3. Tenacity

Toughness, or residual static resistance to crack propagation, is a very important concept, as it determines the reliability of structures.

Various tests were used to characterize this property:

• tensile tests on notched specimens, with toughness criteria based on the ratio of the stress at break R _K on a notched specimen to the yield strength R _{p 0.2} of an unnotched specimen;

• tear tests to determine the energy required to initiate a tear and the energy required to propagate the tear;

• impact tests on notched or fatigue pre-cracked bars;

• tests based on fracture mechanics are generally the most interesting, as they can be used...