Crash-tests and numerical simulations are vital sources of information for designing car safety elements. The aim of this study is the design of a crash-box for a Formula SAE car and the investigation, through a numerical approach, of its dynamic behaviour in frontal impact conditions. The impact attenuator is obtained by the combination of honeycomb sandwich panels and aluminium sheets. Firstly experimental tests and numerical analysis on honeycomb structures were carried out in order to better understand their behaviour and model them properly. Afterwards a global 3D model was built and discretized with finite element method (FEM) in the Ansys code, while the simulation of the crash itself was done by means of the Ls-Dyna code. The crash-box has been optimized regarding several parameters so that the performances required by Formula SAE rules are achieved with minimal structural weight. The obtained results show that the impact attenuator by itself is able to absorb the total kinetic energy with dynamic buckling and plastic deformation of its structure with an average deceleration limited under a 20g value.