Experimental investigation of mixed-mode I/II fracture behavior of parallel strand bamboo

The past decade has seen the rapid development of engineered bamboo composites in the civil engineering field. They have excellent mechanical properties but are susceptible to cracks, which may affect the structural performance and reduce the load-bearing capacity of the composites. Therefore, it is more reasonable to consider the fracture behavior in structural design. For this purpose, this study investigated the fracture behavior of parallel strand bamboo, a kind of engineered bamboo composite using mixed-mode bending tests. The enhancement of fracture process zone (FPZ) on the toughness was confirmed. The additional crack length induced by the presence of FPZ was evaluated, which was 14.65 mm for mode I fracture and 21.12 mm for mode II fracture, respectively. The elliptical fracture criterion GI/GIc+GII/GIIc2.23=1 applied to the initiation fracture toughness envelope, while the linear fracture criterion GI/GIR+GII/GIIR=1 was more applicable to describe propagation fracture toughness envelope. The proposed fracture failure-based criterion will contribute to the application confidence of engineered bamboo composite in the civil engineering field.