Carbon reinforced concrete

Carbon F34 (Small).JPG
Thought you guys might like this. Did a series of chairs using carbon fiber reinforced concrete- took a lot of work to get the material right, but we were able to mold these to 3/8" thick, and could probably go even thinner. The whole thing weighs about 15lbs. The wet concrete is almost like adobe, it’s super thick and fibrous, and you can press it out into sheets.

More here:

Cool! Is it an embedded sheet, or chopped?

Very cool.

How does the concrete handle impact if it were to get knocked over or someone tried leaning back too hard? Interested to know if the brittleness of the concrete can survive when that thin.

I recently sat on some steel chairs with the top and back both made of concrete slabs (much thicker, maybe 1") and I recall my wife bumping it into something and a chunk of concrete cracking off at the edge.

Mirk- it’s a mix of fiber lengths, oriented and unoriented. I think you’d have a hard time fully saturating cloth with concrete, but it might be worth trying.

Cyberdemon- it’s obviously not ductile like metal, but it’s not at all like normal concrete either. The shell rings when you knock it. I’m sure it would break if you dropped it from a height, but probably 100+ people sat in these on Friday, and they survived totally unharmed. Even when I broke the test pieces I made, the fiber still held the matrix together.

Need to do some more systematic material testing now that I have some time, but the material looks really promising.

Scott, really nice chair!

How are the legs attached to the concrete composite? Is the center spindle array the 3D printed part or steel?

Thanks Shaw. All the black parts under there are 3D printed. The loads on that center part are actually pretty modest. The legs press fit into those connectors, which screw into threaded inserts embedded in the concrete. That way the legs are all simple straight cuts, and all the same length. Doing it that way was accidental, but it worked out really well.