Crushing behaviours and energy absorption characteristics of square antiprisms structure against flatwise crushing

• A thin-walled energy absorber is proposed and outperforms the conventional tubes by providing higher plateau stress and specific energy absorption capacity. • Because of its particular geometric structures, the problem of high initial crushing peak force in axial collapse of thin-walled structures has been solved. • The deformation mode is described with experiment and numerical simulation in detail, and the mechanism why there is a lower peak force is revealed. In this study, a type of thin-walled energy absorber named square antiprisms (SAP) is proposed, which can be used as a core of cladding “sandwich” panel design for improving crashworthiness. Three types of SAP structure, i.e. open SAP, half-enclosed SAP and all-enclosed SAP are studied. The purpose of this unique geometric structure is to increase the energy absorption capacity of the thin-walled structure while maintaining a uniform collapsing resistance under various crush loading rates as compared with other existing conventional thin-walled structures (i.e. cylindrical tube, square tube), and folded square dome shaped structure proposed recently [50] . A unit cell of standard Miura-origami folding core is numerically simulated and calibrated with the experimental results. Good agreement on the peak and average crushing force between numerical results and experimental data is achieved. The calibrated numerical model is then used to simulate the structural response of thin-walled energy-absorbing structures under various loading rates. The collapse modes and the energy absorption capacity including average and peak stress, energy absorption, crush force efficiency and densification strain are compared among these structures. The proposed open SAP structure shows good energy absorption characteristics under quasi-static loading and dynamic loading by yielding low initial peak stress, big crush force efficiency, large densification strain and more uniform collapsing. In addition, unlike the existing typical axial crashed thin-walled energy absorber, the SAP structure show shows insensitivity to the medium and low crushing speed (no more than 63 km/s) in terms of initial peak stress and uniformity ratio. Compared with the existing typical thin-walled structures, the proposed SAP structure demonstrates a superior performance to most of the axially loaded thin-walled components, indicating a potential application as an energy absorber.