Experiments with rings to determine the anisotropic elastic constants of bamboo

Different species of bamboo are extensively used to build houses and temporary structures in developing countries. Few studies have been carried out to establish the elastic constants along the transverse axes which are the weakest directions, making them prone to failure. This is mainly due to the difficulty to cut specimens long enough to accomplish correct circumferential or radial uniaxial tests. A simple test protocol is proposed in this study to determine the radial-circumferential Poisson’s ratio, the circumferential Young’s modulus and the circumferential-axial shear modulus of bamboo using ring specimens. The proposed protocol was used to determine the elastic properties of Guadua angustifolia, which is a species frequently used in structural applications in South America. The radial-circumferential Poisson’s ratios were equal to 0.43, 0.14 and 0.12 for the bottom, middle and top portions of the culm, respectively; the circumferential Young’s modulus was equal to 398 MPa; and the circumferential-axial shear modulus was equal to 581 MPa. These values are within the range reported for different species of bamboo and structural timber. These values could be used to accomplish reliable finite element analyses of joints of bamboo structures. The proposed protocol may be used to determine the anisotropic elastic constants of other species of bamboo.