Wood As a Bimodular Material

Wood is usually considered to be a material with equal stiffness in tension and compression, but this supposition is not uniformly supported by experimental evidence. On the basis of data in the literature, the authors believe that there is sufficient evidence to conclude that some woods, particularly hardwoods, exhibit bimodular behavior. For the hardwood data analyzed here, the ratio of Young's modulus in tension to Young's modulus in compression (Et/Ec) averaged 1.08 and ranged as high as 1.28. Comparisons with composite materials with known bimodular behavior suggest that fiber displacement around rays (and the resulting fiber curvature) might be one cause of this behavior. Some data also indicate that the equality of the tension and compression moduli may be affected by the moisture content. There are similarities with synthetic fibers which suggest that wood fibers might also be bimodular, but the question of whether bimodular behavior can be ascribed to both undelignified fibers and solid wood remains unanswered

Determination of Boron Diffusion Coefficients in Wood

The unsteady-state diffusion of boron through southern pine (Pinus spp.) was investigated at various moisture contents, temperatures, and treatment conditions. The fastest rates of diffusion were observed in the longitudinal direction, followed by the radial and the tangential directions. The diffusion rate increased with time in all directions. The longitudinal diffusion rate increased rapidly with moisture content (MC), while a slow increase in the radial diffusion rate was observed at MCs above 90%. Moisture conlent did not affect the rate of tangential diffusion within the range of MCs in this study (70-110%). The effect of temperature on boron diffusion rates was more pronounced than the effect of MC. The diffusion rate increased with temperature, although slight direction-dependent differences were observed. A repeated dip-treatment increased the rate of diffusion in the tangential direction, but only small differences were found in the longitudinal and the radial directions. No other data were found in the literature for comparison.Average values of the diffusion coefficients were calculated to predict the concentration profile of boron in wood under various conditions. The longitudinal diffusion coefficients were 10 to 20 times larger than the radial diffusion coefficients, and the radial diffusion coefficients were two to four times larger than the tangential diffusion coefficients. The use of the average boron diffusion coefficients caused some differences between real and predicted values in the early stages of diffusion, but the potential for practical use was demonstrated

Mechanism of Voc Release From High-Temperature Southern Pine Lumber Drying

Hydrocarbon (Method 25A) emissions from drying southern pine lumber have been measured in full-scale experiments. The mechanism proposed comprises three components: release of turpentine dissolved in the surface layer of water on the wood, water-mediated transport of turpentine from the interior of the wood to the surface, and evaporation of turpentine during the falling rate period. The result allows the total Method 25A release to be estimated without knowledge of the airflow through the kiln. Full-scale Method 25A emissions from lumber can be predicted from laboratory work on sawdust, indicating that the mechanism is independent of the type of furnish

Wood as a bimodular material

"February 1992""To be submitted to Wood and Fiber Sci.

Z-directional pore volume distribution of pigment films

"June 1991.""Submitted for CPPA.

Release and measurement of VOC emissions from lumber kilns

"January 2001."Submitted to International Environmental Conference, April 22-25, 2001, Charlotte, North Carolina

Mechanism of VOC release from lumber kilns

"September 2001."Submitted to Wood and Fiber Science

Mechanism of VOC release from high-temperature Southern pine lumber drying

"June 2002."Submitted to Corrosion Reviews

Image analysis of an LWC paper reveals wire mark in the print density variation

"September, 1987.""This manuscript is based on results obtained in IPC Project 3501-5 and was presented at the TAPPI Engineering Conference in September issue of Tappi Journal.

Dynamic measurements of stratified consolidation in a press nip

"June 1992.""Submitted to TAPPI 1992 Engineering Conference, September 14-17, 1992, Boston, Massachusetts.