The effect of cracks on mechanical properties of round bamboo

Abstract Cracks are inevitable defects in engineering applications of round bamboo. However, existing research on the effects of cracks on the mechanical properties remains insufficient. In this study, systematic mechanical tests were conducted on crack-free (B1) and cracked (B2) round bamboo specimens, including compressive strength parallel to grain, shear strength parallel to grain, radial stiffness, flexural properties, and impact toughness. Combined with the loading deformation characteristics and energy absorption mechanism, the load-displacement curves of specimens under different loading conditions were analyzed. The results indicate that cracks exert a significant adverse effect on the radial stiffness and flexural performance of round bamboo. Specifically, the radial stiffness of cracked specimens decreases by more than 50 %, while their flexural strength and elastic modulus are reduced by approximately 31 % and 46 %, respectively. Compared with B1, B2 exhibit a prominent decline in impact toughness, whereas their parallel-to-grain compressive strength decreases only slightly. Notably, the parallel-to-grain shear strength of B2 increases by roughly 10 % relative to B1. Additionally, the energy absorption of B2 is improved under compressive and shear loading, yet reduced under flexural loading. Overall, cracks can enhance the shear resistance of round bamboo but significantly degrade its mechanical performance under flexural and impact loading conditions.