Failure analysis of typical glubam with bidirectional fibers by off-axis tension tests

摘要

Glubam is a new construction material using laminated bamboo with bidirectional fibers. In this paper, we present the failure analysis of glubam with bidirectional fibers using Hankinson formula and Tsai-Wu failure criterion. Off-axis tension tests were performed on glubam specimens with longitudinal to transverse fiber ratio of 4:1. The glubam specimens were designed to study its tensile properties in different directions to the main fiber. A revised Hankinson equation suitable for glubam are developed yielding satisfactory agreement with the test results. It is found that the interaction coefficient F_(12) in Tsai-Wu failure theory can only be established from the 15° off-axis tension test. Also, three approximation methods, Tsai-Hill, "Hoffman", and "Mises-Hencky" methods, are applied to estimate the value of interaction F_(12). Four failure envelopes of glubam have been presented and compared. By comparing with off-axis test data, the failure envelope from Tsai-Wu theory provides unconservative prediction when in-plane shear is ignored. Even when in-plane shear is considered, the failure envelope obtained from Tsai-Wu theory is still deemed unsuitable to represent the behavior of glubam. Therefore, it seems the empirical approach is currently appropriate to represent the behavior of the 4:1 glubam subjected to biaxial tensile stress state.