Failure behavior of laminated bamboo under mixed-mode loading with varying lay-up strategies

Laminated bamboo is a promising low-carbon material, yet the failure behavior and intrinsic mechanisms of laminated bamboo in structural applications remain insufficiently understood. This study focuses on the common combined bending-shear stress state in structures and investigates the failure modes of laminated bamboo under mixed-mode loading using fracture tests. A systematic comparison of mechanical properties, characterized by fracture parameters, was conducted across different layup configurations and notch-to-depth ratios. It is found that a higher proportion of 90° plies enhances bending-shear performance, including load capacity, stiffness, energy dissipation, and resistance to brittle failure. However, a high 90° fiber ratio and the stacking of 90° plies adjacently (90₂/0/90₂) increase notch sensitivity and accelerate performance degradation in deep notch members. A moderate 90° fiber ratio and alternating 90°/0° plies (e.g., (90/0)₂/90 or (0/90)₂/0) maintain good bending-shear performance while providing more gradual degradation in deep notch members. The findings provide insights into the material design of laminated bamboo under mixed-mode loading to achieve optimized structural performance and establish the basis for integrated material-structure design.