These tests have been on the net for a while, “a while” ranging from 3 months ago to a couple of days. We thought it would be a public service to collect them in a single post.
Note that “impact resistance” is only one type of strength. Here the material must resist both compression and shock, mostly. However, there are some ways of testing the part (even with a hammer) that can cause compression failures. Torsion is mostly not an issue with these parts. Shear comes into play especially with the printed parts, which tend to fail along print-layer lines.
And who else is thinking… hmmm. What about a polymer part with a tough internal structure, and an overmold of the rubbery stuff? If you did the overmold when the inner part was still hot-out-of-the-mold fresh, the exotherm from the overmold would probably go a long way to mechanically join the two “layers.”