2022 Volume 68 Issue 2 Pages 88-96
Material properties of laminae sawn from mature parts of large diameter logs of Japanese larch (Larix kaempferi), such as Young's modulus obtained by the longitudinal vibration method and twist warp, were investigated. These laminae were sawn from Japanese larch logs from Hokkaido, Japan, and had small end diameters of 20 cm or more (≥20-cm logs) and 26 cm or more (≥26-cm logs). Laminae from ≥26-cm logs were sawn from mature wood parts of trucks. Subsequently, the effects of the rough sawn size and crosscut frequency on yield in the production of jointed laminae were examined. Additionally, simulations of stress grades capable of manufacturing glulam and cross laminated timber (CLT) were conducted. Laminae from ≥26-cm logs had higher Young's modulus and smaller twist warp than those from ≥20-cm logs. In this study, the yield in the production of a 30-mm-thick jointed laminae was maximized when the rough sawn thickness was 35 mm and crosscut frequency was once for each rough sawn lamina. The possible stress grade of glulam made of laminae from ≥26-cm logs was as high as E150-F435 in symmetrical mixed-grade according to the Japanese Agricultural Standards for glulam. The major stress grades of CLT made of laminae from ≥26-cm logs corresponded to Mx120 and S120 according to the Japanese Agricultural Standards for CLT. The laminae from mature wood parts of the Japanese larch have the potential to improve yields in the manufacturing of jointed laminae and produce high stress grade glulam and CLT.