Logging age for the Bambusa rigida culm based on physical-mechanical properties.

Abstract

To optimize the logging age of the Bambusa rigida culm, physical-mechanical properties of bamboo culms aged from 0.5 to 4.5 years were sampled by age with sample size of 10 for each age bamboo culm and evaluated according to national standards from Testing Methods for Physical and Mechanical Properties of Bamboos (GB/T 15780-1995) and the radial bending test method. Data from different bamboo ages were statistically analyzed with ANOVA. Results showed that (1) the moisture content of green bamboo and volumetric shrinkage decreased with an increase in bamboo age from 0.5 to 4.5 years; whereas, the basic density increased overall. Also, (2) compression strength parallel to the grain, modulus of rupture (MOR), and modulus of elasticity (MOE) reached a maximum at 3.5 years of age, and shear strength parallel to the grain had already leveled off at this age. (3) From the base to the top portion of the bamboo culm, moisture content of the green bamboo and volumetric shrinkage decreased; whereas, the basic density, compression strength parallel to the grain, shear strength parallel to the grain, MOR, and MOE all increased. Noteworthy was that shear strength, MOR, and MOE decreased at the top portion of the bamboo at age 4.5, which reflected the aging phenomenon of bamboo culms. (4) The 3.5-year-old bamboo culms had a moisture content of green bamboo, 60.67%; basic density, 0.72 g·cm-3; volume shrinkage, 12.54%; compression strength parallel to the grain, 82.41 MPa; shear strength parallel to the grain, 11.99 MPa; MOR, 237.13 MPa; and MOE, 18.32 GPa. Comprehensively, a matured 3.5-year-old Bambusa rigida culm was recommended as the optimal logging age.