Treesearch

Gamma irradiation is a commonly used method of sterilization of wood specimens prior to decay testing. As part of a larger series of studies, an investigation was made into the effects of gamma irradiation on flexural bending strength properties and its corresponding relationship to changes in lignin and hemicellulosic contents of wood after exposure to various dose rates and total dosage. Effects of irradiation were compared with effects of a steam sterilization method. Flexural strength was reduced in response to a long exposure to radiation. Klason lignin and galactan contents were also...

Using sustainable building materials is gaining a significant presence in the US. This study examined hardwood lumber manufacturing using life-cycle inventory methodology. Material flow and energy use were identified for hardwood sawmills in northeastern US. A hardwood log volume conversion of 43.7% to planed dry lumber was found. Values of 608 MJ/m3 of electrical and 5800 MJ/m3 of thermal energy were determined for the manufacturing of planed dry hardwood lumber where mostly green wood residues were burned on-site for energy. Emission data produced from modeling estimated biomass and...

N-methyl amino catechol borate (1), N-methyl amino-4-methyl catechol borate (2), N-methyl amino-4-t-butyl catechol borate (3), and N-methyl amino-2, 3-naphthyl borate (4) were synthesized by reflux of boric acid with a diol in solvent N,N-dimethyl formamide. The aminoborates were characterized by proton nuclear magnetic resonance spectroscopy, FTIR spectroscopy and elemental analysis. Wood impregnated with aminoborate 1, 3, or 4 after 2-wk water leaching was able to prevent decay by a brown-and white-rot fungus. Thermogravimetric analysis showed that wood impregnated with aminoborate 1 or...

Moisture gradient in wood and wood composites is one of most important factors that affects both physical stability and mechanical performance. This paper describes a method for measuring moisture gradient in lumber and engineering wood composites as it varies across material thickness. This innovative method employs a collimated radiation beam (x rays or [gamma] rays) emitted from a radiation source that discretely scans the material in steps or continuously through its thickness direction. A radiation detector on the other side detects intensities of the transmitted beam, which directly...

It has been argued that repetitive member allowable property adjustments should be larger for high-variability material than for low-variability material. We report analytic calculations and simulations that suggest that the order of such adjustments should be reversed. That is, given the manner in which allowable properties are currently calculated, as the coefficient of variation of the strength distribution of individual elements increases, the upward repetitive member adjustments (if any) of assemblies constructed from these elements should decrease.

Exposure to elevated levels of atmospheric CO2 for a period of 17 years resulted in small but statistically significant decreases in wood basic specific gravity and number of rays per millimeter. Other anatomical characteristics (percentages of tissues, number of vessels per square millimeter, vessel diameters, and fiber wall thickness) were unaffected by treatment. Differences due to distance from pith were important, but cardinal direction (north, south, east, west) was not.

To satisfy the increased demand for forest products, much of future timber supply is expected to be from improved trees grown on managed plantations. This fast growth resource will tend to be harvested in short-age rotations and will contain higher proportions of juvenile wood than those of current harvests. In anticipation of this resource, definitive information is needed about the influence of juvenile wood on lumber properties so that grading rules or the associated allowable design stresses can be modified as needed. Most information developed to date has concentrated on ultimate...

Minimizing wood shrinkage is a priority for many wood products in use, particularly engineered products manufactured to close tolerances, such as wood propellers for unmanned surveillance aircraft used in military operations. Those currently in service in the Middle East are experiencing performance problems as a consequence of wood shrinking during long-term storage at low equilibrium moisture content conditions prior to installation. To evaluate the extent of shrinkage, seven sugar maple (Acer saccharum) veneer propellers were dried from 11% to 3% moisture content in a controlled...

A cantilever-beam vibration-testing apparatus has been developed to provide a means of dynamic and non-destructive evaluation of modulus of elasticity for small samples of wood or wood-composite material. The apparatus applies a known displacement to a cantilever beam and then releases the beam into its natural first-mode vibration and records displacement as a function of time. That frequency and amplitude attenuation is then used to calculate the dynamic material properties of the cantilever beam. The dynamic testing is quick and calculates the dynamic modulus and loss-tangent damping...