Compression properties of Japanese cedar (Cryptomeria japonica) treated with resin impregnation under loading perpendicular to the grain

Abstract

The compression properties of wood perpendicular to the grain is an important resistance mechanism in timber joints, especially wood-to-wood joints. Hence, improving the compression properties of wood is essential to developing timber joints with high resistance performance. In this study, we attempted to improve the compression properties using a resin impregnation technique. Three compression tests were conducted: loading at the full surface of the specimen, loading at the local part of the specimen with the unloaded part expanding in the tangential direction, and loading at the local part of the specimen with the unloaded part expanding in the longitudinal direction. Two types of resins were used: urethane and acryl. For compression loading on the full surface, the stiffness was increased by resin impregnation in the case of acryl impregnation. However, the yield load did not increase significantly. In the cases of compression loading in the local part and unloaded part expanding in the tangential direction, the stiffness increased when acryl was used, and the yield load increased when both resins were used. Significant increment in the properties were observed when the local compression load acted on the specimens with the unloaded parts expanding in the longitudinal direction. When urethane and a 10 mm incision depth were used, the stiffness and yield load increased 1.35 and 2.54 times, respectively. When using acryl and a 10 mm incision depth, the stiffness and yield load increased 1.64 and 2.93 times, respectively.