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

Abstract

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 F12 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 F12. 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.