I can add that expanding the Alu honeycomb, and maintaining a regular hexagonal structure to the cells is not possible in the real world (at least no for me
)
I have been using the EC honeycomb in the smallest cell size, and machining it down to 3 and 5 mm in compressed form, then expanding it.
Even expanding the full 10 mm thickness Honeycomb, leaves the cells quite irregular i shape. I do not think it has any important influence in the strength of the resulting sandwich structure.
Looking at how the forces act on the Aluminium Honeycomb cells, it seems to me that a very large proportion of the forces will be compressive, acting on the "thickness axis" of the honeycomb.
Taking that into account the actual precise geometric distribution of these very straight upright "walls" of thin Aluminium alloy does not seem that important, it will average out over an area.
So the number of "walls" (density pr area) and the wall thickness is the important bit. (along with the strength of the particular alloy)
From my own "empiric" research I can tell you that a sample sandwich composite, consisting of 5 mm thick EC smallest cell Alu honeycomb, between to layers of Infused CF, (each made with 2 x 200 twill + 1 300gsm Satin) will handle a load of more than 50 kg's force on a 1 sq. cm area, without visible distortion, when the force was raised to 80 kg. on the same surface area, there was a less then 1 mm deep permanent indentation, that did not affect the stiffness of the panel- ..
In this sample, the Alu honeycomb was "glued" on to the CF sheets with a thin layer of laminating epoxy, directly on a "peel-ply" surface. I did not use the specialized Permabond honeycomb glue.
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