Comparison of the Creep Behavior of A Basswood Waferboard to that of Solid Wood

Flexural creep at 50, 60, 70, and 80% RH for parallel- and perpendicular-to-grain solid wood was compared with a laboratory-produced particleboard of the same species. Accelerated flexural creep rates at high relative humidities did not follow trends of wood stressed in tension and compression perpendicular-to-grain. Creep in particleboard lies between that parallel- and perpendicular-to-grain

Predicting Flexural Creep in Particleboard

An analytical expression that relates flexural creep behavior to time, temperature, and stress was used in this study to predict the long-time performance of a commercial particle-board from the short-time behavior exhibited in a conventional static bending test. The particleboard exhibited a hyperbolic deflection—log time relationship under all conditions studied while deflection predicted from tests at elevated temperature was nearly linear with log of time. Both Larson-Miller and Goldfein parameters provide reasonable estimates at low stress levels. At higher stress levels, the Larson-Miller parameter provides more conservative estimates of the behavior in the 1000-3000 hr range. Neither method predicts accurately the increasing creep rates at the high stress levels and longer times

Drying Rates of Wood Chips During Compression Drying

Compression drying is basically a process of forcing the free water in wood to move under high hydrostatic pressure through a solid structure. Fundamental information regarding the time-dependent characteristic of compression drying is necessary to develop efficient commercial processes. The purpose of this study is to provide an initial evaluation of the effect of some factors—pressure, wood density, and particle (chip) size—on free water extraction.Five species—aspen, balsam fir, jack pine, red maple, and red oak—were tested in this study. For each species both typical pulp size chips and particles from hammermilled chips were used. Drying rates were determined under constant ram face pressures at 500 psi, 1,000 psi, 1,500 psi, and 2,000 psi, respectively. The concept of drying rate is one of the important factors in dealing with compression drying, especially in designing dewatering pressure cycles.The most efficient compression drying is achieved during the first two minutes. Drying rates are negligible after 3 to 4 minutes of constant pressure in the 500 to 2,000 psi range. The analysis of variance for species shows highly significant differences in final moisture contents. Size of chips had a significant effect on final moisture contents Compressed density of hammermilled chips is slightly higher than that of unrefined chips. High density chips require higher pressure to initiate effective drying rates

Studies of Flexural Creep Behavior in Particleboard Under Changing Humidity Conditions

The effect of changing relative humidity, to cause simple adsorption or cyclic adsorption-desorption, on the creep behavior of particleboard, oriented particleboard, and plywood was studied. For the particular boards studied, creep response was sensitive to the highest humidity to which the boards were subjected. Behavior of both urea and phenolic resin-bonded particleboards was similar. When stressed below approximately 20% of maximum static bending strength, flexural creep was linear with stress level. An increased rate of adsorption had a smaller overall effect than the greatest humidity level to which the board was subjected. A shavings/residue-type particleboard demonstrated accelerated creep behavior above about 75% RII. Although plywood and oriented particleboard had increased creep at the higher humidity levels, there did not appear to be as definite a point where creep rate accelerated. Flexural creep behavior under a single concentrated load was qualitatively similar to that under simple flexural stress

Forest Products Research at U.S. Universities in 1982

This is a survey of professional staffing, research emphasis, and funding levels of the 37 universities in the United States that conduct forest products research. The survey was conducted by the Subcommittee on Forest Products Research, National Planning Group for Forestry (NPG-2)