James Bruton is an ex-toy-designer (coming from the EE side, not the ID side) who now shares videos of his experiments and inventions on YouTube. Bruton recently got his hands on some of MatterHackers' carbon-fiber-reinforced PLA filament, and 3D-printed it alongside regular PLA to see how it measured up.
His simple test showed the CFR PLA to be roughly 20% stiffer. Then, to put the stuff to more practical use, he printed up an unusual design for a multi-part skateboard, then took it to a skatepark:
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By the bye, if you're interested in buying some carbon-fiber-reinforced PLA yourself, here's a link. (Today being Black Friday, MatterHackers' site states that they're offering discounts from today through Cyber Monday, but they don't specify what the discount is.)