Design Decisions
Through modeling and analysis we came to the following decisions for cell shape and manufacturing processes. The details of the analysis and selection are outlined below.Cell Shapes
In identifying the most efficient core, we first looked at cell structures with their respective stress distributions under various loading conditions. Compression, shear and torsion were our main concerns, because these loading conditions would reveal the strengths and weaknesses of the cell designs. However, through our analysis compression revealed the most pertinent information because it is the most common loading situation due to face sheet attachment.The second of our design criteria was packing efficiency. Small volumes are hard to fill with insulation material. Packing efficiency is a property of adjacent cells within a square. Any excess volume identified through cell shape packing is undesirable as shown below.
The cell shapes that we recomended to SMARF were the rounded hexagonal because of its packing efficiency and stress distribution. We also recomended the single reinforced rounded hexagonal shape as well because it provides a quick and easy way to significantly increase the strength of the sheet.
Manufacturing Methods
Manufacturing methods exist for honeycomb panels for ductile materials, but this type of manufacturing method is not applicable for brittle materials. The available methods are inadequate for the purposes of this project. After conferring with SMARF we moved ahead with two manufacturing methods, a layering method and a molding method.Layering method
This method is a streamlined version of the current method being implemented by SMARF (Photos of this method can be found in Appendix D). Material is poured on preformed sheets, hardened in-place, and then stacked to form a panel. Due to the nature of our project we cannot discuss the specifics of the method. The image below shows the frame we constructed for our layering method. We tested the frame at SMARF’s facilities. Photos of this can be found here.
The manufacturing method shown below is a method that is currently utilized by many aluminum honeycomb manufacturers and has some similarities to proposed method.
Mold method
Material is poured into a mold and allowed to dry. The panel is then removed from the mold. Once again, the specifics of this process cannot be disclosed. The image below shows a prototype Computer Aided Drafting rendering of the mold.