Elongation at break

The capacity of a material to undergo significant permanent deformation before fracture, as displayed by most metals and many thermoplastics. Ductile behaviour gives visible warning of overload and allows local stresses to redistribute.

The maximum tensile stress a material can withstand before failure, determined by pulling a specimen to rupture in a tensile test. It is one of the most widely quoted mechanical properties on datasheets for metals, plastics, laminates and membranes.

The deformation of a material in response to stress, expressed as change in length divided by original length. Strain is dimensionless, often quoted as a percentage, and may be elastic (recoverable) or plastic (permanent).

Material behaviour that combines viscous flow with elastic response, so that stiffness depends on time, loading rate and temperature. Polymers are viscoelastic, which gives rise to creep, stress relaxation and damping, and is characterised by dynamic mechanical analysis.