Assessment of the ballistic response of honeycomb sandwich structures subjected to offset and normal impact

In the present study, experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores. The high velocity impact tests were carried out using a compressed air gun. A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm). The deformation, failure mode and energy dissipation characteristics were obtained for both kinds of loading. Moreover, the explicit solver was run in Abaqus to create the finite element model. The numerically obtained test results were compared with the experimental to check the accuracy of the modelling. The numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in Abaqus. Furthermore, the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation,deformation and failure mode was examined. The result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact loading. Sandwich panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset distance. Also,increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy absorption. However, inscribe circle diameter had a negative influence on the ballistic resistance. Also, the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation directions. The energy dissipation in plastic work was highest for circumferential direction, regardless of impact condition followed by tangential, radial and axial directions.