Effect of defects on the dynamic compressive behavior of cellular solids

In this work, we investigate the dynamic compressive response of hexagonal honeycombs with defects in the form of missing cell walls for various impact velocities. Five types of honeycombs have been considered including a defect-free structure. The influence of the defect locations on the deformation bands, the local accelerations, the contact-induced, and the deformation-induced stresses have been discussed. A new parameter, termed as the bias factor, has been introduced to account for the type of the missing cell wall defects. A hexagonal unit cell has two vertical and four inclined cell walls. For a given defect percentage, we vary the relative proportion of the missing inclined and the missing vertical walls through the bias factor. The effect of the relative proportion of defects and the location of defects on the energy absorption capacity and the plateau stresses at the impact and the support ends has been discussed. The simulations reveal that the defect location causes a significant reduction in the energy absorption capacity as compared to the relative proportion of defects. It is observed that the sensitivity of the dynamic performance of the honeycombs to the presence of the defects reduces as the impact velocity increases. We define a non-dimensional dissipation performance parameter β, to evaluate the performance of various honeycomb types. It is found that the honeycombs with defects concentrated at the support end show the highest dissipation performance for impact velocities in the range 75–150 m/s.