Dynamic crushing failure and energy absorption of natural bamboo-culms under axial low-velocity impact

The axial crushing behavior of natural bamboo culms with various growth ages under quasi-static and low-velocity impact was experimentally investigated in this study. First, the macro- and micro- structural features of bamboo culms were observed, and the tensile mechanical properties of bamboo materials were measured. And then the typical crushing responses and deformation/failure patterns of dynamically-loaded bamboo culms were presented, compared with those under quasi-static load. Whereafter, the strain field distribution and energy absorption characteristics of bamboo culms were analyzed, and the crashworthiness of tested bamboo culms under impact load was evaluated. Finally, the energy absorption capacity of bamboo culms was compared with typical metallic circular tubes (made of Q235 steel and AA6061-T6 aluminum alloy) and other widely-used engineering materials/structures. The results indicate that the brittle fracture is the dominant failure mode of bamboo culms, which includes the splitting mode for internodal specimens and the bulging mode for nodal specimens. The nodal bamboo culms have a superior energy absorption capacity and crashworthiness compared to internodal bamboo culms, attributed to the dense distribution of vascular bundles and high anti-split strength of bamboo nodes. The energy absorption capacity of 1-year-old nodal bamboo culms is better than that of aluminum or steel tubes, and the corresponding SEA value of nodal bamboo culms has reached 11.8 J/g, while it is 10.65 J/g of the aluminum tube and 6.65 J/g of the steel tube, respectively.