Mechanical behaviors of porous bionic structure of lotus stem.

• The design of the bionic structure is inspired by the lotus stem. • Distribution of porous layer can improve energy absorption. • Mechanism of mechanical property enhancement of bionic structure revealed. • Compared to reference structures, the bionic structure has significant advantages. • The bionic lotus stem structure has advantages over the five bionic structures proposed in recent years. Lotuses could survive in heavy storms while long and slender lotus stems have porous structure. 12 or 13-wells cross section structure and its distribution along lotus stems were identified by sampling random lotuses from nature. 4 bionic 12-wells structured bars and 1 bionic 13-wells structured bar were fabricated by 3D printing technology with toughness resin. 1 hollow circular tube and 1 hollow square tube were prepared for reference. All the bionic bars and tubes were subjected to three-point bending experiments and transverse loading experiments to investigate mechanical properties referred to the effects of cross section structures and their axial gradient distribution. The results of the transverse loading experiments showed that the peak crushing force (PCF) of the 13-wells original structure (Os-13w) was reduced by about 82.46 % and the crushing force efficiency (CFE) was increased by about 300.00 % compared with the reference square tube. The results of three-point bending experiments showed that the specific energy absorption (SEA) and CFE of the 12-wells original structure (Os-13w) increased by about 90.71 % and 173.33 %, respectively, and the PCF decreased by about 29.28 % compared with the reference circular tube. Simulation of the experiments explained why the bionic 12-wells structured bar had better mechanical performance than the referenced tubes. In addition, comparisons are made with some novel bionic structures of recent years. [ABSTRACT FROM AUTHOR]