Micromechanical Characterization of Scratch and Mar Behavior of Automotive Topcoats

The automobile industry and its customers demand durable glossy appearance of automotive topcoats. A micro-scratch technique has been developed to quantitatively characterize scratch and mar behavior. With the micro-scratch instrument normal force, tangential force, penetration depth and permanent damage can be controlled or measured precisely as function of time or position during scratch experiments. These physical quantities allow us to evaluate scratch and mar resistance based on damage mechanisms. The micro-scratch instrument is stable enough to produce centimeters long scratches of various types and sizes so that the relationship between scratch morphology and appearance can be investigated. Results from statistical surveys on well-defined scratches suggest that a scratch with fracture is the most visible type of damage.