> A brick heavy enough to fracture an iron pipe will crush a copper pipe of
> equal dimensions.

I think I was wrong in using iron for the stiff pipe. It's ductile just like copper, and if you had a thin-wall iron pipe it would behave the same. The heavy iron pipe we're envisioning is built for a different task than the copper one. Let's say PVC pipe vs. copper pipe approximately the same size, designed for the same task, as in for home plumbing. Drop a brick on the copper pipe and it dents. Drop a brick on the plastic pipe and it cracks. Which has failed? At least the copper one doesn't leak.

> Vibrate both pipes together, and the copper pipe will fail first.

Cyclic loading would be a whole 'nother analysis, different from impact loading.

> Uniformly load both pipes together, and the copper pipe will deflect more,
> and be the first to yield.

Just because a material yeilds first does not mean that it fails first. The yield point is just the point where the material goes from elastic to plastic behavior, and some materials can take on quite a load beyond that point before failure occurs. Have you ever witnessed a tensile test? A copper strip will stretch quite a bit before it snaps. A PVC one will only stretch a little before it snaps.

> As I said, do not make the mistake of concluding that stiffer cannot mean
> stronger.

I'm not saying stiffer cannot mean stronger, I'm saying that stiffer is not necessarily stronger, and that stronger can mean weaker. But we would have to set up a lot of ground rules as to what the materials are, what the application is, what the failure mode is, etc., before we can make judgements.

> Irrelivant. It was an accurate demonstration of the falicy of the argument
> that stronger is inherently opposite of stiffer.