Anisotropic mechanical properties and composite model of parallel bamboo strand lumbers

Abstract

To investigate the anisotropic mechanical behaviors of the parallel bamboo strand lumbers (PBSLs), seven kinds of PBSL specimens with fiber orientation changing from 0° to 9° at an interval of 15° were tested in tension, compression and shearing, respectively. It is found that the failure of the PBSL is essentially along the bamboo fibers. It is a typical interfacial failure as the cracks develop along the fiber direction induced by shearing or splitting. Fiber fracture is mainly observed in tension along the fiber direction. A nonlinear constitutive model is proposed on the basis of analyzing the stress-strain curves of PBSLs at different fiber angles. Classical strength failure criteria for unidirectional composite materials are contrasted based on failure analysis and anisotropic strength prediction. It is found that both the Norris criterion and the Hill-Tsai theory can consistently predict the strength anisotropy of the PBSL.