Influence of Juvenile Wood on Dimensional Stability and Tensile Properties of Flakeboard

The purpose of this study was to determine if juvenile wood adversely affects the linear expansion, water adsorption, and thickness swell of aligned flakeboard. Literature on juvenile wood properties and their effects on product performance was reviewed. Veneer and lumber cut from 35-year-old plantation-grown loblolly pine were segregated by age and used to manufacture plywood and flake-board. As expected, longitudinal linear expansion of the juvenile (0 to 12 years old) veneer was greater than that of mature (13+ years old) veneer. At several levels of humidity exposure, linear expansion of symmetrical cross-laminated plywood made from the juvenile veneer was greater than that of plywood made from mature veneer. Significant increases in the linear expansion of three-layer cross-oriented flakeboard were also attributed to juvenile wood. Differences in the linear expansion of single-layer directional aligned flakeboards made from juvenile wood and from mature wood were not statistically significant for the most part. Analysis did show that test results were affected by tree-to-tree variation in wood age and sample variations. Accurate predictions of dimensional stability in three-layer cross-aligned panels were made using tensile and linear expansion properties derived from the directional flakeboard

Concerns About a Variance Approach to X-Ray Diffractometric Estimation of Microfibril Angle in Wood

In this article, we raise three technical concerns about Evans' 1999 Appita Journal "variance approach" to estimating microfibril angle (MFA). The first concern is associated with the approximation of the variance of an X-ray intensity half-profile by a function of the MFA and the natural variability of the MFA. The second concern is associated with the approximation of the natural variability of the MFA by a function of the MFA. The third concern is associated with the fact that the variance approach was not designed to handle tilt in the fiber orientation. All three concerns are associated with potential biases in MFA estimates. We raise these three concerns so that other researchers interested in understanding, implementing, or extending the variance approach or in comparing the approach to other methods of estimating MFA will be aware of them