Influence of Moisture Sorption on the Strength of Sugar Maple Wood in Tangential Tension

This research confirms that, at a given equilibrium moisture content, the strength perpendicular to the grain is less after desorption than after adsorption. This behavior, called second-order effects of moisture sorption, has been established for sugar maple wood in tangential tension. For the compliance coefficient s33, these effects only halve those measured in radial compression (s22)- Also, it is shown that second-order effects could be present, though to a lesser extent, up to failure. Near the oven-dry condition, some internal tensions were responsible for a decrease of the ultimate tensile stress in the adsorption state. A subsequent remoisturing eliminated those tensions, seemingly built up during the preliminary drying of samples. Finally, near the fiber-saturation point, a loss of bound water may take place in the presence of free water and thus affect significantly the strength of wood across its grain