[CNCKitchen], like many others, is looking to make strong 3D prints. Using a high tech PLA bio copolyester compound, he printed a bunch of hooks in two different orientations. He used several different types of glue including epoxy and superglue. You can see the video of his results, below.
In addition to the glue, he used epoxy and bulk carbon fiber, again, in two different orientations. After several days of curing, he was ready to test.
Untreated parts managed about 53 kg or not quite 25 kg, depending on their orientation. The thin superglue part got up to 58 kg. Viscous superglue didn’t do much better than the thin glue. Since the epoxy cracked before the plastic, there wasn’t much difference and in one orientation it was even weaker than the reference part.
You can get carbon fiber enhanced PLA, but you get short fibers. [Stefan] glued long pieces of carbon fiber exactly where he wanted them using epoxy. This method did provide some benefits.
Unfortunately, at least with the plastic used, none of the results were amazing. The carbon fiber technique bears more investigation, but even so, the results were — so far — not astonishing. However, this is a great application of the scientific method. Intuitively, adding some glue ought to make parts better, right? Testing like this shows that it doesn’t in this particular circumstance.
By the same token, you’d think getting superglue in your eyes would be a life-changing event. Apparently, not so much, although we still don’t recommend it. If you want to know more about glue — maybe more than you want to know — we deconstructed glue awhile ago.