Experimental and numerical assessment of the orthotropic imbibition dynamics of wood

Abstract

ABSTRACT The moisture content of wood is changed during manufacturing processes, such as drying and impregnation. Understanding the water transport in wood is helpful for optimizing the manufacturing technology and improving the durability of wood products. Herein, the one-side imbibition tests of Chinese fir and poplar were carried out via direct contact with a water-saturated sponge. Imbibition amounts and orthotropic kinetics were evaluated by X-ray densitometry, where wood exhibited non-uniform and directional behaviors for water imbibition and there were variations in behavior between Chinese fir and poplar. More water uptake and faster migration were observed for poplar, while water preferentially accumulated at the wetting front for Chinese fir. The effective imbibition height of poplar was significantly higher than Chinese fir, regardless of orientation direction. Within the growth rings, Chinese fir showed heterogeneous water uptake, and faster water migration in latewood was observed. Imbibition height in a single fiber was simulated as a function of cell wall ratio, and the influences of anatomical factors on water movement were explored. These simulation assessments were consistent with the results of the one-side imbibition tests. These findings help to explain the water transport mechanism at the mesoscale and interactions between wood and water.