Searching superior crashworthiness performance by constructing variable thickness honeycombs with biomimetic cells

Honeycomb materials are often used as the inner core of composite sandwich structures and are widely applied in impact resistance equipment design. Inspired by biomimetic materials, a series of potential variable thickness honeycombs with enhanced biomimetic cells (VTHEBs) are proposed and analyzed in this study, including the variable thickness honeycomb with bionic circular cells (VTHBC), the variable thickness honeycomb with bionic triangular cells (VTHBT), and the variable thickness honeycomb with bionic hexagonal cells (VTHBH). The crashworthiness properties of VTHEBs are studied by experimental, numerical, and theoretical analysis. The experimental results reveal the mechanical responses of VTHEBs under out-of-plane loading and validate the numerical models established by LS-DYNA. It is also observed that VTHBC shows better crashworthiness than VTHBT and VTHBH. Compared with the corresponding regular variable thickness honeycomb (RVTH), the variable thickness honeycomb with enhanced bionic cells has superior material distribution, which helps to improve the crushing force level and energy absorption potential. Besides, the numerical models are used to explore the effects of different design parameters (thickness deviation coefficient, cell size coefficient) on the mechanical performances of VTHEBs. Finally, the theoretical models of crushing forces are derived to predict the crushing performances of VTHEBs. The results show that the theoretical models can approximate the overall trend of experimental and numerical results with acceptable accuracy. This study provides an interesting design concept for superior crashworthy structures, which can be expected to be applied to impact resistance equipment in the future.