Mechanical Response of Aluminum and Nomex Honeycomb Sandwich Panels under Localized Quasi-Static Indentation

This study investigates the buckling behavior of composite honeycomb sandwich panels subjected to quasi-static indentation through a combined experimental, analytical, and numerical approach. Sandwich panels with aluminium (AHC) and Nomex (NHC) cores were tested under various indenter geometries (cylindrical, conical, truncated cone, and hemispherical) and different cell sizes (3.2 mm, 6.4 mm, and 9.6 mm). The influence of core material, cell size, and indenter geometry on critical buckling load, failure modes, and energy absorption was systematically evaluated. A theoretical model was developed to predict the threshold buckling load based on geometric and material parameters, and validated against experimental results. Finite element simulations using ABAQUS provided insight into damage evolution and agreed closely with both theoretical predictions and experimental measurements. The results show that smaller cell sizes and higher core densities improve indentation resistance and delay buckling. Indenter geometry significantly affects both the failure mode and the extent of damage. These findings contribute to a better understanding of the mechanical behavior of lightweight sandwich structures under localized loading and provide design guidelines for improving their structural performance in aerospace and transportation applications.