Wood and Fiber Science (E-Journal)
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Effects of Early Pruning on Ring Specific Gravity in Young Loblolly Pine Trees
Full text linkJuvenile wood is not well suited for use in many forest products. Understanding factors that affect the formation of juvenile and mature wood is important when managing commercially important conifer species. The purpose of this investigation was to determine the contribution of ring age, relative height in the stem, and crown position (within or not within the green crown) on ring specific gravity of loblolly pine trees pruned at young ages. A designed experiment consisting of five treatments, control; prune at age 3 yr, age 6 yr, or age 9 yr; and at ages 3,6, and 9 yr, was established at two locations in the Piedmont region of Virginia. Wood samples were acquired at three heights along the stem 15 yr after planting. Results showed that differences in ring specific gravity of the treated plots (Half of green crown removed at each scheduled pruning) were significantly higher than that of the control plots. All variables of ring age, relative height and ring position of within or not within the green crown, were statistically significant. The results suggest that cambial age, maturation, and proximity to green crown are important for controlling whole-ring specific gravity in loblolly pine trees.
Density profile and micromorphology variation of densified wood from three fast growth hardwood species in Costa Rica
Full text linkThis study evaluates 1) the effect of the thermo-hydro-mechanical densification process-using three temperatures, two compression times, and the presence or absence of steam, and 2) the effect of initial wood micromorphology on the density profile of densified wood of three low-density fast growing hardwood species in Costa Rica (Alnus acuminate, Vochysia ferruginea, and Vochysia guatemalensis). Four density profiles in the densified wood of the three species resulted from the densification temperature and the initial micromorphology of the wood. The initial diameter of the vessels affects the compression stage during the densification process and causes the formation of irregular density profiles. Therefore, this is the most important element in determining the type of the density profile. The wood of A. Acuminata (with smaller-diameter vessels) densified at 180oC tends to produce more uniform density profiles than the other two species that have larger diameter vessels. The time of compression and the use or not of steam as an initial stage in the densification process did not influence the types of density profiles obtained. Similarly, the type of wood tissue and wood pattern had no effect on the type of density profiles. In conclusion, uniform and regular density profiles in densified wood are more likely to be achieve at high temperatures and with smaller-diameter vessels.
TECHNCIAL NOTE: Hardwood Species Bonding Properties After Cyclic Changes of Environmental Conditions: First Trials
Full text link The focus of this research was to investigate the bonding quality of the adhesives type after exposure to various moisture and temperature changes. This exposure was to simulate the changes in the interior application, which can cause problems in furniture manufacturing, especially with the usage of different adhesives. Different types of adhesives (Polyvinyl acetate (PVAc), Polyurethane (PUR), urea-formaldehyde (UF), and melamine-urea-formaldehyde (MUF)) were tested for bonding quality on two hardwood species; European beech (Fagus sylvatica L.) and English oak (Quercus roburL.). Bonding quality was tested based on EN13354 standard for control specimens, after 8 and 16 cycles of moisture and temperature changes. There was no statistical difference in bonding quality for the PVAc adhesive on beech and oak wood. PUR adhesive showed a significant decrease in the bonding quality of beech wood and no change in oak wood after exposure. The highest reduction in bonding quality after exposure cycles was found in the UF adhesive due to hydrolysis of the adhesive, regardless of the wood species. There was only reduction in the bonding quality for the MUF adhesive for beech wood after 16 cycles of the exposure condition.
Effect of Distance Above Ground during Air Seasoning on Flexural Properties of Blackgum and Red Oak Ties
Full text linkStacks of red oak (Quercus rubra) and black gum (Nyssa sylvatica) railroad ties were seasoned 150, 200, or 300 mm above the ground to investigate the effect of height on fungal colonization and timber properties. Decay fungi became increasingly abundant as seasoning time increased. Decay fungi were more abundant on black gum than red oak ties, but fungal isolation frequency did not differ with variation in seasoning sill height. Similarly, neither MOR nor MOE differed with seasoning height. The results indicate that decreasing the tie seasoning height by 150 mm had no significant effect on either fungal colonization or timber properties.
ANTIFUNGAL ACTIVITY OF ORGANIC ACIDS AND THEIR IMPACT ON WOOD DECAY RESISTANCE
Full text linkOrganic acids are present in many bio-based chemicals suggested as active ingredients for wood preservative formulations, but their effects in wood have not been studied. However, an understanding of their effect in wood is necessary. The aim of this study was to determine the antifungal and wood-preserving activities in vitro of acetic, formic, and propionic acids against the wood-decaying fungi Coniophora puteana, Rhodonia (Poria) placenta, Gloeophyullum trabeum, and Trametes versicolor. Mixes of these three acids were also tested for possible synergetic effects. All the acids and mixtures showed antifungal activity against the pure cultures of wood-decaying fungi. Propionic acid by itself had the best performance, inhibiting at 1 g/L concentration the growth of all the decay fungi by 99-100%. Despite the antifungal activity of the organic acids, the pine sapwood specimens treated with 3% and 6% acid solutions and exposed to decay by C. Puteana and G. trabeum did not differ significantly from the untreated pine. Leaching of the sapwood specimens caused an incremental mass loss of the sapwood specimens. In addition, the leached specimens had a lower mass than the specimens before the acid impregnation, indicating that they were damaged by the acidic chemicals. The presence and acidity of organic acids in wood-derived bio0-based chemicals need to be assessed before they are used as wood preservatives.
The Wood Products Processing Program at the University of British Columbia – Reflections on the Last Twenty-Five Years
Full text linkThe Department of Wood Science at the University of British Columbia initiated its Wood Products Processing (WPP) program in September 1995. The program replaced a previous wood science-based program, which, like many programs across North America at the time, suffered from low enrollment levels. The new program introduced a greater focus toward manufacturing processes, their analysis and optimization, and aspects of business operations. This article describes the establishment of some of the essential components of the WPP program and their development over the last 25 yr. Enrollment, co-op program, and graduation data are presented. The transfer programs established with Chinese forestry universities, which have fueled recent WPP program growth, are detailed. Some areas where the program has met with less success are discussed, as are some recent developments of the program
Grading lumber with acoustic-based technologies Part 2: ultimate tension stress estimation from time- and frequency-domain parameters
No full textThis research article summarizes results from Part 1 of a study designed to examine the use of advanced signal processing techniques with acoustic-based lumber assessment technologies to evaluate the MOE and ultimate tension stress (UTS) of structural lumber. In Part 1 of this research, a mathematical model of acoustic wave behavior in an idealized specimen is derived using fundamental mechanics. In Part 2, wave behavior is examined experimentally in a series of 38 × 38 × 2438-mm wood specimens. The specimens vary considerably in visual character. Several of the specimens are, from a visual assessment, clear of naturally occurring defects such as knots. Conversely, strength-reducing defects such as knots are visible in several specimens. The presence of naturally occurring defects can affect acoustic waves in a variety of ways. A few examples include altering wave speed, changing the wave travel path, and/or converting the wave from longitudinal waves to shear waves or back through mode conversion. These alterations can cause wave behavior to deviate from the behavior observed in clear wood specimens. Deviations are observable in both time and frequency domains. From the differences, parameters are identified which improve estimation of UTS.
Physical and mechanical behaviors of thermally modified rubberwood glulam beam under sustained and cyclic loading
Full text linkThis study evaluated the effect of thermal modification on the physical and mechanical properties of rubberwood glued laminated (glulam) timber. The flexural creep property and cyclic loading behavior were also investigated. The obtained results indicated that the MC and specific gravity of thermally modified rubberwood decreased with an increase in modification temperature. Moreover, the flexural strength of the rubberwood glulam timber at modification temperatures of 180 and 220oC was 8.57% and 46.72%, respectively, which was less than that of the control rubberwood dried at 90oC. However, the MOE between the thermally modified rubberwood glulam timber and control specimens was not significantly changed. The flexural creep test indicated that the maximum relative creep of the thermally modified rubberwood timber equaled 0.31, which was lower than that of other natural timber and tended to decrease when increasing the stress level. Various mathematical models were also proposed, and the best-fitted model was found to be the Bailey-Norton power law model. Nevertheless, the cyclic loading results also proved that thermal modification temperature had a direct effect on the ductility index and energy dissipation of rubberwood glulam timber, but it had no significant effect on the impairment of strength.
Ground-Penetrating Radar Investigation of Salvaged Timber Girders from Bridges Along Route 66 in California
Full text linkThis study describes assessment of the internal conditions of timber bridge structural members along Route 66 in California. These timber bridges were exposed to desert climate conditions for several decades, which can lead to a variety of deterioration. Overtime, the deterioration may cause loss of structural integrity within the bridges and lead to potentially hazardous conditions for the motoring public. Members from dismantled bridges were brought to the Forest Products Laboratory in Madison, WI. Strength-reducing features including decay, splits and cracks insect attack, and corrosion of metal components were initially identified using visual inspection. Further assessment was then performed using several nondestructive testing technologies including ground=penetrating radar (GPR). GPR was used, among other nondestructive techniques, to identify and locate internal features and defects within the timbers. The tomographic output of the GPR known as radargrams, revealed deterioration. Based on the information contained within the radargrams, it was possible to classify some internal features and defects with a high degree of certainty, whereas others remained less clear. In this study, the potential of using GPR for inspection of bridge timbers is discussed and supported through interpretation of the radargrams