Influences of defects on dynamic crushing properties of functionally graded honeycomb structures

In this work, the functionally graded honeycomb structures with defects are investigated. It is shown how the patterns and locations of defects, as well as the density gradients, can affect the in-plane dynamic crushing behavior of honeycombs. Numerical results show that due to missing vertical cell walls, the deformation process for the transverse-vertical mixing defects is more complicated than that for pure vertical defects. For the honeycombs with negative density gradient, the I-shape deformation band is dominant during the dynamic crushing. However, the honeycombs with positive density gradient are crushed to densification with the combination of the first and second deformation bands. It is revealed that the ability of energy absorption could be improved by introducing the functional graded property. Moreover, under a high impact velocity, the gradient displays a high sensitivity on the energy-absorption capability of the honeycomb structures. At the early stage of crushing, the honeycomb structures with the positive density gradient behave the stronger capacity on energy absorption than those with the negative one. The energy-absorption curves for systems with positive and negative densities are symmetric about the homogeneous structures. As the compression proceeds, for the honeycombs with positive and negative density gradients, the trends of energy-absorptive abilities go into reverse.