Perpendicular To Grain Fracture Of Curved Glulam Beams-experiment And Numerical Modelling

In glulam small laminations are glued together to form larger members, thusoptimizing wood properties and maximizing wood utilization. Besides, curvedglulam beams have beautiful shape. They have been widely used in woodstructures. There is significant difference in stress distribution between curved andstraight glulam beams under load. Stress perpendicular to grain is induced in acurved glulam beam because of the effect of curvature. Since wood is very weak intension perpendicular to grain, the stress can cause a curved glulam beam tofracture and fail during bending. The material properties of small clear specimensand fracturing perpendicular to grain of curved glulam beams were investigated inthis study, both experimentally and numerically. Then the XFEM was employed toanalyze the failure mode and crack propagation of curved glulam beams.Shear strength parallel to grain, tensile strength perpendicular to grain,compressive strength parallel to grain and flexural strength of Northeastern larchwere tested with small clear specimens sampled from the curved glulam beams.Also, the12elastic constants like moduli of elasticity, shear moduli and Poisson’sratios were obtained. Through fracture experiments, the fracture toughness ofmode-Ⅰand mode-Ⅱof northeastern larch was measured, and the relationshipbetween thickness of specimen and fracture toughness discussed.Based on XFEM and using ABAQUS, the tests for fracture toughness ofmode-Ⅰand mode-Ⅱand the crack initiation and propagation were simulated. Thesimulated failure mode and load-deformation curves agreed well with the testresults, proving the validity of XFEM simulation.Testing of the three curved glulam beams under short-term loading wereconducted, the fracturing mechanism of curved glulam beams under tensingperpendicular to grain was explained. Finally, the complete process of crackpropagation and failure of the curved glulam beams were simulated by means ofXFEM.