Crashworthiness of circular fiber reinforced plastic tubes filled with composite skeletons/aluminum foam under drop-weight impact loading

Carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic (GFRP) have shown great promise in the design of light-weight thin-walled energy absorbers. Herein, circular CFRP/GFRP hybrid tubes and tubes, reinforced with internal composite skeletons (XS and OS), were fabricated to further enhance the energy absorption capacities. The crashworthiness and failure pattern of reinforced structures were compared with the hollow and aluminum foam-filled composite tubes. Moreover, low-velocity drop-weight impact tests were carried out to investigate the effect of hybridization design and filler types on the energy dissipation mechanism under axial compression. The experimental results revealed that the hollow composite tubes collapsed in progressive and the impact energy was absorbed by the generation of cracks, fiber fracture and friction. Also, the GFRP tubes exhibited better crashworthiness than CFRP tubes under low velocity impact, which was different from the quasi-static compression conditions. In contrast to hollow counterparts, the mean crushing force (MCF) of foam-filled tubes was improved by approximately 40%, whereas the specific energy absorption (SEA) was reduced by 30% due to the low weight efficiency of the aluminum foam. The filling of XS-skeleton divided the tube into four cells and improved the MCF by more than 10%. However, it reduced the SEA by around 8% due to unstable and inefficient deformation of XS-skeleton during crushing. By contrast, the OS-skeleton divided the hollow tube into more cells and collapsed progressively, resulting in superior energy absorption characteristics. Herein, the OS-filled GFRP tube was found to be the most crashworthy structure that improved the crushing force efficiency (CFE) and SEA by 50% and 7%, respectively.