ESTD 1999

Sandwich

Posted: 12th October 2015

After completing a new case for my PC, it became apparent that my old desk was not up to scratch. I considered how best to craft a new one to use the space as efficiently as possible, but ended up discarding the idea of a desk completely and using Ergotron LX monitor and keyboard arms instead. This worked brilliantly, except that the plastic keyboard tray was too small, and flexed a lot. I saw this as an opportunity to increase my experience with composite materials, and made a new one using sandwich construction.

A large section of aluminium honeycomb, two small sheets of carbon fibre, and tins of epoxy.
I imagine this honeycomb is made by metallic space-bees, and the epoxy is their honey. Maybe.

In the photo above you can see the different materials I needed. The 20mm thick aluminium honeycomb forms the core, the purpose of which is merely to hold the two 1mm thick sheets of carbon fibre apart. The further apart they are, the stiffer the structure is overall. Since this was the first time I had made a sandwich panel, I had to guess at how best to go about it. I started by cutting the carbon fibre into two equal sheets, and cut a section of the aluminium honeycomb slightly larger. Then I coated one of the carbon panels in epoxy, about 0.5mm thick, placed the honeycomb on top, and then weighted it down with a heavy sheet of wood on top (making sure it was all perfectly flat). Once the epoxy had cured, I repeated the process with the second sheet of carbon. Once that was done, I trimmed the aluminium flush with the edge, then realized it was going to be too sharp to leave exposed, and so pushed the edges in a bit.

A close-up of the edge of the panel, showing how the aluminium has bonded to the carbon.
The epoxy has pulled itself into place better than I expected.

It was quite strange to pick up the panel afterwards and feel how very rigid it is, despite all the constituent materials being rather flimsy by themselves. I could have used cheaper materials for this, like glass fibre instead of carbon fibre, and expanded polystyrene instead of aluminium; I chose carbon fibre to match my case, and aluminium because I wanted the edges to be exposed so the construction of the panel is visible.

The completed panel attached to the arm, with a keyoard and mouse resting on top.
Solid!
Two monitors and a keyboard/mouse on wall-mounted arms.
The whole setup.