A notch  is actually a deliberately induced v shape or circular shape  defect in a planer  surface. It is that part of the surface where the stress is concentrated.  Surface Notches are increasingly being used in fracture mechanics and for material characterization.  Notches are usually used in the impact testing of materials to find the origin of the crack. Surface notches are used to achieve standardized characteristics of fracture toughness. It is based on the material and characterization, the type of notch is introduced in to a specimen. The standardization test of fracture toughness is carried out using Charpy impact method. The dimensions of the specimen and the notches are calculated according to the American standard ASTM E23. Usually v shaped notches are used for the standardization of ductile and polymeric material.