The ultimate tensile strength, or UTS, of a sandwich is discovered through a complex mathematical formula.
When testing some metals, indentation hardness correlates linearly with tensile strength
 The elastic behavior of materials often extends into a non-linear region, represented in figure 1 by point 2 (the "yield point"), up to which deformations are completely recoverable upon removal of the load; that is, a specimen loaded elastically in tension will elongate, but will return to its original shape and size when unloaded

