Effects of Laser Incising on Compressive Strength and Physical Properties of Sapwood, Transition Zone, and Mature Wood of Oriental Spruce (Picea orientalis)

Abstract

Oriental spruce (Picea orientalis (L.) Peterm.), a refractory species of low natural durability, requires adequate impregnation to attain a longer service life in high-risk end uses (use classes 3 and 4). Improving the permeability of such species through laser-incising pretreatment is therefore important, provided that the physical and mechanical properties of the different wood portions (sapwood, transition zone, and mature wood) are not adversely affected. In this study, the weight loss, density, moisture content, shrinkage and swelling, and compressive strength parallel to the grain of these wood portions were evaluated after laser incising. The depth and diameter of the incised holes and the growth-ring characteristics were also examined. The sapwood and transition-zone samples had greater latewood layer width and higher latewood proportion than the mature wood. Laser incising reduced radial and tangential shrinkage and swelling in mature wood. Compressive strength parallel to the grain of the mature wood was lower in the laser-incised samples than in the controls. In the transition zone, the radial hole diameter was higher than the tangential diameter.