Poly-Lactide* - Carbon Fibre composite.
*. a more accurate name for Poly Lactic Acid (a name which is completely inaccurate because it isn’t a polyacid, it’s also correctly called polylactyllactate).
It’s almost as easy to work with as Polylactide (aka PLA 
) without the carbon fibre, but a lot more rigid (2x - 2.5x), quite a bit stronger (1.5x - 2.5x) and suffers from a lot less creep (1/2 to 1/4 at the same load).