|MadSci Network: Physics|
I am not familiar with the term, but I think I know what you are referring to. It is sometimes called fracture toughness.
The modulus is found by pulling a tensile bar---a bar thinned in the middle area, but smooth. The bar would break much differently if it had a notch. This notch is the beginning of a fracture, and pulling this bar tells how much force a material can withstand once a crack is started.
BTW, it is possible to make a cracked material stronger by drilling a smooth hole at the tip of the crack. The force is spread around about 60% of the circle, instead of concentrated at the tip of the crack. Still, it is unsettling to see a series of holes, say on the wing of an airplane!
Try the links in the MadSci Library for more information on Physics.