Impact behavior of honeycombs under combined shear-compression. Part I: Experiments

This paper presents a combined shear-compression impact test for soft cellular materials designed in order to investigate their behavior under impact multiaxial loadings. A large-diameter Nylon Split Hopkinson Pressure Bar system (SHPB) with beveled ends of different angles is used to apply the desired shear-compression combinations. The data processing methods are studied and validated by virtual testing data generated with FEM simulations. A series of experiments on an aluminum honeycomb were performed at the impact velocity of about 15 m/s with the loading angles ranging from 0° (corresponding to the pure compression) to 60°. It shows a strong effect of the additional shear loading because both the initial peak and the crush strength decrease with increasing loading angles. The quasi-static shear-compression experiments were also performed using the same beveled ends on a universal INSTRON machine and a notable strength enhancement under impact loading is observed. Images captured during quasi-static and impact tests permit for the determination of the two co-existing deforming patterns under combined shear-compression and reveal the influence of the loading rate on the occurrence of these two patterns.