Drying Stress and Check Development in the Wood of two Oaks

Abstract

This study was designed to relate the checking behaviour of drying wood as observed under light and electron microscopes to moisture gradient, stress development, and mechanical properties of drying wood during early stages of drying . Woods used were northern red oak (Quercus rubra) and narrow-leaved oak (Cyclobalanopsis longinux).Wood was dried from the green condition at 40, 60, and 80°C as wafers. Wafers were sealed to retard drying from the transverse surfaces. Moisture gradient was measured during drying on thin slices removed from the tangential faces. Drying stresses were estimated for the same times and drying conditions by finite element modeling using the ABAQUS program modified to take into account time-related deformation. Stiffness and strength in tension perpendicular to the grain in the tangential direction were determined at 20, 40, 60, and 80°C for specimens in the green conditions and at 15% moisture content.