Shear band

A shear band is a lens-like region in which a large plastic shear has taken place, embedded in unsheared matrix.

Shear bands are important in the understanding of failure mechanisms of brittle polymers at low temperatures (less than 80% of the glass transition temperature). Shear bands and crazes are considered to be internal flaws inside the polymer. The tensile strength of a polymer becomes independent of the length of the fracture. In other words, the polymer fails because of the flaws and not because of the cracks induced into the system when the size of the crack is very small.