in VEL, BD, and CS occurred among the nine clones. Moderate to high values of repeatability were obtained for FD, VEL, BD, and CS, indicating that these characteristics are genetically controlled. Radial variation of FL with respect to relative distance showed almost the same pattern for two different radial growth rates (faster and slower) at the same age, suggesting that xylem maturation in teak trees depends on cambial age rather than stem diameter
