Ductility

The tendency of a material to fracture with little or no plastic deformation, as seen in glass and many cured thermosets. Brittle materials are sensitive to flaws, notches and impact, and fail suddenly rather than yielding.

The strain at which a specimen ruptures in a tensile test, expressed as a percentage of its original length. High values indicate a ductile or flexible material such as an elastomeric roofing membrane, while rigid laminates typically fail at low elongation.

The stress at which a material begins to deform permanently rather than elastically. Loading beyond the yield point leaves residual deformation after unloading; many brittle materials, including cured thermoset laminates, fracture without showing a distinct yield.

The ability of a material to absorb energy and deform without fracturing, combining strength with ductility. Tough materials resist impact and flaw growth, whereas strong but brittle materials can fail suddenly.