A modified honeycomb for better energy absorption capacity

This research was conducted in collaboration with the Saint Louis Institute, a research and development laboratory specializing in the defense sector. The findings were presented at the LWAG 2022 (Light-Weight Armour for Defence & Security) conference in Germany. In this study, we evaluate the absorption properties of a sandwich panel whose core, composed of an aluminum honeycomb structure, features a novel cellular configuration. This work contributes to the development of sacrificial panels for armor applications.

Typically, when a panel is subjected to an ultra-fast shock (a few milliseconds) such as an explosion, we can distinguish three deformation regimes of the panel. The first phase is a linear elastic deformation over a very short time; this is the compression phase.

Once the compression peak is reached, we enter a constant stress deformation regime; this is the crushing plateau. Once this plateau is passed, the structure's thickness is greatly reduced, and the stress increases rapidly until complete compaction; this is the densification regime.

In this study we investigate the influence of several geometric parameters of the honeycomb:

• The height;
• The cell diameter;
• Wall thickness;
• The influence of gluing the hides;
• Cell configuration: Hexagonal (classic) and modified by EC3D.

The various samples were subjected to standardized mechanical tests under quasi-static conditions (ASTM C365M and ASTM D7336M). Numerical correlations using finite element analysis were performed to assess the relevance of the experimental results. Finally, tests under real explosion conditions (rapid dynamics) were conducted to evaluate differences in behavior.

The results of this study highlight the benefits of the new, modified cell configuration. With equivalent material, equivalent density (the predominant parameter), and similar manufacturing cost, the performance of our structure is superior. Consequently, this means that for equivalent mechanical properties, our structure will require less material (up to 30% less), which represents a significant advantage for many sectors.