Comparison of energy absorption in negative stiffness honeycombs made of high-performance Polyamide 11 and 12

Abstract

Negative stiffness honeycombs are energy absorbers that absorb energy by transitioning from one buckling mode to another, and their snap-through behaviour in cells. They have a fundamental property as an energy absorber; in this type of absorber, negative stiffness causes reversibility after impact. In this study, the effect of negative stiffness honeycomb material in increasing energy absorption is investigated experimentally and numerically. Quasi-static tests are performed on negative stiffness honeycombs made of polyamide 11 (PA11) and polyamide 12 (PA12). Then, the finite element (FE) model of the structure is simulated under quasi-static compression. The FE model requires the nonlinear elastic and viscoelastic properties of the materials used to make the honeycombs. For this purpose, tensile and stress relaxation tests are performed. The Prony series coefficients for polyamide materials 11 and 12 are extracted and used in the FE model. Next, the energy absorption performance of negative stiffness honeycombs of PA11 and PA12 is compared experimentally and numerically. The comparison shows that the energy absorption per unit mass (SEA) for a negative stiffness honeycomb made of PA11 is 1.7 times higher in the experimental data and 1.62 times higher in the FE result than negative stiffness honeycomb made of PA12. Other fundamental parameters of energy absorption also confirm the higher efficiency of negative stiffness honeycombs made of PA11. This study provides a unique contribution by integrating experimentally determined nonlinear viscoelastic properties into the FE model and offering a comparison of energy absorption performance between PA11 and PA12 in negative stiffness honeycombs.