Wood and Fiber Science (E-Journal)
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Degradation of Wood in Standing Lodgepole Pine Killed by Mountain Pine Beetle
Get PDFLodgepole pine is widely distributed throughout the Pacific Northwest and is an important commercial species. Although outbreaks of mountain pine beetle can kill extensive areas of pine stands, little attention was paid to postmortality rate of wood quality and quantity deterioration until the most recent outbreak, which because of its unprecedented size has resulted in extensive salvage harvesting. We used dendrochronology to determine the exact year of mortality and destructive sampling to quantify change in wood characteristics with time. We also estimated the fall-down rate of dead trees. Most trees did not start to fall until 8 yr postmortality. We found that change in wood moisture content was the main driver behind changes in wood properties. Dependent variables included checking (number and depth), blue-stain depth, saprot, and damage caused by wood borers and were explained by a small collection of biophysical variables. Biogeoclimatic unit and soil moisture regime were not important predictors of decay and degrade, except for development of saprot at the base of trees. Wood quality significantly changed within the first 1-2 yr postmortality and varied with position along the stem followed by a period of relative stability
Feasibility of a New Hybrid Wood Composite Comprising Wood Particles and Strands
Get PDFHybrid boards consisting of a strand core and particleboard faces (PSP) with three different shelling ratios were designed using strand sizes from dust to 4.5 mm mesh and normal particleboard face material. Flexural properties, internal bond (IB) strength, screw withdrawal resistance (SWR), hardness, and dimensional properties were measured. The modulus of elasticity of these hybrid boards was 25% greater than that specified by the ANSI standard for M3 industrial particleboard. An increase in modulus of rupture of approximately 50% was recorded for boards containing 60% strands compared with control particleboard without strands. Hybridization also accounted for a decrease in linear expansion compared with particleboard. However, IB strength decreased and SWR values showed no significant change. Therefore, with improved core properties, PSP has the potential to replace M3 particleboard
Tensile Properties of Four Types of Individual Cellulosic Fibers
Get PDFThis research is intended to expand information on fiber characteristics for better understanding their complexity and potential in industrial use. Tensile properties of four types of individual cellulosic fibers, bamboo, kenaf, Chinese fir, and ramie, were measured by a custom-designed microtensile tester. Load-displacement curves for most individual fibers were found to be linear until failure. Average values of at least 30 individual fibers of bamboo, kenaf, Chinese fir, and ramie were 1685, 983, 908, and 1001 MPa for tensile strength; 26, 19, 14, and 11 GPa for tensile modulus; and 7.1, 5.4, 8.3, and 8.9% for elongation at break, respectively. Cross-sectional areas of cell walls measured by confocal laser scanning microscopy were 117, 140, 217, and 337 μm2, respectively, an inverse relation with tensile modulus. Among the fibers, bamboo had the greatest tensile strength and modulus, whereas the other three did not have any statistical difference. Ramie had the largest elongation at break and the lowest modulus. Elongation at break of kenaf was significantly smaller than that of the other fibers. Fracture morphologies and load-displacement curves indicated these fibers were brittle materials. Tensile data can be used to screen fiber applications
Performance of Three Alternative Surfacing Processes on Black Spruce Wood and Their Effects on Water-Based Coating Adhesion
Get PDFSurface quality and water-based coating performance of samples prepared by oblique cutting, helical planing, and face milling were studied. Oblique cutting and helical planing generated surfaces with similar features. Samples had little subsurface damage and fibrillation, and few cell lumens were accessible on the surface to favor coating penetration. As a result, these samples had lower surface roughness and wetting properties than face-milled ones. Face-milled samples were defined by more subsurface damage, fibrillation, and open lumens that favored coating penetration. However, the pull-off strength of face-milled samples was significantly lower after accelerated weathering than the oblique-cut or helical-planed samples. Hence, oblique cutting and helical planing are suitable for preparing surfaces of black spruce prior to coating application. No correlations were detected between surface quality parameters and adhesion, which indicates that pull-off tests have to be determined to quantify coating adhesion on surfaces of this wood species
Influence of Machining Parameters on the Tensile Strength of Finger-Jointed High-Density Black Spruce Lumber
Get PDFFinger-jointed softwood lumber is widely used in manufacturing of structural or nonstructural applications such as glued laminated lumber and prefabricated wood I-joists. Black spruce is the most frequently used species for finger-jointed engineered wood products in eastern Canada. However, some key machining parameters must be adjusted according to the properties of the wood to obtain a surface quality suitable for the finger-jointing process. The main objective of this study was to evaluate the effect of cutting speed and chip load on the ultimate tensile strength (UTS) of finger-jointed high-density black spruce. The variables were four cutting speeds and three chip loads. A feather profile was selected with an isocyanate adhesive and an end-pressure of 3.45 MPa. A factorial analysis showed a statistically significant interaction between cutting speed and chip load on UTS and cutting speed was the most significant variable. The influence of chip load on UTS was lower, apparent only at 3260 m/min cutting speed. Suitable finger-jointing could be achieved at 1860-3960 m/min cutting speed with a chip-load of 0.51-1.27 mm. However, the best result was obtained at 3260 m/min cutting speed and 0.89 mm chip load. These results need to be validated in industrial mills to verify tool wear behavior
Properties of Single Bamboo Fibers Isolated by Different Chemical Methods
Get PDFThe objective of this study was to investigate the properties of single Cizhu bamboo fibers isolated by four chemical methods, with and without ultrasonic treatment. Properties tested were static contact angle, lumen size, and mechanical properties (tensile strength, modulus of elasticity [MOE], and elongation) of fibers macerated by four methods: nitric acid and potassium chlorate, sodium hypochlorite (NaClO), hydrogen peroxide and glacial acetic acid (H2O2 + HAc), and sodium hydroxide. The results showed that the maceration time was different among the four methods. Ultrasonic treatment significantly affected the contact angle of all treatments with the exception of H2O2 + HAc. Lumen sizes treated by NaClO were different but cross-sectional area and cell wall area were similar for all other treatments, with and without ultrasonic treatment. Differences in mechanical properties were found among chemicals whereas elongation was similar for all solutions. Ultrasonic treatment accelerated the maceration rate, thus decreasing treatment time and contact angle of single fibers, but had no effect on cell wall area. Tensile strength and MOE were each affected in one solution by ultrasonic treatment, but those effects were within the range of the other solutions
Evaluation of Laminated Veneer Lumber Tensile Strength Using Optical Scanning and Combined Optical-Ultrasonic Techniques
Get PDFNondestructive commercial ultrasonic grading provides laminated veneer lumber (LVL) manufacturers a means for sorting veneer based on average ultrasonic propagation time (UPT) and/or average dynamic modulus of elasticity (MOEd). However, little is known about the influence of veneer defects on strength properties of veneer and LVL. Including veneer defect and growth ring pattern measurements, obtained via optical scanning, was hypothesized to improve LVL static tensile strength (Ft) property predictions. Nondestructive and destructive testing of Douglas-fir (Pseudotsuga menziesii) veneer and LVL was performed to evaluate improvements in LVL Ft property predictions. Various models based solely on density, optical, ultrasonic, and combined system measurements were developed for LVL property predictions. LVL static Ft was best predicted (R2 1/4 0.65) with integrated optical and ultrasonic measurements (ie combined system model), which included average defect, growth ring pattern, and MOEd measurements from the LVL material. Results suggested improved LVL Ft predictions could be achieved by integrating ultrasonic and optical systems. Additionally, the optical model, which included average defect, growth ring, and density measurements, better explained the variation in LVL static Ft values (R2 = 0.58) compared with the MOEd (R2 = 0.51) and UPT (R2 = 0.31) models
Mathematical Approach for Defining Juvenile-Mature Wood Transition Zone in Black Locust and Chestnut
Get PDFThis article defines age of transition from juvenile to mature wood in two ring-porous species, black locust (Robinia pseudoacacia L.) and chestnut (Castanea sativa Mill.). A logistic function was proposed using fiber length and ring width data of three black locust trees, aged 35-37 yr, and five chestnut coppice trees, aged 25-27 yr, from Sithonia Peninsula, Chalkidiki, Greece. The approach proved to be practical and objective in delineating maturity zones, and it was based on rate of change of yearly fiber length. The juvenile wood zone spread to the sixth growth ring from the pith in both species, whereas the demarcation of juvenile and mature wood was at age 12 and 14 yr in chestnut and black locust, respectively. Transition zone width comprised rings 7-12 in chestnut and rings 7-14 in black locust
