Wood and Fiber Science (E-Journal)
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FINITE ELEMENT ANALYSIS OF TENSILE LOAD RESISTANCE OF MORTISE-AND-TENON JOINTS CONSIDERING TENON FIT EFFECTS
Full text linkEffects of tenon fit in its width direction on the tensile load-deflection behavior of T-shaped, round-end, mortise-and-tenon joints were investigated experimentally and analytically. Finite element method (FEM) 3D modeling technique as an analytical tool was used to model the tensile load-deformation behavior of T-shaped, round-end, mortise-and-tenon joints. Experimental results indicated that mean ultimate tensile loads and stiffness of evaluated mortise-and-tenon increased significantly as tenon fit increased from 0 to 0.2 mm with an increment of 0.1 mm. The measured glue-line thickness between mortise-andtenon contact surface was found to be a good indicator of tensile load resistance performance of mortise-andtenon joints evaluated in this study. FEM modeling technique was verified as a valid analytical tool for prediction of tensile load resistances of T-shaped, round-end, mortise-and-tenon joints
Performance of thermally modified Scots pine treated with combinations of some modifying chemicals
Full text linkIn this study, low-temperature thermally-modified (at 140°C) Scots pine (Pinus sylvestris L.) wood samples were impregnated with either one or more modifying agents, including the brown colorant, paraffin wax emulsion (PWE), and an organic preservative (4,5-dichloro-2-octyl-2H-isothiazol-3-one, DCOIT) microemulsion. All wood samples were assessed in dimensional stability, water absorption, the modulus of rupture (MOR), decay and mold resistance, and their weathering performance under both labscale and outdoor exposure. The results showed that 1) the treating groups with PWE showed obvious lower water absorption, and the lowest value appeared in the group treated with brown colorant and PWE (BCPWE); 2) thermal modification improved the dimensional stability of wood, whereas all the further treatments except the group impregnated with PWE slightly counteracted the effect of thermal modification on dimensional stability after water soaking; 3) the MOR of thermally-modified sample showed little change after further treatments; 4) and thermally-modified wood treated with BC-PWE-DCOIT showed the optimal weathering performance with the least color change and the best mold resistance
Analysis of Adhesive Penetration into Wood using Nano-X-ray Computed Tomography
Full text linkThis study focused on the penetration of adhesive into cell lumens and cell walls. Douglas-fir samples containing an iodinated phenol-formaldehyde adhesive were analyzed using nano-X-ray computed tomography (XCT), X-ray fluorescence microscopy, and energy-dispersive X-ray spectroscopy to observe adhesive penetration in cell walls. A gradient of penetration was observed within the cell wall structure. In addition, these nano-XCT datasets were indexed to previous micro-XCT datasets, which gave the ability to link the nanoscale cell wall penetration to microscale penetration in to the porous network of cell lumens.
Pyrolysis kinetics of moso bamboo
Full text linkPyrolysis processes of moso bamboo (Phyllostachys pubescens), bamboo fiber, cellulose, hemicellulose, and lignin were investigated by thermogravimetric analyzer at different heating rates under nitrogen environment. Coatse-Redfern (CR) and Kissinger-Akahira-Sunose model were used to calculate pyrolysis kinetics. The results showed that the thermal degradation occurred during 300-400°C and 200-300°C for cellulose and hemicellulose, respectively. The lignin degraded from 200°C to the end of the process. The pyrolysis process of moso bamboo could be divided into three steps, which all occurred during 130-560°C. The thermal decomposition of bamboo fibers occurred during 232-390°C. As the heating rate increased, the pyrolysis processes of all samples shifted to higher temperatures. The minimum activation energy of each sample was found at different heating rates from the CR model. The results will be helpful to understand the pyrolysis mechanism of moso bamboo to effectively design its thermochemical conversion process.
Preparation and application of high performance corn starch glue in straw decorative panel
Full text linkTo develop a production technique for nonformaldehyde-tolerant straw veneer by using a biomass-based adhesive, this study used corn starch as the main material and combined it with polyvinyl alcohol solution, flour, and polyisocyanate prepolymer to prepare a corn starch adhesive without formaldehyde. The adhesive was applied to the straw board substrate veneer used for decorative board products, and the production process and production properties were evaluated. The results showed that the corn starch adhesive was excellent, and indexes of the product reached the performance requirements of the artificial board in GB/T 14074-2006. The surface bonding strength of the mattress board veneer decorative cover was greater than 0.40 MPa, and the physical and mechanical properties met or exceeded the national standard (GB/T 15104-2006) for a decorative veneer. Formaldehyde emission in the production process was less than 0.05 mg/L. These results have great significance in the improvement of the practicality of biomass-based adhesives in the manufacture of wood-based panels.
TRACHEID EFFECT SCANNING AND EVALUATION OF IN-PLANE AND OUT-OF-PLANE FIBER DIRECTION IN NORWAY SPRUCE TIMBER
Full text linkLocal fiber direction is decisive for both strength and stiffness in timber. In-plane fiber direction on surfaces of timber can be determined using the so-called tracheid effect which is frequently used in both research and industry applications. However, a similar established method does not exist for measuring the out-of-plane angle, also known as diving angle. The purposes of this article were to evaluate if the tracheid effect can also be used to determine, with reasonable accuracy, the out-of-plane angle in Norway spruce and to verify an existing mathematical model used to calculate the fiber direction in the vicinity of knots. A newly developed laboratory laser scanner was applied for assessment of fiber directions in a single Norway spruce specimen containing a knot. It was assumed that the specimen had a plane of symmetry through the center of the knot, and by splitting the specimen through this plane into two parts, it was possible to make measurements on orthogonal planes. The results showed that the out-of-plane angle could not be determined with very high accuracy and the difficulties related to this objective were analyzed. Regarding the mathematical model of fiber direction in the vicinity of a knot, fiber directions calculated on the basis of this model agreed well with experimentally obtained fiber directions, but successful application of the model requires that the geometry of the knot is known in detail
STRENGTH AND STIFFNESS PROPERTIES OF SMALL CLEAR SPECIMENS TAKEN FROM COMMERCIALLY PROCURED NO.2 2×8 AND 2×10 SOUTHERN PINE DIMENSION LUMBER
Full text linkThis technical note focuses on the modulus of rupture (MOR) and modulus of elasticity (MOE) of small clear southern pine (Pinus spp.) test pieces cut from commercially procured full-size lumber specimens. A production-weighted sample of 476 No.2 grade 2×8s and 2×10s was acquired from retail establishments throughout the southern pine producing region. The specimens were subjected to static bending tests to measure MOR and MOE. From 447 of those specimens, a single small clear beam (3.8 × 3.8 × 61 cm) was extracted and subjected to a static bending test of the same properties. Two-sample t tests showed no evidence of statistical difference in either mean MOE or MOR between the small samples taken from the 2×8s and the 2×10s. Bivariate correlations and r2 values showed an overall weak relationship (r = 0.30, r2 = 0.09) between the small clears and their parent specimens in respect to MOR. A more moderate relationship (r = 0.60, r2 = 0.36) was found in respect to MOE between small clears and their parent specimens. In addition, a relatively strong relationship was found between the MOR and MOE values of the small clears themselves (r = 0.77, r2 = 0.59). It is intended that subsequent publications will examine similar relationships in other grades and sizes
Fire Safety of CLT Buildings in New Zealand and Australia
Full text linkThis article summarizes the design procedures for ensuring fire safety in cross laminated timber (CLT) buildings in Australia and New Zealand, with reference to the Building Codes in both countries. New Zealand and Australia are located close together geographically and have similarities in some areas of building control, but prescriptive code requirements are often very different. There is a small but growing local CLT industry, but CLT materials for large projects are imported from Europe
DISTRIBUTIONS OF MOE AND MOR IN A FULL LUMBER POPULATION
Full text linkReliability calculations for lumber products ultimately depend on the statistical distributions that we use to model lumber stiffness and strength. Fits of statistical distributions to empirical data allow researchers to estimate the probability of failure in service. For these fits to be useful, the theoretical statistical distributions must be good matches for the empirical lumber property populations. It has been common practice to assume that the MOE of a grade of lumber is well-fit by a normal distribution, and the MOR of a grade of lumber is well-fit by a normal, lognormal, or two-parameter Weibull distribution. Recent theoretical results and empirical tests have cast significant doubt on these assumptions. The exact implications of the theoretical results depend on the distributions of full (mill-run) MOE and MOR populations. Mill-run data have not yet appeared in the literature. Instead, studies have focused on subpopulations formed by visual or machine stress rated (MSR) grades of lumber. To better understand the implications of the recent theoretical results, we have investigated the statistical distributions of mill-run MOE and MOR data. An ungraded mill-run sample of 200 southern pine 24 s produced at a single mill on a single day was subjected to both nondestructive (transverse vibration and longitudinal stress wave) evaluation and static bending tests to determine its MOE and MOR values. Various distributions were fit to the MOE and MOR data and evaluated for goodness-of-fit. The results suggest that mill-run MOE might be adequately modeled by a normal distribution or a mixture of two normal distributions, mill-run MOR might be adequately modeled by a skew normal distribution or a mixture of two normals, and neither mill-run MOE nor mill-run MOR is well-fit by a Weibull distribution.