Elongation between zero stress and final rupture, as a percent of original specimen length. For example, a 1 meter specimen that stretches to 1.1 meters before breaking in two has 10% elongation at break. Also simply called elongation.
It is a measure of ductility, and the value for brittle materials can be vanishingly small — typically assumed to be zero. Values above 100% tend to be limited to elastomers and a few particuarly soft thermoplastics. All else being equal, materials with higher elongation have a better capacity to handle an excessive load without separating.
The same suite of testing standards covers a number of properties that are derived from tensile stress-strain curves. ASTM tests include C1273 and C1366 for ceramics (at ambient and elevated temperatures, respectively), D412 for elastomers, D638 for plastics, D1623 for rigid polymeric foams, D3039 for polymeric-matrix composites, D3552 for metal-matrix composites, and E8 for metals.
ISO tests include 37 for elastomers, 527 for plastics, 1926 for rigid polymeric foams, and 6892 for metals. ISO testing standards for the tensile properties of ceramics are heavily fragmented.