Physical and mechanical properties of wood from sweet bamboo culms (Dendrocalamus asper Backer)

This research investigates the physical and mechanical properties of wood from Sweet-Bamboo culms (Dendrocalamus asper Backer.). The physical properties, i.e., moisture content, specific gravity, and shrinkage, and the mechanical properties, i.e., static bending, tension parallel to grain, compression parallel to grain, and shear parallel to grain were studied. The effect of moisture content and culm height on the above properties was likewise examined. Four Sweet-Bamboo culms were randomly collected from Prachinburi Province. Each culm was approximately 3 years old. Methods for preparing the test specimens were modified to be suitable for bamboo culms from the procedure in ISO Standard. The specimens were crosscut at every two-meter intervals along the culm starting from ground level for a total of seven locations. At each location, the specimens were removed from the part without bark and inner skin. They were then tested according to the ISO Standard at two moisture-content conditions, i.e., green and air-dried. The data gathered were analyzed using the analysis of variance concepts and compared by the Duncan's New Multiple Range Test. The results indicated that the wood of Sweet-Bamboo culms has moisture content at natural green condition of 46 percent and specific gravity at air-dried condition of 0.77 on the average. The mean of shrinkage at air-dried condition in tangential, radial and longitudinal direction are 2.53, 1.35 and 0.21 percent, respectively. The mean of modulus of rupture of 135 MPa, modulus of elasticity of 13,115 MPa, and toughness of 676 kPa were obtained. The tensile, compressive and shear stresses parallel to grian were found to be 314, 72 and 14 MPa, respectively. In addition, analysis of variance showed that tensile stress parallel to grain and toughness of bamboo wood significantly increased with culm height. For static bending, compressive and shear stresses parallel to grain of bamboo wood, significant difference along the culm height was not detected. The mechanical properties in air-dried condition were slightly higher than those in green condition. Moreover, the results revealed that the top part of a bamboo culm is stronger than those of Nibong (Oncosperma tigillarium Ridl.) and Palmyrah (Borassus flabellifer Linn.) stems which are of the same monocotyledonous species. It was concluded that the Sweet-Bamboo wood had low natural moisture content, medium specific gravity, and slightly low shrinkage comparing to other species. However, it had very high mechanical properties, especially the resistance for tension parallel to grain which was higher than all other wood species. All mechanical properties were also uniform along the culm. This indicated that the whole culm of Sweet Bamboo could be utilized without rejecting the top portion like in other wood species.