Numerical and experimental study of viscoelastic properties and energy absorption of functionally graded negative stiffness honeycomb made of Polyamide 12

This study investigated the effect of a functionally graded negative stiffness (FGNS) honeycomb made from polyamide 12 (PA12) on increasing energy absorption. In addition, the viscoelastic model of PA12 was implemented in the finite element (FE) model to demonstrate the recoverability of these structures. First, a quasi-static compression test was performed on constant thickness negative stiffness (CTNS) honeycomb and FGNS honeycomb. Then, these two structures' FE models were simulated. The stress relaxation test was utilised to derive Prony series coefficients for PA12 viscoelastic properties. The results of viscoelastic simulation for CTNS and FGNS honeycombs were then compared with experimental results. The comparison demonstrated a good agreement in both the loading and unloading stages. Furthermore, the critical parameters for evaluating the structural energy absorption of the FGNS honeycomb and the conventional ones were used in this study. According to the results, the FGNS honeycomb outperformed the CTNS experimentally and numerically.