3D printed fan failure in test bed - video
Expected failure mode and YouTube Forensics
Cool video!
The failure mode I would expect from this is a blade elongating or snapping under centrifugal force, catching the edge of the housing, snapping off if it already hadn't, the debris colliding with the next fan blade causing it to snap, repeating until it's all just flying shrapnel. If the housing is strong enough you'd be left with a naked hub, broken blades, and the housing.
Youtube allows you to move forward and back one frame at a time with . and , when a video is paused. It looks like the failure is mostly as expected, except the housing wasn't strong enough to contain the failure. Single framing, It peeled at what I'd guess was the point of the initial failure around the 9:00 position and then exploded from the force of the remaining failing blades. (I can't post the screenshot and I don't know why..)
It's a very cool thing to see though; I love 3d printing. MarkForged makes a printer that can embed continuous e.g. carbon fiber or fiberglass thread in the print in selectable orientations. Those would be a great fit for the blades and hub in this application because you could reinforce them specifically against elongation.
Very gool stuff.