Quasi-static axial crushing behaviour and energy absorption of novel metal rope crochet-sintered mesh tubes

This paper presents a novel reinforcement structure for composite tubes, i.e. crochet-sintered mesh tube (CSMT), for energy absorption applications. The CSMTs are fabricated by crocheting, followed by swelling and vacuum solid-phase sintering of super-fine soft 304 stainless steel wire rope twisted with 49 steel wires. This study focuses on their quasi-static crushing response and energy absorption, and investigates the influence of tube diameter and length on these characteristics. Unlike the dense structure of thin-walled metal tubes used at present, the CSMTs have a special porous structure characterised by inter-crocheting and multiple inter-locking rope skeletons and metallurgical bonds. The crushing deformation exhibits progressive folding with collapse of the mesh pores and densification, without fracture under large plastic deformation, and with rope skeleton stretching, bending, twisting and warping. The diameter and length of the CSMTs have a significant effect on the crushing mode and stability. With the same length, the larger the diameter, the better is the stability; the larger the ESR (effective stroke ratio), the higher are the SEA (specific energy absorption) and CFE (crushing force efficiency). With the same diameter, the greater the length, the weaker is the stability; the smaller the ESR, the lower are the SEA and CFE. The CSMT3 with 40 mm length and 35 mm diameter shows the best deformation stability, an ESR of 0.59, and an SEA of 1114.7 J/kg. The CSMT5 with 65 mm length and 35 mm diameter presents the lowest ESR (0.44) and SEA (592.3 J/kg). The CFE values of all the CSMTs are very high and lie in the range of 0.7-1.0. There is no significant initial impact effect. The CSMTs' lightweight, porous, and continuous wire structure, their long and stable plastic platform, and their collapsing deformation and high crushing force efficiency make them suitable for applications related to energy absorption components. The CSMTs may be used as a new reinforcement structure in composite tubes, and play an important role in the development of the novel structure of thin-walled metal tubes for energy absorbing components.