Wood and Fiber Science (E-Journal)
Not a member yet
2592 research outputs found
Sort by
EVALUATING BEARING PROPERTIES OF WOOD PEG CONNECTION USING FOUR DIFFERENT TEST METHODS
Get PDFThe objective of this study was to evaluate appropriate test methods for the bearing properties of wood peg connection using four different test methods: ASTM D 5764 (2013), the method of Church and Tew (1997), the method of Schmidt and Daniels (1999), and the method of Schmidt and Mackay (1997). Bearing properties of wood peg connection were compared using digital image correlation. Although ASTM D 5764 (2013), the method of Church and Tew (1997), or the method of Schmidt and Daniels (1999) could not differentiate bearing properties by peg orientation, the method of Schmidt and Mackay (1997) could differentiate such properties by peg orientation. ASTM D 5764 (2013), the method of Church and Tew (1997), and the method of Schmidt and Daniels (1999) created unrealistic strain distributions which affected yield load determined from the load–displacement curve. The method of Schmidt and Mackay (1997) showed the highest strain distribution at the bearing area between the wood peg and the main member, resulting in load–displacement curve by bearing mainly. These results suggest that the method of Schmidt and Mackay (1997) could determine the bearing properties of wood peg connection.
INVESTIGATION OF DECAY RESISTANCE OF ALKALINE COPPER, UREA-FORMALDEHYDE, AND PHENOL -FORMALDEHYDE RESINS
No full textThe decay resistance of modified fast-growing poplar lumber with ion-based preservative and thermosetting resins were determined in laboratory and field stake tests. Commercial alkaline copper quat-type D (ACQ-D), thermosetting phenol–formaldehyde (PF) resin with varying concentrations, and urea–formaldehyde (UF) resin were used to improve decay resistance of low-grade fastgrowing poplar. The results indicated that the concentrations of PF and weight gains of resin-modified specimens were highly correlated, and target resin retains can be achieved from resin concentration. The retention rates of ACQ of 1.1% concentration, UF of 41.5% concentration and PF of 10% concentration were 6.72, 18.43, and 7.31 kg/m3, respectively. For PF, the retention rate is linearly related to concentration. The mass losses (ML) for the untreated, ACQ-treated, and UF-treated specimens were 26.34%, 8.91%, and 11.66% after 12 wk of incubation in laboratory, respectively. The ML for the treated specimens were 9.74%, 7.32%, 3.14%, 2.38%, and 2.41% for PF impregnated wood at concentrations of 10%, 15%, 20%, 25%, and 40%, respectively, after 12 wk of incubation in the laboratory.
RECENT DEVELOPMENT IN CLT CONNECTIONS PART I: IN-PLANE SHEAR CONNECTION FOR CLT BRACING ELEMENTS UNDER STATIC LOADS
Get PDFCross-laminated timber (CLT) is already being used successfully in residential, commercial, and industrial buildings. The use of computerized numerical control (CNC) automatic processing machines and high degree of prefabrication in combination with relatively large elements lead to short erection time on building site and to potentially cost-effective constructions. High in-plane shear strength and stiffness of the CLT itself make CLT members especially suited for bracing elements with in-plane loads. However, some available connection techniques show limited load-carrying capacities and stiffness values in comparison with the shear capacity of CLT. To better use the potential of CLT under in-plane loading, so called contact joints were developed with increased stiffness and load-carrying capacities using CNC automatic processing machines.
DEFECT DETECTION AND QUALITY ASSESSMENT OF HARDWOOD LOGS: PART 1—ACOUSTIC IMPACT TEST AND WAVELET ANALYSIS
Get PDFThe objective of this study was to determine the technical feasibility of combining acoustic wave data with high-resolution laser scanning data to improve the accuracy of defect detection and quality assessment in hardwood logs. This article (Part 1) focused on exploring the potential of an acoustic impact testing method coupled with advanced waveform analysis to detect internal decay of hardwood logs and classify logs in terms of log quality and potential board grade yields. Twenty-one yellow-poplar (Liriodendron tulipifera) logs obtained from the Central Appalachian region were evaluated for internal soundness using an acoustic impact testing technique. These logs were then sawn into boards, and the boards were visually graded based on National Hardwood Lumber Association grading rules. The response signals of the logs from acoustic impact tests were analyzed through moment analysis and continuous wavelet transform to extract time-domain and frequency-domain parameters. The results indicated that the acoustic impact test coupled with wavelet analysis is a viablemethod to evaluate the internal soundness of hardwood logs. Log acoustic velocity alone was able to identify the very low-end logs that have the most severe internal rot or other unsound defects but failed to identify the logs with poor geometry that resulted in very low recovery. Time centroid, damping ratio, and combined time- and frequency-domain parameters were found effective in predicting log quality in terms of board grade yields. Log segregation based on time-domain (time centroid and ρ/Tc**2) and frequency-domain (damping ratio and Ed/ζ**2) parameters showed a positive correlation with the board grade yields.
ORTHOGONAL CUTTING STUDY OF WOOD AND KNOTS OF WHITE SPRUCE
Get PDFWood defects can cause important loss of raw material and tooling during wood machining. White spruce (Picea glauca [Moench] Voss) is a wood species widely used in Canada, which presents an important occurrence of knots. These knots provoke several problems during machining affecting the final surface quality. The main objective of this research was to evaluate the orthogonal cutting forces and surface quality of white spruce wood with and without the presence of knots. Wood pieces of 12% MC were machined at four rake angles (10°, 20°, 30°, and 40°). Cutting forces and roughness were measured on clear wood (90°-0° cutting direction), knot (90°-90° cutting direction), and surrounding knot areas (before and after knot). Wood density in matched pieces were analyzed by X-ray densitometry. The results showed that the density of knots was in average 2.4 times higher than the density of clear wood. However, cutting forces of knots were up to eight times higher than those of clear wood. For all cutting areas, the parallel force increased as rake angle decreased. However, the sensitivity of cutting forces to changes in rake angle was higher for knots than for clear wood. Furthermore, surface roughness was positively correlated with the cutting forces. The rake angle of 40° produced the smaller cutting forces and lower surface roughness for clear wood, knots, and surrounding knot areas
Vertical Density Profile and Internal Bond Strength of Wet-Formed Particleboard Bonded with Cellulose Nanofibrils
Get PDFIn this study, the effects of cellulose nanofibrils (CNFs) ratio, press program, particle size, and density on the vertical density profile (VDP) and internal bond (IB) strength of the wet-formed particleboard were investigated. Results revealed that the VDP was significantly influenced by the press program. Pressing using a constant pressure (CP) press program produced panels with flat-shaped profile. Panels made from a constant thickness (CT) press program produced U-shaped profile. The CNF ratio and density also influenced the VDP especially for the CT panels. As the CNF ratio increased, there were noticeable increases in face density, while the core density slowly increased. The CT panels had the lowest core density compared with the CP counterparts, thus significantly lowering the IB. The IB of CP panels increased with the increase of CNF ratio, but the trend for CT panels was different. For the 10% CNF ratio, the IB increased as the core density increased. For the 15% and 20% CNF ratios, the IB decreased as the core density increased. For CP panels, the minimum core densities were higher and thus the IB was significantly higher. None of the panels met the IB values for high-density standard particleboard. All CP panels met some of the medium-density standard IB values and all the low-density standard IB values. However, for the CT panels, only those with 15% and 20% CNF ratio marginally met the low- and medium-density particleboard standard. Trends show that increased CNF ratio and higher pressure could improve IB properties for the high-density particleboard
USING NONDESTRUCTIVE TESTING TO IDENTIFY PREMIUM GRADES IN SOUTHERN PINE AND DOUGLAS-FIR UTILITY CROSSARMS
Get PDFUnlike lumber, wood utility crossarms are not currently available in premium grades that indicate a higher level of performance in service. Previous research has shown that nondestructive testing (NDT) techniques are able to predict performance properties of solid wood products with considerable accuracy. The aim of this study was to determine the suitability of NDT methods for predicting the stiffness and strength properties of wood utility crossarms and possibly aiding in the identification of a premium grade that exhibits higher average performance values. Samples of Douglas-fir and southern pine were subjected to multiple NDT technologies to estimate modulus of elasticity (MOE). Each specimen was also measured for MOE and modulus of rupture (MOR) with a static bending test. Bivariate correlations and corresponding R2 values showed that Fibre-gen’s Director HM200 and Metriguard’s E-computer were the most accurate NDT devices among those tested for predicting both MOR and MOE. Means tests also suggested that the devices could possibly be used to identify a premium grade that shows significantly higher average performance values
EFFECTS OF CUTTERHEAD DIAMETER AND LOG INFEED POSITION ON SURFACE QUALITY OF BLACK SPRUCE CANTS PRODUCED BY A CHIPPER-CANTER
Get PDFThe effects of the cutterhead diameter and log infeed position on surface quality of black spruce (Picea mariana [Mill] B.S.P.) cants processed by a conical chipper-canter were evaluated. Three cutterhead diameters (345.2, 448.7, and 661.5 mm) combined with three infeed positions or vertical distance from the cutterhead axis to the bedplate on which the log was supported, were studied. The nominal linear cutting speed was fixed at 23.5 m/s. Rotation and feed speeds were adjusted to obtain a nominal feed per knife (chip length) of 25.4 mm. For each cutting condition, two sides of the log were machined at either frozen or unfrozen wood temperatures. Surface quality was analyzed according to waviness and roughness standard parameters. Results showed that surface quality was affected by the cutterhead diameter, infeed position, and wood condition (frozen and unfrozen). Surface quality improved as the vertical distance from the cutterhead axis to the bedplate increased. The global action of the bent knife induced some vibration into the canting edge, which could explain the variation in surface quality among infeed positions. Moreover, frozen logs produced smoother surfaces compared with unfrozen logs. In addition, the effect of the angle of the canting edge with respect to the wood grain on cant surface quality depended on the orientation of the growth rings and on the wood condition (frozen and unfrozen). These results give useful information to improve surface quality within the studied range of infeed positions and cutterhead diameters
RELATING WOOD CHEMISTRY AND STRENGTH: PART II. FUNDAMENTAL RELATIONSHIPS BETWEEN CHANGES IN WOOD CHEMISTRY AND STRENGTH OF WOOD
Get PDFABSTRACTIn Part I of this series, the relationship between physical properties and chemistry andanatomy of wood were reviewed (Winandy 2016). This Part II article explores a fundamental relationship between the mechanical properties and the chemical composition of wood and how degradation of its individual chemical components affects strength loss. It then presents a proposal for a universal theory as to the fundamental mechanism between wood strength loss and changing wood chemistry. That theory purports that the desequencing of the complex lignocellulosic structure of woody materials involves the same systematic series of processes during either biological, chemical, or thermal deterioration. The goal of this article is to create a better understanding of how changes in wood chemistry fundamentallyinfluence wood strength.
Combustibility of Boron-Containing Fire Retardant Treated Bamboo Filaments
Get PDFAbstract:As an indoor decorative material, bamboo filaments should be treated with flame retardants for safe use. The effects of different treatment conditions on boron loading of flame retardants (boric acid/borax 1:1) in bamboo filaments were investigated by single factor experimental design. Furthermore, effects of boron-containing flame retardants on combustibility of bamboo filaments were evaluated by cone analysis. The results showed that boron loading in treated bamboo filaments increased distinctly as treatment duration, temperature, or solution concentration increased. Compared with untreated and ultraviolet (UV)-treated bamboo filaments, heat release decreased obviously in treated bamboo filaments with greater boron loading, heat rates were only 50% and 30% of untreated bamboo filaments and UV bamboo filaments, and the total amount of heat release was decreased by 39.7% and 56.5%, respectively. During the combustion process, boron-containing flame retardants had excellent smoke suppression efficacy and total smoke release was decreased by 86.1% and 91.1%, respectively. As a result, boron-containing flame retardants promote carbon residue production of treated bamboo filaments and decrease themass loss during fire.