Energy-absorbing mechanism and crashworthiness performance of thin-walled tubes diagonally filled with rib-reinforced foam blocks under axial crushing

Thin-walled structures are widely used as crucial structural components for energy absorbing applications. To design lightweight thin-walled-involved composite structures with better mechanical performance remains an open issue. In this study, the X-shaped rib-reinforced foam-filled tubes were designed and tested under quasistatic axial compression. Two types of foams, i.e., the aluminum foam and the additively manufactured polylactide (PLA) foam were considered as lightweight fillers. The effects of foam block filling ratio (rib angle) and arrangement of different foam fillers on the axial crushing performance of the diagonally rib-reinforced foam block-filled tube were analyzed. Results indicated that tubes that were diagonally filled with PLA foam blocks possessed better energy absorption capacity, whereas the higher mean crushing strength was achieved by diagonally filling with two aluminum blocks. It also revealed that tubes filled with different foam blocks did not always show advantages over those filled with the same foams. Moreover, the diagonally aluminum foam blocks filled tubes with a large rib angle could induce the global buckling, whereas that with the rib angle of 120 degrees exhibited better mechanical properties in load consistency and specific energy absorption capacity. Numerical simulations were conducted to reveal the energy absorption enhancement mechanism of the tubes filled with varying combinations of the reinforced fillers. Results indicated that the interaction between the foam blocks and the reinforced rib contributed most to the increased energy absorption. Further, an analytical model for evaluating the crushing strength of the developed structure was proposed. The theoretical predictions are in good agreement with the experimental results. The idea of tailoring the fillers arrangement and assembling pattern would promote the development of optimal energy-absorbing thin-walled involved composite structures.