| Parallel Strand Bamboo（PSB）is a kind of green and sustainable structural material,which has greater mechanical properties than those of traditional wood products.The property of oriented fiber reinforcement of PSB makes it can be treat as orthogonal anisotropic material.The strength on parallel to strand direction is much higher than that of the other two directions,so the cracks in PSB usually extend along the parallel to strand direction under loading actions.The PSB components are failed in mode I or mode Ⅱ or mode mixed fracture.Therefore,studying the fracture properties of PSB and establishing the fracture-parameters-based failure criterion are the critical problems in timber structural design.In this paper,ENF（End Notched Flexure）test was employed to study the mode Ⅱ fracture properties of PSB.Extended Finite Element Method-based（XFEM-）Virtual Crack Closure Technique（VCCT）in ABAQUS software was used in numerical simulations.It was found that:（1）The mode Ⅱ crack of PSB propagates along its initial direction which shows self-similarity.The fracture process goes through two periods:FPZ（Fracture Process Zone）development and crack propagation.R-curve firstly exhibits an increasing manner due to FPZ development,and then the curve becomes approximately horizontal during crack propagation.（2）The critical energy release rate,GⅡc,was evaluated by corrected beam theory（CBT）,compliance calibration method and J-integral method separately.The results of these three methods were basically the same,which indicated that the mode Ⅱ critical energy release rate of PSB is a constant independent of the initial crack length.The reference value of GⅡc was given by 2.4N/mm.（3）The mean value of fracture toughness KⅡc is 4079k Nm-3/2,which is about two times as much as common wood products.When the thickness of specimen is more than 10mm,the fracture toughness is hardly affected by the thickness.（4）Good agreement can be observed between the result of XFEM-VCCT numerical simulations and experiments.It lays a foundation to establish a numerical method for evaluating the ultimate load carrying capacity of PSB components with mode Ⅱ cracks. |
