Scratching behaviour of polymer films using blunt spherical styli

There are four different kinds of scratch morphologies developed when a blunt spherical stylus is in contact with the surface of a polymer multilayer system in relative motion. Qualitatively, a relationship between scratch morphologies and mechanisms can be established. The main deformation mechanisms are surface shear yielding, surface cracking, subsurface yielding (indentation), and interfacial delamination. Tangential forces during scratching using a blunt spherical stylus are largely due to the friction between materials and the stylus. In that sense, lubricants can improve the material scratch performance by reducing the friction force at a given normal load. Many variables, such as scratching speed, environments, and the sizes of styli, can affect polymer scratching performances to a large degree.