Impact of tree age and grain orientation on the shrinkage and swelling of Acacia mangium wood from Sabah, Malaysia

Abstract

The aim of this study was to determine the impact of tree age and grain orientation on the shrinkage and swelling of Acacia mangium wood.   The specimens from eight ages of tree 3, 5, 7, 9, 11, 13, and 15 year-old were tested for water absorption, swelling, shrinkage, Volumetric Shrinkage and Swelling according to the ASTM D 143-94.   Results show that Acacia mangium wood swells in both radial and tangential directions, indicating that a linear relationship can be established with increasing water content over time. At a grain angle of β = 90.0°, a significant negative correlation (R² = 0.98) was observed between the percentage of dimensional change and longitudinal shrinkage.  There was no strong correlation (R² = 0.50) between the longitudinal swelling time and the dimensional change. However, a relationship (R² = 0.66) was indicated between the percentage of tangential and radial swelling over time at an angle of β = 0.0°.  Additionally, it was investigated that the tangential shrinkage percentage of Acacia mangium wood increased from 0.10% to 2.758%, while the radial shrinkage increased from 0.095% to 2.385%.  The longitudinal shrinkage increases dramatically from 1.548% to 3.105%.  Micrograph images obtained using scanning electron microscopy (SEM) and 3D optical microscopy were included in this study to improve the results by offering detailed visual insights into fibre orientation and the structure of the cell wall.