<p>I am currently printing PLA infused with 80% copper powder. So far I mainly used it because it looks and feels really nice and post-processing is almost limitless, however recently I have thought that metal-like filaments might actually be a good idea for gears (in case I don't want to use polycarbonate or carbon fiber PLA).</p>
<p>I have been researching about the material properties of copper-infused PLA and found a few studies about the &quot;strength&quot;, however, those seem to have exclusively focussed on how much weight can be suspended on a hook where it showed pretty good results. The only other info I found was an unsourced &quot;it is more brittle&quot;, however the objects I printed so far do not feel more brittle.</p>
<p>Does anyone have any experience with spur gears printed from copper-infused PLA? Are there any advantages over regular PLA? Any downsides (I could imagine higher abrasiveness is not really helpful)?</p>

At a guess, copper really isn't that strong so you're likely to see minimal improvements, if any.
The PLA carrier plastic is still PLA, with a low melting point.
The copper won't "fuse" with the PLA, it will still be flakes of metal embedded in a tiny pocket inside of a plastic structure.
However this is all speculation, and your best option for an answer is to print some gears and methodically test them against plain PLA, and perhaps a metal gear if you can.  Try and use identical setups/bearings/pressures and times.
Perhaps a high torque and a high-speed test, in both lubricated and unlubed, for PLA, copper-PLA, and a straight metal gear? That would be 12 tests in all and clear out all questions.