Uniaxial constitutive models for wood under cyclic compression loads with varying loading orientations

A desirable objective is to develop a unified constitutive model for wood that can effectively capture its uniaxial cyclic compressive behaviors. To achieve this goal, quasi-static cyclic compression tests have been conducted to supplement the limited cyclic experimental data available. Observation of deformation within the cell structure led to the concluded that material failure resulted from the coalescence of shear or tensile microcracks and the rearrangement of cell structures in regions under compressive stress. Based on the experimental results, a secant stiffness degradation-based and an empirical-based unified constitutive model for wood were proposed. Comparison between the predicted and experimental results indicated that the two proposed models could accurately capture the nonlinear characteristics of wood.