Bending along an axis for strength? I read about this law / property a couple of months back, but I've forgotten what it's name was and I can't seem to find it by Googling. I was hoping someone could give me the name for this property. If I recall correctly, it was named after same famous mathematician like Gauss or something...
More detail:
This site was basically describing how you can make a long piece of metal, paper, etc. stronger by bending it along its long axis. This way, it is less likely to collapse along its length when upright. An example of this property was grass blades, which are able to stay upright due to the fold / bend along their long axis.
If someone knows the exact name of this property, please do tell me!!
 A: What you are looking for is the famous Theorema Egregium by Gauss, which asserts that the Gaussian curvature of a surface is invariant under local isometry. At the same time, the Gaussian curvature of a surface is the product of the principal curvatures. 
Regarding a slight bend along the middle as a local isometry (of course, this conceptualization breaks down when one really bends the object too far, e.g. to the point of permanently deforming it), this physically implies that the leave of grass (or slice of pizza, which is my personal favorite as far as applications go---yum!) will resist bending along the axis orthogonal to the one you're bending it along.
I think it's also important to note that this has been discussed several times over at math.SE
A: Of course, I cannot be sure what you read, so, for what it's worth, Euler's buckling theory (http://en.wikipedia.org/wiki/Buckling#Columns )can also be relevant. It determines the maximum axial load a column can withstand without losing stability. I guess Euler derived the theory for a round column, but there should be formulas for an arbitrary shape of the column as well, and I guess the critical load should depend on the components of the moment of inertia. When you bend a strip along its axis, you increase the least component of the moment of inertia.
